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TL431: Circuit Diagram from Low and High Voltage Cut Off

jagdish controls
Prodigy 140 points
Part Number: TL431
Other Parts Discussed in Thread: TL1431

Dear Team,

I have designed LED Driver using FL7733 IC from Fairchild.

The Driver is working well. But I want to add extra protection by adding Low Input Voltage ( 120V AC) & High Input Voltage (275V AC) Cut-off using IC TL431.

My requirement is -Whenever the Input Voltage is from 0 - 120V AC & Above 275V AC ( Both Conditions to be considered), the Output of TL431 should be able to provide GND for the VDD Pin of  IC FL7733.

Please help in this regards.

  • 0
    TI__Mastermind 24485 points
    Hello,

    Using the TL431 will shunt any current so that the cathode is fixed to the desired voltage set by the voltage reference equation in the datasheet.

    How are you intending on using it as a cutoff?

    Here is a post where another person was implementing something similar with a TL1431, which would be functionally the same:

    e2e.ti.com/.../535858
    You can use the TL431 as long as the cathode voltage of the device never exceeds 36V, and the cathode current never exceeds 100mA.

    Additionally, if you have high currents and voltages you need to consider thermals as well to ensure the device does not heat up beyond absolute maximum operating conditions.

    Best,
    Michael