JPH0738103B2 - Gas discharge panel drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] When driving a gas discharge panel such as used in a plasma display panel, when the potential of an output electrode terminal is set to the ground potential, a current limiting element is present in a current path flowing to the ground terminal. Is a drive circuit of the gas discharge panel that prevents the malfunction of the logic circuit in the vicinity by inserting the.

FIELD OF THE INVENTION The present invention relates to a circuit for driving a gas discharge panel such as used in a plasma display panel.

In the conventional circuit of this kind, since the discharge to each drive electrode of the discharge panel and its disappearance are controlled one after another, the logic circuit malfunctions due to a large current flowing from the ground connection point of the drive element to the logic circuit for controlling the drive element. However, improvement measures are being considered.

[Prior Art] A gas discharge panel is one in which a discharge gas is sealed between glass substrates, and a high voltage is selectively applied to electrodes orthogonal to each inside of the glass substrates to discharge at a predetermined place. Wake up. At this time, a voltage waveform that causes discharge and a voltage waveform that sustains discharge are applied and driven through a drive circuit that uses a semiconductor element. FIG. 5 shows the driving circuit. In FIG. 5, 1 and 2 are transistors, 3 is an output electrode terminal of the transistor 2 (common electrode terminal of the transistor 1), 4 is a ground terminal, 5 is a control electrode terminal of the transistor 2, 61 and 62 are diodes, and 7 is A resistor element, 8 is an operating voltage application terminal, 9 is a stray capacitance, and
What happens between the emitters is shown.

Further, FIG. 6 shows a voltage waveform of the output electrode terminal 3 in FIG.

In FIG. 6, the potential applied to the control electrode terminal 5 is "L".
Then, the transistor 2 is turned off, and the voltage Vpp of the operating voltage applying terminal 8 is set to a high voltage such as 140V. At that time, a current flows between the base and the emitter of the transistor 1 through the resistor 7 and turns on the transistor 1. The potential of the output electrode terminal 3 becomes equal to Vpp. If Vpp is lower than the potential of the output electrode terminal 3, the current from the output electrode terminal 3 passes through the diode 61 and flows between the base and collector of the transistor 1, so that the potential of the output electrode terminal 3 is restored again. Same as Vpp. Therefore, when the transistor 2 is turned off and the transistor 1 is turned on and a drive voltage of the discharge panel is applied to Vpp, a waveform having the same change as the potential of the output electrode terminal 3 is obtained (during time T1 in FIG. 5). That when selecting the electrode for discharge, to turn on the transistor 2 at time t ₂ of FIG. 5 as "H" potential of the control electrode terminal 5. When the voltage Vpp at the operating voltage application terminal 8 is positive and large, the transistor 2 is turned on, so that the potential of the collector electrode thereof drops to the ground potential. At this time, terminal 8
Current flows from Vpp through resistance element 7,
If the value of the resistance element 7 is set to be sufficiently large, it will be small. At this time, a current corresponding to the original potential Vpp of the output electrode terminal 3 flows through the transistor 2 to the ground terminal 4.

On the other hand, there is a control integrated circuit including a logic circuit for controlling a large number of driving elements such as the transistors 1 and 2, and the ground terminal thereof is also commonly connected to the ground terminal 4.

[Problems to be Solved by the Invention] In the circuit shown in FIG. 4, the current flowing through the conductor of the ground terminal 4 is extremely large as compared with the operation control current of the drive element or the operation current of the logic circuit. In some cases, the drive element control logic circuit malfunctions because noise is generated due to a large current flowing when the transistor is off.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a drive circuit which solves the above-mentioned drawbacks and prevents malfunction of the drive element control logic circuit when the gas discharge panel is driven.

[Means for Solving Problems] FIG. 1 is a diagram showing a principle configuration of the present invention. In FIG. 1, 10 is an overall drive circuit for driving a gas discharge panel, 1 and 2 are transistors, 3 is an output electrode terminal of the transistor 2 (for example, the same as the common electrode terminal of the transistor 1), and 4 is a ground. Terminals, 5 are control electrode terminals of the transistor 2, 8 is an operating voltage applying terminal, and 11 is a current limiting element inserted in the drive current circuit of the transistor 2.

In the drive circuit of the gas discharge panel, which connects the output electrode terminal 3 of the drive element 2 to which a high voltage is applied and the gas discharge panel, and sets the potential of the output electrode terminal 3 to the ground potential 4 by the signal of the control signal application terminal 5, The essential constituent feature of the present invention is that the current limiting element 11 is inserted in the current path flowing to the ground terminal 4 when the potential of the output electrode terminal 3 is set to the ground potential.

[Operation] When the gas discharge panel is driven to generate discharge, the signal at the control signal application terminal 5 is set to "L" to turn off the transistor 2. Since the transistor 1 is turned on at that time, the potential of the output electrode terminal 3 rapidly rises to the potential Vpp of the operating voltage terminal 8. At this time, discharge starts. FIG. 2 is a diagram showing a potential change of the output electrode terminal 3 of the transistor 2. In FIG. 2, the potential of the output electrode terminal 3 becomes Vpp at time t ₄ . Next, at time t ₅ , a “H” signal is applied to the control signal application terminal 5 to turn on the transistor 2. The potential of the output electrode terminal 3 decreases and approaches the potential of the ground terminal 4. At this time, a current having a magnitude corresponding to Vpp is instantaneously transmitted through the transistor 2 to the ground terminal 4
However, the waveform is distorted by the current limiting element 11. Therefore, the potential of the output electrode terminal 3 gradually becomes zero at time t ₆ .

The potential of the output electrode terminal 3 needs a sharp rising waveform at the time of rising to start discharge, but may have a dull waveform because it has no direct relation to discharging at the time of falling. Since the current change is gentle, even if there is a logic circuit with a common ground connection, malfunction does not occur.

[Embodiment] FIG. 3 shows a concrete circuit diagram as an embodiment of the present invention.
In this example, the current type of the transistor is composed of an NPN type 2 and a PNP type 20, and a resistance element is used as the current limiting element 11. The operating voltage uses + Vpp and −Vpp. The drive transistors 2 and 20 shift the application phase of the "H" signal from the control signal application terminal by 180 degrees. Therefore, the potential of the output electrode terminal of the transistor with respect to the gas discharge panel 30 is as shown in FIG. The code for the time at this time is the same as that in FIG.

As described above, according to the present invention, when the potential of the output electrode terminal is set to the ground potential, the current limiting element is inserted in the current path flowing to the ground terminal, and the falling current waveform of the drive waveform is blunted. Therefore, no noise is generated in the logic circuit for controlling the drive element, and no malfunction occurs.

[Brief description of drawings]

 FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, FIG. 3 is a diagram showing an embodiment of the present invention, and FIG. 4 is an operation waveform of FIG. FIG. 5 is a diagram showing a conventional drive circuit, and FIG. 6 is an operation waveform diagram of FIG. 1, 2 ... Transistor 3 ... Output electrode terminal 4 ... Ground terminal 5 ... Control signal application terminal 11 ... Current limiting element

Claims (1)

[Claims] 1. The output electrode terminal (3) of a drive circuit (10) to which a high voltage is applied is connected to a gas discharge panel, and the potential of the output electrode terminal (3) is changed by a signal from a control signal application terminal (5). In the drive circuit of the gas discharge panel which is set to the ground potential, when the potential of the output electrode terminal (3) is set to the ground potential, the current limiting element (11) is inserted in the current path flowing to the ground terminal (4). The drive circuit for the gas discharge panel.