Power control for a printer fuser

A method of delivering AC power at different magnitudes to drive a load, comprising:

• sensing a zero crossing of an AC power signal having recurring AC cycles to identify a subsequent three cycles, including a 1st cycle, a 2nd cycle and a 3rd cycle, said three cycles defining respective AC power cycles;
• controlling an AC switch in a manner to deliver a desired amount of AC power to the load;
• for delivering from about zero power to about 33% power, delivering about zero power in two cycles, and in the one cycle controlling the AC switch using a trigger pulse occurring at a desired phase angle of the AC signal to deliver a desired magnitude of power;
• for delivering power from a level of about 33% to about 66%, in one cycle delivering substantially no power, and in another cycle delivering substantially full power, and in yet another cycle controlling the AC switch using a trigger pulse occurring at a desired phase angle of the AC signal to deliver a desired magnitude of power to the load;
• and
• for delivering power from at a level of about 66% to about full power, in one cycle delivering substantially full power, and in another cycle delivering substantially full power, and in yet another cycle controlling the AC switch using a trigger pulse occurring at a desired phase angle of the AC signal to deliver a desired magnitude of power to the load.

A reproduction machine, comprising:

• a programmed controller;
• a fuser having a heater;
• a table programmed in said controller, said table defining respective timing delays corresponding to different power magnitudes;
• a zero crossing detector for detecting zero crossings of an AC signal used to drive said fuser heater, and said programmed controller responsive to respective zero crossings for defining at least a first cycle and second cycle;
• and
• a heater control having an AC switch, said heater control for receiving the timing delays from said programmed controller for triggering said AC switch at different times in said first cycle and said second cycle.