Dimmer having a microprocessor-controlled power supply

• US 7,546,473 B2
• Filed: 06/30/2006
• Issued: 06/09/2009
• Est. Priority Date: 06/30/2005
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Newman, Robert C
• Primary Examiner(s): Lee; Thomas
• Assistant Examiner(s): Brown; Michael J
• Application Number:
  US11/480,146
• Publication Number:
  US 20070001654A1
• Time in Patent Office: 1,075 Days
• Field of Search: 713/300, 713/320, 713/340, 323/208, 323/233, 323/905
• US Class Current: 713/300
• CPC Class Codes: H05B 39/044 continuously H05B39/042 takes precedence
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 323/905 Lamp dimmer structure

Abstract

A power supply for a two-wire load control device supplies power to a microprocessor, which in turn controls the power supply. The power supply comprises an energy storage element, e.g., a capacitor, for producing a DC voltage for powering the microprocessor. The power supply comprises a high impedance circuit for allowing the energy storage element to receive energy at a first rate before the DC voltage is produced and the microprocessor is powered. The power supply further comprises a low-impedance circuit, i.e., a resistor in series electrical connection with a controllably conductive device, for allowing the energy storage element to receive energy at a second rate greater than the first rate. After starting up, the microprocessor is operable to selectively enable and disable the second energy-receiving circuit by rendering the controllably conductive device conductive and non-conductive, respectively. The microprocessor is operable to monitor the power supply and to control the amount of power delivered to an electrical load connected to the load control device in response to the monitoring of the power supply.

Claims

1. A two-wire load control device for control of power delivered to an electrical load from a source of AC voltage, comprising:

a first controllably conductive device adapted to be operatively coupled to the source of AC voltage and to the electrical load for controlling the power delivered to the load;

a microprocessor coupled to the first controllably conductive device for controlling the first controllably conductive device; and

a power supply adapted to be coupled to the source of AC voltage and coupled to the microprocessor for generating a DC voltage to power the microprocessor, the power supply including an energy storage element and a second controllably conductive device for controllably storing energy in the energy storage element;

wherein the microprocessor is operatively coupled to the second controllably conductive device to control the second controllably conductive device,

further wherein the power supply further comprises a low impedance circuit in series electrical connection with the second controllably conductive device and a high impedance circuit in parallel electrical connection with the series combination of the low impedance circuit and the second controllably conductive device;

wherein when the second controllably conductive device is non-conductive, the energy storage element is operable to receive energy through the high impedance circuit, and when the second controllably conductive device is conductive, the energy storage element is operable to receive energy through the low impedance circuit.

2. The load control device of claim 1, wherein the microprocessor monitors the power supply in order to determine whether the energy storage element is receiving energy through the low impedance circuit.

3. The load control device of claim 2, wherein the power supply further comprises a hardware shut-off circuit for causing the second controllably conductive device to become non-conductive when the DC voltage exceeds a predetermined threshold.

4. The load control device of claim 3, wherein the microprocessor controls the second controllably conductive device to become conductive at a predetermined time after a zero-crossing of the AC voltage.

5. The load control device of claim 3, wherein the microprocessor controls the second controllably conductive device to become non-conductive before the DC voltage exceeds the predetermined threshold.

6. The load control device of claim 2, wherein the microprocessor is operable to control the first controllably conductive device in order to control the power delivered to the electrical load in response to monitoring the power supply.

7. The load control device of claim 2, further comprising:

a low-voltage load powered by the DC voltage of the power supply and operable to draw a current from the energy storage element of the power supply;

wherein the microprocessor is operable to control the first controllably conductive device in order to control the power delivered to the electrical load in response to the current drawn by the low-voltage load.

8. The load control device of claim 2, further comprising:

a low-voltage load powered by the DC voltage of the power supply and operable to draw a current from the energy storage element of the power supply;

wherein the microprocessor is operable to control the amount of current drawn by the low-voltage load in response to monitoring the power supply.

9. The load control device of claim 1, wherein the microprocessor controls the second controllably conductive device to become conductive at a predetermined time after a zero-crossing of the AC voltage.

10. The load control device of claim 1, wherein the microprocessor controls the second controllably conductive device to become non-conductive at a predetermined time after a zero-crossing of the AC voltage.

11. The load control device of claim 1, wherein the power supply further comprises a hardware shut-off circuit for causing the second controllably conductive device to become non-conductive when the DC voltage exceeds a predetermined threshold.

12. The load control device of claim 1, further comprising:

a low-voltage load powered by the DC voltage of the power supply and operable to draw a current from the energy storage element of the power supply;

wherein the microprocessor is operable to control the amount of current drawn by the low-voltage load to substantially zero amps for a predetermined number of half-cycles of the AC voltage after a startup of the microprocessor.

13. The load control device of claim 1, wherein the power supply further comprises a third controllably conductive device in series electrical connection with the high impedance circuit, the microprocessor operable to control the third controllably conductive device.

14. A two-wire load control device for control of a load from a source of AC voltage, comprising:

a first controllably conductive device adapted to be coupled in series electrical connection between the load and the source of AC voltage;

a power supply comprising a controllable impedance coupled in series electrical connection with an energy storage element, the power supply operable to provide a DC voltage to the energy storage element, the energy storage element operable to receive energy when the first controllably conductive device is non-conductive; and

a controller powered by the DC voltage of the power supply and coupled to the first controllably conductive device and the controllable impedance for control of the first controllably conductive device and the controllable impedance, respectively;

wherein the controller is operable to control the controllable impedance to a first impedance value to cause the energy storage element to receive energy at a first rate and to control the controllable impedance to a second impedance value to cause the energy storage element to receive energy at a second rate, wherein the second impedance value is substantially smaller than the first impedance value.

15. The load control device of claim 14, wherein the controllable impedance comprises a first resistor in series electrical connection with a second controllably conductive device, wherein the controller is operable to control the second controllably conductive device.

16. The load control device of claim 15, wherein the controllable impedance comprises a second resistor in parallel electrical connection with the series combination of the second controllably conductive device and the first resistor.

17. The power supply of claim 14, wherein the second energy-receiving circuit comprises a first controllably conductive device having a control input, the energy storage element operable to receive energy at the second rate when the first controllably conductive device is conductive;

wherein the controller is operable to render the controllably conductive device conductive and non-conductive.

18. The power supply of claim 17, further comprising:

a hardware shut-off circuit operable to render the first controllably conductive device non-conductive when the DC voltage exceeds a predetermined threshold.

19. The power supply of claim 18, further comprising:

a second controllably conductive device switch having a control input and coupled between the DC voltage and the control input of the first controllably conductive device;

wherein the first controllably conductive device is rendered conductive when the second controllably conductive device is conductive.

20. The power supply of claim 19, wherein the hardware shut-off circuit comprises:

a third controllably conductive device having a control input and coupled between the DC voltage and the control input of the second controllably conductive device;

a resistor coupled to the DC voltage and the control input of the third controllably conductive device; and

a zener diode having a cathode coupled to the junction of the resistor and the control input of the third controllably conductive device;

the series combination of the resistor and the zener diode connected in parallel electrical connection with the energy storage element;

wherein the third controllably conductive device is rendered conductive when the voltage across the zener diode exceeds the break-over voltage of the zener diode.

21. The power supply of claim 18, wherein the controller is operable to render the first controllably conductive device non-conductive before the DC voltage exceeds the predetermined threshold.

22. The power supply of claim 18, wherein the controller is coupled to the hardware shut-off circuit and is operable to determine if the hardware shut-off circuit is rendering the first controllably conductive device non-conductive.

23. The power supply of claim 17, wherein the second energy-receiving circuit comprises a first resistor in series electrical connection with the first controllably conductive device.

24. The power supply of claim 23, wherein the first energy-receiving circuit comprises a second resistor in parallel electrical connection with the series combination of the first controllably conductive device and the first resistor.

25. The power supply of claim 24, wherein the first energy-receiving circuit further comprises a second controllably conductive device in series electrical connection with the second resistor;

the controller operable to render the second controllably conductive device conductive and non-conductive.

26. The power supply of claim 17, wherein the first controllably conductive device comprises a semiconductor switch.

27. The power supply of claim 26, wherein the semiconductor switch comprises a bipolar junction transistor.

28. A two-wire load control device for control of a load from a source of AC voltage, comprising:

a controllably conductive device adapted to be coupled in series electrical connection between the load and the source of AC voltage;

a power supply comprising an energy storage element, a first energy-receiving circuit for the energy storage element, and a second energy-receiving circuit for the energy storage element, the first energy-receiving circuit allowing the energy storage element to receive energy at a first rate, the second energy-receiving circuit allowing the energy storage element to receive energy at a second rate greater than the first rate, the power supply operable to store energy in the energy storage element when the controllably conductive device is non-conductive, the power supply producing a DC voltage; and

a controller powered by the DC voltage of the power supply, the controller operable to control the controllably conductive device and coupled to the power supply to selectively enable and disable the second energy-receiving circuit.

29. A two-wire load control device for control of power delivered to an electrical load from a source of AC voltage, comprising:

a first controllably conductive device adapted to be operatively coupled to the source of AC voltage and to the electrical load for controlling the power delivered to the load;

a microprocessor coupled to the first controllably conductive device for controlling the first controllably conductive device; and

a power supply adapted to be coupled to the source of AC voltage and coupled to the microprocessor for generating a DC voltage to power the microprocessor, the power supply comprising;

an energy storage element;

a second controllably conductive device operatively coupled to the microprocessor and operable to controllably store energy in the energy storage element in response to the microprocessor;

a low impedance circuit in series electrical connection with the second controllably conductive device; and

a high impedance circuit in parallel electrical connection with the series combination of the low impedance circuit and the second controllably conductive device;

wherein when the second controllably conductive device is non-conductive, the energy storage element is operable to receive energy through the high impedance circuit, and when the second controllably conductive device is conductive, the energy storage element is operable to receive energy through the low impedance circuit; and

wherein the microprocessor monitors the power supply in order to determine whether the energy storage element is receiving energy through the low impedance circuit.

30. A power supply for a two-wire load control device for controlling a load from a source of AC voltage, the load control device having a controller, the load control device comprising:

an energy storage element operable to produce a DC voltage for powering the controller;

a first energy-receiving circuit for allowing the energy storage element to receive energy at a first rate; and

a second energy-receiving circuit for allowing the energy storage element to receive energy at a second rate greater than the first rate;

wherein the controller is powered by the DC voltage and is operable to control the power supply to selectively enable and disable the second energy-receiving circuit.

31. A method for generating a DC voltage in a two-wire load control device for controlling the power delivered from an AC power source to an electrical load, the method comprising the steps of:

generating the DC voltage across an energy storage element;

providing the DC voltage to a controller of the load control device; and

controlling with the controller of the load control device the time constant with which the energy storage element charges;

further wherein the step of controlling the time constant comprises selectively charging the energy storage element with a first time constant and with a second time constant greater than the first rate in response to the controller.

32. The method of claim 31, wherein the step of controlling the time constant further comprises charging the energy storage element with the second time constant after a second predetermined time after the zero-crossing of the AC voltage of the AC power source, the second predetermined time closer to the zero-crossing than the first predetermined time.

33. The method of claim 32, wherein the step of controlling the rate further comprises providing a hardware shut-off circuit coupled to the energy storage element for causing the energy storage element to stop charging with the second time constant.

34. The method of claim 33, further comprising the step of:

monitoring the hardware shut-off circuit to determine whether the energy storage element has stopped charging with the second time constant.

35. The method of claim 34, wherein the step of controlling the time constant further comprises causing the energy storage element to stop charging with the second time constant before the hardware shut-off circuit causes the energy storage element to stop charging with the second time constant.

36. The method of claim 34, further comprising the step of:

controlling the power delivered to the electrical load in response to the step of monitoring the hardware shut-off circuit.

37. The method of claim 34, further comprising the steps of:

providing a low-voltage load powered by the DC voltage and operable to draw a current from the energy storage element; and

controlling the power delivered to the electrical load in response to the current drawn by the low-voltage load.

38. The method of claim 34, further comprising the steps of:

providing a low-voltage load powered by the DC voltage and operable to draw a current from the energy storage element; and

controlling the amount of current drawn by the low-voltage load in response to step of monitoring the hardware shut-off circuit.

39. The method of claim 32, further comprising the steps of:

providing a low-voltage load powered by the DC voltage and operable to draw a current from the energy storage element; and

controlling the amount of current drawn by the low-voltage load to substantially zero amps for a predetermined number of half-cycles of the AC voltage after a startup of the controller.

40. The method of claim 31, further comprising the step of:

determining if the DC voltage has exceeded a predetermined voltage;

wherein the step of controlling the time constant further comprises charging the energy storage element with the second time constant when the DC voltage is below the predetermined voltage.

41. The method of claim 40, wherein the step of controlling the time constant further comprises charging the energy storage element with the second time constant before a first predetermined time after a zero-crossing of an AC voltage of the AC power source.

42. The method of claim 31, wherein the step of controlling the time constant further comprises charging the energy storage element at the first time constant before a startup of the controller.

43. The method of claim 42, further comprising the step of:

determining if the DC voltage has exceeded a predetermined voltage;

wherein the step of controlling the time constant comprises selectively charging the energy storage element with a third time constant when the DC voltage is above the predetermined voltage, the third time constant equal to substantially large such that the energy storage element is prevented from charging.

44. A method for generating a DC voltage in a two-wire load control device, the method comprising the steps of:

generating the DC voltage across an energy storage element;

providing the DC voltage to a controller of the load control device;

selectively allowing the energy storage element to receive energy at a first rate and at a second rate greater than the first rate in response to the controller; and

determining when the DC voltage exceeds a predetermined voltage;

wherein the step of controlling the rate further comprises allowing the energy storage element to receive energy at the second rate when the DC voltage is below the predetermined voltage.