JP3140819B2 - DC circuit breaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC circuit breaker for interrupting a large DC current.

[0002]

2. Description of the Related Art Conventionally, interruption of a large current is mainly performed in an AC circuit, and the fact that an arc generated between open contacts is extinguished when the current at the time of reversal of the polarity of the AC becomes zero. are doing. In this case, the hot ionized gas between the contacts may be rapidly cooled in order to prevent re-ignition of the arc.

In the case of a DC circuit, since there is no current zero point, the arc is extended by extending the arc to make the arc voltage higher than the circuit voltage, or by forcibly creating a current zero point using an inductor or the like. . In addition, since a vacuum circuit breaker in which a contact is sealed in a vacuum vessel has an extremely short insulation recovery time, it is considered that if a current zero point can be created, it is possible to perform the interruption.

[0004]

However, in the above conventional example, a complicated mechanism or a special contact is required for extinguishing the arc when interrupting a large current, and it is difficult to extend the life and reduce the size. There is a problem that power is lost in a commutation circuit for preventing the occurrence of an arc, and a special circuit is required for driving thereof, which complicates the operation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a DC circuit breaker which solves the above-mentioned drawbacks, has a small and simple structure, hardly generates an arc when a large current is interrupted, and hardly causes a power loss. .

[0006]

In order to achieve the above-mentioned object, a DC breaker according to the present invention increases the impurity concentration in a thin portion of both P and N regions sandwiching a PN junction surface in a substantially step-like manner.
A PN junction diode in which at least one of the outer regions adjacent to the thin portion has a low impurity concentration is connected in parallel to a circuit breaker for breaking electrical connection.

[0007]

In the DC breaker having the above-described structure, in the transient state where the breaker shifts from conduction to cut-off, the current is absorbed by the reverse bias capacitance of the PN junction diode. Later, when the insulation of the circuit breaker becomes sufficient, the reverse bias capacity becomes small, so that the absorbed current decreases sharply, the voltage rises sharply, and the interruption is completed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows a configuration diagram of a charge limiting diode. The charge limiting diode 1 is a kind of PN junction diode, and is formed of a semiconductor having a PN junction surface 2 formed at a center portion and electrodes attached to both sides. The junction surface 2 of the PN junction is substantially flat, and the both sides of the junction surface 2 are stepwise increased to substantially the same impurity concentration, and the inner layers 3 and 4 having a thickness of, for example, about 0.1 μm are formed. Intermediate layers 7 and 8 having an impurity concentration as low as about the same level and a thickness of about several μm are formed outside the boundary surfaces 5 and 6 therebetween. Electrodes 11 and 12 are provided outside the intermediate layers 7 and 8 with the outer layers 9 and 10 having a particularly high impurity concentration interposed therebetween to realize ohmic contact. The inner layer 3, the intermediate layer 7, and the outer layer 9 are all P-type semiconductors, and the inner layer 4, the intermediate layer 8, and the outer layer 10 are N-type semiconductors. Therefore, the electrode 11 becomes the anode 1a and the electrode 12 becomes the cathode 1k.

FIG. 2 shows an impurity concentration distribution along a vertical section of the charge limiting diode 1. As shown in FIG. Here, X5 is the coordinates of the boundary surface 5 between the inner layer 3 and the intermediate layer 7, X2 is the coordinates of the bonding surface 2, X6 is the coordinate of the boundary surface 6 between the inner layer 4 and the intermediate layer 8, and the vertical axis is the impurity concentration. Is shown.

The reverse voltage Vr is applied to the charge limiting diode 1.
When the voltage Vr is sufficiently small, a depletion layer having a thickness proportional to the square root of the voltage Vr is formed in the inner layers 3 and 4 around the junction surface 2, but the thickness of the depletion layer also depends on the square root of the impurity concentration. When the depletion layer reaches the outside of the boundary surfaces 5 and 6, the expansion of the depletion layer with an increase in the applied voltage becomes steep. At this time, the N-type region in the depletion layer is positively charged due to the large amount of donor ions, and the P-type region is negatively charged due to the large amount of acceptor ions. Can be

The relationship between the reverse voltage Vr applied to the charge limiting diode 1 and the junction capacitance Cj is as shown in the characteristic diagram of FIG. That is, when the voltage Vr increases, the capacitance Cj decreases, and the rate of the decrease changes partly discontinuously. The threshold voltage is a voltage at which the thickness of the depletion layer becomes equal to the thickness of the inner layers 3 and 4.
Assuming that Vth, as Vr increases Vr <Vth, capacitance
Cj decreases little by little, but when Vr = Vth, the rate of decrease sharply increases, and when Vr> Vth, the capacitance Cj rapidly decreases at first,
As the reverse voltage Vr increases, the rate of decrease in the capacitance Cj decreases. Here, since the capacity is considered as a value obtained by differentiating the electric quantity with the voltage, the product of the capacity and the voltage is not equal to the electric quantity.

The charge limiting diode 1 is charged when a reverse voltage is applied, and when the charge amount exceeds a fixed value _Qo , the voltage rises sharply, and the charged charge amount becomes almost constant value Qo.
It has the property of being restricted to _o . This charge amount _Qo
Is determined from Q _o = eNXS. Here, S is the area of the bonding surface, N is the impurity concentration in the inner layers 3 and 4, that is, the acceptor ion concentration in the N region and the donor ion concentration in the P region, and X is the thickness of each of the inner layers 3 and 4. The change in the impurity concentration at the boundary surfaces 5 and 6 is as large and sharp as possible, and the charge limiting characteristic becomes steeper.

FIG. 4 shows the use of the charge limiting diode 1.
1 shows a delay circuit in which an input voltage Vin is
The output voltage is connected to be applied to the cathode of
Vout is connected to take out directly from diode 1.
And the anode of diode 1 is connected to the common terminal GND.
Have been. As the input voltage Vin, the threshold voltage of the diode 1
As shown in FIG. 5, a voltage V that is sufficiently larger than the voltage Vth
When input in steps, output after a certain delay time Tr
The voltage Vout rises rapidly and reaches the voltage V. This late
Delay time Tr is approximately Tr ≒ RQ_o  / V.

FIG. 6 shows another delay circuit, in which a diode 1
Is connected so that the input voltage Vin is applied to the resistor R, the anode of the diode 1 is connected to the input side, and the output voltage Vout is directly extracted from the resistor R. When a voltage V is applied to this circuit as an input Vin in a stepwise manner as shown in FIG. 7, the output voltage Vout becomes
It rises with Vin and falls quickly after the delay time Tr.

As described above, since the charge current of the charge limiting diode 1 rapidly decreases when the charge reaches the predetermined charge _Qo , a delay operation with switching characteristics can be realized.

FIG. 8 shows the circuit of FIG. 4 in which the resistance R is replaced with an inductance L, and the delay time Tr ′ is Tr ′ ≒.
(2Q _o L / V) ^1/2 . In this circuit, FIG.
When the input voltage Vin which becomes the voltage V in a step-like manner as shown in FIG. 4 is applied, the output voltage Vout rises rapidly after the delay time Tr ′, and settles to the voltage V after generating a considerably high overshoot peak.

FIG. 10 is a circuit diagram of an embodiment of a circuit breaker of a high current DC circuit. A fixed contact 31a of a circuit breaker 31 is connected to a positive electrode of a DC power supply 32 and a cathode 1k of a charge limiting diode 1, and the circuit breaks. The movable contact 31b of the vessel 31 has the load 3
The negative input terminal of the load 33 is connected to the negative input terminal of the DC power supply 32.

In such a circuit, when the circuit breaker 31 is open, the charge limiting diode 1 is connected to the cathode 1
The same voltage as that of the DC power supply 32 is applied with k being positive and the anode 1a being negative. However, no current flows because the voltage is reverse-biased with respect to the PN junction. Electric current flows. When the closed circuit breaker 31 is opened, current continues to flow due to the circuit conductors and the inductance of the load 33, but this current is absorbed by the junction capacitance of the charge limiting diode 1. Fixed contact 31a
When the movable contact 31b and the movable contact 31b are sufficiently separated from each other, the reverse voltage Vr of the charge limiting diode 1 rapidly rises above the voltage Vth, and the flowing current decreases sharply and eventually becomes zero.

In such a configuration, when the circuit breaker 31 is opened, a high voltage is hardly generated between the fixed contact 31a and the movable contact 31b, and a spark or arc discharge is hardly generated. It is possible, and the wear and evaporation of the contacts are reduced, so that the service life is extended and the contacts are hardly damaged. Further, since the charge limiting diode 1 has the characteristics of a diode and is not charged in the reverse direction, even if the charge limiting diode 1 is connected in series with the inductance of the circuit, a severe overshoot is immediately stopped and generation of noise is suppressed.

In the embodiment, the circuit breaker 31 is connected to one in the circuit.
Although it is provided, it is also possible to use not one but, for example, a plurality of them connected in series. The charge limiting diode 1 may be connected in parallel with the circuit breaker 31 of the main circuit when the circuit breaker 31 is opened, and may be connected via another switch.

FIG. 11 is a circuit diagram of the second embodiment. The movable contact 21b of the switch 21 and one end of the resistor 22 are connected to the cathode 1k of the charge limiting diode 1, and the resistor 22
Is connected to the anode 1a of the charge limiting diode 1 via the switch 23. Fixed contact 2 of switch 21
1a is connected to the fixed contact 24a of the circuit breaker 24, and the movable contact 24b of the circuit breaker 24 is connected to the anode 1a of the charge limiting diode 1. In the DC breaker having such a configuration, the positive contact of the DC power supply 25 is connected to the fixed contact 24a of the breaker 24, the positive input terminal of the load 26 is connected to the movable contact 24b, and the negative input terminal of the load 26 is DC power supply 2
5 is connected to the negative electrode.

In such a circuit, when power is supplied from the DC power supply 25 to the load 26, the circuit breaker 24 is closed with the switch 21 open, and then the switch 21 is closed. When the supply is cut off, the circuit breaker 24 is opened to perform a breaking operation while the switch 21 is closed and the charge limiting diode 1 is connected in parallel with the circuit breaker 24. After opening the circuit breaker 24, the switch 21 is opened after a certain time, then the switch 23 is closed, the charge limiting diode 1 is discharged, and then the switch 23 is opened.

With such an operation, power is supplied to and cut off from the load 26. With this configuration, a DC supply of a large current, a high voltage, or a high load is cut off as compared with the case where the circuit breaker 24 is used alone. be able to. That is, in the transition period from the moment when the contacts of the breaker 24 are separated to the time when the insulation between the contacts is completed, the breaker 24 acts as a resistive load, and generates a voltage determined by the distance between the contacts and the state of the material between the contacts. When a voltage exceeding the voltage is applied, discharge such as arc discharge occurs, and the interruption fails. However, in this embodiment, a current flows through the junction capacitance of the charge limiting diode 1 connected in parallel, and since this junction capacitance Cj is sufficiently large, the voltage does not increase so much until the breaker 24 is completely cut off. Moreover, the junction capacitance Cj of the charge limiting diode 1 is equal to the threshold voltage Vth
Since the above is small, when the voltage of the charge limiting diode 1 exceeds the threshold voltage Vth after the circuit breaker 24 is completely shut off, the current flowing in sharply decreases, so that the switch 21 can be opened after a short time. By opening the switch 21, the discharge of the charge limiting diode 1 is enabled, and at the same time, the load on the charge limiting diode 1 can be reduced. The resistor 22 has a low resistance with sufficient power so that the discharge at the threshold voltage Vth or less can be performed in a short time. It should be noted that another circuit breaker may be used instead of the switch 21, but the switch is considered to be sufficient because the charge limiting diode 1 bears the voltage. Further, since it is dangerous if the switch 23 and the switch 21 are closed at the same time, the switch 23 is a normally-off type push button type, but this may be linked with the switch 21.

FIG. 12 shows a circuit diagram of the third embodiment. A circuit breaker 41 is connected in parallel to the charge limiting diode 1,
A resistor 42 and a switch 43 connected in series are similarly connected in parallel, and a movable contact 44 b of a switch 44 is connected to the cathode 1 k of the charge limiting diode 1. In the DC breaker having such a configuration, the positive contact of the DC power supply 45 is connected to the fixed contact 44a of the switch 44, the positive input of the load 46 is connected to the anode 1a of the charge limiting diode 1, and the negative input of the DC power supply 45 is connected to the negative input. The negative input of the load 46 is connected.

The power is turned on by closing the circuit breaker 41 and the switch 44, and the power is turned off by opening the circuit breaker 41 while the switch 43 is open. As in the second embodiment, the transient current is absorbed by the charge limiting diode 1, and after this current decreases, the switch 44 is opened to disconnect the charge limiting diode 1 from the DC power supply 45, and the switch 43 is closed once. To discharge.

FIG. 13 shows a circuit diagram of the fourth embodiment. A circuit breaker 51 and a resistor 5
The movable contact 53b of the switch 53 is connected to the cathode 1k. The positive terminal of the DC power supply 54 is connected to the fixed contact 53 a of the switch 53, the positive input of the load 55 is connected to the anode 1 a of the charge limiting diode 1, and the DC power supply 54 Is connected to the negative input of the load 55.

When supplying power to the load 55, the circuit breaker 51 is closed before the power is turned on, and then the switch 53 is closed. When shutting off, first, the circuit breaker 51 is opened, and after a certain time, the switch 53 is opened.

In this circuit as well, almost all the current during the transitional period at the time of interruption is absorbed by the charge limiting diode 1, and the voltage rises sharply after the insulation of the circuit breaker 51 becomes sufficient. When this voltage rises to such an extent that the switch 53 can be turned off,
The switch 53 is opened to complete the cutoff. At this time, the difference from the third embodiment is that the current always flows through the resistor 52 when the switch 53 is opened. Therefore, the switch 53 is required to have a slight interruption capability. You. After the switch 53 is opened, the charge stored in the charge limiting diode 1 is discharged through the resistor 52. In order to reduce the power loss due to the resistor 52,
After opening the switch, as soon as the current decreases sufficiently, the switch 53
Shall be opened. In such a configuration, since the number of switches is one less, the operation is simplified as compared with the above embodiment.

FIG. 14 shows another embodiment of the charge limiting diode 1 ', in which the P-type intermediate layer 7 having a low impurity concentration in the previous embodiment is eliminated. In this case, the reverse voltage Vr becomes the threshold voltage Vt
When h is exceeded, the depletion layer spreads in the intermediate layer 8 and the junction capacitance is rapidly reduced. Even in such a structure, the same function as that of the charge limiting diode 1 of the previous embodiment can be realized, and the layer with the high impurity concentration is outside the layer with the low impurity concentration. Easy to manufacture. This is because it is easy to form a layer with a high impurity concentration outside the substrate with a low impurity concentration, and this is usually performed by an alloy method or the like, but the reverse structure is difficult to manufacture.

As described above, the charge limiting diodes 1 and 1 ′ each having the thin layer having a high impurity concentration provided on both sides of the bonding surface 2 and having the layer having a low impurity concentration provided outside at least one of the thin layers,
Since a non-linear characteristic as shown in FIG. 3 is shown when a reverse voltage is applied, it is effective in absorbing a transient current at the time of circuit interruption.

In the above-described embodiment, the outer layers 9 and 10 having a particularly high impurity concentration are provided inside the electrodes 11 and 12.
These may be removed if ohmic contact is obtained. Further, the inner layers 3, 4 or the intermediate layers 7, 8 may not have the same concentration. Although the thicknesses of the inner layers 3 and 4 are not necessarily equal, it is preferable to make them equal in order to increase the initial value of the junction capacitance Cj. And the inner layers 3, 4
The boundary surfaces 5 and 6 between the and the intermediate layers 7 and 8 do not have to be clear, that is, if there is a sufficient difference in impurity concentration in the vicinity of the boundary surfaces 5 and 6, it is assumed that the concentration changes continuously. Is also good.

[0032]

As described above, the DC breaker according to the present invention absorbs the transient current of the breaker into the above-mentioned PN junction diode, thereby facilitating the interruption and reducing the absorbed current sharply. The shut-off is completed quickly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a charge limiting diode.

FIG. 2 is an explanatory diagram of an impurity concentration distribution.

FIG. 3 is a characteristic diagram of junction capacitance and voltage.

FIG. 4 is a circuit diagram having a delay function.

FIG. 5 is an explanatory diagram of a transient response of an input / output voltage.

FIG. 6 is a circuit diagram having a delay function.

FIG. 7 is an explanatory diagram of a transient response of an input / output voltage.

FIG. 8 is a circuit diagram having a delay function.

FIG. 9 is an explanatory diagram of a transient response of an input / output voltage.

FIG. 10 is a circuit diagram of the first embodiment.

FIG. 11 is a circuit diagram of a second embodiment.

FIG. 12 is a circuit diagram of a third embodiment.

FIG. 13 is a circuit diagram of a fourth embodiment.

FIG. 14 is a configuration diagram of a charge limiting diode of an example.

[Explanation of symbols]

 1, 1 'charge limiting diode 2 junction surface 3, 4 inner layer 5, 6 boundary surface 7, 8 intermediate layer 9, 10 outer layer 11, 12 electrode 25, 32, 45, 54 DC power supply 21, 23, 43, 44, 53 Switches 22, 42, 52, resistors 24, 31, 41, 51 Circuit breakers 26, 33, 46, 55 Load

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-296624 (JP, A) JP-A-54-140176 (JP, A) JP-A-61-78020 (JP, A) JP-A-49-1979 128249 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 33/59 H01H 33/66

Claims (5)

(57) [Claims] 1. A PN junction wherein the impurity concentration of a thin portion of both P and N regions sandwiching a PN junction surface is increased in a substantially step-like manner, and the impurity concentration of at least one of an outer region adjacent to the thin portion is reduced. A DC circuit breaker, wherein a diode is connected in parallel with a circuit breaker for disconnecting electrical connection. 2. The circuit breaker includes a PN junction diode and
The DC breaker according to claim 1, wherein the DC breaker is connected in parallel to a series circuit of the switch. 3. The DC circuit breaker according to claim 2, wherein a series circuit of a second switch and a resistor is connected in parallel with said PN junction diode. 4. A switch is connected in series with the PN junction diode connected in parallel to the circuit breaker.
3. The DC circuit breaker according to claim 1. 5. A second power supply in parallel with said PN junction diode.
The DC circuit breaker according to claim 4, wherein a series circuit of a switch and a resistor is connected.