DE2218597C2 - Circuit for operating a gas discharge display panel - Google Patents

Description

The invention relates to a circuit for operating a gas discharge display panel with the ones mentioned in the preamble of claim 1 features listed.

Such a circuit is the subject of the earlier patent according to DE-PS 21 36 412.

The structure of such gas discharge display panels is known (US-PS 34 99 167). To control the discharge cells, in the proposed circuit, each of the row or column electrodes is connected to a matrix selection element which has two diodes and a resistor which end in a common node. A resistance pulse generator is connected between the AC voltage source and the end of the resistor facing away from the junction, and a diode pulse generator is connected between the AC voltage source and the one diode.The pulse voltage is applied to the resistor, for example, by a transformer, which is used in particular at the high frequencies that are used the higher power loss is disadvantageous.
ίο It is also in the case of gas discharge display panels, which are provided with electrodes provided with dielectric layers and arranged in a matrix in rows and columns. Has limited discharge cells, known (US-PS 35 73 542) to apply voltage pulses to ignite and extinguish the discharge cells of an alternating voltage maintaining the discharge. The voltage pulses and the alternating voltage are generated in semiconductor circuits, the alternating voltage being transmitted to the addressing circuits via the windings of a transformer. The known circuit does not have any matrix selection elements, each with two diodes and a resistor.

The object on which the invention is based exists

in designing the generic circuit so that it has a higher repetition frequency and can be operated with a smaller power loss.

In a circuit of the generic type, this object is achieved according to the invention by means of the characterizing elements Part of claim 1 specified features solved. Advantageous further developments of the invention are characterized in the subclaims

With this circuit are much higher repetition frequencies and lower power losses are possible than with circuits with transformers or with active solid-state pulse circuits. Furthermore, the polarity of the circuit according to the invention can be easily determined reverse to make negative or positive pulse voltage circuits. In particular, the Invention transformers for high voltages in the addressing circuits avoided, since the transistor in simply via a coupling transformer with low power or another logical one Arrangement with circuit separation can be controlled. It is also possible to have the transistor in one To use a floating potential matrix. This reduces the dimensions and the Requirements for size and core material as well as capacities reduced. Also are the waveforms of the pulse voltages problem-free with regard to inductive feedback and transformer induction.

Embodiments of the invention are explained in more detail below with reference to the drawing
Fi g. 1 a matrix selection element with addressing and control circuit,

F i g. 2A is a simplified illustration of a gas discharge display panel with one matrix selection and addressing circuit each for the row and column electrodes,

Fig. 2B shows a matrix selection circuit in connection with addressing circuits for a number of row or column electrodes,

3A and 3B each a positive and negative Thyristor pulse generator for the diodes of the matrix selection elements,

FIGS. 4A and 4B each have a positive and negative Transistor pulse generator for the diodes of the matrix output

elective elements,

F i g. 5A and 5B each have a transistor circuit for the pulse voltage to be fed to a matrix selection element.

In Fig. 2A, a gas discharge display panel P consists of plates RS and CS on which row electrodes 50 and column electrodes 51 are provided, which are provided with dielectric layers 52 and 53, respectively. The plates are connected to one another at a small distance from one another by sealing spacers 54 and form a thin gas discharge space which is filled with a gas at a certain pressure. The row and column electrodes are each controlled by a matrix selection and addressing circuit 62 and 63, respectively

A matrix selection circuit 60 is provided for driving the row electrodes 50 and a matrix selection circuit 61 is provided for driving the column electrodes 51, each of which is fed by an alternating voltage source 10A or IOC with opposite polarity (± y _sy ) , the other poles of which are connected to one another and are at ground potential .

In Fig. 2B, a matrix selection circuit 60 is shown in more detail, the individual matrix selection elements D 1, D2 and R of which are each connected to a row electrode X 11... XNM. Furthermore, in FIG. 2B drive circuits 90, 91 for the diodes of the array select circuit 60 and drive circuits 92, 93 shown for the resistors in the array selecting circuit 60, the individual resistors R and diode D 1 of the matrix selection elements are manifolds A 1 ... AM or Bt ... ß / V interconnected.

In the circuit shown in FIG. 1, the matrix selection element consisting of the resistor R 1 and the diodes D 1 and D 2 has the same circuit structure as in DE-PS 21 36 412. Electrodes X are also selected and addressed by Pulse voltages that are applied to the voltage of an alternating voltage source 10 (V _s ) . The AC voltage source supplies rectangular, sinusoidal, trapezoidal, i.e. somehow shaped periodic waveforms. The voltage of the AC voltage source 10 can only be half the voltage required to operate the display panel if the remaining half is phase-shifted by 180 ° or is fed to the other electrodes from opposite polarity. Thus, for example, the row electrodes are fed with one half of the voltage and the column electrodes with the other voltage that is phase-shifted by 180 °.

The resistor A1 and the diodes Ol and D2 of each matrix selection element are connected together in a node N. A matrix selection element is provided for each electrode X of the display panel, the electrode in each case being connected to the node N (FIG. 2B). The end of the resistor R 1 facing away from the node N is connected to a pulse voltage source, the voltage pulse of which, in conjunction with the alternating voltage, is sufficient to change the discharge state of the discharge cell delimited by a row and column electrode. The pulse voltage source consists of the DC voltage source labeled Vp and the transistor Ti, the positive pole of which is connected to the collector of the transistor T 1 via a bus G , while the emitter is connected to the bus A 1. to which the individual resistors of the matrix selection elements are connected. The negative pole of the DC voltage source Vp is connected to the AC voltage source 10 (V ₁ ) via the bus line α. According to FIG. 2B, the pulse voltage source is connected to the resistors of the first column via the busbar A 1 and to the resistors of the second column via the busbar A 2 and so on.

The transistors Π are normally non-conductive and are switched to the conductive state by a pulse e> Nes transformer control circuit 20, 21, the voltage on the secondary winding 205 of the transformer 20 occurring at the resistor 21 and via the base-emitter path at the transistor Ti is applied so that it is conductive. In the conducting state of transistor T \ the full pulse voltage of the pulse voltage source across the resistor R 1 is missing at the node N is a low impedance, the voltage increases at the node N of the pulse potential, and is transmitted to the electrode X. The polarity of the diode D1 is such that it represents a low impedance for the pulse voltage source.

In the conduction path between the diode D 1 and the AC voltage source 10, a non-inductive circuit arrangement is provided, which has either a high impedance or a very low impedance, in order to enable the addition of the voltage occurring at node N with the AC voltage that is on the bus / x is supplied. This collecting line is common for the anodes of all diodes D 2 . The function of the diodes D 2 , also referred to as bypass diodes, is explained in DE-PS 21 36 412.

Different circuits can be connected between the collecting line B for the cathodes of all diodes D 1 and the collecting line α, which are shown in FIGS. 3A, 3B, 4 \ and 4B, the circuit of FIG. 3B corresponding to the circuit of FIG.

The anode of the thyristor SCR is connected to the bus line B and the cathode to the bus line λ. A control circuit has a voltage divider with the resistors RA and /? Ss, whose connection point / is connected to the control electrode C of the thyristor. A capacitor C is parallel to the resistor RA.

If the voltage at node N increases when the transistor T \ conducts, the same voltage also begins to grow on the common line and is conducted to the control electrode of the thyristor via the resistor RA and the capacitor C. The small increase in potential is sufficient to turn on the thyristor, so that it is permeable even to strong currents and the voltage at node N does not rise any further, so that there is no increase in voltage at electrode X either. However, so that the voltage occurring at node A / does not drop to zero at the same time as or shortly before (but not after) the switching on of the transistor Ti and therefore cannot be fed to the selected electrode X , a voltage pulse is applied to the control electrode of the thyristor so that it does not become conductive. Since the control electrode of the thyristor is biased by this voltage pulse, the voltage occurring at node N is also applied to the electrode. At this point in time, the voltage occurring at the node N is added to the voltage of the AC voltage source 10. A selection signal will be

in this case via a transformer 25 from a control circuit 90 or 91 (FIG. 2B) of the thyristor circuit supplied, the diode D 3 connected in series with the secondary winding 255 with regard to polarity Keeps unwanted signals away from the control electrode of the thyristor.

All other diodes Dl, the cathodes of which are connected to the bus line B , are biased in a corresponding manner, so that when pulses occur at the resistors R I _1, as already explained, the voltage at the nodes in accordance with the sum of the pulse voltage and the Voltages from the AC voltage source 10 increases in this time interval. The potentials of the alternating voltages could be controlled synchronously with the application of the pulse paper to the transistors T1 or the thyristors SRC , although this is not shown.

Apart from the polarity, the circuit shown in FIG. 3B has the same circuitry as that in FIG. 3A circuit shown. The diodes D 1 and D 2 have reversed polarity and the anode of the thyristor is connected to the bus λ, while the cathode is connected to the anode of the diode D 1.

Instead of the thyristors provided in FIGS. 3A and 3B, the transistors 70 shown in FIGS. 4A and 4B can also be used. F i g. 4A shows a transistor for negative pulse generation and FIG. 4B shows a transistor for positive pulse generation. In FIG. 4A, the emitter of the transistor 70 is connected to the anode of the diode D 1 and the collector is connected to the bus λ. A bias voltage source 71 normally maintains the transistor in a conductive state, with the bias voltage being applied across the secondary winding 25S of the transformer 25 and a small current limiting resistor 72. To select the bus line B , a pulse voltage is applied to the secondary winding 25S as in the circuit according to FIG. 3A induced in order to overcome the bias voltage Vw of the voltage source 71 and to block the transistor 70, so that a high impedance is established at the busbar B and all diodes Dl connected to it, whereby the potential at the node point to that with this connected electrode is guided. Like the circuits with the thyristors, the circuits with the transistors are also reversible, which makes it possible to use NPN transistors. Both types of circuit act as isolated, non-inductive switches. The in the F i g. 5A and 5B shown pulse circuits for negative and positive pulses are also the same circuit, NPN transistors are provided in both circuits, which can also be PNP transistors or mixed transistors in complementary circuits to make the negative and positive voltage pulse generator symmetrical. However, the secondary windings of the transformers are wound or connected in such a way that they supply or induce pulse voltages of the correct polarity which are applied to the base of the transistors in order to render them conductive.

For this purpose 3 sheets of drawings

Claims (3)

Patent claims: 1. Circuit for operating a gas discharge display panel, which has discharge cells delimited by electrodes arranged in rows and columns and provided with dielectric layers, with at least one alternating voltage source for applying an alternating voltage to the row and column electrodes, maintaining the discharge in the discharge cells, with a matrix selection - and addressing circuit with a plurality of addressing circuits for the row and column electrodes for the optional application of a pulse voltage that changes the discharge state of the discharge cells, the addressing circuit having a matrix selection element with two diodes and a resistor for each row or column electrode, which end in a common node, which is connected to one of the row or column electrodes, the pulse voltage source supplying the pulse voltage between the end of the resistor facing away from the node and connected to the output of the AC voltage source, one of the diodes being connected directly between the common node and the output of the AC voltage source, and wherein a semiconductor switch controlled by the matrix selection and addressing circuit is connected between the end of the other diode and the output of the AC voltage source, thereby characterized in that the resistor (Rt) of the matrix selection element (Ru Di, D ₂ ) is connected via the collector / emitter path of a normally non-conductive transistor (Ti) to one output of a DC voltage source (V _P ) , the other output of which is connected to the Output of the AC voltage source (V * 10) is connected, and that for each transistor (Ti) a control circuit (20, 21) of the matrix selection and addressing circuit is provided for its selective activation. 2. A circuit according to claim 1, characterized in that with the row or column electrodes (50, 51) connected addressing circuits of the matrix selection and addressing circuit transistors (Ti) of the same type of NPN. 3. A circuit according to claim 1 or 2, characterized in that the control circuits one Signal transmitter (20) have for low power, the secondary winding (20S ^ on the Base / emitter path of the assigned transistor (Τ,) is connected.