JP2002108306A - Liquid crystal driving power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal driving power circuit which reduces current consumption and improves display quality. SOLUTION: This liquid crystal driving power circuit is equipped with an output part for multiple predetermined reference voltages, a push-pull amplifier 14 which inputs a reference voltages and outputs a level voltage for driving a liquid crystal display element, and a switch SW which selects the reference voltage inputted to one amplifier of the push-pull amplifier 14 out of the multiple reference voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal drive power supply circuit for reducing current consumption and improving display quality.

[0002]

2. Description of the Related Art FIG. 9 shows an overall configuration diagram of a liquid crystal driving device. As shown in FIG. 9, the liquid crystal driving device corresponds to the liquid crystal panel 1 of mxn dot display, and COM electrodes 2a, 2b... 2n which are also scanning electrodes and SEG which is a data electrode.
Each of the electrodes 3a, 3b... 3m has n and m electrodes. The COM electrodes 2a, 2b ... 2n and the SEG electrodes 3a, 3
3m form parallel linear transparent electrodes, respectively, and are arranged so as to be perpendicular to each other.

The COM electrodes 2a, 2b... 2n and SEG
A liquid crystal is put between the electrodes 3a, 3b... 3m, and a voltage is applied to each of the COM electrodes 2a, 2b... 2n and the SEG electrodes 3a, 3b. , The orientation of the liquid crystal is changed to control the display ON-OFF.

Therefore, equivalently, the COM electrodes 2a, 2
2n and the pixels at the intersections of the SEG electrodes 3a, 3b... 3m have a capacity, and it can be considered that the capacity is charged and discharged. A COM driver 4 for driving the COM electrodes 2a, 2b... 2n and SEG electrodes 3a, 3b.
The EG driver 5 is mainly an analog switch, and outputs one level voltage (including GND) from the level voltage supplied from the liquid crystal drive power supply circuit.

FIG. 10 shows an example of actual driving waveforms of the COM electrodes 2a, 2b... 2n and the SEG electrodes 3a, 3b.

[0006] As shown in FIG.
The M electrodes 2a, 2b,.
The selection level voltage is sequentially output (scanned) to the electrode 2n, and the non-selection level voltage is output to all the electrodes other than the selection electrode.

On the other hand, the SEG electrodes 3a, 3b.
When the OM electrodes 2a, 2b... 2n are scanned, the COM electrodes 2a,
When a pixel at a point intersecting 2b... 2n is displayed, the selected level voltage is output, and when not displayed, a non-selected level voltage is output. The selection level voltage and the non-selection level voltage are based on the COM electrodes 2a, 2b.
The electrodes 3a, 3b,..., 3m are all set so that the liquid crystal display is performed when selected.

Further, in order to prevent the deterioration of the liquid crystal, the selection level voltage and the non-selection level voltage are changed so that the polarity of the applied voltage changes at regular intervals called a frame so that the applied voltage is changed to AC even in the same display state. I have.

As the selection level voltage for driving the liquid crystal, the highest and lowest level voltages for driving the liquid crystal are commonly used, and six level voltages obtained by changing the non-selection level voltage are generally used. The liquid crystal drive power supply circuit 6 (see FIG. 9) generates this level voltage.

FIG. 11 shows a configuration diagram of a conventional liquid crystal drive power supply circuit.

As shown in FIG. 11, a reference voltage obtained by dividing the highest liquid crystal drive voltage VLCD and the lowest voltage GND by a resistor is buffered by an amplifier, and level voltages V1 to V5 are output.

[0012]

However, the conventional liquid crystal drive power supply circuit has the following problems.

In the conventional liquid crystal drive power supply circuit, when the reference voltage divided by the resistor is used directly for driving the liquid crystal, the driving waveform of the liquid crystal panel 1 which is a capacitive load depends on the CR time constant. It is necessary to make the impedance low, but in this case, the resistance R
1. A large idling current flows through R2, which is not suitable for low power consumption.

Therefore, a liquid crystal driving IC for low power consumption used in a liquid crystal panel for portable electronic equipment in recent years is shown in FIG.
As shown in (1), it is composed of a high resistance division and an amplifier 8. This amplifier 8 is generally used for low power consumption,
Two types of amplifiers are used according to the driving capability, and have a configuration generally called a single end.

Conventionally, the amplifier 8 has been selectively used in accordance with the required current driving capability of each level. In recent years, however, as the driving circuit has been further reduced, the bias current of the single-ended amplifier used in the amplifier 8 has been reduced. Various problems due to the current circuit method have surfaced due to a tendency to increase the capacity load due to reduction and an increase in the panel size, and a request to stabilize the amplifier output due to a demand for improving display quality.

For example, considering the non-selection level voltage of the COM electrodes 2a, 2b... 2n, V2 and V5 are output for each frame except when selected, so that an amplifier that outputs V2 has a charging capability. good. However, the liquid crystal is a capacitive load, and the SEG electrodes 3a, 3b... 3m output voltages according to the display state.
3m output the non-selection level voltage V3 and all the SEG electrodes 3a, 3b... 3m output the selection level voltage V1 during the scanning of the next line, that is, when the level voltage at one end of the capacitor rises, COM The electrodes 2a, 2b... 2n output the non-selection level voltage V2, and the amplifier 8 needs to be discharged. For this reason, conventionally, it has been coped with by temporarily suppressing the fluctuation of the level voltage or by increasing the bias current of the amplifier 8 outputting the level voltage V2.

In this case, since it is difficult to cope with a reduction in power consumption and an increase in panel load, there is also a method of switching between two amplifiers having different driving capabilities as necessary as shown in FIG. 12 (JP-A-9-292596). reference). However, in this method, it is necessary to grasp at which timing or which display pattern the level fluctuates, which makes it difficult to switch the amplifier, and furthermore, the through current easily flows because the amplifier output is simply short-circuited. May occur. The through current can be solved by providing an offset between the two amplifiers. In this case, if the offset voltage is large, the output level may fluctuate in an AC manner between the offset voltages, which affects the display. There are cases.

The present invention has been made in view of the above, and has been made in view of the above. A liquid crystal which realizes two items having a trade-off relation of a reduction in current consumption and an improvement in display quality by using a few switches and their control signals. It is an object to provide a driving power supply circuit.

[0019]

According to the present invention, there is provided a liquid crystal driving power supply circuit comprising: a plurality of predetermined reference voltage output units; and a push-pull amplifier which receives the reference voltages and outputs a level voltage for driving a liquid crystal display element. And a switch for selecting a reference voltage to be input to one of the push-pull amplifiers from the plurality of reference voltages.

Further, the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element.

Further, the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element. The reference voltage is selected and input.

Further, the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging, and the charge amplifier and the discharge amplifier are single-ended amplifiers.

Also, the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging, and the reference voltage input to the amplifier capable of discharging is based on the input voltage. It has a voltage to offset the reference voltage.

Further, the offset voltage is controlled according to display switching.

Further, the liquid crystal drive power supply circuit of the present invention comprises an output section for a predetermined reference voltage, and a push-pull amplifier for receiving the reference voltage and outputting a level voltage for driving a liquid crystal display element. One of the amplifiers constituting the pull amplifier is controlled to be discharged.

[0026]

Embodiments of the present invention will be described below.

FIG. 1 is a configuration diagram of a liquid crystal drive power supply circuit according to an embodiment of the present invention.

This liquid crystal drive power supply circuit has predetermined output level voltages V1 to V5 (level voltages similar to those in FIG. 11).
Among them, FIG. 2 shows an example of a driving circuit in which level voltages V1, V2, and V4 are used, and FIG. 2 corresponds to a circuit that outputs level voltages V3 and V5.

Here, the level voltages V1, V2, and V4 are mainly driven by charge driving, and the level voltage rises during discharge when the frame is switched, when one terminal of the panel capacitance changes according to the display state, or when noise is mixed. This is the driving capability necessary under special conditions such as when on the other hand,
Conversely, the level voltages V3 and V5 are mainly discharged, and the charging capability is required as an auxiliary capability.

FIGS. 1 and 2 have the same basic concept, so that FIG. 1 (level voltages V1, V2, V4
Will be described.

The charge amplifier 12 and the discharge amplifier 13 which are output amplifiers of the level voltages V1, V2 and V4
Means that the liquid crystal panel 11 is driven via the output driver 17. Further, the output switch SWD is controlled by the control circuit 16.
Output driver 17 having switches and switches SW1 and SW2
Is controlled.

ON / OFF of each dot of the liquid crystal panel 11
A charge capability is required at the time of display driving, and a discharge capability may be required at the time of frame switching or when the level of one end of the capacitive load rises due to a change due to display or an influence of noise or the like.

Output unit 15 for outputting a predetermined reference voltage
Is, for example, the highest reference voltage VL at the resistors RA and RB.
When outputting 4/5 VLCD of CD, RA = 4R,
By setting RB = R, a specific reference voltage is generated, and this reference voltage is input to the charge amplifier 12 which is a single-ended amplifier having a charge capability to generate a low impedance level voltage. The charge amplifier 12 and the discharge amplifier 13 constitute a push-pull amplifier 14.

VA of voltage input to charge amplifier 12
The higher voltage VOFF1 or VOFF2 is the input voltage of the discharge amplifier 13 having the opposite capability to the charge amplifier 12 via the switch SW1 or SW2, that is, the discharge amplifier 13 having the discharge capability. The output of the discharge amplifier 13 is the same as the output of the charge amplifier 12.

FIG. 3 shows a single-ended amplifier 12a, 1
Fig. 3b shows a configuration diagram of 3a.

The single-ended amplifiers 12a and 13a
Are used for the charge amplifier 12 and the discharge amplifier 13 shown in FIG.

The single-ended amplifier 1 shown in FIG.
In 2a, since a constant bias current flows on the Nch side of the output stage and the Pch side is driven by receiving the output of the differential stage, the charging capability is sufficient, but the discharging capability is limited by the bias current and is small. ing. For this reason, unnecessary through current does not flow in the output stage, and the amplifier can be used as a low power consumption amplifier.

On the other hand, the single-ended amplifier 13a shown in FIG.
Conversely, it is a type that does not have the ability to charge but has the ability to discharge.

FIG. 4 shows the current characteristics of a push-pull amplifier 14 composed of two charge amplifiers 12 and discharge amplifiers 13 having different capacities.

The reason for the current characteristic will be described below. However, here, for simplicity of description, the offset voltages VoffN and VoffP of the amplifier itself are small compared to other input levels, and are ignored.

The output voltage (= VIN-) is changed to the input voltage (= V
IN +) or less, input voltage (= non-inverting input terminal) for both charge amplifier 12 and discharge amplifier 13>
Since this is an output terminal (= inverted input terminal), the charge current capability is increased so as to increase the output. However, since the output section of the discharge amplifier 13 is limited by a constant bias current as shown in FIG. 3B, the output section has the characteristics indicated by broken lines in FIG.

Therefore, the overall characteristics of the amplifier are mainly those of the charge amplifier 12. Next, when the output voltage rises by Voff or more from the input voltage, both the charge amplifier 12 and the discharge amplifier 13 have the input voltage (= non-inverted input terminal) <the output terminal (= inverted input terminal). Attempts to discharge the load charge so as to lower it. However, the output section of the charge amplifier 12 is shown in FIG.
As shown in (a), since there is no discharge capability, the characteristics of the discharge amplifier 13 are dominant.
Finally, when the output voltage is between VA and VA + Voff, the charge amplifier 1
2 does not try to charge, the discharge amplifier 13
Since no discharge is attempted, a bias current flows in the output stage of each amplifier, and the characteristics shown in FIG. 4 are obtained.

At this time, if the offset voltage Voff is reduced, the area charged by the charge amplifier 12 and the discharge amplifier 1 are affected by the offset voltage of the charge amplifier 12 and the discharge amplifier 13.
There is a possibility that the above-mentioned relationship in which the regions where the discharges 3 do not overlap is not satisfied and a through current flows,
In addition, interference or tension between the two amplifiers is likely to occur at the time of driving the load, which may cause unnecessary charge / discharge or waveform distortion.

Conversely, if the offset voltage Voff is increased, the above-mentioned through current is unlikely to occur even if the offset voltage of each amplifier varies, but between VA to VA + Voff, it is possible to drive only the bias current of the two amplifiers. Therefore, the output tends to fluctuate between the voltages due to the influence of a load or noise, and unevenness may occur depending on the display state due to an extra fluctuating voltage applied to the liquid crystal.

Therefore, the liquid crystal drive power supply circuit of the present invention switches the offset voltage in the push-pull amplifier 14 at the time of output switching, thereby minimizing the above-mentioned drawbacks caused by the offset voltage and maximizing the advantages. It is possible.

Next, the operation of the liquid crystal drive power supply circuit of the above embodiment will be described.

In the above embodiment, the push-pull amplifier 14
Can be divided into two types of operation methods according to the operation speed of the single-ended amplifier.

1. When a low-speed amplifier is used (Fig. 1, Fig. 5
reference).

The terms “low speed” and “high speed” refer to the influence time on the liquid crystal display. The time during which the liquid crystal load is driven is the ON time of the output switch SWD of the output driver 17, and an amplifier that operates relatively slowly with respect to the ON time of the output switch SWD, for example, the settling time is the ON time of the output switch SWD. If the time is several tens% or more, it will be referred to as a low-speed amplifier here. As a specific value, the liquid crystal driving time for one line is several hundred μm.
Since this is the case, a single-ended amplifier having a settling time of several tens of μsec or more is used.

When a low-speed single-ended amplifier is used, useless ringing may occupy a large portion of the liquid crystal drive time when a push-pull configuration is used, and this may have a significant effect on display.

FIG. 5 shows a difference in driving waveform depending on the offset voltage.

As shown in FIG. 5, the output control signal is a timing waveform when the output is switched (ON). At this moment, the load of the panel capacitance is connected to the output terminal of the amplifier to drive the liquid crystal panel 11. I do.

When the offset of the discharge amplifier 13 is relatively large (output waveform), specifically, it is several% or more of the driving voltage.
When the output is more than several hundred mV, the output is connected to the amplifier at the timing of the output control signal, and the load starts to be charged. However, since the speed of the amplifier is low, the output is output when the load is charged (or when noise is input). When the voltage to be output largely overshoots, the discharge amplifier 13 operates up to the offset voltage of the discharge amplifier 13 and returns relatively quickly (S1 region). However, VA and VB (= VA + VOF)
During the period F), as described above, since driving is performed with a constant bias current, it takes time to return to VA, and a useless voltage is applied to the liquid crystal, adversely affecting display.

On the other hand, when the offset voltage between the two amplifiers is small (output waveform), when it is less than 1% of the liquid crystal driving voltage, that is, when it is about several tens of mV, the level at which the charge amplifier 12 and the discharge amplifier 13 start operating. Since the thresholds VA and VB are small and the outputs of the amplifiers with low operating speeds are driven independently, they interfere with each other until there is no mismatch between the discharge and charge of each amplifier (overshoot, undershoot). Sn and Mn are the discharge amplifier 13 and the charge amplifier 1 respectively.
2 represents an operating area. The ringing of the time before the settling is not only wasteful charging / discharging of the load, but also large for the display depending on the AC characteristics of the liquid crystal if it occupies a large time in the ON time of the switch SW. Affect.

Finally, when the offset voltage according to the method of the present invention is changed according to the output switching timing (output waveform), the offset voltage is changed at the timing of the offset switching control signal. This timing corresponds to the timing when the switch SW is turned on (the timing when the load is connected to the amplifier).
Temporarily reduce the offset voltage input to the
V to about 50 mV). After switching the switch SW, the offset voltage is increased after a certain time (τ) (about 50 mV
~ Several hundred mV). Since the offset switching signal of the offset switching control signal may be switched before the switch SW of the load is switched, and may be restored when the output of the amplifier almost reaches the target output, τ is
Set to about the rise (fall) time of the amplifier with respect to the panel load.

When the offset voltage at the time of switching is small,
Operates with a waveform similar to the output waveform. After the time when the output of the amplifier has completely risen (τ), the discharge amplifier 1
By changing the input voltage of No. 3, the output voltage of the amplifier is likely to fall between VA and VA + VB. That is, as described above, the charge amplifier 12 and the discharge amplifier 1
3 can easily enter the drive region with only the bias current. Therefore, useless interference by the two amplifiers is reduced, and the level is easily settled. Naturally, unlike the case where the initial offset voltage is large even when the driving is performed only with the bias current, the overshoot is suppressed, and the time until the return is reduced in proportion to the offset voltage. Therefore, the drive waveform has less distortion (ringing) and less wasteful charge and discharge.

2. When configured with a high-speed amplifier (see FIGS. 1 and 6).

Since the operation of the amplifier is faster than the liquid crystal driving time, if the offset voltage is made small, even if ringing occurs due to interference between the two amplifiers constituting the push-pull amplifier 14, the driving time of the switch SW can be reduced. In this case, there is little effect on the liquid crystal display because the information is settled in a short time. However, in this case, overshoot and undershoot are repeated in a short period of time, so that the load capacity of the liquid crystal panel 11 is unnecessarily charged and discharged during this period (output waveform). The larger the load capacity, the more wasteful current consumption is lost.

When the offset voltage of the discharge amplifier 13 is large (output signal), even if the amplifier itself is high-speed, as described above, the bias current of the output stage of each amplifier is between VA and VB (= VA + offset voltage). Therefore, the time until stabilization is determined by the bias current and the output load even if the internal operation of the amplifier is fast. Therefore, there is no problem if the bias current is increased so as not to affect the liquid crystal. However, the current consumption increases, and the bias current is consumed even when the load is not driven, resulting in unnecessary current loss. Unless the bias current is increased, the waveform shift greatly affects the display quality.

On the other hand, in the method of switching the offset voltage of the present invention, the offset voltage is increased at the timing when the switch SW of the output stage is turned ON, and after a certain time (after the rise time), unlike the low-speed amplifier configuration described above. In addition, the offset voltage is reduced, which is effective. An example of a driving waveform according to this method is shown in an output waveform. The switching timing is indicated by the offset switching control signal. The offset voltage is increased immediately before the output is switched, and the offset voltage is decreased at the timing when the amplifier rises (τ = approximate rise time).

When the switch SW is turned on, the output greatly overshoots because the offset voltage is large. However, this overshoot time (≒ rise time) does not affect the display because the amplifier is fast.

Next, if the offset of the discharge amplifier 13 is reduced after the above time, the output of the amplifier becomes VA
To VB, the discharge amplifier 13 (or the charge amplifier 12) operates to bring the level closer to VA (VB). However, the operation of the amplifier at this time is different from when the output is first turned on, and the output voltage of the amplifier is close to a certain extent in both the discharge amplifier 13 and the charge amplifier 12 (the state in which the output has risen to the vicinity of VA = (Within several percent of VA), it is difficult for overshoot and undershoot to occur as in the case where the offset voltage described earlier is small. Even if it is simply considered that the overshoot occurs at a constant ratio of the waveform height, the overshoot of the rectangular wave at the time of outputting a voltage of several tens of volts and the rectangular wave changing from within a few% of VA to VA is the first overshoot. Obviously, this will be a few percent of the overshoot.

Accordingly, in this case, useless ringing and useless charge / discharge loss at the time of switching as in the case where the initial offset voltage is small is prevented, and VB (= VA + offset voltage) is changed to VA by switching the switch SW. Unlike the case where the offset voltage is large by approaching, the output error of the amplifier is reduced and the display quality is not degraded.

Therefore, according to the present invention, except for the initial timing at the time of output switching, useless overshoot and undershoot do not occur, a current consumption loss is small, and a drive waveform with little waveform distortion is realized.

In the above description, the level voltages V1, V2, V
4 is a description of the case where the charge is the main capability and the discharge is the auxiliary capability, and is an operation description corresponding to FIG. 1. As for the level voltages V3 and V5, the discharge is the main, and FIG. The corresponding operation is the same except that the driving waveform diagram and the offset voltage are in the opposite directions, and the description is the same, so the description is omitted here.

Therefore, by controlling the offset voltage that determines the operating range of the bidirectional current driving capability of the push-pull amplifier composed of two single ends in accordance with the drive or connection timing of the liquid crystal panel load, By suppressing the ringing at the time of driving the load, it is possible to reduce the unnecessary current consumption and the waveform distortion affecting the display.

A push-pull amplifier whose output is more stable is formed by sharing the output of the charge amplifier 12 and the output of the discharge amplifier 13. The input voltage of the discharge amplifier 13 is The through current between two amplifiers is suppressed by giving an offset voltage from the input voltage, and the through current between two single amplifiers is controlled by controlling the offset voltage according to display switching (load switching). In addition, more stable output of the output voltage (output with less distortion) is enabled.

FIG. 7 is a block diagram of a liquid crystal drive power supply circuit according to another embodiment of the present invention.

In this embodiment, the basic configuration is the same as that of the above embodiment, but the control of the amplifier is further devised. In FIG. 7, the discharge amplifier 23
Is connected, and the same input voltage as that of the charge amplifier 22 is input.

In this case, the discharge amplifier 23 is controlled by the control circuit 26 by one or more output control signals (analog or logic).

FIG. 8 is a configuration diagram of single-ended amplifiers 22a and 23a of another embodiment.

The single-ended amplifiers 22a and 23a
Are used for the charge amplifier 22 and the discharge amplifier 23 shown in FIG.

The single-ended amplifiers 22a and 23a
By controlling (changing) the current flowing through the MNA and MNB (or MPA and MPB) by the two output control signals OFF1 and OFF2, the balance of the differential stage of the amplifier is shifted and the same input is applied even when the same input is input. It is possible to give an apparent offset voltage.

This offset voltage is OFF1, OFF
2, the offset voltage can be controlled by changing this current in the same manner as in the above-described embodiment.

In the other embodiment, since the same level can be input to the charge amplifier 22 and the discharge amplifier 23 as shown in FIG. 7, for example, the number of resistance divisions can be reduced, and the switch SW is not required. And the circuit (layout) becomes simpler. Also, in the previous embodiment where the offset voltage was intentionally created by a resistor,
Although the offset voltage changes each time the liquid crystal drive voltage VLCD changes, this method does not depend on the liquid crystal drive voltage VLCD. Further, in this embodiment, OFF1 and OF
Although the two signals F2 and F2 are used, the difference between the currents (offset currents) flowing through the two input transistors in the differential stage depends on the offset voltage. Since a plurality of offset voltages can be changed by only one signal, there is an effect that only one signal line is required.

[0076]

According to the present invention, there is provided a liquid crystal driving power supply circuit comprising: a plurality of predetermined reference voltage output units; a push-pull amplifier which receives the reference voltage and outputs a level voltage for driving a liquid crystal display element; And a switch for selecting a reference voltage to be input to one of the push-pull amplifiers from the reference voltage described above, so that low current consumption and display quality can be realized.

Further, since the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element, the current consumption can be reduced more accurately and the display quality can be improved more accurately. be able to.

The push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element. Since the reference voltage is selected and input, the discharge can be performed more reliably, and the current consumption can be reduced and the display quality can be improved.

Further, the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging, and the charge amplifier and the discharge amplifier are single-ended amplifiers. It is possible to reliably reduce the current consumption and improve the display quality.

The push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging. The reference voltage input to the amplifier capable of discharging is based on the input voltage. Since a voltage for offsetting the reference voltage is provided, unnecessary current consumption and waveform distortion affecting display can be reduced.

Further, since the offset voltage is controlled in accordance with display switching, it is possible to suppress ringing at the time of driving the load of the liquid crystal panel, and realize unnecessary current consumption and reduction of waveform distortion affecting display. it can.

Further, the liquid crystal drive power supply circuit of the present invention includes an output section for a predetermined reference voltage, and a push-pull amplifier for receiving the reference voltage and outputting a level voltage for driving a liquid crystal display element. Since one of the amplifiers constituting the pull amplifier is configured to be subjected to discharge control, it is possible to realize a simpler structure, lower current consumption and improved display quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid crystal drive power supply circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a liquid crystal drive power supply circuit according to an embodiment of the present invention.

FIG. 3 shows a configuration diagram of a single-ended amplifier.

FIG. 4 shows current characteristics of a push-pull amplifier composed of two charge amplifiers and discharge amplifiers having different capabilities.

FIG. 5 shows a waveform diagram when a low-speed amplifier is used.

FIG. 6 shows a waveform diagram when a high-speed amplifier is used.

FIG. 7 is a configuration diagram of a liquid crystal drive power supply circuit according to another embodiment of the present invention.

FIG. 8 shows a configuration diagram of a single-ended amplifier according to another embodiment.

FIG. 9 shows an overall configuration diagram of a conventional liquid crystal driving device.

FIG. 10 shows an example of actual driving waveforms of a conventional COM electrode and SEG electrode.

FIG. 11 shows a configuration diagram of a conventional liquid crystal drive power supply circuit.

FIG. 12 shows a configuration diagram of a conventional example in which two amplifiers having different driving capabilities are switched as required.

[Explanation of symbols]

12, 22 Charge amplifier 13, 23 Discharge amplifier 17 Output driver 11 Liquid crystal panel 15 Reference voltage output unit 14 Push-pull amplifier 12a, 13a, 22a, 23a Single-ended amplifier 16, 26 Control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA10 NA31 NA43 NA53 NA80 NC04 NC23 NC90 ND03 ND39 5C006 AC02 BA19 BB12 BF43 BF44 FA00 FA22 FA25 FA26 5C080 AA10 BB05 DD03 DD26 FF01 FF02 FF03 FF08 FF09 JJ04 JJ04 JJ02 JJ04

Claims (7)

[Claims] An output unit for outputting a plurality of predetermined reference voltages;
A push-pull amplifier that inputs the reference voltage and outputs a level voltage for driving a liquid crystal display element; and a switch that selects a reference voltage to be input to one of the push-pull amplifiers from the plurality of reference voltages. A liquid crystal drive power supply circuit characterized by the following. 2. The liquid crystal drive power supply circuit according to claim 1, wherein the push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element. 3. The push-pull amplifier includes an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging the liquid crystal display element. 2. The liquid crystal drive power supply circuit according to claim 1, wherein the reference voltage is selected and input. 4. The push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging, and the charge amplifier and the discharge amplifier are single-ended amplifiers. 2. The liquid crystal drive power supply circuit according to claim 1, wherein: 5. The push-pull amplifier has an amplifier capable of charging the liquid crystal display element and an amplifier capable of discharging, and the reference voltage input to the amplifier capable of discharging is based on the input voltage. 2. The liquid crystal drive power supply circuit according to claim 1, having a voltage for offsetting a reference voltage. 6. The liquid crystal drive power supply circuit according to claim 5, wherein the offset voltage is controlled according to display switching. 7. An output unit for a predetermined reference voltage, and a push-pull amplifier for receiving the reference voltage and outputting a level voltage for driving a liquid crystal display element, wherein one of the amplifiers constituting the push-pull amplifier is provided. A liquid crystal drive power supply circuit characterized by performing discharge control.