Solid state lighting panels with variable voltage boost current sources

• US 8,941,331 B2
• Filed: 05/17/2013
• Issued: 01/27/2015
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Brightplus Ventures LLC (IPValuation Partners, LLC)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Roberts, John K., Vadas, Keith J., Murugesu, Muhinthan
• Primary Examiner(s): A, Minh D
• Application Number:
  US13/896,977
• Publication Number:
  US 20130249408A1
• Time in Patent Office: 620 Days
• Field of Search: 315/291, 315/307, 315/224, 315/246, 315/185.R, 315/200.R, 315/312, 315/308
• US Class Current: 315/308
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• 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 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

A lighting system includes a lighting panel having a string of solid state lighting devices and a current supply circuit having a voltage input terminal, a control input terminal, and first and second output terminals coupled to the string of solid state lighting devices. The current supply circuit is configured to supply an on-state drive current to the string of solid state lighting devices in response to a control signal. The current supply circuit includes a charging inductor coupled to the voltage input terminal and an output capacitor coupled to the first output terminal. The current supply circuit is configured to operate in continuous conduction mode in which current continuously flows through the charging inductor while the on-state drive current is supplied to the string of solid state light emitting devices.

Claims

1. A lighting system, comprising:

at least two strings of solid state lighting devices that are respectively configured to emit at least a first light and a second light, respectively;

at least two current supply circuits coupled to first and second strings of the at least two strings, respectively, each of the current supply circuits configured to supply an on-state drive current to a respective string of the at least two strings of solid state lighting devices in response to at least one control signal generated in response to a sensor output signal generated by at least one temperature sensor, each of the current supply circuits comprising;

a controller having a control input, a first control output configured to provide a first PWM control signal, and a second control output configured to provide a second PWM control signal; and

first and second output terminals coupled to the respective string of the at least two strings of solid state lighting devices.

2. The lighting system according to claim 1, further comprising a sense resistor coupled to the second output terminal of ones of the current supply circuits.

3. The lighting system according to claim 2,

wherein the controller further comprises a feedback input coupled to the sense resistor, and

wherein the controller is configured to activate the second control signal in response to a feedback signal received on the feedback input.

4. The lighting system according to claim 1, wherein the controller comprises a closed loop control system that is configured to generate the first and second PWM control signals in response to the sensor output signals generated by the at least one temperature sensor.

5. The lighting system according to claim 1, wherein ones of the at least two current supply circuits comprise a variable voltage boost, constant current power supply circuit configured to operate in continuous current mode.

6. The lighting system according to claim 1, wherein ones of the at least two current supply circuits comprise a voltage input terminal, and a control input terminal.

7. The lighting system according to claim 1, wherein ones of the at least two current supply circuits comprise a charging inductor coupled to the voltage input terminal and an output capacitor coupled to the first output terminal.

8. The lighting system according to claim 7, wherein the ones of the at least two current supply circuits are each configured to operate in continuous conduction mode in which current continuously flows through the charging inductor while the on-state drive current is supplied to the first and second strings, respectively.

9. The lighting system according to claim 7, wherein each of the current supply circuits comprises:

a rectifier having an anode coupled to the charging inductor and a cathode coupled to the output capacitor; and

a first control transistor coupled to the anode of the rectifier and having a control terminal coupled to the first control output of the controller,

wherein the first control transistor is configured to cause the charging inductor to be energized in response to the first PWM control signal from the controller and to cause energy stored in the charging inductor to be discharged through the rectifier and into the output capacitor in response to the first PWM control signal.

10. The lighting system according to claim 9, further comprising a second control transistor coupled to the second output terminal of the current supply circuit and having an input coupled to the second control output of the controller;

wherein the second control transistor is configured to cause a voltage stored in the output capacitor to be applied to the first output terminal of the current supply circuit in response to the second PWM control signal from the controller.

11. The lighting system according to claim 10, wherein ones of the current supply circuits further comprise:

a low pass filter between the second control output and the second control transistor.

12. The lighting system according to claim 7, wherein the charging inductor has an inductance of about 50 μ

H to about 1.3 mH.

13. The lighting system according to claim 7, wherein the charging inductor has an inductance of about 680 pH.

14. The lighting system according to claim 1, wherein the sensor output signal comprises a first sensor output signal, further comprising a light sensor that generates a second sensor output signal responsive to light output by the lighting system,

wherein the at least one control signal comprises the first sensor output signal and the second output sensor signal.

15. The lighting system according to claim 1, wherein ones of the current supply circuits are configured to convert at least about 85% of input power into output power.

16. The lighting system according to claim 1, wherein ones of the current supply circuits are configured to convert at least about 90% of input power into output power.

17. A lighting system, comprising:

a lighting panel including at least first and second strings of solid state lighting devices that are respectively configured to emit at least a first light and a second light, respectively;

at least first and second current supply circuits coupled to the at least first and second strings of solid state lighting devices, respectively, and configured to supply an on-state drive current to a respective one of the first and second strings of solid state lighting devices; and

a pulse width modulation (PWM) controller that is coupled to the first current supply circuit and the second current supply circuit and that is configured to generate, for each of the first current supply circuit and the second current supply circuit, a first PWM control signal and a second PWM control signal that are supplied to the each of the at least first and second strings.

18. The lighting system according to claim 17,

wherein each of the first and second current supply circuits comprises a variable voltage boost, constant current power supply circuit configured to operate in continuous current mode.

19. The lighting system according to claim 18, wherein each of the first and second current supply circuits comprises:

a temperature sensor that is configured to generate a sensor output signal that the PWM controller uses to generate the first PWM signal or the second PWM signal, and

a sense resistor that is coupled to an output terminal of the current supply circuit and that is configured to provide a feedback signal to the PWM controller.

20. The lighting system according to claim 17, wherein each of the first and second current supply circuits comprises a sense resistor that is coupled to an output terminal of the respective one of the first and second current supply circuits and that is coupled to a feedback input to provide the feedback signal to provide closed loop control.

21. The lighting system according to claim 20, further comprising a filter coupled to the sense resistor, the filter configured to filter the feedback input.

22. The lighting system according to claim 17,

wherein the first string of solid state lighting devices are coated with a wavelength conversion phosphor and are configured to emit the first light that includes a combined light including a dominant wavelength corresponding to a blue color and a dominant wavelength corresponding to a yellow color, and

wherein the second string of solid state lighting devices are configured to emit the second light that includes a dominant wavelength corresponding to a red color.

23. The lighting system according to claim 22, wherein the first current supply circuit provides current control of the first string of solid state lighting devices that is independent of current control of the second string of solid state lighting devices provided by the second current supply circuit.

24. The lighting system according to claim 22, further comprising a third string of solid state lighting devices that are configured to emit a third light that includes a dominant wavelength corresponding to a red color.

25. The lighting system according to claim 24, further comprising a third current supply circuit that is configured to supply an on-state drive current to the third string of solid state lighting devices, and

wherein the first current supply circuit provides current control of the first string of solid state lighting devices that is independent of current control of the second string of solid state lighting devices provided by the second current supply circuit and that is independent of current control of the third string of solid state lighting devices provided by the third current supply circuit.