This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC27282: Any problems with negative voltage as half-bridge system ground?

Part Number: UCC27282
Other Parts Discussed in Thread: UCC27531

Hi everyone

I am thinking of a circuit like this:

The system which is controlling the driver is referenced to GND. The -10V are referenced to GND too. Of course the signals at the control pins need to be prepared so that they go down to -10V when low.

1. Is there any problem with the negative voltage level on VSS? 

2. Are there any better solutions to drive a half-bridge with a negative voltage on the negative supply terminal?

Thank you for your help.

Best regards

  • Hello Robin,

    For this implementation, there will be a voltage level shifter required for the driver input signals. There is an application note that shows the UCC27531, low side driver, with a negative gate drive bias and level shifter. This same circuit can be applied to the UCC27282.

    The application note can be found here:

    https://www.ti.com/lit/an/slua994/slua994.pdf?ts=1610639915997&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FUCC27531

    For the VDD I see 3.3V applied with -10V on VSS, please confirm that VDD to VSS will be 13.3V.

    Confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

  • Hello Richard

    Thank you so much for your fast reply. This really answered my questions. But I would like to ask you two more questions:

    1. So basically the circuit of this apploication note can be used with any half-bridge driver if the VDD to VSS voltage is as specified? There are no other parameters which need to be checked for the negative VSS?

    2. I need to operate multiple half-bridges in parallel, drived from one single PWM signal. Ideally all the IGBT/FET should switch at the same time. But a lot of drivers have really big dead time or propagation delay tolerances so that theoretically there could be a big difference in switching time of each IGBT/FET. Are there any drivers which have really small timing tolerances to meet time critical requirements?

    Best regards 

  • Hello Robin,

    For the 1st question, you need to make sure that the total voltage, positive bias plus negative bias is within the recommended operating range of the gate driver VDD to VSS rating. For example a driver with 16V rating operating with +10V and -5V will have a total of 15V applied to the driver VDD to VSS pins.

    The example you show is with 3.3V applied to VDD and -10V to VSS which is 13.3V which is OK from the driver rating. You need to confirm if driving +3.3V to the MOSFET is adequate since it sounds low.

    For the delay concerns, The UCC27282 has 16ns typical prop delays and a maximum of 30ns so the variance in delays will not be significant. There is no internal dead time in this driver, although there is interlock which will prevent LO and HO from being on at the same time.

    Confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

  • Hello Richard

    Thanks again for your fast and helpful response. This answered all my questions.

    Thanks again for your help.

    Best regards