LM5022: Reference Design of LM5022, PMP9446

Kuan Wei Chen (Kevin Chen)

Part Number: LM5022
Other Parts Discussed in Thread: PMP9446, PMP

Dear Team,

My customer want to use this reference design for Vin=12V, Vo=54V, Io=0.5A

I found some question on it:

1. The transformer turn ratio is 6:24, so the maximum Vo should be 48V right? Even Duty=100%, I still don't think 12Vin will have 54Vo.

2. For the secondary side diode, why you use 600V/10A rating?

Base on my understanding, this reference design is for 54V/0.75A output. So diode reverse voltage should be 12*4+54=102. Diode average current should be 0.75A.

Kevin

over 5 years ago

0 Youhao Xi over 5 years ago

TI__Guru 68595 points

Hi Kuan Wei,

Don't miss this one for buck type circuit. This is a flyback and the Vout and Vin relationship is:

Vout = D /(1-D) x Vin/k

where k is the transformer duty cycle. Theoretically it can create very high output voltage if D is approaching 100%.

The 600V diode is not necessary. I guess it was available with the designer make the board.

By the way, the PMP design was created by the PDS group and you may make a request to them to get help from them.

Best Regards,
Youhao Xi, Applications Engineering

0 Kuan Wei Chen (Kevin Chen) over 5 years ago in reply to Youhao Xi

TI__Genius 9710 points

Dear Youhao,

Thanks a lot, can you help on double check the diode's current and voltage rating?

Kevin

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LM5022: Reference Design of LM5022, PMP9446