Hybrid-control current driver for dimming and color mixing in display and illumination systems

• US 8,120,277 B2
• Filed: 06/04/2008
• Issued: 02/21/2012
• Est. Priority Date: 06/04/2008
• Status: Active Grant

• Current Assignee: Boca Flasher, Inc.
• Original Assignee: Boca Flasher, Inc.
• Inventors: McKinney, Steven J.
• Primary Examiner(s): TRAN, THUY V
• Application Number:
  US12/155,425
• Publication Number:
  US 20090302779A1
• Time in Patent Office: 1,357 Days
• Field of Search: 315/291, 315/294, 315/299, 315/307, 315/312, 315/313, 315/316
• US Class Current: 315/294
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A control/driver circuit produces variable current output for a lighting system providing improved dimming and color-mixing capability by allowing digital modulation control in addition to analog control over a range of illumination intensities. The circuit and method described is preferably adapted to higher current applications such as LED lighting systems using high-power LEDs. The output current of the circuit varies in proportion to the voltage level of an analog control signal, and additionally in proportion to the relative duty cycle of a digital pulsed control input.

Claims

1. An illumination control circuit comprising:

a controlling module comprising;

one or more analog output signals producing output control voltages each individually variable within a range of values, and one or more digital output signals and producing digital pulses between logic “

1” and

logic “

0”

each with relative duty cycles individually variable within a range of values;

one or more intensity modules receiving

said one or more analog output signals and said one or more digital output signals of said controlling module to control one or more illumination sources;

wherein said one or more intensity modules are controlled according to said one or more analog output signals and said one or more digital output signals of said controlling module to vary the intensity of said illumination sources in proportion to a voltage level of said analog output signals, and additionally in proportion to the relative duty cycles of said digital pulses of said one or more digital output signals,

and wherein

said intensity modules each comprise

a switching regulator circuit

containing a switching device

 

wherein said switching device includes an input pin

 

capable of disabling its output

and receiving in its feedback loop one of said one or more analog output signals from said controlling module;

a pair of transistors configured to form an open-drain, non-inverting buffer;

wherein said non-inverting buffer

receives as its input one of said one or more digital output signals from said controlling module, and

produces a buffered digital output signal;

and wherein said buffered digital output signal from said non-inverting buffer is received by said switching device in said switching regulator circuit through said input pin.

2. The illumination control circuit of claim 1 wherein said controlling module further comprises:

a microcontroller comprising

an input/output port, and

one or more output signals, said one or more output signals of said microcontroller each having a first state and a second state; and

one or more digital-to-analog converters each comprising

as an input, the input/output port from said microcontroller, and

an analog output signal.

3. The illumination control circuit of claim 2 wherein said intensity modules each provides

a regulated current or voltage output;

wherein said regulated current or voltage output from said intensity module is controlled according to the analog output signal from one of said one or more digital-to-analog converters when said second input signal from said microcontroller is in its first state,

and wherein said regulated current or voltage output from said intensity module is zero when said second input signal from said microcontroller is in its second state.

4. The illumination control circuit of claim 3 wherein said regulated current or voltage outputs of said intensity modules jointly vary the intensity of said illumination sources in order to achieve a dimming effect.

5. The illumination control circuit of claim 3 wherein said regulated current or voltage outputs of said intensity modules individually vary the intensities of multiple colored illumination sources to vary the hue of the combined output of light.

6. The illumination control circuit of claim 3, wherein the illumination sources comprise light emitting diodes.

7. The illumination control circuit of claim 2, wherein the output signals of said microcontroller are frequency modulated.

8. The illumination control circuit of claim 2, wherein the output signals of said microcontroller are pulse width modulated.

9. The illumination control circuit of claim 1, wherein the illumination sources comprise light emitting diodes.

10. An illumination control circuit comprising:

a microcontroller adapted to write a digital pulsed modulation signal to a power regulating device, and additionally adapted to write an output control signal to a digital-to-analog converter according to programmed instructions;

said digital-to-analog converter having an analog output signal that varies according to said output control signal of said microcontroller;

a power regulating device

receiving said analog output signal of said digital-to-analog converter to control an illumination source,

and receiving said digital pulsed modulation signal of said microcontroller,

and regulating the power delivered to an illumination source to control the intensity of said illumination source;

wherein said power regulating device comprises

a switching regulator circuit

containing a switching device

wherein said switching device includes an input pin capable of disabling its output

and receiving in its feedback loop said analog output signal from said digital-to-analog converter;

a pair of transistors configured to form an open-drain, non-inverting buffer;

wherein said non-inverting buffer

receives as its input said digital pulsed modulation signal of said microcontroller, and

produces a buffered digital output signal;

and wherein said buffered digital output signal from said non-inverting buffer is received by said switching device in said switching regulator circuit through said input pin; and

wherein said power regulating device is controlled according to the analog output signal of said digital-to-analog converter to vary the intensity of said illumination source over

a first range of illumination intensities of said illumination source such that the intensity of the illumination source varies in proportion to the voltage of said analog output signal of said digital-to-analog converter,

and a second range of illumination intensities of said illumination source such that the intensity of said illumination source varies

in proportion to the voltage of the analog output signal of said digital-to-analog converter

and additionally in proportion to a relative duty cycle of said pulsed modulation signal of said microcontroller.

11. An illumination control circuit comprising:

a controlling module comprising

one or more digital output signals each having a first state and a second state,

one or more analog output signals producing output control voltages each individually variable within a range of values;

one or more intensity modules receiving said one or more digital output signals and said one or more analog output signals of said controlling module to control one or more illumination sources;

wherein said one or more intensity modules are controlled

according to said one or more analog output signals of said controlling module to vary the intensity of said one or more illumination sources in proportion to the voltage level of said one or more analog output signals,

and additionally in response to a pulsing of said one or more digital output signals between said first state and said second state;

and wherein each intensity module comprises

a power regulator having in its feedback loop one of said analog output signals from said controlling module,

and each having an output connected to one or more of said illumination sources which

provides a current to said one or more illumination sources proportional to a voltage level of said one or more analog output signals when said one or more digital output signals is in its first state

and provides no current to said one or more illumination sources when said one or more digital output signals is in its second state.

12. The illumination control circuit of claim 11 wherein said feedback loop of said power regulator comprises:

a sense resistor in series with said one or more illumination sources, said sense resistor providing a voltage signal proportional to a current through said one or more illumination sources;

a comparator having as its first input, said voltage signal from said sense resistor, and having as its second input said one or more analog output signals from said controlling module;

said comparator having an output connected to the feedback input of said power regulator;

said output of said comparator being provided in proportional response to a voltage from said sense resistor compared to said one or more analog output signals from said controlling module.

13. The illumination control circuit of claim 11 wherein each power regulator is a constant-current configured buck switching regulator.

14. The illumination control circuit of claim 11 wherein each power regulator is a constant-current configured boost switching regulator.

15. The illumination control circuit of claim 11 wherein each power regulator is a constant-current configured buck-boost switching regulator.