Controlled power dissipation in a lighting system

Patent metadata

Field	Value
Publication number	US-9497850-B2
Application number	US-201113289931-A
Country	US
Kind code	B2
Filing date	Nov 4, 2011
Priority date	Nov 4, 2010
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

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.

First claim

What is claimed is:

1. An apparatus comprising:
a controller configured to generate a first control signal 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 generate a second control signal to control a power dissipation circuit coupled in series with the flyback switch to dissipate excess energy in the flyback switch during a controlled power dissipation phase, and the controlled power dissipation phase exclusively occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter, wherein the excess energy comprises more energy than an amount of energy to be provided to a load coupled to the switching power converter plus inherent energy losses.

2. The apparatus of claim 1 further comprising:
a current source coupled to the flyback switch and controlled by the controller 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 in 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 charging 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, to dissipate excess energy representing more energy than an amount of energy to be provided to a load coupled to the switching power converter plus inherent energy losses, 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.

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, wherein the at least three states in the power dissipation mode occur during a time beginning with a charging phase of the primary-side transformer coil and an end of an immediately subsequent flyback phase of the primary-side transformer coil.

14. The apparatus of claim 12 wherein the controller is configured to intersperse multiple efficient and power dissipation modes during a charging phase of the switching power converter and during a flyback phase.

15. A method comprising:
controlling with a first control signal 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 with a second control signal a power dissipation circuit coupled in series with the flyback switch to dissipate excess energy in the flyback switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs exclusively after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter, wherein the excess energy comprises more energy than an amount of energy to be provided to a load coupled to the switching power converter plus inherent energy losses.

16. The method of claim 15 further comprising:
controlling a current source, coupled to the flyback switch, and the flyback switch with a controller 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 in 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 charging 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: cur

Assignees

• Melanson John L
• King Eric J
• Koninklijke Philips Nv

Inventors

• Melanson John L
• King Eric J

Classifications

• H05B47/10

  Controlling the light source · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H05B45/395

  Linear regulators · CPC title

• H05B45/46

  having LEDs disposed in parallel lines · CPC title

• H05B45/44

  with an active control inside an LED matrix · CPC title