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PWM regulator

A project log for Bench power supply

USB and manual control, and monitoring, 2 channel 5A 30V bench supply.

rue-mohrRue Mohr 08/10/2014 at 23:250 Comments

had.io firefox things still not fixed...

So, I been working on getting the pwm regulator thing worked out. over the past few days I been looking at the MC34063, UC3842, and TL494. The 34063 is trickey to get to drive an external fet, the UC3842, without tricks is limited to a miniumum voltage of 2.5V. The TL494 is not a great design fit either. So, right now I have a LM339 based pwm genorator running on the bench, at 100kHz, which seems to be a fine freq (not too low, not too high). 

The bulk supply I have in it can output up to 36V, my peak design output is 30V, so the converter needs a duty higher than 83% (+- losses). 5A, so, all the design specs are comming togethor. I'm expecting to use a discontinious mode converter, this should help handle the range of voltages and currents its dealing with.

Posting the avr firmware is still on my todo list!

Not much to take pictures of, my appologies.

It turns out that the 3842 has about .2V schmitt on its votlage error amp, meaning the output ripples by that much, that wont do!

After a few itterations, this is quickly moving towards a set of analog regulation amplifiers that output to a PWM power stage. Part of the trick is to find comparitors for the pwm that are fast enough for the switching. I dont think I'm gonna make 300Khz, oh well. I suppose I could implement a sloppy pwm regualtor to get the supply up and tune it later, I'm really itching to have a better supply.

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