| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit, a control method thereof, a heating unit and an image forming apparatus which can control so that these load maintains fixed setting conditions even if the condition of input power source is not good. SOLUTION: In this apparatus, when a zero crossing detection circuit 12 detects that input power source voltage from an ac power supply 1 becomes below certain threshold value, the detected signal is output to an engine controller 11 as a pulse signal, and the engine controller 11 sends an on-signal with a stated amount of a phase angle based on the pulse signal, and phase control of the electric power supply to a ceramic heater 24 is performed by sending the on-signal. When the pulse signal from the zero crossing detection circuit 12 during the period in which the on-signal is sending is detected, or when pulsing periods of the pulse signals are except a stated amount of pulse periods, the pulse signals are made ignored. COPYRIGHT: (C)2004,JPO
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