Switching power supply apparatus

A switching power supply apparatus, comprising:

• switching means for forming a rectangular wave voltage by turning ON/OFF an input voltage (Vin),
• an insulating transformer having a primary winding connected to said switching means and a secondary winding connected to an output terminal, the winding ratio of said windings being N:1,
• output voltage forming means, connected to said secondary winding, for forming an output voltage by carrying out rectification and smoothing by using rectifying means, an inductance device and a capacitor, and
• overcurrent protection means for restricting an output current by detecting the peak current of a current flowing through said switching means, wherein
• in said overcurrent protection means, by using said input voltage (Vin), said output voltage (Vout) and the ON/OFF ratio (D) of said switching means, the detected peak current value is corrected by an error signal proportional to the value of (Vout−D×Vout).

A switching power supply apparatus, comprising:

• switching means for forming a rectangular wave voltage by turning ON/OFF an input voltage (Vin),
• an inductance device for storing exciting energy at the time when said switching means is ON and said input voltage is applied and for outputting the stored exciting energy at the time when said switching means is OFF, and
• overcurrent protection means for restricting output current by detecting the peak current (Ip) of the current flowing through said switching means, wherein
• said overcurrent protection means carries out the arithmetic operation of {(1−D)×(Ip+K×Vout)} with respect to the detected peak current Ip and with K used as a constant, and determines the ON period of said switching means so that the arithmetically operated value becomes constant.