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Design of universal power supply with two isolated auxiliary input using common transformer and common secondary outputs

Posted by: kuldeep.solank… on Tue, 05/11/2021

I want to design SMPS with below specifications:

Input: IN1: 60VAC-280VAC, IN2: 60VAC-280VAC

Output: Out1: 5V/0.5A, Out2: 12V/0.5A, VA: 10

Isolation required between two input supply is of 5KV for HV test.

Single transformer to be used for both inputs at different winding and only one switcher work at a time based on priority. 

Please suggest best compatible design solution.

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Submitted by PI- MarcusJoaquin on Wed, 05/19/2021

Hi Kuldeep,

Do you have a block diagram or a simple schematic?

IN1 and IN2 are the same 60Vac - 280Vac, just needed the schematic to further verify your inquiry.



Submitted by kuldeep.solank… on Thu, 05/20/2021


Schematic is not available right now. This can be traditional flyback convertor design.

This is just an idea to do feasibility of this concept, weather this will work or not?

I need to design two isolated SMPS but I have space limitation in my product.


Submitted by PI- MarcusJoaquin on Thu, 05/20/2021

I understand that this will utilized flyback converter and we can design it with your requirements at 5kV surge.

I ask for the block diagram to understand its application. Maybe we can treat this as two-phase system having one flyback converter, either two inputs works at the same time or not.

But if your requirements is you need to isolate both the inputs, you also need to separate flyback converter as using a single transformer will defeat the isolation purposes.

If we need to design a separate SMPS what is your form factor or any dimension requirements of the PCB and maximum height requirements?