Low burden visual power-on indicator for a self-powered circuit protection device

摘要

The present invention provides a low burden visual POWER ON indicator for a self-powered electrical circuit protection device. The visual indicator includes a current transformer for producing an induced current in direct proportion to the current supplied to an electrical device protected by the protection device. The induced current is summed and rectified. An energy accumulator stores a predetermined voltage required to operate the protection device. The stored voltage is controlled by an accumulation switch which in turn is controlled by a hysteresis control circuit. The hysteresis control circuit includes an operational amplifier which is biased by a stable reference voltage. When the voltage on the energy accumulator is equal to the stable reference voltage the operational amplifier produces a HIGH output signal. When the voltage on the energy accumulator is less than the stable reference voltage the operational amplifier produces a LOW output signal. A HIGH output signal causes the power accumulation switch to close thereby diverting current away from the energy accumulator. A LOW output signal opens the power accumulation switch causing current to flow to the energy accumulator thereby charging it. An LED is electrically connected to the operational amplifier such that it is illuminated only when the operational amplifier produces a HIGH output signal and thereby provides a visual indication of the POWER ON state of the protection device.