SYSTEM AND METHODS FOR DIMMING A HIGH PRESSURE ARC LAMP

• US 20080036399A1
• Filed: 07/31/2007
• Published: 02/14/2008
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Olson, Scot, Pitman, Bruce
• Granted Patent: US 7,928,665 B2
• Time in Patent Office: Days
• US Class Current: 315/308
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H05B 41/2824 using control circuits for the switching element H05B41/2822 takes precedence
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: H05B 41/3921 with possibility of light intensity variations

Abstract

A driver circuit provides a drive current from a power source to an arc lamp to produce a light. The circuit includes a transformer having primary and secondary windings, with the ends of the secondary winding providing the lamp drive current to the arc lamp. A current steering module provides a drive output from the power source to the transformer in response to a current steering input, and a current control loop adjusts the current steering input in response to the current in one of the windings of the transformer. A luminance control loop adjusts the current steering input in response to the brightness of the light and a luminance command. A power control module may be further provided to generate a boost command in response to a difference between the brightness of the arc lamp and a luminance command.

Claims

1. A driver circuit for providing a drive current from a power source to an arc lamp producing a light having a brightness, the circuit comprising:

a transformer having a primary winding and a secondary winding, wherein each of the primary and secondary windings have a first and a second end and are configured to conduct an electrical current having a polarity, and wherein the ends of the secondary winding are coupled to provide the lamp drive current to the arc lamp;

a current steering module configured to provide a drive output from the power source to the transformer in response to a current steering input;

a current control loop configured to adjust the current steering input in response to the current in one of the windings of the transformer; and

a luminance control loop configured to adjust the current steering input in response to the brightness of the light.

2. The driver circuit of claim 1 further comprising a power control module coupled to the luminance control loop, wherein the power control module is configured to generate a boost command in response to a difference between the brightness of the lamp and a luminance command.

3. The driver circuit of claim 2 wherein the lamp drive current provided to the arc lamp is increased in response to the boost command.

4. The driver circuit of claim 2 wherein the power source is configured to receive the boost command and to adjust the power provided in response thereto.

5. The driver circuit of claim 2 wherein the boost command is provided to the transformer to adjust a ratio of primary to secondary windings.

6. The driver circuit of claim 2 wherein the boost command is provided to a boost coil adjacent the primary windings of the transformer.

7. The driver circuit of claim 1 further comprising a lamp frequency control loop configured to adjust the polarity of the electrical current in the primary winding in response to a signal received from the transformer to thereby adjust the frequency of the lamp drive current applied to the fluorescent lamp.

8. The driver circuit of claim 1 wherein the lamp frequency control loop comprises:

a flip-flop having a clock input, a signal input, an inverting output, and a non-inverting output, and wherein the inverting input is coupled to the signal input;

a first switch coupled to the inverting input, to a reference voltage, and to the first end of the primary winding; and

a second switch coupled to the non-inverting input, to the reference voltage, and to the second end of the primary winding;

wherein the polarity of the primary winding is adjusted by toggling the first and second switches to thereby switchably couple the first and second ends of the primary winding, respectively, to the reference voltage.

9. The driver circuit of claim 8 wherein the drive output is coupled to the clock input of the flip-flop.

10. The driver circuit of claim 8 wherein the flip-flop is a latching flip-flop.

11. The driver circuit of claim 8 wherein the first and second switches are transistors.

12. The driver circuit of claim 8 wherein the transformer further comprises a center tap on the primary winding that is coupled to the drive output of the current steering module.

13. A system comprising:

a power source;

an arc lamp producing a light having a brightness; and

a driver circuit configured to provide electrical energy from the power source to the fluorescent lamp, the driver circuit comprising;

a transformer having a primary winding and a secondary winding, wherein each of the primary and secondary windings have a first and a second end and are configured to conduct an electrical current, wherein the primary winding comprises a center tap, and wherein the ends of the secondary winding are coupled to the arc lamp; and

a current steering module configured to provide a drive output from the power source to the center tap of the transformer in response to a current steering input.

14. The system of claim 13 wherein the device driver further comprises a power control module configured to generate a boost command in response to a difference between the brightness of the lamp and a luminance command.

15. The system of claim 14 wherein the lamp drive current provided to the arc lamp is increased in response to the boost command.

16. The system of claim 14 wherein the power source is configured to receive the boost command and to adjust the electrical energy provided to the driver circuit in response thereto.

17. The system of claim 14 wherein the boost command is provided to the transformer to adjust a ratio of turns in the primary and secondary windings.

18. The system of claim 14 wherein the boost command is provided to a boost coil adjacent the primary winding of the transformer.

19. A lamp driver device for driving an arc lamp in an optical display, the lamp driver device comprising:

a logarithmic amplifier, the logarithmic amplifier having a relatively high gain at low luminance levels and a relatively low gain at high luminance levels, the logarithmic amplifier including an op amp coupled to a photo-diode, the op amp configured with negative feedback to drive a current such that substantially zero volts are across a photo-diode to compensate for temperature differences in the photo-diode; and

a power recovery and control circuit, the power recover and control circuit coupled to a lamp interface and feeding back excess energy from the lamp interface to a power source, the logarithmic amplifier and power recovery and control circuit providing a precise control of plasma in the arc lamp.

20. The device of claim 19 further comprising a power control module configured to generate a boost command in response to a difference between a brightness of a light provided by the arc lamp and a luminance command provided to the power recovery and control circuit.