Duty factor probing of a triac-based dimmer
First Claim
1. A method of determining a dimming control value of a thyristor-switched dimmer, the method comprising:
- predicting zero-crossings of a voltage of an AC power source that supplies power to the thyristor-switched dimmer;
probing the output of the thyristor-switched dimmer by periodically or intermittently applying a minimum conductance across the output of the thyristor-switched dimmer from a turn-on time of the thyristor-switched dimmer circuit at least until the predicting has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source;
detecting a leading edge of a waveform of an output voltage of the thyristor-switched dimmer circuit subsequent to the next zero-cross time; and
determining the dimming control value of the thyristor-switched dimmer from a time interval extending from the next zero-cross time of the voltage of the AC power source to the detected leading edge.
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Accused Products
Abstract
A power supply circuit for operating high-efficiency lighting devices from a thyristor-controlled dimmer determines the dimming value, i.e., the dimmer duty factor by periodically probing the dimmer output. A minimum conductance is applied across the output of the dimmer during probing intervals that begin at the turn-on time of the dimmer and last until enough information has been gathered to correctly predict a next zero crossing of the AC line voltage that supplies the input of the dimmer. The dimming value is determined from the time interval between the predicted zero-crossing and a next turn-on time of the dimmer. The probing can be performed at intervals of an odd number of half-cycles of the AC line frequency so that a DC offset is not introduced within internal timing circuits of the dimmer. The AC line frequency can also be determined from a time interval between the predicted zero crossings.
93 Citations
20 Claims
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1. A method of determining a dimming control value of a thyristor-switched dimmer, the method comprising:
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predicting zero-crossings of a voltage of an AC power source that supplies power to the thyristor-switched dimmer; probing the output of the thyristor-switched dimmer by periodically or intermittently applying a minimum conductance across the output of the thyristor-switched dimmer from a turn-on time of the thyristor-switched dimmer circuit at least until the predicting has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source; detecting a leading edge of a waveform of an output voltage of the thyristor-switched dimmer circuit subsequent to the next zero-cross time; and determining the dimming control value of the thyristor-switched dimmer from a time interval extending from the next zero-cross time of the voltage of the AC power source to the detected leading edge. - View Dependent Claims (2, 3, 4, 5)
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6. An integrated circuit for operating a circuit that powers one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:
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a zero-crossing predicting circuit for predicting a next zero-cross time of a voltage of an AC power source that supplies power to the thyristor-switched dimmer circuit; a probing control circuit that intermittently or periodically applies a minimum level of conductance to the output of the thyristor-switched dimmer circuit from a turn-on time of the thyristor-switched dimmer circuit at least until the zero-crossing predicting circuit has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source; a detector for detecting a leading edge of a waveform of an output voltage of the thyristor-switched dimmer circuit subsequent to the next zero-cross time; and a control circuit that determines the dimming control value of the thyristor-switched dimmer from a time interval extending from the next zero-cross time of the voltage of the AC power source to the detected leading edge. - View Dependent Claims (7, 8, 9, 10)
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11. A method of powering one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:
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converting power from the output of the thyristor-switched dimmer circuit to supply the one or more lighting devices; predicting a next zero-cross time of a voltage of an AC power source that supplies power to the thyristor-switched dimmer circuit; probing the output of the thyristor-switched dimmer by periodically or intermittently applying a minimum conductance across the output of the thyristor-switched dimmer during durations of probing cycles, wherein a rate of initiating the probing cycles is less than a half-cycle rate of an AC power source that supplies the thyristor-switched dimmer circuit, whereby some half-cycles of the AC power source are not probed, wherein the durations of the probing cycles extend from a turn-on time of the thyristor-switched dimmer circuit at least until the zero-crossing predicting circuit has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source. - View Dependent Claims (12, 13, 14, 15)
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16. An integrated circuit for operating a circuit that powers one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:
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a power converter control circuit for controlling a power converter for supplying the one or more lighting devices from the output; a zero-crossing predicting circuit for predicting a next zero-cross time of a voltage of an AC power source that supplies power to the thyristor-switched dimmer circuit; a probing control circuit that intermittently or periodically applies a minimum conductance to the output of the thyristor-switched dimmer circuit during durations of probing cycles, wherein a rate of initiating the probing cycles is less than a half-cycle rate of an AC power source that supplies the thyristor-switched dimmer circuit, whereby some half-cycles of the AC power source are not probed, wherein the durations of the probing cycles extend from a turn-on time of the thyristor-switched dimmer circuit at least until the zero-crossing predicting circuit has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source. - View Dependent Claims (17, 18, 19, 20)
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Specification