Patent ID: 8897663

Claim:
An induction heating device comprising: a coil which inductively heats a workpiece of a fuser with an input voltage obtained from an alternating current voltage by rectification; a switching element coupled in series with the coil; a peak voltage detector which detects a peak value of the input voltage; an effective voltage detector which detects an effective value of the input voltage; a crest factor calculator which calculates an actual crest factor of the input voltage based on the peak value of the input voltage which is detected by the peak voltage detector and the effective value of the input voltage which is detected by the effective voltage detector; and a power controller which achieves control of power to the fuser by controlling a duty ratio of ON and OFF periods of the switching element, wherein the power controller calculates the duty ratio of ON and OFF periods of the switching element based on a value of power needed to supply the fuser, the effective value of the input voltage which is detected by the effective voltage detector, a crest factor for a sine-wave input voltage, and the actual crest factor of the input voltage which is calculated by the crest factor calculator, and wherein the power controller calculates the duty ratio of ON and OFF periods of the switching element by using the ratio of the crest factor for a sine-wave input voltage to the actual crest factor of the input voltage which is calculated by the crest factor calculator.