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LTC4357 Solar Panel Charging 12V Battery Through Ideal Diode to Prevent Back Feeding

Solar Panel Charging 12V Battery Through Ideal Diode to Prevent Back Feeding

In solar power systems, Schottky diodes are used to prevent discharge of the battery during hours of darkness. Unfortunately, the voltage drop and power dissipation of a Schottky diode can be quite large when used with high wattage solar panels, thus reducing the amount of power available to charge the battery. This circuit uses the LTC4357 with a FDB3632 MOSFET to replace the Schottky diode. When the solar panel is illuminated by full sunlight, it charges the battery. A shunt regulator absorbs any excess charging current to prevent overcharging. If the forward current is greater than 25mV/RDS(ON), the MOSFET is fully enhanced and the voltage drop rises according to RDS(ON) • (I BATTERY + I LOAD). In darkness, or in the event of a short circuit across the solar panel or a component failure in the shunt regulator, the output voltage of the solar panel will be less than the battery voltage. In this case, the LTC4357 shuts off the MOSFET, so the battery will not discharge. The current drawn from the battery into the LTC4357’s OUT pin is only 7μA at 12V.




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