PURPOSE: To provide a power controller which features various previously set inputs controlling stationary power, cold-temperature start boosting, warm-up, and cooling time constants without depending upon the use of a sensor like a thermistor so as to control the operation temperature of a belt fuser.

CONSTITUTION: The controller sets desired power according to the ON/OFF cycle of a system. For cold-temperature starting, stationary plus and boosting power is used and during a warm-up, a boosting level rapidly decreases at a speed set with a warm-up time constant. During a halt (no power applied), a power set value rapidly increases at a speed set with a cooling time constant.