POWER SUPPLY DEVICE AND IMAGE FORMING APPARATUS

To improve the accuracy in detecting AC voltage during intermittent switching control.SOLUTION: A power supply device comprises: a transformer T1 that has primary winding P1, secondary winding S1, and auxiliary winding P2; a FET 1 that performs a switching operation; a power supply control unit 301 that controls the FET 1; a second rectifying and smoothing circuit that rectifies and smooths the induction voltage of the auxiliary winding P2; and a feedback unit 305 that feeds back the output voltage of the secondary winding S1. The power supply control unit 301 has a measurement unit that measures the length of a stop period. In a switching period for performing the switching operation, upon executing the switching operation of the FET 1 a predetermined number of times, the power supply control unit makes a transition to the stop period, in the stop period for stopping the switching operation, when determining that the output voltage of the secondary winding S1 falls below a target voltage based on the output voltage of the feedback unit 305, makes a transition to the switching period, and estimates the voltage value of AC voltage based on the output voltage of the second rectifying and smoothing unit and the length of the stop period measured by the measurement unit.SELECTED DRAWING: Figure 3 【課題】間欠スイッチング制御時における交流電圧の検知精度を向上させること。【解決手段】１次巻線Ｐ１、２次巻線Ｓ１、及び補助巻線Ｐ２を有するトランスＴ１、スイッチング動作を行うＦＥＴ１、ＦＥＴ１を制御する電源制御部３０１、補助巻線Ｐ２の誘起電圧を整流平滑する第２の整流平滑回路、２次巻線Ｓ１の出力電圧をフィードバックするフィードバック部３０５を備え、電源制御部３０１は、停止期間の長さを計測する計測部を有し、スイッチング動作を行うスイッチング期間においてＦＥＴ１のスイッチング動作を所定の回数、実施すると停止期間に移行し、スイッチング動作を停止させる停止期間においてフィードバック部３０５の出力電圧に基づいて２次巻線Ｓ１の出力電圧が目標電圧よりも低下したと判断するとスイッチング期間に移行し、第２の整流平滑部の出力電圧と計測部によって計測された停止期間の長さとに基づいて交流電圧の電圧値を推定する。【選択図】図３