Buck converter having improved transient response to load step down

摘要

A synchronous buck converter having an improved transient response during output current includes a first switching transistor connected between an input node and a first node, a second switching transistor connected between the first node and a second node, a series inductor connected between the first node and an output node, an output capacitor connected between the output node and the second node, a first driver circuit operative to turn the first switching transistor one and off according to a variable duty cycle determined by an error signal representing the difference between the voltage output of the converter and a reference voltage, a sensing circuit operative to provide a control signal output when the duty cycle for the first switching transistor is zero, a second drive circuit responsive to the control signal output of the sensing circuit to turn off the second switching transistor and a second sensing circuit operative to provide a second control signal when a dissipating current of the inductor is zero, wherein the second drive circuit is responsive to the second control signal to turn the second switching transistor on when the dissipating current of the inductor is zero.