LED lighting system with a multiple mode current control dimming strategy
First Claim
1. A light emitting diode (LED) lighting system comprising:
- a controller to control current in an LED, wherein the controller includes components to respond to a dimming level input to control an active value of the LED current, wherein;
for a first set of dimming levels, the active value varies between a full active value and an intermediate active value of the LED current; and
for a second set of dimming levels, the LED current is duty cycle modulated;
a dimming level strategy module coupled to the controller and having an input to receive a dimmer signal indicating a dimming level, wherein the dimming level strategy module is configured to generate a target active value of the LED current and generate a duty cycle control signal having a duty cycle control value indicating a duty cycle of the LED current, wherein (i) for the first set of dimming levels, the duty cycle control value indicates an LED current duty cycle of approximately 1.0 and (ii) for the second set of dimming levels, the duty cycle control value causes a duty cycle of the LED current to vary in response to varying dimming levels indicated by the dimmer signal; and
a duty cycle modulator coupled to the dimming level strategy module to convert the duty cycle control value into a duty cycle modulated enable signal, wherein a duty cycle of the enable signal is approximately 1.0 for the first set of dimming levels and the duty cycle of the enable signal causes a duty cycle of the LED current to vary in response to dimming levels in the second set of dimming levels;
wherein the controller includes components to control the active value of the LED current so that an average active value of the LED current is approximately equal to the target active value.
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Accused Products
Abstract
A light emitting diode (LED) lighting system includes a controller to control current in one or more LEDs in response to a dimming level input. The LED lighting system implements a dimming strategy having two modes of operation that allow the LED lighting system to dim the LEDs using an active value of an LED current less than a full value LED current while maintaining continuous conduction mode operation. In an active value varying mode of operation, the controller varies an active value of the LED current for a first set of dimming levels. In an active value, duty cycle modulation mode of operation, the controller duty cycle modulates an active value of the LED current for a second set of dimming levels. In at least one embodiment, the active value of the LED current varies from a full active value to an intermediate active value as dimming levels decrease.
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Citations
32 Claims
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1. A light emitting diode (LED) lighting system comprising:
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a controller to control current in an LED, wherein the controller includes components to respond to a dimming level input to control an active value of the LED current, wherein; for a first set of dimming levels, the active value varies between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, the LED current is duty cycle modulated; a dimming level strategy module coupled to the controller and having an input to receive a dimmer signal indicating a dimming level, wherein the dimming level strategy module is configured to generate a target active value of the LED current and generate a duty cycle control signal having a duty cycle control value indicating a duty cycle of the LED current, wherein (i) for the first set of dimming levels, the duty cycle control value indicates an LED current duty cycle of approximately 1.0 and (ii) for the second set of dimming levels, the duty cycle control value causes a duty cycle of the LED current to vary in response to varying dimming levels indicated by the dimmer signal; and a duty cycle modulator coupled to the dimming level strategy module to convert the duty cycle control value into a duty cycle modulated enable signal, wherein a duty cycle of the enable signal is approximately 1.0 for the first set of dimming levels and the duty cycle of the enable signal causes a duty cycle of the LED current to vary in response to dimming levels in the second set of dimming levels; wherein the controller includes components to control the active value of the LED current so that an average active value of the LED current is approximately equal to the target active value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of controlling an LED lighting system comprising:
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receiving a dimmer signal indicating a dimming level; controlling an active value of a current in an LED in response to the dimming level, wherein controlling the active value of the LED current comprises; for a first set of dimming levels, varying the active value between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, duty cycle modulating the LED current; generating a target active value of the LED current; generating a duty cycle control signal having a duty cycle control value indicating a duty cycle of the LED current, wherein (i) for the first set of dimming levels, the duty cycle control value indicates an LED current duty cycle of approximately 1.0 and (ii) for the second set of dimming levels, the duty cycle control value varies between 1.0 and less than 0.5 in response to varying dimming levels indicated by the dimmer signal; and converting the duty cycle control value into a duty cycle modulated enable signal, wherein a duty cycle of the enable signal is approximately 1.0 for the first set of dimming levels and the duty cycle of the enable signal ranges from less than 1.0 to less than 0.5 for the second set of dimming levels; wherein controlling the active value of the LED current further comprises controlling the active value of the LED current so that an average active value of the LED current is approximately equal to the target active value. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for controlling an LED lighting system comprising:
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means for receiving a dimmer signal indicating a dimming level; means for controlling an active value of a current in an LED in response to the dimming level, wherein the means for controlling the active value of the LED current comprises; for a first set of dimming levels, means for varying the active value between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, means for duty cycle modulating the LED current; means for generating a target active value of the LED current; means for generating a duty cycle control signal having a duty cycle control value indicating a duty cycle of the LED current, wherein (i) for the first set of dimming levels, the duty cycle control value indicates an LED current duty cycle of approximately 1.0 and (ii) for the second set of dimming levels, the duty cycle control value varies between 1.0 and less than 0.5 in response to varying dimming levels indicated by the dimmer signal; and means for converting the duty cycle control value into a duty cycle modulated enable signal, wherein a duty cycle of the enable signal is approximately 1.0 for the first set of dimming levels and the duty cycle of the enable signal ranges from less than 1.0 to less than 0.5 for the second set of dimming levels; wherein the means for controlling the active value of the LED current further comprises means for controlling the active value of the LED current so that an average active value of the LED current is approximately equal to the target active value.
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30. A light emitting diode (LED) lighting system comprising:
a controller to control current in an LED, wherein the controller includes components to respond to a dimming level input to control an active value of the LED current, wherein; for a first set of dimming levels, the active value varies between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, the LED current is duty cycle modulated; wherein the controller includes an input to receive an enable signal and, during operation of the controller, the enable signal is duty cycle modulated to cause the controller to duty cycle modulate the LED current for the second set of dimming levels and an average active value of the LED current for dimming levels in the second set of dimming levels is approximately equal to a duty cycle of the enable signal times a ratio of the active value of the LED current to the full value of the LED active value.
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31. A method of controlling an LED lighting system comprising:
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receiving a dimmer signal indicating a dimming level; controlling an active value of a current in an LED in response to the dimming level, wherein controlling the active value of the LED current comprises; for a first set of dimming levels, varying the active value between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, duty cycle modulating the LED current; receiving an enable signal, wherein the enable signal is duty cycle modulated; and in response to dimming levels in the second set of dimming levels, modulating the LED current in accordance with a duty cycle of the enable signal wherein an average active value of the LED current for dimming levels in the second set of dimming levels is approximately equal to a duty cycle of the enable signal times a ratio of the active value of the LED current to the full value of the LED active value.
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32. An apparatus for controlling an LED lighting system comprising:
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means for receiving a dimmer signal indicating a dimming level; means for controlling an active value of a current in an LED in response to the dimming level, wherein the means for controlling the active value of the LED current comprises; for a first set of dimming levels, means for varying the active value between a full active value and an intermediate active value of the LED current; and for a second set of dimming levels, means for duty cycle modulating the LED current; means for receiving an enable signal, wherein the enable signal is duty cycle modulated; and means for modulating the LED current in response to dimming levels in the second set of dimming levels and in accordance with a duty cycle of the enable signal wherein an average active value of the LED current for dimming levels in the second set of dimming levels is approximately equal to a duty cycle of the enable signal times a ratio of the active value of the LED current to the full value of the LED active value.
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Specification