Current direction detection circuit and switching regulator having the same

Abstract

A switching regulator includes a first transistor and a second transistor connected in series between an input voltage and a reference voltage, an output terminal arranged to output an output voltage in accordance with a voltage appearing at a first connection point between the first and second transistors, a first control circuit arranged to output a first control signal and a second control signal to alternately turn on and off the first and second transistors, respectively, in accordance with the output voltage at the output terminal, a third transistor connected in parallel with the second transistor between the first connection point and the reference voltage, the third transistor being arranged to be controlled by the second control signal in common with the second transistor, an impedance element located between the third transistor and the reference voltage, and a second control circuit arranged to output a third control signal to turn off the second transistor prevailing over the second control signal in accordance with a voltage appearing at a second connection point between the third transistor and the impedance element.

1 . A switching regulator comprising:
 a first transistor and a second transistor connected in series between an input voltage and a reference voltage;   an output terminal arranged to output an output voltage in accordance with a voltage appearing at a first connection point between the first and second transistors;   a first control circuit arranged to output a first control signal and a second control signal to alternately turn on and off the first and second transistors, respectively, in accordance with the output voltage at the output terminal;   a third transistor connected in parallel with the second transistor between the first connection point and the reference voltage, the third transistor being arranged to be controlled by the second control signal in common with the second transistor;   an impedance element located between the third transistor and the reference voltage; and   a second control circuit arranged to output a third control signal to turn off the second transistor prevailing over the second control signal in accordance with a voltage appearing at a second connection point between the third transistor and the impedance element.   
   
   
       2 . The switching regulator according to  claim 1 , further comprising a detector arranged to detect whether or not a level at the second connection point is lower than the reference voltage. 
   
   
       3 . The switching regulator according to  claim 2 , wherein the second control circuit is arranged to output the third control signal to turn off the second transistor prevailing over the second control signal when the detector cannot detect that the level at the second connection point is lower than the reference voltage. 
   
   
       4 . The switching regulator according to  claim 1 , further comprising a smoothing circuit connected between the first connection point and the output terminal.