WEBVTT

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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

00:08:06.038 --> 00:08:09.918
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

00:09:03.839 --> 00:09:09.279
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

00:09:11.559 --> 00:09:15.958
like that today but with the techniques

00:09:14.799 --> 00:09:17.639
you're going to learn in this course you

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could actually go back and analyze this

00:09:17.639 --> 00:09:21.278
thing and figure out what it did right

00:09:19.519 --> 00:09:24.240
so some foundational ideas that we're

00:09:21.278 --> 00:09:26.559
going to come back to which can be 100

00:09:24.240 --> 00:09:29.519
years old but there's also elements that

00:09:26.559 --> 00:09:32.879
are extremely new okay and today you

00:09:29.519 --> 00:09:35.200
know this this was fancy 100 years ago

00:09:32.879 --> 00:09:38.120
today Power Electronics is everywhere

00:09:35.200 --> 00:09:39.720
from I say from mowatt to gigawatts and

00:09:38.120 --> 00:09:41.159
and it does actually use switch mode

00:09:39.720 --> 00:09:43.320
power conversion down at those power

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levels this is actually a a multi-watt

00:09:43.320 --> 00:09:48.600
power supply and this is literally at

00:09:45.159 --> 00:09:50.919
the gigawatt scale so if you if you go

00:09:48.600 --> 00:09:53.120
out to S the Sandy Pond terminal there

00:09:50.919 --> 00:09:55.199
is a power converter that takes two gws

00:09:53.120 --> 00:09:58.159
coming down from Canada hydro and

00:09:55.200 --> 00:10:00.278
converts it to AC to power homes and

00:09:58.159 --> 00:10:01.919
everything else around here right so and

00:10:00.278 --> 00:10:05.480
the techniques that we're going to learn

00:10:01.919 --> 00:10:06.958
in this class really span the entire

00:10:05.480 --> 00:10:08.759
range right so some of the details

00:10:06.958 --> 00:10:10.879
change and we'll learn about that but

00:10:08.759 --> 00:10:12.799
there's underlying principles that that

00:10:10.879 --> 00:10:16.000
cut across all kinds of electrical

00:10:12.799 --> 00:10:18.078
energy conversion systems

00:10:16.000 --> 00:10:20.078
okay what kind of applications well

00:10:18.078 --> 00:10:23.399
portable Electronics this slightly older

00:10:20.078 --> 00:10:25.399
an iPhone 5 and you think okay iPhones

00:10:23.399 --> 00:10:27.440
got radio transmitters and displays and

00:10:25.399 --> 00:10:30.159
other stuff in it but it turns out that

00:10:27.440 --> 00:10:33.040
a large fraction of the volume and board

00:10:30.159 --> 00:10:34.319
area is actually associated with energy

00:10:33.039 --> 00:10:35.199
conversion in the thing because no

00:10:34.320 --> 00:10:37.160
matter what you're doing you're

00:10:35.200 --> 00:10:39.839
processing energy to process information

00:10:37.159 --> 00:10:41.719
right so something like 40% in this of

00:10:39.839 --> 00:10:43.200
the motherboard in this example was

00:10:41.720 --> 00:10:45.399
associated with power

00:10:43.200 --> 00:10:47.480
conversion likewise you know at some

00:10:45.399 --> 00:10:49.839
point you're going to charge your phone

00:10:47.480 --> 00:10:52.680
or your or your iPad or your computer

00:10:49.839 --> 00:10:54.519
into the wall that's mostly Power

00:10:52.679 --> 00:10:56.638
Electronics too all kinds of computers

00:10:54.519 --> 00:10:58.320
if you're in a data center there's

00:10:56.639 --> 00:11:01.200
several layers of power conversion

00:10:58.320 --> 00:11:02.160
between the AC group GD and the final

00:11:01.200 --> 00:11:05.519
set of

00:11:02.159 --> 00:11:07.958
processors okay this is more of what it

00:11:05.519 --> 00:11:10.480
looks like inside your home computer

00:11:07.958 --> 00:11:12.199
we'll actually learn exactly about those

00:11:10.480 --> 00:11:14.759
kind of converters and about all the

00:11:12.200 --> 00:11:16.920
components that are in them if you're

00:11:14.759 --> 00:11:19.360
going to communicate right the

00:11:16.919 --> 00:11:21.199
transmitters we tend to think of this as

00:11:19.360 --> 00:11:22.919
analog circuits to to make RF

00:11:21.200 --> 00:11:25.800
transmitters but in fact Power

00:11:22.919 --> 00:11:27.958
Electronics are heavily embedded in any

00:11:25.799 --> 00:11:31.199
real communication systems to increase

00:11:27.958 --> 00:11:33.078
the efficiency of transmission

00:11:31.200 --> 00:11:35.120
all kinds of commercial applications

00:11:33.078 --> 00:11:38.039
whether you're you know doing LED

00:11:35.120 --> 00:11:39.919
lighting or this is actually from some

00:11:38.039 --> 00:11:42.759
water

00:11:39.919 --> 00:11:45.240
Purity device but of course it requires

00:11:42.759 --> 00:11:48.799
a power supply right

00:11:45.240 --> 00:11:50.278
so almost any use of energy these days

00:11:48.799 --> 00:11:52.838
requires a power

00:11:50.278 --> 00:11:54.919
supply even in your home I mentioned

00:11:52.839 --> 00:11:56.880
that it used to be that you'd connect

00:11:54.919 --> 00:11:58.120
Motors up to the grid and they'd run and

00:11:56.879 --> 00:11:59.958
maybe You' turn them on and off

00:11:58.120 --> 00:12:02.120
something like that but no longer right

00:11:59.958 --> 00:12:04.838
if you want high performance you need to

00:12:02.120 --> 00:12:07.879
be able to modulate that energy so two

00:12:04.839 --> 00:12:10.279
examples here this is for an air

00:12:07.879 --> 00:12:12.720
conditioning unit and it uses an

00:12:10.278 --> 00:12:15.320
inverter a DC to AC converter inside it

00:12:12.720 --> 00:12:17.320
to drive the motor much more quietly and

00:12:15.320 --> 00:12:20.560
much more modulated for higher overall

00:12:17.320 --> 00:12:23.000
system efficiency even your dishwasher

00:12:20.559 --> 00:12:25.638
these days has power converters in it

00:12:23.000 --> 00:12:30.559
because it's more efficient in this case

00:12:25.639 --> 00:12:33.079
quieter to do it that way okay IDE is

00:12:30.559 --> 00:12:35.919
that you might not think of as power

00:12:33.078 --> 00:12:39.078
converters medical applications this is

00:12:35.919 --> 00:12:41.838
this is actually a uh magnetic

00:12:39.078 --> 00:12:43.879
stimulator generates 5,000 amps pulse

00:12:41.839 --> 00:12:46.480
trains in a transducer coil to throw up

00:12:43.879 --> 00:12:47.919
magnetic fields that can trigger nerves

00:12:46.480 --> 00:12:49.199
this is an interesting one it's actually

00:12:47.919 --> 00:12:51.039
homework zero so the thing you're

00:12:49.198 --> 00:12:53.479
analyzing in the first homework just to

00:12:51.039 --> 00:12:57.480
break the rust off is actually this box

00:12:53.480 --> 00:12:59.680
right here okay scientific applications

00:12:57.480 --> 00:13:01.519
you may not be processing energy but

00:12:59.679 --> 00:13:03.239
even if you just need to generate

00:13:01.519 --> 00:13:05.839
electric High electrical fields for

00:13:03.240 --> 00:13:07.680
whatever reason or magnetic fields as in

00:13:05.839 --> 00:13:10.079
the magnetic stimulator you need energy

00:13:07.679 --> 00:13:12.278
conversion circuits to do it then

00:13:10.078 --> 00:13:14.000
there's the sort of the more maybe the

00:13:12.278 --> 00:13:17.039
applications you might think of

00:13:14.000 --> 00:13:19.759
Transportation right let say that

00:13:17.039 --> 00:13:21.000
electric vehicle or a hybrid vehicle

00:13:19.759 --> 00:13:23.319
right you

00:13:21.000 --> 00:13:24.600
need Power Electronics to drive the

00:13:23.320 --> 00:13:25.839
energy conversion and this is not a

00:13:24.600 --> 00:13:28.759
small thing first of all you need the

00:13:25.839 --> 00:13:31.959
Power Electronics to drive these things

00:13:28.759 --> 00:13:34.759
right secondly in fact as in one

00:13:31.958 --> 00:13:37.439
example they redes they

00:13:34.759 --> 00:13:40.879
redesigned the power converter for a

00:13:37.440 --> 00:13:43.440
Prius the the power train for the Prius

00:13:40.879 --> 00:13:45.159
the fuel economy went up by 5% just by

00:13:43.440 --> 00:13:48.760
redesigning the Power Electronics to be

00:13:45.159 --> 00:13:52.159
better so it has a huge impact on the

00:13:48.759 --> 00:13:56.439
overall application and of course that's

00:13:52.159 --> 00:13:58.759
um electric vehicles but traction right

00:13:56.440 --> 00:13:59.639
trains that's higher power but the same

00:13:58.759 --> 00:14:01.399
issue

00:13:59.639 --> 00:14:03.000
actually even future trains this it's a

00:14:01.399 --> 00:14:05.799
little hard to see behind this railing

00:14:03.000 --> 00:14:08.600
that's a maglev magnetically levitated

00:14:05.799 --> 00:14:10.319
train along the Wayside over in the back

00:14:08.600 --> 00:14:12.480
corner you see this big building here

00:14:10.320 --> 00:14:14.800
inside that big building as these racks

00:14:12.480 --> 00:14:16.720
of Power Electronics now you better have

00:14:14.799 --> 00:14:19.240
pretty reliable Power Electronics if

00:14:16.720 --> 00:14:20.879
your vehicle's flying along at 400 kmers

00:14:19.240 --> 00:14:23.799
an hour floating on you know that far

00:14:20.879 --> 00:14:26.039
off the ground right so not only do you

00:14:23.799 --> 00:14:29.639
need efficiency but you need reliability

00:14:26.039 --> 00:14:32.838
and precision okay even Strang

00:14:29.639 --> 00:14:37.079
things uh this is this is an example of

00:14:32.839 --> 00:14:38.639
a drone just by powered by high voltage

00:14:37.078 --> 00:14:41.838
right you just apply high voltage it

00:14:38.639 --> 00:14:43.399
breaks down the air accelerates ions and

00:14:41.839 --> 00:14:45.000
you can use that for propulsion that's

00:14:43.399 --> 00:14:47.519
the first demonstration of it but it

00:14:45.000 --> 00:14:49.198
actually it's very similar in some

00:14:47.519 --> 00:14:51.000
regards to what people use for space

00:14:49.198 --> 00:14:54.120
propulsion you've heard of ion engines

00:14:51.000 --> 00:14:57.159
right the twin ion engine TIE fighter or

00:14:54.120 --> 00:14:59.399
what more practically they use to uh to

00:14:57.159 --> 00:15:00.879
reposition satellites those require

00:14:59.399 --> 00:15:05.120
Power Electronics to generate high

00:15:00.879 --> 00:15:08.799
voltages and accelerate ions okay Power

00:15:05.120 --> 00:15:10.039
transmission and generation right that's

00:15:08.799 --> 00:15:11.479
so you're getting your energy from

00:15:10.039 --> 00:15:13.439
somewhere and increasingly we're getting

00:15:11.480 --> 00:15:16.199
it from renewable resources well

00:15:13.440 --> 00:15:19.680
generally the way things are trending

00:15:16.198 --> 00:15:21.799
you take some mechanical or solar or

00:15:19.679 --> 00:15:24.039
other source of energy and you

00:15:21.799 --> 00:15:25.838
transition it not only through a

00:15:24.039 --> 00:15:27.480
generator but through Power Electronics

00:15:25.839 --> 00:15:30.240
to get there and that's true for

00:15:27.480 --> 00:15:33.560
terrestrial things things like this is a

00:15:30.240 --> 00:15:35.318
house rooftop PV system this is a micro

00:15:33.559 --> 00:15:36.838
inverter

00:15:35.318 --> 00:15:39.919
um

00:15:36.839 --> 00:15:42.519
Automotive Systems or even much smaller

00:15:39.919 --> 00:15:45.439
things like uh

00:15:42.519 --> 00:15:48.278
uh Power harvesting energy harvesting

00:15:45.440 --> 00:15:50.759
techniques you need Power Electronics in

00:15:48.278 --> 00:15:53.399
it also all kinds of industrial

00:15:50.759 --> 00:15:56.000
applications whether you're doing uh

00:15:53.399 --> 00:15:58.480
plasma processing for Semiconductor

00:15:56.000 --> 00:16:02.120
processing or you know you want to

00:15:58.480 --> 00:16:04.600
refine metals like a DC Arc furnace you

00:16:02.120 --> 00:16:06.519
need Power Electronics there too okay so

00:16:04.600 --> 00:16:09.360
that's just sort of a way long way of

00:16:06.519 --> 00:16:11.919
saying power electronics are in almost

00:16:09.360 --> 00:16:13.839
everything you care about these days and

00:16:11.919 --> 00:16:15.838
it's only getting more so because we

00:16:13.839 --> 00:16:18.839
have to be better about how we use

00:16:15.839 --> 00:16:18.839
energy

00:16:19.039 --> 00:16:23.879
okay so what's inside a power converter

00:16:22.078 --> 00:16:26.239
and we're going to talk about this in

00:16:23.879 --> 00:16:30.519
much greater detail but if you want to

00:16:26.240 --> 00:16:33.600
think about it what we have

00:16:30.519 --> 00:16:35.600
is typically some kind of energy storage

00:16:33.600 --> 00:16:38.560
elements these could be inductors or

00:16:35.600 --> 00:16:40.519
capacitors or sometimes other things and

00:16:38.559 --> 00:16:42.239
what we're going to do is we're going to

00:16:40.519 --> 00:16:44.959
use semiconductor switches and we're

00:16:42.240 --> 00:16:46.639
going to draw energy from some Source

00:16:44.958 --> 00:16:48.198
we're going to manipulate it somehow so

00:16:46.639 --> 00:16:49.120
we store it in these energy storage

00:16:48.198 --> 00:16:51.758
elements and then we're going to put it

00:16:49.120 --> 00:16:55.399
to the output and we're going to repeat

00:16:51.759 --> 00:16:58.360
that right so draw transform put it to

00:16:55.399 --> 00:16:59.399
the output okay because we do this on a

00:16:58.360 --> 00:17:02.399
cyclic

00:16:59.399 --> 00:17:04.078
basis we generate sort of Ripple and

00:17:02.399 --> 00:17:05.359
potentially noise that could interfere

00:17:04.078 --> 00:17:08.000
with things like television or

00:17:05.359 --> 00:17:11.318
Electronics so you generally need

00:17:08.000 --> 00:17:13.400
filters to do that too we also of course

00:17:11.318 --> 00:17:15.240
need to control that flow of energy

00:17:13.400 --> 00:17:16.759
right we can't be stupid about it we

00:17:15.240 --> 00:17:18.318
have especially for something high

00:17:16.759 --> 00:17:21.720
performance like a microprocessor which

00:17:18.318 --> 00:17:24.599
might be changing its operation very

00:17:21.720 --> 00:17:26.120
very fast we need to control that flow

00:17:24.599 --> 00:17:27.958
so there's control circuitry we're going

00:17:26.119 --> 00:17:29.558
to be learning about all of the aspects

00:17:27.959 --> 00:17:34.360
of Designing

00:17:29.558 --> 00:17:36.079
all of these kinds of elements

00:17:34.359 --> 00:17:38.678
okay

00:17:36.079 --> 00:17:41.199
so we're leveraging sort of everything

00:17:38.679 --> 00:17:43.919
from circuit design semiconductor

00:17:41.200 --> 00:17:46.880
devices passive components and materials

00:17:43.919 --> 00:17:49.840
increasingly packaging and Cooling and

00:17:46.880 --> 00:17:51.039
controls also matter and things have

00:17:49.839 --> 00:17:55.319
been getting better and better and

00:17:51.038 --> 00:17:57.279
better both because the um ways we can

00:17:55.319 --> 00:18:00.279
manufacture things get better and

00:17:57.279 --> 00:18:03.319
because the devices which we have

00:18:00.279 --> 00:18:05.200
our access to in order to implement

00:18:03.319 --> 00:18:06.720
these things get better okay and so

00:18:05.200 --> 00:18:09.480
we're going to look at some of the

00:18:06.720 --> 00:18:11.798
different ways you can do that I'll just

00:18:09.480 --> 00:18:14.599
give you

00:18:11.798 --> 00:18:16.440
uh one example this is what you would

00:18:14.599 --> 00:18:18.359
find something like in a data center

00:18:16.440 --> 00:18:21.480
right so they come in they rectify the

00:18:18.359 --> 00:18:24.279
voltage they get it to sort of 400 Volts

00:18:21.480 --> 00:18:26.200
for reasons we'll go into this converter

00:18:24.279 --> 00:18:29.279
here was designed to take that 400 volts

00:18:26.200 --> 00:18:31.038
and bring it down to 12 volts okay

00:18:29.279 --> 00:18:32.599
that that tiny little thing a little bit

00:18:31.038 --> 00:18:35.119
bigger than a penny there actually can

00:18:32.599 --> 00:18:36.918
handle a kilowatt then you need more

00:18:35.119 --> 00:18:42.158
converters to take it down from there to

00:18:36.919 --> 00:18:45.320
the one VT that the processor uses okay

00:18:42.159 --> 00:18:48.120
so the sort of a long way of saying all

00:18:45.319 --> 00:18:49.960
kinds of things are limited by energy

00:18:48.119 --> 00:18:52.119
and how we can control it right across

00:18:49.960 --> 00:18:53.759
all these applications and what we're

00:18:52.119 --> 00:18:55.759
usually trying to do is how figure out

00:18:53.759 --> 00:18:57.440
how to make them smaller and lighter

00:18:55.759 --> 00:18:59.359
right if you're taking up 40% of your

00:18:57.440 --> 00:19:00.798
iPhone you want

00:18:59.359 --> 00:19:02.918
make that thing smaller so it doesn't

00:19:00.798 --> 00:19:04.679
take that up and you can replace that

00:19:02.919 --> 00:19:06.799
volume either with nothing or with

00:19:04.679 --> 00:19:08.519
things that are more interesting to you

00:19:06.798 --> 00:19:10.000
we need higher efficiency both for the

00:19:08.519 --> 00:19:12.359
converters and the systems how we

00:19:10.000 --> 00:19:14.038
process energy can matter to the not

00:19:12.359 --> 00:19:15.439
only the ultimate efficiency of the

00:19:14.038 --> 00:19:17.519
converter but the efficiency of the

00:19:15.440 --> 00:19:19.759
system how it uses energy can be

00:19:17.519 --> 00:19:21.879
determined by the Power Electronics we

00:19:19.759 --> 00:19:25.640
want higher performance that could mean

00:19:21.880 --> 00:19:28.720
higher bandwidth or other aspects and

00:19:25.640 --> 00:19:31.038
then there's all kinds of means that we

00:19:28.720 --> 00:19:33.440
we can use better electrical processing

00:19:31.038 --> 00:19:35.480
to enable new applications so these are

00:19:33.440 --> 00:19:38.679
the kind of things that we're going to

00:19:35.480 --> 00:19:39.919
learn about this term I'll pause there

00:19:38.679 --> 00:19:41.519
i' I've been going on a while are there

00:19:39.919 --> 00:19:43.038
any questions about any of this before

00:19:41.519 --> 00:19:44.240
we get going this is just to sort of

00:19:43.038 --> 00:19:47.038
Orient you as to what we're going to

00:19:44.240 --> 00:19:47.038
focus the term

00:19:49.440 --> 00:19:56.519
on I can put the slides on canvas

00:19:53.079 --> 00:19:56.519
sure any other

00:19:57.440 --> 00:20:00.640
questions okay

00:20:01.319 --> 00:20:07.558
okay I will just give

00:20:05.200 --> 00:20:11.440
you a slight

00:20:07.558 --> 00:20:13.558
notion okay just and this is a

00:20:11.440 --> 00:20:16.279
favorite thing I like to bring in just

00:20:13.558 --> 00:20:17.720
to show you the kind of things we're

00:20:16.279 --> 00:20:20.558
going to look at this

00:20:17.720 --> 00:20:22.240
term this is a piece of commercial

00:20:20.558 --> 00:20:23.440
Hardware from a company called MKS

00:20:22.240 --> 00:20:24.519
instruments that I just happen to have

00:20:23.440 --> 00:20:27.600
in my

00:20:24.519 --> 00:20:29.000
office this input piece is a filter so

00:20:27.599 --> 00:20:30.399
you don't create electrom magnetic

00:20:29.000 --> 00:20:31.960
interference and you don't generate

00:20:30.400 --> 00:20:35.679
noise you don't

00:20:31.960 --> 00:20:37.880
want then this piece here takes energy

00:20:35.679 --> 00:20:40.798
from the 60 HZ grid and generates DC

00:20:37.880 --> 00:20:42.320
from it and it has to do it while making

00:20:40.798 --> 00:20:44.879
the whole thing look like a resistor to

00:20:42.319 --> 00:20:46.798
the grid so you don't mess up the grid

00:20:44.880 --> 00:20:49.039
okay that's what this part does then it

00:20:46.798 --> 00:20:51.359
has these isolated dcdc converters that

00:20:49.038 --> 00:20:54.319
can take that DC voltage and generate

00:20:51.359 --> 00:20:58.399
other DC voltages referenced in other

00:20:54.319 --> 00:21:00.798
ways and without worrying about uh sort

00:20:58.400 --> 00:21:04.280
of currents going back to ground okay

00:21:00.798 --> 00:21:07.319
it's galvanically isolated and then it

00:21:04.279 --> 00:21:09.240
takes that energy and goes back DC to AC

00:21:07.319 --> 00:21:11.720
okay now in some systems you might go DC

00:21:09.240 --> 00:21:13.159
to AC for 60 hertz to to generate into

00:21:11.720 --> 00:21:15.400
the Grid or for a motor or something

00:21:13.159 --> 00:21:17.480
else this particular one has these

00:21:15.400 --> 00:21:20.640
outputs that are at 13 megahertz for

00:21:17.480 --> 00:21:22.960
driving plasmas to process

00:21:20.640 --> 00:21:25.600
semiconductors okay but you get all

00:21:22.960 --> 00:21:28.159
these kind of functions AC to DC DC to

00:21:25.599 --> 00:21:29.719
DC DC to AC and we're going to learn the

00:21:28.159 --> 00:21:31.919
first of all the

00:21:29.720 --> 00:21:34.798
underlying uh principles of doing all

00:21:31.919 --> 00:21:38.360
these things and how to design them okay

00:21:34.798 --> 00:21:41.038
so the the the real goal

00:21:38.359 --> 00:21:43.678
is by the time you walk out of here you

00:21:41.038 --> 00:21:44.919
should have all the tools to go off and

00:21:43.679 --> 00:21:47.640
design Power

00:21:44.919 --> 00:21:49.759
Electronics for all kinds of

00:21:47.640 --> 00:21:50.720
applications and and in fact graduates

00:21:49.759 --> 00:21:53.679
of this

00:21:50.720 --> 00:21:55.440
class have worked on electric vehicles

00:21:53.679 --> 00:21:57.000
Char battery charger

00:21:55.440 --> 00:21:59.440
solar

00:21:57.000 --> 00:22:01.319
uh communication

00:21:59.440 --> 00:22:04.320
systems data

00:22:01.319 --> 00:22:06.678
centers the in fact the the power supply

00:22:04.319 --> 00:22:08.200
I usually use for my laptop and the in

00:22:06.679 --> 00:22:11.000
fact the wireless charger for my

00:22:08.200 --> 00:22:13.319
eyewatch were all designed or the teams

00:22:11.000 --> 00:22:15.119
were led by graduates of this class

00:22:13.319 --> 00:22:18.678
right so this the goal is to give you

00:22:15.119 --> 00:22:21.519
the tools you need to go do these things

00:22:18.679 --> 00:22:25.200
okay so with

00:22:21.519 --> 00:22:29.639
that um let me

00:22:25.200 --> 00:22:31.600
start by just giving you a sense

00:22:29.640 --> 00:22:36.240
of

00:22:31.599 --> 00:22:36.240
um what goes on inside Power

00:22:40.558 --> 00:22:46.798
Electronics so let's think of the

00:22:43.720 --> 00:22:49.640
simplest case I have some DC input

00:22:46.798 --> 00:22:54.158
voltage and I'd like some other DC

00:22:49.640 --> 00:22:54.159
voltage so suppose I have some

00:22:54.319 --> 00:22:59.639
input that's you know maybe it's 9 volts

00:22:58.079 --> 00:23:02.639
to 6 16

00:22:59.640 --> 00:23:04.200
Vols I'm making that up arbitrarily but

00:23:02.640 --> 00:23:06.880
that's roughly what you might get in a

00:23:04.200 --> 00:23:09.240
typical vehicle right out of the

00:23:06.880 --> 00:23:11.799
cigarette lighter

00:23:09.240 --> 00:23:13.759
okay and suppose I want and I'll call

00:23:11.798 --> 00:23:16.798
this

00:23:13.759 --> 00:23:18.119
VN and suppose I want here's some load

00:23:16.798 --> 00:23:21.079
that I'm going to represent with a

00:23:18.119 --> 00:23:25.199
resistor I'm going to call that V out

00:23:21.079 --> 00:23:27.278
okay and suppose I want EG 5

00:23:25.200 --> 00:23:29.720
volts right to power something that

00:23:27.278 --> 00:23:33.359
takes five volts

00:23:29.720 --> 00:23:36.600
right what's the most obvious and simple

00:23:33.359 --> 00:23:39.199
way to get 5 volts at my output from

00:23:36.599 --> 00:23:39.199
some higher

00:23:41.679 --> 00:23:47.919
voltage voltage divider precisely right

00:23:44.960 --> 00:23:50.480
I could come up here I could say okay

00:23:47.919 --> 00:23:50.480
let me put

00:23:50.558 --> 00:23:56.519
in some volt variable

00:23:53.519 --> 00:23:58.839
resistor and I'll drop down this voltage

00:23:56.519 --> 00:24:02.200
to give me the voltage I want and I'm

00:23:58.839 --> 00:24:03.798
done and in fact a lot of systems that's

00:24:02.200 --> 00:24:07.798
exactly more or less what they have

00:24:03.798 --> 00:24:09.400
inside them in fact inside most

00:24:07.798 --> 00:24:12.599
integrated circuits there's lots of

00:24:09.400 --> 00:24:14.320
these things going on okay well okay

00:24:12.599 --> 00:24:18.079
they don't do it quite this way what do

00:24:14.319 --> 00:24:18.079
they really do

00:24:18.599 --> 00:24:24.158
they will take VN and what they will do

00:24:21.960 --> 00:24:26.679
is they'll use some kind of transistor a

00:24:24.159 --> 00:24:31.240
mosfet or a bipolar

00:24:26.679 --> 00:24:34.000
transistor and they will treat that

00:24:31.240 --> 00:24:35.679
essentially as a variable resistor right

00:24:34.000 --> 00:24:38.200
so I implement the variable resistor

00:24:35.679 --> 00:24:40.679
with a controlled transistor and I will

00:24:38.200 --> 00:24:43.278
come and I'll have some feedback loop

00:24:40.679 --> 00:24:45.600
I'll Fe feed in a reference

00:24:43.278 --> 00:24:47.880
voltage and I'll measure the output

00:24:45.599 --> 00:24:49.918
voltage and I'll control the Gate of

00:24:47.880 --> 00:24:51.640
this transistor and essentially make

00:24:49.919 --> 00:24:53.640
that transistor look like a variable

00:24:51.640 --> 00:24:55.960
resistor and control the voltage

00:24:53.640 --> 00:24:58.038
division so that even if this voltage

00:24:55.960 --> 00:25:01.278
varies between 9 and 16 volts I always

00:24:58.038 --> 00:25:05.158
get my 5 Vols output

00:25:01.278 --> 00:25:07.398
Okay and like I said that's very

00:25:05.159 --> 00:25:08.720
common but what's the problem with this

00:25:07.398 --> 00:25:10.519
well there's a whole lot of problems

00:25:08.720 --> 00:25:13.839
with this right why why wouldn't you

00:25:10.519 --> 00:25:15.960
want to do this uh

00:25:13.839 --> 00:25:19.079
in typical

00:25:15.960 --> 00:25:20.840
operation efficiency terrible efficiency

00:25:19.079 --> 00:25:25.599
yes

00:25:20.839 --> 00:25:27.798
exactly so let's think about this if I

00:25:25.599 --> 00:25:30.319
accept the fact let me call this current

00:25:27.798 --> 00:25:30.319
I in

00:25:33.798 --> 00:25:38.839
okay and this current I

00:25:37.278 --> 00:25:42.240
out

00:25:38.839 --> 00:25:45.158
okay if this thing does act exactly like

00:25:42.240 --> 00:25:47.240
a variable resistor the input currents

00:25:45.159 --> 00:25:49.080
equal to the output current now this

00:25:47.240 --> 00:25:50.440
actually a real system might have some

00:25:49.079 --> 00:25:52.678
current that actually also goes to

00:25:50.440 --> 00:25:54.278
ground let's take the best case where

00:25:52.679 --> 00:25:56.559
the output current is equal to the input

00:25:54.278 --> 00:26:00.798
current okay what would be the

00:25:56.558 --> 00:26:00.798
efficiency of this Beast well the

00:26:05.679 --> 00:26:11.480
efficiency the efficiency is equal to

00:26:07.798 --> 00:26:13.839
the output power over the input power

00:26:11.480 --> 00:26:15.919
right I'm drawing energy maybe from my

00:26:13.839 --> 00:26:17.359
car battery or whatever my battery

00:26:15.919 --> 00:26:19.640
source is and I'm delivering it to the

00:26:17.359 --> 00:26:23.158
output but not all of it's getting to

00:26:19.640 --> 00:26:24.919
the output so the output power is V out

00:26:23.159 --> 00:26:30.278
time I

00:26:24.919 --> 00:26:33.000
out and my input power is VN time I in

00:26:30.278 --> 00:26:36.079
and I just told you that I out was equal

00:26:33.000 --> 00:26:37.640
to I in in the best case so that's V out

00:26:36.079 --> 00:26:41.240
over

00:26:37.640 --> 00:26:44.399
VN right so if I'm coming in from 15

00:26:41.240 --> 00:26:47.440
volts and I'm getting five

00:26:44.398 --> 00:26:50.719
volts that's 33% efficiency right I've

00:26:47.440 --> 00:26:52.240
taken 2/3 of my energy and thrown it

00:26:50.720 --> 00:26:54.839
away

00:26:52.240 --> 00:26:58.000
now if I got lots of energy floating

00:26:54.839 --> 00:26:59.359
around and I'm processing a microwatt

00:26:58.000 --> 00:27:01.079
maybe maybe I don't care maybe I'll live

00:26:59.359 --> 00:27:03.240
with that because this thing's pretty

00:27:01.079 --> 00:27:05.038
simple right it's a transistor it's a

00:27:03.240 --> 00:27:06.839
power transistor and some controls and

00:27:05.038 --> 00:27:09.000
they can often put all that on one

00:27:06.839 --> 00:27:11.398
integrated circuit or even as a subblock

00:27:09.000 --> 00:27:13.038
on an integrated circuit I might still

00:27:11.398 --> 00:27:17.278
need some filtering it's not it's not

00:27:13.038 --> 00:27:21.119
quite as easy as it sounds but um pretty

00:27:17.278 --> 00:27:23.038
much it's relatively simple but my

00:27:21.119 --> 00:27:24.678
efficiency is miserable now if I thought

00:27:23.038 --> 00:27:27.640
about in your in your

00:27:24.679 --> 00:27:29.759
computer right your desktop computer

00:27:27.640 --> 00:27:31.919
typically the intermediate Supply that

00:27:29.759 --> 00:27:33.278
you're getting after it's sort of come

00:27:31.919 --> 00:27:35.840
in from the grid and been transformed

00:27:33.278 --> 00:27:37.798
down you get 12 volts right and let's

00:27:35.839 --> 00:27:40.720
say your computer is it sort of it

00:27:37.798 --> 00:27:42.398
depends on what it's doing but say it's

00:27:40.720 --> 00:27:45.720
operating at a volt right so then you're

00:27:42.398 --> 00:27:47.479
less than 10% efficient right and if you

00:27:45.720 --> 00:27:49.759
think that you know you can have a

00:27:47.480 --> 00:27:53.440
microprocessor that's taking 200 amps at

00:27:49.759 --> 00:27:55.798
a volt or few hundred Watts suddenly if

00:27:53.440 --> 00:27:58.200
I've got less than 10% efficiency on 200

00:27:55.798 --> 00:27:59.639
Watts that means I need to put in a few

00:27:58.200 --> 00:28:01.278
kilowatts well you can't even plug that

00:27:59.640 --> 00:28:03.038
into the wall never mind the fact you've

00:28:01.278 --> 00:28:06.240
just made a massive room heater right

00:28:03.038 --> 00:28:10.119
that's that's like that'd be great for

00:28:06.240 --> 00:28:13.599
heating your dorm room um but pretty

00:28:10.119 --> 00:28:17.439
terrible for the overall system okay so

00:28:13.599 --> 00:28:19.319
the number one reason we don't like this

00:28:17.440 --> 00:28:21.519
solution is

00:28:19.319 --> 00:28:24.359
efficiency good thing it's simple bad

00:28:21.519 --> 00:28:28.240
thing it's terrible efficiency this

00:28:24.359 --> 00:28:28.240
technique I should have noted

00:28:28.278 --> 00:28:33.519
is what's known for historical reasons

00:28:30.558 --> 00:28:35.798
as a quote unquote

00:28:33.519 --> 00:28:40.159
linear power

00:28:35.798 --> 00:28:43.519
supply why linear I think only because

00:28:40.159 --> 00:28:45.200
analog circuits kind of a category of

00:28:43.519 --> 00:28:47.120
them became known as quote unquote

00:28:45.200 --> 00:28:49.080
linear circuits there's nothing really

00:28:47.119 --> 00:28:51.839
that linear about it but this would be

00:28:49.079 --> 00:28:54.720
called a linear power converter or or

00:28:51.839 --> 00:28:56.678
some sometimes a linear regulator is

00:28:54.720 --> 00:28:59.399
what it would be called

00:28:56.679 --> 00:29:01.360
okay for obvious reasons I hate throwing

00:28:59.398 --> 00:29:03.000
away energy we're not going to talk

00:29:01.359 --> 00:29:04.639
about linear Regulators at all in this

00:29:03.000 --> 00:29:06.359
class and there's plenty of classes

00:29:04.640 --> 00:29:09.679
where you can learn about that we want

00:29:06.359 --> 00:29:13.479
to do things some better way that's not

00:29:09.679 --> 00:29:18.159
going to burn lots of energy okay so

00:29:13.480 --> 00:29:22.079
ideally you know in my world the goal is

00:29:18.159 --> 00:29:24.519
to take as much of the input energy in

00:29:22.079 --> 00:29:26.319
and put it to the output right and

00:29:24.519 --> 00:29:29.038
that's important because think about it

00:29:26.319 --> 00:29:31.319
this way I I showed you a photo graph of

00:29:29.038 --> 00:29:35.319
something that was you know really tiny

00:29:31.319 --> 00:29:38.200
maybe that big right and that thick and

00:29:35.319 --> 00:29:40.038
was processing a kilowatt right if I

00:29:38.200 --> 00:29:42.679
don't do that at really high efficiency

00:29:40.038 --> 00:29:45.319
that thing will burn up right so in

00:29:42.679 --> 00:29:48.399
order to make something small I need to

00:29:45.319 --> 00:29:50.398
make it efficient all right so we want

00:29:48.398 --> 00:29:52.798
almost all of the energy at the input to

00:29:50.398 --> 00:29:55.079
get to the output well how can we do

00:29:52.798 --> 00:29:57.798
that let's think of a completely

00:29:55.079 --> 00:30:00.918
different way we might achieve this same

00:29:57.798 --> 00:30:03.759
function function all right and here's

00:30:00.919 --> 00:30:03.759
the idea here's my

00:30:09.000 --> 00:30:15.240
input I'm going to create a switch here

00:30:12.720 --> 00:30:16.440
single pole double throw switch now

00:30:15.240 --> 00:30:17.679
we're not going to go get physical

00:30:16.440 --> 00:30:19.360
switches we're probably going to get

00:30:17.679 --> 00:30:22.320
semiconductor devices and make it do

00:30:19.359 --> 00:30:24.278
something like this but we could use

00:30:22.319 --> 00:30:27.599
anything any technology that was

00:30:24.278 --> 00:30:29.759
practical as a switch okay and let me

00:30:27.599 --> 00:30:30.959
just Define if I'm going to define a

00:30:29.759 --> 00:30:33.879
switching function that I'm going to

00:30:30.960 --> 00:30:37.880
call Q of T if Q of T is

00:30:33.880 --> 00:30:40.760
one I'll connect the switch to the input

00:30:37.880 --> 00:30:40.760
if Q of T is

00:30:41.159 --> 00:30:47.559
zero I'll connect the switch to the

00:30:43.798 --> 00:30:52.038
ground okay so this notion this voltage

00:30:47.558 --> 00:30:52.038
okay maybe I'll call this voltage

00:30:54.079 --> 00:30:59.879
VX all right so one thing I could do is

00:30:57.440 --> 00:31:02.880
I could say okay let me just hook this

00:30:59.880 --> 00:31:06.559
up to my load here's my resistive

00:31:02.880 --> 00:31:10.240
load whatever it is and I'll call this V

00:31:06.558 --> 00:31:12.798
out all right well all right what would

00:31:10.240 --> 00:31:15.319
that look like well let me Define my

00:31:12.798 --> 00:31:15.319
switching

00:31:22.159 --> 00:31:28.120
function I'm going to put the switch in

00:31:25.119 --> 00:31:29.879
the up position for a little while then

00:31:28.119 --> 00:31:31.759
I'll put it in the down

00:31:29.880 --> 00:31:33.679
position by setting the switching

00:31:31.759 --> 00:31:35.158
function to zero and then I'll just

00:31:33.679 --> 00:31:36.720
repeat that so I said we're going to

00:31:35.159 --> 00:31:39.399
operate in some kind of repetitive

00:31:36.720 --> 00:31:43.480
fashion here and so

00:31:39.398 --> 00:31:46.038
forth let me operate with some period

00:31:43.480 --> 00:31:47.399
T okay that's mean my switching period

00:31:46.038 --> 00:31:50.440
in this example I'm showing you is a

00:31:47.398 --> 00:31:52.959
fixed switching period okay and I will

00:31:50.440 --> 00:31:56.120
keep the switch in the up position some

00:31:52.960 --> 00:31:59.000
fraction of the time that I'll call DT

00:31:56.119 --> 00:32:01.518
so D is a fraction zero is less than D

00:31:59.000 --> 00:32:01.519
is less than

00:32:01.880 --> 00:32:07.200
one

00:32:03.599 --> 00:32:09.439
okay so if I do that then what do I get

00:32:07.200 --> 00:32:11.278
for VX VX is going to look something

00:32:09.440 --> 00:32:15.519
like

00:32:11.278 --> 00:32:19.319
this okay um when the switch is in the

00:32:15.519 --> 00:32:19.319
up position VX equals

00:32:21.278 --> 00:32:29.599
VN so this is VX when the switch is in

00:32:24.720 --> 00:32:29.600
the down position VX is equal to zero

00:32:31.759 --> 00:32:36.839
okay and I rinse and repeat and I get

00:32:34.480 --> 00:32:40.960
this now now I have this pulsating

00:32:36.839 --> 00:32:42.519
voltage VX okay what's the average value

00:32:40.960 --> 00:32:45.720
of that voltage

00:32:42.519 --> 00:32:47.399
VX right I can take you know simple

00:32:45.720 --> 00:32:50.720
integration right one over T the

00:32:47.398 --> 00:32:53.879
integral of VX of T over a period

00:32:50.720 --> 00:32:58.798
T okay and what I would

00:32:53.880 --> 00:33:01.159
find is the average voltage of VX

00:32:58.798 --> 00:33:05.359
is equal to D *

00:33:01.159 --> 00:33:08.880
VN all right so I can create a waveform

00:33:05.359 --> 00:33:11.519
here whose average value is something

00:33:08.880 --> 00:33:13.480
different than VN just by controlling

00:33:11.519 --> 00:33:19.960
this timing

00:33:13.480 --> 00:33:22.919
D all right so now if my load resistor

00:33:19.960 --> 00:33:25.919
here was a space heater you know maybe

00:33:22.919 --> 00:33:27.519
this is some load resistance RL and I

00:33:25.919 --> 00:33:29.840
wanted to modulate the power to that

00:33:27.519 --> 00:33:32.120
load resistance by controlling the

00:33:29.839 --> 00:33:35.278
average voltage on the load resistance

00:33:32.119 --> 00:33:38.518
then this technique would work

00:33:35.278 --> 00:33:40.919
great if on the other hand my load was a

00:33:38.519 --> 00:33:43.000
microprocessor and I start you know

00:33:40.919 --> 00:33:44.240
pulsing 12 volts between 12 volts and

00:33:43.000 --> 00:33:47.079
zero on it I'm probably going to blow it

00:33:44.240 --> 00:33:49.038
up right so that's no good all right but

00:33:47.079 --> 00:33:52.038
this notion is at least that I can

00:33:49.038 --> 00:33:55.038
control an average voltage by pulsing a

00:33:52.038 --> 00:33:58.599
set a switch okay and this would be

00:33:55.038 --> 00:34:01.200
known as pwm or pulse width modulation

00:33:58.599 --> 00:34:02.959
because I control the average volage by

00:34:01.200 --> 00:34:05.080
the fraction of the time the switch is

00:34:02.960 --> 00:34:08.480
in one position versus the

00:34:05.079 --> 00:34:11.440
other okay so that's that's the basic

00:34:08.480 --> 00:34:12.960
concept we're going to be using how do I

00:34:11.440 --> 00:34:16.519
fix this

00:34:12.960 --> 00:34:19.440
little problem of in practice right what

00:34:16.519 --> 00:34:21.280
I wanted was a DC voltage what I got was

00:34:19.440 --> 00:34:23.800
a pulsating voltage that just happened

00:34:21.280 --> 00:34:25.720
to have the right average value well I

00:34:23.800 --> 00:34:28.519
could go do something like this maybe

00:34:25.719 --> 00:34:30.158
I'll go back and say okay let me throw

00:34:28.519 --> 00:34:33.838
in a

00:34:30.159 --> 00:34:36.280
filter and extract out the component I

00:34:33.838 --> 00:34:39.159
want right I want the average value of

00:34:36.280 --> 00:34:43.000
VX so maybe I'll come back here and say

00:34:39.159 --> 00:34:46.119
okay let me throw in a filter and I'll

00:34:43.000 --> 00:34:46.119
use an inductor

00:34:47.159 --> 00:34:53.240
here an l and if I want optionally I can

00:34:50.960 --> 00:34:57.760
put a capacitor here

00:34:53.239 --> 00:34:59.319
C okay and you know I think people can

00:34:57.760 --> 00:35:02.720
look at

00:34:59.320 --> 00:35:07.079
this filter block and recognize that as

00:35:02.719 --> 00:35:09.319
a low pass filter the DC component of VX

00:35:07.079 --> 00:35:13.440
passes through the filter to the

00:35:09.320 --> 00:35:15.039
output and the AC component of VX gets

00:35:13.440 --> 00:35:17.720
rejected by the filter and doesn't get

00:35:15.039 --> 00:35:19.679
to the output so in this case I might

00:35:17.719 --> 00:35:22.679
get an output voltage V out that looks

00:35:19.679 --> 00:35:24.960
something like this I'm going to sort of

00:35:22.679 --> 00:35:27.279
make this up but you know I'm amplifying

00:35:24.960 --> 00:35:28.838
the Ripple but eventually it's going to

00:35:27.280 --> 00:35:30.920
filter

00:35:28.838 --> 00:35:33.400
the energy content of that and the

00:35:30.920 --> 00:35:35.159
fundamental and higher harmonic terms of

00:35:33.400 --> 00:35:37.599
VX are going to go away and the DC terms

00:35:35.159 --> 00:35:40.799
going to go through and I get an output

00:35:37.599 --> 00:35:43.519
voltage V out that's very close to

00:35:40.800 --> 00:35:46.039
whatever value I want and if I'm

00:35:43.519 --> 00:35:49.199
basically make the filter cut off hard

00:35:46.039 --> 00:35:51.318
enough I can't distinguish between V out

00:35:49.199 --> 00:35:55.399
and the average value of VX and I get

00:35:51.318 --> 00:35:59.639
exactly what I wanted Okay so we've

00:35:55.400 --> 00:35:59.639
essentially now created

00:36:00.960 --> 00:36:03.639
a voltage

00:36:04.358 --> 00:36:09.279
converter that lets me use this

00:36:07.480 --> 00:36:13.039
pulsewidth modulation by controlling

00:36:09.280 --> 00:36:15.920
this duty cycle D to regulate the output

00:36:13.039 --> 00:36:17.960
just the way I wanted so instead of you

00:36:15.920 --> 00:36:19.760
know here I'm just changing the gate

00:36:17.960 --> 00:36:21.880
voltage on my transistor to control the

00:36:19.760 --> 00:36:23.160
output here I'm changing timing I'm

00:36:21.880 --> 00:36:26.119
going to control

00:36:23.159 --> 00:36:27.679
timing okay and by controlling timing I

00:36:26.119 --> 00:36:31.318
control average value and then I get

00:36:27.679 --> 00:36:33.919
what I want right any questions about

00:36:31.318 --> 00:36:37.559
that what's what's the

00:36:33.920 --> 00:36:41.680
efficiency that is an excellent question

00:36:37.559 --> 00:36:41.679
the answer is

00:36:42.239 --> 00:36:47.199
um ideally theoretically the efficiency

00:36:46.119 --> 00:36:51.358
can be

00:36:47.199 --> 00:36:54.759
100% in reality it can't be why do I say

00:36:51.358 --> 00:36:58.960
the efficiency can ideally be

00:36:54.760 --> 00:37:02.359
100% well how would I implement

00:36:58.960 --> 00:37:04.159
this box in the real world usually I I

00:37:02.358 --> 00:37:06.119
don't get semiconductor single pole

00:37:04.159 --> 00:37:08.598
double throw switches the way I would

00:37:06.119 --> 00:37:11.680
usually build this Beast is like

00:37:08.599 --> 00:37:14.359
this okay I would usually have a first

00:37:11.679 --> 00:37:17.399
switch and a second switch implemented

00:37:14.358 --> 00:37:18.519
like this so I close this when Q of T is

00:37:17.400 --> 00:37:21.200
equal to

00:37:18.519 --> 00:37:22.800
one and I close this one when Q of T is

00:37:21.199 --> 00:37:29.318
equal to

00:37:22.800 --> 00:37:29.318
zero okay and then I build my filter

00:37:30.318 --> 00:37:37.719
and then I put my load on here okay

00:37:35.280 --> 00:37:40.119
so what would be the efficiency of this

00:37:37.719 --> 00:37:44.039
thing well let's think about

00:37:40.119 --> 00:37:46.400
this um this is voltage Vex and this is

00:37:44.039 --> 00:37:46.400
voltage

00:37:46.440 --> 00:37:49.599
vout all

00:37:50.838 --> 00:37:56.799
right what power is theoretically

00:37:54.039 --> 00:37:59.079
dissipated in my switch if I have an

00:37:56.800 --> 00:38:01.680
ideal switch has zero resistance when

00:37:59.079 --> 00:38:02.800
it's on and has infinite resistance when

00:38:01.679 --> 00:38:06.679
it's

00:38:02.800 --> 00:38:08.880
off what's that zero power why because

00:38:06.679 --> 00:38:12.838
the power dissipated the power that goes

00:38:08.880 --> 00:38:17.358
into this box let me call this V

00:38:12.838 --> 00:38:19.880
switch let me call this I switch okay

00:38:17.358 --> 00:38:22.039
well P switch the power going into the

00:38:19.880 --> 00:38:25.960
switch the power being dissipated in the

00:38:22.039 --> 00:38:28.039
switch is going to be V switch time I

00:38:25.960 --> 00:38:32.880
switch

00:38:28.039 --> 00:38:35.358
okay well if it's an ideal switch then

00:38:32.880 --> 00:38:37.880
if the switch is on V switch is

00:38:35.358 --> 00:38:40.719
zero right it's ideal so it has no

00:38:37.880 --> 00:38:42.519
voltage drop when it's on so the power

00:38:40.719 --> 00:38:44.598
when it's on is

00:38:42.519 --> 00:38:46.599
zero when the switch is off it has

00:38:44.599 --> 00:38:50.359
infinite resistance so the switch is

00:38:46.599 --> 00:38:52.519
current zero so basically the power

00:38:50.358 --> 00:38:54.318
going into the switch if it's an ideal

00:38:52.519 --> 00:38:57.719
switch

00:38:54.318 --> 00:39:01.119
um is ideally zero so these these

00:38:57.719 --> 00:39:02.639
elements this ideal switch is a lossless

00:39:01.119 --> 00:39:05.079
element

00:39:02.639 --> 00:39:07.920
right

00:39:05.079 --> 00:39:10.839
likewise I wasn't I didn't just randomly

00:39:07.920 --> 00:39:14.358
choose any filter here right I chose an

00:39:10.838 --> 00:39:16.000
LC filter why did I choose an LC filter

00:39:14.358 --> 00:39:17.639
I choose an LC filter because inductors

00:39:16.000 --> 00:39:19.599
and capacitors are energy storage

00:39:17.639 --> 00:39:21.440
elements if they're ideal then they

00:39:19.599 --> 00:39:25.960
store energy but they don't dissipate

00:39:21.440 --> 00:39:28.559
energy right so basically

00:39:25.960 --> 00:39:30.880
everything in the box here everything

00:39:28.559 --> 00:39:33.400
between the input and the output is a

00:39:30.880 --> 00:39:36.119
lossless element so then one would

00:39:33.400 --> 00:39:39.480
assume that if every element's lossless

00:39:36.119 --> 00:39:42.000
any energy walking in to the left comes

00:39:39.480 --> 00:39:44.880
out to the right right and that's how

00:39:42.000 --> 00:39:48.760
that that kilowatt little 400 volt to

00:39:44.880 --> 00:39:51.599
12vt converter I showed you um in the

00:39:48.760 --> 00:39:54.319
photo is about 97% efficient it's not

00:39:51.599 --> 00:39:55.920
100% because you know the wires have

00:39:54.318 --> 00:39:57.519
some resistance and the switches have

00:39:55.920 --> 00:39:58.720
some on-state resistance a whole bunch

00:39:57.519 --> 00:40:02.559
of things that contribute to loss and

00:39:58.719 --> 00:40:05.399
we'll talk about that um but I can make

00:40:02.559 --> 00:40:08.000
it really close to 100% even though I

00:40:05.400 --> 00:40:09.519
might be doing a huge step down right so

00:40:08.000 --> 00:40:11.800
if I tried to build a linear regulator

00:40:09.519 --> 00:40:13.800
that was going from 400 to 12 volts

00:40:11.800 --> 00:40:14.920
that' be about 2 and a half% efficient

00:40:13.800 --> 00:40:16.720
right so if I want to generate a

00:40:14.920 --> 00:40:19.760
kilowatt at 2 and a half% efficiency

00:40:16.719 --> 00:40:24.639
what is that 40 kilowatt input and

00:40:19.760 --> 00:40:26.440
instead what I get is sort of like 1.03

00:40:24.639 --> 00:40:27.879
kilowatt input to generate a kilowatt

00:40:26.440 --> 00:40:30.440
output right

00:40:27.880 --> 00:40:33.760
so the whole Magic that we're going to

00:40:30.440 --> 00:40:36.000
talk about this term is how can I use

00:40:33.760 --> 00:40:38.760
sort of perfectly lossless elements draw

00:40:36.000 --> 00:40:41.599
energy in process it and put it out the

00:40:38.760 --> 00:40:43.720
other side okay and by the way I should

00:40:41.599 --> 00:40:45.960
say not only did I say oh inductors and

00:40:43.719 --> 00:40:50.039
capacitors are lossless in principle

00:40:45.960 --> 00:40:54.119
lossless elements uh it wasn't an

00:40:50.039 --> 00:40:57.679
accident that we put an inductor

00:40:54.119 --> 00:40:59.440
here right because think about it when

00:40:57.679 --> 00:41:03.078
this switch is

00:40:59.440 --> 00:41:04.920
closed right I have V in on this side of

00:41:03.079 --> 00:41:07.480
the inductor and V out on this side of

00:41:04.920 --> 00:41:10.838
the inductor and I have current flowing

00:41:07.480 --> 00:41:13.960
this way right well what's happening

00:41:10.838 --> 00:41:15.799
when this switch is closed basically

00:41:13.960 --> 00:41:17.400
there's voltage across this inductor and

00:41:15.800 --> 00:41:19.839
current going through it we are storing

00:41:17.400 --> 00:41:21.559
energy in that inductor so the

00:41:19.838 --> 00:41:22.880
difference in voltage between the input

00:41:21.559 --> 00:41:24.279
and the output is basically putting

00:41:22.880 --> 00:41:26.680
energy in the

00:41:24.280 --> 00:41:28.079
inductor in this the other part of the

00:41:26.679 --> 00:41:30.159
cycle

00:41:28.079 --> 00:41:31.440
when I turn this switch off and this

00:41:30.159 --> 00:41:34.318
switch

00:41:31.440 --> 00:41:36.679
on basically I'm taking now I have a

00:41:34.318 --> 00:41:38.079
negative voltage across the inductor I'm

00:41:36.679 --> 00:41:40.159
taking energy out of the inductor and

00:41:38.079 --> 00:41:43.039
put it in the output so essentially I'm

00:41:40.159 --> 00:41:45.440
using this inductor as a filter but it's

00:41:43.039 --> 00:41:48.279
also an intermediate store of energy

00:41:45.440 --> 00:41:50.318
that lets me kind of take energy from

00:41:48.280 --> 00:41:52.920
the input and transfer to the output

00:41:50.318 --> 00:41:54.960
with a voltage conversion without losing

00:41:52.920 --> 00:41:57.639
any of the

00:41:54.960 --> 00:42:01.440
energy excellent question long answer to

00:41:57.639 --> 00:42:01.440
a short question any other

00:42:04.119 --> 00:42:12.519
questions okay so as I said um my goal

00:42:09.480 --> 00:42:14.079
is to sort of first of all teach you a

00:42:12.519 --> 00:42:16.400
lot of the underlying principles this is

00:42:14.079 --> 00:42:18.280
the this is the world's if you will

00:42:16.400 --> 00:42:20.079
simplest switching power converter so

00:42:18.280 --> 00:42:23.200
the when we use this technique we also

00:42:20.079 --> 00:42:23.200
often say we're switched

00:42:24.079 --> 00:42:27.680
mode all right with the notion that

00:42:26.400 --> 00:42:29.480
we're going to use

00:42:27.679 --> 00:42:31.480
switches and energy storage elements to

00:42:29.480 --> 00:42:33.159
process energy and that's sort of what

00:42:31.480 --> 00:42:35.440
sits at the core of Power

00:42:33.159 --> 00:42:38.358
Electronics okay and as I said we're

00:42:35.440 --> 00:42:39.960
going to look at all of the aspects how

00:42:38.358 --> 00:42:41.318
do you design these things how do you

00:42:39.960 --> 00:42:43.318
control them how do you design the

00:42:41.318 --> 00:42:44.480
components and by the time we're done

00:42:43.318 --> 00:42:46.920
you should be able to put it all

00:42:44.480 --> 00:42:49.519
together and and start designing Power

00:42:46.920 --> 00:42:52.200
Electronics of your own and you will for

00:42:49.519 --> 00:42:57.960
the final project

00:42:52.199 --> 00:42:57.960
okay so any final questions

00:42:59.239 --> 00:43:04.719
okay we'll wrap up today and I will see

00:43:01.039 --> 00:43:04.719
everybody on Wednesday