DC/AC and DC/DC power supply for LCD displays

• US 6,879,111 B2
• Filed: 05/29/2002
• Issued: 04/12/2005
• Est. Priority Date: 05/29/2002
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Voto, Andrew Michael, Voto, Robert Martin
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): VU, JIMMY T
• Application Number:
  US10/157,648
• Publication Number:
  US 20030222631A1
• Time in Patent Office: 1,049 Days
• Field of Search: 315/169.1, 315/169.3, 315/169.4, 315/224, 315/291, 315/209.R, 315/307, 315/DIG.5, 363/97, 363/56, 363131-132, 363/20
• US Class Current: 315/169.3
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 7/5381 Parallel type
• CPC Class Codes: H05B 41/2821 by means of a single-switch converter or a parallel push-pull converter in the final stage H05B41/285 takes precedence

Abstract

A voltage power supply circuit is provided that uses the voltage output of an oscillator to provide a high voltage DC output to drive a liquid crystal display device. A controller IC opens and closes an FET to allow the EMF of an inductor to generate a DC voltage that exceeds the battery voltage source for the liquid crystal display device. Accordingly, the oscillator circuit that drives a back light display for a liquid crystal device is simultaneously used to generate the high voltage DC source for the liquid crystal display device.

Claims

1. A voltage power supply circuit comprising:

an oscillator circuit that provides a voltage output;

an inductor in series with the voltage output of the oscillator circuit;

a switch positioned in series with the inductor and the voltage output of the oscillator circuit, the switch being positioned between the inductor and a ground;

a DC circuit electrically connected to a high potential side of the switch; and

a battery voltage source supplying voltage to the oscillator circuit;

wherein the inductor generates an EMF when the switch does not conduct to create a voltage in the DC circuit that exceeds a voltage level of the battery voltage source.

2. The voltage power supply circuit as claimed in claim 1, further comprising a clamping circuit that clamps a voltage output by the DC circuit to a voltage fixed relative to the voltage supplied by the battery voltage source.

3. The voltage power supply circuit as claimed in claim 1, wherein the switch is a FET.

4. The voltage power supply circuit as claimed in claim 3, further comprising a controller IC, the controller IC driving the FET to an open and closed condition.

5. The voltage power supply circuit as claimed in claim 1, wherein the oscillator circuit is a Royer type oscillator.

6. The voltage power supply circuit as claimed in claim 1, further comprising an AC voltage circuit, the oscillator driving the AC voltage circuit.

7. The voltage power supply circuit as claimed in claim 6, wherein the AC voltage circuit drives a cold cathode fluorescent lamp for a liquid crystal display.

8. The voltage power supply circuit as claimed in claim 1, wherein the DC circuit further comprises a high voltage DC output and a low voltage DC output.

9. The voltage power supply circuit, as claimed in claim 8, further comprising:

a high side liner regulator regulating a voltage of the high voltage DC output; and

a low side linear regulator regulating a voltage of the low voltage DC output.

10. A voltage power supply circuit as claimed in claim 8, further comprising a high side charge capacitor that stores a voltage generated by the EMF and provides the stored voltage to the high voltage DC output.

11. The voltage power supply circuit as claimed in claim 9, further comprising:

a coupling capacitor positioned between the low voltage DC output and the low side linear regulator, the coupling capacitor inverting the EMF voltage; and

a low side charge capacitor storing an inverted voltage from the coupling capacitor, the low side charge capacitor providing the inverted voltage to the low side linear regulator.

12. The voltage power supply circuit as claimed in claim 1, wherein the DC voltage circuit drives a biasing voltage across an LCD glass of a liquid crystal display system.

13. A voltage power supply circuit for a liquid crystal display system comprising:

a Royer oscillator having a voltage output;

an inductor in series with the voltage output of the Royer oscillator;

a FET in series with the inductor and the voltage output, the FET positioned at a low potential side of the inductor;

a controller IC controlling voltage supplied to a gate of the FET for turning the FET on and off at a predetermined frequency;

a DC voltage circuit electrically connected to a position between the inductor and the FET;

an AC voltage circuit driven by the Royer oscillator;

a cold cathode fluorescent lamp driven by the AC voltage circuit;

ac LCD glass, a voltage across the LCD glass being selectively driven by the DC circuit;

a battery voltage source supplying battery voltage to the Royer oscillator; and

a clamping circuit connected between the DC voltage circuit and the battery voltage source that clamps the DC voltage circuit to a level above a voltage level of the battery voltage source;

wherein EMF generated by the inductor when the controller IC closes the FET generates a voltage in the DC voltage circuit that exceeds the voltage level of the battery voltage source.

14. An improved voltage power supply for a liquid crystal display device of the type that provides a DC voltage across an LCD glass and an AC voltage to drive a back light display for the liquid crystal display device, the improvement comprising:

an oscillator circuit that provides a voltage output and drives an AC circuit;

an inductor in series with the voltage output of the oscillator circuit;

a switch positioned in series with the inductor and the voltage output of the oscillator circuit, the switch being positioned between the inductor and a ground;

a DC circuit electrically connected to a high potential side of the switch; and

a battery voltage source supplying voltage to the oscillator circuit;

wherein the inductor generates an EMF when the switch does not conduct to create a voltage in the DC circuit that exceeds a voltage level of the battery voltage source.

15. The improvement as claimed in claim 14, further comprising a clamping circuit that clamp the DC circuit to the battery voltage source, the clamping circuit clamping a voltage of the DC circuit to a level above the battery voltage source.

16. The improvement as claimed in claim 14, wherein the switch is a FET.

17. The improvement as claimed in claim 16, further comprising a controller IC, the controller IC driving the FET to an open and closed condition.

18. The improvement as claimed in claim 14, wherein the oscillator circuit is a Royer type oscillator.

19. The improvement as claimed in claim 14, wherein the AC voltage circuit drives a cold cathode fluorescent lamp for the liquid crystal display.

20. An LCD device comprising:

a voltage power supply circuit for generating a high AC voltage and a high DC voltage to a liquid crystal display of the LCD device, the voltage power supply circuit comprising;

an oscillator circuit tat provides a voltage output;

an inductor in series with the voltage output of the oscillator circuit;

a switch positioned in series with the inductor and the voltage output of the oscillator circuit, the switch being positioned between the inductor and a ground;

a DC circuit electrically connected to a high potential side of the switch; and

a battery voltage source supplying voltage to the oscillator circuit;

wherein the inductor generates an EMF when the switch does not conduct to create a voltage in the DC circuit that exceeds a voltage level of the battery voltage source.