Pls check the voltage across C7, and make sure the voltage is high enough.  And you can use an 10V external power supply to power the optocoupler, and I believe the regulation of the 5V shoyuld be good with the external bias.

regards

I have tested the Voltage across C, following are the results

 Input                             Across C7                      Load

30VDC                            9.5VDC                        50mA

30VDC                            6.25VDC                     No Load

I think the Bias Voltage is Less as u said. Now how do I increase the Bias Voltage?

pritam

PLS modify R3 from 100ohm to 2ohm, and check the regulation. If the no load output can be around 4.6V, then you have to modify the feed back resistor.

Regards

No load o/p was around 4.6V so changed the feedback resistors. now getting O/P of 5.11 V, 15V and -17V @ loads of  240mA, 40mA and 50mA. resp. Attached O/P waveforms. Plz give suggestions to optmize

THANKS.

I guess you do not like the regulation. But it is really hard to solve it since only the 5V channel is close loop and the other two outputs are open loop.

Two possible solutions to improve your problem: 1. dummy load for the other outputs, this is the easiest way but efficiency willl suffer . 2. Optimize the transformer. but you have to try different transformer.

regards