Secondary-side alternating energy transfer control with inverted reference and LED-derived power supply

• US 9,173,261 B2
• Filed: 06/30/2011
• Issued: 10/27/2015
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Mokry, Wesley L., Melanson, John L.
• Primary Examiner(s): Tran, Thuy Vinh
• Assistant Examiner(s): LUONG, HENRY T
• Application Number:
  US13/173,526
• Publication Number:
  US 20120025722A1
• Time in Patent Office: 1,580 Days
• Field of Search: 315/224, 315/246, 315/244, 315/247, 315/291, 315307-308, 315/312, 315/219, 315/185.R
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A single magnetic storage element is used to provide power to multiple lighting devices, which may be strings of light-emitting diodes (LEDs) of different color. A switching circuit controls alternating application of energy among the multiple lighting devices and another switching circuit may charge the primary winding to different energy levels to control the intensity of the multiple lighting devices. In particular, the multiple lighting devices may be controlled to provide a desired color profile while dimming the lighting devices, while requiring only a single magnetic storage element for supplying energy to the lighting devices.

Claims

1. A circuit for powering two or more lighting devices, the circuit comprising:

at least one output terminal for providing a first output current or voltage to a first one of the lighting devices and providing a second output current or voltage to a second one of the lighting devices;

a first switching circuit coupled to an input power source;

a magnetic storage element having a first winding coupled to the first switching circuit, wherein the first switching circuit charges the magnetic storage element from the input power source during charging intervals of switching cycles of the first switching circuit; and

a second switching circuit coupled to a terminal of the magnetic storage element for selecting, according to a synchronization signal, between providing the first output current or voltage to the first one of the lighting devices and providing the second output current or voltage to the second one of the lighting devices during alternating flyback intervals of the switching cycles that follow the charging intervals of the switching cycles, wherein the second switching circuit comprises a detection circuit for detecting changes in a voltage at the terminal of the magnetic storage element and generating the synchronization signal to provide indications in the corresponding switching cycles that the first switching circuit has commenced charging intervals of the switching cycles in response to detecting the changes in the voltage at the terminal of the magnetic storage element and wherein the second switching circuit alternates a state of the selecting in response to the synchronization signal indicating, in the charging intervals, that a next charging interval has commenced.

2. The circuit of claim 1, further comprising a power supply circuit coupled to a second winding of the magnetic storage element for generating a power supply voltage for providing power to the second switching circuit.

3. The circuit of claim 2, wherein the power supply circuit charges a holding capacitor while the first switching circuit charges the magnetic storage element.

4. The circuit of claim 1, wherein the detection circuit comprises a flip-flop having a clock input coupled to a first terminal of a second winding of the magnetic storage element by a resistor and wherein a power supply return terminal of the flip-flop is coupled to the first terminal of the second winding of the magnetic storage element by a diode, wherein the second terminal of the second winding is coupled to the at least one output terminal, such that when a polarity of a voltage across the second winding is such that the first output current or voltage is being supplied to the first one of the lighting devices, the diode is forward-biased and when the first switching circuit is charging the magnetic storage element, the diode is reverse biased, causing the voltage at the clock input of the flip-flop to toggle the flip-flop to change the state of the selecting.

5. The circuit of claim 1, further comprising a first control circuit for controlling the first switching circuit, wherein the first control circuit controls the first switching circuit to control charging of the magnetic storage element to different energy storage levels during alternating ones of the charging intervals corresponding to the alternating flyback intervals, whereby different amounts of energy are transferred to the individual lighting devices.

6. The circuit of claim 1, wherein the at least one output terminal comprises a first output terminal for supplying the first output current or voltage to the first one of the lighting devices and a second output terminal for supplying the second output current or voltage to the second one of the lighting devices, and wherein the circuit further comprises at least one additional output terminal for providing at least one additional output current or voltage to at least one additional corresponding one of the lighting devices, and wherein the second switching circuit alternatively couples the magnetic storage element to the first output terminal, the second output terminal, and the at least one additional output terminal during the alternating flyback intervals.

7. The circuit of claim 1, wherein the two or more lighting devices are two or more light-emitting diode circuits each having one or more light-emitting diodes connected in series.

8. The circuit of claim 7, wherein the corresponding total forward bias voltages of the two or more light-emitting diode circuits have different values, and wherein the second switching circuit comprises a switching device coupling a first output terminal to a second output terminal, wherein the magnetic storage element is statically coupled to the first output terminal, wherein the first lighting element has a higher total forward bias voltage value than a lower total forward bias voltage value of the second lighting element, whereby when the switching device is disabled the first output current is conducted through the first lighting element, but when the switching device is enabled, the second output current is conducted through the second lighting element.

9. The circuit of claim 1, further comprising a first control circuit for controlling the first switching circuit, wherein the first control circuit controls the first switching circuit to control charging of the first winding of the magnetic storage element to different volt-second product values during alternating ones of the charging intervals corresponding to the alternating flyback intervals, whereby the first output current differs from the second output current and wherein the first control circuit comprises a voltage sensing circuit for sensing differing reflected voltages across the primary winding of the magnetic storage element during the alternating flyback intervals and determining whether the alternating flyback intervals are following the correct corresponding charging intervals, and changing the order of the charging intervals according to a result of the determining.

10. The circuit of claim 1, wherein the at least one output terminal comprises a first output terminal for supplying the first output current or voltage to the first one of the lighting devices and a second output terminal for supplying the second output current or voltage to the second one of the lighting devices.

11. A method of supplying power to multiple lighting devices, comprising:

first controlling charging of a magnetic storage element from a first winding of the magnetic storage element during charging intervals of switching cycles of the first switching circuit;

generating a synchronization signal by detecting changes in a voltage at a terminal of the magnetic storage element to provide indications in the corresponding switching cycles that the charging intervals have commenced;

second controlling discharging of the magnetic storage element to alternate application of energy stored in the magnetic storage element between the multiple lighting devices during alternating flyback intervals of the switching cycles that follow the charging intervals of the switching cycles, according to the synchronization signal, wherein a state of the second controlling is changed in response to the synchronization signal indicating, in the charging intervals, that a next charging interval has commenced;

first providing a first output current or voltage to a first one of the lighting devices during a first one of the flyback intervals; and

second providing a second output current or voltage to a second one of the lighting devices during a second one of the flyback intervals.

12. The method of claim 11, further comprising generating a power supply voltage from a second winding of the magnetic storage element to supply power to a control circuit coupled to the second winding of the magnetic storage element that performs the second controlling.

13. The method of claim 12, wherein the generating a power supply voltage comprises charging a holding capacitor while the first controlling is charging the magnetic storage element.

14. The method of claim 11, wherein the detecting comprises toggling a flip-flop having an input coupled to the second winding of the magnetic storage element in response to the first controlling commencing charging the magnetic storage element.

15. The method of claim 11, further comprising controlling the first switching circuit to control charging of the magnetic storage element to different energy storage levels during alternating ones of the charging intervals corresponding to the alternating flyback intervals, whereby different amounts of energy are transferred to the individual lighting devices.

16. The method of claim 15, further comprising receiving multiple dimming values corresponding to different levels of intensity of the first one of the lighting devices and the second one of the lighting devices, and wherein the first controlling sets the different energy storage levels according to corresponding ones of the multiple dimming values.

17. The method of claim 11, further comprising providing at least one additional output current or voltage to at least one additional corresponding one of the lighting devices, and wherein the second controlling alternatively directs energy from the magnetic storage element to supply the first output current or voltage, the second output current or voltage, and the at least one additional current or voltage during the alternating flyback intervals.

18. The method of claim 11, wherein the two or more lighting devices are two or more light-emitting diode circuits each having one or more light-emitting diodes connected in series, and wherein the first and second providing provide the first output current or voltage and the second output current or voltage to corresponding ones of the light-emitting diode circuits.

19. The method of claim 18, wherein the corresponding total forward bias voltages of the two or more light-emitting diode circuits have different values, and wherein the second controlling comprises controlling a switching device coupling the first lighting device to the second lighting device, wherein the second winding of the magnetic storage element is statically coupled to the first lighting device, wherein the first lighting device has a higher total forward bias voltage value than a lower total forward bias voltage value of the second lighting device, whereby when the switching device is disabled the first output current is conducted through the first lighting device, but when the switching device is enabled, the second output current is conducted through the second lighting device.

20. A circuit for powering two or more lighting devices, the circuit comprising:

at least one output terminal for providing a first output current or voltage to a first one of the lighting devices and providing a second output current or voltage to a second one of the lighting devices;

a first switching circuit coupled to an input power source;

a magnetic storage element having a primary winding coupled to the first switching circuit, wherein the first switching circuit charges the magnetic storage element from the input power source during charging intervals;

a flip-flop having a clock input coupled to a first terminal of a second winding of the magnetic storage element and an output coupled to a gate of a transistor for selecting between providing the first output current or voltage to the first one of the lighting devices and providing the second output current or voltage to the second one of the lighting devices during alternating flyback intervals following the charging intervals, wherein the flip-flop has a power supply return terminal coupled to the first terminal of the second winding by a diode, so that the diode is reverse biased while the first switching circuit charges the magnetic storage element from the input power source; and

a power supply circuit for providing a power supply voltage to the flip-flop, wherein the power supply circuit is coupled to the second winding of the magnetic storage element, wherein the power supply circuit charges a holding capacitor while the first switching circuit charges the magnetic storage element.

21. The circuit of claim 20, wherein the at least one output terminal comprises a first output terminal for supplying the first output current or voltage to the first one of the lighting devices and a second output terminal for supplying the second output current or voltage to the second one of the lighting devices.