DE1094303B - Electronic switch with three and four stable positions - Google Patents

Description

GERMAN

The invention relates to an electronic switch with three and four stable layers, especially as an electronic replacement for a polarized telegraph relay with the middle position of the contact tongue is intended.

A polarized telegraph relay with a center position must correspond to the three possible states "Positive current", "negative current" and "no current" on an incoming line are three stable ones Can take up positions. Even a fully-fledged, electronic equivalent circuit must have these three stable states can reproduce.

A well-known electronic equivalent circuit of a polarized telegraph relay with center position contains three transistors and has three stable layers. Each of the three stable layers is through the Conductive state, of a transistor and the blocking state of the other two transistors.

In contrast, in the electronic changeover switch according to the invention, two become independent bistable flip-flops that can be controlled from one another are used. According to the invention, these two tilting stages are closed connected to a circuit with four stable states, which, when appropriate, preferably pulse-wise Control at the control inputs of the multivibrators positive «or negative or no current outputs a consumer connected to its output. The two characteristic states "positive current" and "negative current" are due to different positions of the flip-flops (a flip-flop in the on-state and a flip-flop in the off-state), the characteristic state "no current" through equal positions of the Tilt stages (both tilt stages in the on or off position) marked.

In an advantageous embodiment, two are each made up of one in a branch circuit lying low-power control transistor and a switching transistor lying in the main circuit higher performance existing bistable multivibrators are used. The two tilt stages are thereby operated in such mutual dependence that not both switching transistors are conductive at the same time are. For the characteristic state "no current", only the position of the two flip-flops is permitted, at which both switching transistors are blocked. Since in this state · only the two control transistors are conductive are, the characteristic state "no current" results in a very low power consumption of the circuit.

In an advantageous embodiment, this mutual dependence of the two »flip-flop stages achieved in that there are control resistors in the main circuit of the switching transistors and the voltage drop at the control resistor located in the main circuit of a conductive switching transistor

Electronic switch
with three and four stable layers

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dr. phil. Abund Wist, Long Island, NY (V. St. Α.),
has been named as the inventor

causes safe blocking of the other switching transistor, preferably by securing the conductive state of its control transistor.

If the changeover switch is to be operated for higher switching voltages than the permissible operating voltage of a holding transistor, several switching transistors can be connected in series in the same direction in a known manner in each of the two main circuits, the switching paths of which are bridged by resistances which are high in relation to the forward resistors ^{1 and low in relation to the blocking resistors} .

The switch according to the invention can be used without capacitors or inductances are built up. This is particularly advantageous because it allows result in very steep edges of the pulses.

Compared to the known circuit arrangement with three transistors, the following advantages result:

1. By using unbalanced flip-flops with a control transistor and a Switching transistor results in a high response sensitivity with a large switching capacity. Around To achieve this with the known circuit arrangement, one would have to use each of the three transistor transistors Connect a control transistor upstream, which increases the cost to six transistors would.

2. The changeover switch according to the invention has in a stable position (both switching transistors blocked) only a very low power consumption.

3. The design of the changeover switch without capacitors results in high switching frequencies and steep pulse edges.
Details of the invention are explained with reference to the drawing.

009 677/337

Fig. 1 shows a bistable multivibrator as it is advantageously used for the construction of the switch according to the invention. If the input terminal al is negative compared to the input terminal bl, the transistor Tl is blocked. At the resistor R5 there is now no reverse voltage for the transistor T3, which makes it conductive. A voltage drop now occurs at resistor R3 which is greater than the voltage drop at resistor R 1 and thus ensures the blocking state of transistor Tl even when there is no blocking voltage at input E 1.

If the terminal al is positive compared to the terminal bl, the transistor Tl becomes conductive. The transistor T 3 is blocked by the voltage drop across the resistor. There is no voltage drop across the resistor RS , so that the transistor Tl remains conductive even when there is no longer any voltage at the input El. Since this circuit does not contain any capacitors, the edges of the emitted pulses are very steep and mainly only influenced by the transistor properties (capacitance; inertia effect). For the same reason, relatively strong changes in the supply voltage do not affect the switching state of this flip-flop circuit until they reach the order of magnitude of the voltages dropping across an open transistor.

FIG. 2 shows an exemplary embodiment according to the invention, which results essentially from the interconnection of two flip-flops according to FIG. 1. Each of the two flip-flops can be controlled at the inputs E1 or E2 in the manner described in FIG. The consumer Rb is connected to output A. The four stable states of the switch are as follows:

1. Transistors T1 and Γ4 conductive, transistors T2 and T3 blocked. In this case, a current flows from point d via consumer Rb, resistors R 13 and R14, transistor T4 and resistor R 16 to the negative battery pole.

2. Transistors T2 and T3 conductive, transistors T1 and T 4 blocked. In this case, a current flows from the positive battery pole via the resistors R3 and i? 4, the transistor T3, the resistor R 6 and the load resistor Rb to the point d.

3. Transistors T1 and T2 conductive, transistors T3 and T4 blocked. In this case, no current flows through the load resistor Rb.

4. Transistors T3 and T4 conductive, transistors T1 and T2 blocked. A current now flows from the positive battery terminal via the resistors R 3 and R 4 of the transistor T 3, the resistors 6, R13 and 14, the transistor T 4 and the resistor R16 to the negative battery terminal. For reasons of symmetry, there is no voltage difference between points c and d, and the load resistance Rb again remains de-energized.

There are two stable positions of the switch available for the "no current" status. However, since only one stable position is required for this characteristic state, it is advisable to select the more favorable of the two stable positions! Since the two transistors T 3 and T4 consume significantly more power than the transistors Tl and T 2, it is advantageous to select the stable position of the switch for the characteristic "no current" state, in which the two transistors T3 and T4 are blocked.

The other state in which the transistors T 3 and T4 are conductive must then be prevented.

Such an embodiment is shown in FIG. In this exemplary embodiment, the two flip-flops are operated in such mutual dependence that the two transistors T3 and T4 cannot be conductive at the same time. If, for example, the transistor T4 is conductive, a negative potential is applied to the base of the via the resistor R2

ίο transistor T1. The transistor Tl becomes conductive as a result and in turn blocks transistor T3. This ensures that the two transistors T3 and T4 cannot be conductive at the same time.

Otherwise, the mode of operation of the circuit arrangement according to FIG. 3 the same as that of the circuit arrangement according to FIG. 2. The one in FIG Stable positions described in points 1 to 3 remain in place.

Fig. 4 shows an embodiment which is suitable for switching voltages which are higher than the permissible operating voltage of one of the transistors in the main circuit. For this purpose, the transistors T3 and T5 or T4 and T6 are in the same direction in series in the two main circuits. The resistors /? 7 and R8 or R17 and R18 are used in a known manner to distribute the reverse voltage evenly. The resistors R 9 and RIO or 7? 19 and R20 are control resistors for the transistors T 5 and T6, respectively. They cause the transistors T5 and T6 to be in the same position as the transistors T 3 and T 4, respectively. Otherwise, the mode of operation of the circuit according to FIG. 4 does not differ from that of the circuit according to FIG. 3.

Of course, the invention includes all obvious modifications and additions to the in Embodiments shown in the figures. For example, other than those shown in FIG. 1 can also be used Flip-flop types can be used. The circuit can also be entirely or partially with complementary transistors or other controllable electronic switching paths.

Claims (6)

Patent claims: 1. Electronic changeover switch using two independently controllable bistable flip-flops, preferably as an equivalent circuit of a polarized telegraph relay with the center position of the contact tongue, characterized in that the two flip-flops are connected to form a circuit with four stable states, which when appropriate, preferably in pulses Control at the control inputs' (£ 1, E 2) of the multivibrator outputs positive or negative or no current to a consumer (Rb) connected to their output (A) . 2. Changeover switch according to claim 1, characterized in that two each of one in one Secondary circuit lying control transistor (Tl, T 2) low power and one in the main circuit lying switching transistor (T3, T4) higher power existing bistable multivibrators be used. 3. Changeover switch according to claim 2, characterized in that the two flip-flops in such mutual dependence operated so that not both switching transistors (T3, T4) at the same time are conductive. 4. Circuit arrangement according to claim 3, characterized in that in the main circuit of the switching transistors (T3, T4) are control resistors (R 13, i? 14) and the voltage drop across the control resistor (R13 or R 14) in the main circuit of a conductive switching transistor (T3 or T 4) ensures that the other switching transistor (T 4 or T3) , preferably by securing the conductive state of its control transistor (T2 or Tl). 5. Circuit arrangement according to claim 2 to 4 for higher switching voltages, characterized shows that in each of the two main circuits several Schakt transistors (T3, T5, T 4, T 6) are in series in the same direction and their switching paths are bridged by resistors (R7, RB, R17, RlS) which are high in relation to the forward resistances and low in relation to the blocking resistors . 6. Circuit arrangement according to claim 2 to 6, characterized in that the circuit except Transistors only contains ohmic resistors. For this purpose, 1 sheet of drawings © 009 677/337 11.60