you can go our online PIXL design link, choose TOPJx TOP271E, and use PIXL instead of PI expert, you can have a design accept 5V 20A.

https://piexpertonline.power.com/

Thank you, PI-Neela for your prompt reply; I am now working on the design of 5V/20A in PIXL with TOP271E & I will update you once I advance on to the next stage of designing.

Also, I have limited knowledge when it comes to selection of output recitifers & output capacitors by looking at peak output current & voltage values & rms current values. I am therefore attaching the PIXL file for your reference of 5V-20A so that you may advise which output diode & output capcitor value to use. It would also be extremely beneficial for us if you could go through rest of the values entered as well so that there may be no error.

Another question that rises is whether to select half frequency or full frequency for designing & what are the benefits to select either of the two over the other? For now, I have let it remain at half frequency as it was the default input value.

The point of bias voltage also remains unclear to me as I have limited knowledge for it. The default value was set at 12Volt & the information panel at its right said that it should be greater than 8V at no load & VMAX. How to select optimum bias voltage for designs & what should be the ideal value in such case?

Secondly, we are also looking to design 5Volt - 40Amp & 5Volt - 60Amp circuits as well. Therefore, can you please guide us as to which PI Value to use for these designs?

AWaiting your earnest reply

Your PIXL look ok. the PIXL prdict the voltage stress on device. YOu can also refer to design example examples on our website for similar device choice.

high frequency can end up with lower transformer size. lower frequency could results in higher efficiency, but need to verify on board.

bias voltage will be lower at no load or light load, higher at full load. you need to design your bias voltage at no load still meet the bias requirement. start with 12V as recommended, test it on board with bias votlage at no load and full load, iteration with more or less turns if needed.

for 40A and 60A design, possible selection coudl be bigger size TOP, LCS and TFS2, also could use PFC stage,

https://ac-dc.power.com/products/hiper-family/hiperpfs-4/

https://ac-dc.power.com/products/hiper-family/hiperlcs/

https://ac-dc.power.com/products/hiper-family/hipertfs-2/

Hello, PI-Neela

Thank you for confirming details about my PIXL. I made some changes in it after your comments & I have switched to 132KHz frequency.

Some points that I would like to have clarity on:
1. As the heatsink type is external, how to calculate the exact size of heatsink for Topswitch & output diodes? What should be the temperature limit for them at full load?

2. The VDS value (TOPswitch on state drain to source voltage) is set by default as 10Volt. Do I have to modify it in any way or is it fine just like that?

3. I would like to use copper wire instead of copper foil at output winding. Which gauge to use & how many parallel strands to have for 5Volt - 20Amp output? Please note the copper wire I would be using is not triple insulated.

4. The question of values for output diode remains unclear. If I am not wrong then to select the optimum diode value, PIVS (output recitifer peak inverse voltage) & ISP (Peak secondary current) are taken into consideration. For this design, PIVS = 24Volts & ISP = 62.43 Amps. So, does this mean I can use 2 pieces of Schottky diode 30Amp - 45Volt (TO-220 package) in parallel for this application?

5. The last thing I would like your help with is how to find out the values of output capacitors to use in this design? The output capacitor rms ripple current is 20.74Amp so how to calculate what value of capacitor (unit in mfd) to use for this design?

Hello Kunal ,

Please see below :

Some points that I would like to have clarity on:
1. As the heatsink type is external, how to calculate the exact size of heatsink for Topswitch & output diodes? What should be the temperature limit for them at full load?

The Heat Sink size is designed how much thermal resistance you need for the package. Calculate the loss disspation of TopSwitch and Output diodes , Based on Theta(JA) of the datasheet , calculate the temperature rise and design the external Heat Sink.  Generally the temperature should be less than 90 with the heat sink.It depends on Application

2. The VDS value (TOPswitch on state drain to source voltage) is set by default as 10Volt. Do I have to modify it in any way or is it fine just like that?

It's Just fine

3. I would like to use copper wire instead of copper foil at output winding. Which gauge to use & how many parallel strands to have for 5Volt - 20Amp output? Please note the copper wire I would be using is not triple insulated.

Use unserved litz wire for 20A Output , The guage should 38 X 250

4. The question of values for output diode remains unclear. If I am not wrong then to select the optimum diode value, PIVS (output recitifer peak inverse voltage) & ISP (Peak secondary current) are taken into consideration. For this design, PIVS = 24Volts & ISP = 62.43 Amps. So, does this mean I can use 2 pieces of Schottky diode 30Amp - 45Volt (TO-220 package) in parallel for this application?

Yes , Since you have high secondary peak currents , it's better to use 50A diodes in Parallel

5. The last thing I would like your help with is how to find out the values of output capacitors to use in this design? The output capacitor rms ripple current is 20.74Amp so how to calculate what value of capacitor (unit in mfd) to use for this design?

You have use multiple capacitors in Parallel because you habe high ripple current , Select the Capacitors which are rated for higher ripple current than 20.74 A and also how much output ripple you required for your design .

I=Cdv/dt , use this equation and also how much voltage undershoot and overshoor required for your specs for transient response.

Regards,

KSAN