UC3843: Slope Compensation

Expert 1035 points

Part Number: UC3843

Why the slope compensation usually use down slope of inductor current

is any problem using turn on slope?

over 3 years ago

0 Hong Huang over 3 years ago

TI__Mastermind 47475 points

Hi,

It is easy to design.

0 J over 3 years ago in reply to Hong Huang

Expert 1035 points

why use upslope can't easy design?

0 Hong Huang over 3 years ago in reply to J

TI__Mastermind 47475 points

Hi,

You can figure out downslope compensation directly and quickly from a plot in general. If you are ok to figure out either way, then it is ok for you to use either compensation - the effect is the same. Actually the implementation is upslope in practice.

0 J over 3 years ago in reply to Hong Huang

Expert 1035 points

how do I know the downslope compensation directly and quickly, the upslope is not?
I see most slope compensation is using downslope not upslope but I don't know why

0 Hong Huang over 3 years ago in reply to J

TI__Mastermind 47475 points

cid:image005.png@01D685CE.5F04B6F0

The slope compensation is to make current start point and end point at same level for CCM. The above downslope compensation shows how much slope is needed so you can get it right away.

0 Hong Huang over 3 years ago in reply to Hong Huang

TI__Mastermind 47475 points

Attach the picture:

0 J over 3 years ago in reply to Hong Huang

Expert 1035 points

I know the slope compensation is make the start/end current at same level,

My question is the slope compensation m is usually use m2 not m1 that why?

m=0.5*m2 or m=m2 like that

0 Hong Huang over 3 years ago in reply to J

TI__Mastermind 47475 points

Hi,

Let's start without slope compensation (remove the -m)

1. let m1 hit the threshold (the dashed line),

2. then use -m2 to reach T. You can see the current cannot come back to start of m1.

3. Then you need shift -m2 end until reach the same start of m1.

4. Then draw a line from start of m1 to start of shifted -m2,

5. extend to T, that line is -m.

0 J over 3 years ago in reply to Hong Huang

Expert 1035 points

Using the m2 is directly, that mean I can not use m1 to do the slope compensation?
if I want to use m1 how do I do or I can't use m1?

0 Hong Huang over 3 years ago in reply to J

TI__Mastermind 47475 points

Hi,

I only know how to do downslope compensation.

0 J over 3 years ago in reply to Hong Huang

Expert 1035 points

Ok I got it thank your help

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UC3843: Slope Compensation