Importance

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Abstract

A control circuit ideally suited for a capacitor charging circuit (100) that uses an apparent measure of current flow through a circuit line to regulate current drawn from a battery through the circuit line is disclosed. A summing circuit (136) produces a difference voltage (138) of the battery voltage (152) subtracted from a threshold reference voltage (151). The difference voltage (138) is subsequently amplified by an amplifier (140), rectified by a diode (142), and added to a voltage measure (130) from a current-sense resistor (117) by a summing circuit (128). The resulting voltage measure (126) is an apparent measure of current flow and is provided to a charge controller (122) which regulates current flow through a transformer (107) by controlling the operation of a switch (108). As the voltage on the battery (102) decreases below the reference voltage set by voltage source (150), the increasing difference voltage (138) adds bias to the actual measure of current flow (130), thus providing the charge controller (122) with an apparent measure of current flow through the transformer (107) that is higher than the actual level of current flow. The charge controller is thereby deceived and reduces the current drawn from the battery through the transformer.

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First Claim