DPA422G circuit doesn't always start up

Hi,

I am not sure what exatly is happening at start up. Could you please capture waveforms for output voltage and control pin during start up?

Regards,

PI-NANO

Hi,
I've attached a pdf to show some signals on a working device.
regards,

Barry

Hi,

Its a bit confusing now. Do you have working devices and non working devices with you. I think I have not understand the problem fully. Could you please describe the problem clearly under what conditions it doesn't start up. Could you please send your specifications, PIExpert/PIxls and Layout files in order to get clear understanding of the problem.

Regards,

PI-NANO

Hi,
Thanks for your time.
I'm not in a position to continue with this at the moment as I'm busy on another project. Some time next week I'll try and get all the data that you require.
Once again, thank you.
Best regards, Barry

Hi,
I think I may have solved the start up problem but I’d like your opinion and advice.
The circuit originally had suppression components on the input of the power supply. I think the chokes are reacting with the transformer primary winding causing a high degree of oscillation. The ‘scope traces indicate this. Is this a common problem?

Regards,

Barry

Hi,

EMI filter components are used in the circuit in order to suppress the switching noise generated from the circuit. However filter components needs to be designed carefully, because power supply can produce oscillations when the resonant frequency of EMI filter components is close to the control loop crossover frequency. You can try changing the component values in order to make the power supply working with filter components present on the board.

Regards,

PI-NANO