Method and apparatus for optimizing power efficiency in light emitting device arrays

• US 20050116662A1
• Filed: 11/08/2004
• Published: 06/02/2005
• Est. Priority Date: 11/06/2003
• Status: Active Grant

• Current Assignee: OL Security LLC (Intellectual Ventures LLC)
• Original Assignee: CEYX Technologies Incorporated
• Inventors: Sanchez, Jorge
• Granted Patent: US 7,151,346 B2
• Time in Patent Office: Days
• US Class Current: 315/225
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H05B 41/245 for a plurality of lamps
• CPC Class Codes: H05B 41/282 with semiconductor devices H05B41/2806, H05B41/288, H05B41/295 take precedence
• 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: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The disclosed embodiments provide a method and apparatus for optimizing power efficiency in liquid crystal displays. A microprocessor or embedded microcontroller associated with circuit control modules eliminates redundancy by allowing a single inverter to equalize the intensity of illumination for an array of multiple CCFLs. The microcontroller optimizes power management by continuously sensing the operating currents of every lamp and automatically adjusts for variations in illumination of individual lamps by parallel switching of capacitance that ensures an equal current is applied to each lamp. The microcontroller produces the appropriate control signals and executes a digital servo control algorithm to modify the currents for carrying out the luminance adjustments.

Claims

1. A method of power control for multiple luminent devices comprising:

sensing individual output information for each luminent device of a multiple device array;

processing the output information to produce individual power conserving current control signals for each luminent device; and

conserving power consumption by adjusting an operating current applied to each luminent device through a single inverter in accord with the power conserving current control signals generated by a microcontroller.

2. The method of claim 1 wherein the luminent devices are cold cathode fluorescent lamps.

3. The method of claim 1 wherein the inverter is replaced with a driver and the luminent devices are light emitting diodes.

4. An apparatus for power control of multiple luminent devices comprising:

sensors for sensing individual output information for each luminent device of a multiple device array;

a microcontroller for processing the output information to produce individual power conserving current control signals for each luminent device; and

a current control circuit and server control system software for conserving power consumption by adjusting an individual operating current applied to each luminent device through a single inverter in accord with the individual power conserving current control signals.

5. The apparatus of claim 4 wherein the sensors are current sensors.

6. The apparatus of claim 4 wherein the sensors are light sensors.

7. The apparatus of claim 4 wherein the luminent devices are cold cathode fluorescent lamps.

8. The apparatus of claim 4 wherein the inverter is replaced with a driver and the luminent devices are light emitting diodes.

9. A method for power control in multiple luminent devices comprising:

receiving a power conserving current control signal from a microcontroller;

isolating a power conserving voltage control signal from the current power conserving control signal;

filtering the power conserving voltage control signal to produce an isolated power conserving voltage control signal compatible with a transistor;

setting impedance at the base of a transistor;

operating the transistor in accord with a current response required by the luminent device;

conserving power consumption by applying the power conserving voltage control signal to the transistor to generate a power efficient alternating current specified by the power conserving current control signal; and

,

routing both polarities of the power efficient alternating current to the luminent device.

10. The method of claim 9 wherein the transistor operates in linear mode.

11. The method of claim 9 wherein the transistor operates in switched mode.

12. The method of claim 9 wherein the luminent devices are cold cathode fluorescent lamps.

13. A circuit for power control in a luminent device comprising:

an isolator for receiving a power conserving current control signal from a microcontroller and isolating a power conserving voltage control signal from the power conserving current control signal;

a capacitor for filtering the power conserving voltage control signal to produce an isolated power conserving voltage control signal compatible with a transistor;

a resistor for setting impedance at the base of the transistor;

a transistor for generating a power efficient alternating current, specified by the power conserving current control signal, from the power conserving voltage control signal; and

,

a diode bridge for routing both polarities of the power efficient alternating current to the luminent device.

14. The circuit of claim 13 wherein the isolator is an optical isolator.

15. The circuit of claim 13 wherein the isolator is a photovoltaic converter that converts the current control signal to a proportional light output that is then converted to a voltage.

16. A method for power control of a luminent device comprising:

sensing individual output information for an individual luminent device in a multiple device array;

processing the output information to produce an individual power conserving current control signal for the luminent device;

applying the power conserving current control signal to a plurality of switches coupled to parallel capacitors to create a power efficient operating current specified by the power conserving current control signal; and

,

conserving power consumption by driving the luminent device with the power efficient operating current.

17. The method of claim 16 wherein the luminent device is a cold cathode fluorescent lamp.

18. The method of claim 16 wherein the luminent device is a light emitting diode.

19. A circuit for power control in a luminent device comprising:

sensors for sensing individual output information for an individual luminent device in a multiple device array;

a microcontroller for processing the output information to produce an individual power conserving current control signal for the luminent device;

switches coupled to parallel capacitors for creating a power efficient operating current specified by the power conserving current control signal; and

,

a luminent device to be driven by the power efficient operating current.

20. The circuit of claim 19 wherein the luminent device is a cold cathode fluorescent lamp.

21. The circuit of claim 19 wherein the luminent device is a light emitting diode.

22. A method of power control for multiple lumient devices comprising:

generating a high frequency pulse width modulated power control signal with a high frequency clock;

generating a low frequency pulse width modulated power control signal with a low frequency clock;

sensing output feedback information for individual luminent devices in a multiple device array;

using the feedback information to determine optimal pulse width timing modification values for the high and low frequency pulse width modulated power control signals by applying a digital power conservation algorithm executed by a microcontroller;

modifying the pulse widths of the high and low frequency power control signals according to the determined modification values to produce optimized high and low frequency pulse width modulated power control signals; and

,

routing the optimized high and low frequency pulse width modulated power control signals to an inverter switching circuit for driving a luminent device.

23. The method of claim 22 wherein the digital power conservation algorithm is continuously executed.

24. An apparatus for power control of multiple lumient devices comprising:

a high frequency clock for generating a high frequency pulse width modulated power control signal;

a low frequency clock for generating a low frequency pulse width modulated power control signal;

sensors for sensing output feedback information for individual luminent devices in a multiple device array;

a microcontroller for executing a digital power conservation algorithm using the feedback information to determine optimal pulse width timing modification values for the high and low frequency pulse width modulated power control signals;

pulse width modulator generators for modifying the pulse widths of the high and low frequency power control signals according to the determined modification values to produce optimized high and low frequency pulse width modulated power control signals; and

,

logic gates for routing the optimized high and low frequency pulse width modulated power control signals to an inverter switching circuit for driving a luminent device.