Need Separate grounds for multiple secondary output

Posted by: mohan.n2293@gm… on 09/14/2017

Hi PI,
My power supply spec is as follows,
Input = 180 v- 440 v
Out 1(main): 5 V ,10 A
Out 2(main):12 V,1 A
Out 3: 5 V,1 A

For out 1 and 2 i need same ground and out 3 i need separate ground.
I tried in PI Expert but i m getting common return path for all the outputs as shown in attachment.

Files

Untitled.png (32.35 KB)

Comments

Hi Mohan,

Good day. Thank you very much for using Power Integrations product. I suppose you are using PIXls? or also known as PI Expert design tool. Let me check the design. To do that I do have some questions:

1. What is your chosen PI product for your design?
2. Do you have the design file of your power supply using Power Integrations design tool?
3. Kindly provide the schematic if there is any.

Regards,

PI-LeoDavinci

Hi LeoDavinci,

Thanks for your replying the post,Please find the answer for question.

1. What is your chosen PI product for your design?
--> Top-HX family Part Num = TOP256EN.

2. Do you have the design file of your power supply using Power Integrations design tool?

--> I have only transformer design files because PI tool can support only 85 to 265 AC input but
in my design i need to use 440v 3 phase input .Please find attachment for transformer design details.

3. Kindly provide the schematic if there is any.
--> Please find the attachment for Schematic .

The problem here is we need separate return path for each output but we are getting same return path in PI design Tool.

Attachment	Size
Transformer Designing (1.69 MB)	1.69 MB
Schematic which i want (26.53 KB)	26.53 KB

Hi Mohan,

Thank you very much for the information you provided. Considering the common ground for your design and comparing it with the PI design here are the points you may consider:

The PI design is based on the 5V and 6V output center tap style wherein the 6V output are of common ground. This is a design reference and guideline. Should a separate ground be considered then we simply consider 6 turns for 6V and 5 turns for 5V and do terminate the grounds separately instead of using a center tap style of 6 turns where 5V output will be tapped on the 5 turns of the whole turns ratio. The PI design does not limit the user to use common or separate ground. What it does is optimize the design according to the area of the core. Now the question is:

Can the user deviate from center tap to separate grounds? The answer is yes, but kindly take note of the wire diameter that will be used should you cascade the two windings since there will be more turns when separating grounds. You may compute the wire diameter needed to fit the area of the core or you can simply do trial and error by using the PI design as a reference since an initial AWG number is suggested.

Will the computed flux density be the same with using separate ground and dedicating turns for each output? The answer is it should be the same since it will not change the power/energy needed to satisfy your design. It will only affect the mechanical factor and coupling of your transformer. But this shouldn't be a major issue at all.

Hope this helps.

Leo