Design flyback power supply for peak power
Hi,
We need a power supply for a circuit that have current peak of 3.5A, these peak can last for 60ms, and it repeats in the frequency of 5 to 100Hz, but the mean circuit power is 25W.
I project was made using piexpert for 15V at 3.5A, we used TOP261YN for the prototype, transformer was made with a EE30 core, it worked, but it's not stable, at peak power the ouput swings betwewn 12V and 19V.
What is the best option for this kind of power supply? should we use a LC filter in the output, or design the power supply with more power capability.
Best regards,
Adriano
Comments
Hello Adriano,
Sorry for the late reply. can you share the actual schematic with us to begin.
when you mention some variation in the output, more or less 3.5V. do you have the waveform or can you discribe more details about how it varies.
Best Regards
Hi,
After some tests, I could get a working prototype setting the target crossover frequency in the PI expert at 3kHz, and using the phase boost network, with this configuration the ouput is stable, with low ripple.
Now I wondering if this crossover frequency is too high, and it could bring another problem of stability to the circuit, or should we use this way, what would you advise next to build a safe power supply?
Best regards,
Adriano
Hello Adriano,
How much pahse margin you get when the crossover frequency at 3kHz? when you setting the crossover frequency at 1khz to 2 khz, how much phase margin you will get or is there any unstable performance you will get
Best Regards
Hello,
The phase margin at 3khz is 62.12 degrees, at 2kHz phase margin is 59.34 degrees and at 1kHz I get a stimated phase margin of 81.71 degrees.
I have not tested the power supply at 2kHz, only in 1kHz which makes it unstable.
Best regards,
Adriano
Hello Adriano
If you can provide us the shcematic and those unstable waveforms, it will be really useful for analysis.
I think with the phase margin you provide, the system should be stable. With higher PM, the transient response will be slower. Depended on your requirment of the transient reponse, you can choose the proper phase margin. By the way how much is your transient load varies? Normally PM at around 60 will make your system has less overshoot and fast time response, i think you should try crossover frequency at around 2K to see if the system is stable or not. If 2K is stable, that should be the OK.
Best Regards
Hello,
I made another prototype, 15V x 4A, and tested with resistive load, I can get the full power with no problem, but using it in our application where the load is pulsed we have some variation in the output, more or less 3.5V, the switching frequency is 66kHz, feedback circuit used is TL431A and PC817B, I tried the phase boost, but I can't get better regulation than this. I would like to hear from power integrations what can be done to get a better regulation in the output.
Best regards,
Adriano