Patent ID: 7991313

Claim:
An image forming apparatus comprising: an alternating-current power supply; a developer container containing a developer; a developer carrier that is provided in the developer container and that is configured to carry and convey the developer; an electrode member that opposes the developer carrier to form a pair of electrodes with the developer carrier; and a remaining-amount-of-developer detecting unit configured to apply an alternating-current voltage supplied from the alternating-current power supply to the developer carrier or one electrode of the pair of electrodes and to measure the difference in voltage between the other electrode of the pair of electrodes and the developer carrier or the one electrode of the pair of electrodes in order to detect the remaining amount of the developer in the developer container, wherein the alternating-current power supply includes: a piezoelectric transformer including a ceramic piezoelectric oscillation body; a piezoelectric-transformer driving unit configured to apply a driving voltage to a primary electrode of the piezoelectric transformer in order to excite the ceramic piezoelectric oscillating body; a piezoelectric-transformer driving-signal generating unit configured to apply a driving signal to the piezoelectric-transformer driving unit; a voltage detecting unit configured to detect an alternating-current voltage output from a secondary electrode of the piezoelectric transformer; a voltage setting unit configured to set a target value of the alternating-current voltage output from the secondary electrode of the piezoelectric transformer; and a controlling unit configured to feed back a difference signal between a detection signal supplied from the voltage detecting unit and a setting signal supplied from the voltage setting unit to the piezoelectric-transformer driving-signal generating unit to control the alternating-current voltage, and wherein the alternating-current voltage controlled with the controlling unit is applied to the developer carrier or the one electrode of the pair of electrodes to detect the remaining amount of the developer in the developer container.