JPH09322384A - Leak breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute the DC power supply circuit of a leak breaker, which can correspond to the rated voltage in the wide range of a main circuit by using the less number of parts. SOLUTION: The AC power supply voltage flowing through a main circuit 1 undergoes full-wave retification by a rectifier circuit 6 of a DC power supply circuit 23, and the voltage is applied on the collector of a voltage dropping transistor 20. The applied voltage is also applied to a constant-voltage diode 21 connected to the base of the voltage dropping transistor 20. Thus, the voltage is dropped. At the same time, the voltage dropping transistor 20 is set in the on-state, and a load current (emitter current) IL is made to flow. The DC power supply Vd smoothed by a smoothing capacitor 12 is supplied to a leak detecting circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage breaker for detecting an earth leakage of a main circuit for supplying an AC power source to a load and opening a main circuit contact provided in the main circuit.

[0002]

2. Description of the Related Art In such a conventional earth leakage breaker, a DC power supply circuit for supplying an operation power supply to a built-in earth leakage detection circuit or the like is generally constructed from an AC power supply of a main circuit. At that time, various circuit systems are used in order to step down the rated voltage of the main circuit to an appropriate level as an operating power supply. For example, as disclosed in Japanese Examined Patent Publication No. 7-57062, a plurality of parallel circuits of a Zener diode and a constant current diode are connected in series to a DC power supply circuit of an earth leakage breaker of a rated voltage shared type. There is a device which can cope with a wide range of rated voltage by inserting a current control circuit.

An example of this earth leakage circuit breaker is shown in FIG. In FIG. 4 showing an electrical configuration, the main circuit 1 is composed of three power supply lines A, B and C (A, B and C phases), and the power supply side terminals 2a, 2b and 2c are connected to the input side and output. Load side terminals 3a, 3b and 3c are provided on the side. This main circuit 1 has a main circuit contact 5 that can be separated by a trip coil 4.
Is provided.

The power supply lines A and C on the load side of the main circuit contact 5 are connected to an input terminal of a rectifying circuit 6 composed of bridge-connected diodes. Between the positive and negative output terminals of the rectifier circuit 6, the trip coil 4
And a series circuit of thyristors 7 is connected.

A circuit 10a in which a constant voltage diode 8 and a constant current diode 9 are connected in parallel so as to have polarities opposite to each other is defined as one stage, and a plurality of such circuits, for example, five stages, are connected in series as a current limiting circuit 10. It is configured. The input side terminal 10b (cathode side of the constant voltage diode 8) of the current limiting circuit 10 is connected to the positive side output terminal of the rectifier circuit 6, and the output side terminal 10c (anode side of the constant voltage diode 8) is It is connected to the negative output terminal of the rectifier circuit 6 via the constant voltage diode 11. A smoothing capacitor 12 is connected in parallel to the constant voltage diode 11.

The rectifying circuit 6, the current limiting circuit 10, the constant voltage diode 11 and the smoothing capacitor 12 constitute a DC power supply circuit 13. Then, the current limiting circuit 10
The output side terminal 10c and the negative side output terminal of the rectifier circuit 6 are
It is connected to the power input terminal of the leakage detection circuit 14.

The main circuit 1 is provided with a zero-phase current transformer 15, and the output terminal of the zero-phase current transformer 15 is connected to the input terminal of the leakage detection circuit 14. A current-voltage converting resistor 16 is connected between the output terminals of the zero-phase current transformer 15. The leakage detection circuit 14 detects a zero-phase current (converted into a voltage by the resistor 16) and a set value, which are detected by the zero-phase current transformer 15 collectively collecting the A, B and C phase currents flowing in the main circuit 1. Differential amplification is used to detect leakage.

The output terminal of the leakage detection circuit 14 is
The leakage detection circuit 14, which is connected to the gate of the thyristor 7, supplies a control signal to the gate of the thyristor 7 to energize the trip coil 4 when the leakage is detected.
The main circuit contact 5 is opened. The above-mentioned electrical components are housed in a case (not shown), so that an earth leakage breaker is configured.

Here, consider a case where a DC voltage E is applied across both ends of a set of parallel circuits 10a constituting the current limiting circuit 10 of the DC power supply circuit 13 to gradually increase from zero potential. First, a current starts to flow in the constant current diode 9,
Lower limit voltage V that reaches the rated current Is of the constant current diode 9
Up to 1, the current also rises in proportion to the rise of the applied voltage E, and when it reaches the rated current Is, after that, a constant rated current Is flows regardless of the rise of the applied voltage E. When the applied voltage E further rises and reaches the rated voltage (Zener voltage) Vz of the constant voltage diode 8, the current Iz also starts flowing in the constant voltage diode 8.

Therefore, the parallel circuit 10a having such a structure is
When the voltage E is applied to the current limiting circuit 10 connected in series, it is possible to maintain the current flowing through the current limiting circuit 10 at a constant current value Is within the range of the applied voltage E from 5V1 to 5Vz. Become.

That is, the DC power supply circuit 1 having the above configuration
In the earth leakage circuit breaker having 3, the number of connection stages of the parallel circuit 10a can be increased according to the height of the AC voltage supplied from the main circuit 1 to reduce the operating voltage to the earth leakage detection circuit 14. It is like this.

[0012]

However, in general, the rated voltage of the main circuit 1 is 100 V from the single-phase AC power supply voltage (two power supply lines in this case) to the three-phase AC power supply voltage 41.
In the earth leakage breaker of the common rated voltage type, which has a wide range of up to 5 V and is intended to be used also for such a rated voltage that changes over a wide range, when the rated voltage of the main circuit 1 is high, In the DC power supply circuit 13 having the above-mentioned configuration, the number of connection stages of the parallel circuit 10a increases, so that the number of parts increases and the empty space inside the case of the earth leakage breaker cannot be effectively used.

Further, in the above structure, the constant current diode 9 is used regardless of the magnitude of the current consumption of the leakage detection circuit 14 itself.
Since a current equal to the rated current Is of the DC leakage current is constantly flowing, the circuit loss of the DC power supply circuit 13 increases, and the temperature inside the case of the earth leakage breaker rises due to the circuit loss. There was a problem of leading to a decrease.

The present invention solves the above-mentioned problems.
It is an object of the present invention to provide an earth leakage circuit breaker capable of constructing a DC power supply circuit corresponding to a wide range of rated voltage of a main circuit with a smaller number of parts.

[0015]

To achieve the above object, an earth leakage circuit breaker according to claim 1 comprises a main circuit contact provided in a main circuit for supplying an AC power supply to a load and an AC power supply of the main circuit. A DC power supply comprising a DC power supply circuit for creating a DC power supply and a DC power supply from this DC power supply circuit, and an earth leakage detection circuit that opens the main circuit contacts when a leakage of the main circuit is detected. The circuit is composed of a rectifier circuit for rectifying the AC power supply of the main circuit, an NPN type step-down transistor whose collector is connected to the positive side output terminal of the rectifier circuit, and a connection between the collector and base of the step-down transistor. The base resistance, the Zener diode connected between the base of the step-down transistor and the negative side output terminal of the rectifier circuit, the emitter of the step-down transistor and the negative side output terminal of the rectifier circuit. Characterized in that a smoothing capacitor connected between the.

According to this structure, by appropriately selecting the resistance value of the base resistor, it is possible to supply a current in accordance with the current consumption of the leakage detection circuit, and by appropriately selecting the Zener diodes having different Zener voltages. It can easily support a wide range of rated voltages of the main circuit.

In this case, the DC power supply circuit has a base for the current detection resistor whose one end is connected to the emitter of the step-down transistor and whose other end is connected to the positive terminal of the smoothing capacitor, and the emitter and base of the step-down transistor. And a current limiting transistor whose collector is connected and whose emitter is connected to a common connection point of the current detecting resistor and the smoothing capacitor. If such a configuration is adopted, a short circuit or the like on the load side may occur. Even if the current flowing in the DC power supply circuit, that is, the emitter current of the step-down transistor increases, the terminal voltage of the current detection resistor rises and the current-limiting transistor turns on, causing the base current of the step-down transistor to be shunted. Thus, the emitter current can be suppressed to a predetermined upper limit value (claim 2).

In the DC power supply circuit, the ground terminal is connected to the negative output terminal of the rectifier circuit, the input terminal is connected to the emitter of the step-down transistor or the emitter of the current limiting transistor, and the output terminal is the output-side smoothing capacitor. It is preferable to have a configuration including a three-terminal regulator connected to the positive-side terminal of the above. With such a configuration, it is possible to further reduce the ripple of the DC power supply voltage applied to the leakage detection circuit via the three-terminal regulator. Yes (Claim 3).

Further, the DC power supply circuit may be provided with a smoothing capacitor which is connected between the positive and negative output terminals of the rectifier circuit in the preceding stage of the step-down transistor. Then, the load current can be stably supplied to the smoothing capacitor in the output stage (claim 4).

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. Note that the same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, the current limiting circuit 10 and the constant voltage diode 11 are removed from the DC power supply circuit 13 shown in FIG. The collector of an NPN step-down transistor 20 is connected to the positive output terminal of the rectifier circuit 6, and the base of the step-down transistor 20 is rectified by a rectifier circuit (Zener diode) 21. 6 is connected to the negative output terminal.

A base resistor 22 is connected between the collector and the base of the step-down transistor 20, and the positive terminal of the smoothing capacitor 12 is connected to its emitter. The above constitutes the DC power supply circuit 23, and the others are configured similarly to those shown in FIG.

Next, the operation of the first embodiment will be described. The rectifier circuit 6 full-wave rectifies the AC power supply voltage of the main circuit 1 and applies a pulsating DC voltage having a peak value of the AC power supply voltage to the collector of the step-down transistor 20. When a voltage is applied to the collector of the step-down transistor 20, a current Iz flows through the constant voltage diode 21 through the base resistor 22 (current is indicated by IR), and its terminal voltage holds the Zener voltage Vz. Then, the base potential IB flows from the base to the emitter because the base potential of the step-down transistor 20 rises. Then, the step-down transistor 20 is turned on, the collector current Ic1 proportional to the DC current amplification factor flows, and the load current (emitter current) IL obtained by adding the base current IB to the collector current Ic1 flows to smooth the current. The DC power source smoothed by the capacitor 12 is supplied to the leakage detection circuit 14.

At this time, the DC power supply voltage Vd supplied to the leakage detection circuit 14 becomes a value obtained by subtracting the base-emitter voltage VBE1 of the step-down transistor 20 from the zener voltage Vz, that is, Vd = Vz-VBE1. Voltage V
By appropriately selecting the constant voltage diode 21 having an appropriate value as z, it is possible to reduce the voltage so as to obtain an appropriate DC voltage. Further, if the current IB is suppressed by setting the resistance value of the base resistor 22 to an appropriate value and the current Iz flowing through the constant voltage diode 21 is suppressed, the DC power supply circuit 23 is prevented from consuming excessive current. It can be prevented.

The earth leakage detection circuit 14 operates by being supplied with the DC power supply Vd produced as described above from the DC power supply circuit 23, and refers to the zero-phase current from the zero-phase current transformer 15 to perform main operation. When the leakage of the circuit 1 is detected, a control signal is applied to the gate of the thyristor 7 to energize the trip coil 4 to open the main circuit contact 5.

As described above, according to this embodiment, the main circuit 1
The AC power supply voltage is full-wave rectified by the rectifier circuit 6 of the DC power supply circuit 23 and applied to the collector of the step-down transistor 20, and the applied voltage is connected to the base of the step-down transistor 20 via the base resistor 22. By applying the voltage to the constant voltage diode 21 as well, the voltage is stepped down, the step-down transistor 20 is turned on, the load current (emitter current) IL is passed, and the DC power supply Vd smoothed by the smoothing capacitor 12 is supplied to the leakage detection circuit 14. I did it.

Therefore, even when the AC power supply voltage of the main circuit 1 is high, the DC power supply circuit 23 having a smaller number of components than the conventional one supplies a voltage suitable for supplying to the leakage detection circuit 14. A DC power supply Vd can be created. Therefore, the vacant space in the case can be effectively used without increasing the size of the DC power supply circuit 23. Further, the DC power supply circuit 23 does not significantly exceed the level of the current required for the leakage detection circuit 14 to operate and consume the current transiently, so that it is possible to prevent the deterioration of the performance and the shortening of the life. it can.

FIG. 2 shows a second embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. In FIG. 2 showing the electrical configuration of the main part, a smoothing capacitor 24 is connected to the positive and negative output terminals of the rectifier circuit 6 in the preceding stage of the step-down transistor 20.

A current detecting resistor 25 is provided between the emitter of the step-down transistor 20 and the smoothing capacitor 12.
Is inserted, the base of the current limiting transistor 26 is connected to a common connection point of the current detecting resistor 25 and the emitter of the step-down transistor 20, and the current detecting resistor 25 and the smoothing capacitor 12 are commonly connected. NPN at the point
The emitter of a current limiting transistor 26 of the shape is connected. The collector of the current limiting transistor 26 is connected to the base of the step-down transistor 20. The above is the configuration of the DC power supply circuit 27, and the other configurations are similar to those of FIG.

Next, the operation of the second embodiment will be described. In the normal operation, the smoothing capacitor 24 provided on the collector side of the step-down transistor 20 ensures a stable load current I to the smoothing capacitor 12 in the output stage.
L can be supplied.

Now, let us consider a case where the load current IL suddenly rises due to a short circuit of the load for some reason. In this case, the terminal voltage of the current detecting resistor 25 rises in accordance with the increase of the load current IL, and when it reaches the minimum operating voltage of the current limiting transistor 26, that is, the base-emitter voltage VBE2, the current limiting transistor 26 is reached. Is turned on.

Then, the collector current Ic2 of the current limiting transistor 26 flows, and this collector current Ic2 is
Since the current IR that flows into the base of the step-down transistor 20 is shunted, the base current IB of the step-down transistor 20 does not flow any more. Therefore, the terminal voltage of the current detecting resistor 25 is the base-emitter voltage VBE2.
Assuming that the value of the load current IL at the time of reaching is ILIM, the load current will not exceed the upper limit value ILIM.

As described above, according to the second embodiment, when the DC power supply circuit 27 is provided with the current detecting resistor 25 on the emitter side of the step-down transistor 20, the load current IL is suddenly increased. When the terminal voltage of the current detecting resistor 25 reaches the voltage VBE2, the current limiting transistor 26 is turned on, and by suppressing further increase of the base current IB of the step-down transistor 20, the load current IL is reduced. I tried to suppress it to the upper limit value ILIM.

Therefore, even if a short circuit occurs on the load side, the load current IL does not exceed the upper limit value ILIM, so that the overcurrent causes the junction temperature of the step-down transistor 20 to exceed the operating temperature range and be damaged. Can be prevented.

FIG. 3 shows a third embodiment of the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. 3, the smoothing capacitor 24 is removed from the collector side of the step-down transistor 20 in FIG.

The input terminal of the three-terminal regulator 28 is connected to the emitter of the current limiting transistor 26, and the output terminal is connected to the positive terminal of the smoothing capacitor 12. The ground terminal of the three-terminal regulator 28 is connected to the negative output terminal of the rectifier circuit 6.
The other configuration is the same as that of FIG. 2, and the above constitutes the DC power supply circuit 29. The rated output voltage of the three-terminal regulator 28 is, for example, 5V.

According to the third embodiment configured as described above, the DC voltage output from the emitter of the step-down transistor 20 via the current detecting resistor 25 is further 5V via the three-terminal regulator 28. Since the DC power supply voltage is output after being stabilized, the stabilized DC power supply with even smaller ripples can be supplied to the leakage detection circuit 14.

The present invention is not limited to the embodiments described above and shown in the drawings, but the following modifications or expansions are possible. Also in the first and third embodiments, the smoothing capacitor 24 may be provided on the collector side of the step-down transistor 20. With such a configuration, a stable load current IL can be supplied to the smoothing capacitor 12. it can. Also, in the first embodiment, as in the third embodiment, the step-down transistor 20 may be provided with the three-terminal regulator 28 on the emitter side. With such a configuration, the ripple is further reduced and the stability is improved. It is possible to obtain an integrated DC power supply.

In the second embodiment, the smoothing capacitor 24
The number of parts can be reduced by adopting such a configuration. The rated output voltage of the three-terminal regulator 28 is not limited to 5V, and the leakage detection circuit 14
It may be changed as appropriate according to the operating voltage.

[0039]

Since the present invention is as described above,
The following effects are obtained. According to the earth leakage breaker of claim 1, the AC power supply voltage of the main circuit is full-wave rectified by the rectifier circuit and applied to the collector of the step-down transistor, and the applied voltage is applied to the constant voltage diode via the base resistor. The voltage is reduced by applying the voltage, and the step-down transistor is turned on to allow the load current to flow to supply the DC power supply to the leakage detection circuit.Therefore, even if the AC power supply voltage of the main circuit is high, Then, with the DC power supply circuit configured with a smaller number of parts, it is possible to create a DC power supply with an appropriate voltage to supply to the earth leakage detection circuit, use the empty space inside, and reduce the performance and life. Can be prevented.

According to the earth leakage breaker of the second aspect, the current detecting resistor is provided on the emitter side of the step-down transistor, and when the load current is about to increase suddenly, the terminal voltage of the current detecting resistor is increased. The current limiting transistor is turned on when it reaches a predetermined value, so even if a short circuit occurs on the load side, the increase in the load current is also suppressed by suppressing the further increase in the base current of the step-down transistor. Therefore, it is possible to prevent the step-down transistor from being damaged.

According to the earth leakage breaker of the third aspect, the DC voltage output from the emitter of the step-down transistor via the current detecting resistor is further stabilized and output via the three-terminal regulator. Therefore, it is possible to supply the stabilized DC power supply with less ripples to the leakage detection circuit.

According to the earth leakage breaker of the fourth aspect, since the smoothing capacitor is provided in the preceding stage of the step-down transistor, it is possible to supply a stable load current to the smoothing capacitor in the output stage.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a main part of an electrical configuration in a second embodiment of the present invention.

FIG. 3 is a diagram corresponding to FIG. 2 in a third embodiment of the present invention.

FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional technique.

[Explanation of symbols]

1 is a main circuit, 5 is a main circuit contact, 6 is a rectifier circuit, 12 is a smoothing capacitor, 14 is a leakage detection circuit, 20 is a step-down transistor, 21 is a constant voltage diode (zener diode), 22 is a base resistor, and 23 is A DC power supply circuit, 24 is a capacitor, 25 is a current detection resistor, 26 is a current limiting transistor, 27 is a DC power supply circuit, 28 is a three-terminal regulator, and 29 is a DC power supply circuit.

Claims (4)

[Claims] 1. A main circuit contact provided in a main circuit for supplying an AC power supply to a load, a DC power supply circuit for producing a DC power supply from the AC power supply of the main circuit, and a DC power supply from the DC power supply circuit. In the leakage breaker including a leakage detection circuit that opens the main circuit contact when the leakage of the main circuit is detected, the DC power supply circuit is a rectification circuit that rectifies an AC power supply of the main circuit, and the rectification circuit. An NPN type step-down transistor whose collector is connected to the positive side output terminal of the circuit, a base resistor connected between the collector and the base of the step-down transistor, a base of the step-down transistor and the rectifier circuit. A zener diode connected between the negative side output terminal and a smoothing capacitor connected between the emitter of the step-down transistor and the negative side output terminal of the rectifier circuit. Earth leakage breaker, characterized in that it comprises and. 2. The DC power supply circuit has a current detecting resistor having one end connected to the emitter of the step-down transistor and the other end connected to the positive side terminal of the smoothing capacitor, and a base and an emitter and base of the step-down transistor. 2. The earth leakage breaker according to claim 1, further comprising: a current limiting transistor having a collector connected thereto and an emitter connected to a common connection point of the current detecting resistor and the smoothing capacitor. 3. The DC power supply circuit has a ground terminal connected to a negative output terminal of a rectifier circuit, an input terminal connected to an emitter of a step-down transistor or an emitter of a current limiting transistor, and an output terminal of a positive electrode of a smoothing capacitor. The earth leakage breaker according to claim 1 or 2, further comprising a three-terminal regulator connected to the side terminal. 4. The DC power supply circuit comprises a smoothing capacitor connected between the positive and negative output terminals of the rectifier circuit, the smoothing capacitor being located in front of the step-down transistor. The earth leakage breaker according to any one of 3 above.