Patent ID: 8320145

Claim:
A switching power source device including a drive pulse generating circuit which outputs a drive pulse whose pulse width is modulated at a predetermined switching frequency, an inverter circuit having a switching element which turns on and off a direct current input voltage in accordance with a drive pulse from the drive pulse generating circuit, generating an alternating current voltage, and a rectification and smoothing circuit which rectifies and smoothes the alternating current voltage, generates an output voltage, and supplies an output current to a load, the switching power source device comprising: current control pulse generating means configured of a target value setting module which outputs a value which, being a predetermined target value relating to a control of the output current, can be changed, a computing module which carries out a computing process relating to the control of the output current based on the target value, and outputs a result of the computation, and a pulse generating module which generates a current control pulse voltage for controlling the output current based on the computation result; a current detecting circuit which detects the output current from the rectification and smoothing circuit or a current flowing in the switching element; and a current limit signal generating circuit which, when the current detected by the current detecting circuit exceeds a reference value set based on the output of the current control pulse generating means, outputs a current limit signal for limiting the current, wherein the drive pulse generating circuit, on the current limit signal being output, operates in such a way that an on-duty of the drive pulse driving the switching element stops widening, or becomes narrower.