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TPS92640: About OVP

li darren
Intellectual 520 points
Part Number: TPS92640

Hi,

TPS92640 was used in some project, 50V/6A, 5V/20A, 12V/10A etc. there are the same issue in them. Such as, setting ovp voltage is 54V, when output voltage is greater than 51V, the output current decrease slowly,  it will shut down until 54V, and switching waveform became chaotic.

Please give me a suggestion.

Below is 5V/20A data, Input voltage is 12V, OVP  is set 7.5V.

7,59V     0A

7.5V        0.962A

7.0V        11.419A

6.6V         19.931A

6V            19.977A

5V             2.048A 

Below is Vout ripple.

, 

  • 0
    TI__Mastermind 25500 points

    Hello,

    Are you actually forcing the output voltage high? If so that is probably normal operation. The OVP can be tripped at a lower value if you have any noise on the output voltage. The OVP will act like that if you are forcing the load to a greater voltage. The device will turn off until the voltage falls enough (130mV hysteresis) then turn back on again. This causes a large output current ripple and lowers the output current average. If it gets high enough (because you are forcing it) it will eventually not turn on again.

    OVP is really meant to protect the output capacitor and shunt FET (if used) if the LED string opens. It isn't intended for normal operation or it will behave as you see. Generally for a 5V output you would use a 10V or higher output cap, so you would set OVP at 10V (or higher) so that if there is an LED open those components would be protected. Generally you do not want to have it very close to the operating voltage, particularly if you have extra noise due to layout or very low (or no) output capacitance where spikes on Vout could trip it prematurely.

    Regards,

    Clint