| 摘要 |
PURPOSE: A DC-DC converter is provided to maintain high efficiency in a wide load region, and simultaneously to prevent the reduction of responsiveness of an output voltage signal even under low-load conditions by improving a structure of the DC-DC converter. CONSTITUTION: A DC-DC converter is so constituted that it is switchable to either PWM control as a first feedback control method or PFM control as a second feedback control method. The PFM control is selected in a region in which a load current flowing to the load(LOAD) becomes smaller by exceeding a prescribed value. And at the same time, the PWM control is selected regardless of the magnitude of the load current when a voltage level supplied to the load(LOAD) is changed. The DC-DC converter requires switching signals PWM/PFM since the PWM control and the PFM control have different circuit operations. Accordingly, an operation mode of an oscillation circuit and inputs of multiplexer circuits(Mux1,Mux2) are switched by using the switching signals PWM/PFM generated at a PWM/PFM determining circuit(10).
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