Shunt circuit for reducing audible noise at low loading conditions of a power supply employing a high frequency resonant converter
First Claim
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1. A power supply for supplying power to an output circuit comprising:
- a resonant converter having an operating frequency which increases with increases in load current delivered to the output circuit by the power supply, the load current flowing through said resonant converter to the output circuit; and
,nondissipative shunting means coupled in parallel relative to said output circuit for automatically maintaining a current flow through said resonant converter above a level required to maintain the operating frequency above a predetermined frequency irrespective of the level of the load current, the shunting means shunting a variable portion of the current flowing in said resonant converter as the load current varies, the current shunted by said shunting means decreasing toward zero as said load current increases, and the current shunted by the shunting means increasing as said load current decreases and as said operating frequency moves toward said predetermined frequency such that the load current flowing in said output circuit would be reduced toward zero as said operating frequency moves to said predetermined frequency.
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Abstract
A power supply including a resonant converter is provided with current shunt. The current shunt automatically shunts a portion of current flowing in the resonant converter at light loading of the power supply such that output current flowing in an output circuit connected to the power supply would be reduced toward zero as the operating frequency of the converter moves to a predetermined frequency.
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Citations
23 Claims
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1. A power supply for supplying power to an output circuit comprising:
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a resonant converter having an operating frequency which increases with increases in load current delivered to the output circuit by the power supply, the load current flowing through said resonant converter to the output circuit; and
,nondissipative shunting means coupled in parallel relative to said output circuit for automatically maintaining a current flow through said resonant converter above a level required to maintain the operating frequency above a predetermined frequency irrespective of the level of the load current, the shunting means shunting a variable portion of the current flowing in said resonant converter as the load current varies, the current shunted by said shunting means decreasing toward zero as said load current increases, and the current shunted by the shunting means increasing as said load current decreases and as said operating frequency moves toward said predetermined frequency such that the load current flowing in said output circuit would be reduced toward zero as said operating frequency moves to said predetermined frequency. - View Dependent Claims (2, 3, 21)
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4. A power supply for supplying power to an output circuit comprising:
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a series resonant converter having an operating frequency which increases with increases in load current delivered to the output circuit by the power supply, the load current flowing through said resonant converter to the output circuit; and
,nondissipative shunting means coupled in parallel relative to said output circuit for automatically maintaining a current flow through said resonant converter above a level required to maintain the operating frequency above a predetermined frequency irrespective of the level of the load current, the shunting means shunting a variable portion of the current flowing in said resonant converter as the load current varies, the current shunted by said shunting means decreasing toward zero as said load current increases, and the current shunted by the shunting means increasing as said load current decreases and as said operating frequency decreases toward said predetermined frequency such that the load current flowing in said output circuit would be reduced toward zero as said operating frequency decreases to said predetermined frequency. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A UPS system for supplying AC power to a load comprising:
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rectifier means connectable to an AC utility power source; a series resonant converter coupled to said rectifier means and having an operating frequency which varies directly with variations of load current delivered to an output circuit by the power supply, at least a portion of the load current flowing through said resonant converter, said output circuit comprising an invertor connectable to a load for supplying AC power to said load; a battery connectable to the input of said converter; said converter further including an isolation transformer having a primary and a secondary winding, said transformer coupling said output circuit to said converter, and nondissipative shunting means connected in parallel relative to one of said primary or secondary windings for automatically maintaining a current flow through said resonant converter above a level required to maintain the operating frequency above a predetermined frequency irrespective of the level of the load current, the shunting means shunting a variable portion of the resonant current flowing in said converter as the load current varies, the current shunted by the shunting means decreasing toward zero as said load current increases, and the current shunted by the shunting means increasing as said load current decreases and as said operating frequency falls toward said predetermined frequency such that said load current flowing in said output circuit would be reduced toward zero as said operating frequency falls to said predetermined frequency. - View Dependent Claims (17, 18, 19)
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20. A UPS system for supplying AC power to a load comprising:
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rectifier means connectable to an AC utility power source; a series resonant converter coupled to said rectifier means and having an operating frequency which varies directly with the loading of an output circuit, said output circuit comprising an inverter connectable to a load for supplying AC power to said load; a battery connectable to the input of said converter; said converter further including an isolation transformer having a primary and a secondary winding, said transformer coupling said output circuit to said converter, and shunting means connected in parallel with said primary winding for automatically shunting a portion of the resonant current flowing in said converter as said operating frequency falls toward a predetermined frequency such that said output current flowing in said output circuit would be reduced toward zero as said operating frequency falls to said predetermined frequency.
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22. A UPS system for supplying AC power to a load comprising:
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rectifier means connectable to an AC utility power source; a series resonant converter coupled to said rectifier means and having an operating frequency which varies directly with the loading of an output circuit, said output circuit comprising an invertor connectable to a load for supplying AC power to said load; a battery connectable to the input of said converter; said converter further including an isolation transformer having a primary and a secondary winding, said transformer coupling said output circuit to said converter, and shunting means connected in parallel with one of said primary or secondary windings for automatically shunting a portion of the resonant current flowing in said converter as said operating frequency falls toward predetermined frequency such that said output current flowing in said output circuit would be reduced toward zero as said operating frequency falls to said predetermined frequency, said shunting means comprising a series arrangement of an inductive element and a capacitor, said operating frequency being between a resonant frequency of said converter and said predetermined frequency with said predetermined frequency being less than said resonant frequency. - View Dependent Claims (23)
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Specification