Variable-duty PWM Boost Drive

564

11:07:18

How to: Close left switch and wait. The pot near the bottom will adjust the voltage but it's not particularly stable (bug workaround).

A simplified demo based on the TL494. It's used in a lot of switch mode power supplies and does a lot of tedious work in a single package. There's docs online with more complete info, but in a nutshell, it compares a rising sawtooth wave (green trace) to 2 reference signals (one is shown in blue) and enables the output only when both signals are below the sawtooth.

One of the comparators handles dead-time control, which is why the startup is so gradual. Without that it would overcompensate the difference and cause the output voltage to overshoot.

(Note that the real IC uses error amps for feedback but due to op amp bugs this one just has a pot.)

published 11 years ago

UncleRick

11 years ago

Nicely done, Mamish. Elegant.

Secuture

11 years ago

If i corectly assume it is a little cuted (due to limits) show up demo of tl494 chip internal operation ??

UncleRick

11 years ago

It looks like you almost had yourself painted into the upper left corner. What would you think about this: An adjustable marquee (box), that could surround a drawing, such that the author could move that drawing, around the canvas. Often I get part way through a drawing, only to find myself against a wall and I don't really want to relocate each part, one by one. I can see that moving only a portion of a drawing, could present a logistics problem with the auto-wiring function. A winning solution would be to move the entire drawing. This would be a good fix, to a common problem of running out of room, up against a wall.

UncleRick

11 years ago

I didn't understand your question where you asked...: If i corectly assume it is a little cuted (due to limits) show up demo of tl494 chip internal operation ??

Secuture

11 years ago

Lol he's right u face print suggest u have lot of capacity in nose section and rectangular small bloody eyes lol i recommends banana skin inhalation as cure for this situation

UncleRick

11 years ago

HA! I tried those back in 1971. Banana skins don't do anything at all.

Mamish

11 years ago

You guessed right. I went off the tl494 internal block diagram, minus the parts that take up way too much space; the flip flop would have taken about 13 extra gates.

Mamish

11 years ago

Btw I do like the idea of a way to select and move more than one component at once. That said, for this one I actually planned the corner space pretty specifically.

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