Switching regulator, control circuit and control method thereof, and electronic apparatus

摘要

A control circuit for controlling a switching transistor and a synchronous rectifying transistor of a switching regulator includes: a bottom detection comparator configured to assert an on signal; an off signal generator configured to assert an off signal; a zero current detector configured to assert a zero current detection signal; and a control logic part configured to receive the on signal, the off signal and the zero current detection signal and generate a control signal such that the control circuit (i) transitions to a first state where, when the on signal is asserted, (ii) transitions to a second state where, when the off signal is asserted, and (iii) transitions to a third state where, when the zero current detection signal is asserted; In the third state, the control logic part reduces an operation current of at least a portion of the control circuit.

主权项

1. A control circuit for controlling a switching transistor and a synchronous rectifying transistor of a switching regulator, comprising:
a bottom detection comparator configured to assert an on signal when a feedback voltage depending on an output voltage of the switching regulator decreases to a predetermined reference voltage; an off signal generator configured to assert an off signal when current flowing into the switching transistor reaches a predetermined peak value; a zero current detector configured to assert a zero current detection signal when current flowing into the synchronous rectifying transistor decreases to a predetermined threshold value after the off signal is asserted; a control logic part configured to receive the on signal, the off signal and the zero current detection signal and generate a control signal such that the control circuit (i) transitions to a first state where, when the on signal is asserted, the control logic part turns on the switching transistor and turns off the synchronous rectifying transistor, (ii) transitions to a second state where, when the off signal is asserted, the control logic part turns off the switching transistor and turns on the synchronous rectifying transistor, and (iii) transitions to a third state where, when the zero current detection signal is asserted, the control logic part turns off the switching transistor and the synchronous rectifying transistor; and a pre-driver configured to switch the switching transistor and the synchronous rectifying transistor based on the control signal from the control logic part, wherein, in the third state, the control logic part reduces an operation current of at least a portion of the control circuit until a next on signal is asserted from lapse of a predetermined standby time after the zero current detection signal is asserted.