JPH0262587A - Power unit for liquid crystal driving - Google Patents

Abstract

PURPOSE:To erase unstable display contents by detecting the rise/fall state of an input power source and supplying a driving voltage to a liquid crystal display part only when a reference voltage is reached. CONSTITUTION:When the input load power source 5 is turned on, the output of an input voltage detection part 11 is V+ and the output of a reference voltage generation part 10 is V-. That is decided by a voltage comparator 12 and a circuit switch part 13 is operated with its output. When the power source rises and falls, the switch part 13 is turned on and an element 9 for voltage setting is passed, so a voltage regulator does not generate a normal liquid crystal driving voltage and nothing is displayed on a liquid display part 1. Further, the switch is turned off after the power source rises to make the element 9 effective, and consequently the set liquid crystal driving voltage is generated to make a proper display.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electronic equipment equipped with a liquid crystal display.

2. Description of the Related Art In recent years, electronic devices have become more sophisticated, smaller, and lighter, and more and more electronic devices are equipped with liquid crystal displays as display means.

Hereinafter, a conventional liquid crystal driving power supply device will be described with reference to the drawings.

FIG. 2 shows an example of a conventional liquid crystal driving power supply device.

In FIG. 2, 1 is a liquid crystal display unit consisting of a liquid crystal control unit, a drive unit, and a liquid crystal panel; 2 is a power supply (voC) for the control system of 1;
3 is a ground, and 4 is a variable voltage divider that variably takes out the liquid crystal drive power source 6 (-.ut) from the input negative power source 6 (-Vin). Each power source 2 and 5 is provided from a part other than the present one.

Regarding the liquid crystal drive power supply device configured as above,
The operation will be explained below.

In FIG. 2, 2 is a liquid crystal control system power supply: VO. , 6 when the input negative power supply knee V, n is given. C1-vin
and 6 liquid crystal drive voltage knee ■. The movement of , is shown in Figure 3. When the device is turned on at time t:lo, -V. U,
is generated following the rise of vcc and -vi, and becomes the voltage set by the variable voltage divider 4, and is displayed on the liquid crystal. Further, the user operates the variable voltage divider 4 to obtain -V in order to obtain a more appropriate display contrast. ut may also be adjusted. 1=1. When you turn off the device with
Following the falling of voo and -vl, ■. , also decays,
The LCD display also disappears.

Furthermore, Fig. 4 is an improved example of the previous example, with 1° 2.
3, 5.6 are similar to those shown in FIG. 7 is a three-terminal voltage regulator, 8 is a bias element for 7, and 9 is a voltage setting element for the liquid crystal drive power source 6. In this case as well, the user operates the voltage setting element 9 to set the liquid crystal drive power source 6 to obtain an appropriate display contrast. In general, the contrast adjustment shown in FIG. 4 is more precise than the example shown in FIG. 2, but when the input power is turned on and off, the liquid crystal drive power is generated and attenuated in the same way as in the previous example.

Problems to be Solved by the Invention However, with the above-mentioned configuration, it is difficult to solve the problem in contrast to the general case where there is a transient rise and fall with a certain slope when charging and cutting.
Because of the power supply for driving the liquid crystal that is generated and remains during the unstable period of the liquid crystal display, there is a secret point that for some time there will be chaotic display contents that are not controlled by the liquid crystal.

The present invention has been made with attention to the above-mentioned conventional technology, and is a liquid crystal drive device that generates a liquid crystal display after a control system is established when the power is turned on to the device, and that can immediately erase the displayed content when the power is turned off to the device. It provides a power supply device.

Means for Solving the Problems In order to achieve this object, the liquid crystal driving power supply device of the present invention comprises an input voltage detection section, a reference voltage generation section, a voltage comparison section for both outputs, a circuit switch section, and a voltage regulator section that is switched by this.

Operation The present invention detects nine rising and falling states of the input power supply with the above-mentioned configuration, and supplies a driving voltage to the liquid crystal display section only when the reference voltage is reached.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a liquid crystal driving power supply device in an embodiment of the present invention.

In FIG. 1, 1 is a liquid crystal display unit consisting of a liquid crystal control unit, a drive unit, and a liquid crystal panel; 2 is a power source for the liquid crystal control unit in 1; and 3
is ground, 6 is input negative power supply, 6 is voltage regulator 7
1 is a liquid crystal drive power supply applied to 1, 8 is a bias element 7, 9 is a voltage setting element 6, 1o is a reference voltage generator consisting of a Zener diode and a bias resistor, and 11 is a component consisting of two resistors. 12 is a voltage comparator, and 13 is a circuit switch consisting of a transistor and a resistor.

Regarding the liquid crystal drive power supply device configured as above,
The operation will be explained below.

Now, as shown in Fig. 6(a), the liquid crystal control system power supply: V
When the input negative power supply knee Vi is applied to c, , 6 (time 1=
Power on at 1o, 1=1. ), the output of the input voltage detection section 11 is +, and the output of the reference voltage generation section 1° is V-.
becomes. This is determined by the voltage comparator 12, and the circuit switch section 13 is operated by the output thereof. This switch operation is shown in Fig. 6 (l).

When the power is turned on and off, the switch is turned on and the voltage setting element 9 is passed, so the voltage regulator does not generate a normal liquid crystal drive voltage and nothing is displayed on the liquid crystal display section 1. Further, after the power is turned on, the switch is turned off and the voltage setting element 9 becomes effective, thereby generating the set liquid crystal drive voltage and displaying properly.

The liquid crystal drive voltage at this time is -V. U, becomes as shown in FIG. 6(C).

As described above, according to this embodiment, by detecting the input power supply, comparing the voltages, and switching the output power supply, unnecessary liquid crystal drive power supplies are turned off when the input power supply rises and falls at 9 o'clock. be able to.

In the present invention, a voltage comparator is used as the determination section for controlling the circuit switch section, but this may be configured by a switch circuit using a transistor.

Effects of the Invention As described above, the present invention erases unstable display contents by not applying a liquid crystal drive voltage during the period when the liquid crystal display control system is unstable at power-up and power-down. It has great practical effects, such as ease of use and image of the device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a liquid crystal driving power supply device in an embodiment of the present invention, and FIG. 5 is an operation explanatory diagram in the same embodiment.
FIG. 2 is a block diagram of a conventional liquid crystal driving power supply device, FIG. 3 is a voltage waveform diagram of the conventional example, and FIG. 4 is a block diagram of another conventional example. 1...Liquid crystal display unit, 2...Control system power supply, 3...Ground, 4...Variable voltage divider, 5... Input negative power supply, 6...LCD drive power supply, 7...Voltage regulator, 8...
... Bias element, 9... Voltage setting element,
10... Reference voltage generation section, 11... Input voltage detection section, 12... Voltage comparator, 13...
...Circuit switch section.

Claims (1)

[Claims] Consisting of a regulator that stabilizes the input voltage, an input voltage detection section, a reference voltage generation section, a voltage comparison section for both outputs, and a circuit switch section that controls the output voltage of the regulator based on the comparison result. A liquid crystal drive power supply device featuring: