WIDE VOLTAGE, HIGH EFFICIENCY LED DRIVER CIRCUIT

• US 20090315484A1
• Filed: 04/29/2009
• Published: 12/24/2009
• Est. Priority Date: 04/29/2008
• Status: Active Grant

• Current Assignee: Dan J. And Denise L. Costa 1997 Family Trust
• Original Assignee: IVUS Energy Innovations Incorporated
• Inventors: CEGNAR, ERIK J., JESSUP, FRED, ALEXANDER, DAVID G., MAUGHAN, MIKE
• Granted Patent: US 8,203,281 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H05B 45/38 using boost topology

Abstract

An electrical circuit and method for driving light emitting diodes with a constant current via a high efficiency DC-DC converter controlled by a digital controller through pulse width modulation (PWM).

Claims

1. A method of driving at least one light emitting diode, said method comprising the steps of:

generating an internal reference current;

measuring the current from a DC-DC boost converter powered by a power source, said DC-DC boost converter driving said at least one light emitting diode;

supplying said measured current and said internal reference current to a closed loop control;

using said closed loop control to generate a PWM signal;

controlling the output current of said DC-DC boost converter using said PWM signal; and

driving said at least one light emitting diode with said output current.

2. The method of claim 1, wherein the said measured current is determined by measuring the voltage across a measurement resistor, filtering the measured voltage to create a filtered voltage, amplifying the filtered voltage to create an amplified signal, and converting the amplified signal to create said measured current.

3. The method of claim 2, wherein said amplification step is accomplished using an operational amplifier.

4. The method of claim 1, wherein the power source is at least one ultracapacitor.

5. The method of claim 1, wherein said power source is a plurality ultracapacitors connected in series, parallel or combinations of series and parallel.

6. The method of claim 1, wherein said internal reference current can be changed based upon user input.

7. The method of claim 1, wherein the power source is at least one battery.

8. The method of claim 1, wherein said power source is a plurality batteries connected in series, parallel or combinations of series and parallel.

9. The method of claim 1, wherein said internal reference current can be changed based upon temperature.

10. The method of claim 1, wherein said internal reference current can be changed based upon time.

11. The method of claim 1, wherein said closed loop control is a proportional-integral-derivative control.

12. The method of claim 1, wherein said closed loop control is a proportional-integral control.

13. The method of claim 1, wherein said closed loop control is a proportional derivative control.

14. The method of claim 1, wherein said closed loop control is an integral control.

15. A LED driver circuit for powering a plurality of light emitting diodes with a power source, said circuit comprising:

a DC-DC boost converter powered by said power source, said DC-DC boost converter for providing current to said light emitting diodes, said DC-DC boost converter controlled by a microcontroller through pulse width modulation (PWM);

a current feedback circuit for measuring the output of said DC-DC boost converter, said current feedback circuit comprising a measurement resistor connected in series with said light emitting diodes, wherein voltage measured across said measurement resistor can be filtered by a filter and amplified by an operational amplifier to create an amplified signal; and

said microcontroller, said microcontroller for generating a reference current, said microcontroller comprising a PWM generator for generating a PWM signal based on the difference between said measured current and said reference current, said PWM signal for controlling current output of said DC-DC boost converter.

16. The LED driver circuit of claim 15, wherein said amplified signal is analog, and wherein said microcontroller further comprises an analog to digital converter for converting said analog amplified signal to said measured current which is digital.

17. The LED driver circuit of claim 15, wherein said at least one light emitting diode comprises a plurality of series connected light emitting diodes.

18. The LED driver circuit of claim 15, wherein said power source is at least one ultracapacitor or at least one battery.

19. The LED driver circuit of claim 18, wherein said power source is a plurality of ultracapacitors connected in series, parallel or a combination of series and parallel.

20. A LED driver circuit for powering a plurality of series connected light emitting diodes with a plurality of series connected ultracapacitors, said circuit comprising:

a DC-DC boost converter powered by said power source, said DC-DC boost converter for providing current to said light emitting diodes, said DC-DC boost converter controlled by a microcontroller through pulse width modulation (PWM);

a current feedback circuit for measuring the output of said DC-DC boost converter, said current feedback circuit comprising a measurement resistor connected in series with said light emitting diodes, wherein voltage measured across said measurement resistor can be filtered by a filter and amplified by an operational amplifier to create an analog amplified signal; and

said microcontroller, said microcontroller for generating a digital reference current, said microcontroller comprising an analog to digital converter for converting said analog amplified signal to a digital measured current, said microcontroller comprising a PWM generator for generating a PWM signal based on the difference between said measured current and said reference current, said PWM signal for controlling current output of said DC-DC boost converter.