High power factor electronic transformer system for gaseous discharge tubes
First Claim
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1. A high power factor electronic transformer system for use with a rectifier, comprising:
- an inverter circuit connected to a rectified voltage from the rectifier for producing a high-frequency voltage therefrom;
a first capacitor connected across a first input terminal and a second input terminal of said inverter circuit;
an inductor connected between the first input terminal of said inverter circuit and a first output terminal of the rectifier and a second output terminal of the rectifier being connected to said second input terminal of said inverter circuit;
switch means with an open state and a closed state;
said inverter circuit including a transformer having a secondary winding connected to a load and a primary winding connected at one end to said first input terminal of said inverter circuit and at a second end to said switch means;
a second capacitor connected in parallel with said switch means; and
control means for controlling said switch means so that a sinusoidal input current input to the rectifier remains substantially sinusoidal.
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Abstract
A cost-effective apparatus to improve the power factor of an AC line powered electronic transformer for powering gaseous discharge tubes uses an L-C filter link between a rectifier that provides DC voltage and an inverter for converting from DC to AC. The L-C filter link and the inverter function as a power factor correction stage, while at the same time converting DC voltage to AC voltage to drive gaseous discharge tubes.
75 Citations
12 Claims
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1. A high power factor electronic transformer system for use with a rectifier, comprising:
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an inverter circuit connected to a rectified voltage from the rectifier for producing a high-frequency voltage therefrom; a first capacitor connected across a first input terminal and a second input terminal of said inverter circuit; an inductor connected between the first input terminal of said inverter circuit and a first output terminal of the rectifier and a second output terminal of the rectifier being connected to said second input terminal of said inverter circuit; switch means with an open state and a closed state; said inverter circuit including a transformer having a secondary winding connected to a load and a primary winding connected at one end to said first input terminal of said inverter circuit and at a second end to said switch means; a second capacitor connected in parallel with said switch means; and control means for controlling said switch means so that a sinusoidal input current input to the rectifier remains substantially sinusoidal.
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2. A high power factor electronic transformer system for a gaseous discharge tube, comprising:
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a rectifier circuit connected to an alternating current voltage source and producing a rectified voltage therefrom; an inverter circuit having positive and a negative input terminals and including a transformer for producing a high-frequency voltage; an inductor connected between a positive output terminal of said rectifier circuit and said positive input terminal of said inverter circuit; a first capacitor connected across said positive and negative input terminals of said inverter circuit; a semiconductor control switch; said transformer having a secondary winding connected to provide the high-frequency voltage to the gaseous discharge tube and a primary winding connected at one end to said positive input terminal of said inverter circuit and at a second end to a drain of said control switch; a source of said control switch connected to said negative input terminal of said inverter circuit and to said first capacitor; a second capacitor connected between said drain and said source of said semiconductor control switch; and means for controlling said semiconductor control switch connected to a gate of said switch, wherein an inductance of the transformer, a capacitance of the second capacitor, and a switching frequency of the means for controlling are chosen so that the semiconductor control switch will conduct electricity between the drain and the source when a voltage across the drain and the source is at a minimum, and whereby a sinusoidal input current input to said rectifier circuit remains substantially sinusoidal. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification