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TPS92512HV: How to bleed off output capacitor quickly when device is powered off?

Brian Josel
Intellectual 320 points
Part Number: TPS92512HV

Using an LED string of 12 LEDs, with a forward voltage of 3.15V (Vout = 38.1V), at a certain point the LEDs don't conduct and there is a large amount of charge in the output capacitor.  Is there a way to use a bleed off resistor in parallel with the output capacitor or from Vout to GND to allow for the capacitor to bleed off its charge after the IC is powered off WITHOUT ruining the LED ripple current or regulation capability?

  • 0
    TI__Mastermind 28655 points
    Hello Brian,

    This can be done with external circuitry. A MOSFET and resistor across the output that switching on when power is removed as long as it means the SOA of the MOSFET and pulse capability of the resistor. This has to be done carefully since you don't want the MOSFET on when the Buck converter is on. If it can be bled down slow maybe a higher value resistor across the LEDs that doesn't draw too much current can be used.

    Best Regards,