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DPA425R - 30W (Multioutput)output loading problem

Posted by: pramodtjm on

I used the multioutput circuit generated by PI expert software.(15V-2Amp,+12V - 150mA, -12V -150mA).

Iam not able to load the circuit beyond 100mA. It turns off when load is increased .When  load is released 15V is regained.

DPA425R is used. 

Files

Attachment Size
DPA-Switch_PIDesign1.uds 549 KB

Comments

Submitted by PI-Sarek on 08/14/2012

Hi, The typical reasons for such a problem could be: 1. Incorrect concetion of primary or secondary winding connections. For a converter to operate as a flyback converter, it is necessary that the primary and secondary start and end terminals are connected correctly. If the primary start is connected to the drain terminal of the DPA Switch, it is necessary that the secoindary start terminal is connected to the anode of the positive output rectifier and to the cathode of the negative output rectifier. If there is error in this connection, a flyback converter gets configured as a "forward" which will result in a large leading edge current causing immediate termination of the switching cycle and the converter will eventually go into auto-restart. 2. Incorrect X-pin resistor The X-pin resistor programs the current limit for the part.Please verify the value of this resistor. If you continue to experience any problems, please provide us a copied of schematic, layout and transformer construction and we will help you to resolve this issue. Please also include oscilloscope images of the drain current waveform when the power supply is in operation and when you exceed a load of 100mA. Regards, PI-Sarek Regards PI-Sarek

Submitted by pramodtjm on 08/27/2012

Hi,I have checked the polarity of primary and secondary waveforms and satisfies the condition for flyback converter.

After rewinding the transformer ,i was able to load 15V upto 650mA and +12,-12V upto 100mA. 

But the voltage waveform across drain-source showsa  spike of around 250V when the device turns off under loaded conditon.The spike increases with increase in load.I have attached schematic and tfr details.

Submitted by PI-Sarek on 08/28/2012

Hi,

It is good to know that the converter is operating and you are able to load it. In order to understand your comment about the voltafge spike, I would like to review the schematic and the waveform. I could not see any schematic in the file that you attached. Would you please attach the schematic as a PDF, JPG or TIF file?

I was able to open the document with the transformer details just fine.

If possible, please also attach voltage waveforms being sen by you.

Regards PI-Sarek

Submitted by pramodtjm on 09/02/2012

Hi, I have attached schematic in pdf format. 

Testing of smps is stopped currently due to non avilability of DPA switch.I will send the waveforms once i get the switch.

Kindly gothrough the schematic. 

Submitted by PI-Sarek on 09/11/2012

Please load the converter to whatever load you can and send me the primary current waveform. This will help me understand what the problem may be. Regards PI-Sarek