A power supply for an image intensifier of a night vision device is disclosed. The power supply comprises a battery, a memory, and a processor. The processor is configured to turn off a switch via which a voltage is supplied to a photocathode of the image intensifier in response to current drawn by an anode of the image intensifier. The processor is further configured to store, as a stored voltage value, a value of the voltage in the memory. The processor is further configured to turn on the switch and re-apply a voltage to the photocathode in accordance with the stored voltage value after a first predetermined period of time. The processor is further configured to enable an automatic brightness control procedure using the stored voltage value.