INN2603K output voltage overshoot at start-up
Hello,
I use a INN2603K for the application example of the innoswitch ep datasheet page 8. I reduced the output voltage to 10.5V, 800mA, use reduced current limit and 230Vac input voltage. When I start-up the board there is an overshoot of the output voltage to 15V and then to 10.5V. The time from 0V to 15V is 9ms. The time from 15V to 10.5V 9.3ms. I use the capacitor values like the reference design. Have you some hits where to look?
Best regards,
SW-EVS
Comments
Here it is!
| Attachment | Size |
|---|---|
| Schematic (296.04 KB) | 296.04 KB |
| primary inductance 800uH (152.57 KB) | 152.57 KB |
Hi SW-EVS,
I saw the schematic and the values don't give any lead as such. I would like to see the waveform for BPS voltage, primary drain current and output voltage. Output overvoltage occurs when the BPS charges to 4.4 V slower as compared to the output voltage reaching its expected value and so the secondary side controller cannot take over soon enough to start regulating. Please provide me this waveform.
PI-AP
Hello,
I found the Problem. RDR-420 "9.2.2 Efficiency with a Schottky Diode, SS16, in Parallel with Q1, SR FET" show an efficiency improvement using a Schottky diode in parallel to the secondary MOSFET. I also do that, but I forgot to decrease the snubber capacitance. Reducing the value of the capacitor solved the Problem.
Hi SW-EVS,
Could you please provide the schematic and transformer design files? Also if you could provide the image of the waveform, it would be helpful. Just as a headsup, I hope you are using the corresponding BPP capacitor value for the reduced current limit as the example in the datasheet is not for reduced current limit.
PI-AP