Apparatus and methodology for enhancing efficiency of a power distribution system having power factor correction capability by using a self-calibrating controller

• US 8,314,572 B2
• Filed: 03/23/2009
• Issued: 11/20/2012
• Est. Priority Date: 06/24/2008
• Status: Active Grant

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Schindler, Matthew, Dhayagude, Tushar, Santo, Hendrik, Sangam, Dilip
• Primary Examiner(s): Le, Tung X
• Application Number:
  US12/409,088
• Publication Number:
  US 20090315467A1
• Time in Patent Office: 1,338 Days
• Field of Search: 315/185.R, 315224-226, 315/291, 315/294, 315/297, 315307-309, 315/312
• US Class Current: 315/307
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines

Abstract

The present invention relates to circuits and methods for controlling one or more LED strings. The circuit comprises a programmable controller coupled to one or more detectors, wherein the one or more detectors are configured to detect one or more measurable parameters of one or more LEDs or LED drivers. The controller is configured to receive information from the one or more detectors related to the one or more measurable parameters and use that information to determine the desired drive voltage for the LED strings. The controller is associated with a power supply having power factor correction (PFC) capability. The controller provides the power supply with a control signal indicative of the desired drive voltage for one or more LED strings. The power supply also receives ac voltage and current waveforms as inputs and performs power factor correction and rectified waveforms related to the ac waveforms. The power supply generates the desired drive voltage based on the control signal.

Claims

1. A circuit for controlling one or more light emitting diode (LED) strings comprising:

a detector coupled to one or more LED strings and a programmable controller, wherein the detector is capable of;

detecting a first measurable parameter of the one or more LED strings;

the programmable controller that;

receives information from the detector related to the first measurable parameter; and

based on the received information, adjusts one or more controllable parameters of the one or more LED strings until receiving an indication from the detector that the first measurable parameter meets a reference condition,

wherein adjusting one or more controllable parameters includes using the information to determine a desired drive voltage level value, and generating a control signal indicative of the desired drive voltage value; and

a power supply having a power factor correction capability that;

receives the control signal as a first input;

receives an AC voltage waveform as a second input; and

generates a drive voltage based on the control signal.

2. The circuit of claim 1, wherein the detector includes a detector for detecting an upper limit of a triode region voltage range.

3. The circuit of claim 1, wherein the detector includes a detector for detecting an ambient temperature of a LED string.

4. The circuit of claim 1, wherein the detector includes a detector for detecting a luminous intensity of a LED.

5. The circuit of claim 1, wherein the detector includes a detector for detecting a wavelength of a light emitted by a LED.

6. The circuit of claim 1, wherein the programmable controller generates the control signal relative to a start up of at least one of the one or more LED strings.

7. The circuit of claim 1, wherein the programmable controller generates the control signal relative to a change in a second measurable parameter in at least one of the one or more LED strings.

8. The circuit of claim 1, wherein the programmable controller generates the control signal based at least in part on at least one of a fixed time interval or a variable time interval.

9. The circuit of claim 1, wherein the programmable controller comprises a digital-to-analog converter (DAC) and a state machine.

10. The circuit of claim 1, further comprising:

a liquid crystal display, wherein the circuit is implemented in the liquid crystal display.

11. A method for controlling one or more LED strings comprising:

detecting a first measurable parameter of one or more LED strings;

receiving information related to the first measurable parameter; and

based on receiving the information, adjusting one or more controllable parameters of the one or more LED strings until receiving an indication that the first measurable parameter meets a reference condition, wherein adjusting one or more controllable parameters includes;

generating a control signal indicative of a desired drive voltage for the one or more LED strings based on the information,

performing a power factor correction related to AC current and AC voltage waveforms inputs for a power supply, and

causing the power supply to generate the desired drive voltage based on the control signal.

12. The method of claim 11, wherein the control signal includes a current signal.

13. The method of claim 11, wherein performing the power factor correction includes causing the current waveform to be in phase with the voltage waveform.

14. The method of claim 11, wherein the first measurable parameter is selected from a group comprising ambient temperature of a LED, current flowing through a LED, voltage across a LED, luminous intensity of a LED, and a wavelength of light emitted by a LED.

15. The method of claim 11, wherein the generating of the control signal is initiated relative to a start up of at least one of the one or more LED strings.

16. The method of claim 11, wherein the generating of the control signal is initiated relative to a change in a second measurable parameter.

17. A liquid crystal display including a system for controlling one or more LED strings for backlighting comprising:

a detector coupled to one or more LED strings and configured for detecting an upper limit level for a triode region voltage range for a LED string;

a programmable decentralized controller associated with the detector that

receives information from the detector associated with the upper limit level for the triode region voltage range; and

based on the received information, generates a control signal indicative of a desired drive voltage level until receiving an indication from the detector that the upper limit level for the triode region voltage range meets a reference condition; and

a power supply having power factor correction capability associated with the programmable decentralized controller, wherein the power supply;

receives the control signal as a first input and an AC voltage waveform as a second input; and

generates a drive voltage waveform having the desired drive voltage level.

18. The liquid crystal display of claim 17, wherein the detector includes a detector for detecting an ambient temperature of a LED string.

19. The liquid crystal display of claim 17, wherein the control signal includes a current signal.

20. The liquid crystal display of claim 17, wherein the control signal includes a voltage signal.