LM5181: LM5181 Secondary current detect theory

Shuang Feng76

Expert 3310 points

Part Number: LM5181

Hi,

here we want to understand the theory of the secondary current detect.

below we described the BCM mode, we could detect the secondary current to turn on the MOSFET when the current is 0.

could you help to clarify how could our device detect the secondary current into zero?

thanks a lot.

over 3 years ago

+1 Elena Gao over 3 years ago

TI__Genius 13735 points

Hi, Shuang,

I have found a plot as below, this is detecting the voltage slew rate change when ID current reach to zero., below marking should be Vo *Np/Ns for LM5181, please check if this can help you understanding.

thank you.

Elena

0 Shuang Feng76 over 3 years ago in reply to Elena Gao

TI__Expert 3310 points

Thanks, it is clear.

I want to double confirm. Does it mean that our device have internal state machine could calculate and identify such voltage slew rate change?

+1 Elena Gao over 3 years ago in reply to Shuang Feng76

TI__Genius 13735 points

Hi, Shuang,

It didn't show in the block diagram, so I am not sure that's it designed like. sorry for that.

Elena

0 Shuang Feng76 over 3 years ago in reply to Elena Gao

TI__Expert 3310 points

Thanks, it is enough.

Have a nice day.

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LM5181: LM5181 Secondary current detect theory