High Efficiency Inductor-less Off-Line LED Driver

• US 20130257277A1
• Filed: 07/30/2012
• Published: 10/03/2013
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Zudrell-Koch, Stefan, Knoedgen, Horst
• Granted Patent: US 8,947,007 B2
• Time in Patent Office: Days
• US Class Current: 315/112
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The present document relates to providing power for driving SSL devices. A power converter converts a varying input voltage to supply an output voltage to a SSL device in series with a current source. The power converter comprises one or more capacitors; a plurality of switches to couple the capacitors in a plurality of configurations. A control unit operates the power converter in a plurality of operational modes providing a corresponding plurality of different conversion ratios between the input/output voltages. The operational modes comprise a first phase and a second phase, during which the capacitors are differently arranged. The control unit controls the switches to alternate between the phases at a commutation cycle rate. The control unit sets the operational mode based on the varying input voltage.

Claims

1. A SSL light bulb assembly comprising:

a SSL device;

a driver circuit, converting supply electricity received through an electrical connection module into a controlled drive current for the SSL device, comprising;

a first power converter converting a varying input voltage at an input of the power converter into an output voltage at an output of the power converter supplying the output voltage to the solid state lighting, comprising;

one or more capacitors;

a plurality of switches coupling said one or more capacitors with one another, with the input and/or with the output of the power converter according to a plurality of configurations; and

a control unit operating the power converter in a plurality of operational modes providing a corresponding plurality of different conversion ratios between the input voltage and the output voltage of the power converter, and

a current source at the output of the first power converter, supplying a constant current to the SSL device, when the SSL device is coupled to the output of the first power converter.

2. The light bulb assembly of claim 1, wherein

the input voltage is derived from a rectified version of a mains supply voltage alternating at a mains frequency;

the input voltage varies in accordance to the mains frequency; and

the control unit is configured to measure the input voltage for setting the one of the plurality of operational modes.

3. The light bulb assembly of claim 2, wherein the control unit sets one of the pluralities of operational modes in sync with the mains frequency.

4. The light bulb assembly of claim 1, wherein the control unit sets one of the plurality of operational modes, such that a voltage drop across the current source does not exceed a pre-determined maximum current source voltage.

5. The light bulb assembly of claim 1, wherein the control unit is configured to set one of the plurality of operational modes, such that the output voltage meets or exceeds a pre-determined load voltage of the SSL device.

6. The light bulb assembly of claim 1, wherein a first operational mode of said plurality of operational modes comprises a first phase, during which the one or more capacitors are arranged in a first configuration from said plurality of configurations, and a second phase, during which the one or more capacitors are arranged in a different second configuration from the plurality of configurations.

7. The light bulb assembly of claim 6, wherein the control unit is configured to control the plurality of switches to switch from the first phase to the second phase, thereby operating the power converter in the first operational mode.

8. The light bulb assembly of claim 6, wherein the control unit is configured to set the one of the plurality of operational modes based on the varying input voltage.

9. The light bulb assembly of claim 6, wherein the control unit is configured to repeat the first phase and the succeeding second phase at a commutation cycle rate.

10. The light bulb assembly of claim 9, wherein the control unit is configured to alternate between the first phase and the second phase of the first operational mode, such that an average charge across the one or more capacitors is maintained constant.

11. The light bulb assembly of claim 9, wherein the control unit is continuously modifying the commutation cycle rate.

12. The light bulb assembly of claim 1, wherein the plurality of switches are MOS transistors.

13. The light bulb assembly of claim 1, wherein the control unit is configured to control the current through the SSL device, in particular so as to control the current flowing through the SSL device to be different for at least some of the plurality of operational modes.

14. The light bulb assembly of claim 1, wherein the power converter is implemented as an integrated circuit on a single chip or in a single package, with only the one or more capacitors being external to the integrated circuit.

15. The light bulb assembly of claim 1 wherein the driver circuit is located within a housing of the light bulb.

16. The light bulb assembly of claim 1 wherein the SSL device comprises a plurality of SSL sources.

17. The light bulb assembly of claim 1 wherein a housing of the light bulb provides a heat-sink capability.

18. The light bulb assembly of claim 1 wherein the driver circuit is driving the SSL device requiring a drive voltage, which is high compared to an input voltage of the driver circuit.

19. The light bulb assembly of claim 1 wherein the driver circuit is entirely free of inductive components.

20. The light bulb assembly of claim 1 wherein the current source is deployed in series with the SSL device.

21. The light bulb assembly of claim 1 wherein the power converter converts an rectified input voltage Vin such that a constant voltage Vled is provided across the SSL device and such that the voltage drop Vsrc across the current source is maintained below or at a maximum voltage, thereby ensuring that the power loss at the current source is kept below a maximum power level.

22. The light bulb assembly of claim 21 wherein the plurality of switches of the power converter is switched according to different modes, wherein each mode allows for a different conversion ratio between the rectified input voltage Vin and an output voltage Vout, with the output voltage Vout being the sum of the voltage Vled across the SSL device and the voltage Vsrc across the current source.

23. A driver circuit to control a solid state lighting, the driver circuit comprising:

a first power converter converting a varying input voltage at an input of the power converter into an output voltage at an output of the power converter supplying the output voltage to the solid state lighting, comprising;

one or more capacitors;

a plurality of switches coupling said one or more capacitors with one another, with the input and/or with the output of the power converter according to a plurality of configurations; and

a control unit operating the power converter in a plurality of operational modes providing a corresponding plurality of different conversion ratios between the input voltage and the output voltage of the power converter.

24. The driver circuit of claim 23 wherein a first operational mode of said plurality of operational modes comprises a first phase, during which the one or more capacitors are arranged in a first configuration from said plurality of configurations, and a second phase, during which the one or more capacitors are arranged in a different second configuration from the plurality of configurations.

25. The driver circuit of claim 24, wherein the control unit controls the plurality of switches to switch from the first phase to the second phase, thereby operating the power converter in the first operational mode.

26. The driver circuit of claim 24, wherein the control unit sets the one of the plurality of operational modes based on the varying input voltage.

27. The driver circuit of claim 24, wherein the control unit repeats the first phase and the succeeding second phase at a commutation cycle rate.

28. The driver circuit of claim 27, wherein the control unit alternates between the first phase and the second phase of the first operational mode, such that an average charge across the one or more capacitors is maintained constant.

29. The driver circuit of claim 27, wherein the control unit is continuously modifying the commutation cycle rate.

30. The driver circuit of claim 24, wherein the plurality of switches are MOS transistors.

31. The driver circuit of claim 24, wherein the power converter is implemented as an integrated circuit on a single chip or in a single package, with only the one or more capacitors being external to the integrated circuit.

32. The driver circuit of claim 24 to control a second SSL device, the driver circuit comprising a second power converter for supplying the second SSL device;

wherein

the first and second power converters are operable in a plurality of operational modes comprising respective first phases and second phases; and

when the first power converter is operated in the first phase of a particular operational mode of the plurality of operational modes, the second power converter is operated in the second phase of the particular operational mode of the plurality of operational modes, and vice versa.

33. A power converter to convert a varying input voltage at an input into an output voltage at an output;

wherein the power converter is configured to supply the output voltage to a solid state lighting device in series with a current source;

the power converter comprising;

an input port to receive a rectified input voltage;

a first switch, wherein a first terminal of the switch is connected to the input port and a second terminal of the first switch is connected to a first output port;

a first capacitor, wherein a first terminal is connected to the input port and a second terminal is connected to an anode of a first diode to a cathode of a second diode and to a first terminal of a second capacitor;

said first diode, wherein a cathode is connected to the first output port;

said second diode wherein an anode is connected to a second output port;

said second capacitor, wherein a second terminal is connected to ground;

a second switch wherein a first terminal is connected to the second output port and a second terminal is connected to ground; and

said first and second output ports wherein a load is connected between both output ports.

34. The power converter of claim 33, wherein said first and second diodes are replaced by switches.

35. A power converter to convert a varying input voltage at an input into an output voltage at an output;

wherein the power converter is configured to supply the output voltage to a solid state lighting device in series with a current source;

the power converter comprising;

an input port to receive a rectified input voltage;

a first switch, wherein a first terminal of the switch is connected to the input port and a second terminal of the first switch is connected to a first terminal of a second switch, to a first terminal of a third switch, and to a first terminal of a first capacitor;

said second switch wherein a second terminal is connected to an output port of the power converter;

said third switch wherein a second terminal of the second switch is connected to a first terminal of a second capacitor and to a second terminal of a fourth switch;

said first capacitor, wherein a second terminal is connected to a first terminal of the fourth switch and to a first terminal of a fifth switch;

said fourth switch;

said fifth switch wherein a second terminal of the fifth switch is connected to a second terminal of the second capacitor;

said second capacitor wherein a second terminal is connected to an anode of a first diode and to a cathode of a second diode;

said first diode, wherein a cathode is connected to the output port;

said second diode wherein an anode is connected to ground; and

said output port wherein a load is connected between the output port and ground.

36. The driver circuit of claim 35, wherein said first and second diodes are replaced by switches.

37. A method for converting a varying input voltage into an output voltage for a solid state lighting device in series with a current source;

the method comprising;

(1) providing a SSL, a driver circuit comprising a control unit, a means to couple and decouple a plurality of components, a load current source, and a capacitor

(2) measuring the input voltage;

(3) selecting an operational mode based on the measured input voltage, wherein the selected operational mode provides a conversion ratio between the input voltage and the output voltage and wherein the selected operational mode comprises a first phase and a second phase;

(4) configuring one or more capacitors of the capacitor bank according to a first configuration by said means to couple and decouple a plurality of components during the first phase of the operational mode;

(5) configuring one or more capacitors of the capacitor bank according to a second configuration by said means to couple and decouple a plurality of components during the second phase of the operational mode;

(6) implement the selected operational mode by alternating repeatedly between the first phase of step (4) and the second phase of step (5) at the commutation cycle rate until the end of an execution cycle; and

(7) go back to step (2) after the end of the execution cycle.

38. The method of claim 37, wherein the SSL and the current source are connected in series.

39. The method of claim 37, wherein said a means to couple and decouple a plurality of components are a plurality of switches

40. The method of claim 37, wherein the method is executed by the control unit.

41. The method of claim 40, wherein the method is executed at a certain executing rate wherein the execution rate is dependent on a mains frequency.

42. The method of claim 41, wherein the execution rate is a multiple of the mains frequency which allows for an appropriate sampling of the waveform of the input voltage.

43. The method of claim 37, wherein the configuration of the first phase is used to charge the one or more capacitors and the configuration of the second phase is used to discharge the one or more capacitors.

44. The method of claim 37, wherein the alternating between the first phase and the second phase of the first operational mode is performed such that an average charge across the one or more capacitors is maintained constant.