DE1171951B - Electronic switch in which each switching element is formed by means of a bridge consisting of elements that are only conductive in one direction - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: H 03 k

German KL: 21 al - 36/18

Number: 1171 951

File number: C 30069 VIII a / 21 al

Filing date: May 29, 1963

Opening day: June 11, 1964

The invention relates to an electronic switch, which is particularly used for switching from Television signals is determined and suitable, which is also due to signal sources and in which each switching element is formed by means of a bridge consisting of only conductive elements in one current direction.

There are already numerous electronic switching devices for a wide variety of purposes known. Among these circuits, in particular those that have gained in importance use diode bridges, as it is possible to transmit a variable signal, the one Contains direct current component, as is the case, for example, with television signals. With a well-known Embodiment of an electronic switch for two circuit paths are two Diode bridges are used by the two signals to be switched and the switching control signals be applied. When the current sources of the signals to be switched have one pole to ground and these signals change, the switching control signal source must, so that the diode bridges remain balanced be independent of mass. This condition is often addressed by inserting an appropriate one Circuit meets that between the switching control signal source and those of these signals acted upon circuit node of the bridge branch of the bridge a transformer with a symmetrical output owns. However, the use of such a transformer becomes almost impossible, and his Manufacturing costs make the overall circuit completely uneconomical if the control signal is in changes over a very wide frequency range, especially when it reaches high frequencies. This The facts are above all given when using such an electronic switch for television signals. In this case, the electronic switch is located between two or more receiving members and the modulation level.

Although such electronic switches can be used to select a particular circuit, they are primarily intended for the implementation of special effects. In this case, during the transmission of the video signals relating to each line of the final picture, the modulation stage can be made to record, for example , the signals coming from a channel A for a certain part of the line and then those from a channel B , and this for a specific one Number of lines of the actually transmitted image, with the position of the point corresponding to the channel change on a line from line to Electronic switch at which each
Switching device by means of one from only in one
Direction of conductive elements existing
Bridge is formed

Applicant:

Compagnie Frangaise Thomson-Houston, Paris

Representative:

Dipl.-Ing. Dipl. Oec. publ. D. Lewinsky,

Patent attorney,

Munich-Pasing, Agnes-Bernauer-Str. 202

Named as inventor:

Bernard de Thieulloy, Versailles, Seine-et-Oise

(France)

Claimed priority:

France of June 5, 1962 (899 719)

The rest of the line can change. The electronic one used to perform such special effects Switch can be operated in very high cycles. To avoid unpleasant phenomena on the To avoid the transmitted image, it is also important that the duration of the transition from one channel to the other is as short as possible.

The invention is based on the object of providing an electronic switch of the type mentioned at the beginning to create that can avoid the above disadvantages and the above-mentioned requirements enough. In the case of the electronic switch proposed here, this is achieved essentially in that according to the invention, the control voltages of each bridge from one emitting two symmetrical voltages Current source are generated, which a further voltage is superimposed, the value of which is the amplitude of the signal applied to the bridge in question. The control voltage remains symmetrical versus the voltage of the input signal to be switched.

According to a further feature of the invention, the current source supplying symmetrical voltages preferably consists of a symmetrical amplifier to which symmetrical signals V ₀ ± ν are applied and which is in the balanced state, ie when receiving

409 599/271

two identical signals v ₀ , two identical output voltages and output voltages corresponding to that of the signal at the associated bridge.

Here it is of further advantage if, according to the invention, those located on each switch bridge Input signals also hit a circuit element forming a current source of constant voltage, which then retransmits the input signals after a level change, which reach an isolating circuit, the is in series with the power supply circuit provided for the balanced amplifier, which has a resistor connected to the output of the isolating circuit in each of its current paths, the circuit elements of the circuits are dimensioned so that in the balanced state of the symmetrical Amplifier, the voltage drop occurring at the terminals of each resistor mentioned above is equal to the voltage across said circuit element, and finally that with respect to the Level of the signal at the bridge input, symmetrical voltages at the non-common Terminals of said resistors are received.

According to a particularly advantageous embodiment

accordingly their sign via one equipped with conductive elements in only one direction of current Hybrid circuit can be placed on the diagonal branches of one or the other of the two bridges.

In the drawing, an electronic switch of the type proposed according to the invention is in the form of a circuit diagram illustrated on the one hand in its basic principle and on the other hand in two exemplary selected embodiments.

Fig. 1 gives a simplified circuit diagram to explain the basic principle of the operation of the switch proposed here again;

F i g. 2 shows an embodiment of the electronic Switch according to the invention;

Fig. 3 shows a simplified embodiment of the switch proposed here;

F i g. 4 finally shows in diagrams the characteristic curves at various circuit points of the Circuit according to the invention.

On hand F i g. 1 can best explain the operation of the switch according to the invention. In response to applied control signals, this switch leaves those coming from a current source 9

variable video signals E ₁ to an output form of the invention consists of a current source 25 impedance Z transmitted. The current source 9 is a circuit element which forms a counter-constant voltage and is asymmetrical above ground M , to which it is connected to a Zener diode and the associated isolating circuit. The switch now consists of one of the with the load resistors of a diode bridge P ₁ , whose circuit node 2 symmetrical amplifier connected in series and 4 supplied via a resistor R ₁ or R _{2, the} same supply circuit, expediently in a collector value of 6 DC power sources and 7 connected gate-operated transistor, the isolators are identical to each other, but are connected in series with regard to their circuit to the voltage terminal of the load resistors sign. The two level changes of the bridge input signal DC sources 6 and 7 are common to theirs. In this case, the symmetrical junction point 5 at one pole of a chip amplifier advantageously consists of two transistors operated in emitter circuit source 8, the other pole of which is connected to ground M. The individual switch is closed. The circuit node 1 of the bridge P ₁ processing elements are dimensioned so that the signal source 9 is connected to the other pole of the amplifier when there is two mass M on it. The circuit node 3 of the voltages equal to the value v ,, lie at the bridge P ₁ is connected to the output resistance Z connected to each load resistance voltage 40, the other connection also with voltage drop equal to the voltage at the connections mass M in connection stands. As later from the Zener diode. Control voltages applied to the inputs of the balanced amplifier
V ₆ , ± ν then leave on the non-common
Terminals of the load resistors opposite 45 E _{1 is} equal to the mean voltage E ₁ emitted by the current source 9, which occurs at these terminals.
Potential symmetrical potentials appear when
the amplifier is balanced and this potential is the same
is the level of the aforementioned signal.

is set against each other, measures are taken according to the invention that at every moment the voltage supplied by the voltage source 8

The voltage in the circuit point E is equal to E ₁ + V and in the circuit point F is equal to E ₁ - V. The potential difference between the two switching

If the signals to be transmitted have the same amplification points E and F is thus equal to 2 V. The antudes, the level of the reference signal in the direction of application of this voltage is such that the

Diodes d _v d ₂ , d ₃ and d _{i become} permeable. Its on-resistance is extremely low and it poses

the same for each channel, and consequently it is possible to have a single reference signal and a single reference signal Use amplifier to control channel switching.

In terms of the objective of the invention, it also becomes an electronic one with two current paths Proposed switch that has two elements that are conductive in only one direction of current.

55

a current flow / with the value / =

IV

R ₁ + R,

As already mentioned, resistances R ₁ and R " are equal to one another, and the current in each diode is equal to

IiV

- ■ = - ■ · Assuming that the bridge

2 2 K ₁

has armed bridges, which are isolated by a 60 connections 1 and 3, are the ones on them

Resistance at each bridge node of the bridge - occurring voltages equal to E ₁ .

diagonal applied voltage difference V ₁ - V ₂ as already indicated above, the

are fed and the elements are connected so voltage E _{1 of} the voltage source 8 of the voltage

that they are usually current-permeable, which is subject to the current source 9 and is about it

symmetrical amplifier two versus one span 65 equal. These two tensions are therefore equal-

voltage, the value of which corresponds to the amplitude of the to be transmitted to the two bridge connections 1 and 3 of the

the corresponding to the signal lying on a bridge, bridge F _{1 is} applied, which always remains balanced. A

emits symmetrical control voltages, the corresponding from the power source 9 and supplied to the

The variable signal applied to the bridge node 1 is thus completely transmitted to the connection terminals of the impedance Z (output S) . By reversing the pole connections of the current sources 6 and 7, the diodes d _v d ₂ , d ₃ and d _{t of} the bridge P _{1 are} blocked. Since the blocking resistance of these diodes is high, the signals coming from the current source 9 are very strongly attenuated and practically not transmitted to the output S. By changing the polarity of the voltage V applied to the circuit points E and F , it is thus possible _{to block the bridge P 1} or allow it to become permeable, as a result of which the signals originating from the current source 9 can be interrupted or flowed through. By assigning several circuits designed according to the invention, as indicated by the arrows / ^ / ₂ and / ₃ , the signals coming from a particular current source 9 can be applied to the impedance Z as desired.

In Fig. 2 is a circuit diagram illustrating a practical embodiment of an electronic switch according to the invention. Two separate signals, for example video signals E ₁ and E ₂ , are applied to the inputs of the electronic switch according to the invention. Only that part of the switch which corresponds to the circuits that are used for the signal E ₁ will be described below. The mode of operation of the other part for the signal E ₂ is corresponding. The signal E ₁ reaches the switch via the base of an input transistor T ₁ operated in a collector circuit. This transistor serves as an isolating stage, and the signal JE ₁ reaches its emitter with approximately the same level and is then located at the circuit node 1 of the bridge P ₁ . On the other hand, the voltage E _{1 is applied} from this circuit point to the cathode of a Zener diode Z ₁ , the anode of which is connected to the negative pole of the power supply source via a feed resistor R _3. The connection point between the resistor R ₃ and the Zener diode Z ₁ is at the base of a transistor J ₆ . The dynamic resistance of the Zener diode Z ₁ is extremely low compared to its feed resistance R ₃ and the input resistance of the transistor T _6. The changes in the voltage E ₁ are thus transmitted almost completely to the base of the transistor T ₆ and, on the output side, to its emitter at the circuit point A. The transistor T ₆ is in the supply circuit of a symmetrical amplifier formed _{from the transistors T 4} and T _5. The resistors R _i and R ₅ are used as their load resistors. The internal resistances of the collectors of the transistors T ₁ and T- are large compared to the values of the load resistances R ₁ and R _5.

The symmetrical amplifier T ₄ , T ₅ receives signals which are applied to the base electrodes of its transistors in the circuit points C and D. The voltages of the signals in these circuit points are _{symmetrical with respect to a mean value v 0} and can assume two values, namely v ₀ + ν or v ₀ - ν. The amplifier is dimensioned in such a way that the voltage drop occurring at the terminals of the resistors R _i and R ₅ is equal to the ignition voltage of the Zener diode Z ₁ when the two transistors receive _{the voltage v 0 at the same time.} Accordingly, the potentials in the circuit points E and F in this case are equal to the potential of the emitter of the transistor T ₁ , namely E ₁ .

Since the gain of the amplifier T ₄ , T ₅

- the tensions are on

the value ~ ~

the collectors of the transistors J ₄ and T _{5 are} symmetrical with respect to the value E ₁ when the transistors in question receive signals that are symmetrical with respect to the voltage V _0. One of these voltages, namely E ₁ + V, then occurs in the circuit point E and the other, E ₁ - V, in the circuit point F or vice versa, depending on whether the voltages are applied to the transistors.

The node E is located across a resistor R ₁ to the circuit nodes of the bridge 2 P _1; a resistor R _{2 of the} same resistance value connects the circuit point F to the bridge node 4. The circuit point 3 of the BrUCkCP ₁ is connected to the corresponding circuit point of the bridge P ₂ and is also connected to the base electrode of an output transistor T _s .

Since basically the circuit elements in the part of the circuit of FIG. 2 the same as in FIG. 1 and otherwise the same conditions exist, the mode of operation of the switch in FIG. 2 can only be described briefly. If the control signals with the values v ₀ + ν and v _e - ν are applied at C and D , the voltages occurring at the switching points E and F are equal to JB ₁ '- V and E ₁ + V, respectively. These two voltages are then applied to the bridge node 2 via the resistor A ₁ and to the circuit node 4 of the bridge P ₁ via the resistor R ₂ . The potential difference applied to the bridge branch 2-4 then has the value 2 V. Its direction of application is such that the diodes d ₁ to d _{i forming the bridge P 1} are blocked. This applies under the condition that the voltage occurring in the node G _{connecting the bridges P 1} and P ₂ , assuming that the bridge P ₂ is open at the moment in question, is between the values E ₁ −V and E ₁ + V lies. Namely, when the amplitude of the transmitted to node G, and thus to the circuit node 3 of the bridge P ₁ signal E ₂ is less than S ₁ '- V, the diode is d _i of the bridge arm 2-3 conductive, and it turns a current between the bridge connections 2 and 3; if this voltage is greater than E ₁ + V , the diode d _{3 of} the bridge arm 3-4 becomes conductive, and a current flows between the connections 3 and 4 of the bridge P ₁ . In these two cases, the balancing of the bridge P _{1 is} destroyed, and part of the voltage of the signal E ₁ passes through. Since measures have been taken to ensure that the above-mentioned condition is met, the blocking resistance of the diodes d _v d ₂ , d _s and d _{t of} the bridge P _{1 is} high, and the signal E ₁ is not transmitted to the node G.

By reversing the direction of application of the control signal, the voltage in node C becomes v _o - v and that in node D becomes V ₀ + v, while the voltage in node E becomes E ₁ + V and the voltage in node F becomes E ₁ - V will. In this case, the four diodes of the bridge P _{1 are} conductive and give each

a stream ^ _n - from when R _{1 is} equal to R ₂ . you

Forward resistance is thus low and the signal E ₁ is transmitted to node G. Since the control signal is applied to both inputs simultaneously

gene of the symmetrical amplifier T ₇ , T ₈ controlling the state of the bridge P ₂ is reversed, the bridge P _{2 is in} turn blocked. The input resistance of the transistor T ₃ operated in the collector circuit is very large. In the circuit point S thus finally occurs a signal V _0, the amplitude of which comes very close to the signal E ₁ as F i g. 4 can be found.

The operation of the voltage applied to the channel of the signal E ₂ P bridge ₂ and its associated circuits, such as the Zener diode Z _2, of the transistor T ₉ and T ₇ of the balanced amplifier, T ₆ corresponds to that which has just been described. Since the forward direction of the diodes of the bridge P ₂ is reversed compared to the bridge P ₁ , the control signals v ₀ + ν and v ₀ - v, which lead to the blocking of the bridge P _{1 of} the channel of the signal E ₁ , effect the conductivity of the bridge P. ₂ , and vice versa. By simultaneously applying the control signal voltage of the appropriate polarity and appropriate value to the inputs of the balanced amplifiers T ₄ , T ₅ and T ₇ , T ₆ , the states of the bridge P ₁ and P ₂ are opposed to each other, and only one of the signals E ₁ and E ₂ can flow through the circuit that has become permeable and reach output 5. This circuit thus fulfills its function as an electronic switch.

The circuit described above can, however, also be implemented in a simplified manner according to FIG. 3 are executed. The adjustment of the control signals for the switchover is particularly important when the levels of the signals to be transmitted at the inputs E ₁ and £. It is therefore sufficient to use a single symmetrical switching signal amplifier in order to supply the two bridges in accordance with the above mode of operation, as is the case with the circuit in FIG. 3 is given. _{The symmetrical amplifier T 4} , T ₅ , which receives the switching control signal at its inputs C and D, emits voltages with previously defined values E ₁ ± V at its output £ and F. The potential difference between the circuit points E and F is applied simultaneously to the two bridges P ₁ and P ₂ , via decoupling diodes D ₁ to D ₄ , which are connected in such a way that one is blocked when the other is conductive, and vice versa . These decoupling diodes are therefore switched in opposite directions.

Each bridge is usually fed by a potential difference V ₁ - V ₂ , which is applied to it via feed resistors R ₁ , R ₂ or R ₁ , R / . As can be seen from the circuit of FIG. 3, the circuit direction of the diodes of these bridges is such that they become _{conductive when the aforementioned potential differences F 1} - V ₂ are applied. The task of the symmetrical amplifier T ₄ , T ₅ is to apply blocking potentials to the diagonal branches of one or the other bridge via the decoupling diodes D ₁ , D ₂ or D ₃ , D _{4 in} accordance with the direction in which the control signals are applied to the Terminals C and D to be supplied. For example, if the control voltage in node C has the value V ₀ + ν and in node D 6g has the value V ₀ - ν, the voltages in nodes E and F are E ₁ - V and E ₁ 4 - V, respectively, like this already in connection with FIG. 2 has been declared. Under these conditions, the diodes D ₂ and D _{1 are applied} in the forward direction, and a potential difference 2Vm is applied to the bridge diagonal 2-4 of the bridge P _{1 in} such a direction that the diodes of this bridge are blocked, which the transmission of the signal E. ₁ prevents. In contrast, the diodes D ₄ and D _{3 are} blocked with the proviso that the voltage E _{2 is} between E ₁ −V and E ₁ + V; the diodes of the bridge P ₂ remain conductive and the signal E ₂ is transmitted to the output. As already in connection with F i g. 2, the level of the voltage E ₁ transmitted to the nodes E and F is used indifferently in the case of the transmission of the signal E ₁ or E _2; the risk of the signal E _{1 being} mixed with the signal E ₂ is avoided by the diode pairs D ₁ , D ₂ and D ₃ and D ₄ . If the polarity of the control voltage applied to circuit points C and D is _{reversed, bridge P 2 is} blocked and bridge P _{1 is} conductive, and only signal E ₁ is then transmitted to output S.

The control connection points of each bridge are only given a fixed potential if the control signal is applied in the forward direction of the respective diode pair D ₂ , D ₁ or D ₃ , D ₄ . It is therefore important to fix their potential in the absence of the control signal. For this purpose, the mentioned bridge connections are connected via resistors R ₁ and R ₀ or A ₁ 'and R. /, which are connected to two circuit points "fixed potential + V ₁ and - V ₂ ," in the forward direction of the four diodes of each bridge P ₁ and P. These voltages + V ₁ and -F. Are chosen to be large compared to the voltage of the signal E ₁ so that the current in the diodes of the bridge is practically independent of this signal. The resistors R _v R ₂ and R ₁ , R ₂ are chosen so that the currents continuously flowing through the four diodes are approximately equal to each other, thus obtaining a simplified electronic switch according to the invention.

Even if the electronic switch according to the invention is only based on its application above the transmission of television signals are described, they are, however, applicable in all cases, in which the switching voltage remains symmetrical with respect to the value of the voltage to be switched got to.

Claims (5)

Patent claims: 1. Electronic switch, in particular for switching television signals, which is connected to signal sources and in which each switching element is formed by means of a bridge consisting of only one-way conductive elements, characterized in that the control voltages of each bridge (P ₁ ) from a two symmetrical Voltages (V) emitting current source are generated, on which a further voltage (E ₁ ) is superimposed, the value of which _{corresponds to the amplitude (E 1} ) of the signal applied to the bridge in question. 2. Switch according to claim 1, characterized in that the supplying symmetrical voltages Power source from one of symmetrical Signals (v ₀ ± v) applied symmetrical amplifier (Γ ₄ , T ₅ ; T ₇ , T ₈ ) exists, which in the balanced state, ie when receiving two identical signals (v ₀ ), two identical and the one at the associated bridge (P ₁ , P ₂ ) lying signal (E ₁ ', E ₂ ) emits corresponding output voltages. 3. Switch according to claim 2, characterized in that the input signals (E ₁ ', E ₂ ') _{lying on each switch bridge (P 1} , P ₂ ) also meet a circuit element (Z ₁ , Z ₂ ) forming a current source of constant voltage , which then retransmits the input signals after the level change, which reach an isolating circuit (T ₆ , T ₉ ) which is in series with the power supply circuit provided for the symmetrical amplifier (T ₄ , T ₅ ; T ₁ , T _s ) , which in each of its current paths has a resistor (i? ₄ , R ₅ ) connected to the output of the isolating circuit, furthermore the circuit elements of the circuits are dimensioned in such a way that in the balanced state of the balanced amplifier the voltage at the terminals of each resistor (i? ₄ , R ₅ ) The voltage drop that occurs is equal to the voltage at the circuit element (Z ₁ , Z ₂ ) mentioned, and finally the voltages at the non-common terminals, which are symmetrical with respect to the level of the signal at the bridge input (E, F) of the mentioned resistances (i? ₄ , R ₅ ) . 4. Switch according to claim 3, characterized in that the circuit _{element forming a current source of constant voltage (Z 1} , Z ₂ ) consists of a Zener diode and the associated isolating circuit (T ₆ , Tg) consists of one of the load resistors (A ₄ , R ₅ ) there is a series-connected supply circuit supplied transistor, the isolating circuit transmitting the level changes of the bridge input signal (E ₁ , E ₂ ') to the voltage terminal of the load resistors. 5. Double way switch with switches according to one of claims 2 to 4, characterized by two bridges (P ₁ , P _{2 ) equipped with conductive elements in only one current direction (J 1} to <i ₄ ), which are connected by a resistor (R ₁ , R ₂ and R ₁ , R ₂ ) at each bridge node on the bridge diagonal (V ₁ - V ₂ ) are fed and their elements are connected in such a way that they are usually current-permeable, with the symmetrical amplifier (Γ ₄ , T ₅ ) two opposite a voltage the value of the amplitude of the to be transmitted, on the lying a bridge signal (e _1, e _2), emits symmetrical control voltages according to their sign over one with only conductive in a direction of the current elements (D _1, D ₂ and D ₃ , D ₄ ) equipped hybrid circuit to the diagonal branches of one (P ₁ ) or the other (P ₂ ) of the two bridges. 1 sheet of drawings 409 599/271 6.64 © Bundesdruckerei Berlin