Patent ID: 8692486

Claim:
A control circuit of a DC/DC converter, comprising: a current detection circuit configured to compare a current detection signal indicative of a current flowing through a switching transistor of the DC/DC converter with a predetermined threshold to generate an OFF signal that is asserted when the current flowing through the switching transistor reaches a predetermined peak current; a timer circuit configured to generate an ON signal that is asserted after a predetermined time period has elapsed since an assertion of the OFF signal; a pulse generation circuit configured to generate a pulse signal that transitions to a first-level when the ON signal is asserted, and transitions to a second-level when the OFF signal is asserted; and a driver configured to drive the switching transistor based on the pulse signal, wherein the timer circuit includes: a first capacitor, one electrode of the first capacitor having a fixed potential; a current source configured to generate a charging current based on an output voltage V OUT of the DC/DC converter so as to charge the first capacitor with the charging current; an arithmetic circuit configured to generate a threshold voltage V C4 according to an equation of: V C4 =(V IN −V OUT )×V OUT /V IN ×m wherein V IN is an input voltage of the DC/DC converter, V OUT is an output voltage of the DC/DC converter, and m is a constant; and a first comparator configured to compare a voltage of the first capacitor and the threshold voltage V C4 so as to generate the ON signal that is asserted when the voltage of the first capacitor reaches the threshold voltage V C4 .