Systems and methods to control color and brightness of lighting devices

Abstract

Systems and methods are provided to control the color and brightness of LED lighting. A control signal generator generates a hybrid control signal using pulse width modulation and analog control to drive an LED driver with increased resolution to maintain color mixing while adjusting brightness of the LED lighting.

What is claimed is: 
     
         1 . A method to increase a resolution of intensity control in a lighting module comprising an LED, the method comprising:
 determining, at the lighting module, an intensity level for the LED;   generating a first control signal that when coupled to an LED driver results in a first drive signal having a first resolution of intensity control, the first control signal based at least in part on the intensity level;   generating a second control signal that when coupled to the LED driver results in a second drive signal having a second resolution of intensity control, the second control signal based at least in part on the intensity level;   combining the first and second control signals to create a hybrid control signal; and   coupling the hybrid control signal to the LED driver to produce a third drive signal having a third resolution of intensity control, wherein the third resolution of intensity control results in a greater resolution of intensity control than the first resolution of intensity control and the second resolution of intensity control.   
     
     
         2 . The method of  claim 1  wherein the hybrid control signal comprises a pulse width modulation (PWM) signal having an amplitude and a duty cycle. 
     
     
         3 . The method of  claim 2  wherein the amplitude is based at least in part on the first control signal and the duty cycle is based at least in part on the second control signal. 
     
     
         4 . The method of  claim 2  wherein creating the hybrid control signal comprises converting a digital value that is responsive to the amplitude to an analog signal, and modulating the analog signal according to the duty cycle. 
     
     
         5 . The method of  claim 2  wherein creating the hybrid control signal comprises filtering with a low-pass filter a first PWM waveform, a duty cycle of the first PWM waveform based on the amplitude and the filtered first PWM waveform approximating an analog signal having the amplitude, and modulating the analog signal with a second PWM waveform having the duty cycle of the hybrid control signal. 
     
     
         6 . The method of  claim 2  wherein creating the hybrid control signal comprises generating a digital value for predetermined intervals and converting the digital value to an analog value during the predetermined intervals, the digital value based on the amplitude and the predetermined intervals based on the duty cycle. 
     
     
         7 . The method of  claim 2  wherein creating the hybrid control signal comprises averaging a PWM waveform, a duty cycle of the PWM waveform based on the amplitude and the averaged PWM waveform approximating an analog signal having the amplitude, and turning the PWM waveform ON and OFF at predetermined times, the predetermined times based on the duty cycle of the hybrid control signal. 
     
     
         8 . The method of  claim 7  wherein averaging the PWM waveform comprises filtering the PWM waveform with a low-pass filter. 
     
     
         9 . The method of  claim 8  wherein components of the low-pass filter are selected so that a frequency of the PWM waveform is outside of the pass band of the low-pass filter and a frequency of the hybrid control signal is within the pass band. 
     
     
         10 . A lighting module comprising:
 an LED configured to illuminate when driven by an output of an LED driver circuit;   a processor configured to determine an intensity level for the LED, the processor further configured to generate a first control signal that when coupled to the LED driver circuit results in a first drive signal having a first resolution of intensity control and to generate a second control signal that when coupled to the LED driver circuit results in a second drive signal having a second resolution of intensity control, the first and second control signals based at least in part on the intensity level; and   a hybrid control signal generator configured to combine the first and second control signals to create a hybrid control signal, the LED driver circuit configured to receive the hybrid control signal and to output a third drive signal having a third resolution of intensity control, wherein the third resolution of intensity control results in a greater resolution of intensity control than the first resolution of intensity control and the second resolution of intensity control.   
     
     
         11 . The lighting module of  claim 10  wherein the hybrid control signal comprises a pulse width modulation (PWM) signal having an amplitude and a duty cycle. 
     
     
         12 . The lighting module of  claim 11  wherein the amplitude is based at least in part on the first control signal and the duty cycle is based at least in part on the second control signal. 
     
     
         13 . The lighting module of  claim 11  wherein the hybrid control signal generator comprises a microcontroller configured to generate a digital value responsive to the amplitude and a PWM waveform responsive to the duty cycle, and a digital to analog converter (DAC) configured to enable a conversion of the digital value to an analog signal according to the PWM waveform. 
     
     
         14 . The lighting module of  claim 11  wherein the hybrid control signal generator comprises a microcontroller configured to generate a digital value responsive to the amplitude and a PWM waveform responsive to the duty cycle, a digital to analog converter (DAC) configured to convert the digital value to an analog signal, and a switch configured to modulate the analog signal according to PWM waveform. 
     
     
         15 . The lighting module of  claim 11  wherein the hybrid control signal generator comprises a microcontroller configured to generate a first PWM waveform, a low-pass filter configured to average the first PWM waveform to approximate an analog signal having the amplitude, the microcontroller further configured to generate a second PWM waveform having the duty cycle, the hybrid control signal generator further comprising a switch configured to modulate the averaged first PWM waveform with the second PWM waveform. 
     
     
         16 . The lighting module of  claim 11  wherein the hybrid control signal generator comprises a microcontroller configured to generate a digital value for predetermined intervals and a digital to analog converter (DAC) configured to convert the digital value to an analog signal during the predetermined intervals, the digital value based on the amplitude and the predetermined intervals based on the duty cycle. 
     
     
         17 . A method to control color and brightness of a lighting module comprising one or more LEDs, the method comprising:
 decoding data associated with a user-selected color and a user-selected brightness, the decoded data comprising a color ratio and an intensity level;   determining, for each LED of the one or more LEDs, a corresponding amplitude and a corresponding duty cycle of a pulse width modulation (PWM) signal in response to the color ratio at the intensity level; and   generating, for each LED of the one or more LEDs, a corresponding hybrid control signal having the corresponding amplitude and the corresponding duty cycle, each LED of the one or more LEDs further associated with a corresponding hysteretic LED driver;   wherein the corresponding hybrid control signal comprises an analog component and a digital component, and permits the color ratio at varying intensities to be controlled with a level of resolution that is greater than the level of resolution provided by the analog component alone and the level of resolution provided by the digital component alone.   
     
     
         18 . The method of  claim 17  wherein the analog component comprises the corresponding amplitude and the digital component comprises the corresponding duty cycle. 
     
     
         19 . The method of  claim 17  further comprising receiving at the lighting module a data encoded power signal over a two-wire communication network, the data encoded power signal comprising the data associated with the user-selected color and the user-selected brightness for the lighting module, wherein the data encoded power signal forms a sinusoidal waveform between zero crossings. 
     
     
         20 . The method of  claim 17  further comprising providing, for each LED of the one or more LEDs, the corresponding hybrid control signal to the corresponding hysteretic LED driver to generate a corresponding output signal based on the corresponding hybrid control signal, and driving each LED of the one or more LEDs with the corresponding output signal to cause the lighting module to illuminate in response to the user-selected color and the user-selected brightness.