A self-powered photosensor switch detects only rising edge of infrared-light pulse for wireless zero-standby-power wake-up receiver

A self-powered photosensor switch that detects only the rising edge of an infrared (IR) pulse has been developed to reduce the standby current of battery-operated wireless devices with an IR remote controller and to enable removal of the external on/off switch. It consists of a VDD-rising-edge detector, an external-noise current canceller, and an IR LED energy harvester. The detector is powered by the energy harvester and detects a steep rising edge in the supply voltage. The power dissipation of the detector is kept at the picowatt level so that the detector operates only when the supply voltage passes through the sub-Vth region. The external-noise current canceller subtracts the offset current due to environmental noise. It uses a diode-connected low-Vth MOSFET to reduce the supply voltage to less than the operating voltage of the detector, and it keeps the supply voltage constant at a value determined by the constant current source of a low-Vth MOSFET in which the gate is replaced with a hold capacitor,. The photosensor switch makes possible the self-powered detection of IR light signals from a remote controller, even in the presence of environmental noise. To verify its effectiveness, a wake-up receiver containing the photosensor switch was fabricated and tested on a battery-operated wireless device. A commercial IR remote controller was able to wake the device up at a distance of 6 meters, and the standby current of the power-on controller was found to be 0.5 nA. The power dissipation of the photosensor switch was 40 pW.