Patent ID: 7671665

Claim:
An electrical switching circuit for controlling current flow to an electrical load from a primary power source with a first electrical potential difference relative to a circuit ground, comprising: a primary electrical switch coupled between the primary power source and the electrical load with a control input that is responsive to a control signal of predetermined potential difference relative to the electrical load; a primary energy storage device with a low side coupled to the electrical load; a primary switch controller coupled to the primary energy storage unit with a controller output coupled to the primary switch control input that develops a controller output signal that approximates the potential difference across the primary energy storage unit in response to a controller input signal; a secondary electrical energy storage device with a high side and a low side; a controllable electrical switch that toggles the low side of the secondary energy storage device from the circuit ground to the low side of the primary energy storage device; a primary unidirectional current gate coupled between the high side of the secondary energy storage device and the high side of the primary energy storage device to let current flow from the secondary energy storage device to the primary energy storage device when the potential difference of the high side of the secondary energy storage device is higher than the high side of the primary energy storage device; a secondary unidirectional current gate coupled between a secondary power source with an electrical potential difference of at least the predetermined potential relative to the circuit ground and the high side of the secondary energy storage device to let current flow from the secondary power source to the high side of the secondary energy storage device when the potential difference of the secondary power source is higher than the high side of the secondary energy storage device; wherein periodic operation of the secondary electrical switch charges the secondary energy storage device when the secondary switch toggles its low side to the circuit ground and the secondary energy storage device charges the primary storage device when the secondary switch toggles its low side to the low side of the primary energy storage device.