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

Abstract

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one embodiment of a cellular phone terminal according to the present invention;

FIG. 2 is a timing chart showing an example of scanning signals and data signals;

FIG. 3 is a circuit block diagram showing one example of configuration of a power supply circuit 31; and

FIG. 4 is a circuit diagram showing one example of configuration of a buffer BUF 2.

Claims

1. A negative step-up charge pump circuit comprising: a plurality of stages of step-up units formed of charge transfer transistors and charge transfer capacitors,wherein the negative step-up unit charge pump circuit negatively steps up an input voltage by using the plurality of stages of step-up units to thereby produce a desired output voltage, andwherein, of the charge transfer transistors, the former-stage transistors are P channel type field effect transistors and the later-stage transistors are N channel type field effect transistors.

2. An LCD driver IC comprising: a negative step-up charge pump circuit which produces a drive voltage of a negative polarity for a liquid crystal display panel,wherein the negative step-up charge pump circuit has: a plurality of stages of step-up units formed of charge transfer transistors and charge transfer capacitors,wherein the negative step-up unit charge pump circuit negatively steps up an input voltage by using the plurality of stages of step-up units to thereby produce a desired output voltage, andwherein, of the charge transfer transistors, the former-stage transistors are P channel type field effect transistors and the later-stage transistors are N channel type field effect transistors.

3. A liquid crystal display device having: a liquid crystal display panel; andan LCD driver IC which drives and controls the liquid crystal display panel,wherein the LCD driver IC has: a negative step-up charge pump circuit which produces a drive voltage of a negative polarity for the liquid crystal display panel,wherein the negative step-up charge pump circuit has a plurality of stages of step-up units formed of charge transfer transistors and charge transfer capacitors,wherein the negative step-up unit charge pump circuit negatively steps up an input voltage by using the plurality of stages of step-up units to thereby produce a desired output voltage, andwherein, of the charge transfer transistors, the former-stage transistors are P channel type field effect transistors and the later-stage transistors are N channel type field effect transistors.

4. A negative step-up charge pump circuit comprising: first to m (equal to or lager than 2)-th charge transfer transistors; serially connected to a ground;an output transistor serially connected between the m-th charge transfer transistor and an output voltage output terminal;first to m-th charge transfer capacitors having one end connected to a connection node between the transistors; andan output capacitor having one end connected to the output voltage output terminal and another terminal grounded;a gate signal production section which, in synchronization with a predetermined clock signal, produces a gate signal which is a pulse that changes its level between a supply voltage and an output voltage, and an inverted gate signal which is a logical inversion of the gate signal, and supplies the gate signal and the inverted gate signal to the first to m-th charge transfer transistors and the output transistor so that those adjacent to each other are in mutually different open/close states; anda terminal voltage production section which, in synchronization with the clock signal, produces a terminal voltage which is a pulse that changes its level between a supply voltage and a ground voltage, and an inverted terminal voltage which is a logical inversion of the terminal voltage, and supplies the terminal voltage and the inverted terminal voltage to another ends of the first to m-th charge transfer capacitors so that those adjacent to each other are at mutually different voltage levels,wherein the negative step-up charge pump circuit negatively steps up the input voltage to thereby produce a desired output voltage, andwherein the first to (m−1)-th charge transfer transistors are P channel type field effect transistors and the m-th charge transfer transistor and the output transistor are N channel type field effect transistors.

5. An LCD driver IC comprising: a negative step-up charge pump circuit which produces a drive voltage of a negative polarity for a liquid crystal display panel,wherein the negative step-up charge pump circuit has:first to m(equal to or larger than 2)-th charge transfer transistors serially connected to a ground;an output transistor serially connected between the m-th charge transfer transistor and an output voltage output terminal;first to m-th charge transfer capacitors having one end connected to a connection node between the transistors;an output capacitor having one end connected to the output voltage output terminal and another end grounded;a gate signal production section which, in synchronization with a predetermined clock signal, produces a gate signal which is a pulse that change its level between a supply voltage and an output voltage, and an inverted gate signal which is a logical inversion of the gate signal, and supplies the gate signal and the inverted gate signal to the first to m-th charge transfer transistors and the output transistor so that those adjacent to each other are in mutually different open/close states; anda terminal voltage production section which, in synchronization with the clock signal, produces a terminal voltage which is a pulse that changes its level between a supply voltage and a ground voltage, and an inverted terminal voltage which is a logical inversion of the terminal voltage, and supplies the terminal voltage and the inverted gate terminal voltage to another ends of the first to m-th charge transfer capacitors so that those adjacent to each other are at mutually different voltage levels,wherein the negative step-up charge pump circuit negatively steps up the input voltage to thereby produce a desired output voltage, andwherein the first to (m−1)-th charge transfer transistors are P channel type field effect transistors and the m-th charge transfer transistor and the output transistor are N channel type field effect transistors.

6. A liquid crystal display device comprising: a liquid crystal display panel;an LCD driver IC which drives and controls the liquid crystal display panel;wherein the LCD driver IC has:a negative step-up charge pump circuit which produces a drive voltage of a negative polarity for the liquid crystal display panel,wherein the negative step-up charge pump circuit has:first to m(equal to or larger than 2)-th charge transfer transistors serially connected to a ground;an output transistor serially connected between the m-th charge transfer transistor and an output voltage output terminal;first to m-th charge transfer capacitors having one end connected to a connection node between the transistors;an output capacitor having one end connected to the output voltage output terminal and another end grounded;a gate signal production section which, in synchronization with a predetermined clock signal, produces a gate signal which is a pulse that change its level between a supply voltage and an output voltage, and an inverted gate signal which is a logical inversion of the gate signal, and supplies the gate signal and the inverted gate signal to the first to m-th charge transfer transistors and the output transistor so that those adjacent to each other are in mutually different open/close states; anda terminal voltage production section which, in synchronization with the clock signal, produces a terminal voltage which is a pulse that changes its level between a supply voltage and a ground voltage, and an inverted terminal voltage which is a logical inversion of the terminal voltage, and supplies the terminal voltage and the inverted gate terminal voltage to another ends of the first to m-th charge transfer capacitors so that those adjacent to each other are at mutually different voltage levels,wherein the negative step-up charge pump circuit negatively steps up the input voltage to thereby produce a desired output voltage, andwherein the first to (m−1)-th charge transfer transistors are P channel type field effect transistors and the m-th charge transfer transistor and the output transistor are N channel type field effect transistors.