1. Field of the Invention
The present invention relates to a power circuit for a display driver of a display device, particularly to a driving circuit of a liquid-crystal device. More particularly, the present invention relates to a display device for performing to be multiplex driving, still more particularly relates to a power supplying circuit for driving a liquid-crystal device used for a liquid-crystal-driving circuit.
2. Related Background Art
Symbol 106 denotes an LCD driver (LCDDR) for driving an LCD, which receives a voltage from the battery 101 and an output of the regulator 102 and voltages divided by the resistances 103, 104, and 105 as LCD driving voltages.
Symbol 107 denotes a liquid-crystal panel connected to the LCD driver, which is turned on/off by the LCD driver 106.
Symbol 111 denotes an LCD driver (LCDDR) for driving an LCD, which receives power from the battery 101 and a liquid-crystal-driving voltage from the charge pump 110. Symbol 112 denotes a liquid crystal panel connected to the LCD driver, which is turned on/off by the LCD driver 106.
However, since in the case of the voltage divider by using resistance shown in
Moreover, the charge pump type shown in
Furthermore, though some of liquid-crystal drivers respectively having a built-in a charge pump circuit are marketed, most liquid-crystal drivers do not have a charge pump in general. Therefore, because charge-pump ICs for supplying LCD driver voltages are hardly marketed, it is actually difficult to constitute an LCD driver of a small current consumption by using a consumer IC.
To solve the above problems, the present invention makes it possible to provide a display driver of display devices consuming a small current without requiring a complex circuit such as a charge pump circuit by using a series regulator of a very small current consumption constituted by a plurality of CMOS circuits or the like and thereby obtaining the voltages for multiplex driving mode from a voltage supplied from a power source such as a battery.
Moreover, when a voltage is equal to or lower than a power-source voltage, an output voltage of a series regulator is stable and it is possible to accurately raise a low voltage and a high voltage by integral multiples like in the case of a charge pump system even if the number of divided driving voltages increases.
The present invention relates to a power circuit for supplying a plurality of voltages to a driving circuit for multiplex driving mode, that is, a power circuit for a display driver in which the voltages are output via a constant-voltage circuit constituted by a regulator for dividing a voltage supplied from a power source and keeping the plurality of voltages at certain voltage levels.
Moreover, the present invention is characterized by a power circuit in which the above constant-voltage circuit is a step-down regulator.
Furthermore, the present invention is characterized by a power circuit in which the above constant-voltage circuit has means for correcting an output voltage in accordance with a temperature.
Furthermore, the present invention is characterized by a power circuit using one regulator IC in which a plurality of the above constant-voltage circuits are integrated.
Furthermore, the present invention is characterized by a power circuit in which each of the above constant-voltage circuits has at least two input terminals, one input terminal of each constant-voltage circuit is connected to the positive electrode of a power source, and the other input terminal of it is connected to the output of another constant-voltage circuit when connecting the constant-voltage circuits each other.
Furthermore, the present invention is characterized by a power circuit in which each of the constant-voltage circuits has at least two input terminals and includes a first constant-voltage circuit in which the above input terminals are connected to the positive and negative electrodes of the above power source and a second constant-voltage circuit in which the above input terminals are connected to the positive electrode of a power source and the output of the first constant-voltage circuit when connecting the constant-voltage circuits each other.
Furthermore, the present invention is characterized by a camera having a display device provided with a driving circuit using the above power circuit, and a data-copying function for copying the display data to the liquid-crystal device to a film.
The present invention is described below in detail in accordance with the illustrated embodiments.
In this case, the regulators 2, 3, and 4 are regulators having an equal output voltage. Because the VSS of the regulator 3 is connected to the output of the regulator 2, the output voltage of the regulator 3 becomes two times higher than the output voltage of the regulator 2 on the basis of the VSS of the regulator 2. Furthermore, because the VSS of the regulator 4 is connected to the output of the regulator 3, the output voltage of the regulator 4 is set to be three times higher than the output voltage of the regulator 2 on the basis of the VSS of the regulator 2.
Concrete voltage example is as follows. When assuming the voltage of the battery 1 as 5 V and the output voltage of each regulator as 1.5 V, the output voltage of the regulator 2 shows 1.5 V, that of the regulator 3 shows 3.0 V, and that of the regulator 4 shows 4.5 V.
Then, symbol 5 denotes a liquid-crystal display driver (LCDDR) using the battery 1 as the power source of a circuit and the output of the regulator 2, 3, or 4 as the LCD driver voltages, in which the output of the regulator 2 is connected to VL1, that of the regulator 3 is connected to VL2 and that of the regulator 4 is connected to VL3. Symbol 6 denotes a liquid-crystal display device (liquid-crystal display panel) connected to the liquid-crystal display driver 5, which outputs multiplex signals to drive the liquid-crystal display panel 6 by applying common signals COM0, COM1, and COM2 and a segment signal of an SEG21 from an SEG0 through a common electrode and a segment electrode.
(Circuit Diagram of Regulator)
In this case, the regulator is constituted by a CMOS to control an output voltage by controlling the gate voltage of the P-channel MOSFET for controlling a voltage. Thereby, it is unnecessary to use the base current of a voltage control device like in the case of a bipolar transistor and it is possible to decrease the current of a power source. Therefore, it is possible to greatly reduce current consumption.
For each segment signal (SEG) and common signal (COM), voltages VL1, VL2, VL3, and 0 V generated by the regulators 2, 3, and 4 are output in accordance with a display state of a liquid crystal. In this case, the signal shown by “COM0-SEG1 in
(Explanation of Camera Using Liquid-Crystal Display Device)
Symbol 18 (SW1) denotes a switch connected to the microcomputer 11 to start photometry and focus detection and 19 (SW2) denotes a switch connected to the microcomputer 11 to start exposure. Switches SW1 and SW2 are release switches respectively having a two-stage configuration. The switch SW1 is turned on in accordance with the first stroke of a release switch and switches SW1 and SW2 are both turned on in accordance with the second stroke of the release switch.
Symbol 20 denotes an AF (auto-focus)-region selecting switch connected to the microcomputer 11 to optionally select any one of a plurality of AF regions provided for the focus detecting sensor 14, 21 denotes a dial detecting circuit connected to the microcomputer 11 to detect operations of dials for various settings provided for a camera, and 22 denotes a setting dial connected to the dial detecting circuit 21 to perform various settings of a camera. It is possible to select an optional automatic AF region or automatic AF-region selection in which a camera automatically selects an AF region by the AF-region selecting switch 20 and the dial.
Symbol 23 denotes a film loaded in a camera body (not illustrated), 24 denotes a film detecting circuit controlled by the microcomputer 11 to detect the position of the film 23, 25 denotes a photosensor driven by the film detecting circuit 24 to detect the position of the film 23, and 26 denotes a film supplying circuit controlled by the microcomputer 11 to wind or rewind the film 23 by driving a film supplying motor 27. Symbol 28 denotes a shutter control circuit controlled by the microcomputer 11 to control a shutter for exposure, and 29 denotes a shutter controlled by the shutter control circuit 28 to perform exposure.
Then, symbol 30 denotes a liquid-crystal display driver connected to the microcomputer 11 to display various information on an LCD, which corresponds to symbol 5 in
Thus, a plurality of constant voltages are generated from a voltage supplied from a battery serving as a power source by using a plurality of regulators to turn on an LCD via a liquid-crystal display driver by using the certain voltages as LCD driver voltage sources.
Moreover, it is possible to obtain different liquid-crystal-driving voltages by using one type of a regulator and thereby connecting the output of one regulator with VSS of another regulator.
Though the LCD by multiplex driving mode has been described by a ⅓ bias and a ⅓ duty, it is also possible to use the above mode for another bias levels by changing the number of regulators.
Furthermore, it is possible to decrease the current consumption and always display data easily in the case of a unit using a battery as a power source such as a camera by using this LCD power circuit.
Then, symbol 40 denotes a liquid-crystal display driver using the battery 36 as the power source of a circuit and outputs of the regulators 37, 38, and 39 LCD driver voltage sources. The output of the regulator 37 is connected to VL1, that of the regulator 38 is connected to VL2, and that of the regulator 39 is connected to VL3. Symbol 41 denotes a liquid-crystal display device connected to the liquid-crystal display driver 40, in which liquid crystal is driven in accordance with common signals COM0, COM1, and COM2 and segment signals of SEG0 to SEG21.
(Regulator for Outputting a Plurality of Voltages)
In
Then, symbol 44 denotes a liquid-crystal display driver using the battery 42 as the power source of a circuit and a plurality of outputs of the regulator 43 as LCD driver voltage sources, in which a first output of the regulator 43 is connected to VL1, second output of it is connected to VL2, and third output of it is connected to VL3. Symbol 45 denotes a liquid-crystal display device connected to the liquid-crystal display driver 44, in which liquid crystal is driven in accordance with common signals COM0, COM1, and COM2 and segment signals of SEG0 to SEG21.
It is possible to decrease the size of a power-circuit portion by the above configuration.
(Description of One-Chip Configuration)
In
Symbol 48 denotes a regulator built in the integrated circuit 47 to keep a voltage supplied from a power source constant, which outputs a voltage of 1.5 V in this case. Symbol 49 denotes a regulator whose integrated-circuit input is connected to a power source and whose VSS is connected to the output of the regulator 48 to keep a voltage constant, which outputs 3.0 V two times higher than the output voltage of the regulator 48. Symbol 50 denotes a regulator whose input is connected to a power source and whose VSS is connected to the output of the regulator 49 to keep a voltage constant, which outputs 4.5 V three times higher than the output voltage of the regulator 48. In this case, specific output voltages are set to 1.5 V, 3.0 V, and 4.5 V. However, it is possible to drive LCDs having driving voltages different from each other by changing a voltage in accordance with the driving voltage of an LCD. Symbol 51 denotes a liquid-crystal display driver built in the integrated circuit 47 to use outputs of the regulators 48, 49, and 50 as LCD driver voltage sources, in which the output of the regulator 48 is connected to VL1, that of the regulator 49 is connected to VL2, and that of the regulator 50 is connected to VL3. Symbol 41 denotes a liquid-crystal display device connected to the liquid-crystal display driver 40, in which liquid crystal is driven in accordance with common signals COM0, COM1, and COM2 and segment signals of SEG0 to SEG21.
Thus, a plurality of constant voltages are generated from a voltage supplied from a battery serving as a power source by using a plurality of regulators so as to turn on an LCD via a liquid-crystal display driver by using the certain voltages as LCD driver voltage sources.
Moreover, a plurality of constant voltages are generated from a voltage supplied from a battery serving as a power source by using a regulator having a plurality of output terminals so as to turn on an LCD via a liquid-crystal display driver by using the constant voltages as LCD driver voltage sources.
Furthermore, as shown in
Therefore, as shown in
Moreover, a configuration using a CMOS circuit of a small current consumption is generally used as the structure of a regulator used for the present invention. However, when a current consumption is small, it is allowed to use another type such as a bipolar type as long as it consumes a small current.
As described above, a method is provided which obtains a power source for multiplex driving a display device such as a liquid-crystal display device from a voltage supplied from a power source such as a battery by using a regulator consuming a very small current constituted by a plurality of CMOS circuits. Thereby, it is possible to provide an LCD driver of a small current consumption without using a complex circuit such as a charge pump circuit.
Moreover, because of a simple configuration using only a series regulator and a general-purpose liquid-crystal display driver, it is possible to always display data on a liquid-crystal display portion by a simple circuit configuration without considering the service life of a battery also in the case of a unit using a battery as a power source such as a camera. Though the present invention is described on a liquid-crystal display device, it is also effective for another display device according to a different display principle such as an organic electroluminescence device or an electrophoresis display device.
Number | Date | Country | Kind |
---|---|---|---|
2002-029390 | Feb 2002 | JP | national |
Number | Date | Country | |
---|---|---|---|
Parent | 10354075 | Jan 2003 | US |
Child | 11156729 | Jun 2005 | US |