Three-color rgb led color mixing and control by variable frequency modulation
AssigneeMicrochip Technology Incorporated
InventorCharles R. Simmers
Life of this patent
Estimating the term…
Abstract
Perceived output color and intensity (brightness) of light from a three-element red-green-blue (RGB) light emitting diode (LED) or optical combination of three LEDs (red, green and blue) are controlled with three pulse train signals, each having fixed pulse width and voltage amplitude and then increasing or decreasing the frequency (increasing or decreasing the number of pulses over a time period) of these pulse train signals so as to vary the average current through each of the RGB-LEDs. This reduces the level of electro-magnetic interference (EMI) at any one frequency by varying the pulse train energy spectrum over a plurality of frequencies.
Claims20
An apparatus for controlling brightness and color from a grouping of red, green and blue light emitting diodes (LEDs), comprising:
- red, green and blue pulse generating circuits having trigger inputs and pulse outputs, wherein a plurality of trigger signals are applied to each of the trigger inputs and a plurality of pulses therefrom are generated at each of the red, green and blue pulse outputs, wherein each of the plurality of pulses has a constant width and amplitude;
- red, green and blue pulse on-time integrators, each having a pulse input coupled to a respective pulse output of the red, green and blue pulse generating circuits and an integration time interval input, wherein the red, green and blue pulse on-time integrators generate output voltages proportional to percentages of when the amplitudes of the plurality of pulses for each of the red, green and blue pulse outputs are on over an integration time interval;
- red, green and blue operational amplifiers, each having negative and positive inputs and an output, each of the negative inputs is coupled to the output voltage from a respective one of the red, green and blue pulse on-time integrators and each of the positive inputs of the red, green and blue operational amplifiers is coupled to voltage signals representing desired color and light brightness from red, green and blue light emitting diodes (LEDs);
- and
- red, green and blue voltage controlled frequency generators having frequency control inputs and frequency outputs, wherein each of the frequency control inputs is coupled to a respective output of the red, green and blue operational amplifiers, and the frequency outputs generating the plurality of the trigger signals are coupled to the trigger inputs of the red, green and blue pulse generating circuits, whereby the red, green and blue voltage controlled frequency sources cause the red, green and blue pulse generating circuits to produce the plurality of pulses necessary for producing the desired color and light brightness from the red, green and blue LEDs.
An apparatus for controlling brightness and color from a grouping of red, green and blue light emitting diodes (LEDs), comprising:
- red, green and blue pulse generating circuits having trigger inputs and pulse outputs, wherein a plurality of trigger signals are applied to each of the trigger inputs and a plurality of pulses therefrom are generated at each of the red, green and blue pulse outputs, wherein each of the plurality of pulses has a constant width and amplitude;
- a light brightness detector adapted to receive colored light from red, green and blue light emitting diodes (LEDs) and output a voltage proportional to the color light brightness therefrom;
- a brightness control operational amplifier having a negative input coupled to the light brightness detector and a positive input coupled to a voltage signal representing a desired color light brightness from the red, green and blue LEDs;
- red, green and blue gain controlled amplifiers, each having a respective signal input coupled to red, green and blue control signals representing desired color and light brightness from the red, green and blue light LEDs, and a gain control input coupled to an output of the brightness control operational amplifier;
- and
- red, green and blue voltage controlled frequency generators having frequency control inputs and frequency outputs, wherein each of the frequency control inputs is coupled to a respective output of the red, green and blue gain controlled amplifiers, and the frequency outputs generating the plurality of the trigger signals are coupled to the trigger inputs of the red, green and blue pulse generating circuits, whereby the red, green and blue voltage controlled frequency sources cause the red, green and blue pulse generating circuits to produce the plurality of pulses necessary for producing the desired color and light brightness from the red, green and blue LEDs.
A microcontroller for controlling brightness and color from a grouping of red, green and blue light emitting diodes (LEDs), comprising:
- a microcontroller having red, green and blue outputs, a brightness control input and red, green and blue control inputs, the red, green and blue outputs are coupled to a red, green and blue light emitting diodes (LEDs), the brightness control input is coupled to a color light brightness control signal and the red, green and blue control inputs are coupled to red, green and blue control signals;
- and
- the microcontroller generates a plurality of red, green and blue pulses, wherein each of the plurality of red, green and blue pulses has a constant width and amplitude, and light brightness from each of the red, green and blue LEDs is proportional to a percent of time that the plurality of constant width and amplitude red, green and blue pulses are on over an integration time interval.
Dependencies are inferred from the claim text.