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Overvoltage protection of current source

Recently, we are doing overvoltage protection of voltage-controlled current sources, hoping to cut off the power supply when the load is overvoltage. However, the current solution is implemented by using a comparator and an analog switch. When no overvoltage occurs, the function is normal, but when an overvoltage occurs, the power supply is repeatedly turned on and off because the overvoltage detection loop is not cut off, causing the load current to oscillate. I hope to get some suggestions. ,thanks.

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  •        Hello, consider the simplest case. When there is no overvoltage, the DAC power supply is normally supplied (currently available); when an overvoltage occurs, the output of this current source is cut off, and the above functions are repeated when the voltage of the DAC is reset the next time.
           My current idea is to add a latch after the comparator to realize the EN function of turning off the analog switch, but I have not found a suitable device and simulation.

  • Hi,

    A few more questions:

    • What is the normal voltage levels?
    • Is there a tolerance for the overvoltage (like a diode drop, 0.7 V), or is it any voltage above the normal levels?
    • What is the typical current through the switch?
    • Is the DAC reset a power cycle then?

    Yours sincerely,


  • 1. The normal voltage level is lower than 10V. It is currently set by the hysteresis comparator in the simulation diagram. In the previous diagram, VIH = 9.8V, VIL = 9.2V (simulation example, can be set by VCC 24V power supply resistor divider. Certainly)
    2. A little tolerance is allowed for overvoltage.
    3. Since the current switch is connected to the pre-DAC voltage, the maximum current should be tens of mA.
    4. What I currently consider is that if the DAC outputs a voltage, the voltage-controlled current source will cut off the output of the current source after the load overvoltage occurs. After the next DAC voltage setting, repeat judgment is the above process.                                                                                                                                
    Thank you very much for your reply, and I have also sent you the simulation diagram.