Patent ID: 7279869

Claim:
A pulse frequency modulation control circuit for controlling a switching regulator having a switching circuit and an inductive device to convert an input voltage to an output voltage, the pulse frequency modulation control circuit comprising: a current sensing circuit for generating a current detection signal representative of a current flowing through the inductive device; a voltage sensing circuit for generating a voltage detection signal representative of the output voltage; and a pulse generating circuit for generating a pulse control signal in response to the current detection signal and the voltage detection signal, the pulse control signal having a plurality of switch cycles, each of which consists of an ON-time applied to turn on the switching circuit and an OFF-time applied to turn off the switching circuit, wherein: the ON-time is adjusted in accordance with the current detection signal such that the ON-time is prolonged in response to an increase of a maximum of the current detection signal, and the OFF-time is adjusted in accordance with the voltage detection signal such that the OFF-time is prolonged in response to a reduction of a falling rate of the voltage detection signal wherein: the pulse generating circuit comprises: a reference ON-time setting circuit for preventing the ON-time from being shorter than a predetermined reference ON-time, and an ON-time adjusting circuit for dynamically adjusting the ON-time in accordance with the current detection signal, wherein: the reference ON-time setting circuit comprises: a current source; a capacitor connected between the current source and a ground potential; a switch controlled by the pulse control signal such that the switch is turned off during the ON-time for allowing the current source to charge the capacitor, and the switch is turned on during the OFF-time for allowing the capacitor to be discharged to the ground potential; and a comparator for comparing a potential difference across the capacitor and a predetermined reference voltage.