High Current Fast Rise And Fall Time LED Driver

• US 20080012507A1
• Filed: 06/22/2007
• Published: 01/17/2008
• Est. Priority Date: 07/07/2006
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Nalbant, Mehmet
• Granted Patent: US 8,188,682 B2
• Time in Patent Office: Days
• US Class Current: 315/306
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

The present invention contemplates a variety of improved techniques for the fast switching of current through, among others, LED loads. A current shunting device is utilized to divert current away from a load at high speed when activated, thus enabling the control of the amount current that flows through the load.

Claims

1. A system comprising:

a current source providing a controlled current;

a load coupled to the current source so as to allow the current from the current source to drive the load; and

one or more current shunting devices configured to divert the current from the current source away from the load.

2. A system as recited in claim 1, wherein the current source is an inductor.

3. A system as recited in claim 1, wherein the current source and its associated switching circuitry are kept at a substantially charged state.

4. A system as recited in claim 1, wherein the current shunting device includes a switch, wherein the switch is a low impedance metal oxide semiconductor field-effect transistor (MOSFET), a bipolar junction transistor (BJT), or an insulated-gate field-effect transistor (IGFET).

5. A system as recited in claim 1, wherein the load includes a light emitting diode (LED) or a string of LEDs.

6. A system as recited in claim 5, wherein the LED is configured to provide light suitable for use with one or more of a rear projection television and a front projector.

8. A system as recited in claim 1, wherein the system includes one or more of synchronous rectification and a freewheeling diode.

10. A system as recited in claim 1, wherein the current shunting device is operable to divert at least a portion of the current from the current source away from the load when activated.

7. (canceled)

9. (canceled)

11. (canceled)

12. A system comprising:

a controlling circuit including;

a current source providing a controlled current; and

a current shunting device configured to divert the current from the current source away from a load when activated and switch the current to the load when not activated; and

said load coupled to the current source so as to allow the current from the current source to drive the load.

13. A system as recited in claim 12, wherein the controlling circuit is an integrated circuit (IC).

14. A system as recited in claim 12, wherein the controlling circuit is operable to perform one or more of, activate the current shunting device, deactivate the current shunting device, and adjust the amplitude of the controlled current.

16. A system as recited in claim 12, wherein the load is configured to provide light suitable for use with one or more of a rear projection television and a front projector.

15. (canceled)

17. (canceled)

18. A circuit for fast switching of current to a light emitting diode (LED) comprising:

one or more LEDs;

a voltage source;

a first switching metal oxide semiconductor field-effect transistor (MOSFET) having a drain, gate, and source, the drain of the first MOSFET coupled to the inductor; and

an inductor coupled to the LED, wherein the inductor is charged by the voltage source through the first MOSFET; and

a control signal operable to activate the first MOSFET and shunt current away from the LED, thereby causing the LED to stop producing light.

19. A circuit as recited in claim 18, wherein:

the control signal comes from one or more of a first pin of an integrated circuit (IC) having configured to drive the gate of the first MOSFET and a control system.

21. A circuit as recited in claim 18, further comprising:

a second MOSFET having a drain, gate, and source, the source of the second MOSFET coupled to the voltage source, the drain of the second MOSFET coupled to the inductor.

22. A circuit as recited in claim 21, wherein:

the control signal is operable to activate the second MOSFET and thereby charge the inductor.

23. A circuit as recited in claim 18, further comprising:

a third MOSFET having a drain, gate, and source, the source of the third MOSFET coupled to the drain of the second MOSFET.

24. A circuit as recited in claim 23, wherein:

the control signal is operable to activate the third MOSFET and thereby charge the inductor.

25. A circuit as recited in claim 18, wherein the LED is configured to provide light suitable for use with one or more of a rear projection television and a front projector.

20. (canceled)

26. (canceled)

27. A method for fast switching of a load comprising:

(a) providing a substantially constant current source;

(b) providing a load;

(c) providing a shunting circuit;

(d) applying a current to the load from the current source;

(e) activating the shunting circuit; and

(f) diverting the current away from the load by the shunting circuitry creating a low impedance connection.

28. A method as recited in claim 27, further comprising:

providing a high frequency pulse train; and

wherein, the shunting circuitry is activated with the pulse train.

29. A method as recited in claim 27, further comprising:

one or more of deactivating the shunting circuitry,

applying the current to the load, activating the shunting circuitry and diverting the current away from the load.

31. A method as recited in claim 27, further comprising:

configuring the load to provide light suitable for use with one or more of a rear projection television and a front projector.

30. (canceled)

32. (canceled)

33. A method for fast switching high current light emitting diodes (LEDs), characterized by controlling at a substantially constant current an inductor current of an inductor coupled to the LEDs, and switching off the LEDs by shunting the inductor current through a low impedance switch to ground thereby diverting current away from the LEDs.

34. A method as recited in claim 33, further comprising:

configuring the LEDs to provide light suitable for use with one or more of a rear projection television and a front projector.

35. (canceled)