Patent ID: 7859239

Claim:
A switching regulator configured to switch according to an input signal and perform PWM control with a PWM pulse signal generated to cause an output voltage from an output terminal to be a given constant voltage with respect to a switching element for charging an inductor with an input voltage to an input terminal, the switching regulator comprising: a control logic circuit configured to receive the PWM pulse signal; and a pulse width limiting circuit configured to limit a duty cycle of the PWM pulse signal so that a period of time the switching element remains ON is a given minimum value or greater, wherein the pulse width limiting circuit includes: a reference current source configured to generate and output a reference current; a constant current source configured to generate and output a given constant current based on the reference current; a capacitor configured to be charged with the constant current; an inverting block configured to connect the constant current source and a ground and to receive the given constant current from the constant current source, the inverting block comprising: a first switch circuit configured to supply the constant current to the capacitor according to a level of the PWM pulse signal; and a second switch circuit configured to discharge a voltage across the capacitor to the ground when the first switch circuit stops supplying the constant current to the capacitor; a determination circuit configured to determine whether the voltage across the capacitor becomes a given value or greater; and a limiting circuit configured to hold the level of the PWM pulse signal during a period of time from when the PWM pulse signal reaches the level to turn on the switching element to when the voltage across the capacitor reaches and exceeds the given value, and to limit a pulse width of the PWM pulse signal.