DRV8412: Opposite high-bridge turning on spontaneously

David Kraeutmann

Part Number: DRV8412

When running at close to 50V, the opposite high-bridge turns on spontaneously and only turns off when the CBC limit kicks in. I've attached some scope screenshots; the top two traces are OUT_A, OUT_B on the DRV8412DDWEVM and the bottom two are PWM_A/PWM_B.

over 4 years ago

0 Wang5577 over 4 years ago

TI__Guru 56650 points

David,

Would you help me clarify “opposite high-bridge”?

Also, can you compare the input signal with the output signal? What output waveform do you expect?

0 David Kraeutmann over 4 years ago in reply to Wang5577

Prodigy 70 points

The opposite half-bridge is "A" turning on I'm switching "B" when A+B are in a full-bridge configuration, and vice versa.

The input waveform is given in the oscilloscope screenshots as the bottom two waveforms, with each color corresponding to the appropriate output waveform.

I changed the output transformer (I had a suspicion that the previous transformer was saturating) and the problem disappeared. However, I'm still wondering why it happened in the first place.

Quick schematic:


A --- 4.7uH ----|-----|   |------ |
               68nF    XFER       load (ultrasonic transducer at resonance)
B --- 4.7uH ----|-----|   |------ |

I've annotated one of the screenshots

0 Wang5577 over 4 years ago in reply to David Kraeutmann

TI__Guru 56650 points

David,

Great! You found the previous transformer saturate issue.

"However, I'm still wondering why it happened in the first place." Do you mean the transformer saturation?

If you have more questions, you can reopen this post by posting your questions in this thread.

Motor drivers

Motor drivers forum

DRV8412: Opposite high-bridge turning on spontaneously