Power control system for LCD monitor

• US 8,373,641 B2
• Filed: 02/27/2008
• Issued: 02/12/2013
• Est. Priority Date: 02/21/2003
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Lee, Sang Ho
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): HOLTON, STEVEN E
• Application Number:
  US12/038,429
• Publication Number:
  US 20080143705A1
• Time in Patent Office: 1,812 Days
• Field of Search: 345/102, 345211-213, 315/291
• US Class Current: 345/102
• CPC Class Codes: H05B 41/2855 against abnormal lamp operating conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A power control system for an LCD monitor having an LCD panel includes a light source unit providing light to the LCD panel, a power supply unit generating a standard low DC current, and a high-voltage generator for converting the lower DC voltage to a relatively high voltage and supplying the high voltage to the light source. The power control system further includes a feedback control unit coupled to the power supply unit for interrupting the operation of the power supply unit when the converted high voltage is determined to be abnormal. The feedback control unit includes a cable, through which a voltage can be induced due to high voltage generated by the high-voltage generator, and a power supply control circuit capable of interrupting the operation of the power supply unit when the converted high voltage is determined to be abnormal by analyzing the induced current.

Claims

1. A power control system for a liquid crystal display (LCD) monitor having an LCD panel, the power control system comprising:

a light source unit for providing light to the LCD panel;

a power supply unit for generating a low direct current (DC) voltage;

a high-voltage generator for outputting to the light source unit a high voltage based on the low DC voltage;

a feedback control unit for detecting a voltage induced from the high voltage output from the high-voltage generator, for determining based on a level of the induced voltage an abnormal condition of the high voltage output, and for inhibiting the output of the high-voltage generator during a time corresponding to the abnormal condition by suspending operation of said power supply unit during the time corresponding to the abnormal condition, the induced voltage representing the abnormal condition in at least one case of when a power surge exists in the high voltage output, when there is no detection of induced voltage from the high voltage output, and when the induced voltage indicates that the high voltage output is less than a predetermined voltage level; and

a main controller for generating a power control signal for controlling an on/off function of the power supply unit,

wherein said feedback control unit comprises a patterned conductor for conducting the induced voltage to said feedback control unit.

2. The power control system of claim 1, wherein the patterned conductor is a printed current board (PCB) pattern disposed electromagnetically proximate to an electrical output of the high-voltage generator and to an electrical input of the light source unit.

3. The power control system of claim 1, wherein the patterned conductor is electrically isolated from the high voltage output and has two ends, one end being connected to an input of the feedback control unit and the other end being grounded.

4. The power control system of claim 1, wherein said feedback control unit further comprises a power supply control circuit for receiving the induced voltage and for suspending further operation of the power supply unit during the time corresponding to the abnormal condition.

5. The power control system of claim 4, wherein the patterned conductor is configured to transmit the conducted voltage to said power supply control circuit.

6. The power control system of claim 4, wherein said power supply control circuit is integrated within the power supply unit.

7. The power control system of claim 6, wherein said power supply control circuit includes a switching mode power supply (SMPS) control circuit.

8. The power control system of claim 6, wherein said feedback control unit further comprises a Zener diode for limiting the induced voltage received by said power supply control circuit.

9. The power control system of claim 1, wherein said feedback control unit further comprises:

a coupling capacitor for alternating current (AC) coupling the induced voltage conducted by the patterned conductor;

an integration circuit for integrating the AC-coupled voltage, to output an integrated DC voltage; and

a rectifying diode for outputting the integrated DC voltage, the integrated DC voltage being used to determine the abnormal condition.

10. The power control system of claim 9, wherein said integration circuit comprises a series resistor and a shunt capacitor.

11. The power control system of claim 1, wherein said light source unit includes a fluorescent lamp.

12. The power control system of claim 11, wherein the fluorescent lamp includes a cold cathode fluorescent lamp (CCFL).

13. The power control system of claim 1 wherein the main controller further generates a brightness control signal for controlling brightness of the light source unit.

14. The power control system of claim 13, further comprising:

a direct current to direct current (DC/DC) converter for converting a standard DC voltage to a predetermined DC voltage; and

a brightness controller for controlling the predetermined DC voltage output from the DC/DC converter according to the brightness control signal received from the main controller.

15. A method for controlling power to a liquid crystal display (LCD) monitor having an LCD panel, the method comprising:

generating a low direct current (DC) voltage;

generating a high voltage based on the low DC voltage;

applying the generated high voltage to a light source unit for providing light to the LCD panel;

detecting a voltage induced from the high voltage provided to the light source unit;

determining, based on a level of the induced voltage, an abnormal condition of the generated high voltage, the induced voltage representing the abnormal condition in at least one case of when a power surge exists in the generated high voltage, when there is no detection of induced voltage from the generated high voltage, and when the induced voltage indicates that the high voltage is less than a predetermined voltage level; and

inhibiting generating said high voltage during a time corresponding to the abnormal condition by suspending generating said low DC voltage,

wherein the detected voltage is induced into a patterned conductor for conducting the induced voltage to a feedback control unit.

16. The method of claim 15, wherein the feedback control unit suspends generating said low DC voltage based on said determined abnormal condition.

17. The method of claim 16, wherein the patterned conductor is a printed current board (PCB) pattern disposed electromagnetically proximate to an electrical output of a high-voltage generator that generates the high voltage and to an electrical input of the light source unit.

18. The method of claim 17, wherein the patterned conductor is electrically isolated from the generated high voltage and has two ends, one end being connected to an input of the feedback control unit and the other end being grounded.

19. The method of claim 15, further comprising:

generating a power control signal for controlling an on/off function of said low DC voltage generation and for generating a brightness control signal for controlling brightness of a light source unit for providing light to the LCD panel;

converting a standard DC voltage to a predetermined DC voltage; and

controlling the predetermined DC voltage according to the brightness control signal.