DE19722838C2 - Circuit arrangement for controlled pulse coupling for test purposes - Google Patents

Description

The circuit arrangement according to the invention relates to a circuit arrangement for controlled pulse coupling too Testing purposes according to the preamble of the claim. The circuit arrangement according to the invention is in particular geared to the impulse coupling over DC enable test leads with no risk of Surges caused uncontrolled switching operations become.

According to the known prior art are in the pre-standard Interference immunity standard ENV 50142 VDE V 0843 part 5 dated October 1995 for the coupling of the impulses 10/700 µs and 1.2 / 50 µs surge arrester (ÜSAG) as a possible Coupling variant provided. Overvoltages that occur are derived against mass. Will this span? with a capacitive load for pulse coupling used, uncontrolled switching operations occur, which can lead to the destruction of the test object.

Von Haase "Diodes as Surge Protection" in de / der Master electrician and German electrical trades, de 8/90 p. 553-556 are known protective circuits with diodes, which exclusively on the prevention of overvoltages in the Connection is aligned with a pulse coupling.

From FR 2738682 it is known to use field effect transistors in Use protective circuits against overvoltages.  

DE 341 962 C2 shows the use of field effect transistors in protective circuits. The protection circuits described are also used to protect against overvoltages used.

From "301 circuits", Elektor Verlag GmbH, 1982, 5133 Gangelt 1, page 346 is a backup for surge-sensitive components Protection circuit known. This circuit is too designed exclusively for surge protection.

DE 44 17 129 A1 describes a method and a Device for checking surge protection systems with a surge protector that is on Arc base works. To the one to be checked Surge protection system will be one for the one to be checked Surge protection system sufficient ignition voltage created. After igniting the Surge protection device is the follow current as Evaluation criterion for the functionality of the Surge protection device measured.

A known solution to avoid uncontrolled Switching operations consist of using a bidirectional Zener diode for pulse coupling, such as in VDE 0845 "Protection of telecommunications systems against Lightning strikes, static electricity and surges from high voltage systems "October 1987; part 1 page 17 picture 7 described. With this solution, unwanted occur Voltage jumps not on. But about impulse stability of the Zener diodes with a max. Test voltage of 4 kV and resulting in a maximum current of 160 A a minimum ballast resistance of 25 Ω would have to ensure a zener diode with a power of approx. 100 W can be used. Zener diodes with such  But performance is very expensive and therefore extremely rarely distributed.

The technical task is to create a circuit develop order to be controlled Pulse coupling for testing purposes, and the one Inexpensive alternative to the one described above Zener diode represents. The one to be developed Circuit arrangement should consist of standard components being constructed.

This task is characterized by the Features solved in the claim.

The basic principle of the circuit arrangement according to the invention consists of two field effect transistors T for takeover of the power section of the protective circuit. This makes it possible to switch gears to over-span Protection by two Zener diodes Z lower power realize.

The circuit arrangement according to the invention consists of two interconnected identical circuit components S1 and S2, which are arranged between the connection points A and B of a network. Connection points in the sense of the invention are designed as interfaces, such as S ₀ interface, U _K0 interface or a / b interface. Since both circuit components S1 and S2 are identical, they can be switched on alternately between connection points A and B.

Each circuit component S1, S2 consists of a field effect transistor T, the SOURCE electrode S via a Resistor R with the GATE electrode G and its DRAIN Electrode D via a Zener diode Z with the GATE electrode G connected is. Both circuit components are S1 and S2 via the SOURCE electrodes S of their field effect transistors T connected with each other. The connection of the two Circuit components S1 and S2 existing overall circuit to the connection points A and B of the network always takes place  via the one assigned to the respective connection point A or B. Circuit components S1 and S2, the connection via the drain electrode D of the field effect transistor T each because circuit components S1 and S2 is realized. Since both circuit components S1 and S2 circuit are technically identical, is a swap of the Connection points A and B when connecting the inventions according circuit arrangement to the network radio tionally possible.

The circuit arrangement according to the invention is explained in more detail using an exemplary embodiment. Fig. 1 shows the principle of operation of the circuit arrangement according to the invention.

In FIG. 2, a concrete embodiment is shown, the operation of which is explained below:

The circuit arrangement according to the invention consists of the Circuit components S1 and S2 as described above, the via the SURCE electrodes S of their field effect transistors T1 and T2 are connected to each other.

The field effect transistors T ₁ and T ₂ take over fiction, according to the power section of the protective circuit. They must therefore correspond to this purpose in their dimensioning. For example, field effect transistors of the type BUZ 341 are suitable for use in the circuit arrangement according to the invention. With the resistors R ₁ / R ₂ = 2 kΩ, the voltage in the idle state between the respective GATE electrode G and the SOURCE electrode S is reduced to 0 volts, and the field effect transistor T ₁ is high-resistance.

If a positive voltage of <100 volts is now applied to the network between the connection points A and B, the lower part of the circuit becomes low-resistance due to the action of the protective diode in the field effect transistor T ₂ . The upper part remains high-impedance. The current through the Zener diode Z ₁ is low and thus the field effect transistor T ₁ is not yet activated and remains high-resistance. Only when a voltage of greater than 100 volts is applied to the circuit arrangement does the current in the Zener diode Z ₁ rise rapidly, and the transistor T ₁ becomes conductive due to the voltage drop across the resistor R ₁ .

With a polarity reversal of the circuit, we use the same effect mechanisms on the resistor R ₂ , the Zener diode Z ₂ and the field effect transistor T ₂ .

List of the reference symbols used

1

first circuit component

2nd

second circuit component
A connection point to the network
B Connection point to the network
T field effect transistor
S SOURCE electrode
D DRAIN electrode
G GATE electrode
R resistance
Z zener diode
Components of the first circuit component

1

T ₁

Field effect transistor
R ₁

resistance
Z ₁

Zener diode
Components of the second circuit component

2nd

T ₂

Field effect transistor
R ₂

resistance
Z ₂

Zener diode

Claims (1)

Circuit arrangement for the controlled coupling of pulses for test purposes, the circuit arrangement being arranged between the connection points A and B of a network, characterized in that it is composed of two identical, interchangeable circuit components (S1; S2), each circuit component (S1 ; S2) consists of a field effect transistor (T), the SOURCE electrode (S) via a resistor (R) with the GATE electrode (G) and the DRAIN electrode (D) via a Zener diode (Z) with the GATE Electrode (G) is connected that both circuit components (S1; S2) are connected to each other via the SOURCE electrodes (S) of their field effect transistors (T), and that the connection of the circuit components connected via the SOURCE electrodes (S) ( 1 ; 2 ) to the connection points A and B via the DRAIN electrode (D) of the respective connection point (A; B) assigned field effect transistor (T).