Paralleling Power Supply Units Made Easy ???

That's not quite right. The supply that sees higher voltage than it's setpoint will just shut off. The pwm duty cycle will go to zero percent. This is a very safe condition for the supply. There's no oscillation or whatever. You're not going to overstress the error amp either. The amp is probably powered by 12V. The reference voltage to the error amp is usually around 5V. If the first supply is at 15V then the second supply needs to go up to 15V * 12/5 = 36V. That's highly unlikely that the two setpoints are that far apart.

Sal

LScamper wrote:
Some thoughts:

If there is diode isolation between them there should be no problem.

I do see a problem if there is no diode isolation and one supply reaches its voltage set point and the other is still charging the battery.

When the first supply reaches its set point it goes into constant voltage mode. When the other supply charges the voltage above that set point the first supply's control loop tries to lower the voltage to its set point, it can not do that. It will keep trying and will saturate. At that point the first supply is operating open loop. Depending on the supply design it may just shut the output off, a good thing. It is possible that the error amp, being over driven, will saturate and reverse its output if it is not designed well. This would turn on the output to full voltage, a bad thing! I can only guess that these cheap supplies are not designed worrying to much about all the possible ways they will be used. I don't think anyone can say exactly how they will react to being paralleled without a complete knowledge of how they are designed.