Method and apparatus for an intelligent light emitting diode driver having power factor correction capability

• US 8,441,199 B2
• Filed: 12/29/2009
• Issued: 05/14/2013
• Est. Priority Date: 03/23/2009
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Santo, Hendrik, Schindler, Matthew D., Sangam, Dilip, Dhayagude, Tushar
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Chen, Jianzi
• Application Number:
  US12/649,057
• Publication Number:
  US 20100237786A1
• Time in Patent Office: 1,232 Days
• Field of Search: 315/185.R, 315/192, 315/200.R, 315/201, 315/205, 315/247, 315/250, 315/291, 315/294, 315/297, 315/299, 315/300, 315/302, 315/307, 315/308, 315/311, 315/312, 315/361
• US Class Current: 315/224
• 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
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/30 Driver circuits
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology

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 a set of light emitting diode strings, comprising:

a programmable controller having one or more associated detectors, the programmable controller obtains data related to one or more measurable parameters for the set of light emitting diode strings via the associated detectors, determines a drive value based at least in part on the measurable parameters, and generates a control signal based on the drive value;

a power supply system, having power factor correction capability, obtains the control signal as a first input, and an ac waveform voltage as a second input, and generates a drive voltage based at least in part on at least one of the control signal or the ac waveform voltage; and

a programmable variable resistor included in the power supply for setting a set of operating conditions for an input current and voltage control loop that facilitate the power supply in generating the drive voltage;

wherein the one or more associated detectors includes at least a first triode region detector coupled to at least a first light emitting diode in the set of light emitting diode strings, the first triode region detector determines a limit triode region for the first light emitting diode; and

wherein the programmable controller determines the drive value based at least in part on the limit triode region.

2. The circuit of claim 1, wherein the programmable variable resistor is controlled via a state machine.

3. The circuit of claim 2, wherein the state machine controls the programmable variable resistor based at least in part on at least one of the following inputs:

a zero crossing signal, an input line voltage value, a discrete error voltage, the limit triode region, or an input voltage feedforward correction value.

4. The circuit of claim 3, wherein the zero crossing signals are determined via a zero crossing detector included in the power supply.

5. The circuit of claim 1,

wherein the one or more associated detectors includes a second triode region detector coupled to at least a second light emitting diode in the set of light emitting diode strings, the second triode region detector determines a second upper limit triode region for the second light emitting diode;

wherein the limit triode region is a first upper limit triode region; and

wherein the programmable controller determines the drive value based at least in part on the higher value of the first upper limit triode region and the second upper limit triode region.

6. The circuit of claim 1, wherein the measurable parameters include at least one of an ambient temperature of at least one of the light emitting diodes in the light emitting diode strings, a luminous intensity of at least one of the light emitting diodes in the light emitting diode strings, or a wavelength of light emitted by at least one of the light emitting diodes in the light emitting diode strings.

7. The circuit of claim 1, wherein the programmable controller includes at least one of a digital-to-analog converter, a state machine, digital processing circuitry, or analog processing circuitry.

8. The circuit of claim 7, wherein the state machine included in the programmable controller is also the state machine included in the power supply.

9. The circuit of claim 1, wherein the circuit is implemented in at least one of a liquid crystal display, a light emitting diode lighting system, or light emitting diode related driving system.

10. A method for controlling a set of light emitting diode strings, comprising:

determining at least one characteristic for at least a first light emitting diode included in the light emitting diode strings;

generating a control signal for a drive voltage for at least one of the light emitting diode strings based at least in part on the characteristics;

performing a power factor correction related to ac current and ac voltage waveforms inputs for a power supply;

producing the drive voltage based at least in part on the control signal, and a value of a programmable variable resistor located in an input current and voltage control loop; and

wherein determining at least one of the characteristics includes determining, using a first triode region detector, a first limit triode region for the first light emitting diode.

11. The method of claim 10, further comprising controlling the programmable variable resistor via a state machine.

12. The method of claim 11, wherein the state machine controls the programmable variable resistor based at least in part on at least one of a zero crossing signal, an input line voltage value, a discrete error voltage, the limit triode region signal, or an input voltage feedforward correction value.

13. The method of claim 12, further comprising determining the zero crossing signals via a zero crossing detector included in a power supply.

14. The method of claim 12, wherein the characteristics include at least one of an ambient temperature of at least one of the light emitting diodes in the light emitting diode strings, a luminous intensity of at least one of the light emitting diodes in the light emitting diode strings, or a wavelength of light emitted by at least one of the light emitting diodes in the light emitting diode strings.

15. The method of claim 14, further comprising determining the characteristics via a detector included in a programmable controller.

16. The method of claim 15, wherein the programmable controller includes at least one of a digital-to-analog converter, a state machine, digital processing circuitry, or analog processing circuitry.

17. The method of claim 16, wherein the programmable controller and power supply share one or more components.

18. The method of claim 17, wherein the components include the state machine.

19. The method of claim 11,

further comprising determining a second limit triode region for a second light emitting diode in the light emitting diode strings via a second triode region detector included in a power supply;

wherein the first limit triode region is a first upper limit triode region; and

wherein generating the control signal is based at least in part on a higher drive voltage.

20. A system facilitating control of a set of light emitting diode strings, comprising:

a programmable controller associated with a set of detectors that measures data including at least a limit triode region obtained via a triode region detector of at least one of the light emitting diodes in the light emitting diode strings, the controller determines a drive value based at least in part on the data, and generates a control signal based on the drive value;

a power supply having power factor correction capability that obtains the control signal as a first input, and an ac waveform voltage as a second input, and generates a drive voltage based at least in part on the ac voltage; and

a programmable variable resistor included in the power supply that sets a set of input current and voltage control loop operating conditions that facilitate the power supply in generating the drive voltage, wherein a state machine controls the programmable variable resistor based at least in part on at least one of the following inputs;

a zero crossing signal generated via a zero crossing detector, an input line voltage value obtained via an input voltage controlled input current loop, a discrete error voltage obtained via an operational amplifier, the limit triode region, or an input voltage feedforward correction signal obtained via an input voltage feed forward correction loop.