LED DRIVER FOR POWERING AN LED UNIT FROM A ELECTRONIC TRANSFORMER

• US 20120229041A1
• Filed: 11/02/2010
• Published: 09/13/2012
• Est. Priority Date: 11/05/2009
• Status: Active Grant

• Current Assignee: eldoLAB Holding B.V. (Acuity Brands, Inc.)
• Original Assignee: eldoLAB Holding B.V. (Acuity Brands, Inc.)
• Inventors: Saes, Marc, Welten, Petrus Johannes Maria
• Granted Patent: US 9,301,348 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: F21K 9/23 Retrofit light sources for lighting devices with a single fitting for each light source, e.g. for substitution of incandescent lamps with bayonet or threaded fittings
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

An LED driver comprising a power converter for powering an LED unit and a control unit for controlling the power converter is provided. The power converter comprising an input terminal for receiving a rectified AC supply voltage, and an output terminal for supplying a current to the LED unit, and the control unit comprising—an input for receiving a supply signal representative of the supply voltage and—an output for providing a control signal to the power converter The control unit is further arranged to:—determine the control signal for controlling the power converter based on the supply signal, and—control the power converter to supply the current to the LED unit based on the control signal, the current being amplitude modulated in synchronism or in phase with the rectified AC supply voltage.

Claims

1. An LED driver comprising

a power converter for powering an LED unit;

a control unit for controlling the power converter;

the power converter comprising

an input terminal for receiving a rectified AC supply voltage, and

an output terminal for supplying a current to the LED unit,

the control unit comprising

an input for receiving a supply signal representative of the supply voltage and

an output for providing a control signal to the power converter, whereby the control unit is arranged to;

determine the control signal for controlling the power converter based on the supply signal, and

control the power converter to supply the current to the LED unit based on the control signal, the current being amplitude modulated in phase or in synchronism with the rectified AC supply voltage.

2. The LED driver according to claim 1 further comprising a rectifier arranged to receive an AC supply voltage and provide the rectified AC voltage to the input terminal.

3. The LED driver according to claim 1, further comprising an energy storage element connectable to the input terminal.

4. The LED driver according to claim 3, whereby the energy storage element comprises a capacitance.

5. The LED driver according to claim 3 further comprising a first switch for connecting and disconnecting the energy storage element to the input terminal, the first switch being controlled by the control unit, based on the input signal.

6. The LED driver according to claim 4, wherein the control unit is arranged to operate the power converter

in a first mode, thereby charging the capacitance from the rectified AC supply voltage;

and

in a second mode, thereby discharging the capacitance and providing a capacitance discharge current to the power converter for, at least partly, supplying the LED unit.

7. The LED driver according to claim 6 wherein the capacitance is charged in a pulsed mode.

8. The LED driver according to claim 7 wherein the capacitance comprises a plurality of capacitances that are sequentially charged.

9. The LED driver according to claim 1, further comprising a power factor correction device connectable to the input terminal.

10. The LED driver according to claim 9 wherein the power factor correction device is connectable to the rectified AC voltage via a second switch, the second switch being controlled by the control unit, based on the input signal.

11. The LED driver according to claim 9 wherein the power factor correction device comprises a series connection of a capacitance and an inductance or current source.

12. The LED driver according to claim 9 wherein the power factor correction device comprises a capacitance circuit comprising a first and second capacitance, wherein the first and second capacitance are arranged to be charged in series and discharged in parallel.

13. The LED driver according to claim 1, wherein the control signal represents a current set point to be followed by the power converter, the current set point being amplitude modulated based on the supply signal.

14. The LED driver according to claim 5 wherein the energy storage element is arranged to supply the power converter when the rectified AC supply voltage is comparatively low.

15. The LED driver according to claim 1 wherein a peak value of the current is, in use, varied according to the amplitude of the rectified AC supply voltage.

16. The LED driver according to claim 15 wherein the peak value of the current is varied proportional to the amplitude.

17. The LED driver according to claim 15 whereby the variation is applied gradually by only adjusting a current level during a comparatively small part of a period of the rectified AC supply voltage per period of the rectified AC supply voltage.

18. The LED driver according to claim 1 wherein the current comprises a staircase-like profile.

19. The LED driver according to claim 1 wherein the control unit is arranged to control the power converter to apply a current fluctuation during an ascending part or a descending part of the rectified AC supply voltage in order to detect whether or not the supply voltage originates from an electronic transformer.

20. The LED driver according to claim 2 wherein the AC supply voltage is provided by an electronic transformer or a TRIAC dimmer.

21. The LED driver according to claim 1 whereby the rectified AC supply voltage is phase angle modulated by a TRIAC dimmer.

22. The LED driver according to claim 21 whereby the control unit is arranged to determine a phase angle of the phase angle modulation of the TRIAC dimmer from the supply signal and whereby the control signal for controlling the power converter is based on the phase angle.

23. The LED driver according to claim 1 wherein the control unit is arranged to control the power converter to

gradually reduce the amplitude modulation applied to the current and monitor if the supply voltage is sustained, and

if the supply voltage is no longer sustained, gradually increase the amplitude modulation until the supply voltage is sustained again.

24. Method of powering an LED unit by an LED driver, the method comprising the steps of:

a. providing a rectified AC supply voltage to an input terminal of a power converter of the LED driver;

b. receiving a supply signal representative of the supply voltage at an input of a control unit of the LED driver;

c. determining a control signal for controlling the power converter based on the supply signal; and

d. controlling the power converter to supply a current to the LED unit based on the control signal, whereby the current is amplitude modulated in phase with the rectified AC supply voltage.