Patent ID: 7129680

Claim:
A DC/DC converter comprising: a voltage converting circuit connected between an input terminal and an output terminal for outputting an output voltage and a switch current detection signal; a fast transient response circuit for receiving the output voltage, control voltage, and switch current detection voltage, and outputting a second control operation determination signal; a step-up and step-down operation determining circuit for receiving the output voltage, the control voltage, and input voltage, and outputting a first control operation determination signal; a voltage comparator for receiving the output voltage, the control voltage, and the second control operation determination signal, and outputting a switch condition signal; and a switch control circuit for receiving the switch condition signal, the first control operation determination signal, and the second control operation determination signal, and outputting a switch control signal, wherein the voltage converting circuit is composed of series connection of: a first switch circuit; an inductor; a second switch circuit; and a smoothing capacitor; wherein the fast transient response circuit comprises: a load judging circuit for receiving the switch current detection signal output from at least one of the first switch circuit and the second switch circuit, and the output voltage output from the smoothing capacitor, detecting an output load region, and outputting a load region detection signal; an output voltage change detecting circuit for comparing the control voltage and the output voltage, detecting the change of the output voltage and outputting an output voltage change detection signal; and a control operation determining circuit for outputting the second control operation determination signal for determining a control mode of the switch control circuit by the load region detection signal and the output voltage change signal to the switch control circuit and the voltage comparator; and wherein the switch control signal is fed into the voltage converting circuit, and a feedback circuit is composed.