Matsushita Electric Industrial Co., Ltd.

Tsukasa Kawahara

Kazuhiko Nagaoka

Yoshito Date

Tomokazu Kojima

Yasuyuki Doi

Tetsuro Ohmori

Takahito Kushima

Tooru Suyama

Tsutomu Sakakibara

Miki Fujino

Masahiro Akabori

Kenji Miyake

Shinji Miyamoto

Yoshiyuki Konishi

Satoshi Wada

A compact-size driving voltage controller is provided which can be driven with low power. The compact-size driving voltage controller which can be driven with low power includes a High output operational amplifier and a Low output operational amplifier for supplying driving voltages VcomH, VcomL to a load such as a liquid crystal display panel, an output switch for alternating between the outputs of the operational amplifiers, a Low voltage setting operational amplifier for generating a set voltage to be supplied to the non-inverted input terminal of the Low output operational amplifier, a set voltage generator including a current mirror circuit and a clamping circuit, a bias current controller for controlling the bias current flowing in each operational amplifier with a predetermined timing, and a timing controller for controlling the changeover timing of the output switch.

Driving voltage controller

An inductoraccumulates an energy therein or releases the accumulated energy according to the state of a main switch elementbeing turned ON/OFF. When the inductorreleases an energy, if a sub-switch elementis in the ON state, a current is passed through a circuit downstream of the sub-switch element, thereby increasing an output voltage VO. The sub-switch elementis a P-channel MOS transistor, and a sub-switch control circuitoutputs a control signal VCTfor the sub-switch element. A level shift circuitreceives an output-side potential VP of the inductor, and outputs, as a control signal VGapplied to the gate of the sub-switch element, the potential VP if the control signal VCTis at the L level or a potential (VP&#x2212;VM) lower than the potential VP if the control signal VCTis at the H level. Thus, the output voltage of the DC-DC converter can be made precisely equal to the target voltage.

DC-DC converter

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Nagaokakyo, Japan

Tsukasa Kawahara