Ambient light sensitive automatic flash control circuit

摘要

A flash control circuit for a camera flash circuit in which a scene ambient light sensing circuit is coupled to the main flash capacitor which serves as the sole energy source for the light sensing circuit independent of the battery source. The ambient light sensing circuit comprises a light sensing device and resistor coupled in series across a zener diode which serves as a fixed voltage reference device for the light sensing circuit. In a preferred embodiment, the ambient light sensing circuit is coupled in series with the flash sync switch across the flash capacitor such that activation of the light sensing circuit occurs only while the sync switch is closed.