Abstract: The invention provides a fixing apparatus including a coil for generating a magnetic field; a heating medium having an electroconductive layer which generates heat by an eddy current by the magnetic field generated by the coil, and adapted to fix an unfixed toner image borne on a recording material by heat; a temperature detecting member for detecting the temperature of the heating medium; a semiconductor switch element for executing an on-off current supply to the coil; and a capacitor connected electrically parallel to the coil; wherein the capacitor executes charging and discharging, and an on-period from the semiconductor switch element to the coil is controlled according to the output of the temperature detecting member.

Abstract: There is provided a switching power supply unit that is capable of performing zero-voltage switching in the entire load region to reduce switching loss and noise and improve the voltage transmission efficiency. The switching power supply unit is comprised of a main switching device, and an auxiliary switching device for controlling resonance so as to prevent power loss accompanying a switching action of the main switching device. A control circuit varies the OFF period during which the main switching device and the auxiliary switching device are ON simultaneously, according to power consumption by a load on an apparatus in which the switching power supply unit is installed.

Abstract: A DC power supply apparatus includes a switching transformer having a switching element, a primary current detection circuit, arranged on a primary side of the transformer, for detecting a current flowing in the switching element, a secondary current detection circuit for detecting an output current from a secondary side of the transformer, and a control circuit for controlling the switching element on the basis of outputs from the primary and secondary current detection circuit.