Low Voltage Disconnect Circuit

Low Voltage Disconnect circuit are used to disconnect the battery to the load when the battery voltage drops to certain level. This avoids further discharging of the battery. This is very useful for devices that uses rechargeable batteries.

About the Circuit

The circuit is simple, it only uses a comparator that compares the voltage from a zener diode and from a voltage divider with the input tap into the battery. When the +input becomes higher than the zener diode voltage, the output of the comparator turns on and it turns on Q1 . It will the pull down D1 to ground and it will pull down the voltage at -input via R4. This will create a lower turn off voltage, this effect is called the hysteresis. This is done to avoid the circuit from oscillating when the input voltage is just equal to the threshold voltage.


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