Controller circuit
First Claim
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1. A controller circuit comprising:
- means for receiving a substantially constant average current from a pulsed current source;
at least two channels each incorporating at least one light emitting diode (LED) and a further channel for acting as a short circuit;
multiplex means arranged to selectively direct current pulses to one of said channels, and to control the frequency with which current pulses are directed to the channels incorporating at least one LED and the frequency with which the current pulses are directed to said channel acting as a short circuit; and
means for varying the ratio of frequencies with which the current pulses are directed to said channels to control the intensity of the LEDs, wherein the current source comprises a switch-mode converter circuit and the multiplex means is operable to switch at a frequency which is substantially synchronous with the switching frequency of the switch-mode converter circuit and during a charge phase thereof.
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Abstract
A circuit used to control the brightness of a number of light emitting diodes (LEDs) in an array, such that the color and brightness of the light produced by the array may be varied. The circuit is optimized to operate at high efficiency, permitting its use in confined spaces with poor cooling. The circuit permits a variety of configurations of LEDs to be controlled and driven from a range of line voltages. The circuit is further optimized to use few components to achieve its function.
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Citations
10 Claims
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1. A controller circuit comprising:
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means for receiving a substantially constant average current from a pulsed current source;
at least two channels each incorporating at least one light emitting diode (LED) and a further channel for acting as a short circuit;
multiplex means arranged to selectively direct current pulses to one of said channels, and to control the frequency with which current pulses are directed to the channels incorporating at least one LED and the frequency with which the current pulses are directed to said channel acting as a short circuit; and
means for varying the ratio of frequencies with which the current pulses are directed to said channels to control the intensity of the LEDs, wherein the current source comprises a switch-mode converter circuit and the multiplex means is operable to switch at a frequency which is substantially synchronous with the switching frequency of the switch-mode converter circuit and during a charge phase thereof. - View Dependent Claims (2, 3, 4, 5)
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6. A controller circuit comprising:
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means for receiving a constant average current from a pulsed current source;
at least two channels incorporating at least one light emitting diode (LED) and a further channel acting as a short circuit;
multiplex means arranged to selectively direct current pulses to one of said channels, and to control the time current pulses which are directed to the channels incorporating at least one LED and the time current pulses which are directed to said channel acting as a short circuit;
means for varying the ratio between the time current pulses which are directed to said channels incorporating LEDs and the time current pulses which are not directed to said channels incorporating LEDs to control the intensity of the LEDs, wherein the constant current source comprises a switch-mode converter and the multiplex means is operable to switch at a frequency which is substantially synchronous with a switching frequency of the switch-mode converter and during a charge phase thereof. - View Dependent Claims (7, 8, 9, 10)
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Specification