Patent ID: 8416588

Claim:
A control circuit in constant on-time mode for controlling a DC/DC converter, comprising: a comparing circuit comprising: a comparator comprising: a positive input end for receiving a control voltage; a negative input end for receiving a feedback voltage divided from an output voltage of the DC/DC converter; and an output end for outputting a comparing signal; and a voltage adjusting circuit coupled to the positive input end of the comparator for adjusting the control voltage; wherein the voltage adjusting circuit comprises: a first resistor coupled to the positive input end of the comparator; a first capacitor coupled to the positive input end of the comparator; a first voltage reference source coupled to the first resistor, the first capacitor, and ground; a first switch, comprising: a first end coupled to the positive input end of the comparator; a second end; and a control end coupled to the pulse generator for receiving the pulse signal; and a constant current source coupled to the second end of the first switch; and a pulse generator coupled to the output end of the comparator for generating a pulse signal according to the comparing signal for controlling a switch set of the DC/DC converter; the pulse generator coupled to the control end the first switch for transmitting the pulse signal to the control end of the first switch wherein the first end of the first switch conducts the second end of the first switch for allowing the constant current source to discharge the first resistor and the first capacitor in order to lower when the first switch receives the pulse signal.