Series connected power supply for semiconductor-based vehicle lighting systems

• US 7,710,050 B2
• Filed: 11/17/2005
• Issued: 05/04/2010
• Est. Priority Date: 11/17/2005
• Status: Active Grant

• Current Assignee: Magna International Incorporated
• Original Assignee: Magna International Incorporated
• Inventors: MacDonald, Jamie A., Preston, Nigel Ashley
• Primary Examiner(s): Philogene; Haissa
• Application Number:
  US11/281,332
• Publication Number:
  US 20070108843A1
• Time in Patent Office: 1,629 Days
• Field of Search: 315/185.R, 315/185.S, 315/169.1, 315/169.3, 315/200.A, 315/312, 315/291, 315/307, 315/77, 315/247, 315/320, 315/149, 315/158, 345/44, 345/46, 345/204, 345211-214, 345/207, 340/815.4, 340/815.45, 372/29.012, 372/38.02, 372/38.04, 362/800
• US Class Current: 315/312
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 45/54 in a series array of LEDs

Abstract

A novel and advantageous power supply is disclosed for lighting systems employing semiconductor light sources where the semiconductor light sources are connected in series. The power supply includes a constant current source to supply current to the semiconductor light sources and a bypass switch is provided around each semiconductor light source, or each sub-string of series connected semiconductor light sources. By opening or closing respective bypass switches, individual semiconductor light sources or sub-strings of semiconductor light sources can be illuminated or extinguished as desired. If the bypass switches are electrically controllable, such as semiconductor switches or relays, failures of one or more semiconductor light sources can be determined by the power supply and failed light sources can be bypassed and/or redundant semiconductor elements illuminated to replace failed light sources. Further, if the bypass switches are semiconductor switches, the power supply can employ pulse width modulation techniques to dim one or more semiconductor light sources as desired.

Claims

1. A power supply for series-connected light emitting diodes in a motor vehicle lighting system, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected light emitting diodes;

a semiconductor switch across each respective one of the light emitting diodes, each semiconductor switch operating when closed to provide a current path around a respective light emitting diode; and

a controller to operate said semiconductor switch, said controller operable to open and close each respective semiconductor switch and further operable to pulse width modulate the operation of at least one semiconductor switch to dim the corresponding light emitting diode.

2. A power supply according to claim 1 wherein the constant current source is a buck boost converter.

3. A power supply according to claim 1 wherein the constant current source is a Single Element Primary Inductor Circuit (SEPIC).

4. A power supply according to claim 1 wherein the controller is further operable to detect failures of light emitting diodes.

5. A power supply according to claim 4 wherein the controller detects closed circuit failures of light emitting diodes by measuring the change in voltage across the constant current source while opening and closing respective semiconductor switches.

6. A power supply according to claim 4 wherein the controller detects open circuit failures of light emitting diodes by measuring the current provided by the power supply.

7. A power supply according to claim 4 wherein the controller detects open circuit failures of light emitting diodes by measuring the voltage provided by the power supply.

8. A power supply according to claim 4 wherein at least one series connected light emitting diode is redundant and its respective semiconductor switch is opened by the controller upon determination by the controller of a failure of another light emitting diode.

9. A power supply according to claim 4 wherein the controller further generates an output signal indicating the detection of a failure of a light emitting diode.

10. A power supply according to claim 9 wherein the output signal indicates which light emitting diode has failed.

11. A power supply according to claim 1 further comprising two or more series connected light emitting diodes arranged as a sub-string of light emitting diodes, the sub-string having a corresponding semiconductor switch across it.

12. A power supply for series-connected light emitting diodes in a motor vehicle lighting system, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected light emitting diodes;

a bypass switch across each respective one of the light emitting diodes, each bypass switch operating when closed to provide a current path around a respective light emitting diode;

a controller to operate said bypass switches, and

at least one temperature sensor providing a signal to said controller to indicate a measured temperature, said controller being responsive to the measured signal to alter the current supplied to at least one light emitting diode.

13. A power supply according to claim 12 wherein the controller is operable to alter the current by pulse width modulating the operation of at least one bypass switch.

14. A power supply according to claim 12 comprising at least two temperature sensors, each respective temperature sensor providing a respective signal to the controller to indicate a respective measured temperature, the controller being responsive to each respective measure signal to alter the current supplied to each respective light emitting diode.

15. A power supply for series-connected semiconductor light sources, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected semiconductor light sources;

a bypass switch across each respective one of the semiconductor light sources, each bypass switch operating when closed to provide a current path around a respective semiconductor light source; and

a controller to operate said bypass switches, said controller operable to detect failures of the semiconductor light sources, wherein said controller detects closed circuit failures of the semiconductor light sources by measuring the change in voltage across the constant current source while opening and closing respective bypass switches.

16. A power supply for series-connected semiconductor light sources, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected semiconductor light sources;

a bypass switch across each respective one of the semiconductor light sources, each bypass switch operating when closed to provide a current path around a respective semiconductor light source; and

a controller to operate said bypass switches, said controller operable to detect failures of the semiconductor light sources, wherein said controller detects open circuit failures of the semiconductor light sources by measuring the current provided by the power supply.

17. A power supply for series-connected semiconductor light sources, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected semiconductor light sources;

a bypass switch across each respective one of the semiconductor light sources, each bypass switch operating when closed to provide a current path around a respective semiconductor light source; and

a controller to operate said bypass switches, said controller operable to detect failures of the semiconductor light sources, wherein said controller detects open circuit failures of the semiconductor light sources by measuring the voltage provided by the power supply.

18. A power supply for series-connected semiconductor light sources, comprising:

a constant current source to supply a pre-selected level of electrical current to the series connected semiconductor light sources;

a bypass switch across each respective one of the semiconductor light sources, each bypass switch operating when closed to provide a current path around a respective semiconductor light source; and

a controller to operate said bypass switches, said controller operable to detect failures of the semiconductor light sources;

wherein at least one series connected semiconductor light source is redundant and its respective bypass switch is opened by the controller upon determination by the controller of a failure of another semiconductor light source.