DE2165425A1 - Drive system for electrical discharge devices - Google Patents

Description

Drive system for electrical discharge devices

The invention relates to a drive system for an electrical discharge device, in particular a drive system for a electrical discharge device comprising a pair of opposing electrodes with a dielectric interposed therebetween Material, as well as a formed in the dielectric material, filled with a discharge medium cell.

Reference should first be made to Fig. 1 of the accompanying drawings, in which a basic form of electrical discharge device is shown, which with the novel according to the invention Drive system can be operated; this discharge device 1 includes an insulator plate J3 with a perforation 2, isolator plates 4 and 5 on opposite sides

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Sides of the perforation 2 are arranged, and a pair of opposite Electrodes 6 and 7 which are attached to the outside of the insulator plates 4 and 5. The one through the perforation 2 of the insulator plate 5 and the insulator plates 4 and 5 are formed Cell 8 is filled with an inert discharge medium, for example neon gas, argon gas and the like, and the electrodes 6 and 7 are connected to an alternating current source 9. At least one of the pairs of the insulator plate 4 and the electrode 6 and the insulator plate 5 and the electrode 7 is made of transparent Material made. When a high frequency alternating voltage with a sine waveform as shown 2A is applied from the source 9 to the electrodes 6 and 7, a plasma discharge results in the cell 8 in the vicinity of each peak value of the alternating voltage wave, so that a discharge current consisting of individual peaks results as shown in FIG. 2B. With the device described it is possible by properly selecting the configuration of the cell 8 and arranging a plurality of discharge devices to make the desired pattern of letters, numbers or symbols visible.

The reason for using a high frequency alternating current for generating the glow discharge in the discharge device is the following:

If a direct voltage were applied to the electrodes 6 and 7, luminescence would occur momentarily in the discharge device, but a subsequent discharge would be prevented by the accumulation of positive and negative plasma ions on the inner surfaces of the insulator plates 4 and 5,

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For this reason, a high-frequency alternating voltage is used, as indicated in FIG. 1, in order to remove such plasma ions and thus ensure a continuous discharge. In practice, a high frequency of the order of 20 kHz is preferred in order to achieve a sufficiently high brightness.

The discharge device of the type shown in Fig. 1 requires a breakdown voltage of about 400 V, which is about twice is as big as the conventional gas discharge tubes, for example neon glow lamps and Nixie lamps (trade name). For this reason, various types of drive systems or drive circuits having such able to deliver high breakdown voltage.

In an earlier drive system, shown in FIG a combination of a transistor 10 and a step-up transformer 11 is used. Since it is difficult to find one To procure transistor with a high voltage rating, a transistor with a voltage rating of, for example 10 to 200 V is used, and its output voltage becomes stepped up to the required breakdown voltage of around 400 V. Another prior drive system shown in FIG. 3B is that shown in FIG. 3A The transistor 10 is replaced by an electron tube 12 with a high voltage rating. In Figs. JA and 3B, the reference numerals 13 to 16 resistors and the reference numerals 17 to 19 Capacitors.

In the circuit shown in Fig. 3A it is possible to

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to use a transistor with a low voltage rating and a source with a low terminal voltage, however, by using the step-up transformer prevents miniaturization of the circuit as well as a reduction in price. On the other hand, it is the one shown in Fig. 3B

height

Circuit necessary to use a source that has an operating voltage for the electron tube can deliver. This also prevents miniaturization of the circuit. Moreover, are both the reliability and the service life are unsatisfactory.

The present invention is therefore based on the object of an improved drive system for an electrical discharge device to create that allows the supply voltage to be less than half that of the previous drive systems to reduce the required value. In the drive system according to the invention, neither a step-up transformer nor a Vacuum tube may be required so that it can be made small in size and light in weight. Furthermore, this should Drive system according to the invention have a simple circuit structure and be easy to manufacture. Furthermore, the inventive The drive system must be designed so that it uses solid-state switching elements how transistors and thyristors can work instead of vacuum tubes, so that the reliability and the usable service life can be increased.

According to the present invention, this object is achieved with a drive system for an electrical discharge device, the one formed in an insulator, with a discharge medium

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filled cell and a pair of opposing electrodes on the ■ Having outside of the insulator, with a supply source which has a clamping voltage of predetermined peak value, wherein the drive system is characterized by a differential circuit comprising a pair of switching elements connected to the source has, as well as means for alternately switching the switching means off and on and means for connecting the electrodes the discharge device to the output terminals of the differential circuit, whereby an operating voltage is applied to the electrodes which is twice as large as the terminal voltage of the source.

The switching elements are preferably solid-state semiconductor elements like transistors and thyristors.

The invention is explained in more detail below using exemplary embodiments in conjunction with the drawings, all of which ^! Features that differ from the state of the art can be essential to the invention. Show it:

1 shows a schematic representation of an electrical discharge device in which the drive system according to the invention can be used; \

Figures 2A and 2B are voltage and current waveforms for illustrative purposes the mode of operation of the discharge device shown in FIG. 1;

FIGS. JA and 3B show two embodiments of previous drive systems

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for discharge devices of the type shown in FIG Kind;

4 shows a circuit diagram to explain the operating principle the drive system according to the invention;

Fig. 5 is a detailed circuit diagram corresponding to a Embodiment of the invention;

Figs. 6k to 6g are waveforms for explaining the operation of the embodiment shown in Fig. 5;

Figures 7 and 8 show modifications of the drive circuit shown in Figure 5;

Figs. 9 and 10 show further modifications of the present invention;

Fig. HA to HD input pulse waveforms which are used for effective operation of the embodiment of J \ illustrated in Fig. 9; and

12 shows a block diagram of a typical arrangement of several discharge devices operated from drive systems according to the invention.

According to the circuit diagram shown in Fig. 4 is a discharge device 1 on terminals 24 and 25 of a double-pole changeover switch 23 connected via lines 21 * and 22, the

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Line 22 is grounded. The connections 27, 28 and 26, 29 of the Switches 23 are cross-connected via lines 31 or J52, and terminals 26 and 27 are on via lines 33 and 34, respectively a DC voltage source 35 is connected.

The terminal voltage V of the source 35 is chosen so that it is about half, i.e. 200 V, of the breakdown voltage of the discharge device 1 (although these voltages, depending on the type of the discharge device vary, these values are in the following description).

If the double-pole changeover switch 23 is flipped in the direction of arrow 37, the terminal 2β is connected to the terminal 24, and the terminal 27 to the terminal 25. Accordingly, the charge 21 receives a positive potential of 200 V. On the other hand, if the switch 23 is folded in the direction of arrow 38, the connections between lines 33 * 3 ^ ^and 21, 22 reversed, so that line 21 receives a negative potential of 200V. For this reason, by alternately turning the switch 23, a voltage twice the level of the source voltage, ie a voltage of 400 V, is applied to the discharge device and causes it to light up every time the polarity is reversed. In other words, the discharge device is operated from a direct voltage source of 200 V with an alternating voltage of 400 V, so that a continuous discharge results without interference from the plasma ions. FIG. 5 shows an example of the novel drive system constructed in accordance with the principles discussed in connection with FIG. In this embodiment, the discharge *

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device 1 between the collectors of a pair of NPN- ■ Switching transistors 41 and 42 placed, the emitters of which are connected to ground. The bases of these transistors are connected to input terminals 43 or 44 placed. Furthermore, the collectors are each one. Terminal of a DC voltage source connected via load resistors 45 and 46, respectively.

When a positive input signal is applied to input terminal 4 ^ and at the same time the input terminal 44 is grounded, the transistor 4l is in the ON state and the transistor set to the OFF state. Under these conditions, a terminal 48 of the discharge device 1 is connected to the conductive trane sistor 41 is connected to ground, while the other terminal 49 is supplied with the terminal voltage V (200 V) of the source 35, so that the discharge device lights up momentarily, as has already been described in connection with FIG. 4.

If, on the other hand, a positive input signal is applied to input terminal 44 and terminal 43 is connected to ground, will the transistor 42 is set to the ON state, and the transistor 41 to the OFF state. Thus, the polarity is that of the discharge device applied voltage is reversed and this causes a momentary lighting up again.

The operation of the embodiment shown in FIG. 5 will now be considered in more detail with reference to the waveforms shown in FIG. If pulses of opposite phase, each having a pulse period T and a pulse width T / 2, as shown in FIGS. 6a and 6s> ,

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- ₉ - are given to input terminals 4 ^ and 44 change

• the potentials on output terminals 48 and 49 of the switching transistors 41 and 42 in the manner illustrated by the curves of Figures 6c and 6d. If you use terminal 49 as a reference point understands, the voltage applied to the discharge device 1 changes as shown in Fig. 6E, that is, a pulsating Voltage (400 V) that is twice as large. like the source voltage, is applied to the discharge device. Immediate

; After every polarity reversal there is a momentary discharge in the discharge device, as explained by the curve shown in Fig. 6f, and thus there is a light-up

^: th as shown in Fig. 6g.

Figures 7 and 8 show modified embodiments of the Invention, in which thyristors 141, 142 and field effect transistors 241, 242 instead of those in the embodiment according to FIG used switching transistors 41 and 42 are used.

: Fig. 9 shows a further modification of the present invention,! in which the load resistors 45 and 46 j shown in Fig. 7 are replaced by PNP switching transistors 51 and 52, whose! Emitters are jointly connected to a terminal of the DC voltage source 55. In cases where large currents flow when the transistors 51 and 41 or the transistors 52 and 42 are turned ON at the same time, a small resistor may be provided in series with the transistors 51 and 52. An input terminal 56 connected to the base of the PNP transistor 5I ^; is closed, a pulse is fed that has the same phase position as the pulse that is connected to the base electrode

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j -ιοί of the NPN transistor 4l connected input terminal 43 entered j will. In the same way, pulses with the same phase position are sent via the input terminals 57 and 44 to the bases of the transistors 52 and 42 given.

j When the transistor 4l is in the ON state and the tran- If transistor 42 is in the OFF state, the transistor 51 becomes in the OFF state held while transistor 52 is held ON, I and vice versa. In this way, by replacing the in the

¹ embodiment according to FIG. 5 load resistors used by switching transistors 51 and 52 ensure a more effective switching process, as will be described below: Again in Fig. 5 it is shown that when designating the discharge current that flows in the discharge device 1 when the transistor 41 to 42 in is OFF state, with I ,, the voltage applied to the discharge device 1 by the equation V 'I ₁ R in the oN state and the transistor - I ₁ R _{1 of} g _EDR ü _Ckt be, can R the resistance of the resistor 46 and Rm represent the internal direct current resistance of the transistor 4l. In general, the internal resistance R ₁ ^ can be neglected, since H ^ Rm. The voltage applied to the discharge device 1 then results as V - IR, i.e. at a value smaller than the source voltage V.

If you consider the current I ₂ , which is caused by the resistor 45 \

i flows (this resistor has the same resistance value R as resistor 46 ) _f results in I ₂ = V / R, since transistor 41 is in the ON state and since its internal direct current resistance4

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can be neglected. This current I ₂ does not contribute to the luminous appearance of the discharge device 1, but is only required to keep the terminal 48 of the discharge device at ground potential and represents the power loss in the drive circuit.

In the same way, when the transistor 42 is in the ON state and the transistor 41 is in the OFF state, the potential difference applied to the discharge device results from V-I-zR, where I_ represents the current flowing through the discharge device . The current L · flowing through the resistor 46 is represented by the relationship I ₂ , = V / R. This also stands for the power loss in the drive circuit.

In this way, the resistors 45 and 46 used in the embodiment of Fig. 5 reduce the voltage applied to the discharge device below the source voltage V. Moreover, the currents Ip and I ₁ ,, which do not flow through the discharge device lead to the loss of power and decrease thus the utilization factor of the source. In the embodiment shown in Fig. 9, although the switching transistors 5I and 52 act as a load for the switching transistors 41 and 42, the DC resistance PL ₁ resulting in the conductive state of the transistors 4l and pi or 42 and 52 is negligibly small, as already mentioned above has been mentioned, and it is thus possible to apply a voltage substantially equal to the source voltage V to the discharge device. Further, when the transistor 51 is in the ON state, the transistor 41 is kept in the OFF state and vice versa.

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reverses, so that there is no possibility of a simultaneous conducting state
of both transistors 51 and 41. Accordingly, ¹ does not result from the current I ₂ and I ₂ . according to Fig. 5 corresponding current, and it

is thus a lossless operation of the drive circuit with

I ensured good efficiency. It should be emphasized that all Tran- j

sistors 51, 41, 54 and 44 of the same conductivity type be I. jand can be fed with pulses of the same phase at their bases.

: However, since in reality a small reverse current flows through the transistor even during the period of the OFF state,
it is impossible to reduce the power loss of the drive circuit; Reduce JNull; however, it is possible the loss of performance
to be reduced to 1/100 to 1/1000 of that of the circuit shown in FIG. - _:

'As described above, a drive fre-

; Frequency on the order of 20 kHz or more is used. When a
Drive frequency of 50 kHz is used, the period j T is 20 microseconds, and it is thus necessary to supply the bases of the respective transistors 51, 52, 41 and 42 with pulses having a pulse width of 10 microseconds.

Although with such high drive frequencies switching transistors with
high operating speed are used, the transistors have a more or less long storage time. When feeding the
positive pulses of the same phase to the transistors 51 and
41, the transistor 51 is set in the OFF state, and the
Transistor 41 in the ON state. KLIs however the storage time

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becomes greater than 1/100 of the pulse width (10 microseconds in the example above), transistor 51 may at a time, too every time the transistor 41 is turned ON, not in enter the OFF state. In other words, the transistor 51 remains in during a period corresponding to the storage time Leading state. Under these circumstances, as a result of the leading state!

of the transistor 41, a large current through the transistors 5I and j

41 directed and destroyed them. The same goes for the others:

Transistors 52 and 42.!

In the embodiment shown in Fig. 10, resistors are ^ 53 and 54 with small resistance in the common collector ^

lines of the transistors 51, 41 and 52, 42 inserted so as to j

i prevent excessive currents. j

ίThe excessively large currents can instead be caused by such protective resistors

S ι

) also by slightly modifying the bases of the corresponding. . impulses supplied to the corresponding switching transistors are prevented, in the following way. j

Figures HA, HB, HC and HD show waveforms of input pulses applied to the bases of transistors 51, 41, 52 and 42, respectively. The pulse period is denoted by T, and the ON and OFF times of the respective transistors are _{denoted by 0 * T} and T-, ™. As these transistors are minority carriers

UJM Ui? J?

store, each transistor remains after receiving a control pulse that would otherwise put it in the OFF state, during an interval τ that is slightly greater than the memory time "C ¹ , in the ON state.

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First, consider the operation of transistors 5I and 4l. Since these transistors are controlled by the pulses shown in FIGS. HA and HB, when the pulse supplied to transistor 51 is in state a, that in Pig. HA is present, the pulse applied to transistor 41 in the in Pig. HB, with the result that the transistor 51 is in the ON state, while the transistor 41 is in the OFF state. As shown in Fig. HA, the base of the transistor 51 receives the OFF signal b after receiving the ON signal a during the interval Tqjt due to the storage time, and its collector current becomes zero after t (not shown ). As is represented by a part c of the curve shown in FIG. 11, the base of the transistor 41 is applied with an OFF signal during this time. Only after the expiry of the interval T which is longer than the storage time ¹ C of the transistor 51, a through part of the curve ά of FIG. HB represented ON signal of Bais of the transistor 41 is supplied and this offset in ^the! A condition.

; The operations of transistors 52 and 42 are the same as those of transistors 51 and 41 except that control pulses of opposite phase are applied. That way will by supplying control pulses with conductivity-preventing periods to the corresponding switching transistors the danger eliminates excessive current passages and thus achieves a safe operation of the drive circuit with a high degree of efficiency. Moreover, since it is possible to use the protective resistors 53 shown in FIG. 10, the number of components can be reduced

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- to omit 15 and 54.

To make the switching transistors non-conductive, it's just required to terminate the control pulse applied to the base of any of the switching transistors.

Fig. 12 shows a typical arrangement of a number of discharge devices employing the novel propulsion systems can be. A large number of discharge elements 1 are located therein connected to connection points 48a to 48v and 49a to 49s. The output terminals of the drive systems (not shown) are connected to these connection points. E.g. are the output terminals 48 of a plurality of drive circuits, each of which has the structure shown in FIG. 5, to the connection points 48a to 48v are connected, while the other output terminals 49 are connected to the connection points 49a to 49s are, so that any one of the discharge devices or any combination of several discharge devices for Discharge can be brought.

If one considers the two connection points 48h and 48g for the I case that only the drive circuits connected to these connection points are put into operation while other drive circuits connected to the remaining connection points are connected, are held ineffective, calls the discharge 'device Ic when a predetermined voltage is applied a discharge, while the other discharge devices connected to the same junctions 48h and 49g la, Ib, ld, If, Ig and Ie only receive a voltage that

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is half the predetermined voltage, i.e. only the ■ Terminal voltage of the DC voltage sources so that these other discharge devices do not come to discharge. Naturally the discharge devices connected to other connection points also come not to discharge. Furthermore, the connection point 48g also has the operating voltage applied to it is, the connected discharge devices Ic and Ie to discharge, while the remaining discharge devices do not come to discharge. Accordingly, by selectively starting any one or more of the Connection points 48a to 48v and 49a to 49s connected Drive systems any pattern can be displayed.

In general, the breakdown voltage of discharge devices of the type shown in FIG. 1 varies more or less depending on the frequency of the input signal. For example, in the case of a sinusoidal voltage, the breakdown voltage decreases with increasing frequency. For example, if an insulating plate 3 with a thickness of 0.3 mm and insulating plates 4 and 5 with thicknesses of 0.1 mm each are used and neon gas with a pressure of 200 Torr is used as the discharge medium a breakdown voltage of 400 V pp resulted at a frequency of 50 kHz; when increasing the frequency to 500 kHz this breakdown voltage decreased to 500V. As a result is it when using an input signal with a high proportion of high-frequency components, for example a square wave signal, possible to operate the discharge device with a discharge voltage of only 300 V, even if the pulse repetition frequency for example only 50 kHz, because a high proportion

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the high frequency component of 500 kHz is present. With the new drive system, only half of the discharge voltage is i.e. an input voltage of only 150 V is sufficient. In other words, a discharge device operated with a voltage of 400 V, 50 kHz generated by the earlier drive system can be operated with a source voltage of 150 V. if it is a square wave of 50 kHz generated by the new drive system. It is therefore clear that it is possible with the novel drive system to operate the discharge device with a breakdown voltage that is less than half that of previous drive systems; turned tension.

Overall, the new drive system has the following advantages:

j It is possible to use discharge devices of the type with on the j to bring electrodes attached to the outside of the cell with a source for discharge or glow discharge, their terminal voltage is about half the breakdown voltage of the discharge device. If an operating voltage is used that contains a high proportion of high-frequency components, such as a square wave, it is possible to use the discharge device operate with a source whose terminal voltage is less than half the breakdown voltage, for this reason it is not necessary to use high voltage elements such as vacuum tubes or gas discharge tubes and step-up transformers as in conventional drive systems. Since it is possible to replace these elaborate elements with commercially available plague elements how to replace transistors or thyristors ^ one can be compact

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Manufacture drive systems at a low cost. In addition, the circuit structure of the drive system is simple because a pair of ■ Pest body switching elements operated differentially or alternately will.

Although in the exemplary embodiments described above a DC voltage source was used, it is clear that a source can be used instead, which consists of a AC power source is derived through a half-wave rectifier, or some other source with similar peak values.

It will be appreciated further that, instead of rectangular input signal ^ also input signals can be used by sawtooth or triangular shape _r

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Claims (1)

Claims Drive system for an electrical discharge device, which is formed in an insulator, with a discharge medium having a filled cell and a pair of opposing electrodes on the outside of the insulator, with a source of supply, which has a clamping voltage of predetermined peak value, characterized by a differential circuit which has a pair of switching elements connected to the source, and means for alternately turning it on and off the switching means and means for connecting the electrodes of the discharge device to the output terminals of the differential circuit, whereby an operating voltage is applied to the electrodes that is twice as high as the terminal voltage of the Source. 209831/0607 2165421 2. Drive system according to claim 1, characterized in that j the terminal voltage of the predetermined peak value is approximately equal to half the breakdown voltage of the discharge device. J5. Drive system according to claim 1 or 2, characterized in that that the differential circuit contains a pair of parallel branches, each with a resistor and one connected in series with it Have switching element, wherein the ends of the resistors are common to a terminal of the source and the Connections between the resistors and their associated switching elements to the electrodes of the discharge device are connected. 4. Drive system according to claim J, characterized in that the switching elements have transistors of the same conductivity type, the collectors of which are connected via associated resistors one terminal of the source are connected and their emitters are connected to the other terminal of the source, and that Means are provided for applying repetitive input signals of opposite phase to the bases of the transistors give and thereby to put the transistors alternately in ON and OFF states. 5. Drive system according to claim J5, characterized in that the switching elements of the differential circuit thyristors open! j wise. 209831/0607 2165415 - U- 6. Drive system according to claim J>, characterized in that the switching elements of the differential circuit have field effect transistors. j 7 · Drive system according to claim 1, characterized in that the differential circuit has a pair of branches connected in parallel to the source, each branch having one Has pair of series-connected switching elements, the connections of which to the electrodes of the discharge device device are connected, and that means are provided to; the switching elements alternately in ON and OFF states move in such a way that in one branch the one pole i the source neighboring switching element and in the other branch ■ neighboring the other pole of the source switching element | are placed in the ON state, while the other switching; elements of the branches are switched to the OFF state. ■ ,8th. Drive system according to Claim 7 *, characterized in that the one switching element adjacent to one pole of the source j first and second switching transistors with the same conductivity ! type, of which the emitter to one pole of the Source connected and the bases with input signals opposite Phase can be fed that the other pole of the source adjacent to the other switching elements third and fourth holding transistors have the same conductivity type, of which the emitters are connected to the other pole of the source and the bases with input signals opposite Phase can be charged that the collectors of the in 209831/0607 2165423 Series-connected transistors in each branch are interconnected to form the electrodes of the discharge device connected to the junctions between the collectors of the series-connected transistors of the branches concerned with the first and second transistors adjacent to one pole of the source from the opposite one Conductivity type are like the third and fourth transistors adjacent to the other pole of the source, and that means are provided to the bases of the first and second transistor input signal © eilei ^ l ^ r phase so that the first and vj / -> rt-a ', r uisistor and the second and third transistor are alternately set to ON and OFF states. 9. Drive faa :; .i "em according to claim 8, characterized in that the input signals fed to the transistors concerned have such a relative phase position that one of the Storage time of the respective transistors corresponding conduction blocking period results. j 10.Antriebssystem according to claim J, characterized in that: each of the parallel branches has a current limiting resistor. 11.Antriebssystem according to any one of the preceding claims, characterized characterized in that the supply source comprises a DC voltage source. 209831/0607