Disabling UVP/OVP protections

[370forlife]

I have a yuelin YLP-013 that I put together using some old parts (mostly parts pulled from other power supplies, 4A bridge rectifier, teapo caps, etc...) to use as a bench supply to power up various things. Problem is this thing crossloads like a bitch, and as soon as you get even a light load on only the 12v rail, the 5v and 3.3v go high and it shuts off.

Now because I will mostly be using the 12v rail I would like to disable the UVP and OVP for the 5v and 3.3v rails. Voltage regulation won't be too big of a deal as I won't be using it for powering electronics, mostly small motors and other things.

The PWM/protections IC is a EST7502B. On the data sheet, pins 1, 2 and 3 are labeled as the OVP and UVP pins for the 3.3v, 5v, and 12v respectively. Would one simply break the connection from these pins and their voltages?

[Th3_uN1Qu3]

Re: Disabling UVP/OVP protections

If you break the connection you will have zero voltage thus trigger UVP.

First measure the voltage from each of those pins to ground, then cut them from the circuit and wire them to something that'll fool 'em. For the 5v protection you can use a 78L05. If you don't have a 3.3v reg lying around, a voltage divider from the 78L05 output should be stable enough for 3.3v. It only needs 1mA at most so calculate the resistors accordingly.

And btw... contrary to what they say, the 78L05 is NOT short circuit protected. At least not to the instantaneous current that a PC power supply can deliver. So be careful not to short it while you're testing the thing.

[Trinite]

Re: Disabling UVP/OVP protections

I ran into this problem as well, and found that if I put a small load on the +5V line, it worked fine. Might work for a quick fix.