DC converter circuit and power supply circuit

摘要

A DC converter circuit having high reliability is provided. The DC converter circuit includes: an inductor configured to generate electromotive force in accordance with a change in flowing current; a transistor including a gate, a source, and a drain, which is configured to control generation of the electromotive force in the inductor by being on or off; a rectifier in a conducting state when the transistor is off; and a control circuit configured to control on and off of the transistor. The transistor includes an oxide semiconductor layer whose hydrogen concentration is less than or equal to 5×1019 atoms/cm3 as a channel formation layer.

主权项

1. A DC converter circuit comprising:
an inductor comprising a first terminal and a second terminal; a transistor electrically connected to the first terminal of the inductor, the transistor comprising:
an oxide semiconductor layer including a channel formation region over a substrate, the oxide semiconductor layer including indium and zinc; anda gate insulating layer adjacent to the oxide semiconductor layer; a rectifier electrically connected to the first terminal of the inductor; and a control circuit electrically connected to the transistor, wherein the control circuit comprises a hysteresis comparator which outputs a pulse signal to a gate of the transistor, wherein a duty ratio of the pulse signal is set in accordance with a voltage of the second terminal of the inductor, and wherein the hysteresis comparator comprises:
a first comparator to which a first reference voltage and the voltage of the second terminal of the inductor is applied;a second comparator to which the voltage of the second terminal of the inductor and a second reference voltage is applied;a first inverter to which a voltage of the first comparator is applied;a second inverter to which a voltage of the second comparator is applied;a first NOR gate to which a voltage of the first inverter is applied; anda second NOR gate to which a voltage of the second inverter is applied,wherein the first NOR gate outputs a voltage to the gate of the transistor, andwherein the second NOR gate outputs a voltage to the first NOR gate.