Patent ID: 8669749
Filing Date: 2014-03-11
Classification: H02M

Abstract:
1. A switching power supply unit of a non-insulated, synchronous rectification type which converts a voltage input to an input terminal into a predetermined voltage and outputs an output voltage, comprising: an inductor; a plurality of output switching elements which perform switching in accordance with an on/off control signal input to a control electrode and charge the inductor with the output voltage; a plurality of rectifying switching elements associated with the output switching elements and discharging the inductor when the associated output switching elements are turned off to stop charging the inductor; a switching element control circuit which generates and outputs a switching control signal which allows the output switching elements to perform switching and the rectifying switching elements to perform reverse switching to the switching of the output switching elements so that the output voltage turns to the predetermined voltage; a switching regulator integrated circuit including a select control terminal to which a select signal is input from an exterior; and a plurality of buffer circuits associated with the output switching elements and the rectifying switching elements, each buffer circuit amongst the plurality of buffer circuits controlling, in response to the select signal, an associated pair of the output switching element and the rectifying switching element to operate in accordance with the switching control signal from the switching element control circuit, wherein the output switching elements, the rectifying switching elements, the switching element control circuit and the buffer circuits are integrated on the switching regulator integrated circuit, wherein a first buffer circuit of the plurality of buffer circuits outputs a first on/off control signal to a first output switching element of the plurality of output switching elements, and a second buffer circuit of the plurality of buffer circuits outputs a second on/off control signal to a second output switching element of the plurality of output switching elements, wherein each of (i) the switching control signal output from the switching element control circuit and (ii) the select signal received through the select control terminal is input into the plurality of buffer circuits to control the first on/off signal and the second on/off signal, wherein the first on/off control signal output by the first buffer circuit to the first output switching element of the plurality of output switching elements is also input to the second buffer circuit, and the second on/off control signal output by the second buffer circuit to the second output switching element of the plurality of output switching elements is also input to the first buffer circuit, to control switching between the first output switching element and one of the rectifying switching elements and to control switching between the second output switching element and another of the plurality of rectifying switching elements, and wherein a size of the first buffer circuit is smaller than a size of the second buffer circuit.