POWER SUPPLY DEVICE AND IMAGE FORMING DEVICE

To provide a power supply device and an image forming device capable of preventing an over-current detection more than necessary because an over-current threshold of the next current can be appropriately switched when a load increases, when an AC power supply is interrupted, or the like.SOLUTION: In an image forming device, a power supply unit includes: a PFC circuit having a PFC control circuit that determines over-current when a voltage between current detection registers exceeds a predetermined value with respect to a primary current flowing through a PFC power device 603 and a PFC output electrolytic capacitor for smoothing a boosted primary voltage; a first over-current threshold switching circuit 130 that detects when an AC input voltage is turned off and connects a current detection register 1009 to a current detection register 605 in series; and a second over-current threshold switching circuit 131 configured to detect that the primary voltage drops to a voltage value V2 and connect a current detection register 2008 to the current detection register 605 in series.SELECTED DRAWING: Figure 4 【課題】次電流の過電流閾値を、負荷増大時、ＡＣ電源の瞬断時等において適切に切り替えることができるので、必要以上に過電流検出が行われるのを防止できる電源装置及び画像形成装置を提供する。【解決手段】画像形成装置において、電源部は、ＰＦＣパワーデバイス６０３に流れる一次電流に対し電流検出抵抗間電圧が所定値以上になると過電流と判断するＰＦＣ制御回路及び昇圧された一次電圧を平滑するＰＦＣ出力電解コンデンサを有するＰＦＣ回路と、ＡＣ入力電圧がオフになるのを検出し、電流検出抵抗６０５に電流検出抵抗１００９を並列に接続した第１の過電流閾値切替回路１３０と、一次電圧が電圧値Ｖ２まで低下するのを検出し、電流検出抵抗６０５に電流検出抵抗２００８を並列に接続した構成とする第２の過電流閾値切替回路１３１と、を備える。【選択図】図４