Load regulation problem with TOP266KG design

Posted by: durgesh on 03/03/2016

Hi,

In one of our SMPS design, we have used TOP266KG to generate 12V,2.5A (30W) power from 60-300VAC input range. But during testing we observed that 12V output is stable at no load condition. But, whenever we connect load of >=1A then there are deeps present on 12V output trail; output volatge drops to 0V and again rise to 12V continuously.

Following are the changes which we have done but there is no change in output:

1) Removed D2 and D3. (Thought there wiil be over voltage at output side)

2) Removed R14 and short X pin to source. (Thought current limiting resistor value is wrong)

3) Removed R9.

Please help me with the above situation.

Thanks,

Durgesh

Files

AC_SMPS_TOP_JX.png (318.31 KB)

Comments

Did anyone faced the same issue with TOP266KG design? Waiting for reply.

Thanks,

Durgesh

Hello durgesh,

can you also share the waveform about the output voltage with us too?

Hello PI-YY,

Please find attched images of output waveform when 500mA load is connected at output.

Thanks,

Durgesh

Attachment	Size
P_20160310_123514_HDR.jpg (2.17 MB)	2.17 MB
P_20160310_123418_HDR.jpg (2.67 MB)	2.67 MB

Hello durgesh,

i recommend you to increase input filter capacitor to maintain a minimum DC bus voltage of 70 V. if you run our PIxls or PI expert, you will find the recommended value. below is the link:

https://piexpertonline.power.com/

i believe what happend here is your input capacitor is low, when the power supply run at low line, the input capaictor voltage already had big deep because it cannot supply the power. when you use 20uF capacitor, the power supply hit the power limitation and do the auto-restart protection.

I check the PIxls spreadsheet, if your minimum input voltage is 60VAC, you may need 228uF input capacitance. if you minimum input voltage is 85VAC, you need 58uF capacitance.

I recommend you to increase the input capacitance, you will see you can deliver more and more power.

Best Regards

Jia