JPH052452U - Semiconductor circuit breaker - Google Patents

Abstract

(57) [Abstract] [Purpose] In a semiconductor circuit breaker configured by connecting semiconductor breaking elements in parallel, the increase in overcurrent at the time of short-circuit failure is limited to reduce the overshoot caused by operation delay, It is an object of the present invention to obtain a semiconductor circuit breaker which does not concentrate on an element having a small ON resistance and causes an element failure. A circuit breaker including n field effect transistors connected in parallel, a current detector for detecting a current value of a line to be cut off, and a drive circuit for driving the field effect transistor by an output signal of the current detector. In addition to the basic configuration, n
A semiconductor circuit breaker comprising an inductor between the drain side parallel connection point of each field effect transistor and each drain, and a snubber circuit between the drain and source of each field effect transistor.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

  This invention is a semiconductor circuit breaker that detects overcurrent in a DC power line and shuts it off at high speed. It is about.

[0002]

[Prior art]

As a conventional semiconductor circuit breaker of this type, there is one having a configuration shown in FIG. In the figure, 1 is _a line to be cut off, _2a to _2k to _2n are n (where n is an integer) field effect transistors, 3 is a current detector, 4 is a comparator, 5 is a drive circuit, and 6 is a snubber circuit. , 7 are capacitors forming the snubber circuit 6, and 8 are resistors forming the snubber circuit 6. I _L is a current flowing through the line 1 to be cut off, and V _REF is a reference voltage.

[0003]   Next, the operation will be described. N lines of electric fields connected in parallel are connected to the line 1 to be cut off. Effect transistor 2_a~ 2_nIs on, current I_LIs flowing. Current I _L Is detected by the current detector 3 and converted into a voltage signal, Data is input to the negative terminal of the data input terminal 4. The reference voltage V is applied to the positive terminal of the comparator 4._REF Is input And the current I_LIs within the specified rated value, the current detector 3 Reference voltage V more than the output voltage of_REF Is higher. At this time, the comparator 4 Output becomes high level, and the drive circuit 5 causes the n field effect transistors 2_a~ Two_nSince the ON voltage is continuously supplied between the gate and source of the Dista 2_a~ 2_nKeeps on.

Next, when the current I _L rises and reaches the current value to be interrupted by exceeding the rated value, the output voltage of the current detector 3 becomes a value higher than the reference voltage V _REF , and the output of the comparator 4 becomes Inverts to low level. As a result, the drive circuit 5 stops the supply of the on-voltage, so that the n field-effect transistors 2 _a to 2 _n are turned off and the current I _L is cut off. Since the comparator 4 has a hysteresis characteristic and keeps the low level even after the current I _L is cut off, the n field effect transistors 2 _a to 2 _n are kept off. Further, when the current is cut off at a high speed, a high surge voltage is generated due to the large dI / dt at the time of the cutoff and the line inductance of the line 1 to be cut off, and the field effect transistors _2a to _2n may be destroyed. . Therefore, in order to absorb the surge voltage and protect the field effect transistors 2 _a to 2 _n , the snubber circuit 6 including the capacitor 7 and the resistor 8 is used.

[0005]   The above operation will be described with reference to FIGS. 6 and 7. Figure 6 shows a semiconductor circuit breaker FIG. 1 is a power system diagram, in which 1 is a line to be cut, 10 is a constant voltage source, and 11 is a semiconductor circuit breaker. , 12 is a load, and 13 is a line inductance. Figure 7 is for a load short circuit This is the operating waveform. In the figure, the current value I_thIs the current cutoff level and the reference voltage V_REFIs a current value corresponding to. Also, time t_oIs the time when the load short circuit occurs, t _d Is the operation delay time.

When the power system shown in FIG. 6 is healthy, the output current of the constant voltage source 10 is supplied to the load 12 via the semiconductor circuit breaker 11 in the ON state. Here, when the load 12 is short-circuited at the time t _o , the current I _L increases at a constant increase rate determined by the line inductance 13 and the voltage value of the constant voltage source 10. Then, when the current I _L reaches the current cutoff level I _th , the semiconductor breaker 11 performs the cutoff operation.

However, there is an operation delay time t _d until the semiconductor circuit breaker 11 starts to cut off after detecting that the current I _L has reached the current cutoff level I _th . Therefore, as shown in FIG. 7, the operation waveform becomes a waveform with overshoot of the operation delay time t _d . This overshoot increases as the increase rate of the current I _L increases, that is, the line inductance 13 decreases, if the operation delay time t _d is constant. For example, in FIG. 6, the overshoot is larger when the to-be-interrupted line 1 is grounded at the point A than when the load 12 is short-circuited. In FIG. 7, the solid line shows the case where the line inductance 13 is small, and the broken line shows the case where the line inductance 13 is large.

As shown in FIG. 5, the semiconductor breaker is composed of n field effect transistors 2 _a to 2 _k to 2 _n connected in parallel. The main purpose of this is to increase the current capacity as a semiconductor circuit breaker by parallel connection. However, since the ON resistances of the _n field effect transistors 2 _a to 2 _k to 2 _n vary, the current I _L is not equally divided into n and the ON resistance is concentrated on the field effect transistor 2 _k having a smaller ON resistance than the other. There is an imbalance of doing. Therefore, if a large overshoot occurs at the time of a short circuit failure as described above, the rated current value of the element will be exceeded due to current concentration, and the field effect transistor 2 _k will be destroyed.

[0009]

[Problems to be solved by the device]

  Since the conventional semiconductor circuit breaker is configured as described above, a short circuit Depending on the part and line inductance, a large overcurrent due to operation delay may occur. The on-resistance is caused by the occurrence of shoot and the concentration of overcurrent accompanied by the shoot. There is a problem that the field-effect transistor having a small resistance is destroyed.

[0010]   This invention was made in order to solve the above problems, and it Limits the increase in overcurrent to reduce overshoot and turns on the overcurrent. To obtain a semiconductor circuit breaker that concentrates on elements with low resistance and does not lead to element failure With the goal.

[0011]

[Means for Solving the Problems]

  A semiconductor circuit breaker according to one embodiment of the present invention (hereinafter, referred to as “first semiconductor circuit breaker”). I will omit it. ) Is the drain of each of the field effect transistors connected in parallel. An inductor is provided between the drain side parallel connection point.

[0012]   A semiconductor circuit breaker of another embodiment (hereinafter, abbreviated as "second semiconductor circuit breaker"). Is connected in series to the drain side parallel connection point of the field effect transistors connected in parallel. It is equipped with a continuous inductor.

[0013]

[Action]

  A first semiconductor breaker according to the present invention is a field effect transistor connected in parallel. An inductor is provided between each drain of the star and the parallel connection point on the drain side. The current flowing through each field effect transistor in the transient state at the time of short circuit failure is Due to the inductor connected in series with the field effect transistor, the rate of current increase Limited. In this way, while reducing the overshoot at the time of short circuit failure, The even distribution of the increased current to each field-effect transistor allows for a specific field-effect transistor. Prevents overcurrent from concentrating on the transistor.

[0014]   A second semiconductor circuit breaker according to the present invention is a field effect transistor connected in parallel. It has an inductor connected in series at the drain side connection point of the transistor The current flowing through each field effect transistor in the transient state at the time of failure is The rate of current increase is limited by the rectifier. Therefore, in the case of short-circuit failure, overshoe Can be made smaller.

[0015]

【Example】

Example 1.   An embodiment of the first semiconductor circuit breaker of the present invention will be described below. In FIG. 1 is the blocked line, 2_a~ 2_k~ 2_nIs n field-effect transistors, 3 is current Detector, 4 is a comparator, 5 is a drive circuit, 6_a~ 6_k~ 6_nIs n snubber times Road, 7_a~ 7_k~ 7_nIs n snubber circuits 6_a~ 6_k~ 6_nThe capacities that make up 8_a~ 8_k~ 8_nIs n snubber circuits 6_a~ 6_k~ 6_nResistance that composes 9 _a ~ 9_k~ 9_nAre n inductors. Also, I_LFlows through the blocked line 1 Current, V_REF Is the reference voltage.

[0016]   2 is a power system diagram in which a semiconductor circuit breaker is used, and 1 is a line to be cut. 10 is a constant voltage source, 11 is a semiconductor circuit breaker, 12 is a load, and 13 is a line inductor. It is a closet.

Next, the operation will be described. In FIG. 1, the movements of the _n field effect transistors 2 _a to 2 _n , the current detector 3, the comparator 4, the drive circuit 5, and the reference voltage V _REF are the same as in the conventional configuration.

[0018] First, an n-number field effect transistor 2 _a to 2 _n are turned on, and to be cut off line 1, the following steady-state current I _L rating is flowing. In this case, the smaller the ripple current I _L, the inductor 9 _a to 9 _n operate as extremely low resistance and does not inhibit the flow of current I _L.

Now, assume that a short-circuit fault occurs and the current I _L starts to increase rapidly. In this case, the inductor 9 _a to 9 _n, the counter electromotive force proportional to the increase rate of current is generated. Considering the rate of increase of the current I _k flowing through one field effect transistor 2 _k , the rate of increase of the current I _k is given by the following equation, _where L _{k is} the value of the inductor 9 _k and V _k is the counter electromotive force.

[0020]

[Equation 1]

If the load 12 is short-circuited in FIG. 2 and the line inductance 13 is extremely small, the counter electromotive force V _k becomes approximately the output voltage E 1 of the constant voltage source 10, and therefore the equation ( 1) is

[0022]

[Equation 2]

It can be written as equation (2). That is, the rate of increase of the current I _k flowing through each field effect transistor 2 _k is limited by the inductor 9 _k . Therefore, if the values of the inductors 9 _{a to} 9 _k are adjusted, the n field effect transistors 2 ^{(1 )} To 2 ⁽ⁿ⁾ , the increase in transient current can be evenly distributed. Here, the increase rate of the current I _L is the sum of the equation (2).

[0024]

[Equation 3]

Equation (3) is obtained. Therefore, the rate of increase of the current I _L is limited by the inductors 9 _{a to} 9 _n , and the inductor delay is also taken into consideration in consideration of the operation delay time t _d until the semiconductor circuit breaker 11 starts shutting down after detecting the overcurrent. by setting the value of 9 _a to 9 _n, regardless of the site of the short circuit fault, the overshoot of the overcurrent due to the operation delay time t _d it is possible to below any level.

By the above operation, the current I _L at the time of short circuit failure in the power system of FIG. 2 becomes as shown in FIG. In the figure, the solid line shows the case where the circuit breaker according to the present invention is used, and the broken line shows the case where the conventional circuit breaker is used. Further, I _th is a DC cutoff level, and I _1im is an allowable current level for _preventing a device failure. As apparent from the figure, even if the operation delay times t _d of the two circuit breakers are the same, the rate of increase of the current I _L is limited by the inductors 9 _{a to} 9 _n . In that case, the overshoot is smaller, and the allowable current level I _1im or less can be _achieved .

Example 2. An embodiment of the second semiconductor circuit breaker according to the present invention is shown in FIG. In FIG. 4, 1 is _a line to be cut off, 2 field effect transistors from 2 _a to 2 _k to 2 _n , 3 is a current detector, 4 is a comparator, 5 is a drive circuit, 6 is a snubber circuit, and 7 is a snubber. A capacitor forming the circuit 6, 8 a resistor forming the snubber circuit 6, and 9 an inductor. I _L is a current flowing through the line 1 to be cut off, and V _REF is a reference voltage.

This is because in the first semiconductor circuit breaker shown in FIG. 1, instead of connecting the inductors 9 _{a to} 9 _n to the _n field effect transistors 2 _a to 2 _n, respectively, the _n field effect transistors 2 _a to 2 _n are connected. One inductor is connected in series to the drain side parallel connection points of _{a to} 2 _n . Thus, operation of the second semiconductor circuit breaker shown in FIG. 4, except even distribution function of the overcurrent with the inductor 9 _a to 9 _n are the same as the operation of the first semiconductor circuit breaker. The second semiconductor circuit breaker is a case where the field effect transistors 2 _a to 2 _n are connected in parallel for the purpose of making the on-resistance smaller than the increase of the current capacity, and the overcurrent I _L at the time of short-circuit failure is 1 The inductor 9 is set and used such that even if the field effect transistors 2 _k are concentrated in one field effect transistor 2 _k , the cutoff operation is completed before the field effect transistor 2 _k reaches the overcurrent fault.

[0029]

[Effect of device]

  As described above, according to the present invention, the field-effect transistors connected in parallel It was configured to limit the rate of increase of transient current flowing in each by an inductor. Therefore, the transient current does not concentrate on a certain element and the element failure does not occur. The effect of obtaining a semiconductor circuit breaker that can keep the flow overshoot below the allowable level is there.

[0030]   In addition, according to another embodiment of the present invention, when the current concentration on a certain device is allowed. Even in the case of a semiconductor, the transient current overshoot during interruption can be kept below the allowable level. The circuit breaker is obtained.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a first semiconductor circuit breaker of the present invention.

FIG. 2 is a power system diagram showing an example of use of the circuit breaker according to the present invention.

FIG. 3 is a waveform diagram showing the operation of the circuit breaker according to the present invention and the conventional circuit breaker.

FIG. 4 is a connection diagram showing an embodiment of a second semiconductor circuit breaker of the present invention.

FIG. 5 is a connection diagram showing a conventional semiconductor breaker.

FIG. 6 is a power system diagram showing an example of use of a conventional circuit breaker.

FIG. 7 is a waveform diagram showing the operation of the conventional circuit breaker.

[Explanation of symbols]

1 Blocked line 2 Field effect transistor 3 Current detector 4 comparator 5 drive circuit 6 snubber circuit 7 capacitors 8 resistance 9 inductor 10 constant voltage source 11 Semiconductor circuit breaker 12 load 13 line inductance

Claims (2)

[Scope of utility model registration request] 1. N snubbers composed of n field-effect transistors as semiconductor blocking elements connected in parallel, and a series connection of a resistor and a capacitor connected in parallel between the drain and source of each field-effect transistor. The circuit, a current detector for detecting the sum of the output currents of the n field-effect transistors connected in parallel, the output of the current detector and the reference voltage are compared, and the above n
A comparator for generating ON / OFF signals of the field effect transistors and a signal of the comparator are input, the hot side of the output is connected to the gates of the n field effect transistors, and the return side of the output is the n field effects. In a semiconductor circuit breaker composed of a drive circuit connected to the sources of transistors, the circuit breaker is inserted between the drain side connection points of the n field effect transistors connected in parallel and the drains of the field effect transistors. A semiconductor circuit breaker comprising n inductors. 2. A field effect transistor as n semiconductor blocking elements connected in parallel, a snubber circuit comprising a resistor and a capacitor connected in series, connected in parallel between the drain and source of the field effect transistor, and A current detector that detects the sum of the output currents of n field-effect transistors connected in parallel is compared with the output of the current detector and the reference voltage. A comparator that inputs an OFF signal and a signal of the comparator are input, the hot side of the output is connected to the gates of the n field effect transistors, and the return side of the output is connected to the sources of the n field effect transistors. In a semiconductor circuit breaker composed of a circuit, drain side contacts of the n field effect transistors connected in parallel are connected. A semiconductor circuit breaker comprising an inductor connected in series at a connecting point.