JP3071125B2 - Split power supply circuit for driving LCD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a divided power supply circuit for driving a liquid crystal for generating a plurality of voltages for driving a liquid crystal, and more particularly to a structure of a divided power supply circuit for driving a liquid crystal used in a simple matrix type liquid crystal display or the like. .

[0002]

2. Description of the Related Art Conventionally, a thin liquid crystal display with low power consumption has been used as a display device of various devices. In this liquid crystal display, liquid crystal is sealed between two substrates, and a predetermined voltage is applied to each of two electrodes formed on the opposing surface of each substrate to drive liquid crystal molecules between the electrodes for each pixel. , Desired display.

For example, in a simple matrix type liquid crystal display, line-sequential scanning of each electrode is performed using a time division driving method. In such a time-division driving method, as shown in FIG.
To V4) and outputs the same to a driver of a liquid crystal display (not shown).

In FIG. 4, a divided power supply circuit includes a buffer amplifier Amp for generating voltages (V1 to V4) in a plurality of stages.
1 to Amp4. A resistor R1 is connected between the high-side circuit power supply VCC and the low-side circuit power supply VEE.
0, a resistor R11, and variable resistors RO, R12, and R13 are connected in series, and desired voltages divided by these resistors are input to input terminals IN1 to IN4 of Amp1 to Amp4, respectively. And each Amp1-4
Depending on the voltage input to each of the input terminals IN1 to IN4, 4
The two divided voltages V1, V2, V3, and V4 are generated. The divided voltages V1 to V4 are V1 and V2 on the high voltage side,
The potential difference between V2 on the high voltage side and V3 on the low voltage side is adjusted by a resistor RO according to the number of horizontal scanning lines of the liquid crystal display.
The multi-stage divided voltage output from the divided power supply circuit allows selection and selection of each pixel of the liquid crystal display.
The liquid crystal drive voltage at the time of non-selection is determined, and display is performed based on this.

In such a divided power supply circuit for driving a liquid crystal, there is a demand that the output current be increased with an increase in the size of the liquid crystal display. To solve this, for example, Japanese Unexamined Patent Publication No. Hei 4-328721 discloses a method. As shown, it has been proposed to connect the output transistors of the buffer amplifier in Darlington connection. That is, in FIG.
Regarding Amp2 to Amp4, a first-stage transistor is provided downstream of the transistor Q15 similar to Amp1, and the base of the output transistor Q10 is connected to the emitter of this transistor. Thus, sufficient current amplification is performed while suppressing the bias current supplied to the output transistor. In this conventional example, the output transistor of Amp1 which generates the highest voltage has a single output in order to prevent a voltage drop of 2VBE with respect to the circuit power supply VCC as shown in FIG.

Further, in the above conventional example, as shown in FIG. 4, the bias current supplied to the current source transistors Q10 of Amp1 and Amp2 for generating the high voltage power is the resistance value of the external variable resistor RBO. Is adjusted so that an appropriate amount of current can be adjusted according to the capability of the divided power supply circuit. More specifically, the base of a transistor Q6 is connected to a reference voltage generator (Vref) that generates a reference voltage in response to the activation of the activation circuit, and the emitter of the transistor Q6 is externally variable via a terminal BO. The resistor RBO is connected.

By adjusting the resistance value of the variable resistor RBO, a current corresponding to the resistance value of the variable resistor RBO flows through the input side transistor Q7 of the constant current circuit provided on the collector side of the transistor Q6. Thereby, the constant current value flowing through the transistor Q15 forming the current mirror circuit with the transistor Q7 is changed. The collector of the transistor Q15 is connected to the base of an output transistor Q10, which is a current source side transistor.
The constant current supplied to 10, ie, the bias current, is changed. Therefore, the current flowing through output transistor Q10 is adjusted to a desired value. The output transistor Q10
The adjustment of the bias current was performed in the same manner for Amp2.

As described above, in the divided power supply circuit used in the conventional drive circuit, the bias current of the current source transistor is adjusted to make the bias current appropriate for the divided power supply circuit, thereby reducing the power consumption of the device. It was measured.

However, with the enlargement of the liquid crystal display and the development of liquid crystal displays of various sizes, it has been required to adjust the output current from the divided power supply output circuit according to the standard of the liquid crystal display.
For this reason, in the conventional split power supply output circuit as shown in FIG. 4, in order to adjust the respective output currents from the respective Amps 1 to 4, an external current adjusting resistor may be connected to the output terminal of each Amp as required. R20 to R23 were connected.

[0010]

SUMMARY OF THE INVENTION However, Amp
If the limiters for adjusting the output currents from 1 to 4 are configured by connecting external resistors to their output terminals, each output of each Amp requires a resistor. Further, in the power supply circuit for driving the liquid crystal, since the output load includes the liquid crystal, that is, the capacitor component, the current instantaneously flows to the full capacity of the divided power supply circuit when switching the output current, and it is difficult to reduce the power consumption of the device. There was a problem.

Further, when the external resistors R20 to R23 are connected to the output terminal as described above, a resistor is added outside the feedback circuit of Amp, and a potential difference is generated between both ends of the resistor, and the resistor is extremely vulnerable to load fluctuation. It becomes a circuit configuration. Therefore, there has been a problem that the output voltage is not stabilized, which adversely affects the display quality of the liquid crystal display.

In order to adjust the output current, a method has been proposed in which a built-in resistor is provided in a current path between an output transistor of Amp and an output terminal. However, in this method, the resistance value is constant. Therefore, there has been a problem that the amount of output current individually required for the liquid crystal display cannot be adjusted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a divided power supply circuit for driving a liquid crystal, which outputs an optimum current according to a liquid crystal display and consumes low power. .

[0014]

In order to achieve the above object, the liquid crystal driving divided power supply circuit of the present invention has the following features.

That is, a divided power supply circuit for driving a liquid crystal for generating a plurality of voltage levels for driving the liquid crystal, comprising a plurality of voltage generating sections for respectively generating the voltage of each step, wherein the plurality of voltage generating sections are provided. The unit has a current source side transistor and a current sink side transistor, respectively, a bias current for driving the current source side transistor ,
A bias voltage for driving the current sink side transistor
It is characterized in that both currents are adjusted by adjusting resistors.

Further, the device has an adjusting resistor terminal, and the adjusting resistor having a predetermined resistance value is connected to the adjusting resistor terminal, so that the current source transistor and the current sink are connected.
And adjusting both of the bias currents for the built-in transistor .

Further, as another configuration of the adjusting resistor, a terminal for selecting a plurality of fixed resistors is provided, and the resistance value of the adjusting resistor is adjusted by one or a combination of the selected terminals. Features.

The voltage generator includes a high-voltage generator for generating a high-voltage and a low-voltage generator for generating a low-voltage. A terminal for connecting to a low-voltage side circuit power supply via a resistor is provided on the downstream side of the current sinking transistor of the section, and a resistor is provided on the upstream side of the current source side transistor of the low voltage side voltage generating section. And a terminal for connecting to a circuit power supply on the high voltage side via the terminal.

Further, among the plurality of voltage generating sections, the current source transistor of the highest voltage side voltage generating section has a single output configuration, and the current source side transistors of the remaining voltage generation sections have a Darlington output configuration. It is characterized by the following.

[0020]

According to the liquid crystal driving split power supply circuit of the present invention,
In each of the voltage generators that generate voltages in a plurality of stages, the bias currents of the respective current source transistors and the respective current sink transistors are all adjusted by adjusting resistors. Therefore, if the bias current is adjusted according to the liquid crystal display to be driven, the output current from each voltage generation unit can be set to an optimum value.

Further, if an adjusting resistor terminal is provided and an external variable resistor is connected to this terminal, various resistance values can be set as required. Further, as another example, if the adjustment resistor is configured by a plurality of fixed resistors and a terminal for selecting the fixed resistor, and the resistance value is changed by one or a combination of the selected terminals,
The resistance value can be adjusted easily and accurately.

Further, according to the present invention, the low voltage side is connected via a resistor to the downstream side of the current sinking transistor of the high voltage side voltage generating section and the upstream side of the current source side transistor of the low voltage side voltage generating section. A terminal for connecting a circuit power supply and a high-voltage circuit power supply is provided. This allows
The potential difference between the emitter and the collector of the transistor on the current sink side or the source side having a large potential difference is reduced, and destruction of this transistor is prevented. Further, by passing a current through these resistors, heat generation in the output transistors of the divided power supply circuit is reduced.

Further, in the present invention, among the plurality of voltage generators, the current source transistor of the highest voltage generator has a single output configuration. Thus, a voltage drop with respect to the circuit power supply voltage can be set as VBE of one transistor. On the other hand, the current flowing transistors of the other voltage generating units have a Darlington output configuration. Therefore,
A large output current can be obtained with a small bias current.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a liquid crystal driving divided power supply circuit according to an embodiment of the present invention will be described below with reference to the drawings. The same parts as those in the drawings already described are denoted by the same reference numerals and description thereof will be omitted. Here, FIG. 1 shows a configuration of a voltage generator on the high voltage side, an adjustment resistor, a starter circuit, and a reference power supply generator, and FIG. 2 shows a configuration of a voltage generator on the low voltage side. FIG. 3 shows the configuration of the amplifier section of each voltage generating section.

[Configuration of Starting Circuit, Reference Voltage Generating Unit, and Adjusting Resistor] In FIG. 1, transistors Q1 and Q2 are
When the circuit power supply (VCC) is started, a current for starting is supplied. After the startup, a first constant current determined by the voltage drop (2VBE) determined by the transistors Q3 and Q4, which normally function as diodes, and the resistance value of the resistor R1 flows through the transistor Q5. And
A constant current corresponding to the first constant current flows through each transistor that is connected to the transistor Q5 in a current mirror connection, and the constant current corresponding to the first constant current flows through each of the voltage generating units 100, which are buffer amplifiers.
The constant current is supplied from the constant current source 22 to the amplifier units 10 to 40 of 200, 300, and 400.

The base of the transistor Q6 has a voltage (2VB) determined by the transistors Q3 and Q4.
E) is applied as the reference voltage Vref. Then, a current determined by the voltage drop (2VBE) of the transistors Q3 and Q4 and the resistance value of the adjusting resistor 50 (the resistors R2, R3 and R4) flows through the transistor Q6, whereby the corresponding current is changed to the second constant current. As the transistor Q
6 and a power supply (VCC). Further, transistors Q14 and Q1 forming a current mirror circuit with the transistor Q7.
5, the second constant current flows.

Here, the adjusting resistor 50 is a resistor for adjusting the second constant current, and has fixed resistors R2 to R4 between the emitter of the transistor Q6 and the low voltage side power supply (VEE).
Are connected in series. Then, the terminal B1 is drawn out from the connection point between the emitter of the transistor Q6 and the resistor R2, the terminal B2 is drawn out from the connection point between the resistors R2 and R3, and the terminal R3 is drawn out from the connection point between the resistors R3 and R4. ing. For example, when the B1 terminal and the B3 terminal are connected, a resistor R4 is provided between the emitter of the transistor Q6 and the power supply (VEE), and the resistance value of the adjusting resistor 50 is the resistor R4.
4 is equal to the resistance value. In addition, any of the terminals B1 to B
3 is also not connected, all the resistors R2, R3, and R4 are connected between the emitter of the transistor Q6 and the power supply (VEE).
This is the sum of the resistance values of R4. Thus, the terminals B1 to B3
Is selectively connected, the resistance value of the adjusting resistor 50 is easily and accurately changed, and the amount of the second current is adjusted. The adjusting resistor 50 is not limited to a fixed resistor, but may be configured by providing a terminal on the emitter side of the transistor Q6 and connecting an external variable resistor.

[Structure of High-Voltage-Side Voltage Generating Units 100 and 200] The amplifier units 10 and 2 of the voltage generating units 100, 200, 300 and 400 each constituted by a buffer amplifier.
0, 30, 40 positive input terminals IN1 to IN4
In the same manner as described above, a multi-step voltage obtained by dividing the voltage between the power supply VCC and the power supply VEE by resistance is applied. Specifically, FIG.
As shown in FIG. 2, resistors R10, R11, RO, R12, and R13 are connected in series between a power supply (VCC) and (VEE) to divide the power supply voltage. In the present embodiment, R10, R11, R12, and R13 of these resistors are configured by fixed resistors, and the resistance value can be changed by the terminal connection method, similarly to the adjusting resistor 50. Further, the resistor RO has a configuration in which terminals are arbitrarily selected from a plurality of fixed resistors and their resistance values are adjusted as described later.
Therefore, the used resistors R10, R11, R12, R13
By setting the RO resistance to a desired value, the output voltages V1 to V4 from the voltage generators 100 to 400 can be made appropriate as required. Note that R10 to R13 and RO constituting the voltage dividing resistor may be constituted by external resistors. However, if the resistance value can be changed by a combination of fixed resistors as in the present embodiment, the resistance value becomes higher. Changes are accurate and easy.

(Structure of Buffer Amplifier 100) A predetermined voltage dropped from the power supply voltage VCC in accordance with the resistance value of the resistor R10 is applied to the input terminal IN1 of the buffer amplifier 100 as the first voltage generator. Is the input terminal IN1
Is supplied to the positive input terminal of the amplifier unit 10 connected to the input terminal. On the other hand, the negative input terminal of the amplifier section 10 is connected to the output terminal V1out of the buffer amplifier which generates the voltage V1 via a resistor, and forms a negative feedback path.

The amplifier section 10 operates according to the voltage applied to the positive input terminal and supplies a predetermined current to the base of the transistor Q16. The collector of the transistor Q16 is connected to an upper power supply (VCC) via a transistor Q14 for supplying a second constant current, and the base of the transistor Q13 is connected to the emitter of the transistor Q16. The emitter of the transistor Q13 is connected to the lower power supply (VE
E), and the collector of the transistor Q13 is connected to a power supply (VCC) via a transistor Q15 for supplying a second constant current and a diode-connected transistor.

When a current is supplied from the transistor Q16 to the base of the transistor Q13 in accordance with the input voltage to the amplifier unit 10 and the current supplied from the transistor Q14, the transistor Q13 operates according to the current, A predetermined current flows through the transistor Q17 and the current mirror Q18 connected thereto. Then, a current corresponding to the second constant current is supplied as a bias current to the base of the output transistor Q12, which is the current sink transistor.

On the other hand, the base of an output transistor Q10, which is a current source transistor, is connected to a transistor Q10.
15 collectors are connected and the output transistor Q
A second constant current is supplied as a bias current to the base 10.

Therefore, by setting the resistance value of the adjusting resistor 50 to a desired value, the output transistor Q1
0 and both the bias current supplied to the output transistor Q12 are adjusted, and the output transistors Q10, Q
The currents flowing through the respective elements 12, that is, the output currents from the buffer amplifier 100 are adjusted to desired values.

When the output transistors Q10 and Q12 operate according to the current flowing through the transistor Q13, a desired voltage V1 is generated at the connection point between the emitter of the output transistor Q10 and the collector of the output transistor Q12. Is supplied to the liquid crystal display from the output terminal V1out.

Further, on the downstream side of the current sinking transistor Q12, that is, in this embodiment, the emitter of the transistor Q12 is connected to the terminal E1, and is connected to the lower power supply (VEE) via a predetermined external resistor RE. It has a connectable configuration.

(Configuration of Buffer Amplifier 200) Next, the configuration of the buffer amplifier 200 which is the second voltage generator will be described. The buffer amplifier 200 is different from the buffer amplifier 100 in that the current source transistor is Darlington connected. That is, the transistor Q2 is connected to the collector of the transistor Q15 through which the bias current determined by the adjusting resistor 50 flows.
2 is connected to this transistor Q22.
Is connected to the base of an output transistor Q20, which is a current source transistor. By thus configuring the output transistor Q20 in a Darlington output configuration, it is possible to increase the current supply capability of the output transistor Q20 with the same bias current as that of the buffer amplifier 100 supplied from the transistor Q15. Note that the (*) marks in the figure indicate that they are connected to each other.

The input terminal I of the buffer amplifier 200
N2 includes a resistor R10 and a resistor R11 from the power supply voltage VCC.
Is input to the positive input terminal of the amplifier section 20, and the voltage V2 is applied to the connection point between the emitter of the transistor Q20 and the collector of the transistor Q12 in accordance with the input voltage. Occurs, and the voltage V2 is output from the output terminal V2out.

Similarly to the buffer amplifier 100, the downstream side (emitter) of the output transistor Q12 is connected to the terminal E.
2 so that the terminal E2 can be connected to the lower power supply VEE via an external resistor RE.

Here, the high voltage side buffer amplifier 100,
For example, if the power supply voltage VCC is 40V, the output voltage V1 from the buffer amplifier 100 is 38V, and the output voltage V2 from the buffer amplifier 200 is as high as 36V. Therefore, the buffer amplifiers 100 and 200
A large potential difference (for example, about 30 V) is generated between the collector and the emitter of the current sink transistor Q12. If the emitter (downstream side) is connected to the lower power supply (VEE) via the resistor RE as described above, a voltage can be generated at both ends of the resistor RE. Therefore, the potential difference generated between the collector and the emitter of the transistor Q12 can be reduced, the damage of the transistor Q12 can be prevented, and the amount of heat generated in the transistor Q12 can be reduced. In a liquid crystal display, its display characteristics have temperature dependence. Therefore, if there is a local heat generation area around the display, there is a possibility that the display quality in the vicinity of the heat generation area is degraded. For this reason, by dispersing the heat generating region to the transistor Q12 and the resistor RE as in the present embodiment, it is possible to prevent the display quality of the liquid crystal display from deteriorating. Note that a resistor having a resistance value corresponding to the difference between the voltages V1 and V2 may be further connected between the terminals E1 and E2 so that the potential at the terminal E1 is higher than the potential at the terminal E2. .

[Configuration of Low-Voltage-Side Voltage Generating Units 300 and 400] Next, the configuration of the low-voltage-side voltage generating units, that is, the buffer amplifiers 300 and 400 will be described with reference to FIG.

The configuration of the buffer amplifiers 300 and 400 is as follows.
This is basically the same as the buffer amplifier 200 of FIG. Between the input terminal IN3 of the buffer amplifier 300 and the input terminal IN2 of the buffer amplifier 200 in FIG. 1, resistance terminals RX1 to RX6 and fixed resistors connected between the terminals RX1 to RX6 are provided. . The input terminal IN2 of the buffer amplifier 200 is connected to the terminal RX1, and the input terminal IN3 of the buffer amplifier 300 is connected to any of the remaining terminals RX2 to RX6. Connect input terminal IN3 to RX2
The voltage applied to the amplifier unit 30 of the buffer amplifier 300 is determined depending on whether any terminal of the RX 6 is connected, and the output terminal V3o of the buffer amplifier 300 is thereby determined.
The configuration is such that the output voltage V3 from ut is determined.
The input terminal IN4 of the buffer amplifier 400 is connected between a resistor R12 connected to the input terminal IN3 of the buffer amplifier 300 and a resistor R13 having one end connected to the lower power supply (VEE). Thus, the input terminal IN4 receives the resistors R10, R11, R11 from the power supply voltage VCC.
O, a voltage lower by a voltage drop corresponding to the resistance value ratio between R12 and R13 is applied, and a voltage V4 corresponding to the input voltage is output from the output terminal V4out of the buffer amplifier 400.

In the buffer amplifiers 300 and 400, the current source side transistor Q30 has a Darlington connection configuration like the buffer amplifier 200. That is, the emitter of the transistor Q22 whose base is connected to the collector of the transistor Q15 that supplies the bias current is connected to the base of the output transistor Q30. Then, the bias current determined by the adjustment resistor 50 in FIG. 1 is supplied to the base of the transistor Q22. On the other hand, the emitter of the output transistor Q32, which is a current sinking transistor, is connected to the lower power supply (VEE), and the base of the output transistor Q32 is connected to the second constant current supplied from the transistor Q14 like the buffer amplifier 100 and the like. A corresponding current is supplied as a bias current. Thus, the output transistors Q30, Q32
The bias current adjusted by the adjusting resistor 50 of FIG.
The output current from 0 is controlled. Note that the mark (*) in FIG. 2 indicates that it is connected to (*) in FIG.

Further, on the upstream side of the output transistor Q30 which is a current source transistor, that is, in this embodiment, the collector of the transistor Q30 is connected to the terminals C1 and C2, respectively.
And connected to the upper power supply VCC via an external resistor RC. In the buffer amplifiers 300 and 400 on the low voltage side, for example, the output voltages V1 and V2 from the buffer amplifiers 100 and 200 on the high voltage side are (38).
V) and (36V), the output voltage V3 is (4
V) and V4 are low voltages such as (2V). Therefore, an extremely large potential difference (for example, about 30 V) occurs between the collector and the emitter of the current source transistor Q30 of each of the buffer amplifiers 300 and 400. Therefore, the upstream side (collector) of the output transistor Q30 is connected to the resistor RC.
To the power supply voltage VCC.
The potential difference between the collector and the emitter of output transistor Q30 can be reduced. Thereby, the possibility of destruction of the output transistor Q30 is reduced, and the amount of heat generated by the transistor Q30 is reduced, so that the display quality of the liquid crystal display can be improved as described above. Note that a resistor having a resistance value corresponding to the difference between the voltages V3 and V4 is further connected between the terminal C1 and the terminal C2, and the terminal C
2 may be configured to be lower than the potential at the terminal C1.

[Configuration of Amplifier Units 10 to 40] Next, FIG.
The amplifier unit 1 of each buffer amplifier 100 to 400 using
The configuration of 0 to 40 will be described.

The input voltages applied to the input terminals IN1 to IN4 are applied to the bases of the transistors Q33 and Q35, which form the positive input terminals of the amplifier units 10, 20, 30, and 40. On the other hand, the bases of the transistors Q34 and Q36 which are the negative input terminals of the amplifier units 10 to 40 are shown in FIGS.
As shown in FIG.
N1 to IN4 to form a negative feedback path.
Then, the transistors Q33, Q35, Q34, Q36
Are supplied with a first constant current from a transistor Q40 constituting the constant current source 22, respectively. Further, transistors Q42 and Q44 forming a current mirror circuit are provided downstream of the transistors Q33 and Q36. The connection point between the transistor Q36 and the transistor Q44 and the connection point between the transistor Q30 and the transistor Q42 are connected to the bases of the transistors Q50 and Q52 receiving the first constant current from the transistors Q46 and Q51 of the constant current source 22, respectively. Is connected. The base of the transistor Q16 is connected to the upstream side of the transistor Q52. An upstream side (collector) of the transistor Q16 is connected to a transistor Q14 forming a current mirror circuit together with the transistor Q7 of FIG. 1, and receives a second constant current from the transistor Q14.

Each of the amplifier sections 10 to 40 has an input terminal IN1.
ＩＮIN4 and the output terminal Vout (V1outＶ
(V4out) and the output voltage (V1 to V4) so as to eliminate the voltage difference, thereby changing the base current of the transistor Q16. Then, the transistor Q
13 is changed and the buffer amplifier 100
The output voltages V1 to V4 from to 400 are adjusted, and the values of the output voltage and the output current are stabilized.

[0047]

In the divided power supply circuit for driving a liquid crystal according to the present invention, the bias currents of the current source transistors and the current sink transistors are all adjusted by the adjusting resistors in each of the voltage generators for generating the voltage in a plurality of stages. I am adjusting. Therefore, if the bias current is adjusted according to the liquid crystal display to be driven, a current having an optimum value can be output from the voltage generator.

Further, by forming the adjusting resistor by an external variable resistor, or by using a plurality of fixed resistors and a terminal for selecting the fixed resistor,
The resistance value can be easily changed, and the bias current can be easily adjusted.

Further, according to the present invention, the low voltage side is connected via a resistor to the downstream side of the current sinking transistor of the high voltage side voltage generating section and the upstream side of the current source side transistor of the low voltage side voltage generating section. Terminals for connecting a circuit power supply and a high-voltage circuit power supply are provided. Thus, the potential difference between the emitter and the collector of the transistor can be reduced, and the transistor can be prevented from being broken.
Further, heat generation in the transistor can be reduced, and the display quality of a liquid crystal display having display characteristics that are temperature-dependent can be improved.

In the present invention, among the plurality of voltage generators, the current source transistor of the highest voltage generator has a single output configuration. Thus, the voltage drop with respect to the circuit power supply voltage can be reduced, and the power supply voltage can be used effectively. On the other hand, by using the Darlington output configuration for the current source transistors of the other voltage generators, a large output current can be obtained with a small bias current, and low power consumption and sufficient current supply capability of the device can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a configuration of a buffer amplifier on a high voltage side according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a configuration of a buffer amplifier on a low voltage side according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of amplifier units 10 to 40 in FIGS. 1 and 2;

FIG. 4 is a diagram showing a circuit configuration of a conventional divided power supply circuit for driving a liquid crystal.

[Explanation of symbols]

10, 20, 30, 40 amplifier section, 22 constant current source,
50 Adjusting resistor, 100, 200, 300, 400
Buffer amplifier.

Claims (5)

(57) [Claims] 1. A divided power supply circuit for driving a liquid crystal, which generates a plurality of voltages for driving a liquid crystal, comprising: a plurality of voltage generators for respectively generating voltages of respective stages; The unit has a current source side transistor and a current sink side transistor, and a bias voltage for driving the current source side transistor.
Current and a bias for driving the current sink transistor.
A divided power supply circuit for driving a liquid crystal , wherein both of the assembling current are adjusted by an adjusting resistor. 2. The liquid crystal driving divided power supply circuit according to claim 1, further comprising an adjusting resistor terminal, wherein the adjusting resistor having a predetermined resistance value is connected to the adjusting resistor terminal. The current source side transistor
Of the bias current for fine current sink side transistor
A divided power supply circuit for driving a liquid crystal, wherein both are adjusted. 3. The divided power supply circuit for driving a liquid crystal according to claim 1, further comprising a terminal for selecting a plurality of fixed resistors, wherein the adjustment is performed by one or a combination of the selected terminals. A divided power supply circuit for driving a liquid crystal, wherein a resistance value of the resistance for the liquid crystal is adjusted. 4. The divided power supply circuit for driving a liquid crystal according to claim 1, wherein the voltage generating section includes a high voltage side voltage generating section that generates a high voltage side voltage, and a low voltage side. A low-voltage side voltage generating unit that generates a voltage on the low-voltage side, and a terminal for connecting to a low-voltage side circuit power supply via a resistor on the downstream side of the current sink side transistor of the high-voltage side voltage generating unit. A terminal for connecting to a circuit power supply on the high voltage side via a resistor is provided on the upstream side of the transistor on the current discharge side of the voltage generating unit on the low voltage side. Split power supply circuit. 5. The divided power supply circuit for driving a liquid crystal according to claim 1, wherein the current source on the highest voltage side of the plurality of voltage generators. A divided power supply circuit for driving a liquid crystal, characterized in that a transistor has a single output configuration, and the remaining current source transistors of the voltage generating section have a Darlington output configuration.