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Merging three separate design into one

Posted by: papaisou11 on

Hi...

I have three smps with tnysw-4 family. The wattage ratings are different.

I want to merge this three design from the primary side.

Thus it will have single bridge diode with single pi filter and after that the High voltage DC will go to the three smps.

I am not willing to use multiple output tranformer.

How can I choose the capacitor and emi choke value?

Thanks.

Comments

Submitted by PI-Kobe on 09/01/2020

Hi,

Can you provide a schematic/s for the three SMPS? Thanks.

Regards,

Submitted by PI-Kobe on 09/03/2020

Hi,

I'm sorry but I can't seem to view your schematic files. Can you send me an image instead (may be a jpeg or png type of file) ? Thanks.

Regards,

Submitted by papaisou11 on 09/08/2020

Hii PI-Kobe.

Sorry for the late reply. I have attached the schematics.

My concern is I want to eliminate the bridge rectifier and the Pi filter of the individual. But, I want to use a single bridge rectifier along with a single pi filter instead of three.

Thus, A high voltage dc will be available across the output after all EMI filteration and bridge rectifier and this will go to the individual SMPS inputs.

Can I just choose the parallel value for the capacitors and The Inductor choke? and the bridge diode as per the total input current?

Attachment Size
1.JPG 71.63 KB
2.JPG 69.08 KB
3.JPG 69.95 KB
Submitted by PI-Kobe on 09/08/2020

Hi,

As a starting point, I think you should first compute for the total bulk capacitance needed to supply the three individual SMPS. It is recommended to use a minimum of 57uF since the total output power required would be 28.5W (9V 1.5A, 12V 0.5A, 18V 0.5A = 28.5W and a 2uF/W rule-of-thumb can be used to estimate the needed bulk capacitance)

Aside from the bulk capacitance, I think you would still need to tune the inductor choke since you're dealing with an increase in the required output power. You may also opt to use a Pi-filter or a CMC. This would all depend on your design requirements and the constraints.

As for the bridge rectifier, you may choose the appropriate component with the input current rating and thermals taken into consideration. I hope this helps

Regards,

Submitted by papaisou11 on 09/11/2020

Hiii

Pi-Kobe. Thanks for giving your valuable time.

To making the calculation easy, I generated another smps using topswitch with 28.5Watt output in TOPswitch HX.

I have set the output at 12.0V at 2.37A.

Therefore, PI-Expert give me another SMPS with a simple HV filter. Can I use this one?

I am sharing you the images for your convinces.

I also read somewhere that the EMI capacitor C6 across the transformer T1 is directly linked with input choke.

So my planning is to use the circuit portion of the HV DC side and the value of the C6 with my previous design of 28.5Watt accumulated TNY switch SMPS.

What is your opinion?

Attachment Size
diode_bridge.JPG 24.3 KB
Capture.JPG 75.82 KB
Submitted by papaisou11 on 09/11/2020

Sorry to mention. As my previous design has three individual smps, I will share the capacitor C6 value.

Thus 0.11 (Approx) nF in each smps.

Submitted by PI-Kobe on 09/11/2020

Hi,

I think what you did was a good starting point. As far as the input side (bridge) is concerned, as long as you design using the required power, you may be alright. Just take into account efficiency and properly adjust the ratings of your bridge components. As for the EMI, you may use an input choke and a high input bulk capacitor usually helps, however, there would be numerous ways you can optimize your design if EMI becomes an issue later on.

Regards,

Submitted by papaisou11 on 09/11/2020

Hi..
Indeed your experienced opinions are helpful.

I understand that the EMI is also depends on the PCB routing. I will optimize the design using the above EMI filter circuit. Also, I will take care of the Diode bridge. Planning to use DB107.

Thanks a lot again PI-Kobe.

Submitted by PI-Kobe on 09/11/2020

Hi,

You are most welcome. Indeed EMI would be a challenge that can only be verified on the bench. Hope everything goes smoothly.

Regards,