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TL431A: SHUNT NETWORK ZENER DIODE TL431a

BERNARD TENDENGU
Prodigy 10 points

Part Number: TL431A

I am currently working on a universal solar charger eletronic circuit which I bumped into on the internet. In the circuit we do have a shunt zener diode tl431a. I need to modify the circuit to that of an led lamp driver but the problem that I do have is that the supply is dc 12 volts @ 75 amps and the other option is that I can use 12 volts @ 68 amps but my fear is on the zener shunt diode incase it may blow.If you can assist me with the modifications I can make to see to it that it does not blow up the circuit. I have also attached the circuit diagram for the universal charger. I intend to power up to 12 led lamp drivers rated at 22 watts or 32 watts.


Please if you can help me out I am stuck.

Regards

Bernard  TendenguUNIVERSAL SOLAR CHARGER.pdf

  • 0
    TI__Mastermind 24485 points
    Hello Bernard,

    This is a huge amount of power for this system. To be honest, I am not even sure if you can manage this power with the setup that you attached. At this high power, you likely need a much more advanced switching regulator topology such as a full bridge switching regulator. To me, the setup you have attached seems like a very bad idea for 800W power supply.
    You may want to check out our TIDesigns power designs to search for a design that has already been tested for such complex/high power driving.
    www.ti.com/.../refdesignsearchresults.tsp

    As for the TL431 specifically, the key is to make sure that the cathode current into the device does not exceed 100mA. In the setup shown, it should be fine. The TL431 is not sourcing any current or providing current to the load, but is simply being used to provide VCC to the LM324. The TL431 needs to be set up so that it has a minimum of 1mA cathode current at all times, and it will regulate appropriately. If the ICC of the LM324 is 10mA, then you need to make sure that the current going through the R3 is >11mA at all times so that the TL431 stays regulating.

    Additionally, having a 100nF capacitor connected to the cathode is not a good idea. This capacitance should either be very low < 2.2nF or very high >10uF, or else the output regulation of the TL431 may oscillate.

    Best,
    Michael