JPS61262027A - Feeder circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] A transistor circuit and a resistor are connected in series, a voltage regulator diode and a photocoupler are connected in parallel to the transistor circuit, and the potential difference between both ends of the power supply circuit is monitored. When the potential difference between the two terminals exceeds the breakdown voltage of the constant voltage diode due to an overcurrent caused by a line fault or the like, the power supply circuit is protected by cutting off the transistor.

[Industrial application field]

The present invention relates to improvements in power supply circuits widely used in the trunks of electronic exchanges.

Generally, in the above-mentioned power supply circuit, there is a strong demand for measures to be able to supply a stable line current and to protect the power supply circuit from abnormalities on the line side, especially overcurrent due to Δ line ground faults and the like.

[Conventional technology]

FIG. 3 is a circuit diagram of a conventional power supply circuit.

In the figure, 1.2 is a transistor, 3 to 7 are resistors, 8.9 is a choke coil, and 10 is a line resistance. Note that the figure shows only the power supply circuit connected to the A line side of the line, and the power supply circuit connected to the B line side is omitted.

In FIG. 3, transistor 1 is normally in a conductive state because the operating voltage is applied, but transistor 2 is in a conductive state.
Since is less than the operating voltage, the line current I is being supplied in a cut-off state. In this case, if a ground fault occurs on the A line side of the line, the current ■ increases, so first the potential difference across the resistor 3 increases, and the potential difference across the resistor 4 also increases, so the transistor 2 changes from the cut-off state to the conductive state. become. Therefore, the potential difference across the resistor 5 applied to the transistor 1 is reduced to less than the operating voltage of the transistor 1, and the transistor I is cut off, so that the current I flows to the resistor 7 side.
Transistor 1 can be protected from damage.

[Problem that the invention seeks to solve]

However, while the line current is small, the power consumption in the resistor 7 is small, but as the line current increases, the power consumption increases, and in that case, the resistor 7 also becomes large.
Therefore, there is a problem that the power supply circuit also becomes large.

[Means for Solving the Problems]] FIG. 1 shows a diagram of the principle of the present invention. In the figure, a voltage regulator diode 15 and a photocoupler 16 are connected in parallel to a power supply circuit in which a transistor circuit 100 and a resistor 3 are connected in series. In this case, the conventional problem can be solved by supplying current through the photocoupler and turning off the transistor.

[Effect]

According to the present invention, the transistors of the transistor circuit are normally used in a saturated state to minimize power consumption, and the A line of the line is connected in series with A'KiA of the line due to an overcurrent due to a ground fault or the like. When the potential difference between the connected transistor circuit and the resistor exceeds the breakdown voltage of the constant voltage diode, the power supply system switches from the transistor to the photocoupler due to the operation of the constant voltage diode. It can be protected without making it large.

〔Example〕

FIG. 2 is a circuit diagram of a power supply circuit according to an embodiment of the present invention.

In the figure, 11 and 12 are resistors, 13 and 14 are transistors, 15 is a constant voltage diode, and 16 is a photocoupler. Note that the same reference numerals indicate the same objects throughout the figures.

In FIG. 2, the normal transistors 13 and 14 are reliably rendered conductive by applying a small operating voltage, and the line current I of line A flows. And most of them are transistors 13.
14 collector current IC flows.

If the A line of the line has a ground fault and the current I increases, the potential difference across the resistor 3 due to the current I also increases, and when the potential difference between ■ and ■ exceeds the breakdown voltage of the constant voltage diode 15, the constant voltage The diode 5 becomes conductive, and at the same time, a current 1F flows through the photocoupler 16, so the photocoupler 16 also becomes conductive.

When the photocoupler 16 becomes conductive, the transistor 1
Since the potential difference between the emitter and base of 3.14 decreases in this case, transistor 13.14 is in a cut-off state, so
Excessive current is prevented from flowing through transistors 13,14.

〔Effect of the invention〕

As described in detail above, according to the present invention, the power supply circuit can be protected by preventing overcurrent from flowing into the power supply circuit by using a constant voltage diode and a photocoupler that are smaller than a resistor.

[Brief explanation of drawings]

Figure 1 is a diagram of the principle of the present invention. FIG. 2 is a circuit diagram of the power supply circuit of the present invention, FIG. 3 is a circuit diagram of a conventional power supply circuit. In the figure, 1.2, 13.14 are transistors, 3~? , 11.12 is resistance, 8.9 is a choke coil, 10 is the line resistance, 15 is a constant voltage diode, 16 is photocabra, 100 indicates a transistor circuit. Enlightenment and moon wandering mouth Early 1 diagram Ba Kaya 2 diagram

Claims (1)

[Claims] A voltage regulator diode (15) and a photocoupler (16) are connected in parallel to a power supply circuit in which a transistor circuit (100) and a resistor (3) are connected in series, and the potential difference between both ends of the power supply circuit is , the voltage regulator diode (
16) A power supply circuit characterized in that when the breakdown voltage exceeds the breakdown voltage of the transistor circuit (100), a power supply current is caused to flow through the photocoupler (16) and the transistor circuit (100) is cut off.