How to choose proper feedback for power supply stability?

[wossy]

slup068

Hi

I am designing a linear bench supply which consists of a comparator, some power mosfets and a diff amp which measures the output and then feeds the voltage back to the comparator. My problem is that the loop is unstable and I know I have to place some feedback around the comparator to compensate the circuit. I need to know how to analyse the circuits frequency response so that I can choose the correct feedback elements. I need to do this cheeply without the aid of any expensive test equipment

Thanks

 

[flatulent]

Re: Power Supply Stability

Use an ordinary op amp instead of the comparator. This will make the system loop gain more linear. Then you can brute force the stability by putting a capacitor across the op amp inverting input to output.

 

[cesare]

Re: Power Supply Stability

Usually if you put a very low pole on the error amplifier you obtain a stable closed response (dominant pole compensation) but the transient performance will be also very poor.

 

[mag]

Re: Power Supply Stability

Pls ref :


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[barrybear]

Re: Power Supply Stability

Change the comparitor for an opamp and decouple the feedback loop. Make sure the opamp is being biased correctly. Make sure that there is always a load on the output ( use a resistor 4.7kohms).

Barrybear