PMP10532: Isolated DC-DC converter minimum load

Jacopo Agostini

Intellectual 390 points

Part Number: PMP10532
Other Parts Discussed in Thread: LM5160,

Hi,

I wanted to use the reference design PMP10532 where LM5160 and a transformer are used to generate +15-15 and 5V.

Why a minimum load, after the transformer, represented by R4, R5 and R6, is needed?

Thanks

over 5 years ago

0 Robert Taylor1 over 5 years ago

TI__Expert 5455 points

Hi Jacopo,

The resistors are needed to prevent the outputs from floating up when there is no load. Basically they are just there for cross regulation purposes during different loading conditions.

Thanks,
Robert

0 Jacopo Agostini over 5 years ago in reply to Robert Taylor1

Intellectual 390 points

Hi,

thank for the answer.

I wanted to understand the physical reason. I read that transformer output can go up when there is no load, basically because of leakage inductance. Is it correct?

0 Robert Taylor1 over 5 years ago in reply to Jacopo Agostini

TI__Expert 5455 points

Yes that is correct, the leakage can cause the output to rise. It also happens because the outputs are not directly regulated, the regulation is done on the primary side.

Thanks,

Robert

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PMP10532: Isolated DC-DC converter minimum load