Patent ID: 7791054

Claim:
A photo controller circuit comprising: an output switching (OS) circuit comprising an alternistor for controllably completing and interrupting a power supply path between a power source and a load, and an optoisolator connected to the power source and to the alternistor for controllably gating the alternistor; a light to voltage converter (LVC) circuit for detecting incident light and generating a direct current (DC) voltage proportional to the detected incident light; a hysteresis control (HC) circuit comprising a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit, the state of the OS circuit being one of active to power on the load and inactive to power down the load; and an intermediate switching (IS) circuit operable to controllably turn on and provide current to activate the optoisolator when the output of the HC circuit indicates the detected incident light is below a first selected level and the IS circuit was off, and to controllably turn off and reduce the current to deactivate the optoisolator when the output of the HC circuit indicates the detected incident light is above a second selected level and the IS circuit was on.