JPH09246931A - Overload protective circuit for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately protect a semiconductor by utilizing a fact that a voltage applied to the semiconductor element of various ratings is almost similarly changed corresponding to the degree of an overload state, making a voltage monitoring device monitor the voltage and switching a comparison reference value with the current detection signal of a current monitoring device when it exceeds a reference value. SOLUTION: The voltage monitoring device 20 compares the current detection signals Si with a current reference value Eia while the value of a current (i) is normal or less than a regular overcurrent and the current reference value Eib is short-circuited, however, compares the current detection signals Si with a higher current reference value Eia+Eib since the current reference value Eib is released when the current (i) is increased more and the voltage (v) exceeds a voltage reference value Ev. In such a manner, by different comparison references corresponding to the current (i) made to flow to the semiconductor element 1, thus the degree of the voltage (v) applied to it, the device 20 is made to detect the overload state, normally an overcurrent state and a short-circuit state, by mutually different references and the element 1 is protected. Then, an optimum value corresponding to the degree of the weight of the overload state to be detected of the element 1 is accurately set by the current reference values Eia and Eib.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention rationally protects a semiconductor element used in a power bridge circuit or the like according to an overload condition such as a mild overcurrent condition or a severe short-circuit current condition due to a short circuit of its load. To an overload protection circuit.

2. Description of the Related Art In order to protect a semiconductor element used in a bridge circuit device or the like, an abnormal current such as an overcurrent or a short circuit current is detected and then the current is cut off, or a safe current value is set. Since it is necessary to narrow down the current to the semiconductor element, it is usually detected by using the current detection resistor to detect the level of the detection signal value from the normal state to the overcurrent state.
It is customary to determine whether or not a short-circuit state is present, and to apply necessary protection to the semiconductor element according to the result of this determination. FIG. 4 shows such a conventional example. The object to be protected is the semiconductor element 1 which is an insulated gate bipolar transistor in the example of FIG. 4, and in the case of the bridge circuit device, of course, a plurality of semiconductor elements 1 are incorporated therein. Only one of them is shown and connected to the voltage V of the power source 2 of the bridge indicated by the thin line in series with the load 3 via the output terminal To on the collector side. The drive circuit 4 for the semiconductor element 1 receives the switching command Sw from the bridge control circuit 5 that controls the bridge circuit as a whole, and accordingly drives the semiconductor element 1 via the gate resistor 1b. To detect the current of the semiconductor element 1, as shown in the figure, an auxiliary emitter 1a is provided and the current detection resistor 6 is connected,
It is customary for the latter to take out the voltage drop due to the current received from the former as the detection signal Si. This detection signal Si is given to the comparators 7 and 8. The comparator 7 compares the signal value of the detection signal Si with the short circuit detection reference value Es and determines that it is in the short circuit state when it exceeds it, and the comparator 8 compares the signal value of the detection signal Si with the overcurrent detection reference value Eo. When it exceeds, it is judged as an overcurrent state and a high comparison output is issued. Of course, the overcurrent detection reference value Eo is set smaller than the short circuit detection reference value Es. In the illustrated example, the comparison outputs of the two comparators 7 and 8 are given to the OR gate 9 via the delay circuits 7a and 8a, respectively, and the high output of the OR gate 9 is given to the drive circuit 4 as the protection command Sp. Detection signal
In the overcurrent state where the signal value of Si is higher than the overcurrent detection reference value Eo and lower than the short circuit detection reference value Es, only the comparison output of the comparator 8 becomes high, and the protection command Sp is output from the OR gate 9 after the delay time by the delay circuit 8a elapses. Is output. In the short-circuited state, the comparison outputs of both comparators 7 and 8 both become high, but the delay time of the delay circuit 7a is set shorter than that of the delay circuit 8a. After a shorter time, the OR gate 9 outputs the protection command Sp. When the drive circuit 4 receives this protection command Sp, for example, the drive operation for the semiconductor element 1 is immediately stopped, so that the semiconductor element 1 is turned off and the overcurrent or the abnormal current that is a short-circuit current flowing through it is cut off. . The protection circuit including the comparators 7 and 8 and the OR gate 9 shown in FIG.
Drive circuit 4 provided for each semiconductor element 1 including
It is advantageous in terms of cost to incorporate the same into an integrated circuit chip for use and commonly use it for driving and protecting the semiconductor elements 1 having various ratings.

However, the conventional protection circuit as shown in FIG. 4 has a large number of constituent circuit elements, which is disadvantageous in terms of cost. In addition, the above-mentioned short-circuit detection reference value Es and overcurrent detection reference are provided. There is a problem that setting the value Eo is not always easy. That is, since the comparators 7 and 8 and the OR gate 9 of the protection circuit of FIG. 4 each require several to ten transistors, the protection circuit needs to be connected to the drive circuit 4 more than the drive circuit 4 when it is incorporated in the integrated circuit for the drive circuit 4. This is because it is necessary to devote a large chip area and the chip cost becomes high. If the rating of the semiconductor element 1 is different, the difference or ratio between the short-circuit detection reference value Es and the overcurrent detection reference value Eo, which is the most desirable for protection, will be slightly different. Therefore, simply adjust the current according to the current rating of each semiconductor element 1. Sufficient measures cannot be taken merely by setting the resistance value of the detection resistor 6. Therefore, as described above, if the same integrated circuit chip is commonly used for the semiconductor elements 1 having various ratings, sufficient protection cannot be provided. . An object of the present invention is to solve the problems of the conventional protection circuit, and to provide more desirable protection than the conventional one with a circuit configuration as simple as possible even when the semiconductor device has various current ratings and voltage ratings. It is to provide a protection circuit.

According to the overload protection circuit for a semiconductor device of the present invention, the above-mentioned problem is detected by detecting a current flowing through a semiconductor device to be protected and detecting a signal value representing the current value. Comparing the voltage value applied to the semiconductor device with the voltage value applied to the semiconductor element, the current detection means for emitting a signal, the current monitoring means for monitoring the signal value of the detection signal and outputting a protection command when it exceeds the current reference value. Using a voltage monitoring means for issuing a comparison signal whose logic state changes depending on the magnitude of both values, and a switching means for switching between the current reference value and the current detection signal value level according to the logic state of the comparison signal, a protection command is provided. It is solved by releasing the semiconductor device from the overload state based on The protection circuit of the present invention having the above-mentioned configuration pays attention to the fact that the voltage applied to the semiconductor element varies similarly in accordance with the overload state even if the current and voltage ratings of the semiconductor element are different, and a semiconductor circuit The element is provided with reasonable protection suitable for the overcurrent state and the short-circuit state. That is, the present invention generates a comparison signal whose logic state changes according to the magnitude of both values while comparing the voltage value applied to the semiconductor element with the predetermined voltage reference value in the voltage monitoring means having the above-mentioned configuration, and the switching means outputs the logic signal. By switching the current reference value or the current detection signal value to be given to the current detection means according to the state, the semiconductor element is provided with a reasonable protection suitable for the overload state. Also in the present invention, the current reference value and the current detection signal value are switched by the switching means in the above-described configuration so that the current monitoring means can detect the overcurrent state and the short-circuit state of the semiconductor element as in the conventional case. Is good. In addition, an overcurrent state or a short-circuit state often occurs only for a very short time, and protection of the semiconductor element in each case may lead to frequent unnecessary interruption of the load current. Then, it is more practical in practice to provide a protection command delay means and start protection of the semiconductor element based on the protection command after the delay. The voltage monitoring means can be appropriately configured by using, for example, a comparator, but in order to simplify the circuit configuration as much as possible, voltage dividing means for receiving the control power supply voltage,
It is very advantageous to construct the voltage monitoring means from the diode connected to the voltage dividing point and receiving the voltage applied to the semiconductor element in the opposite direction, and derive the potential at the voltage dividing point of the voltage dividing means as the comparison signal. . In order to easily switch the current reference value and the current detection signal value given to the current detection means, the current monitoring means is made to short-circuit or release one current reference value by using the two current reference values. The current reference value and the sum of both current reference values are switched and applied, or one current detection resistance is short-circuited or released by the switching means by using two current detection resistances connected in series as the current detection means. Is advantageous. The switching means in this case can be easily configured by using a normal transistor, but the configuration can be further simplified by using a depletion type transistor.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. 1 is a block circuit diagram showing an embodiment of the present invention for switching a current reference value, FIG.
Is a specific circuit diagram corresponding to the embodiment of FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment for switching the current detection signal value.
In each case, the same reference numerals are given to the portions corresponding to FIG. 4, and the description of the overlapping portions will be omitted as appropriate. The semiconductor element 1 shown in FIG. 1 is incorporated in the lower arm of the bridge circuit as in the conventional example of FIG. 4 described above. Since the load 3 of the bridge is usually inductive, the diode 1c for freewheeling is a semiconductor. It is connected in antiparallel to the element 1. The DC power supply 2 of the input voltage V received by the bridge circuit 2, the load 3, the drive circuit 4, the bridge control circuit 5 and the like are the same as in the conventional example of FIG. Current i flowing through the semiconductor element 1
The current detecting means 10 for detecting is composed of the current detecting resistor 11 connected to the auxiliary emitter 1a as in the conventional example, and the voltage drop due to the auxiliary emitter current is derived as the current detection signal Si. The semiconductor element 1 is turned on and off at a predetermined cycle, and the current i is interrupted accordingly.
Also has the same intermittent waveform as the current i. Current monitoring means 20
Consists of a single comparator 21, receives the above-mentioned detection signal Si at one of its inputs, compares the signal value with the current reference value Eia received at the other input in a normal state, and the former value is When the latter value is exceeded, protection command Sp is output. Although the semiconductor element 1 may be immediately turned off by the drive command 4 by this protection command Sp, in the illustrated embodiment, the protection command Sp
Is provided to the drive circuit 4 via the delay means 22. The voltage monitoring means 30 receives the voltage v applied to the semiconductor element 1, that is, the collector-emitter voltage of the insulated gate bipolar transistor, and always sets the value to the voltage reference value Ev.
The comparison signal Sc whose logic state changes depending on the magnitude of both values is compared with the above. In this embodiment, when the monitoring voltage value v exceeds the voltage reference value Ev, the logic state of the comparison signal Sc changes from low to high. Shall be changed to. The voltage monitoring means 30
Has a characteristic that the voltage v monitored by is increased almost linearly with respect to the current i flowing through the semiconductor element 1 with the increase of the current i except in the range where the current value is very small. In the present invention, the switching means 40 is caused to switch the current reference value to be given to the current monitoring means 20 according to the logic state of the above-mentioned comparison signal Sc. In the embodiment of FIG. 1, two current reference values Eia connected in series are used. Eib is provided, and a single switch is used as the switching means 40 to short-circuit the current reference value Eib when the logic state of the comparison signal Sc is low and when it is high. Therefore, the current monitoring means 20 is provided with the current reference value Eia when the comparison signal Sc is low and the sum of both current reference values Eia and Eib when it is high. In the protection circuit of FIG. 1 configured as described above, the voltage reference value Ev applied to the voltage monitoring means 30 becomes about the same as the voltage v applied to the short circuit current when the current i flowing through the semiconductor element 1 approaches the short circuit current. To set. As a result, the current monitoring means 20 compares the current detection signal Si with the current reference value Eia while the value of the current i is normal or less than a normal overcurrent and the current reference value Eib is short-circuited. When the voltage increases and the voltage v exceeds the voltage reference value Ev, the current reference value Eib
The current detection signal Si to a higher current reference value
Compare with Eia + Eib. As described above, in the circuit of the present invention, the current monitoring means 20 is set to the overloaded state, usually the overcurrent state and the short-circuited state, on the basis of the different comparison reference depending on the current i flowing in the semiconductor element 1 and thus the voltage v applied thereto. The semiconductor element 1 is protected by detecting with different criteria. As described above, according to the present invention, the voltage v which increases with the current i of the semiconductor element 1 is monitored by the voltage monitoring means 30, which is the voltage reference value.
When Ev is exceeded, the current reference value is switched by the switching means 40. Therefore, in this embodiment, the current reference value as a reference operation for comparing the current with the detection signal Si of the current by the current monitoring means 20 is determined by the current reference values Eia and Eib. It is possible to easily and accurately set the optimum value of 1 according to the degree of lightness of the overload state to be detected. The protection command Sp issued when the current monitoring means 20 detects the overload state of the semiconductor element 1 based on the current reference value Eia or Eia + Eib is as follows when the current detection signal Si has an intermittent waveform. According to it, it becomes a repetitive pulse waveform, but the delay means to receive it.
22 has a function of confirming the confirmation of the waveform to which the protection command Sp is applied. Only after the confirmation, the protection command Sp of high is driven by the drive circuit 4
Give to. In this embodiment, the drive circuit 4 turns off the semiconductor element 1 in accordance with the protection command Sp to turn off the current i as usual.
It is released from the overload condition by shutting off. FIG. 2 shows a more specific configuration example of the protection circuit of FIG. The voltage monitoring means 30 of this embodiment comprises a diode 31 which receives the voltage v to be monitored from the semiconductor element 1 in the reverse direction, and a voltage dividing means 32 which receives the control power supply voltage Vd and has a voltage dividing point connected to the diode 31. The potential at the voltage dividing point of the voltage dividing means 32 is derived as the comparison signal Sc. The voltage dividing means 32 is 1 as usual.
It is composed of a pair of voltage dividing resistors 32a and 32b, and the voltage dividing value is the voltage reference value Ev. Since the voltage reference value Ev is set higher than the sum of the voltage v applied to the semiconductor element 1 and the forward voltage of the diode 31 in the normal state or a normal overcurrent state, the diode 31 conducts in these states. Accordingly, the comparison signal Sc takes a low logical value, but when the voltage v increases near the short-circuited state and the diode 31 becomes non-conductive, the voltage reference value Ev is output as a high logical value of the comparison signal Sc. . The switching means 40 of this embodiment uses a depletion type transistor 41 that is always on, and shorts the current reference value Eib when the comparison signal Sc is low,
Release when high. Of course, the switching means 40 can also be constructed by combining enhancement type transistors in two stages. Although the voltage v applied to the semiconductor element 1 also fluctuates with the on / off operation of the semiconductor element 1, in the bridge circuit, the free wheeling diode is used when the semiconductor element 1 is off.
1c becomes conductive and the voltage v takes a negative value. Therefore, in a normal overcurrent state, the voltage v is always lower than the voltage reference value Ev and the comparison signal Sc is in a stable low state, but in the short-circuit state, the comparison signal Sc has a waveform in which pulse-like high is repeated. . In this short-circuit state, the current monitoring means 20
Eia + Eib and Eia are received alternately, but fortunately the current detection signal Sc takes 0 or a very small value during the time when the current reference value becomes Eia, which hinders the detection operation of the short circuit state of the current monitoring means 20. Does not occur. In the embodiment of FIG. 2, a CR time constant circuit or a charging / discharging circuit including a resistor 22a and a capacitor 22b is used as the delay means 22. Since the protection command Sp issued from the current monitoring means 20 in the overload state has a repetitive waveform of high pulse as described above, the capacitor 22 is connected via the resistor 22a.
b is charged during the high time of the protection command Sp and discharged during the low time. If the overload state disappears before the capacitor 22b is sufficiently charged, this short-time overload state is ignored, but when the charging voltage rises to a predetermined threshold value, the drive circuit 4 determines it to be high. The protection operation for the semiconductor element 1 is immediately started after being accepted as the protection command Sp. Now, assuming that the semiconductor element 1 is in the overcurrent state and the current monitoring means 20 receives the current reference value Eia, the peak value of the detection signal Si at that time naturally changes according to the degree of the overcurrent. The higher the peak value, the longer the signal value of the detection signal Si exceeds the current reference value Eia, and the wider the high pulse width of the protection command Sp issued by the current monitoring means 20 is. Therefore, the charging voltage of the capacitor 22b is It rises faster than when the peak value is low. As can be seen from this, the delay time or the time until the drive circuit 4 protects the semiconductor element 1 in the overcurrent state can be automatically adjusted by the delay means 22 of FIG. 2 according to the magnitude of the overcurrent. Of course, it is desirable to protect the semiconductor element 1 in the short-circuited state for a short period of time. Usually, this requirement can be satisfied by setting the current reference value Eib to the same level as Eia.
In the embodiment of FIG. 3, the detection sensitivity of the current detection means 10 is switched according to the logic state of the comparison signal Sc by the voltage monitoring means 30. Therefore, in the illustrated embodiment, two current detection resistors 11a and 11b connected in series are provided for the current detection means 10, and the current detection resistance 11b on the ground point E side is switched by the switching means 40 to the high level of the comparison signal Sc. Or short circuit or release depending on low. For example, the current detection resistor 11b is short-circuited when detecting the short-circuit state of the semiconductor element 1, and released when detecting the overcurrent state with high sensitivity. In this way, when detecting a short circuit state and an overcurrent state, both current detection resistors 11a and 11
It is preferable to set b to the same resistance value. Current monitoring means
20 is a comparator for the detection signal Sc from the current detection means 10.
21, the detection signal Sc is the result of detecting the current i of the semiconductor element 1 with the sensitivity adjusted as described above, so that the current reference value with which the signal value is to be compared is a constant value Ei in this embodiment. It can be fixed. The voltage monitoring means 30 may of course have the same configuration as that of FIG. 2, but in the illustrated embodiment, it comprises a comparator 33 and a delay means 34. The comparator 33 compares the voltage v applied to the semiconductor element 1 with the voltage reference value Ev, and the delay means 34 receives the output of the resistor 34a.
And a delay means 22 for protection command Sp including a capacitor 34b
It is a charging / discharging circuit similar to. As described above, when the peak value of the waveform of the voltage v exceeds the voltage reference value Ev, the comparator 33
Emits an output having a repeating waveform of a high pulse, and when this pulse causes the charging voltage of the capacitor 34b of the delay circuit 34 to rise to a predetermined value, the high level of the comparison signal Sc by the voltage monitoring means 30 is established. This comparison signal Sc by the voltage monitoring means 30 has two defined logic states of low and high, unlike the repetitive pulse-like waveform in the embodiment of FIG. In this embodiment, a normal enhancement type n-channel transistor is used as the switching means 40 for short-circuiting and releasing the current detecting resistor 11b. The switching means 40 releases the detection resistor 11b while the comparison signal Sc is low, and short-circuits according to the establishment of the high level. Furthermore, in the embodiment of FIG. 3, the comparison signal Sc from the voltage monitoring means 30 is given to the drive circuit 4. This is so that the protection mode can be switched between the overcurrent state and the short circuit state of the semiconductor element 1, and the drive circuit 4 judges that a short circuit has occurred when the protection signal Sp is received when the comparison signal Sc is high, for example. To turn off the semiconductor element 1 immediately, but the comparison signal Sc
When the protection command Sp is received in a low state, it is determined that the current is an overcurrent state and the abnormal signal So is sent to the bridge control circuit 5. Whether the bridge control circuit 5, which is usually a microprocessor, immediately stops the switching command Sw to the drive circuit 4 by judging from the operating state of the bridge circuit at that time, or reduces the on / off duty ratio to protect the semiconductor element 1 Can be selected, the semiconductor element 1 can be protected more reasonably from the viewpoint of the entire bridge circuit. The present invention is not limited to the above embodiments and can be implemented with various circuit configurations. For example, a flip-flop may be used in place of the delay means 34 used in the circuit of FIG. 3 for establishing the high logic state of the comparison signal Sc. Further, in the above embodiments, all the semiconductor elements 1 are insulated gate bipolar transistors, but of course, the present invention can be applied to other semiconductor elements.

As described above, in the overload protection circuit according to the present invention, the current detection means for detecting the current flowing through the semiconductor element to be protected and issuing a detection signal representing the current value, and monitoring the signal value thereof. Current monitoring means for outputting a protection command when the current reference value is exceeded, and voltage monitoring for issuing a comparison signal that compares the voltage value applied to the semiconductor element with the voltage reference value and switches the logic state according to the magnitude of both values. Means and a switching means for switching the level of the current reference value or the current detection signal value according to the logic state of the comparison signal, and the overload state of the semiconductor element is released based on the protection command, so that various ratings can be obtained. The voltage monitoring means is made to monitor this voltage by utilizing the fact that the voltage applied to the semiconductor element changes substantially in the same manner depending on the degree of the overload condition, and when it exceeds the voltage reference value, the current monitoring means Since the reference value for comparison with the current detection signal is switched by the switching means, even if the semiconductor element has different current ratings or voltage ratings, it is possible to accurately detect the degree of an overload state, for example, an overcurrent state or a short-circuit state. The semiconductor element can be appropriately protected according to the degree of its weight. Since the circuit of the present invention can be commonly used for protection of semiconductor elements of various ratings with the same circuit configuration by appropriately setting the current reference value and the voltage reference value, it is integrated in a small chip or an integrated circuit chip for a drive circuit. The cost of the overload protection circuit used for each semiconductor element forming the bridge circuit or the like can be significantly reduced as compared with the conventional case. It should be noted that the embodiment of the present invention in which a delay unit is provided for a protection command in association with the current monitoring unit and the semiconductor element is protected based on the protection command after the delay is provided in accordance with an overload state for only a very short time. Eliminates the risk of frequent unnecessary and harmful protective actions such as interruption of load current,
By providing the delay means with an appropriate operation time constant or charge / discharge characteristic, it is possible to provide a desired time characteristic for the overload protection operation. Further, as the voltage monitoring means, a voltage dividing means for receiving a predetermined power supply voltage and a diode connected to the voltage dividing point for receiving a voltage applied to the semiconductor element in the opposite direction are used, and the potential at the voltage dividing point of the voltage dividing means is The embodiment of the present invention that derives as the comparison signal has the advantage that the voltage reference value can be easily and accurately set by the voltage dividing ratio of the voltage dividing means with a very simple circuit configuration. Further, an embodiment in which two current reference values are used to cause the switching means to short-circuit or release one of the current reference values so that the current monitoring means switches and gives the sum of the other current reference value and both current reference values. , And two current detection resistors connected in series as the current detection means are used to short-circuit or release one of the current detection resistors by the switching means. There is an advantage that the signal level can be accurately switched.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention for switching a current reference value.

FIG. 2 is a specific circuit diagram corresponding to the embodiment of FIG.

FIG. 3 is a circuit diagram showing an embodiment of the present invention that switches a current detection signal value.

FIG. 4 is a circuit diagram showing a conventional example of an overload protection circuit.

[Explanation of symbols]

1 semiconductor element 1a auxiliary emitter for current detection of semiconductor element 3 load of semiconductor element 4 drive circuit for semiconductor element 5 bridge control circuit 10 current detection means 11 current detection resistors 11a, 11b two current detection resistors 20 current monitoring means 21 Comparator for current monitoring means 22 Delay means for protection command 30 Voltage monitoring means 31 Diode for voltage monitoring means 32 Voltage dividing circuit for voltage monitoring means 33 Comparator for voltage monitoring means 34 Delay means for voltage monitoring means 40 Switching Means 41 Depletion type transistor for switching means 42 Enhancement type transistor for switching means E Ground terminal of semiconductor element Ei Current reference value for current monitoring means Eia, Eib Two current reference values Ev voltage for current monitoring means Voltage reference value for monitoring means i Current flowing in semiconductor element Sc Comparison signal Si Current detection signal So Abnormal signal Sp Protection command Sw Semiconductor element Switching command To the semiconductor element of the output terminal v control power supply voltage of the voltage Vd dividing circuit for acting on the semiconductor element against

Claims (6)

[Claims] 1. A current detection means for detecting a current flowing through a semiconductor element and issuing a detection signal of a signal value representing the current value,
Current monitoring means that constantly monitors the signal value of the current detection signal and issues a protection command when it exceeds the current reference value, and compares the voltage value applied to the semiconductor element with the voltage reference value according to the magnitude of both values. The semiconductor device is provided with a voltage monitoring means for issuing a comparison signal whose logic state changes, and a switching means for switching one of a current reference value and a current detection signal value level according to the logic state of the comparison signal, based on a protection command. An overload protection circuit for a semiconductor device, which is configured to release an overload condition. 2. The circuit according to claim 1, wherein the level of either the current reference value or the current detection signal value is detected by the switching means by the current monitoring means by distinguishing between the overcurrent state and the short-circuit state of the semiconductor element. An overload protection circuit for a semiconductor device, which is characterized by being switched as follows. 3. The circuit according to claim 1, wherein a voltage dividing means for receiving a control power supply voltage is used as the voltage monitoring means, and a diode connected to the voltage dividing point for receiving the voltage in the reverse direction from the semiconductor element is used. An overload protection circuit for a semiconductor device, wherein a comparison signal is derived from a voltage dividing point of the means. 4. The circuit according to claim 1, wherein a protection command delay means is provided in association with the current monitoring means, and the overloaded state of the semiconductor element is released based on the delayed protection command. An overload protection circuit for semiconductor devices, characterized by: 5. The circuit according to claim 1, wherein two current reference values are used and one of the current reference values is short-circuited or released by the switching means so that the current monitoring means and the other current reference value are supplied. An overload protection circuit for a semiconductor device, characterized in that the sum of reference values is switched and applied. 6. The circuit according to claim 1, wherein two current detection resistors connected in series are used as the current detection means,
An overload protection circuit for a semiconductor device, characterized in that one detection resistor is short-circuited or released by a switching means.