Electronic ballast and lighting fixture

• US 20040051478A1
• Filed: 06/06/2003
• Published: 03/18/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: Toshiba Lighting & Technology Corporation (Toshiba Corporation)
• Original Assignee: Toshiba Lighting & Technology Corporation (Toshiba Corporation)
• Inventors: Otake, Hirokazu, Terasaka, Hiroshi, Takahashi, Koji, Kozuka, Hideo
• Granted Patent: US 6,784,626 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 41/3925 by frequency variation H05B41/3922 takes precedence

Abstract

An electronic ballast comprises a direct current power supply configured to provide a direct current voltage.

A switching circuit, including first and second switching elements, is connected in parallel with the direct current power supply, and is configured to convert the direct current voltage to a high-frequency alternating current.

A load circuit, including a discharge lamp, a resonance inductor, and a resonance capacitor, is operated by the high-frequency alternating current. A driving circuit is arranged between the switching circuit and the load circuit.

A driving circuit is provided with feedback windings magnetically connected to a detecting winding of the current transformer. A driving circuit is configured to control a switching frequency of the first and second switching elements according to a detected current of the detecting winding.

A magnetic energy control means is configured to control a magnetic energy of the current transformer.

A current detecting means detects an average current either an output current of the direct current power supply or a current of the switching circuit.

A current control means is configured to control the magnetic energy control means, and to fix the average current to a designated value.

Claims

1. An electronic ballast, comprising:

a direct current power supply configured to provide a direct current voltage;

a switching circuit, including first and second switching elements, connected in parallel with the direct current power supply, configured to convert the direct current voltage to a high-frequency alternating current;

a load circuit, including a discharge lamp, a resonance inductor, and a resonance capacitor, being operated by the high-frequency alternating current;

a driving circuit, arranged between the switching circuit and the load circuit, provided with feedback windings magnetically connected to a detecting winding of the current transformer, and configured to control a switching frequency of the first and second switching elements according to a detected current of the detecting winding;

a magnetic energy control means, configured to control a magnetic energy of the current transformer;

a current detecting means detecting an average current either an output current of the direct current power supply or a current of the switching circuit; and

a current control means, configured to control the magnetic energy control means, and to fix the average current to a designated value.

2. An electronic ballast, comprising:

a direct current power supply configured to provide a fixed direct current voltage;

a switching circuit, including first and second switching elements, connected in parallel with the direct current power supply, configured to convert the direct current voltage to a high-frequency alternating current;

a load circuit, including a discharge lamp, a resonance inductor, and a resonance capacitor, being operated by the high-frequency alternating current;

a driving circuit, provided with a detecting winding of a current transformer, and configured to control a switching frequency of the first and second switching elements according to a detected current of the detecting winding;

a magnetic energy control means, including a base of a transistor, configured to control a magnetic energy of the current transformer;

a current detecting means detecting an average current either an output current of the direct current power supply or a current of the switching circuit; and

a current control means, configured to control the magnetic energy control means and to fix the average current to a designated value, provided with a comparator, wherein the comparator compares a voltage signal of the average current with a reference voltage, and its output supplies to a base current of the base of the transistor.

3. A lighting fixture, comprising:

a body;

lamp sockets, constructed and arranged on the body; and

an electronic ballast, comprising;

a direct current power supply configured to provide a direct current voltage;

a switching circuit, including first and second switching elements, connected in parallel with the direct current power supply, configured to convert the direct current voltage to a high-frequency alternating current;

a load circuit, including a discharge lamp, a resonance inductor, and a resonance capacitor, being operated by the high-frequency alternating current;

a driving circuit, arranged between the switching circuit and the load circuit, provided with feedback windings magnetically connected to a detecting winding of the current transformer, and configured to control a switching frequency of the first and second switching elements according to a detected current of the detecting winding;

a magnetic energy control means, configured to control a magnetic energy of the current transformer;

a current detecting means detecting an average current either an output current of the direct current power supply or a current of the switching circuit; and

a current control means, configured to control the magnetic energy control means, and to fix the average current to a designated value.