Controlled Power Dissipation In A Lighting System

• US 20120112665A1
• Filed: 11/04/2011
• Published: 05/10/2012
• Est. Priority Date: 11/04/2010
• Status: Active Grant

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Inventors: Melanson, John L., King, Eric J.
• Granted Patent: US 9,497,850 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• 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 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05K 1/0203 Cooling of mounted components H05K1/0272 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

In at least one embodiment, a lighting system includes one, some, or all of a switch path, link path, and flyback path power dissipation circuits to actively and selectively control power dissipation of excess energy in a switching power converter of the lighting system. The flyback path power dissipation circuit dissipates power through a flyback path of the switching power converter. In at least one embodiment, the lighting system controls power dissipation through the flyback path by controlling a transformer primary current in the flyback path and, for example, limiting the primary current with a current source and dissipating power in the flyback switch and the current source.

Claims

1. An apparatus comprising:

a controller configured to control a flyback switch coupled to a primary-side transformer coil in an output stage of a switching power converter in a phase cut compatible, dimmable lighting system, wherein the controller is further configured to control a power dissipation circuit to dissipate excess energy through the flyback switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter.

2. The apparatus of claim 1 further comprising:

a current source coupled to the flyback switch to control current through the flyback switch during the charging phase of the switching power converter.

3. The apparatus of claim 2 wherein the current source is a constant current source.

4. The apparatus of claim 1 wherein the controller is further configured to control a duration of the charging phase to control an amount of energy dissipated through the flyback switch.

5. The apparatus of claim 1 wherein the power dissipation phase begins at an end of the charging phase and ends before a beginning of a next flyback phase.

6. The apparatus of claim 1 wherein the power dissipation phase begins prior to an end of the boost phase of the switching power converter and ends after a beginning of a next flyback phase of the switching power converter.

7. The apparatus of claim 1 wherein the charging phase occurs during the flyback phase of the switching power converter.

8. The apparatus of claim 1 wherein the controller is configured to control a member of a group consisting of:

current in the flyback switch, a conduction time of the flyback switch, or the current and the conduction time of the flyback switch.

9. The apparatus of claim 1 further comprising:

an active circuit to dissipate power at the output of a switching power converter when the switching power converter receives more energy than an amount of energy to be provided to a load coupled to the switching power converter.

10. The apparatus of claim 1 wherein the apparatus further comprises at least one member a group consisting of:

a boost switch in a switching power converter of a phase cut compatible, dimmable lighting system, wherein the controller is configured to control a switch path power dissipation circuit to control dissipation of excess energy by at least the boost switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter; and

an active circuit to dissipate power at the output of a switching power converter when the switching power converter receives more energy than an amount of energy to be provided to a load coupled to the switching power converter.

11. The apparatus of claim 10 further comprising:

one or more light emitting diodes; and

the switching power converter coupled to the one or more light emitting diodes.

12. An apparatus comprising:

a controller configured to control a flyback switch coupled to a primary-side transformer coil in an output stage of a switching power converter in a phase cut compatible, dimmable lighting system, wherein the controller is further configured to control the flyback switch in an efficient mode and a power dissipation mode, wherein in the efficient mode, the controller is configured to operate the flyback switch to minimize power dissipation in the flyback switch and in the power dissipation mode the controller is configured to operate the flyback switch to increase dissipation of energy in the flyback switch relative to any power dissipation in the flyback switch during operation in the efficient mode.

13. The apparatus of claim 12 wherein the controller is configured to generate a control signal to control conductivity of the flyback switch and in the efficient mode, the controller is further configured to generate the control signal using two states in the efficient mode and is further configured to generate the control signal using at least three states in the power dissipation mode.

14. The apparatus of claim 12 wherein in the efficient mode the controller is configured to generate a control signal to cause a charging current to flow through the flyback switch during a charging phase of the switching power converter and cut-off current through the flyback switch during a flyback phase during the efficient mode and is further configured to limit current through the flyback switch to an intermediate value between the charging current and zero during the power dissipation mode.

15. A method comprising:

controlling a flyback switch coupled to a primary-side transformer coil in an output stage of a switching power converter in a phase cut compatible, dimmable lighting system; and

controlling a power dissipation circuit to dissipate excess energy through the flyback switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter.

16. The method of claim 15 further comprising:

controlling a current source coupled to the flyback switch to control current through the flyback switch during the charging phase of the switching power converter.

17. The method of claim 16 wherein the current source is a constant current source.

18. The method of claim 15 further comprising:

controlling a duration of the charging phase to control an amount of energy dissipated through the flyback switch.

19. The method of claim 15 wherein the power dissipation phase begins at an end of the charging phase and ends before a beginning of a next flyback phase.

20. The method of claim 15 wherein the power dissipation phase begins prior to an end of the boost phase of the switching power converter and ends after a beginning of a next flyback phase of the switching power converter.

21. The method of claim 15 wherein the charging phase occurs during the flyback phase of the switching power converter.

22. The method of claim 15 further comprising:

controlling a member of a group consisting of;

current in the flyback switch, a conduction time of the flyback switch, or the current and the conduction time of the flyback switch.

23. The method of claim 15 further comprising:

dissipating power in a link path of the switching power converter when the switching power converter receives more energy than an amount of energy to be provided to a load coupled to the switching power converter.

24. The method of claim 15 further comprising:

controlling a boost switch in a switching power converter of a phase cut compatible, dimmable lighting system; and

controlling a switch path power dissipation circuit to control dissipation of excess energy by at least the boost switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter.

25. The method of claim 24 further comprising:

dissipating power in a link path of the switching power converter when the switching power converter receives more energy than an amount of energy to be provided to a load coupled to the switching power converter.

26. The method of claim 24 further comprising:

controlling one or more light emitting diodes.

27. An method comprising:

controlling a flyback switch coupled to a primary-side transformer coil in an output stage of a switching power converter in a phase cut compatible, dimmable lighting system; and

controlling the flyback switch in an efficient mode and a power dissipation mode, wherein controlling the flyback switch in the efficient mode comprises;

operating the flyback switch to minimize power dissipation in the flyback switch; and

wherein controlling the flyback switch in the power dissipation mode comprises;

operating the flyback switch to increase dissipation of energy in the flyback switch relative to any power dissipation in the flyback switch during operation in the efficient mode.

28. The method of claim 27 further comprising:

generating a control signal to control conductivity of the flyback switch;

generating the control signal using two states in the efficient mode; and

generating the control signal using at least three states in the power dissipation mode.

29. The method of claim 27 wherein:

in the efficient mode, the method further comprises;

generating a control signal to cause a charging current to flow through the flyback switch during a charging phase of the switching power converter and cut-off current through the flyback switch during a flyback phase during the efficient mode; and

in the power dissipation mode the method further comprises;

limiting current through the flyback switch to an intermediate value between the charging current and zero during the power dissipation mode.