Patent ID: 8519687
Filing Date: 2013-08-27
Classification: H01L,H02M,Y02B

Abstract:
1. A power source device comprising: a first transistor and a second transistor constituting a high side transistor and a low side transistor of a DC/DC converter, respectively, and supplying power to an external load; a current detection circuit generating a current detection signal reflecting current flowing through the first transistor; an error amplifier circuit detecting a power source voltage of the external load, and outputting an error amplifier signal which is a result of amplifying the power source voltage of the external load with reference to a first setting voltage; a pulse generation circuit outputting a pulse signal every time the power source voltage of the external load decreases to a predetermined voltage; a reverse-current detection circuit which activates a reverse current detection signal upon detection of current flowing in a direction from the power source voltage of the external load toward the second transistor; a clock generation circuit generating a clock signal of a fixed frequency; a mode setting signal; a selection circuit receiving the pulse signal and the clock signal, outputting the pulse signal when the mode setting signal is in an active state and outputting the clock signal when the mode setting signal is in an inactive state; and a switching control circuit configured to: wherein the reverse-current detection circuit is configured to maintain the reverse current detection signal in an inactive state when the mode setting signal is in an inactive state, and wherein the current detection circuit uses a third transistor, which has a transistor size smaller than that of the first transistor and is current-mirror-connected to the first transistor, to generate the current detection signal.