Solid State Lighting Panels with Variable Voltage Boost Current Sources

• US 20120235575A1
• Filed: 05/11/2012
• Published: 09/20/2012
• 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
• Granted Patent: US 8,461,776 B2
• Time in Patent Office: Days
• US Class Current: 315/151
• 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 three strings of solid state lighting devices that are respectively configured to emit at least a first light, a second light and a third light, respectively; and

a digital control system that is configured to generate a first pulse width modulation (PWM) control signal and a second PWM control signal and that includes a closed loop control system that is configured to generate the first and second PWM control signals in response to sensor output signals generated by at least one sensor, the first and second PWM control signals operative to cause an on-state drive current to be supplied to ones of the at least three strings of solid state lighting devices.

2. The lighting system according to claim 1, further comprising at least three current supply circuits coupled to the first, second and third strings, respectively, wherein each of the current supply circuits is configured to supply the on-state drive current to a respective string of the at least three solid state lighting devices in response to the first and second PWM control signals.

3. The lighting system according to claim 2, wherein ones of the at least three current supply circuits comprise a variable voltage boost, constant current power supply circuit configured to operate in continuous current mode.

4. The lighting system according to claim 2, wherein ones of the at least three current supply circuits comprise a voltage input terminal, a control input terminal, and first and second output terminals coupled to the string of solid state lighting devices.

5. The lighting system according to claim 2, wherein the at least three current supply circuits are configured to supply the on-state drive current to the at least three first strings of solid state lighting devices, respectively.

6. The lighting system according to claim 2, wherein ones of the at least three current supply circuits comprise a charging inductor coupled to the voltage input terminal and an output capacitor coupled to the first output terminal.

7. The lighting system according to claim 6, wherein the 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, second and third strings, respectively.

8. The lighting system according to claim 6, 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;

a controller having a control input and first and second control outputs; 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 a first 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 control signal.

9. The lighting system according to claim 8, 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 a second control signal from the controller.

10. The lighting system according to claim 9, wherein the current supply circuit further comprises:

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

11. The lighting system according to claim 9, wherein the current supply circuit further comprises a sense resistor coupled to the second output terminal of the current supply circuit, and 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.

12. The lighting system according to claim 11, wherein the current supply circuit further comprises a low pass filter coupled between the sense resistor and the feedback input of the controller.

13. The lighting system according to claim 8, wherein the charging inductor has an inductance of about 50 μ

H to about 1.3 mH.

14. The lighting system according to claim 8, wherein the charging inductor has an inductance of about 680 μ

H.

15. The lighting system according to claim 1, wherein the at least one sensor comprises a temperature sensor that generates a sensor output signal corresponding to temperature information.

16. The lighting system according to claim 1, wherein the at least one sensor comprises a light sensor that generates sensor output signal responsive to light output by the lighting system.

17. The lighting system according to claim 1, wherein the current supply circuit is configured to convert at least about 85% of input power into output power.

18. The lighting system according to claim 1, wherein the current supply circuit is configured to convert at least about 90% of input power into output power.

19. A lighting system, comprising:

a lighting panel including at least three strings of solid state lighting devices that are each configured to emit light;

at least three current supply circuits coupled to the at least three strings, respectively, wherein each of the current supply circuits comprises a variable voltage boost, constant current power supply circuit configured to operate in continuous current mode; and

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

wherein each of the current supply circuits comprises;

a first control transistor including a control terminal coupled to a first control output of the PWM controller, and

a second control transistor coupled to an output terminal of the current supply circuit and having an input coupled to a second control output of the PWM controller.