DC/DC converter, power supply circuit, and semiconductor device

摘要

Provided is a DC-DC converter with improved power conversion efficiency. A transistor which is incorporated in the DC-DC converter and functions as a switching element for controlling output power includes, in its channel formation region, a semiconductor material having a wide band gap and significantly small off current compared with silicon. The transistor further comprises a back gate electrode, in addition to a general gate electrode, and a back gate control circuit for controlling a potential applied to the back gate electrode in accordance with the output power from the DC-DC converter. The control of the potential applied to the back gate electrode by the back gate control circuit enables the threshold voltage to decrease the on-state resistance when the output power is high and to increase the off-state current when the output power is low.

主权项

1. A semiconductor device comprising:
a DC-DC converter comprising:
a first transistor comprising a gate, a back gate and a channel formation region comprising an oxide semiconductor; anda constant-voltage generation circuit electrically connected to one of a source and a drain of the first transistor; wherein a potential applied to the back gate of the first transistor is controlled according to a magnitude of a power output from the constant-voltage generation circuit.