Combining two power supplies TNY285PG

Posted by: devanshsharma on 09/05/2017

Hello,

Please find attached 2 schematic designs using TNY series. My requirement is that I would like to combine these two supplies but not on one single transformer(to isolate both the 5V outputs). My proposed design will have a single bridge and single PI filter and after that 2 TNY ICs and 2 transformers. Kindly let me know if running two TNY switchers on single input circuit is advisable/possible.

Regards
Devansh

Files

Part1 of combination (81.37 KB)

Part2 of combination (84.42 KB)

Comments

Hi Devansh,
Yes it is possible to use single bridge rectifier and filter for the two circuit design. You just need to consider the total current requirement on the fuse and bridge that you would be using. The bulk capacitors are just the sum of the values of the two separate circuits.

For minimum bulk capacitor requirement you may want to use our online spreadsheet design on the link below.

https://piexpertonline.power.com/site/login

Thanks!

Thanks a lot for the quick response. It is very helpful.

Regards
Devansh

Hello,

Please find attached the schematic of the power supply. However I am facing an issue - When 1 Amp current is drawn at 5V supply. The output voltage drops to 0Volts. However when we remove the load the output voltage again stabilizes at 5Volts after 1--2seconds. Can you please let me know where we are doing an error.
Optocoupler used is - PC817B

Regards
Devansh

Attachment	Size
5V1A-5Vp2A-12p5A_SCHEMATIC.pdf (44.34 KB)	44.34 KB

Hi Devanshsharma,
If the 5V 220mA circuit is working, the 5V,1A should also be working properly since it is the same replica.

My question is when exactly the 5V supply drops to 0V. Does it drops to 0V from low load(ex.10mA) or half load(0.5A) or near full load(1A)? So try to sweep the load to know at what point it drops to 0V so we can have a better idea what the fault was.

After pinpointing what level the output drop out of regulation then you have to monitor the BP pin and Drain current. Then maybe you can share your data to us before and at the point where the 5V drops out of regulation.

Regards.