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so I will just go through the

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oldfashioned paper uh syllabus so the

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course is going to be taught on canvas

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so the canvas site has been published uh

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we will for for uh homeworks and things

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like that they'll be handed out and

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turned in on paper but you can download

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them from canvas as

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well um the classes are going to be here

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Mondays Wednesdays and Thursdays so on

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usual class schedules 1

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pm uh I've mentioned the textbook there

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are some other textbooks that you might

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find Handy and I've listed those in the

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course handout those are completely

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optional you don't have to buy them the

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libraries also have

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copies um the way homeworks will work in

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this

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class is that will typically be issued

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on a Monday and do the following Monday

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okay and uh for the most part you are

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allowed to collaborate and talk about

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the homework problems so you feel free

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to get together and discuss the problems

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that there it's intended that you do so

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the only constraint we have is that you

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must hand in your own solution right so

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so you can trade ideas but in the end

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the thing you write up it can't be a

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copy your neighbors it has to be your

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solution but you can base it on uh you

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know ideas you've exchanged with others

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okay for those who don't know

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anybody or or don't have access to study

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partners and may have questions first of

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all there will be office hours uh Mon's

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office hours will be Thursdays 4: to 5:

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p.m. and Fridays 4 to 5:00 P p.m. in

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10178 in building 10 okay but there are

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also a number of students students in

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the Le laboratory 1050 who have had this

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class before will be happy to answer any

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questions and a few of those students

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are listed in the uh course

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description we've also decided not to

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have exams this term or in-class exams

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rather we're going to have assessments

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which are essentially take-home mini

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quizzes uh they will generally be uh um

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they'll be generally issued weekly and

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this says they're going to be issued

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starting on March 1st I should check if

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that yeah starting on March 1st they'll

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be issued weekly they'll be issued on a

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Wednesday that will be due the next day

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Thursday and those will be submitted

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through canvas through grade

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scope

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um as for homeworks we can take late

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homeworks if you arrange it ahead of

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time and there's some compelling reason

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why they're late assessments are a

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different

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story also the collaboration policy for

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assessments is different you cannot

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collaborate or discuss the problems at

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all for assessments and and you know we

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can't prove or not prove that you're

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doing so but this is you know this is an

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exam effectively so don't discuss it

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with your neighbors and don't discuss

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anything until the solutions are out

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because there may be people who have

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made some special arrangement for

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because they're traveling or or for

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whatever reason to hand it in late okay

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so we're going to have homework and

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assessments and the goal of the

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assessments really is instead of a you

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sort of very few high stakes

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opportunities to show your abilities the

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assessments are sort of distributed in

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low stakes and focused and gives you a

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better opportunity to show you what you

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really know okay so please complete them

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entirely on your own no consultation the

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only thing you're allowed to do is ask

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the core staff clarifying questions just

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the way you might in an exam okay

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and uh as for the assessments you can

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use any of the course materials you know

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read the book whatever you want

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uh do

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not go outside and try to use the

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worldwide web and for that matter the

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use of Bibles is also prohibited I know

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that there's collections of old 6334

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materials floating around you're not

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supposed to be Consulting those okay

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this just supposed to be a measure of

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what you've learned okay okay so the

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grading will be based on three

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components homeworks are going to be

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40% these assessments will be

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50% and there's also a final project

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which is 10% and the final project

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sounds like it's only 10% but it's the

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last thing we look at when we're going

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to assign a grade to everybody and it

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really is your opportunity to put

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together knowledge that you've learned

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throughout the class into a real it's on

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paper it's not a it's not a phys phical

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converter you will construct but it's a

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paper design but it's really your

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opportunity to show us how you've

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synthesized all this knowledge to be

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able to really design Power Electronics

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and I should say just as an aside in

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this class we only have a paper design

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or or but this complements nicely the

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undergraduate Power Electronics class

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which has a lot of really nice lab

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activities and design activities there

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so even if you're a graduate student

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it's it can be a pretty good thing to

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take in terms of of uh rounding out the

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LA your lab skill set in this area

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Okay um if you have any necessary

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technical accommodations don't have

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access to uh iPads or whatever else you

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need for grade scope please let us know

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we'll try to assist uh assist with that

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okay so with that are there any

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questions about anything like associated

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with the course

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mechanics okay so let me um give you a

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sense of what this course is going to be

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about and uh this is one of my favorite

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photos is actually one that uh Nicola

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Tesla mocked up he wasn't really sitting

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next to his Tesla coil when he did this

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or he might have gotten killed um he

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kind of double exposed this but more to

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the point

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uh the quote from him is if we could

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produce electrical effects of the

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required quality this whole planet and

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the conditions of existence on it could

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be transformed and I think the sort of

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the more than a hundred years since he

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he said that or well more than 100 years

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since he said that uh have borne that

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out but it's also true that even

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today uh there's really revolutions

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happening in the way we use energy

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everything's being electrified from

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vehicles to transportation to power

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generation from renewable

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resources and um handling all that

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requires some means of processing

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controlling and converting energy and

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that's really what we're about

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processing controlling converting

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electrical

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energy if you look at what the uh itle e

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the which is sort of the governing body

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of electrical engineering says about

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Power Electronics it says this

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technology encompasses the use of

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electronic components

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the application of circuit Theory and

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design techniques and the development of

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analytical tools towards efficient

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electronic conversion control and

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conditioning of electric power and

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that's what we're really about here so

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we're going to do circuit Theory we're

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going to learn design techniques we're

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going to learn about all the components

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you need to do this we're going to learn

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about controls how do you put it all

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together to make energy conversion

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systems okay so as I mentioned the

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primary function of Power Electronics is

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to take sort of electrical energy in one

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form and convert it into some other form

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you need uh it's really a core

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technology in the electrical

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infrastructure it used to be that the AC

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grid was generators and you'd connect it

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up to things like directly things like

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Motors or lighting or whatever but

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that's pretty much changed at this point

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right lighting is LED lighting you need

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power supplies to go between the grid

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and the lighting same thing heavily

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loads computers Motors everything else

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you need energy tends to flow through

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one or even several layers of power

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conversion circuitry from the principal

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source to the final usage okay and so

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the Power Electronics first of all you

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know the efficiency of that is very

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important but also how you do it impacts

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the quality of the final system so the

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Power Electronics can really be a major

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factor impacting what you can and can't

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do and how well it works

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okay so if you showed up you know

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hundred years

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ago this is what Power Electronics would

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look like right some vacuum tubes and

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some Transformers and that kind of thing

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interestingly of course it's nothing

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like that today but with the techniques

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you're going to learn in this course you

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could actually go back and analyze this

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thing and figure out what it did right

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so some foundational ideas that we're

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going to come back to which can be 100

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years old but there's also elements that

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are extremely new okay and today you

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know this this was fancy 100 years ago

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today Power Electronics is everywhere

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from I say from mowatt to gigawatts and

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and it does actually use switch mode

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power conversion down at those power

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levels this is actually a a multi-watt

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power supply and this is literally at

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the gigawatt scale so if you if you go

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out to S the Sandy Pond terminal there

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is a power converter that takes two gws

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coming down from Canada hydro and

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converts it to AC to power homes and

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everything else around here right so and

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the techniques that we're going to learn

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in this class really span the entire

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range right so some of the details

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change and we'll learn about that but

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there's underlying principles that that

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cut across all kinds of electrical

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energy conversion systems

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okay what kind of applications well

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portable Electronics this slightly older

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an iPhone 5 and you think okay iPhones

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got radio transmitters and displays and

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other stuff in it but it turns out that

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a large fraction of the volume and board

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area is actually associated with energy

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conversion in the thing because no

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matter what you're doing you're

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processing energy to process information

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right so something like 40% in this of

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the motherboard in this example was

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associated with power

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conversion likewise you know at some

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point you're going to charge your phone

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or your or your iPad or your computer

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into the wall that's mostly Power

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Electronics too all kinds of computers

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if you're in a data center there's

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several layers of power conversion

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between the AC group GD and the final

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set of

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processors okay this is more of what it

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looks like inside your home computer

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we'll actually learn exactly about those

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kind of converters and about all the

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components that are in them if you're

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going to communicate right the

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transmitters we tend to think of this as

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analog circuits to to make RF

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transmitters but in fact Power

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Electronics are heavily embedded in any

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real communication systems to increase

278
00:11:27,958 --> 00:11:33,078
the efficiency of transmission

279
00:11:31,200 --> 00:11:35,120
all kinds of commercial applications

280
00:11:33,078 --> 00:11:38,039
whether you're you know doing LED

281
00:11:35,120 --> 00:11:39,919
lighting or this is actually from some

282
00:11:38,039 --> 00:11:42,759
water

283
00:11:39,919 --> 00:11:45,240
Purity device but of course it requires

284
00:11:42,759 --> 00:11:48,799
a power supply right

285
00:11:45,240 --> 00:11:50,278
so almost any use of energy these days

286
00:11:48,799 --> 00:11:52,838
requires a power

287
00:11:50,278 --> 00:11:54,919
supply even in your home I mentioned

288
00:11:52,839 --> 00:11:56,880
that it used to be that you'd connect

289
00:11:54,919 --> 00:11:58,120
Motors up to the grid and they'd run and

290
00:11:56,879 --> 00:11:59,958
maybe You' turn them on and off

291
00:11:58,120 --> 00:12:02,120
something like that but no longer right

292
00:11:59,958 --> 00:12:04,838
if you want high performance you need to

293
00:12:02,120 --> 00:12:07,879
be able to modulate that energy so two

294
00:12:04,839 --> 00:12:10,279
examples here this is for an air

295
00:12:07,879 --> 00:12:12,720
conditioning unit and it uses an

296
00:12:10,278 --> 00:12:15,320
inverter a DC to AC converter inside it

297
00:12:12,720 --> 00:12:17,320
to drive the motor much more quietly and

298
00:12:15,320 --> 00:12:20,560
much more modulated for higher overall

299
00:12:17,320 --> 00:12:23,000
system efficiency even your dishwasher

300
00:12:20,559 --> 00:12:25,638
these days has power converters in it

301
00:12:23,000 --> 00:12:30,559
because it's more efficient in this case

302
00:12:25,639 --> 00:12:33,079
quieter to do it that way okay IDE is

303
00:12:30,559 --> 00:12:35,919
that you might not think of as power

304
00:12:33,078 --> 00:12:39,078
converters medical applications this is

305
00:12:35,919 --> 00:12:41,838
this is actually a uh magnetic

306
00:12:39,078 --> 00:12:43,879
stimulator generates 5,000 amps pulse

307
00:12:41,839 --> 00:12:46,480
trains in a transducer coil to throw up

308
00:12:43,879 --> 00:12:47,919
magnetic fields that can trigger nerves

309
00:12:46,480 --> 00:12:49,199
this is an interesting one it's actually

310
00:12:47,919 --> 00:12:51,039
homework zero so the thing you're

311
00:12:49,198 --> 00:12:53,479
analyzing in the first homework just to

312
00:12:51,039 --> 00:12:57,480
break the rust off is actually this box

313
00:12:53,480 --> 00:12:59,680
right here okay scientific applications

314
00:12:57,480 --> 00:13:01,519
you may not be processing energy but

315
00:12:59,679 --> 00:13:03,239
even if you just need to generate

316
00:13:01,519 --> 00:13:05,839
electric High electrical fields for

317
00:13:03,240 --> 00:13:07,680
whatever reason or magnetic fields as in

318
00:13:05,839 --> 00:13:10,079
the magnetic stimulator you need energy

319
00:13:07,679 --> 00:13:12,278
conversion circuits to do it then

320
00:13:10,078 --> 00:13:14,000
there's the sort of the more maybe the

321
00:13:12,278 --> 00:13:17,039
applications you might think of

322
00:13:14,000 --> 00:13:19,759
Transportation right let say that

323
00:13:17,039 --> 00:13:21,000
electric vehicle or a hybrid vehicle

324
00:13:19,759 --> 00:13:23,319
right you

325
00:13:21,000 --> 00:13:24,600
need Power Electronics to drive the

326
00:13:23,320 --> 00:13:25,839
energy conversion and this is not a

327
00:13:24,600 --> 00:13:28,759
small thing first of all you need the

328
00:13:25,839 --> 00:13:31,959
Power Electronics to drive these things

329
00:13:28,759 --> 00:13:34,759
right secondly in fact as in one

330
00:13:31,958 --> 00:13:37,439
example they redes they

331
00:13:34,759 --> 00:13:40,879
redesigned the power converter for a

332
00:13:37,440 --> 00:13:43,440
Prius the the power train for the Prius

333
00:13:40,879 --> 00:13:45,159
the fuel economy went up by 5% just by

334
00:13:43,440 --> 00:13:48,760
redesigning the Power Electronics to be

335
00:13:45,159 --> 00:13:52,159
better so it has a huge impact on the

336
00:13:48,759 --> 00:13:56,439
overall application and of course that's

337
00:13:52,159 --> 00:13:58,759
um electric vehicles but traction right

338
00:13:56,440 --> 00:13:59,639
trains that's higher power but the same

339
00:13:58,759 --> 00:14:01,399
issue

340
00:13:59,639 --> 00:14:03,000
actually even future trains this it's a

341
00:14:01,399 --> 00:14:05,799
little hard to see behind this railing

342
00:14:03,000 --> 00:14:08,600
that's a maglev magnetically levitated

343
00:14:05,799 --> 00:14:10,319
train along the Wayside over in the back

344
00:14:08,600 --> 00:14:12,480
corner you see this big building here

345
00:14:10,320 --> 00:14:14,800
inside that big building as these racks

346
00:14:12,480 --> 00:14:16,720
of Power Electronics now you better have

347
00:14:14,799 --> 00:14:19,240
pretty reliable Power Electronics if

348
00:14:16,720 --> 00:14:20,879
your vehicle's flying along at 400 kmers

349
00:14:19,240 --> 00:14:23,799
an hour floating on you know that far

350
00:14:20,879 --> 00:14:26,039
off the ground right so not only do you

351
00:14:23,799 --> 00:14:29,639
need efficiency but you need reliability

352
00:14:26,039 --> 00:14:32,838
and precision okay even Strang

353
00:14:29,639 --> 00:14:37,079
things uh this is this is an example of

354
00:14:32,839 --> 00:14:38,639
a drone just by powered by high voltage

355
00:14:37,078 --> 00:14:41,838
right you just apply high voltage it

356
00:14:38,639 --> 00:14:43,399
breaks down the air accelerates ions and

357
00:14:41,839 --> 00:14:45,000
you can use that for propulsion that's

358
00:14:43,399 --> 00:14:47,519
the first demonstration of it but it

359
00:14:45,000 --> 00:14:49,198
actually it's very similar in some

360
00:14:47,519 --> 00:14:51,000
regards to what people use for space

361
00:14:49,198 --> 00:14:54,120
propulsion you've heard of ion engines

362
00:14:51,000 --> 00:14:57,159
right the twin ion engine TIE fighter or

363
00:14:54,120 --> 00:14:59,399
what more practically they use to uh to

364
00:14:57,159 --> 00:15:00,879
reposition satellites those require

365
00:14:59,399 --> 00:15:05,120
Power Electronics to generate high

366
00:15:00,879 --> 00:15:08,799
voltages and accelerate ions okay Power

367
00:15:05,120 --> 00:15:10,039
transmission and generation right that's

368
00:15:08,799 --> 00:15:11,479
so you're getting your energy from

369
00:15:10,039 --> 00:15:13,439
somewhere and increasingly we're getting

370
00:15:11,480 --> 00:15:16,199
it from renewable resources well

371
00:15:13,440 --> 00:15:19,680
generally the way things are trending

372
00:15:16,198 --> 00:15:21,799
you take some mechanical or solar or

373
00:15:19,679 --> 00:15:24,039
other source of energy and you

374
00:15:21,799 --> 00:15:25,838
transition it not only through a

375
00:15:24,039 --> 00:15:27,480
generator but through Power Electronics

376
00:15:25,839 --> 00:15:30,240
to get there and that's true for

377
00:15:27,480 --> 00:15:33,560
terrestrial things things like this is a

378
00:15:30,240 --> 00:15:35,318
house rooftop PV system this is a micro

379
00:15:33,559 --> 00:15:36,838
inverter

380
00:15:35,318 --> 00:15:39,919
um

381
00:15:36,839 --> 00:15:42,519
Automotive Systems or even much smaller

382
00:15:39,919 --> 00:15:45,439
things like uh

383
00:15:42,519 --> 00:15:48,278
uh Power harvesting energy harvesting

384
00:15:45,440 --> 00:15:50,759
techniques you need Power Electronics in

385
00:15:48,278 --> 00:15:53,399
it also all kinds of industrial

386
00:15:50,759 --> 00:15:56,000
applications whether you're doing uh

387
00:15:53,399 --> 00:15:58,480
plasma processing for Semiconductor

388
00:15:56,000 --> 00:16:02,120
processing or you know you want to

389
00:15:58,480 --> 00:16:04,600
refine metals like a DC Arc furnace you

390
00:16:02,120 --> 00:16:06,519
need Power Electronics there too okay so

391
00:16:04,600 --> 00:16:09,360
that's just sort of a way long way of

392
00:16:06,519 --> 00:16:11,919
saying power electronics are in almost

393
00:16:09,360 --> 00:16:13,839
everything you care about these days and

394
00:16:11,919 --> 00:16:15,838
it's only getting more so because we

395
00:16:13,839 --> 00:16:18,839
have to be better about how we use

396
00:16:15,839 --> 00:16:18,839
energy

397
00:16:19,039 --> 00:16:23,879
okay so what's inside a power converter

398
00:16:22,078 --> 00:16:26,239
and we're going to talk about this in

399
00:16:23,879 --> 00:16:30,519
much greater detail but if you want to

400
00:16:26,240 --> 00:16:33,600
think about it what we have

401
00:16:30,519 --> 00:16:35,600
is typically some kind of energy storage

402
00:16:33,600 --> 00:16:38,560
elements these could be inductors or

403
00:16:35,600 --> 00:16:40,519
capacitors or sometimes other things and

404
00:16:38,559 --> 00:16:42,239
what we're going to do is we're going to

405
00:16:40,519 --> 00:16:44,959
use semiconductor switches and we're

406
00:16:42,240 --> 00:16:46,639
going to draw energy from some Source

407
00:16:44,958 --> 00:16:48,198
we're going to manipulate it somehow so

408
00:16:46,639 --> 00:16:49,120
we store it in these energy storage

409
00:16:48,198 --> 00:16:51,758
elements and then we're going to put it

410
00:16:49,120 --> 00:16:55,399
to the output and we're going to repeat

411
00:16:51,759 --> 00:16:58,360
that right so draw transform put it to

412
00:16:55,399 --> 00:16:59,399
the output okay because we do this on a

413
00:16:58,360 --> 00:17:02,399
cyclic

414
00:16:59,399 --> 00:17:04,078
basis we generate sort of Ripple and

415
00:17:02,399 --> 00:17:05,359
potentially noise that could interfere

416
00:17:04,078 --> 00:17:08,000
with things like television or

417
00:17:05,359 --> 00:17:11,318
Electronics so you generally need

418
00:17:08,000 --> 00:17:13,400
filters to do that too we also of course

419
00:17:11,318 --> 00:17:15,240
need to control that flow of energy

420
00:17:13,400 --> 00:17:16,759
right we can't be stupid about it we

421
00:17:15,240 --> 00:17:18,318
have especially for something high

422
00:17:16,759 --> 00:17:21,720
performance like a microprocessor which

423
00:17:18,318 --> 00:17:24,599
might be changing its operation very

424
00:17:21,720 --> 00:17:26,120
very fast we need to control that flow

425
00:17:24,599 --> 00:17:27,958
so there's control circuitry we're going

426
00:17:26,119 --> 00:17:29,558
to be learning about all of the aspects

427
00:17:27,959 --> 00:17:34,360
of Designing

428
00:17:29,558 --> 00:17:36,079
all of these kinds of elements

429
00:17:34,359 --> 00:17:38,678
okay

430
00:17:36,079 --> 00:17:41,199
so we're leveraging sort of everything

431
00:17:38,679 --> 00:17:43,919
from circuit design semiconductor

432
00:17:41,200 --> 00:17:46,880
devices passive components and materials

433
00:17:43,919 --> 00:17:49,840
increasingly packaging and Cooling and

434
00:17:46,880 --> 00:17:51,039
controls also matter and things have

435
00:17:49,839 --> 00:17:55,319
been getting better and better and

436
00:17:51,038 --> 00:17:57,279
better both because the um ways we can

437
00:17:55,319 --> 00:18:00,279
manufacture things get better and

438
00:17:57,279 --> 00:18:03,319
because the devices which we have

439
00:18:00,279 --> 00:18:05,200
our access to in order to implement

440
00:18:03,319 --> 00:18:06,720
these things get better okay and so

441
00:18:05,200 --> 00:18:09,480
we're going to look at some of the

442
00:18:06,720 --> 00:18:11,798
different ways you can do that I'll just

443
00:18:09,480 --> 00:18:14,599
give you

444
00:18:11,798 --> 00:18:16,440
uh one example this is what you would

445
00:18:14,599 --> 00:18:18,359
find something like in a data center

446
00:18:16,440 --> 00:18:21,480
right so they come in they rectify the

447
00:18:18,359 --> 00:18:24,279
voltage they get it to sort of 400 Volts

448
00:18:21,480 --> 00:18:26,200
for reasons we'll go into this converter

449
00:18:24,279 --> 00:18:29,279
here was designed to take that 400 volts

450
00:18:26,200 --> 00:18:31,038
and bring it down to 12 volts okay

451
00:18:29,279 --> 00:18:32,599
that that tiny little thing a little bit

452
00:18:31,038 --> 00:18:35,119
bigger than a penny there actually can

453
00:18:32,599 --> 00:18:36,918
handle a kilowatt then you need more

454
00:18:35,119 --> 00:18:42,158
converters to take it down from there to

455
00:18:36,919 --> 00:18:45,320
the one VT that the processor uses okay

456
00:18:42,159 --> 00:18:48,120
so the sort of a long way of saying all

457
00:18:45,319 --> 00:18:49,960
kinds of things are limited by energy

458
00:18:48,119 --> 00:18:52,119
and how we can control it right across

459
00:18:49,960 --> 00:18:53,759
all these applications and what we're

460
00:18:52,119 --> 00:18:55,759
usually trying to do is how figure out

461
00:18:53,759 --> 00:18:57,440
how to make them smaller and lighter

462
00:18:55,759 --> 00:18:59,359
right if you're taking up 40% of your

463
00:18:57,440 --> 00:19:00,798
iPhone you want

464
00:18:59,359 --> 00:19:02,918
make that thing smaller so it doesn't

465
00:19:00,798 --> 00:19:04,679
take that up and you can replace that

466
00:19:02,919 --> 00:19:06,799
volume either with nothing or with

467
00:19:04,679 --> 00:19:08,519
things that are more interesting to you

468
00:19:06,798 --> 00:19:10,000
we need higher efficiency both for the

469
00:19:08,519 --> 00:19:12,359
converters and the systems how we

470
00:19:10,000 --> 00:19:14,038
process energy can matter to the not

471
00:19:12,359 --> 00:19:15,439
only the ultimate efficiency of the

472
00:19:14,038 --> 00:19:17,519
converter but the efficiency of the

473
00:19:15,440 --> 00:19:19,759
system how it uses energy can be

474
00:19:17,519 --> 00:19:21,879
determined by the Power Electronics we

475
00:19:19,759 --> 00:19:25,640
want higher performance that could mean

476
00:19:21,880 --> 00:19:28,720
higher bandwidth or other aspects and

477
00:19:25,640 --> 00:19:31,038
then there's all kinds of means that we

478
00:19:28,720 --> 00:19:33,440
we can use better electrical processing

479
00:19:31,038 --> 00:19:35,480
to enable new applications so these are

480
00:19:33,440 --> 00:19:38,679
the kind of things that we're going to

481
00:19:35,480 --> 00:19:39,919
learn about this term I'll pause there

482
00:19:38,679 --> 00:19:41,519
i' I've been going on a while are there

483
00:19:39,919 --> 00:19:43,038
any questions about any of this before

484
00:19:41,519 --> 00:19:44,240
we get going this is just to sort of

485
00:19:43,038 --> 00:19:47,038
Orient you as to what we're going to

486
00:19:44,240 --> 00:19:47,038
focus the term

487
00:19:49,440 --> 00:19:56,519
on I can put the slides on canvas

488
00:19:53,079 --> 00:19:56,519
sure any other

489
00:19:57,440 --> 00:20:00,640
questions okay

490
00:20:01,319 --> 00:20:07,558
okay I will just give

491
00:20:05,200 --> 00:20:11,440
you a slight

492
00:20:07,558 --> 00:20:13,558
notion okay just and this is a

493
00:20:11,440 --> 00:20:16,279
favorite thing I like to bring in just

494
00:20:13,558 --> 00:20:17,720
to show you the kind of things we're

495
00:20:16,279 --> 00:20:20,558
going to look at this

496
00:20:17,720 --> 00:20:22,240
term this is a piece of commercial

497
00:20:20,558 --> 00:20:23,440
Hardware from a company called MKS

498
00:20:22,240 --> 00:20:24,519
instruments that I just happen to have

499
00:20:23,440 --> 00:20:27,600
in my

500
00:20:24,519 --> 00:20:29,000
office this input piece is a filter so

501
00:20:27,599 --> 00:20:30,399
you don't create electrom magnetic

502
00:20:29,000 --> 00:20:31,960
interference and you don't generate

503
00:20:30,400 --> 00:20:35,679
noise you don't

504
00:20:31,960 --> 00:20:37,880
want then this piece here takes energy

505
00:20:35,679 --> 00:20:40,798
from the 60 HZ grid and generates DC

506
00:20:37,880 --> 00:20:42,320
from it and it has to do it while making

507
00:20:40,798 --> 00:20:44,879
the whole thing look like a resistor to

508
00:20:42,319 --> 00:20:46,798
the grid so you don't mess up the grid

509
00:20:44,880 --> 00:20:49,039
okay that's what this part does then it

510
00:20:46,798 --> 00:20:51,359
has these isolated dcdc converters that

511
00:20:49,038 --> 00:20:54,319
can take that DC voltage and generate

512
00:20:51,359 --> 00:20:58,399
other DC voltages referenced in other

513
00:20:54,319 --> 00:21:00,798
ways and without worrying about uh sort

514
00:20:58,400 --> 00:21:04,280
of currents going back to ground okay

515
00:21:00,798 --> 00:21:07,319
it's galvanically isolated and then it

516
00:21:04,279 --> 00:21:09,240
takes that energy and goes back DC to AC

517
00:21:07,319 --> 00:21:11,720
okay now in some systems you might go DC

518
00:21:09,240 --> 00:21:13,159
to AC for 60 hertz to to generate into

519
00:21:11,720 --> 00:21:15,400
the Grid or for a motor or something

520
00:21:13,159 --> 00:21:17,480
else this particular one has these

521
00:21:15,400 --> 00:21:20,640
outputs that are at 13 megahertz for

522
00:21:17,480 --> 00:21:22,960
driving plasmas to process

523
00:21:20,640 --> 00:21:25,600
semiconductors okay but you get all

524
00:21:22,960 --> 00:21:28,159
these kind of functions AC to DC DC to

525
00:21:25,599 --> 00:21:29,719
DC DC to AC and we're going to learn the

526
00:21:28,159 --> 00:21:31,919
first of all the

527
00:21:29,720 --> 00:21:34,798
underlying uh principles of doing all

528
00:21:31,919 --> 00:21:38,360
these things and how to design them okay

529
00:21:34,798 --> 00:21:41,038
so the the the real goal

530
00:21:38,359 --> 00:21:43,678
is by the time you walk out of here you

531
00:21:41,038 --> 00:21:44,919
should have all the tools to go off and

532
00:21:43,679 --> 00:21:47,640
design Power

533
00:21:44,919 --> 00:21:49,759
Electronics for all kinds of

534
00:21:47,640 --> 00:21:50,720
applications and and in fact graduates

535
00:21:49,759 --> 00:21:53,679
of this

536
00:21:50,720 --> 00:21:55,440
class have worked on electric vehicles

537
00:21:53,679 --> 00:21:57,000
Char battery charger

538
00:21:55,440 --> 00:21:59,440
solar

539
00:21:57,000 --> 00:22:01,319
uh communication

540
00:21:59,440 --> 00:22:04,320
systems data

541
00:22:01,319 --> 00:22:06,678
centers the in fact the the power supply

542
00:22:04,319 --> 00:22:08,200
I usually use for my laptop and the in

543
00:22:06,679 --> 00:22:11,000
fact the wireless charger for my

544
00:22:08,200 --> 00:22:13,319
eyewatch were all designed or the teams

545
00:22:11,000 --> 00:22:15,119
were led by graduates of this class

546
00:22:13,319 --> 00:22:18,678
right so this the goal is to give you

547
00:22:15,119 --> 00:22:21,519
the tools you need to go do these things

548
00:22:18,679 --> 00:22:25,200
okay so with

549
00:22:21,519 --> 00:22:29,639
that um let me

550
00:22:25,200 --> 00:22:31,600
start by just giving you a sense

551
00:22:29,640 --> 00:22:36,240
of

552
00:22:31,599 --> 00:22:36,240
um what goes on inside Power

553
00:22:40,558 --> 00:22:46,798
Electronics so let's think of the

554
00:22:43,720 --> 00:22:49,640
simplest case I have some DC input

555
00:22:46,798 --> 00:22:54,158
voltage and I'd like some other DC

556
00:22:49,640 --> 00:22:54,159
voltage so suppose I have some

557
00:22:54,319 --> 00:22:59,639
input that's you know maybe it's 9 volts

558
00:22:58,079 --> 00:23:02,639
to 6 16

559
00:22:59,640 --> 00:23:04,200
Vols I'm making that up arbitrarily but

560
00:23:02,640 --> 00:23:06,880
that's roughly what you might get in a

561
00:23:04,200 --> 00:23:09,240
typical vehicle right out of the

562
00:23:06,880 --> 00:23:11,799
cigarette lighter

563
00:23:09,240 --> 00:23:13,759
okay and suppose I want and I'll call

564
00:23:11,798 --> 00:23:16,798
this

565
00:23:13,759 --> 00:23:18,119
VN and suppose I want here's some load

566
00:23:16,798 --> 00:23:21,079
that I'm going to represent with a

567
00:23:18,119 --> 00:23:25,199
resistor I'm going to call that V out

568
00:23:21,079 --> 00:23:27,278
okay and suppose I want EG 5

569
00:23:25,200 --> 00:23:29,720
volts right to power something that

570
00:23:27,278 --> 00:23:33,359
takes five volts

571
00:23:29,720 --> 00:23:36,600
right what's the most obvious and simple

572
00:23:33,359 --> 00:23:39,199
way to get 5 volts at my output from

573
00:23:36,599 --> 00:23:39,199
some higher

574
00:23:41,679 --> 00:23:47,919
voltage voltage divider precisely right

575
00:23:44,960 --> 00:23:50,480
I could come up here I could say okay

576
00:23:47,919 --> 00:23:50,480
let me put

577
00:23:50,558 --> 00:23:56,519
in some volt variable

578
00:23:53,519 --> 00:23:58,839
resistor and I'll drop down this voltage

579
00:23:56,519 --> 00:24:02,200
to give me the voltage I want and I'm

580
00:23:58,839 --> 00:24:03,798
done and in fact a lot of systems that's

581
00:24:02,200 --> 00:24:07,798
exactly more or less what they have

582
00:24:03,798 --> 00:24:09,400
inside them in fact inside most

583
00:24:07,798 --> 00:24:12,599
integrated circuits there's lots of

584
00:24:09,400 --> 00:24:14,320
these things going on okay well okay

585
00:24:12,599 --> 00:24:18,079
they don't do it quite this way what do

586
00:24:14,319 --> 00:24:18,079
they really do

587
00:24:18,599 --> 00:24:24,158
they will take VN and what they will do

588
00:24:21,960 --> 00:24:26,679
is they'll use some kind of transistor a

589
00:24:24,159 --> 00:24:31,240
mosfet or a bipolar

590
00:24:26,679 --> 00:24:34,000
transistor and they will treat that

591
00:24:31,240 --> 00:24:35,679
essentially as a variable resistor right

592
00:24:34,000 --> 00:24:38,200
so I implement the variable resistor

593
00:24:35,679 --> 00:24:40,679
with a controlled transistor and I will

594
00:24:38,200 --> 00:24:43,278
come and I'll have some feedback loop

595
00:24:40,679 --> 00:24:45,600
I'll Fe feed in a reference

596
00:24:43,278 --> 00:24:47,880
voltage and I'll measure the output

597
00:24:45,599 --> 00:24:49,918
voltage and I'll control the Gate of

598
00:24:47,880 --> 00:24:51,640
this transistor and essentially make

599
00:24:49,919 --> 00:24:53,640
that transistor look like a variable

600
00:24:51,640 --> 00:24:55,960
resistor and control the voltage

601
00:24:53,640 --> 00:24:58,038
division so that even if this voltage

602
00:24:55,960 --> 00:25:01,278
varies between 9 and 16 volts I always

603
00:24:58,038 --> 00:25:05,158
get my 5 Vols output

604
00:25:01,278 --> 00:25:07,398
Okay and like I said that's very

605
00:25:05,159 --> 00:25:08,720
common but what's the problem with this

606
00:25:07,398 --> 00:25:10,519
well there's a whole lot of problems

607
00:25:08,720 --> 00:25:13,839
with this right why why wouldn't you

608
00:25:10,519 --> 00:25:15,960
want to do this uh

609
00:25:13,839 --> 00:25:19,079
in typical

610
00:25:15,960 --> 00:25:20,840
operation efficiency terrible efficiency

611
00:25:19,079 --> 00:25:25,599
yes

612
00:25:20,839 --> 00:25:27,798
exactly so let's think about this if I

613
00:25:25,599 --> 00:25:30,319
accept the fact let me call this current

614
00:25:27,798 --> 00:25:30,319
I in

615
00:25:33,798 --> 00:25:38,839
okay and this current I

616
00:25:37,278 --> 00:25:42,240
out

617
00:25:38,839 --> 00:25:45,158
okay if this thing does act exactly like

618
00:25:42,240 --> 00:25:47,240
a variable resistor the input currents

619
00:25:45,159 --> 00:25:49,080
equal to the output current now this

620
00:25:47,240 --> 00:25:50,440
actually a real system might have some

621
00:25:49,079 --> 00:25:52,678
current that actually also goes to

622
00:25:50,440 --> 00:25:54,278
ground let's take the best case where

623
00:25:52,679 --> 00:25:56,559
the output current is equal to the input

624
00:25:54,278 --> 00:26:00,798
current okay what would be the

625
00:25:56,558 --> 00:26:00,798
efficiency of this Beast well the

626
00:26:05,679 --> 00:26:11,480
efficiency the efficiency is equal to

627
00:26:07,798 --> 00:26:13,839
the output power over the input power

628
00:26:11,480 --> 00:26:15,919
right I'm drawing energy maybe from my

629
00:26:13,839 --> 00:26:17,359
car battery or whatever my battery

630
00:26:15,919 --> 00:26:19,640
source is and I'm delivering it to the

631
00:26:17,359 --> 00:26:23,158
output but not all of it's getting to

632
00:26:19,640 --> 00:26:24,919
the output so the output power is V out

633
00:26:23,159 --> 00:26:30,278
time I

634
00:26:24,919 --> 00:26:33,000
out and my input power is VN time I in

635
00:26:30,278 --> 00:26:36,079
and I just told you that I out was equal

636
00:26:33,000 --> 00:26:37,640
to I in in the best case so that's V out

637
00:26:36,079 --> 00:26:41,240
over

638
00:26:37,640 --> 00:26:44,399
VN right so if I'm coming in from 15

639
00:26:41,240 --> 00:26:47,440
volts and I'm getting five

640
00:26:44,398 --> 00:26:50,719
volts that's 33% efficiency right I've

641
00:26:47,440 --> 00:26:52,240
taken 2/3 of my energy and thrown it

642
00:26:50,720 --> 00:26:54,839
away

643
00:26:52,240 --> 00:26:58,000
now if I got lots of energy floating

644
00:26:54,839 --> 00:26:59,359
around and I'm processing a microwatt

645
00:26:58,000 --> 00:27:01,079
maybe maybe I don't care maybe I'll live

646
00:26:59,359 --> 00:27:03,240
with that because this thing's pretty

647
00:27:01,079 --> 00:27:05,038
simple right it's a transistor it's a

648
00:27:03,240 --> 00:27:06,839
power transistor and some controls and

649
00:27:05,038 --> 00:27:09,000
they can often put all that on one

650
00:27:06,839 --> 00:27:11,398
integrated circuit or even as a subblock

651
00:27:09,000 --> 00:27:13,038
on an integrated circuit I might still

652
00:27:11,398 --> 00:27:17,278
need some filtering it's not it's not

653
00:27:13,038 --> 00:27:21,119
quite as easy as it sounds but um pretty

654
00:27:17,278 --> 00:27:23,038
much it's relatively simple but my

655
00:27:21,119 --> 00:27:24,678
efficiency is miserable now if I thought

656
00:27:23,038 --> 00:27:27,640
about in your in your

657
00:27:24,679 --> 00:27:29,759
computer right your desktop computer

658
00:27:27,640 --> 00:27:31,919
typically the intermediate Supply that

659
00:27:29,759 --> 00:27:33,278
you're getting after it's sort of come

660
00:27:31,919 --> 00:27:35,840
in from the grid and been transformed

661
00:27:33,278 --> 00:27:37,798
down you get 12 volts right and let's

662
00:27:35,839 --> 00:27:40,720
say your computer is it sort of it

663
00:27:37,798 --> 00:27:42,398
depends on what it's doing but say it's

664
00:27:40,720 --> 00:27:45,720
operating at a volt right so then you're

665
00:27:42,398 --> 00:27:47,479
less than 10% efficient right and if you

666
00:27:45,720 --> 00:27:49,759
think that you know you can have a

667
00:27:47,480 --> 00:27:53,440
microprocessor that's taking 200 amps at

668
00:27:49,759 --> 00:27:55,798
a volt or few hundred Watts suddenly if

669
00:27:53,440 --> 00:27:58,200
I've got less than 10% efficiency on 200

670
00:27:55,798 --> 00:27:59,639
Watts that means I need to put in a few

671
00:27:58,200 --> 00:28:01,278
kilowatts well you can't even plug that

672
00:27:59,640 --> 00:28:03,038
into the wall never mind the fact you've

673
00:28:01,278 --> 00:28:06,240
just made a massive room heater right

674
00:28:03,038 --> 00:28:10,119
that's that's like that'd be great for

675
00:28:06,240 --> 00:28:13,599
heating your dorm room um but pretty

676
00:28:10,119 --> 00:28:17,439
terrible for the overall system okay so

677
00:28:13,599 --> 00:28:19,319
the number one reason we don't like this

678
00:28:17,440 --> 00:28:21,519
solution is

679
00:28:19,319 --> 00:28:24,359
efficiency good thing it's simple bad

680
00:28:21,519 --> 00:28:28,240
thing it's terrible efficiency this

681
00:28:24,359 --> 00:28:28,240
technique I should have noted

682
00:28:28,278 --> 00:28:33,519
is what's known for historical reasons

683
00:28:30,558 --> 00:28:35,798
as a quote unquote

684
00:28:33,519 --> 00:28:40,159
linear power

685
00:28:35,798 --> 00:28:43,519
supply why linear I think only because

686
00:28:40,159 --> 00:28:45,200
analog circuits kind of a category of

687
00:28:43,519 --> 00:28:47,120
them became known as quote unquote

688
00:28:45,200 --> 00:28:49,080
linear circuits there's nothing really

689
00:28:47,119 --> 00:28:51,839
that linear about it but this would be

690
00:28:49,079 --> 00:28:54,720
called a linear power converter or or

691
00:28:51,839 --> 00:28:56,678
some sometimes a linear regulator is

692
00:28:54,720 --> 00:28:59,399
what it would be called

693
00:28:56,679 --> 00:29:01,360
okay for obvious reasons I hate throwing

694
00:28:59,398 --> 00:29:03,000
away energy we're not going to talk

695
00:29:01,359 --> 00:29:04,639
about linear Regulators at all in this

696
00:29:03,000 --> 00:29:06,359
class and there's plenty of classes

697
00:29:04,640 --> 00:29:09,679
where you can learn about that we want

698
00:29:06,359 --> 00:29:13,479
to do things some better way that's not

699
00:29:09,679 --> 00:29:18,159
going to burn lots of energy okay so

700
00:29:13,480 --> 00:29:22,079
ideally you know in my world the goal is

701
00:29:18,159 --> 00:29:24,519
to take as much of the input energy in

702
00:29:22,079 --> 00:29:26,319
and put it to the output right and

703
00:29:24,519 --> 00:29:29,038
that's important because think about it

704
00:29:26,319 --> 00:29:31,319
this way I I showed you a photo graph of

705
00:29:29,038 --> 00:29:35,319
something that was you know really tiny

706
00:29:31,319 --> 00:29:38,200
maybe that big right and that thick and

707
00:29:35,319 --> 00:29:40,038
was processing a kilowatt right if I

708
00:29:38,200 --> 00:29:42,679
don't do that at really high efficiency

709
00:29:40,038 --> 00:29:45,319
that thing will burn up right so in

710
00:29:42,679 --> 00:29:48,399
order to make something small I need to

711
00:29:45,319 --> 00:29:50,398
make it efficient all right so we want

712
00:29:48,398 --> 00:29:52,798
almost all of the energy at the input to

713
00:29:50,398 --> 00:29:55,079
get to the output well how can we do

714
00:29:52,798 --> 00:29:57,798
that let's think of a completely

715
00:29:55,079 --> 00:30:00,918
different way we might achieve this same

716
00:29:57,798 --> 00:30:03,759
function function all right and here's

717
00:30:00,919 --> 00:30:03,759
the idea here's my

718
00:30:09,000 --> 00:30:15,240
input I'm going to create a switch here

719
00:30:12,720 --> 00:30:16,440
single pole double throw switch now

720
00:30:15,240 --> 00:30:17,679
we're not going to go get physical

721
00:30:16,440 --> 00:30:19,360
switches we're probably going to get

722
00:30:17,679 --> 00:30:22,320
semiconductor devices and make it do

723
00:30:19,359 --> 00:30:24,278
something like this but we could use

724
00:30:22,319 --> 00:30:27,599
anything any technology that was

725
00:30:24,278 --> 00:30:29,759
practical as a switch okay and let me

726
00:30:27,599 --> 00:30:30,959
just Define if I'm going to define a

727
00:30:29,759 --> 00:30:33,879
switching function that I'm going to

728
00:30:30,960 --> 00:30:37,880
call Q of T if Q of T is

729
00:30:33,880 --> 00:30:40,760
one I'll connect the switch to the input

730
00:30:37,880 --> 00:30:40,760
if Q of T is

731
00:30:41,159 --> 00:30:47,559
zero I'll connect the switch to the

732
00:30:43,798 --> 00:30:52,038
ground okay so this notion this voltage

733
00:30:47,558 --> 00:30:52,038
okay maybe I'll call this voltage

734
00:30:54,079 --> 00:30:59,879
VX all right so one thing I could do is

735
00:30:57,440 --> 00:31:02,880
I could say okay let me just hook this

736
00:30:59,880 --> 00:31:06,559
up to my load here's my resistive

737
00:31:02,880 --> 00:31:10,240
load whatever it is and I'll call this V

738
00:31:06,558 --> 00:31:12,798
out all right well all right what would

739
00:31:10,240 --> 00:31:15,319
that look like well let me Define my

740
00:31:12,798 --> 00:31:15,319
switching

741
00:31:22,159 --> 00:31:28,120
function I'm going to put the switch in

742
00:31:25,119 --> 00:31:29,879
the up position for a little while then

743
00:31:28,119 --> 00:31:31,759
I'll put it in the down

744
00:31:29,880 --> 00:31:33,679
position by setting the switching

745
00:31:31,759 --> 00:31:35,158
function to zero and then I'll just

746
00:31:33,679 --> 00:31:36,720
repeat that so I said we're going to

747
00:31:35,159 --> 00:31:39,399
operate in some kind of repetitive

748
00:31:36,720 --> 00:31:43,480
fashion here and so

749
00:31:39,398 --> 00:31:46,038
forth let me operate with some period

750
00:31:43,480 --> 00:31:47,399
T okay that's mean my switching period

751
00:31:46,038 --> 00:31:50,440
in this example I'm showing you is a

752
00:31:47,398 --> 00:31:52,959
fixed switching period okay and I will

753
00:31:50,440 --> 00:31:56,120
keep the switch in the up position some

754
00:31:52,960 --> 00:31:59,000
fraction of the time that I'll call DT

755
00:31:56,119 --> 00:32:01,518
so D is a fraction zero is less than D

756
00:31:59,000 --> 00:32:01,519
is less than

757
00:32:01,880 --> 00:32:07,200
one

758
00:32:03,599 --> 00:32:09,439
okay so if I do that then what do I get

759
00:32:07,200 --> 00:32:11,278
for VX VX is going to look something

760
00:32:09,440 --> 00:32:15,519
like

761
00:32:11,278 --> 00:32:19,319
this okay um when the switch is in the

762
00:32:15,519 --> 00:32:19,319
up position VX equals

763
00:32:21,278 --> 00:32:29,599
VN so this is VX when the switch is in

764
00:32:24,720 --> 00:32:29,600
the down position VX is equal to zero

765
00:32:31,759 --> 00:32:36,839
okay and I rinse and repeat and I get

766
00:32:34,480 --> 00:32:40,960
this now now I have this pulsating

767
00:32:36,839 --> 00:32:42,519
voltage VX okay what's the average value

768
00:32:40,960 --> 00:32:45,720
of that voltage

769
00:32:42,519 --> 00:32:47,399
VX right I can take you know simple

770
00:32:45,720 --> 00:32:50,720
integration right one over T the

771
00:32:47,398 --> 00:32:53,879
integral of VX of T over a period

772
00:32:50,720 --> 00:32:58,798
T okay and what I would

773
00:32:53,880 --> 00:33:01,159
find is the average voltage of VX

774
00:32:58,798 --> 00:33:05,359
is equal to D *

775
00:33:01,159 --> 00:33:08,880
VN all right so I can create a waveform

776
00:33:05,359 --> 00:33:11,519
here whose average value is something

777
00:33:08,880 --> 00:33:13,480
different than VN just by controlling

778
00:33:11,519 --> 00:33:19,960
this timing

779
00:33:13,480 --> 00:33:22,919
D all right so now if my load resistor

780
00:33:19,960 --> 00:33:25,919
here was a space heater you know maybe

781
00:33:22,919 --> 00:33:27,519
this is some load resistance RL and I

782
00:33:25,919 --> 00:33:29,840
wanted to modulate the power to that

783
00:33:27,519 --> 00:33:32,120
load resistance by controlling the

784
00:33:29,839 --> 00:33:35,278
average voltage on the load resistance

785
00:33:32,119 --> 00:33:38,518
then this technique would work

786
00:33:35,278 --> 00:33:40,919
great if on the other hand my load was a

787
00:33:38,519 --> 00:33:43,000
microprocessor and I start you know

788
00:33:40,919 --> 00:33:44,240
pulsing 12 volts between 12 volts and

789
00:33:43,000 --> 00:33:47,079
zero on it I'm probably going to blow it

790
00:33:44,240 --> 00:33:49,038
up right so that's no good all right but

791
00:33:47,079 --> 00:33:52,038
this notion is at least that I can

792
00:33:49,038 --> 00:33:55,038
control an average voltage by pulsing a

793
00:33:52,038 --> 00:33:58,599
set a switch okay and this would be

794
00:33:55,038 --> 00:34:01,200
known as pwm or pulse width modulation

795
00:33:58,599 --> 00:34:02,959
because I control the average volage by

796
00:34:01,200 --> 00:34:05,080
the fraction of the time the switch is

797
00:34:02,960 --> 00:34:08,480
in one position versus the

798
00:34:05,079 --> 00:34:11,440
other okay so that's that's the basic

799
00:34:08,480 --> 00:34:12,960
concept we're going to be using how do I

800
00:34:11,440 --> 00:34:16,519
fix this

801
00:34:12,960 --> 00:34:19,440
little problem of in practice right what

802
00:34:16,519 --> 00:34:21,280
I wanted was a DC voltage what I got was

803
00:34:19,440 --> 00:34:23,800
a pulsating voltage that just happened

804
00:34:21,280 --> 00:34:25,720
to have the right average value well I

805
00:34:23,800 --> 00:34:28,519
could go do something like this maybe

806
00:34:25,719 --> 00:34:30,158
I'll go back and say okay let me throw

807
00:34:28,519 --> 00:34:33,838
in a

808
00:34:30,159 --> 00:34:36,280
filter and extract out the component I

809
00:34:33,838 --> 00:34:39,159
want right I want the average value of

810
00:34:36,280 --> 00:34:43,000
VX so maybe I'll come back here and say

811
00:34:39,159 --> 00:34:46,119
okay let me throw in a filter and I'll

812
00:34:43,000 --> 00:34:46,119
use an inductor

813
00:34:47,159 --> 00:34:53,240
here an l and if I want optionally I can

814
00:34:50,960 --> 00:34:57,760
put a capacitor here

815
00:34:53,239 --> 00:34:59,319
C okay and you know I think people can

816
00:34:57,760 --> 00:35:02,720
look at

817
00:34:59,320 --> 00:35:07,079
this filter block and recognize that as

818
00:35:02,719 --> 00:35:09,319
a low pass filter the DC component of VX

819
00:35:07,079 --> 00:35:13,440
passes through the filter to the

820
00:35:09,320 --> 00:35:15,039
output and the AC component of VX gets

821
00:35:13,440 --> 00:35:17,720
rejected by the filter and doesn't get

822
00:35:15,039 --> 00:35:19,679
to the output so in this case I might

823
00:35:17,719 --> 00:35:22,679
get an output voltage V out that looks

824
00:35:19,679 --> 00:35:24,960
something like this I'm going to sort of

825
00:35:22,679 --> 00:35:27,279
make this up but you know I'm amplifying

826
00:35:24,960 --> 00:35:28,838
the Ripple but eventually it's going to

827
00:35:27,280 --> 00:35:30,920
filter

828
00:35:28,838 --> 00:35:33,400
the energy content of that and the

829
00:35:30,920 --> 00:35:35,159
fundamental and higher harmonic terms of

830
00:35:33,400 --> 00:35:37,599
VX are going to go away and the DC terms

831
00:35:35,159 --> 00:35:40,799
going to go through and I get an output

832
00:35:37,599 --> 00:35:43,519
voltage V out that's very close to

833
00:35:40,800 --> 00:35:46,039
whatever value I want and if I'm

834
00:35:43,519 --> 00:35:49,199
basically make the filter cut off hard

835
00:35:46,039 --> 00:35:51,318
enough I can't distinguish between V out

836
00:35:49,199 --> 00:35:55,399
and the average value of VX and I get

837
00:35:51,318 --> 00:35:59,639
exactly what I wanted Okay so we've

838
00:35:55,400 --> 00:35:59,639
essentially now created

839
00:36:00,960 --> 00:36:03,639
a voltage

840
00:36:04,358 --> 00:36:09,279
converter that lets me use this

841
00:36:07,480 --> 00:36:13,039
pulsewidth modulation by controlling

842
00:36:09,280 --> 00:36:15,920
this duty cycle D to regulate the output

843
00:36:13,039 --> 00:36:17,960
just the way I wanted so instead of you

844
00:36:15,920 --> 00:36:19,760
know here I'm just changing the gate

845
00:36:17,960 --> 00:36:21,880
voltage on my transistor to control the

846
00:36:19,760 --> 00:36:23,160
output here I'm changing timing I'm

847
00:36:21,880 --> 00:36:26,119
going to control

848
00:36:23,159 --> 00:36:27,679
timing okay and by controlling timing I

849
00:36:26,119 --> 00:36:31,318
control average value and then I get

850
00:36:27,679 --> 00:36:33,919
what I want right any questions about

851
00:36:31,318 --> 00:36:37,559
that what's what's the

852
00:36:33,920 --> 00:36:41,680
efficiency that is an excellent question

853
00:36:37,559 --> 00:36:41,679
the answer is

854
00:36:42,239 --> 00:36:47,199
um ideally theoretically the efficiency

855
00:36:46,119 --> 00:36:51,358
can be

856
00:36:47,199 --> 00:36:54,759
100% in reality it can't be why do I say

857
00:36:51,358 --> 00:36:58,960
the efficiency can ideally be

858
00:36:54,760 --> 00:37:02,359
100% well how would I implement

859
00:36:58,960 --> 00:37:04,159
this box in the real world usually I I

860
00:37:02,358 --> 00:37:06,119
don't get semiconductor single pole

861
00:37:04,159 --> 00:37:08,598
double throw switches the way I would

862
00:37:06,119 --> 00:37:11,680
usually build this Beast is like

863
00:37:08,599 --> 00:37:14,359
this okay I would usually have a first

864
00:37:11,679 --> 00:37:17,399
switch and a second switch implemented

865
00:37:14,358 --> 00:37:18,519
like this so I close this when Q of T is

866
00:37:17,400 --> 00:37:21,200
equal to

867
00:37:18,519 --> 00:37:22,800
one and I close this one when Q of T is

868
00:37:21,199 --> 00:37:29,318
equal to

869
00:37:22,800 --> 00:37:29,318
zero okay and then I build my filter

870
00:37:30,318 --> 00:37:37,719
and then I put my load on here okay

871
00:37:35,280 --> 00:37:40,119
so what would be the efficiency of this

872
00:37:37,719 --> 00:37:44,039
thing well let's think about

873
00:37:40,119 --> 00:37:46,400
this um this is voltage Vex and this is

874
00:37:44,039 --> 00:37:46,400
voltage

875
00:37:46,440 --> 00:37:49,599
vout all

876
00:37:50,838 --> 00:37:56,799
right what power is theoretically

877
00:37:54,039 --> 00:37:59,079
dissipated in my switch if I have an

878
00:37:56,800 --> 00:38:01,680
ideal switch has zero resistance when

879
00:37:59,079 --> 00:38:02,800
it's on and has infinite resistance when

880
00:38:01,679 --> 00:38:06,679
it's

881
00:38:02,800 --> 00:38:08,880
off what's that zero power why because

882
00:38:06,679 --> 00:38:12,838
the power dissipated the power that goes

883
00:38:08,880 --> 00:38:17,358
into this box let me call this V

884
00:38:12,838 --> 00:38:19,880
switch let me call this I switch okay

885
00:38:17,358 --> 00:38:22,039
well P switch the power going into the

886
00:38:19,880 --> 00:38:25,960
switch the power being dissipated in the

887
00:38:22,039 --> 00:38:28,039
switch is going to be V switch time I

888
00:38:25,960 --> 00:38:32,880
switch

889
00:38:28,039 --> 00:38:35,358
okay well if it's an ideal switch then

890
00:38:32,880 --> 00:38:37,880
if the switch is on V switch is

891
00:38:35,358 --> 00:38:40,719
zero right it's ideal so it has no

892
00:38:37,880 --> 00:38:42,519
voltage drop when it's on so the power

893
00:38:40,719 --> 00:38:44,598
when it's on is

894
00:38:42,519 --> 00:38:46,599
zero when the switch is off it has

895
00:38:44,599 --> 00:38:50,359
infinite resistance so the switch is

896
00:38:46,599 --> 00:38:52,519
current zero so basically the power

897
00:38:50,358 --> 00:38:54,318
going into the switch if it's an ideal

898
00:38:52,519 --> 00:38:57,719
switch

899
00:38:54,318 --> 00:39:01,119
um is ideally zero so these these

900
00:38:57,719 --> 00:39:02,639
elements this ideal switch is a lossless

901
00:39:01,119 --> 00:39:05,079
element

902
00:39:02,639 --> 00:39:07,920
right

903
00:39:05,079 --> 00:39:10,839
likewise I wasn't I didn't just randomly

904
00:39:07,920 --> 00:39:14,358
choose any filter here right I chose an

905
00:39:10,838 --> 00:39:16,000
LC filter why did I choose an LC filter

906
00:39:14,358 --> 00:39:17,639
I choose an LC filter because inductors

907
00:39:16,000 --> 00:39:19,599
and capacitors are energy storage

908
00:39:17,639 --> 00:39:21,440
elements if they're ideal then they

909
00:39:19,599 --> 00:39:25,960
store energy but they don't dissipate

910
00:39:21,440 --> 00:39:28,559
energy right so basically

911
00:39:25,960 --> 00:39:30,880
everything in the box here everything

912
00:39:28,559 --> 00:39:33,400
between the input and the output is a

913
00:39:30,880 --> 00:39:36,119
lossless element so then one would

914
00:39:33,400 --> 00:39:39,480
assume that if every element's lossless

915
00:39:36,119 --> 00:39:42,000
any energy walking in to the left comes

916
00:39:39,480 --> 00:39:44,880
out to the right right and that's how

917
00:39:42,000 --> 00:39:48,760
that that kilowatt little 400 volt to

918
00:39:44,880 --> 00:39:51,599
12vt converter I showed you um in the

919
00:39:48,760 --> 00:39:54,319
photo is about 97% efficient it's not

920
00:39:51,599 --> 00:39:55,920
100% because you know the wires have

921
00:39:54,318 --> 00:39:57,519
some resistance and the switches have

922
00:39:55,920 --> 00:39:58,720
some on-state resistance a whole bunch

923
00:39:57,519 --> 00:40:02,559
of things that contribute to loss and

924
00:39:58,719 --> 00:40:05,399
we'll talk about that um but I can make

925
00:40:02,559 --> 00:40:08,000
it really close to 100% even though I

926
00:40:05,400 --> 00:40:09,519
might be doing a huge step down right so

927
00:40:08,000 --> 00:40:11,800
if I tried to build a linear regulator

928
00:40:09,519 --> 00:40:13,800
that was going from 400 to 12 volts

929
00:40:11,800 --> 00:40:14,920
that' be about 2 and a half% efficient

930
00:40:13,800 --> 00:40:16,720
right so if I want to generate a

931
00:40:14,920 --> 00:40:19,760
kilowatt at 2 and a half% efficiency

932
00:40:16,719 --> 00:40:24,639
what is that 40 kilowatt input and

933
00:40:19,760 --> 00:40:26,440
instead what I get is sort of like 1.03

934
00:40:24,639 --> 00:40:27,879
kilowatt input to generate a kilowatt

935
00:40:26,440 --> 00:40:30,440
output right

936
00:40:27,880 --> 00:40:33,760
so the whole Magic that we're going to

937
00:40:30,440 --> 00:40:36,000
talk about this term is how can I use

938
00:40:33,760 --> 00:40:38,760
sort of perfectly lossless elements draw

939
00:40:36,000 --> 00:40:41,599
energy in process it and put it out the

940
00:40:38,760 --> 00:40:43,720
other side okay and by the way I should

941
00:40:41,599 --> 00:40:45,960
say not only did I say oh inductors and

942
00:40:43,719 --> 00:40:50,039
capacitors are lossless in principle

943
00:40:45,960 --> 00:40:54,119
lossless elements uh it wasn't an

944
00:40:50,039 --> 00:40:57,679
accident that we put an inductor

945
00:40:54,119 --> 00:40:59,440
here right because think about it when

946
00:40:57,679 --> 00:41:03,078
this switch is

947
00:40:59,440 --> 00:41:04,920
closed right I have V in on this side of

948
00:41:03,079 --> 00:41:07,480
the inductor and V out on this side of

949
00:41:04,920 --> 00:41:10,838
the inductor and I have current flowing

950
00:41:07,480 --> 00:41:13,960
this way right well what's happening

951
00:41:10,838 --> 00:41:15,799
when this switch is closed basically

952
00:41:13,960 --> 00:41:17,400
there's voltage across this inductor and

953
00:41:15,800 --> 00:41:19,839
current going through it we are storing

954
00:41:17,400 --> 00:41:21,559
energy in that inductor so the

955
00:41:19,838 --> 00:41:22,880
difference in voltage between the input

956
00:41:21,559 --> 00:41:24,279
and the output is basically putting

957
00:41:22,880 --> 00:41:26,680
energy in the

958
00:41:24,280 --> 00:41:28,079
inductor in this the other part of the

959
00:41:26,679 --> 00:41:30,159
cycle

960
00:41:28,079 --> 00:41:31,440
when I turn this switch off and this

961
00:41:30,159 --> 00:41:34,318
switch

962
00:41:31,440 --> 00:41:36,679
on basically I'm taking now I have a

963
00:41:34,318 --> 00:41:38,079
negative voltage across the inductor I'm

964
00:41:36,679 --> 00:41:40,159
taking energy out of the inductor and

965
00:41:38,079 --> 00:41:43,039
put it in the output so essentially I'm

966
00:41:40,159 --> 00:41:45,440
using this inductor as a filter but it's

967
00:41:43,039 --> 00:41:48,279
also an intermediate store of energy

968
00:41:45,440 --> 00:41:50,318
that lets me kind of take energy from

969
00:41:48,280 --> 00:41:52,920
the input and transfer to the output

970
00:41:50,318 --> 00:41:54,960
with a voltage conversion without losing

971
00:41:52,920 --> 00:41:57,639
any of the

972
00:41:54,960 --> 00:42:01,440
energy excellent question long answer to

973
00:41:57,639 --> 00:42:01,440
a short question any other

974
00:42:04,119 --> 00:42:12,519
questions okay so as I said um my goal

975
00:42:09,480 --> 00:42:14,079
is to sort of first of all teach you a

976
00:42:12,519 --> 00:42:16,400
lot of the underlying principles this is

977
00:42:14,079 --> 00:42:18,280
the this is the world's if you will

978
00:42:16,400 --> 00:42:20,079
simplest switching power converter so

979
00:42:18,280 --> 00:42:23,200
the when we use this technique we also

980
00:42:20,079 --> 00:42:23,200
often say we're switched

981
00:42:24,079 --> 00:42:27,680
mode all right with the notion that

982
00:42:26,400 --> 00:42:29,480
we're going to use

983
00:42:27,679 --> 00:42:31,480
switches and energy storage elements to

984
00:42:29,480 --> 00:42:33,159
process energy and that's sort of what

985
00:42:31,480 --> 00:42:35,440
sits at the core of Power

986
00:42:33,159 --> 00:42:38,358
Electronics okay and as I said we're

987
00:42:35,440 --> 00:42:39,960
going to look at all of the aspects how

988
00:42:38,358 --> 00:42:41,318
do you design these things how do you

989
00:42:39,960 --> 00:42:43,318
control them how do you design the

990
00:42:41,318 --> 00:42:44,480
components and by the time we're done

991
00:42:43,318 --> 00:42:46,920
you should be able to put it all

992
00:42:44,480 --> 00:42:49,519
together and and start designing Power

993
00:42:46,920 --> 00:42:52,200
Electronics of your own and you will for

994
00:42:49,519 --> 00:42:57,960
the final project

995
00:42:52,199 --> 00:42:57,960
okay so any final questions

996
00:42:59,239 --> 00:43:04,719
okay we'll wrap up today and I will see

997
00:43:01,039 --> 00:43:04,719
everybody on Wednesday