Switching control in electrical load controllers

An electrical load controller for controlling conduction of a supply of alternating current (AC) power to a load, the supply of AC power having an AC waveform, the AC waveform oscillating though full cycles, each full cycle comprising a positive half cycle and a negative half cycle of the AC waveform, the electrical load controller comprising:

• a line input terminal and a load output terminal, the line input terminal configured to be electrically coupled to a supply of AC power, and the 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, the switching circuit having an ON state in which the switching circuit conducts the supply of AC power to the load, and an OFF state in which the switching circuit does not conduct the supply of AC power to the load;
• and
• a controller, the controller configured to perform a method comprising:
• detecting zero-crossings of the AC waveform;
• determining, using the detected zero-crossings, a plurality of periods, each period corresponding to a full cycle of the AC waveform, wherein the determined periods are a fixed number of periods of a plurality of most recent full cycles of the AC waveform;
• determining a frequency of the AC waveform based on the determined plurality of periods of the full cycles of the AC waveform;
• and
• controlling the supply of AC power to the load based on the determined frequency of the AC waveform, wherein the controlling uses the determined frequency to fire the switching circuit of the electrical load controller in a plurality of half cycles of the AC waveform to selectively control the switching circuit to conduct the AC power to the load.

A method of operating an electrical load controller, the method comprising:

• detecting, by receiving an input by a microprocessor of the electrical load controller, zero-crossings of an alternating current (AC) waveform of a supply of AC power, the AC waveform oscillating though full cycles, each full cycle comprising a positive half cycle and a negative half cycle of the AC waveform, wherein the detected zero-crossings of the AC waveform all occur at either negative-going transitions or positive-going transitions of the AC waveform, and wherein the microprocessor is configured to detect the zero-crossings (i) at the negative-going transitions and ignore the positive-going transitions of the AC waveform, or (ii) at the positive-going transitions and ignore the negative-going transitions of the AC waveform;
• determining, using the detected zero-crossings, a plurality of periods, each period corresponding to a full cycle of the AC waveform;
• determining a frequency of the AC waveform based on the determined plurality of periods of the full cycles of the AC waveform;
• and
• controlling a supply of AC power to a load based on the determined frequency of the AC waveform, wherein the controlling uses the determined frequency to fire a switching circuit of the electrical load controller in a plurality of half cycles of the AC waveform to selectively control the switching circuit to conduct the AC power to the load.