Duty cycle based AC power control with reduced voltage fluctuations

A heater segment (10) for phase change inkjet printer and a switch (12) are coupled across an AC line (14). A generator (18) supplies control signal to the switch, for activation of the heater segment. The generator has registers (22,24) in which the control signal is stored. The AC line is coupled to A/D converter (34) via a step down transformer (32), whose output is in the form of a series of duty cycle pulses having a pulse density generated according to the stored control signal. The duty cycle pulses actuate the segments in a condition that the total power spectrum frequency for the pulses is shifted to an aggregate pulse repetition carrier frequency that is greater than a flicker frequency. A pair of multiplexers (26,28) and an output buffer amplifier (30) are also provided in the generator. The multiplexer (26) coupled to a data bus, receives a one bit input value, whose output is coupled to the register (22). A write signal acts as a control signal for the multiplexer (26) to write the input one-bit. The outputs of both the registers, are input to the multiplexer (28) whose output is given as input to the register (24). The output of the register (24) is applied to the optocoupler, via an amplifier (30). The multiplexer (28) is controlled by an interrupt signal which is also used to reset the register (22). The pulse signal from the converter is input to a line synchronization processing circuit (36) that generates a hardware interrupt signal (IRQ) at a fixed interval relative to every zero crossing of the power signal on the AC line. An independent claim is also included for a method of actuating devices connected to AC power line.