Light driving system and method

• US 8,928,243 B2
• Filed: 12/27/2011
• Issued: 01/06/2015
• Est. Priority Date: 12/27/2011
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Potter, Geoffrey, Sinow, Victor Samuel
• Primary Examiner(s): Le, Tung X
• Assistant Examiner(s): COOPER, JONATHAN G
• Application Number:
  US13/337,689
• Publication Number:
  US 20130162169A1
• Time in Patent Office: 1,106 Days
• Field of Search: 315/291, 315/294, 315/297, 315/312
• US Class Current: 315/291
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light driving system is provided that includes a light dimmer that receives an AC input signal and provides a dimmer output signal that includes a fast rising leading edge, a rectifier that receives the dimmer output signal and provide a rectified dimmer output signal and an AC/DC converter that filters the rectified dimmer output signal to provide a DC input signal that is employed to drive a light. The light driving system also comprises a protection circuit that limits current to the AC/DC converter during the fast rising leading edge of the dimmer output signal.

Claims

1. A light driving system comprising:

a light dimmer that receives an AC input signal and provides a dimmer output signal that includes a fast rising leading edge;

a rectifier that receives the dimmer output signal and provide a rectified dimmer output signal;

an AC/ DC converter that filters the rectified dimmer output signal to provide a DC input signal that is employed to drive a light; and

a protection circuit that limits current to the AC/ DC converter during the fast rising leading edge of the dimmer output signal, wherein a controller opens the switch at a falling edge zero crossing point of the dimmer output signal, monitors for the fast rising leading edge of the dimmer output signal and closes the switch bypassing the protection element after a predetermined amount of time after the fast rising leading edge of the dimmer output signal is detected to allow sufficient energy dissipation to mitigate ringing caused by the fast rising leading edge.

2. The system of claim 1, wherein the protection circuit also limits inrush current at startup of the light driving system.

3. The system of claim 1, wherein the protection circuit is a protection element coupled in parallel with a switch, wherein the protection element is coupled into the light driving system during the fast rising leading edge of the dimmer output signal by opening the switch and bypassed after the fast rising leading edge of the dimmer output signal by closing of the switch.

4. The system of claim 1, wherein the controller is part of the AC/ DC regulator and drives a driver circuit to provide a DC voltage to turn on the light and the filter is an input capacitor of the controller.

5. The system of claim 1, wherein the switch is a metal oxide field effect transistor (MOSFET) and the controller slowly turns on the MOSFET upon detection of a fast rising leading edge of the dimmer output signal.

6. The system of claim 1, wherein the protection element and switch are coupled between the rectifier and the controller.

7. The system of claim 1, wherein the protection element and switch are coupled in series with an input capacitor of the controller.

8. A light driving system comprising:

a light dimmer that receives an AC input signal and provides a dimmer output signal that includes a fast rising leading edge;

a rectifier that receives the dimmer output signal and provide a rectified dimmer output signal;

an electromagnetic interference (EMI) filter coupled between the light dimmer and the rectifier to mitigate EMI;

a switching converter that filters the rectified dimmer output signal to provide a DC input signal to a controller that controls a light driver to drive a light; and

a protection circuit that limits current to the switching converter during the fast rising leading edge of the dimmer output signal, wherein the controller opens the switch at a falling edge zero crossing point of the dimmer output signal, monitors for the fast rising leading edge of the dimmer output signal and closes the switch bypassing the resistor after a predetermined amount of time after the fast rising leading edge of the dimmer output signal has been detected to allow sufficient energy dissipation to mitigate ringing caused by the fast rising leading edge.

9. The system of claim 8, wherein the protection circuit is a protection resistor coupled in parallel with a switch, wherein the protection resistor is coupled into the light driving system during the fast rising leading edge of the dimmer output signal by opening the switch and bypassed after the fast rising leading of the dimmer output signal by closing of the switch.

10. The system of claim 8, wherein the protection resistor and switch are coupled between the rectifier and the controller.

11. The system of claim 10, wherein the protection resistor and switch are coupled in series with an input capacitor of the controller.

12. The system of claim 11, wherein the controller couples the protection resistor into the light driving system at startup to limit inrush current.

13. The system of claim 8, wherein the switch is a metal oxide field effect transistor (MOSFET) and the controller slowly turns on the MOSFET upon detection of a fast rising leading edge of the dimmer output signal.

14. A method for suppressing ringing in a light driving system having an AC/ DC converter that drives a light, the method comprising:

switching in a protection element into the light driving system to provide damping to protect the AC/ DC converter during a fast rising leading edge of an input signal;

switching out the protection element after the fast rising leading edge of the input signal;

switching in the protection element into the light driving system during startup to protect the AC/ DC converter from inrush current; and

switching out the protection element after the voltage to the AC/ DC converter has reached a predetermined voltage,

wherein the switching in the protection element into the light driving system comprises switching in a protection resistor at a falling edge zero crossing point of a dimmer output signal and the switching out the protection element after the fast rising leading edge comprises switching out the protection resistor after a predetermined amount of time to allow sufficient energy dissipation to mitigate ringing caused by the fast rising leading edge.