The output ripple of PFS726 is very large
All parameters are calculated from PI Expert.
The schematic and the output voltage waveform is attached.
The peak to peak amplitude of the output ripple is 40V or so. (with 10x probe)
I tried to change the number of turns of the boost inductor but little improvement.
Comments
I'm sorry to bother you, the problem has been solved.
The load is 250W, and I designed the boost inductor for 540W load in software.
So the inductor is larger than that of 250W.
Thank you~
The output voltage is not stable.
At the beginning, the voltage is 385VDC, and it gradually decreases, 380V....378V...375V...370V...369V,after about one minute, until 365V or so, it jumped to 385V suddenly, then it drop again and again.
The design document is attached.
| Attachment | Size |
|---|---|
| PFS726_eric.pdf (83 KB) | 83 KB |
Your PFS does not work properly. you can try a few things to see if there is any change: Check input current waveform. If there is a flat top, then increase the PFC inductance. You can also ground your PFC inductor core to DC- for better EMI. Also, try to aviod FB pin trace directly under the PFC inductor core area. It may resutls in noise pick up on FB pin.
I've tried several tens of inductor, efficiency is OK, but the power factor is too low(<0.82) when the load is 400W to 500W LED. how can I improve the power factor?
| Attachment | Size |
|---|---|
| IMG_2561.JPG (2.15 MB) | 2.15 MB |
if you lower C4 1uF and C5 1.5uF cap values, it could increase the PF.
by the way we do introduce PFS4 family also have high line parts.
I've tried to remove C4 and lower C5 to 1uF and 220nF, but there is no improvement.
I tried to lower the value of V pin resistor from 9MOhm to 6MOhm. PF increase from 0.78 to 0.95, but the output voltage decrease from 385V to 375V. So how to calculate this resistor to a proper value?
any particular reason you want to use differnt V pin resistor? please follow the datasheet design example on page 10. 4Mohm Vpin and FB pin resistor. also 100nF V pin capacitor is used in example.
could you share with us your PIXL design? please print it in PFD version so we can open it withour worry about PIXL version. PIXL carries a lot your system parameters which help us for the review.