JPS5943757B2 - Display panel drive method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a display element, and more particularly to a method for driving an AC-coupled gas discharge display panel as an output device for information equipment having a drive circuit that reduces power consumption.

This type of AC coupled gas discharge display panel has a common segment corresponding to each digit, and is operated by scanning the digit signal for dynamic display.

Such AC coupled gas discharge display panels are compared to display panels using light emitting elements such as light emitting diodes (IJEDs), filament tubes, fluorescent tubes, etc.
Although it is particularly excellent in terms of luminous efficiency, display clarity, temperature characteristics, aging, etc., it is necessary to apply an AC pulse of more than 100 volts as the drive voltage necessary for light emission.

This drive voltage of more than 100 volts is a high-voltage dedicated power source that causes the display panel to emit light, and therefore the power loss in the drive circuit for generating discharge is large and uneconomical. Therefore, in order to facilitate integration of the drive circuit into an IC and to obtain an economical drive circuit, the current capacity of the drive circuit must be reduced. The purpose of the present invention is to
As described above, it is an object of the present invention to provide a driving method for an AC coupled gas discharge display panel that facilitates the integration of a driving circuit into an IC and reduces power consumption.

The system of the present invention includes a plurality of digit display sections each having one digit electrode and a plurality of segment electrodes, and a plurality of connection points to which corresponding segment electrodes between the plurality of digit display sections are connected to each other. one digit electrode and one segment electrode constitute one segment element, and by applying first and second voltages to the digit electrode and segment electrode of each segment element, respectively, a corresponding segment is formed. In one driving method of an AC-coupled gas discharge display panel in which the elements emit light, a first transistor is provided with a segment light emission control signal at its base and whose emitter is grounded, and a collector of the first transistor is connected to the base and connected to the collector. a plurality of segment drive circuits each having a second transistor to which the second voltage is supplied and a diode connected between the base and emitter of the second transistor; a segment driving means in which an emitter is connected to a corresponding one of the plurality of connection points, and the first voltage is applied to the digit electrodes of the plurality of digit display sections in a time-division manner sequentially in response to a digit emission control signal; a digit driving means for supplying the second transistor to the base of the second transistor of the plurality of segment driving circuits only for a period involved in the light emitting operation at every predetermined time; and switch means for supplying the voltage through the load resistor.

Next, a description will be given with reference to the drawings.

FIG. 1 shows the applied voltage waveform in the driving method of this type of AC coupled gas discharge display panel.

In this method, as shown in FIG. 1a, for five drive voltages VO, that is, segment output voltages of the display element drive time width Tl and recovery time width T2, as shown in FIG. 1B, c,
As shown in d and e, the digit output is always at the above-mentioned 1 drive voltage V.
O, and becomes low level only during the scan time of the corresponding digit number in synchronization with the high level time of the segment output.
For example, if the relationship between the drive voltage VO and the discharge starting voltage VT of the electrode plate is set to 0 so that VO<VT>20,
As shown in Figure 1f, only when the digit signal and segment signal are switched in the opposite direction at the same time, the effective voltage applied to the display element becomes 2V0, and the matching point at the rising edge of each segment output and the falling edge of each digit output, or When the falling edge of each segment output matches the rising edge of each digit output, the display element emits light, but when only one of the segment output and the corresponding digit output is switched, the display element emits VO. Does not emit light due to low VT. However, various circuits as shown in FIG. 2 have conventionally been used as switching circuits for driving each segment and each digit.

The circuit shown in FIG. 2a is composed of an NPN transistor Q1 and a load resistor 21. The input (IN) of the signal supply section is supplied to the base electrode of the transistor Q1, the emitter electrode is grounded, and the collector electrode is connected to the base electrode of the transistor Q1. A voltage V0 is input through the collector resistor 21 to drive the AC coupled gas discharge display panel. The circuit shown in FIG. 2b also includes a PNP transistor Q2, a base capacitor 23 for converting the input level from the signal supply section, and a resistor 24 connected between the base and emitter electrodes of the transistor Q2. It is composed of a collector load resistor 22. These transistor switching circuits shown in Figures 2A and 2B have the simplest circuit configuration, but because the recovery time at turn-off is slow, the repetition frequency, which affects the brightness of the displayed characters on the AC coupled gas discharge display panel, is low. In addition, the power loss caused by the resistors 21 and 22 when the transistors Ql and Q2 are switched on is extremely large.

In addition, the circuit shown in FIG. 2C has an emitter electrode. A PNP transistor Q3 connected to the drive potential VO, a capacitor 25 connected to the base electrode of this transistor Q3 for converting the level of the input voltage (IN) from the signal supply section, and the emitter electrode and base of the transistor Q3. A resistor 26 bridged between the electrodes 1, a collector resistor 27,
It is composed of an NPN transistor Q4 whose collector electrode is connected to the collector electrode of the transistor Q3 via the collector resistor 27, and the input voltage (IN) is directly supplied to the base of Q4.

The collector electrode and collector resistor 2 of this transistor Q4
The output terminal (0UT) is taken out from the connection point 7. The transistor switching circuit configured in this way forms a complementary circuit, and there is almost no part that consumes power through direct current, so the capacity of the drive power supply for driving the display elements can be reduced. can.

However, it is relatively difficult to switch PNP transistor Q3 and NPN transistor Q4 at the same time and convert the base input voltage level of transistor Q3, and since transistors Q3 and Q4 have opposite polarities, However, there are problems such as difficulty in converting this transistor switching circuit into an IC. Second
In the switching circuit shown in Figure d, the collector electrode is at the potential V
an NPN transistor Q5 connected to O, a resistor 28 inserted between the collector electrode and the base electrode of this transistor Q5, an anode electrode connected to the emitter electrode of the transistor Q5, and a cathode electrode connected to the base electrode of the transistor Q5. A connected diode D and an NPN transistor Q6 whose collector electrode is connected to the cathode electrode of the diode D and whose emitter electrode is connected to ground potential.
The input terminal (N) is taken out from the base electrode of the transistor Q6, and the output terminal (0UT) is taken out from the anode electrode of the diode D.

Such a transistor switching circuit has an input (I
When N) becomes high level, the current sink transistor Q
When transistor Q5 becomes conductive and the input (IN) becomes low level, transistor Q5 becomes conductive, forming an off-buffered circuit, so the turn-off characteristics are much better than the circuit shown in Figure 2a. , has the disadvantage that extra power is consumed in the resistor 28 when the transistor Q6 is in the on state.

However, since two transistors with the same polarity are used and there is no need for a level conversion capacitor,
It has the advantage that it is extremely easy to convert the drive circuit of the display element into 1C, and that it is easy to interface with a general-purpose transistor-transistor logic circuit (TTL circuit). The present invention focuses on the above-mentioned points, and the second
The purpose of this invention is to further improve the switching circuit shown in FIG. d so that the drive circuit for an AC-coupled gas discharge display panel can be easily converted into a C-type drive circuit, and to obtain a single drive circuit with low power consumption.

However, if the circuit shown in Figure 2 d is used as it is as a segment drive circuit, when the display panel is not displaying anything, that is, when the AC coupled gas discharge display panel is not discharging, all segment outputs must be set to a low level, which increases the load. Power loss in resistor 28 increases.

In this case, if the number of segments is S, the resistance value of the load resistor 28 is R, and the digit drive circuit uses the circuit shown in Figure 2d, the power loss in all segments is equal to SVO when no light is emitted.
It becomes 2/R. Also, when the time width T of the segment output pulse voltage and the recovery time T2 are equal, the total loss due to each digit driver is VO2/2R, so the total is SVO2/
The power loss is R+VO2/2R-(2S+1)·VO2/2R. By the way, the voltage of the segment output waveform is at a low level because the transistor Q6 is turned on regardless of the displayed characters during the recovery time T2 of the segment output pulse.

Therefore, as shown in FIG. 3, the power supply o side of the load resistor 28 is
A switch circuit 31 that is cut off only during T2 is connected to a load resistor 2.
8 in series, the power consumption of the load resistor 26 that occurs during T2, which is not involved in light emission, is reduced. Therefore, when the circuit shown in Fig. 3 is used as the segment 1 drive circuit, the voltage VO
When t1=T2, the total segment power consumption of SVO
When the circuit shown in Fig. 2d, which has the same drive circuit as the digit, is used as a 2/2R switch circuit, the power consumption of the switch circuit is VO2.
/2R, and the total power consumption of each digit 5 drive circuit is VO2/2R, so the total power consumption is (S+2)·VO2/2R. If the circuit shown in FIG. 3 is used in this way, the power consumption ratio will be P(S+2)/(2S+1) compared to the conventional circuit. Generally, if you include the decimal point, it is S-8, so if you substitute S=8 into the above equation of P=(S+2)/(2S+1), it becomes P-0.6, which is about 40% of the power for the drive circuit. You can save money. FIG. 4 shows a display panel drive circuit according to an embodiment of the present invention.

In the figure, display panel 45 has nine digit displays each having one digit electrode and eight segment electrodes.

The outputs of the nine digit drive circuits 43-1 to 43-9 are applied to the nine digit electrodes in a one-to-one correspondence.

Corresponding segment electrodes between each digit display section are all connected to each other, and each segment 1 drive circuit 44-1 to
44-8 output is given. Switch circuit 31. All of the digit drive circuits 431 to 43-9 are the circuits shown in FIG. 2d. The segment drive circuits 44-1 to 44-8 together with the switch circuit 31 constitute the circuit shown in FIG. The digit drive signal supply section includes an inverter 47-1 that manually outputs an output corresponding to a designated digit of a 9-ary counter 41 that counts the control clock and a decoder 42 that selectively and sequentially selects the output signal from the counter 41. ~47-9. Further, the segment drive signal supply section includes NAND gates 48-1 to 48-8 for mixing the selection signal of the segment input and a high frequency signal, that is, a control tallock, for obtaining a pulse-like output at the time of selection, and a control tallock signal. an inverter 49 that inverts the
It is composed of Generally, the time width t1 of the control clock
The ratio of T2 and T2 is 1:1, the counter 41 is activated at the rising edge of the control clock, a designated digit is selected in the decoder 42, and the gated signal is sent to the inverter 47 at time t1.
It enters the current sink transistor Q6 of the digit drive circuits 43-1 to 43-9 through the digit drive circuits 43-1 to 43-9, and only the digit output of the selected digit drive circuit 43-1 to 43-9 becomes low level. On the other hand, in the segment drive signal supply section, the specified segment input signal and control clock signal are supplied as base signals to the transistor Q6 of the corresponding segment drive circuit via a NAND circuit that receives the input signals.
An inverted signal of the control clock is supplied to the current sink transistor Q6 of the switch circuit 31 via the inverter 49. At this time, the segment input corresponding to the segment electrode to emit light is at a high level, and the segment 1 drive circuit whose gate is disconnected from the light emission control clock is at a high level. During the recovery time T2, the light emission control clock is at a low level and the gate cannot be removed, so the digit and drive circuits are all at a high level, and all the segment drive circuits are at a low level. In this way, the display element 45 emits light only when the output of the digit drive circuit is at a low level and the output of the segment 5 drive circuit is at a high level. The switch circuit 31 is connected so that its output is at a low level during the pulse recovery time T2, and at this time the segment drive circuit 44
Since the outputs of -1 to 44-8 are also at a low level, no power loss occurs in the load resistor 46. When the clock signal is on, the current sink transistor Q6 of the switch circuit 31 is off and the transistor Q5 is conductive, so that the output voltage of the switch circuit 31 becomes approximately equal to the 1 drive voltage VO.
At this time, the designated segment drive circuit becomes conductive and the AC coupled gas discharge display panel 45 emits light. In this case, in the time width t1, the output of the switch circuit 31 is almost equal to the drive voltage VO and operates in the same manner as the conventional one, and the interface of the display element 45 is exactly the same as the conventional one, so that the driving capability does not decrease. In addition, in the present invention,
When the drive voltage VO is a negative voltage, even if a PNP transistor is used as the transistor in each drive circuit, the same effect as in the above embodiment can be achieved.

As explained above, by configuring the present invention to include a power reduction switch circuit, the present invention becomes an economical drive circuit with low power consumption, and also makes each drive circuit the same so that it can be integrated into one type of integrated circuit. It has the advantage of being easy to integrate into an IC.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the AC coupled gas waste electricity display.

Claims (1)

[Claims] 1. A plurality of digit display parts each having one digit electrode and a plurality of segment electrodes, and a plurality of connection points to which corresponding segment electrodes between the plurality of digit display parts are connected to each other. One segment electrode constitutes one segment element, and the corresponding segment element emits light by applying first and second voltages to the digit electrode and the segment electrode of each segment element, respectively. In the panel driving method, a first transistor has a base to which a segment light emission control signal is applied and whose emitter is grounded, and a second transistor has a collector connected to the base and the second voltage is supplied to the collector. The emitter of the second transistor of each segment drive circuit is located at one of the plurality of connection points. segment driving means respectively connected to the corresponding ones; digit driving means for sequentially and time-divisionally supplying the first voltage to the digit electrodes of the plurality of digit display sections in response to a digit emission control signal; A third voltage is supplied via a load resistor to the bases of the second transistors of the plurality of segment drive circuits for a period involved in the light emitting operation at predetermined time intervals to make the second transistors conductive. A drive method for a display panel, characterized by comprising a switch means.