LED Dimming Techniques Using Spread Spectrum Modulation
First Claim
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1. A method for controlling the intensity of light emitted by at least one light emitting diode, comprising:
- modulating a fixed frequency carrier signal using controlled frequency modulation depths to created a first modulated signal with a first set of deterministic frequency components;
applying said first modulated signal to control a current flowing through said light emitting diode to generate a second set of deterministic frequency components; and
applying one or more filter responses to selectively filter one or both of said first set and said second set of deterministic frequency components, wherein bandwidth of said filter responses is adjustable.
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Abstract
Circuits and methods of LED dimming are disclosed. Frequency modulation using controlled modulation depth generates deterministic sidebands of both the fundamental frequency and its harmonics. Various filters including low-pass, band-pass, high-pass and combinations of those are used to selectively filter the deterministic frequency components generated by the frequency modulation to achieve LED dimming.
74 Citations
18 Claims
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1. A method for controlling the intensity of light emitted by at least one light emitting diode, comprising:
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modulating a fixed frequency carrier signal using controlled frequency modulation depths to created a first modulated signal with a first set of deterministic frequency components; applying said first modulated signal to control a current flowing through said light emitting diode to generate a second set of deterministic frequency components; and applying one or more filter responses to selectively filter one or both of said first set and said second set of deterministic frequency components, wherein bandwidth of said filter responses is adjustable. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus that controls the intensity of light emitted by at least one light emitting diode, comprising:
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a spread spectrum modulator configured to modulate a fixed frequency carrier signal using controlled frequency modulation depths to created a first modulated signal with a first set of deterministic frequency components; a controller, in response to said first modulated signal, configured to control a current flowing through said light emitting diode to generate a second set of deterministic frequency components; and one or more filter responses being used to selectively filter one or both of said first set and said second set of deterministic frequency components, wherein bandwidth of said filter responses is adjustable. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification