Fujitsu Corporation

Fujitsu Semiconductor Limited

Shoji Tajiri

Morihito Hasegawa

Hidekiyo Ozawa

Takashi Matsumoto

Ryuta Nagai

Toshihiko Kasai

A first power supply line and having a first conductivity type a second transistor coupled between the first transistor and a second power supply line, and having the first conductivity type an output unit driving a first control signal causing the first transistor to become conductive, based on a drive voltage, and outputting the first control signal to the first transistor and a boot strap circuit including a capacitor having a first end coupled to a node of the first transistor and the second transistor and supplying the output unit with the drive voltage based on the capacitor, wherein an electric potential of the first end is reduced before the first transistor becomes conductive.

DC-DC converter and control method thereof

The invention provides a DC-DC converter capable of being started up in a state in which an input voltage is low and capable of being structured without increasing a circuit size. A back-gate voltage (Vsb) is outputted from a back-gate voltage generating circuit (VBGN), and is inputted to a back gate of a transistor (FET). During a period during which an output voltage (Vout) is lower than a reference voltage (e), an oscillation signal (OS) is inputted to a gate of the transistor (FET), and the back-gate voltage (Vsb) is set at a grounded voltage. Therefore, the transistor (FET) has a reference threshold voltage (Vto). On the other hand, during a period during which the output voltage (Vout) is higher than the reference voltage (e), a pulse signal (PS) is inputted to the gate of the transistor (FET), and the back-gate voltage (Vsb) is set at an output voltage of a charge pump portion (). Therefore, the transistor (FET) has a threshold voltage higher than the reference threshold voltage (Vto).

Step-up (boost) DC regulator with two-level back-bias switch gate voltage

Growing community of inventors

Aichi, Japan

Shoji Tajiri