Dimmer with improved noise immunity
AssigneeLeviton Manufacturing Co., Inc.
InventorsMichael Ostrovsky, Ozgur Keser
Life of this patent
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Abstract
A zero-crossing detection method, and devices incorporating the method, enable a selectively enabled bias to pull-up a zero-crossing signal, thereby enabling monitoring of the zero-crossing of both half-cycles of the alternating current (AC). This improves synchronization of the device in noisy environments and enables the detection of dimming problems during either half-cycle. Aspects can detect improper dimmer firing events on either polarity of the power cycle and restore normal dimmer operations when needed.
Claims28
A dimmer for controlling conduction of a supply of alternating current (AC) power to a load, the dimmer comprising:
- a line input terminal and a load output terminal, the line input terminal configured to be electrically coupled to the supply of AC power, and the load output terminal configured to be electrically coupled to the load;
- a switching circuit electrically coupled in series between the line input terminal and the load output terminal, the switching circuit configured to be selectively controlled between an ON state and an OFF state, the switching;
- circuit having a control input configured to receive a firing signal;
- a zero-crossing detector circuit configured to output a zero-crossing signal having a voltage level indicative of a zero-crossing of the AC power, the zero-crossing signal having a substantially square waveform varying between a low voltage level of substantially zero, a positive intermediate voltage level, and a positive high voltage level;
- a controller including a zero-crossing input, the zero-crossing input configured to receive the zero-crossing signal;
- and
- a selectively enabled bias arranged and configured to be selectively electrically coupled to the zero-crossing input;
- wherein the controller is configured to:
- selectively enable the bias to raise the voltage level of the zero-crossing signal from the low voltage level to the positive intermediate voltage level;
- and
- execute a synchronization algorithm to periodically provide the firing signal to the control input in accordance with a timing of the AC power.
A method of operating a dimmer, the dimmer comprising a line input terminal configured to be electrically coupled to a supply of AC power, a load output terminal configured to be electrically coupled to a load, a switching circuit electrically coupled in series between the line input terminal and the load output terminal, a zero-crossing detector circuit configured to output a zero-crossing signal having a voltage level indicative of a zero-crossings of the AC power, the zero-crossing signal having a substantially square waveform, a controller including a zero-crossing input configured to receive the zero-crossing signal, and a bias arranged and configured to be selectively enabled by the controller to electrically couple to the zero-crossing input, the method comprising:
- determining a firing time based on a desired dimming level and a parameter of the AC power;
- detecting a first zero-crossing time t0 when the voltage level of the zero-crossing signal transitions from a low voltage level of substantially zero to a positive high voltage level;
- calculating a time t1 relative to t0 based on the firing time;
- providing a first firing signal at t1 to the switching circuit;
- enabling the bias;
- performing a first detection of whether the zero-crossing signal transitioned to a positive intermediate voltage level;
- detecting a second zero-crossing time t2 when the zero-crossing signal transitions to the low voltage level;
- calculating a time t3 relative to t2 based on the firing time;
- providing a second firing signal at t3 to the switching circuit;
- performing a second detection of whether the zero-crossing signal transitioned to the positive intermediate voltage level;
- and
- disabling the bias.
A zero-crossing detector circuit for use in a dimmer having a switching circuit and a controller, the zero-crossing detector circuit comprising:
- an input configured to be electrically coupled to alternating current (AC) power;
- and
- an output configured to be electrically coupled to the controller;
- wherein the zero-crossing detector circuit is configured to provide a tri-state zero-crossing signal to the output, the tri-state zero-crossing signal comprising a low voltage level of substantially zero, a positive intermediate voltage level, and a positive high voltage level.
Dependencies are inferred from the claim text.