Voltage resonance inverter circuit for dimable cold cathode tubes

• US 5,666,279 A
• Filed: 11/22/1995
• Issued: 09/09/1997
• Est. Priority Date: 11/24/1994
• Status: Expired due to Term

• Current Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Original Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Inventors: Okada, Shingo, Takehara, Takao
• Primary Examiner(s): Sterrett, Jeffrey L.
• Application Number:
  US08/562,178
• Time in Patent Office: 657 Days
• Field of Search: 363/15, 363/16, 363/95, 363/97, 363/131
• US Class Current: 363/95
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 41/2824 using control circuits for the switching element H05B41/2822 takes precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An object of the present invention is to provide a voltage resonance inverter circuit capable of performing constantly a zero-voltage switching action in response to a change in the input voltage. For achievement of the above object of the present invention, the capacitance of a voltage resonance capacitor is decreased in response to an increase of the input voltage thus increasing the characteristic impedance of a resonance circuit. This will increase the amplitude of a resonance voltage causing a zero-voltage switching action.

Claims

1. A voltage resonance inverter circuit having a serial resonance circuit provided at a primary side of a booster transformer, a controller circuit for turning on and off the serial resonance circuit by conducting a switching element at the timing of phase advanced from the resonance frequency of the serial resonance circuit, and a load provided at a secondary side of the booster transformer, comprising:

a comparator for detecting an input voltage of the voltage resonance inverter circuit;

a switch circuit for switching the frequency of the resonance circuit; and

a controlling means for shifting a resonance frequency of the resonance circuit to a higher rate when the input voltage is higher.

2. A voltage resonance inverter circuit according to claim 1, wherein the load provided at the secondary side of the booster transformer is a cold cathode tube.

3. A voltage resonance inverter circuit according to claim 1, wherein the switch circuit for switching the resonance frequency of the resonance circuit is a circuit for changing a capacitance of a capacitor.

4. A voltage resonance inverter circuit according to claim 1, wherein the switch circuit for switching the resonance frequency of the resonance circuit is a circuit for changing an inductance.