Method and apparatus to limit current overshoot and undershoot in light driver

• US 9,198,256 B2
• Filed: 12/20/2011
• Issued: 11/24/2015
• Est. Priority Date: 12/21/2010
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Chen, Yimin, Hillas, Nicholaos, Tripathi, Ajay, Acharya, Kaustuva, Harish Gopala Pillai, Raman Nair
• Primary Examiner(s): Cole, Brandon S
• Application Number:
  US13/996,050
• Publication Number:
  US 20130271040A1
• Time in Patent Office: 1,435 Days
• Field of Search: 315291-311
• US Class Current: 1/1
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light driver having a primary side driver configured to convert an input from a mains power supply to a primary side output, and a secondary side driver coupled to the primary side driver and configured to rectify and filter the primary side output to provide a driver output current for driving a light load. A microcontroller controls the light driver at start-up so that the secondary side driver is powered-on and the primary side driver is in a non-powered state during a soft-start period, and subsequent to the soft-start period the secondary side driver is set to be in a low output state when powered-on and thereafter set to a state so that driver output current of the secondary side driver increases the light output from the light load from an initial dim level to a nominal dim level without flicker.

Claims

1. A light driver, comprising:

a primary side driver configured to convert an input from a mains power supply to a primary side output;

a secondary side driver coupled to the primary side driver and configured to rectify and filter the primary side output to provide a driver output current for driving a light load; and

a microcontroller configured to control the light driver so that the secondary side driver is powered-on and the primary side driver is in a non-powered state during a soft-start period, and subsequent to the soft-start period the primary side driver is set to be in a low output state when powered-on and thereafter set to a state so that driver output current of the secondary side driver increases the light output from the light load from an initial dim level to a nominal dim level without flicker.

2. The light driver of claim 1, wherein the initial dim level is set to about 25% of the nominal dim level.

3. The light driver of claim 1, wherein the secondary side driver provides a feedback signal to set the states of the primary side driver responsive to a soft-start signal and a current reference signal provided by the microcontroller.

4. The light driver of claim 3, wherein the feedback signal is optically coupled from the primary side driver to the secondary side driver.

5. A light driver, comprising:

a primary side driver configured to convert an input from a mains power supply to a primary side output;

a secondary side driver coupled to the primary side driver and configured to rectify and filter the primary side output to provide a driver output current for driving a light load, the secondary side driver providing a feedback signal to the primary side driver responsive to a soft-start signal and a current reference signal; and

a microcontroller configured to provide the soft-start signal and the current reference signal responsive to an input dimming signal indicative of a desired dim level of the light load,

the primary side driver is configured to be off when the soft-start signal is turned on, and after the soft-start signal is turned off to be set responsive to the feedback signal to a low output state and thereafter to an initial state based on the current reference signal.

6. The light driver of claim 5, wherein the current reference signal is set by the microprocessor to an initial dim level and thereafter increases to a nominal dim level.

7. The light driver of claim 6, wherein the initial dim level is set to about 25% of the nominal dim level.

8. The light driver of claim 5, wherein the feedback signal is optically coupled from the primary side driver to the secondary side driver.

9. The light driver of claim 5, wherein the light load comprises an LED module.

10. A light driver, comprising:

a primary side driver configured to convert an input from a mains power supply to a primary side output;

a secondary side driver coupled to the primary side driver and configured to rectify and filter the primary side output current to provide a driver output current for driving a light load, the secondary side driver providing a feedback signal to the primary side driver responsive to a soft-start signal and a current reference signal;

a primary side driver power supply configured to provide a first operating voltage to the primary side driver; and

a secondary side driver power supply configured to provide a second operating voltage to the secondary side driver, the secondary side driver power supply including a microcontroller configured to provide the soft-start signal and the current reference signal to the secondary side driver,

the primary side driver is configured to be cut-off from the second operating voltage when the soft-start signal is turned on, and after the soft-start signal is turned off to be set responsive to the feedback signal to a low output state and thereafter to an initial state based on the current reference signal.

11. The light driver of claim 10, wherein the current reference signal is set by the microprocessor to an initial dim level and thereafter increases to a nominal dim level.

12. The light driver of claim 11, wherein the initial dim level is set to about 25% of the nominal dim level.

13. The light driver of claim 10, wherein the secondary side driver comprises an output control circuit including a subtractor configured to subtract the soft-start signal and the driver output current from the current reference signal to provide the feedback signal.

14. The light driver of claim 10, wherein the primary side driver comprises:

a rectifier configured to limit high frequency components of the input from the mains power supply and rectify the limited input, to provide a rectified waveform;

a boost power factor correction circuit configured to convert the rectified waveform to a fixed voltage;

a half-bridge controller configured to provide a primary side control signal responsive to the feedback signal; and

a half-bridge converter configured to convert the rectified waveform responsive to the primary side control signal, to provide a pulsating signal as the primary side output.

15. The light driver of claim 10, wherein the feedback signal is optically coupled from the primary side driver to the secondary side driver.

16. The light driver of claim 10, wherein the primary side driver comprises a switch configured to selectively disable the operating voltage provided from the primary side driver power supply responsive to a switch control signal provided from the microprocessor.

17. The light driver of claim 16, wherein the switch control signal is optically coupled from the microprocessor to the switch.

18. The light driver of claim 10, wherein the light load comprises an LED module.

19. A method of eliminating flicker from a light source, the method comprising:

converting an input from a mains power supply to a primary side output in a primary side driver stage;

rectifying and filtering the primary side output to provide a driver output current for driving the light source; and

providing control so that the secondary side driver stage is powered-on and the primary side driver stage is in a non-powered state during a soft-start period, and subsequent to the soft-start period the primary side driver stage is set to be in a low output state when powered-on and thereafter set to a state so that driver output current of the secondary side driver stage increases the light output from the light source from an initial dim level to a nominal dim level without flicker.

20. The method of claim 19, wherein the initial dim level is set to about 25% of the nominal dim level.

21. A light driver, comprising:

a primary side driver configured to convert an input from a mains power supply to a primary side output;

a secondary side driver coupled to the primary side driver and configured to rectify and filter the primary side output current to provide a driver output current for driving a light load, the secondary side driver providing a feedback signal to the primary side driver responsive to a soft-start signal;

a primary side driver power supply configured to provide a first operating voltage to the primary side driver; and

a secondary side driver power supply configured to provide a second operating voltage to the secondary side driver, the secondary side driver power supply including a microcontroller configured to provide the soft-start signal to the secondary side driver,

during turning off of the light driver, the primary side driver is configured to be cut-off from the first operating voltage and the feedback signal is set to a low output state responsive to the soft-start signal.