Patent ID: 8525499

Claim:
A switching power supply circuit which is configured to receive a voltage from a direct current voltage source and supply a direct current power to a load part, the switching power supply circuit comprising: a switching element; a current detection circuit which is serially connected to the switching element, and which is configured to convert a current flowing in the switching element into a voltage and detect the voltage; a control circuit which is configured to output a switch driving signal to the switching element to control an ON/OFF operation of the switching element such that a current flowing in the load part becomes constant; a reference voltage generation circuit which is configured to generate a reference voltage proportional to an ON duty of the switch driving signal; and an error amplification circuit which is configured to output error information between a voltage output from the current detection circuit and the reference voltage, to the control circuit, wherein the control circuit is configured to adjust the ON duty of the switch driving signal based on the error information.