HIGH-SIDE CURRENT SENSE HYSTERETIC LED CONTROLLER

• US 20080106217A1
• Filed: 10/19/2006
• Published: 05/08/2008
• Est. Priority Date: 10/19/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Schindel, Darren T., De Oto, Leonard
• Granted Patent: US 7,705,547 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]

Abstract

Systems and methods for hysteretically controlling Light Emitting Diodes (LEDs) when the input voltage is greater than or equal to 18 volts. An example system includes one or more LEDs and a circuit electrically coupled to the one or more LEDs. The circuit hysteretically controls an input voltage supplied to the one or more LEDs based on a sensed electric current that passes through the LEDs. The circuit includes a MOSFET switch for switching on and off the input voltage supplied to the one or more LEDs, a current sensing subcircuit including a first integrated circuit (IC) for sensing the current flowing through the one or more LEDs, a hysteretic comparator circuit including a second IC for generating a hysteretic control signal based on the sensed current, and a switch driver including a third IC for controlling operation of the switch based on the generated hysteretic control signal.

Claims

1. A Light Emitting Diode (LED) system comprising:

one or more LEDs; and

a circuit electrically coupled to the one or more LEDs for hysteretically controlling an input voltage supplied to the one or more LEDs,

wherein the circuit is configured to operate with all input voltages within a range of approximately 5 volts to approximately 76 volts.

2. The system of claim 1, wherein the circuit is configured to operate with input surge voltages up to approximately 80 volts.

3. The system of claim 1, wherein the circuit comprises:

a switch for switching on and off the input voltage supplied to the one or more LEDs;

a current sensing subcircuit for sensing the current flowing through the one or more LEDs;

a hysteretic comparator subcircuit for generating a hysteretic control signal based on the sensed current; and

a switch driver for controlling operation of the switch based on the generated hysteretic control signal.

4. The system of claim 3, wherein the switch includes a MOSFET switch.

5. The system of claim 3, wherein the circuit further comprises a storage element configured to store energy when the switch is turned on and the stored energy is dissipated to the one or more LEDs when the switch is turned off.

6. The system of claim 5, wherein the storage element includes an inductor connected in series with the one or more LEDs.

7. The system of claim 3, wherein the current sensing subcircuit comprises:

a resistor connected in series with the one or more LEDs; and

a current sensing integrated circuit connected across the resistor, wherein an output of the current sensing integrated circuit is connected to an input of the hysteretic comparator subcircuit.

8. The system of claim 3, wherein the current sensing subcircuit senses current on a high side of the one or more LEDs.

9. A method for controlling a current through one or more Light Emitting Diodes (LEDs), the method comprising:

sensing current passing through the LEDs; and

hysteretically controlling an input voltage used to power the one or more LEDs based on the sensed current,

wherein the input voltage is within a range of approximately 5 volts to approximately 76 volts.

10. The method of claim 9, wherein sensing current occurs on a high side of the LEDs.

11. The method of claim 9, wherein the input voltage is between approximately 18 volts and approximately 76 volts.

12. The method of claim 9, wherein the input voltage contains voltage surges of up to approximately 80 volts.

13. The method of claim 9, wherein hysteretically controlling comprises:

generating a hysteretic control signal based on the sensed current; and

controlling operation of a MOSFET switch based on the generated hysteretic control signal.

14. The method of claim 13, further comprising:

storing energy in a storage element when the MOSFET switch is turned on; and

dissipating the stored energy through the one or more LEDs when the MOSFET switch is turned off.

15. The method of claim 14, wherein controlling comprises:

receiving the generated hysteretic control signal at a switch driver; and

driving the MOSFET switch based on the received hysteretic control signal.