JPS5818355Y2 - Resistance value switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit for telecommunications equipment, and more particularly to resistance value switching of a DC high current line in which a large DC current flows in a pulsed manner and hardly flows at other times.

Since this type of power supply circuit is often used in common with electronic circuits that handle minute signals, it may be affected by noise from the large current source during times when large pulsed currents are not flowing.

Therefore, it is necessary to provide a reduced P-wave circuit between the DC large current line and the electronic circuit, but it has been difficult to generate an R-wave because the power supply impedance is low.

Therefore, conventionally, such a circuit uses a relay with a large current capacity, and when a large pulsed current flows, the rON
If the load is capacitive, in order to prevent inrush current, switching is performed so that the potential between the contacts is the same in advance by connecting with an appropriate resistance when rOFFJ. There is.

However, when using a relay, there are drawbacks such as a long contact delay time of several milliseconds to several tens of milliseconds, and a limited lifespan depending on the number of times the contacts chatter.

In addition, it is necessary to provide a relay drive circuit that turns the relay ONJ at the timing when a large current is applied and turns OFFJ the relay at the timing when the current stops, taking into account the operation delay time of the contact piece, which has the disadvantage of complicating the circuit. .

The purpose of the present invention is to use the resistance value switching circuit of the present invention in the part of the above power supply circuit where switching is performed using a conventional relay, thereby eliminating the above-mentioned drawbacks and enabling automatic switching by the current flowing through the line. The object of the present invention is to provide a device that does this.

This invention automatically detects changes in the current flowing between the two terminals by installing a bypass consisting of a thyristor and its gate trigger circuit in parallel to the resistor inserted between the terminals in a two-terminal circuit where a DC current flows in a pulsed manner. This is a resistance value switching circuit that functions so that when current flows, it passes through the bypass, and when the current is small, it passes only through the resistor.

The circuit of this invention has an operation delay time of only a few microseconds and is very fast.There is no need for a drive circuit that is required for relay circuits, there is no chattering, there is almost no lifespan depending on the number of operations, and automatic switching is possible. There are some effects that can be achieved.

Next, a resistance value switching circuit according to the present invention will be explained with reference to the drawings.

As shown in FIG. 1, the resistance value switching circuit according to the present invention includes a resistor 3, a thyristor 4, and a capacitor 5, resistors 6, 7, and a Zener diode 8 as a gate trigger circuit for the thyristor between an input terminal and an output terminal 2. configured.

Next, the operation of this circuit will be explained.

However, when current flows through terminals 1 and 2 in a pulsed manner (hereinafter referred to as state A), or when it does not flow (hereinafter referred to as state B).
It is assumed that the holding current of the thyristor 4 is below.

Therefore, the state of this circuit is repeated as follows: B→A→B→A→...

B-) When the voltage reaches A, a voltage drop occurs between terminal 1 and terminal 2 due to resistor 3, and due to the transient characteristics of capacitor 5, a trigger voltage is applied to the gate of thyristor 4, and thyristor 4 becomes conductive, bypassing resistor 3 and causing a current flow. flows.

This is maintained as long as state A continues.

Next, when the state becomes A-)B, the current between the terminals 1 and 2 becomes less than the holding current of the thyristor 4, and the thyristor 4 automatically returns to the non-conducting state.

This is maintained as long as state B continues.

Zener diode 8 is a gate protection circuit for thyristor 4.

In addition, in FIG. 2, the photocoupler 9 is connected to the one in FIG. 1, and when a prohibition signal is applied to the terminal 10 to short-circuit both ends of the resistor 70, the thyristor 4 maintains a non-conducting state even in the state B-+A, and the resistance value does not switch.

If the circuit that provides the prohibition signal is eliminated, the same circuit as in FIG. 1 will be obtained.

Further, FIG. 3 is an example in which two circuits shown in FIG. 2 are provided in series.

Depending on the signals applied to the terminals 11 and 12, it is possible to take four different resistance values in the state B-+A.

According to this circuit, parts that conventionally used relays can be made contactless, and shortcomings of relays such as operating time and chattering life can be improved, while peripheral circuits can be simplified and miniaturized.

Further, by adding an inhibition circuit to the gate trigger circuit and applying an inhibition signal from the outside, it is possible to prevent the resistance value from switching.

Furthermore, it is possible to provide a resistance value switching circuit that connects a plurality of resistance value switching circuits to which the inhibition circuit is added in series or parallel to switch the resistance value depending on how the inhibition signal is applied.

As explained above, the present invention uses a thyristor to create a resistance value switching circuit for high-voltage, large-current circuits by configuring the current to flow in a pulsed manner and simultaneously switching the resistance value at that time. It can be easily implemented in terms of circuitry, and can be made small and lightweight.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram of an embodiment in which a gate/trigger inhibition circuit is added to the circuit shown in Fig. 1, and Fig. 3 is a circuit diagram showing a plurality of circuits of the present invention. FIG. 3 is a circuit diagram showing a block diagram of a case in which the devices are individually connected. 1...Input terminal, 2...Output terminal, 3
...Resistor, 4...Thyristor, 5...
... Capacitor, 6... Resistor, 7...
...Resistor, 8...Zener diode, 9...
. . . Photocoupler, 10 . . . Gate trigger prohibition signal terminal, 11.12 . . . Resistance value switching circuit.

Claims (1)

[Scope of utility model registration request] A resistor connected between two terminals through which a pulsed direct current flows, a thyristor connected in parallel to the resistor, and a gate trigger circuit that makes the thyristor conductive only when the direct current flows between the two terminals. A resistance value switching circuit comprising: