switching stop for a moment at start up
Hello
I have developed SMPS using TOP258PN. It has 5 output voltages and total power is 30W. It seems to be working well but when I start SMPS switching is stopped for 8.6ms and then restart during slow start process.
please refer attached file
Comments
Sorry
Here is the file
| Attachment | Size |
|---|---|
| scope_36.jpg (146.92 KB) | 146.92 KB |
Hi Iskim,
Thank you very much for the waveform. Looking at the provided waveform it seems that after soft start of around 17msec the PWM stops switching and recovers again after 8.6 msec. Since this is not a LATCH protection you may check and verify the following:
PIN BY PIN VOLTAGE/CURRENT LEVEL VERIFICATION:
1. M PIN - Verify during start-up if current level limit is being exceeded. If the current exceeds 112 μA (IOV) for longer than 100 μs, then switching is disabled and the supply enters auto-restart. This will prevent further increase in output voltage but does not latch off the power supply. Please refer to the application note on page 7 on the link belolw:
https://ac-dc.power.com/sites/default/files/product-docs/an43.pdf
2. C PIN - Monitor the behavior of the control pin (C pin) during the start up and the time when PWM switched off at around 8.6 msec. Kindly refer to page 8 of the link below for the C pin:
https://ac-dc.power.com/sites/default/files/product-docs/topswitch-hx_family_datasheet.pdf
When the levels are already verified and fault is being triggered then the next step would be to check on the schematic and see if the values used is/are correct. Incorrect component value or incorrect selection of component can lead to fault conditions. Hope this helps.
Hi Iskim,
Could you kindly resend the file? It seems that there is not attachment. Thank you very much.