System and method for controlling an output illumination level of a lighting system

• US 8,525,432 B2
• Filed: 04/09/2010
• Issued: 09/03/2013
• Est. Priority Date: 04/09/2009
• Status: Active Grant

• Current Assignee: USAI, LLC
• Original Assignee: USAI, LLC
• Inventors: Wray, Donald L.
• Primary Examiner(s): A, Minh D
• Application Number:
  US12/757,333
• Publication Number:
  US 20110001435A1
• Time in Patent Office: 1,243 Days
• Field of Search: 315/291, 315293-295, 315/307, 315311-312, 315/34, 340/5.61, 340/538.15, 340/870.01, 340/870.02
• US Class Current: 315/291
• 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 method of controlling a brightness level of an LED by supplying power to an LED in series with a field effect transistor and a resistor. A first voltage is supplied from a digital potentiometer to an operational amplifier. The field effect transistor is activated based on the first voltage from the operational amplifier and a second voltage is varied across the resistor when the field effect transistor is activated. The varying of the second voltage across the resistor causes a change in the brightness level of the LED.

Claims

1. A system for controlling a brightness level of a Light Emitting Diode comprising:

a Light Emitting Diode (LED);

said LED connected in series with a transistor and a resistor;

a power supply connected to said LED;

a digital potentiometer;

said digital potentiometer supplying a variable output voltage to an operational amplifier;

said operational amplifier having an output connected to said transistor to activate said transistor;

said operational amplifier receiving a voltage developed across said resistor;

wherein said activation of said transistor by said operational amplifier varies a current through said LED to control the brightness level of said LED; and

said digital potentiometer is connected to a negative side of said resistor and to an output of a second operational amplifier to swamp an error of said digital potentiometer.

2. The system of claim 1, wherein said variable output voltage of said digital potentiometer can be varied by at least 256 discrete voltage steps.

3. The system of claim 2, wherein a microcontroller varies said output steps of said digital potentiometer.

4. The system of claim 3, wherein said microcontroller is connected to a transceiver.

5. The system of claim 4, wherein said microcontroller includes an EEPROM which can be programmed by said transceiver.

6. The system of claim 4, wherein said transceiver is connected to a network to allow remote control of said transceiver.

7. The system of claim 6, wherein a remote user can update a program or a firmware installed in said microcontroller.

8. The system of claim 1 wherein a DMX control protocol is used to control said brightness of said LED.

9. The system of claim 1 further comprising a further LED.

10. The system of claim 9 further comprising a further field effect transistor, resistor, operational amplifier and digital potentiometer.

11. The system of claim 1, wherein:

said power supply comprises a voltage source; and

said LED is between said transistor and said voltage source.

12. The system of claim 11, wherein said transistor is positioned between said resistor and said LED.

13. The system of claim 12, wherein:

said operational amplifier has first and second inputs;

said digital potentiometer is connected to said first input of said operational amplifier;

said transistor comprises first, second and third terminals;

said first terminal of said transistor is connected to said LED;

said second terminal of said transistor is connected to said output of said operational amplifier;

said third terminal of said transistor is connected to said resistor; and

said second input of said operational amplifier is connected to said third terminal of said transistor.

14. The system of claim 13, wherein

said transistor comprises a field effect transistor (FET) having a drain, a gate, and a source, and said first, second and third terminals of said transistor comprise said drain, said gate and said source of said FET, respectively;

and

said first input of said operational amplifier is a non-inverting input and said second input of said operational amplifier is an inverting input.

15. A method of controlling a brightness level of an LED comprising the steps of:

supplying power to an LED;

the LED being in series with a transistor and a resistor;

connecting an output of an operational amplifier to the transistor;

supplying a first voltage from a digital potentiometer to a first input of the operational amplifier;

activating the transistor based on a voltage output from the operational amplifier;

varying a current through the LED when the transistor is activated;

supplying a second voltage developed across the resistor to a second input of the operational amplifier to provide a stabilized output of the operational amplifier; and

outputting a voltage from a second operational amplifier and a voltage from a negative side of the resistor to the digital potentiometer to swamp the error of the digital potentiometer;

wherein the varying of the current through the LED changes the brightness level of the LED.

16. The method of claim 15, wherein the first voltage from the digital potentiometer can vary by at least 256 discrete voltage steps.

17. The method of claim 16, wherein a microcontroller varies the voltage steps from the digital potentiometer.

18. The method of claim 17, wherein the microcontroller is connected to a transceiver.

19. The method of claim 18, wherein the transceiver is connected to a network to allow remote control of the transceiver.

20. The method of claim 19, wherein a remote user can update a program or a firmware installed in the microcontroller.

21. The method of claim 15 further comprising controlling a brightness of a further LED.

22. The method of claim 21 further comprising a further field effect transistor, resistor, operational amplifier and digital potentiometer.

23. The method of claim 15, wherein a DMX control protocol is used to control the brightness of the LED.

24. The method of claim 15, wherein said transistor comprises first, second and third terminals, and the power is supplied by a voltage source, the method further comprising the steps of:

connecting the LED to the voltage source and to the first terminal of the transistor;

connecting the output of the operational amplifier to the second terminal of the transistor;

connecting the resistor to the third terminal of the transistor; and

connecting the second input of the operational amplifier the third terminal of the transistor.

25. The method of claim 24, wherein the transistor is a field effect transistor (FET) having a drain, a gate and a source, where the first, second, and third terminals of the transistor comprise the drain, gate and source of the FET, respectively, and where the first and second inputs of the operational amplifier comprise non-inverting and inverting inputs of the operational amplifier, respectively.

26. A method of controlling a brightness level of an LED comprising the steps of:

supplying power to an LED;

the LED being in series with a field effect transistor and a resistor;

supplying a voltage from a digital potentiometer to a first operational amplifier;

activating the field effect transistor based on a voltage from the first operational amplifier;

varying a voltage across the resistor when the field effect transistor is activated;

wherein the varying of the voltage across the resistor changes the brightness level of the LED and;

outputting a voltage from a second operational amplifier and a voltage from a negative side of the resistor to the digital potentiometer to swamp the error of the digital potentiometer.

27. The method of claim 26, wherein the voltage from the digital potentiometer can vary by at least 256 discrete voltage steps.

28. The method of claim 27, wherein a microcontroller varies the voltage steps from the digital potentiometer.

29. The method of claim 28, wherein the microcontroller is connected to a transceiver.

30. The method of claim 29, wherein the transceiver is connected to a network to allow remote control of the transceiver.

31. The method of claim 30, wherein a remote user can update a program or a firmware installed in the microcontroller.

32. The method of claim 26 further comprising controlling a brightness of a further LED.

33. The method of claim 32 further comprising a further field effect transistor, resistor, operational amplifier and digital potentiometer.

34. The method of claim 26, wherein a DMX control protocol is used to control the brightness of the LED.

35. The method of claim 26, wherein the operational amplifier compares the first voltage from the digital potentiometer to a voltage supplied from a source of the field effect transistor to provide a stabilized output of the operational amplifier.

36. A system for controlling an output illumination level of a lighting system comprising:

a voltage source;

an illumination device coupled to said voltage source;

a voltage converter coupled to said illumination device;

a load coupled to said voltage converter;

a controller coupled to said voltage source and a switch;

said controller providing a variable voltage to said switch;

said load connected to said voltage converter such that a voltage developed across said load is fed to said voltage converter; and

wherein the output illumination level of said illumination device varies according to the variable current passing through said illumination device, wherein said controller is a microcontroller and further comprising a digital potentiometer coupled to said microcontroller.

37. The system according to claim 36, wherein said illumination device is an LED.

38. The system according to claim 36, wherein said load is a resistor.

39. The system according to claim 36, wherein said switch is one of at least a Bipolar transistor, JFET, MOSFET, DEPFET, DGMOSFET, DNAFET, FREDFET, HEMT, IGBT, ISFET, MESFET, MODFET, NOMFET and a OFET.

40. The system according to claim 36 wherein said voltage converter comprises a voltage to current converter.

41. A system for controlling a brightness level of a Light Emitting Diode comprising:

a Light Emitting Diode (LED);

said LED connected in series with a field effect transistor (FET) and a resistor;

a digital potentiometer;

said digital potentiometer supplying a variable output voltage to an operational amplifier;

said operational amplifier connected to said FET to activate said FET;

a power supply connected to said LED;

wherein said activation of said FET by said operational amplifier varies a voltage across said resistor adjusting the brightness level of said LED; and

wherein said digital potentiometer is connected to a negative side of said resistor and to an output of a second operational amplifier to swamp an error of said digital potentiometer.