SWITCHING POWER SUPPLY DEVICE

PROBLEM TO BE SOLVED: To provide a switching power supply device capable of obtaining peak power even under low input voltage.SOLUTION: A switching power supply device includes: an on-off control signal formation circuit 24 for forming an on-off control signal to control an output voltage constant, based on an output voltage detected by output voltage detection means 6 and outputting it to a switching element 3; and correction current detection signal generation means 40a for forming a first correction signal having a constant value from start of turn on time of the switching element during a period its duty ratio is less than a predetermined value in response to a signal indicating start of turn on time of the switching element in the on-off control signal forming circuit, forming a second correction signal whose value is increased with time from the value of the first correction signal during the period the duty ratio is a predetermined value or more, and generating a correction current detection signal, by subtracting the first correction signal and the second correction signal in series from the current detection signal.SELECTED DRAWING: Figure 2 【課題】低入力電圧であってもピーク電力を得るスイッチング電源装置。【解決手段】出力電圧検出手段６で検出した出力電圧に基づき出力電圧を一定に制御するためのオン・オフ制御信号を形成してスイッチング素子３に供給するオン・オフ制御信号形成回路２４と、オン・オフ制御信号形成回路におけるスイッチング素子のオン開始時点を示す信号に応答してスイッチング素子のオン開始時点からデューティが所定値未満の期間に一定値を持つ第１の補正信号を形成し、デューティが所定値以上の期間に第１の補正信号の値から時間の経過と共に増大する第２の補正信号を形成し、電流検出信号から第１の補正信号及び第２の補正信号を順次に減算して補正電流検出信号を生成する補正電流検出信号生成手段４０ａとを備える。【選択図】図２