Rohm Co., Ltd.

Hidekazu Kojima

Haruo Taguchi

A power supply system for a display panel includes a power supply regulator that regulates a power supply voltage of a display driver of a power supply circuit connected to the display panel, and a protection circuit that protects the display driver against an overvoltage.

Power supply system for a display panel

In a negative step-up charge pump circuit according to the present invention, of a plurality of stages of charge transfer transistors and an output transistor, the former-stage transistors are P channel type field effect transistors, and the later-stage transistors are N channel type field effect transistors. With such configuration, it is possible to avoid start-up failure and current driving performance deterioration resulting from an increase in the number of stages of step-up units without complicating processes and increasing the chip size.

Negative step-up charge pump circuit, LCD driver IC, and liquid crystal display device

A power supply circuit has a charge pump (CHP) step-up circuit including multiple CHP units for stepping up a given power supply voltage to a step-up voltage higher than the power supply voltage, and, based on an output voltage setting signal, converts the step-up voltage to a required output voltage. A comparator compares the detection voltage associated with the output voltage with a reference voltage to generate a comparison signal. In supplying a required output voltage, the number of operable CHP units can be changed to control the step-up voltage based on the comparison signal.

Power supply circuit and portable device

In a drive unit for use with a matrix type display, a buffer circuit of the power supply circuit of the drive unit has an high-voltage first output circuit and a low-voltage second output circuit for generating the same output voltage under a normal operating condition, wherein the high-voltage output circuit has enhanced capability of providing output current to bring up the output voltage and the low-voltage output circuit has enhanced capability of providing output current to bring down the output voltage. A voltage detected at a node connected to the output end of the buffer circuit is compared with a bias voltage. Based on the comparison, the outputs of the first and second output circuits are switched over from one to the other as it is supplied to the display.

Growing community of inventors

Kyoto, Japan

Hidekazu Kojima