Duty factor probing of a triac-based dimmer
First Claim
1. A method of determining a line frequency of an AC power source supplying power to a thyristor-switched dimmer circuit, the method comprising:
- during non-adjacent half cycles of a voltage of the AC power source that supplies power to the thyristor-switched dimmer circuit, predicting zero-crossing times of the AC power source for the non-adjacent half cycles by measuring a voltage at an output of the thyristor-switched dimmer circuit at times other than the zero-crossing times and generating an indication of the zero-crossing times by extrapolating the zero-crossing times from the voltage measured at the times other than the zero-crossing times; and
determining the line frequency from a time interval extending between the predicted zero crossing times of the AC power source.
3 Assignments
0 Petitions
Accused Products
Abstract
A line-frequency determining circuit for coupling to the output of a thyristor-switched dimmer that determines a line-frequency of an AC power source that supplies an input to the thyristor-controlled dimmer permits accurate control of periodic probing of the dimmer output. The probing is performed to predict zero-cross times of the AC power source that, in turn, are used to determine a dimming control value of the thyristor-switched dimmer. A minimum conductance is applied across the output of the dimmer during the 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 probing can be performed at intervals of an odd number of half-cycles of the AC line frequency so that internal dimmer timer operation is not affected by DC offset.
99 Citations
20 Claims
-
1. A method of determining a line frequency of an AC power source supplying power to a thyristor-switched dimmer circuit, the method comprising:
-
during non-adjacent half cycles of a voltage of the AC power source that supplies power to the thyristor-switched dimmer circuit, predicting zero-crossing times of the AC power source for the non-adjacent half cycles by measuring a voltage at an output of the thyristor-switched dimmer circuit at times other than the zero-crossing times and generating an indication of the zero-crossing times by extrapolating the zero-crossing times from the voltage measured at the times other than the zero-crossing times; and determining the line frequency from a time interval extending between the predicted zero crossing times of the AC power source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
- 10. An integrated circuit for operating a circuit that powers one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising a zero-crossing predicting circuit for predicting zero-cross times of a voltage of an AC power source that supplies power to the thyristor-switched dimmer circuit during non-adjacent half cycles of the AC power source by measuring a voltage at an output of the thyristor-switched dimmer circuit at times other than the zero-crossing times, generating an indication of the zero-crossing times by extrapolating the zero-crossing times from the voltage measured at the times other than the zero-crossing times, and determining a frequency of the voltage of the AC power source from a time interval extending between the predicted zero crossing times.
-
19. An integrated circuit for operating a circuit that powers one or more lighting devices from an output of a thyristor-switched dimmer circuit, comprising:
-
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 zero-cross times of a voltage of an AC power source that supplies power to the thyristor-switched dimmer circuit during non-adjacent half cycles of the AC power source by measuring a voltage at an output of the thyristor-switched dimmer circuit at times other than the zero-crossing times, generating an indication of the zero-crossing times by extrapolating the zero-crossing times from the voltage measured at the times other than the zero-crossing times, and determining a frequency of the voltage of the AC power source from a time interval extending between the predicted zero crossing times; and 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 the AC power source, 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 (20)
-
Specification