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TPS92310 No Load and Relay Connection

Keith Keller
Expert 6240 points
Other Parts Discussed in Thread: TPS92310

Hello,

We’re using the TPS92310 LED driver in a 24Vout isolated 7s4p configuration LED configuration.

We are considering an architecture where we would keep the driver running all the time to provide housekeeping power to the subsystem, possibly through an auxiliary winding tuned to about 12V.  A relay would then switch the driver output to the LEDs.  We’re concerned about the load dump and inrush current from abruptly removing/connecting the LED array.  Is there any concern with this type of connection?

The proposed 12V winding would power a microcontroller all the time.
Does the TPS92310 have no load protection so as to clamp the output voltage to a maximum?

Thanks very much, Keith

  • 0
    TI__Mastermind 28655 points
    Hello,

    It might be possible but I don't think it will be easy and certainly not as simple as switching the LEDs in and out. This is primary side regulated and is trying to regulate LED current via internal control logic. The IC does OVP via the ZCD pin. The compensation capacitor will make the bandwidth very slow so when opening the LEDs the converter will try to feed current to the output until OVP on the ZCD pin is reached. Once detected it will shut off until VCC uvlo (you probably don't want it operating this way for a regulated bias voltage). There may also need to be some loading on the output to prevent it from slowly charging higher depending on how you use the bias in this mode. The bias voltage would need a separate rectifier so the TPS92310 can still start through the start-up resistor path.

    Also if there is a large output capacitor you don't want to switch a relay connecting in the LEDs if the voltage of the capacitor is higher than the LED stack voltage. The surge could damage the LEDs.

    Thanks,