Patent ID: 7701181
Filing Date: 2010-04-20
Classification: G05F

Abstract:
1. A power supply device that outputs an input voltage input to an input terminal from a predetermined output terminal as an output voltage after converting it into a predetermined voltage, the device comprising: a synchronous rectification switching regulator that outputs the input voltage to the output terminal after converting it into a predetermined voltage; a linear regulator that outputs the input voltage to the output terminal after converting it into a predetermined voltage; and a timing adjustment circuit unit that controls driving of the linear regulator and the synchronous rectification switching regulator in accordance with a control signal input from an outside; wherein the synchronous rectification switching regulator is controlled to be driven by the control signal from the outside and reduces current drive performance of a synchronous rectification transistor that discharges an inductor charged with the input voltage by a switching operation of a switching transistor until a predetermined signal has been input from the timing adjustment circuit unit after being started with the control signal from the outside; wherein the synchronous rectification switching regulator comprises: the switching transistor which is configured to perform the switching operation in accordance with a first input control signal; the inductor charged with the input voltage by the switching operation of the switching transistor; a first synchronous rectification transistor that performs a switching operation in accordance with a second input control signal to discharge the inductor; a second synchronous rectification transistor having current drive performance lower than that of the first synchronous rectification transistor and performing a switching operation in accordance with a third input control signal to discharge the inductor; a control circuit unit that performs switching control with respect to the switching transistor so that the output voltage output from the output terminal becomes the predetermined voltage while causing at least one of the first synchronous rectification transistor and second synchronous rectification transistor to perform a switching operation contrary to the switching transistor; wherein the control circuit unit turns off the first synchronous rectification transistor to cut off an electrical connection while using the second synchronous rectification transistor to discharge the inductor during the signal for reducing the current drive performance of the synchronous rectification transistor being input from the timing adjustment circuit unit.