Importance

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Abstract

The present invention is directed to a novel converter for interposition between an AC power source and a DC load capable of maintaining a substantially unity power factor independent of the impedance of the load. According to the invention, the converter has rectifying circuit to provide DC power to a DC power output circuit from an AC source, circuit for varying the impedance seen by the AC source in the DC output circuit, and circuit responsive to a shift in AC input current away from an in-phase relation with the voltage of the AC source under loading of the DC power output circuit for controlling said impedance varying circuit in a direction to return the AC current towards in-phase relation with the AC voltage. More particularly, according to the preferred form of the invention, the circuit for varying the impedance seen by the AC source in the DC output circuit includes a resonant circuit interposed between the rectifying circuit and the DC output circuit and connected to deliver DC power thereto. The converter includes a control circuit responsive to the DC voltage of the DC output circuit and the phase between the AC voltage and AC current. The control converter also includes a variable impedance responsive to the resonant circuit current for controlling the phase angle between the resonant circuit current and voltage across the resonant circuit.

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First Claim