Multi-Mode Dimmer Interfacing Including Attach State Control

• US 20120049752A1
• Filed: 08/24/2011
• Published: 03/01/2012
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: King, Eric J., Melanson, John L.
• Granted Patent: US 8,847,515 B2
• Time in Patent Office: Days
• US Class Current: 315/210
• CPC Class Codes: H05B 39/044 continuously H05B39/042 takes precedence
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A system and method includes a controller that is configured to coordinate (i) a low impedance path for a dimmer current, (ii) attaching a dimmer to a power converter system at the leading edge of a phase-cut, rectified input voltage, (iii), control of switch mode power conversion, and (iv) an inactive state to, for example, reduce the dimmer current while allowing a dimmer to function normally from cycle to cycle of an alternating current (AC) supply voltage. In at least one embodiment, the dimmer functions normally when the dimmer conducts at a correct phase angle indicated by a dimmer input setting and avoids prematurely resetting while conducting. In at least one embodiment, by coordinating functions (i), (ii), (iii), and (iv) the controller controls a power converter system that is compatible with a triac-based dimmer.

Claims

2. A method comprising:

sensing a leading edge of a dimmer input voltage; and

after the sensing the leading edge of the dimmer input voltage, actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting.

3. The method of claim 2 wherein actively controlling a decreasing transition of a current comprises:

varying an impedance of a variable impedance so that the current through the triac-based dimmer tracks a decreasing function set by a low pass filter.

4. The method of claim 2 wherein varying an impedance comprises varying current from a digitally controlled current digital-to-analog converter.

5. The method of claim 2 wherein the load comprises one or more light emitting diodes.

6. A method comprising:

generating a first signal for a power converter system upon occurrence of a leading edge of a dimmer input voltage, wherein generating the second signal causes the power converter system to draw a current through the dimmer that prevents the dimmer from prematurely resetting during a first portion of the dimmer input voltage following the leading edge.

7. The method of claim 6 wherein the edge of the dimmer input voltage is a leading edge of the dimmer input voltage.

8. The method of claim 6 wherein the first signal is a sense signal representing the dimmer input voltage.

9. The method of claim 6 wherein the second signal comprises a control signal to control conductivity of a switch of a switching power converter.

10. A method wherein a dimmer voltage to a power converter system comprises four states that occur from:

A. an approximately zero volt crossing of the dimmer voltage of a dimmer until a phase cut, leading edge of the dimmer voltage;

B. an end of state A until a steady state value of a dimmer current has reached a predetermined hold value;

C. an end of state B until energy transferred to a load is sufficient to meet at least one energy transfer parameter; and

D. an end of state C until a beginning of state A;

the method comprising;

for state A, enabling a low impedance path for a dimmer current of the dimmer, wherein the impedance of the low impedance path is sufficiently low to maintain a stable phase angle of the dimmer;

for state B;

enabling control of switch mode power conversion of the dimmer voltage;

sensing a leading edge of a dimmer input voltage; and

after the sensing the leading edge of the dimmer input voltage, actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting;

for state C, controlling switch mode power conversion to maintain the dimmer current above a threshold; and

for state D, entering an inactive state, wherein during the inactive state the low impedance path and the control of mode power conversion is disabled.

11. The method of claim 10 wherein the steady state value of the dimmer current is a member of a group consisting of a steady state mean value of the dimmer current, a steady state root mean square value of the dimmer current, or a steady state peak value of the dimmer current.

12. The method of claim 10 wherein the at least one energy transfer parameter comprises a link voltage threshold value, the method further comprising:

determining when a link voltage is less than the link voltage threshold value, wherein sufficient energy is transferred to the load when the link voltage is less than the link voltage threshold value.

13. The method of claim 10 wherein actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting comprises:

damping the current through the triac-based dimmer to ramp down the current through the triac-based dimmer to a predetermined hold value.

14. The method of claim 10 wherein the predetermined hold value is within the range of 25 mA to 75 mA.

15. The method of claim 10 wherein actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting comprises transitioning the dimmer current from a peak attach current value to an approximately constant steady state current value.

16. The method of claim 15 wherein the peak attach current value is in a range of 300-800 mA, and the approximately constant steady state current value is in a range of 25-75 mA.

17. A method comprising:

sensing a leading edge of a dimmer input voltage to a power converter system; and

controlling a dimmer current in accordance with a profile that transfers energy to a power converter system to damp an inductor-capacitor circuit in a dimmer.

18. The method of claim 17 wherein the profile is a function of a member of a group that includes voltage, time, and voltage and time.

19. An apparatus comprising:

a controller configured to;

sense a leading edge of a dimmer input voltage; and

after the sensing the leading edge of the dimmer input voltage, actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting.

20. The apparatus of claim 19 wherein to actively control a decreasing transition of a current, the controller is configured to:

vary an impedance of a variable impedance so that the current through the triac-based dimmer tracks a decreasing function set by a low pass filter.

21. The apparatus of claim 19 wherein the controller includes a digitally controlled current digital-to-analog converter (DAC) and the controller is further configured to vary the impedance by varying current through the DAC.

22. The apparatus of claim 19 wherein the controller further comprises:

a multiplexer having an attach current value input and a peak current value input;

a low pass filter coupled to an output of the multiplexer to generate an output signal having a decreasing transition from the attach current value to the peak current value;

a boost controller coupled to the low pass filter to control current through the dimmer in accordance with the output signal of the low pass filter.

23. The apparatus of claim 19 further comprising:

a power converter system coupled to the controller, wherein the power converter system includes a switching power converter, and the controller is configured to control power conversion of the power converter system including controlling the switching power converter.

24. The method of claim 19 wherein the load comprises one or more light emitting diodes.

25. An apparatus comprising:

a controller configured to generate a first signal for a power converter system upon occurrence of a leading edge of a dimmer input voltage, wherein generating the second signal causes the power converter system to draw a current through the dimmer that prevents the dimmer from prematurely resetting during a first portion of the dimmer input voltage following the leading edge.

26. The apparatus of claim 25 wherein the edge of the dimmer input voltage is a leading edge of the dimmer input voltage.

27. The apparatus of claim 25 wherein the first signal is a sense signal representing the dimmer input voltage.

28. The apparatus of claim 25 wherein the second signal comprises a control signal to control conductivity of a switch of a switching power converter.

29. An apparatus wherein a dimmer voltage to a power converter system comprises four states that occur from:

A. an approximately zero volt crossing of the dimmer voltage of a dimmer until a phase cut, leading edge of the dimmer voltage;

B. an end of state A until a steady state value of a dimmer current has reached a predetermined hold value;

C. an end of state B until energy transferred to a load is sufficient to meet at least one energy transfer parameter; and

D. an end of state C until a beginning of state A;

the apparatus comprising;

a controller configured to;

for state A, enable a low impedance path for a dimmer current of the dimmer, wherein the impedance of the low impedance path is sufficiently low to maintain a stable phase angle of the dimmer;

for state B;

enable control of switch mode power conversion of the dimmer voltage;

sense a leading edge of a dimmer input voltage; and

after the sensing the leading edge of the dimmer input voltage, actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting;

for state C, control switch mode power conversion to maintain the dimmer current above a threshold; and

for state D, enter an inactive state, wherein during the inactive state the low impedance path and the control of mode power conversion is disabled.

30. The apparatus of claim 29 wherein the steady state value of the dimmer current is a member of a group consisting of a steady state mean value of the dimmer current, a steady state root mean square value of the dimmer current, or a steady state peak value of the dimmer current.

31. The apparatus of claim 29 wherein the at least one energy transfer parameter comprises a link voltage threshold value, the method further comprising:

determining when a link voltage is less than the link voltage threshold value, wherein sufficient energy is transferred to the load when the link voltage is less than the link voltage threshold value.

32. The apparatus of claim 29 wherein to actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting the controller is configured to:

damp the current through the triac-based dimmer to ramp down the current through the triac-based dimmer to a predetermined hold value.

33. The apparatus of claim 29 wherein the predetermined hold value is within the range of 25 mA to 75 mA.

34. The apparatus of claim 29 wherein to actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting the controller is configured to:

transition the dimmer current from a peak attach current value to an approximately constant steady state current value.

35. The apparatus of claim 29 wherein the peak attach current value is in a range of 300-800 mA, and the approximately constant steady state current value is in a range of 25-75 mA.

36. An apparatus comprising:

a controller configured to;

sense a leading edge of a dimmer input voltage to a power converter system; and

control a dimmer current in accordance with a profile that transfers energy to a power converter system to damp an inductor-capacitor circuit in a dimmer.

37. The apparatus of claim 36 wherein the profile is a function of a member of a group that includes voltage, time, and voltage and time.