UCC27424: Output pulses of UCC27424 overlap

Shashank Varshney

Part Number: UCC27424

Tool/software:

PWM pulses applied at the input terminals of UCC27424 have a deadtime of 325nsec, but the PWM pulses at the output terminals are overlapping. Can you please let me know why this is happening??

5 months ago

0 Rubas Khalid 5 months ago

TI__Expert 6735 points

Hi Shashank,

The UCC27424 does not have deadtime in the device. Do you mean that you are implementing the deadtime yourself? Can you provide waveforms of the two inputs and two outputs (at the pins of the driver)?

Thanks,
Rubas

0 Shashank Varshney 5 months ago in reply to Rubas Khalid

Prodigy 90 points

0 Rubas Khalid 5 months ago in reply to Shashank Varshney

TI__Expert 6735 points

Hi Shashank,

The deadtime on the output signals on the primary side look to be sufficient, but then it looks to be no longer sufficient on the secondary side. It looks like the secondary side output slew rate is slower, which causes the overlapping. It could most likely be because of the delays on the secondary side, so try to reduce the capacitance of C1 and C2, and see what the results are.

By the way, I see that you are using a push-pull topology to drive half-bridge. This app note may help in designing: https://www.ti.com/lit/an/slla602/slla602.pdf

Thanks,
Rubas

0 Shashank Varshney 5 months ago in reply to Rubas Khalid

Prodigy 90 points

By reducing C1 & C2 capacitor value, the pulses at the start started overlapping each other.

0 Shashank Varshney 5 months ago in reply to Shashank Varshney

Prodigy 90 points

Hello Rubas Khalid.. Thanks for sharing the document link. I have designed according to that and now I am getting correct pulses with correct deadtime. Thanks once again.

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UCC27424: Output pulses of UCC27424 overlap