ATX powersupply modifications
After reading some schematics and projects where people modify the very
common ATX powersupply for various uses. I was wondering if it would be
possible to modify such a supply to create a variable constant voltage,
constant current powersupply. The ATX powersupply can deliver quite a
lot of power in a small package, and is very cheap to boot.
Goal of these modifications is to keep the amount of introduced parts
as small as possible while creating maximum flexibility.
Description
The cheapest ATX powersupplies are based around the TL494 PWM
controller chip, or equivalent. And most of those resemble this
schematic with a few modiciations (schematic source):
The supply is partitioned in a few blocks. The second powersupply is
the 5V VSB powersupply and powersupply for the base drive transformer.
The 3.3V is magamp regulator and in the center of it all is the TL494
PWM controller.
The whole overcurrent protection, 3.3V regulator and possible fan
control will be removed. The TL494 will be changed into the ATtiny2313,
and the feedback will be changed by a potmeter. The code running on the
attiny2313 is based on the push pull converter project. The code is a
bit modified to change the output wave polarity but is essential the
same principle.
Setup
Parts used:
Microcontroller code:
Pictures of modifications:
TODO: first atx psu modification
TODO:
Oscilloscope traces
Traces
Conclusion
What next?
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Last update at: 15-02-2011