JP2000299628A - Switching circuit and switching device - Google Patents

Abstract

(57) [Problem] To provide a switching device which does not require a shunt resistor and which can respond at high speed even to an abnormal current at the time of a rare short circuit such as an incomplete short circuit. SOLUTION: First, second and third semiconductor elements QA, Q
B, QC, and a second input terminal connected to the second main electrode of the first semiconductor element QA, and a second input terminal connected to the second main electrode of the third semiconductor element QC. Comparator CMP4
11, a first semiconductor device QA and a second semiconductor device Q
A first comparator CM for comparing the respective main electrode voltages of B
It comprises at least P1 and control voltage supply means 111 for supplying a control voltage to each control electrode of the first to third semiconductor elements according to the output of the first comparator CMP1. When an abnormal current occurs, the first semiconductor element QA is turned on / off to generate a current oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching circuit and a switching device, and more particularly to a semiconductor switching device suitable for a power supply control device.

[0002]

2. Description of the Related Art As a semiconductor switching device (power semiconductor device) used in a conventional power supply control device, there is, for example, one shown in FIG. The power supply control device shown in FIG. 10 is a device that selectively supplies power from a battery to each load in an automobile and controls power supply to the load by a transistor QF with a built-in temperature sensor. The power supply control device shown in FIG.
Is connected to one end of a shunt resistor RS, and the other end is connected to a drain terminal D of a transistor QF with a built-in temperature sensor. Further, a load 102 is connected to the source terminal S of the transistor QF with a built-in temperature sensor. Here, the load 102 corresponds to a headlight of an automobile, a drive motor of a power window, and the like. The power supply control device shown in FIG. 10 further detects a current flowing through the shunt resistor RS and controls the driving of the temperature sensor built-in transistor QF by a hardware circuit, and a current value monitored by the driver 901. An A / D converter 902 for controlling on / off of a drive signal of the transistor QF with a built-in temperature sensor and a microcomputer (CPU) 903 are provided. The transistor QF with a built-in temperature sensor has an overheat cutoff function of forcibly turning off the conduction state by a built-in gate cutoff circuit when the junction temperature rises to a temperature equal to or higher than a specified value.

In FIG. 10, ZD1 is a signal between the gate terminal G and the source terminal S of the transistor QF with a built-in temperature sensor.
This is a Zener diode that bypasses an overvoltage applied to the true gate TG of the power device QM while maintaining it at 2V. The driver 901 includes a differential amplifier 911, 913 as a current monitoring circuit, a differential amplifier 912 as a current limiting circuit, a charge pump circuit 915, an on / off control signal from the microcomputer 903, and an overload from the current limiting circuit. The drive circuit 914 is configured to drive the true gate G of the temperature sensor built-in transistor QF via the internal resistance RG based on the current determination result. If an overcurrent is detected via the differential amplifier 912 based on the voltage drop of the shunt resistor RS and the overcurrent is detected as exceeding the determination value (upper limit), the drive circuit 914 turns off the temperature sensor built-in transistor QF. ,
Thereafter, when the current decreases and falls below the determination value (lower limit), the transistor QF with a built-in temperature sensor is turned on. on the other hand,
The microcomputer 903 includes a current monitor circuit (differential amplifier 91).
1, 913), and if an abnormal current exceeding a normal value is flowing, the drive signal of the temperature sensor built-in transistor QF is turned off to turn off the temperature sensor built-in transistor QF. Note that if the temperature of the transistor with built-in temperature sensor QF exceeds a specified value before the drive signal of the off control is output from the microcomputer 903, the transistor with built-in temperature sensor QF is turned off by the overheat cutoff function.

[0004]

However, the above-described conventional power supply control device requires a shunt resistor RS connected in series to a power supply path for current detection. By increasing the load current,
There is a problem that the heat loss of the shunt resistor cannot be ignored.

The above-described overheat cutoff function and overcurrent control circuit function when a large current flows due to the almost complete short-circuit state occurring in the load 102 or the wiring. It does not function when a small short-circuit current flows due to the occurrence of a rare short-circuit such as a short-circuit, and the microcomputer 903 must detect an abnormal current via a current monitor circuit and control the transistor QF with a built-in temperature sensor to turn off. In some cases, the response by the microcomputer to such an abnormal current is poor.

Also, a shunt resistor RS and an A / D converter 90
2. Since the microcomputer 903 and the like are required, a large mounting space is required, and there is also a problem that these relatively expensive articles increase the apparatus cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and circumstances, and eliminates the need for a shunt resistor, and reduces the abnormal current when a rare short circuit such as an incomplete short circuit having a certain degree of short circuit resistance occurs. It is another object of the present invention to provide a switching circuit which enables a high-speed response and can be easily integrated.

It is another object of the present invention to provide a switching circuit capable of performing various measurements such as undercurrent detection, lamp disconnection detection, and open detection and controlling the same.

Still another object of the present invention is to eliminate the need for a shunt resistor directly connected to a power supply path for detecting a current, thereby suppressing heat loss of the device and preventing an incomplete short circuit having a certain degree of short circuit resistance. An object of the present invention is to provide an inexpensive semiconductor switching device that enables high-speed response to an abnormal current when a rare short circuit occurs and that is easy to integrate.

Still another object of the present invention is to detect an undercurrent,
An object of the present invention is to provide a semiconductor switching device capable of performing various measurements such as lamp disconnection detection and open detection and controlling the same.

[0011]

A first feature of the present invention is as follows.
A first semiconductor element having first and second main electrodes and a control electrode; a first main electrode and a control electrode respectively connected to the first main electrode and the control electrode of the first semiconductor element; Second
A second semiconductor element having a first main electrode, a first main electrode, a control electrode, and a second main electrode connected to the first main electrode and the control electrode of the first semiconductor element, respectively. Third
A first input terminal connected to the second main electrode of the first semiconductor element, a first comparator for comparing the respective main electrode voltages of the first and second semiconductor elements, A second comparator in which a second input terminal is connected to a second main electrode of the third semiconductor element; and a control electrode of each of the first to third semiconductor elements according to an output of the first comparator. A control voltage supply means for supplying a control voltage, detecting an abnormal current flowing through the first semiconductor element, and turning on / off the first semiconductor element when an abnormal current occurs to generate a current oscillation; This is a switching circuit that cuts off the conduction state of the first semiconductor element by the current oscillation. Here, MOS transistors, SITs, or BJTs can be used as the first to third semiconductor elements.
Also, various MOS composite devices and other insulated gate power devices such as IGBTs can be used. These semiconductor elements may be of an n-channel type or a p-channel type. In the case of a BJT or IGBT, the “first main electrode” refers to one of an emitter electrode and a collector electrode,
In an insulated gate transistor such as an OS transistor or a MOSSIT, it means one of a source electrode and a drain electrode. "Second main electrode" refers to BJT or I
In a GBT, it means either the emitter electrode or the collector electrode that does not become the first main electrode, and in the insulated gate transistor, it means either the source electrode or the drain electrode that does not become the first main electrode. That is, if the first main electrode is an emitter electrode, the second main electrode is a collector electrode, and if the first main electrode is a source electrode, the second main electrode is a drain electrode. The “control electrode” means, of course, the gate electrodes of BJT, IGBT and insulated gate transistors.

When, for example, a power MOS transistor is used as the first semiconductor element, the voltage between the terminals (drain-source voltage) of the power MOS transistor forming a part of the power supply path changes from the off state to the on state. In the voltage characteristics at the time of transition (for example, the fall in the case of an n-channel MOS transistor), according to the state of the power supply path and the load, that is, the time constant based on the wiring inductance and the wiring resistance and short-circuit resistance of the path Change. For example, in a normal operation in which a short circuit does not occur, the voltage quickly decreases to a predetermined voltage or less, but when a complete short circuit occurs, the voltage does not decrease to a predetermined voltage or less. Also, if an incomplete short circuit with some short circuit resistance has occurred,
Although it converges to a predetermined voltage, it takes a long time to converge.

A first feature of the present invention utilizes a transient voltage characteristic of a semiconductor element when transitioning from an off state to an on state in such a semiconductor element. That is, by detecting the difference between the voltage between the terminals of the first semiconductor element and the voltage between the terminals of the second semiconductor element (reference voltage), the voltage between the terminals of the first semiconductor element forming a part of the power supply path is determined. That is, the degree to which the voltage (that is, the current in the power supply path) deviates from the normal state is determined.

Therefore, it is possible to eliminate the need for a conventional shunt resistor connected in series to the power supply path for current detection. It is also possible to easily detect an abnormal current when a rare short such as an incomplete short circuit occurs.

According to a first feature of the present invention, a load connected to the second main electrode of the first semiconductor element, a first reference resistance connected to the second main electrode of the second semiconductor element, Third
It is preferable that the semiconductor device further includes a second reference resistor connected to the second main electrode of the semiconductor element. By forming a current mirror circuit with the first semiconductor element and the third semiconductor element, various measurements such as undercurrent detection, lamp disconnection detection, and open detection can be added according to the second reference resistance. I can do it.

Therefore, if the second reference resistor is a variable resistor, a function corresponding to a wider range of applications can be added. The method of changing the variable resistance may be a continuous change or a discrete change by preparing and switching a plurality of reference resistors.

The second reference resistor does not need to have ohmic characteristics (linear characteristics). If a characteristic obtained by simulating the non-linear characteristic of the load is given as the second reference resistance, it is possible to add a function corresponding to a wider range of uses such as checking the characteristics of the lamp.

A second feature of the present invention is that a first main electrode connected to an external input terminal and a second main electrode connected to an external output terminal are provided.
A first semiconductor element having a main electrode and a control electrode of
A second semiconductor element having a first main electrode and a control electrode connected to a first main electrode and a control electrode of the first semiconductor element, respectively, and a second main electrode connected to a first external terminal; ,
A third semiconductor element having a first main electrode and a control electrode respectively connected to the first main electrode and the control electrode of the first semiconductor element, and a second main electrode connected to a second external terminal; ,
A second comparator having a first input terminal connected to the second main electrode of the first semiconductor element and a second input terminal connected to the second main electrode of the third semiconductor element; A first comparator for comparing the respective main electrode voltages of the second semiconductor element, and a control voltage is supplied to respective control electrodes of the first to third semiconductor elements in accordance with an output of the first comparator. An abnormal current flowing to a load connected to an external output terminal, and when an abnormal current occurs, on / off control of the first semiconductor element to generate a current oscillation; This is a switching device that cuts off a conduction state between an external input terminal and an external output terminal by vibration.

In the second aspect of the present invention, it is preferable that the first to third semiconductor elements, the first comparator, and the control voltage supply means are integrated on the same semiconductor substrate.

When a power MOS transistor, for example, is used as the first semiconductor element constituting the semiconductor switching device, the power M which forms a part of the power supply path
The voltage between the terminals of the OS transistor (the voltage between the drain and the source) indicates the state of the power supply path and the load in the voltage characteristics at the time of transition from the off state to the on state (for example, falling in the case of an n-channel MOS transistor) ,
That is, it changes according to the wiring inductance of the path and the time constant based on the wiring resistance and the short-circuit resistance. For example,
In a normal operation in which a short circuit has not occurred, the voltage quickly falls below a predetermined voltage. However, in a case where a complete short circuit has occurred, the voltage does not fall below the predetermined voltage. Further, when an incomplete short circuit having a certain short-circuit resistance occurs, although it converges to a predetermined voltage, it takes a long time to converge.

A second feature of the present invention utilizes a transient voltage characteristic of the semiconductor element when transitioning from an off state to an on state in such a semiconductor element. That is, by detecting the difference between the voltage between the terminals of the first semiconductor element and the voltage between the terminals of the second semiconductor element (reference voltage), the voltage between the terminals of the first semiconductor element forming a part of the power supply path is determined. By judging the degree to which the voltage (that is, the current of the power supply path) deviates from the normal state, and connecting the first and second reference resistors to the first and second external terminals, respectively, By configuring a circuit, various measurements such as undercurrent detection, lamp disconnection detection, and open detection can be added. If the second reference resistor is a variable resistor, a function corresponding to a wider use can be added.

Therefore, the heat loss of the device can be suppressed by eliminating the need for the conventional shunt resistor connected in series to the power supply path for detecting the current. It is also possible to easily detect an abnormal current when a rare short-circuit such as an incomplete short-circuit having a certain short-circuit resistance occurs. In addition, overcurrent can be detected without using a shunt resistor. In particular, if the on / off control of the semiconductor switching device is configured by a hardware circuit, no microcomputer is required, and the occupied area can be reduced. The manufacturing unit price can be reduced.

In particular, the ratio of the number of unit cells constituting each semiconductor element may be determined so that the current capacities of the second and third semiconductor elements are smaller than the current capacity of the first semiconductor element. . By selecting the number of unit cells and setting the layout of the planar pattern of the power IC, the circuit configuration of the second and third semiconductor elements can be reduced in size, and the area of the semiconductor chip can be further reduced. In addition, the equipment cost can be significantly reduced.

[0024]

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

The current oscillation shutoff function switching device according to an embodiment of the present invention, as shown in FIG. 1, the first main electrode DA connected to the external input terminal T _1,
A first semiconductor element (main semiconductor element) QA and a second main electrode SA and the control electrode GA, which is connected to an external output terminal T _3, the first main electrode D of the first semiconductor element QA
A, a first main electrode D connected to the control electrode GA, respectively.
B, the control electrode GB and, a second semiconductor element having a second main electrode SB connected to the first external terminal T ₁₇ (first
Reference semiconductor element) QB and first semiconductor element QA
Of the first electrode connected to the main electrode DA and the control electrode GA, respectively.
Of the main electrode DC, the control electrode GC, and the second external terminal T ₁₆
Of the third semiconductor element (first reference semiconductor element) QC having the second main electrode SC connected to the first semiconductor element QA and the second semiconductor element QB, respectively. The first input terminal is connected to the first comparator CMP1 and the second main electrode SA of the first semiconductor element QA, and the second input terminal is connected to the second main electrode SC of the third semiconductor element QC. Is connected to the second comparator CMP411 and the first comparator C
It comprises at least control voltage supply means 111 for supplying a control voltage to each control electrode of the first to third semiconductor elements according to the output of MP1.

That is, the switching device with a current oscillation type cutoff function according to the embodiment of the present invention comprises a first semiconductor element QA serving as a main semiconductor element (power device) and the main semiconductor element (first semiconductor element). ) detects an abnormal current of QA, during abnormal current occurs to generate a current oscillation oN / oFF controls the main semiconductor element QA, by the current vibration, conduction between the external input terminal T ₁ and the external output terminal T ₃ This is a semiconductor integrated circuit in which a control circuit for interrupting the state is integrated on the same substrate. A hybrid IC using an insulating substrate such as ceramic or glass epoxy, an insulating metal substrate, or the like may be used as the substrate, but more preferably a power IC monolithically integrated on the same semiconductor substrate (same chip). good.

[0027] Normally, the power IC, the external input terminal _{T 1} to a power source 101 for supplying an output voltage VB, the load 102
It operates by connecting the external output terminal T ₃ to. In the power IC shown in FIG. 1, an overheat cutoff circuit 120 is connected between the control electrode GA of the main semiconductor element QA and the second main electrode SA in order to realize a heat-sensitive cutoff function. As the overheat cutoff circuit, for example, the circuit shown in FIG. 11 may be used (the following embodiment of the present invention will be described using the overheat cutoff circuit shown in FIG. 11). In addition,
When an ON / OFF count integration circuit (count control means) is provided, the thermal cutoff function is not essential. As the first semiconductor element, for example, a DMOS structure, a VMOS structure,
Alternatively, a power MOS transistor having a UMOS structure or a MOSSIT having a similar structure can be used. or,
MOS composite devices such as EST and MCT and other insulated gate power devices such as IGBT can be used.
Furthermore, if the gate is always used with a reverse bias, a junction MOS transistor, a junction SIT, an SI thyristor, or the like can be used. Main semiconductor element Q of this power IC
A may be an n-channel type or a p-channel type. That is, the switching device with the current oscillation type interruption function according to the embodiment of the present invention includes both an n-channel type and a p-channel type. FIG. 1 illustrates a switching device having an n-channel current oscillation type interruption function monolithically integrated on the same semiconductor substrate.

Each of the n-channel first to third semiconductor elements QA, QB, and QC has a pair of main electrodes including first and second main electrodes. For example, the first main electrode DA and the second main electrode SA of the main semiconductor element (first semiconductor element) QA are made of a metal thin film such as aluminum (Al) or an aluminum alloy (Al-Si, Al-Cu-Si). And each is connected to the first and second main electrode regions, which are high impurity density regions. The “first main electrode region” is either an emitter region or a collector region in an IGBT, or a source region or a drain region in an insulated gate transistor (power insulated gate transistor) such as a power MOS transistor or a power MOSSIT. Means one or the other. The “second main electrode region” is either an emitter region or a collector region that does not become the first main electrode region in an IGBT, or a source region that does not become the first main electrode region in a power insulated gate transistor. Or one of the drain regions. That is, if the first main electrode region is an emitter region, the second main electrode region is a collector region, and if the first main electrode region is a source region, the second main electrode region is a drain region. The “control electrode” means, of course, the gate electrode of the IGBT and the power insulated gate transistor. The “main electrode” and “control electrode” are similarly defined for the second and third semiconductor elements QB and QC having the same current-voltage characteristics as the main semiconductor element QA.

The overheat cutoff circuit 120 shown in FIG.
An overheat cutoff MOS transistor QS connected to the gate electrode GA of the main semiconductor element QA;
A latch circuit 122 that inputs a signal to the gate electrode of the transistor QS, a temperature sensor 121 that controls the state of the latch circuit 122, and the like are provided. That is, when the temperature sensor 121 detects that the surface temperature of the semiconductor chip 110 has risen to a temperature equal to or higher than the specified temperature, the latch circuit 12
2 changes, and this state is held in the latch circuit 122. As a result, the overheat cutoff MOS transistor QS
Turns on, short-circuits between the gate and source of the main semiconductor element QA, and forcibly turns off the main semiconductor element QA.

As the main semiconductor element QA, for example, a power device having a multi-channel structure in which a plurality of unit cells (unit cells) are connected in parallel may be used. And
The second and third semiconductor elements QB and QC are arranged at adjacent positions so as to be connected in parallel to the main semiconductor element QA. The second and third semiconductor elements QB, QC
Includes a temperature sensor, a latch circuit, or a MOS for overheating cutoff
A circuit for shutting off overheating of the transistor QS or the like is not essential. Since the second and third semiconductor elements QB and QC are arranged at adjacent positions in the same process as the main semiconductor element (main MOS transistor) QM, they are mutually affected by the influence of temperature drift and non-uniformity between lots. Variations in electrical characteristics can be removed (reduced). The number of unit cells connected in parallel constituting the second and third semiconductor elements QB and QC is adjusted such that the current capacity of the second and third semiconductor elements QB and QC is smaller than the current capacity of the main MOS transistor. are doing. For example, the second and third semiconductor devices QB, Q
For one unit cell of C, the main semiconductor element (main MO)
By configuring the number of unit cells of the (S transistor) QM to be 1000, the ratio of the channel width W of the second and third semiconductor elements QB and QC to the first semiconductor element QM is 1: 1000.

In FIG. 11, a temperature sensor 121 is formed by connecting a plurality of diodes made of polysilicon or the like in series, and the temperature sensor 121 is integrated near the main semiconductor element QA. As the junction temperature of the main semiconductor element QA increases, the surface temperature of the semiconductor chip increases, and the forward voltage drop of the plurality of diodes of the temperature sensor 121 gradually decreases. When the sum of the forward drop voltages of the plurality of diodes decreases to a potential at which the gate potential of the nMOS transistor Q51 is set to the “L” level, n
MOS transistor Q51 is turned off from the on state. Thereby, the gate potential of the nMOS transistor Q54 is pulled up to the potential of the gate control terminal G of the main semiconductor element QA, and the nMOS transistor Q54 is turned on. Therefore, the nMOS transistor Q53 is turned off, the nMOS transistor Q52 is turned on from the off state, and "1" is latched by the latch circuit 122. At this time, the output of the latch circuit 122 becomes “H” level, and the overheat cutoff element QS is turned on from the off state. As a result, the true gate TG of the main semiconductor element QA and the second main electrode (source electrode) SA are short-circuited, the main semiconductor element QA is turned off from the on state, and overheat is cut off.

Returning to FIG. 1, the switching device with a current oscillation type cutoff function according to the embodiment of the present invention is more specifically an n-channel type second and third semiconductor element QB, QC, Resistors R1, R2, R5, R331, zener diode ZD1, diode D1, first comparator C
MP1, a drive circuit 111 as control voltage supply means, a first input terminal connected to the second main electrode (source electrode) of the first semiconductor element QA, and a second main electrode of the third semiconductor element QC (Source electrode) connected to the second input terminal
The comparator CMP 411 and the main semiconductor element (first semiconductor element) QA and the same semiconductor substrate (semiconductor chip) 11
It is monolithically mounted on the 0. In FIG. 1, the Zener diode ZD1 maintains the voltage between the gate terminal G and the source terminal S of the main semiconductor element QA at 12 V, and bypasses the overvoltage when the overvoltage is applied to the true gate TG of the power device QM. Having.

Further, outside the semiconductor chip 110, the first
The first reference resistor Rr1 connected to the external terminal _{T 17} of,
The second reference resistor Rr connected to the second external terminal T ₁₆
2 are provided. The respective resistance values of the first reference resistor Rr1 and the second reference resistor Rr2 are determined by the ratio of the channel width W of the second and third semiconductor elements QB and QC to the main semiconductor element (first semiconductor element) QM. The selection should be made in consideration of the above. For example, as described above, the second and third semiconductor elements QB and QC and the main semiconductor element (main MOS transistor)
When the ratio of the channel width W of QM is 1: 1000,
One example is to set the resistance to be 1000 times the resistance of the load 102 in the overloaded state. By setting this first reference resistor Rr1 and second reference resistor Rr2, the main semiconductor element same drain as when overload current abnormal operation flows to QA - voltage V _{D S} between the sources of the second and third It can be generated in the semiconductor elements QB and QC. Other choices are possible. The first reference resistor Rr1 and the second
Depending on how to select each resistance value of the reference resistor Rr2,
Various measurements such as undercurrent detection, lamp disconnection detection, and open detection can be performed and controlled.

On the other hand, the external control electrode terminal _{T 2,} the switch SW1 and the resistor R10 is connected. The switching device with the current oscillation type cutoff function according to the embodiment of the present invention functions when a user or the like turns on the switch SW1. The drive circuit 111 as a control voltage supply means outputs a signal for driving and controlling these to the control electrodes of the main semiconductor element QA and the reference devices QB and QC based on a switching signal by turning on / off the switch SW1. The drive circuit 111 may be constituted by a BJT or a MOS transistor (for example, it may be constituted by a CMOS). If the drive circuit 111 is constituted by MOS transistors, a simple MO
The power IC according to the embodiment of the present invention (a switching device with a current oscillation type cutoff function) can be manufactured by the S transistor manufacturing process. Also, BJT
When the driving circuit 111 is configured by the above, the power IC according to the embodiment of the present invention can be manufactured by the BIMOS manufacturing process. The output voltage VB of the power supply 101 is, for example, 12
V, the output voltage VP of the charge pump is, for example, VB +
10V.

The first main electrode (drain electrode) DA of the main semiconductor element (first semiconductor element) QA and the first main electrode (drain electrode) DB of the second and third semiconductor elements QB, QC
DC are all connected to the external input terminal T _1, it is maintained at a common potential. Main semiconductor element (first semiconductor element)
A series circuit of a resistor R1 and a resistor R2 is connected between a first main electrode (drain electrode) DA and a second main electrode (source electrode) SA of the QA. The first comparator CMP1 shown in FIG.
The the "+" input terminal, the main semiconductor element main electrode voltage voltage obtained by dividing by the (drain D- source S voltage) V _DS between the resistor R1 and the resistor R2 of QA is supplied via a resistor R5 I have. The source voltage _{VSB of} the first reference semiconductor element QB is supplied to the “−” input terminal of the comparator CMP1. "+" Signal level at the input terminal _V +>"-" signal level at the input terminal V _- when the output of the comparator CMP1 becomes the "H" level, the drive circuit 111, the control electrode (the gate of the main semiconductor element QA Electrode). In the opposite case, the output of the comparator CMP1 becomes “L” level,
The drive circuit 111 turns off the gate drive of the main semiconductor element QA. As described later, the comparator CMP1 has a certain hysteresis characteristic.

FIG. 8 is a conceptual equivalent circuit diagram focusing on a main semiconductor element (first semiconductor element) QA of a switching device having a current oscillation type cutoff function according to an embodiment of the present invention. The equivalent circuit of the main semiconductor element QA as a main semiconductor element (first semiconductor element) - equivalent current source g _m
v _i, drain resistance _{r d,} the gate-source capacitance _{C G S,} the gate-drain capacitance _{C GD} and drain
This is simplified using the source-to-source capacitance _CDS . When the equivalent circuit of the main semiconductor element QA is used, the power supply 1
The power supply path from 01 to the load 102 is represented as a circuit as shown in FIG. The load 102 includes a wiring inductance L0 and a wiring resistance R0 of the power supply path.

FIG. 7 shows the drain-source voltage V of the main semiconductor element QA forming a part of such a power supply path.
_The falling voltage characteristic when the _DS transitions from the OFF state to the ON state is shown by the reference load (normal operation) when the wiring between the load 102 or the main semiconductor element QA and the load 102 is short-circuited.
Is a transient response curve shown when the load 102 has a resistance of 1 kΩ. The fall characteristic has a transient response according to the impedance of the entire power supply path according to the embodiment of the present invention, for example, the wiring inductance and the wiring resistance of the power supply line.

[0038] First, the drain when the resistance of the load 102 in FIG. 7 is a 1 k [Omega - the variation of the source voltage _{V D S,}
It can be considered as follows. That is, depending on the characteristics of the main semiconductor element QA used in this measurement, for example, the drain current _ID
= 12mA (when power supply voltage is 12V and load resistance is 1kΩ)
It is assumed that the true gate-source voltage V _TGS is approximately equal to the threshold voltage Vth = 1.6V. And FIG.
Since the charging of the true gate TG of the main semiconductor element QA by the drive circuit 111 is continued, the true gate-source voltage V _TGS rises if this state is continued.
However, since the drain-source voltage _VDS decreases and the true gate-drain capacitance value _CGD increases, the charge that reaches the true gate-source voltage _VTGS is absorbed. That is, the drain - source voltage V _DS is true gate - charge reaches the source voltage V _TGS is to generate a capacity sufficient not to cause potential increase, the true gate - source voltage V _TGS is about 1.6V (= Vth). That is, at each lapse of time after the main semiconductor element QA transitions to the ON state, the charged charge sent to the gate G by the drive circuit 111 is absorbed, and the true gate TG voltage V
Drain-source voltage V that keeps _TGS constant
_DS .

[0039] Here, the drain load resistance corresponding to 1 k [Omega lower load R - the difference from the curve when the load resistance = 1 k [Omega 7-source voltage _{V DS} and [Delta] V _DS.
Then, the true gate corresponding to the load R in the time t - the source voltage and V _{TGS R.} That is, if a voltage corresponding to the charge of (1) is _subtracted from the true gate-source voltage V _TGSR , Q _GD = ΔV _DS × C _GD + (V _TGSR −Vth) × C _GS. , The true gate-source voltage V _TGSR substantially _equals the threshold voltage Vth = 1.6V. In other words, the true gate-source voltage V _TGSR means that the potential has increased from the threshold voltage Vth = 1.6 V by a voltage corresponding to the charge Q _GD . This can be expressed by the following equation.

(V _TGSR −Vth) × C _GS + ((V _TGSR −Vth) −ΔV _DS ) × C _GD = (ΔV _DS − (V _TGSR −Vth)) × C _GD (2) V _TGSR −Vth = ΔV _DS × 2C _GD / (C _GS + 2C _GD ) (3) ∴ΔV _DS = (V _TGSR −Vth) · ((C _GS / 2C _GD ) +1) (4) That is, ΔV _DS is proportional to (V _TGSR −Vth). When the drain current _ID is zero, the drain-source voltage V is determined only by the circuit for charging the true gate and the Miller capacitance.
_Although the curve of _DS is determined, when the drain current _ID flows,
Back electromotive force is generated by the inductance L _C of the entire circuit, and the same effect as when the load resistance is increased is obtained. Therefore, when the drain current _ID is changing, an inductance equivalent resistance is generated, and even when the pure resistance value of the load becomes very small as in the case of dead short, the equivalent impedance of the load is the inductance of the entire circuit. L not decrease below a certain value determined by _C. Therefore, the drain current I
The rising slope of _D falls to a constant value, and the curve of the true gate-source voltage V _TGS also falls.

First Embodiment of Semiconductor Device (Power IC) of the Present Invention
Channel width W of reference semiconductor element QB and main semiconductor element QA
When the current mirror circuit is configured with the ratio of N2: N1 (n = N1 / N2 = 1000), the main semiconductor element Q
When the source voltage V _{SA of A} and the source voltage V _{SB of} the first reference semiconductor element QB match, (drain current I _DQA of the main semiconductor element) = 1000 × (first reference semiconductor element Q
B drain current I _{D QB} ). Therefore, I _DQA = 5 A as the drain current of the main semiconductor element QA, and I _DQB = 5 m as the drain current of the first reference semiconductor element QB.
When A is flowing, respectively, the drains of the main semiconductor element QA and the first reference semiconductor element QB - source voltage V _DS is consistent, therefore, the true gate - also matches source voltage V _{T GS.} That is, V _DSA = V _DSB ,
V _TGSA = V _TGSB . Here, V _DSA , V
_DSB is the drain-source voltage of the main semiconductor element QA and the first reference semiconductor element QB, respectively, and V _TGSA ,
V _TGSB is a true gate-source voltage of the main semiconductor element QA and the first reference semiconductor element QB, respectively.

Therefore, when the first reference semiconductor element QB is completely turned on, it can be approximated that the power supply voltage VB is substantially applied to both ends of the reference resistor Rr. Therefore, as a load of the first reference semiconductor element QB equivalent to a load of 5A connected to the main semiconductor element QA, the resistance value of the reference resistor Rr is determined as Rr = 12V / 5mA = 2.4 kΩ.

Next, the operation of the semiconductor device (power IC) used for the power supply line of the present invention in the pentode characteristic (drain saturation characteristic) region of the MOS transistor will be described. When the main semiconductor element QA transitions to the ON state, the drain current _IDQA rises toward the final load current value determined by the circuit resistance. The true gate-source voltage V _TGSA of the main semiconductor element QA is _equal to the drain current I
_{Taking the} value determined by _DQA , the drain-source voltage V
While being braked by the mirror effect of the capacitance of the capacitor C _GD due to the decrease in _DSA, this is also going to stand up. Further, the first reference semiconductor element QB is
In accordance with the gate voltage determined by A, it operates as a source follower using the reference resistance Rr as a load resistance.

The true gate-source voltage V _TGSA of the main semiconductor device QA increases as the drain current _IDQA increases.

V _DSA = V _TGSA + V _TGD ・ ・ ・ ・ ・ (5) V _DSB = V _TGSB + V _TGD From a relationship of _{····· (6), V DSA -V} DSB = V TGSA -V TGSB = (I DQA -n × I DQB) / g m become ..... (7). However, _{g m} is the transconductance of the main semiconductor element QA, n = N1 / N2 is the main semiconductor element QA ratio of the channel width of the first reference semiconductor element QB. Accordingly, by detecting the difference V _DSA -V _DSB between the drain and the source, the difference between the drain currents (I _DQA -n × I
_DQB ) can be obtained.

The drain-source voltage V _DSB of the first reference semiconductor element QB is input to the “-” input terminal of the first comparator CMP1. The drain of the main semiconductor element QA
The source-to-source voltage V _DSA is a value V _divided by R1 and the resistor R2.
₊ Is “+” of the first comparator CMP1 via the resistor R5.
Input to the input terminal. That is, V ₊ = V _DSA × R1 / (R1 + R2) (8) is input to the “+” input terminal of the first comparator CMP1. When the load side is in a normal state, (Rr / n) <
R, V ₊ < _VDSB , and the main semiconductor element QA
Maintain the ON state. Here, R is the value of the load resistance. When the load side is overloaded, (Rr / n)> R, and the _further, when the V _{+> V DSB,} in triode characteristic region, the main semiconductor element QA is turned off. Assuming that the source potentials of the main semiconductor element QA and the first reference semiconductor element QB are V _SA and V _SB , after the main semiconductor element QA is turned off, the source potentials V _SA and V _SB decrease toward GND. Therefore, both V _DSA and V _DSB increase.
Before the source potentials V _SA and V _SB reach the GND potential,
When the condition of V ₊ <V _DSB is satisfied, the main semiconductor element Q
A turns on. Immediately after transitioning to the ON state, the main semiconductor element QA has a pentode characteristic region (pinch-off region).
Then, the on state continues toward the triode characteristic region, and turns off when V ₊ > V _DSB . This is one cycle of the on / off operation. It is due to the inductance of the load circuit that once it is turned off, the off state is maintained, and once it is turned on, the on state is maintained. The inductance of the load circuit acts equivalently to the resistance when the current changes. When the current is decreasing, the sign of the inductance equivalent resistance becomes negative, and the load side resistance is reduced. On the other hand, when the current increases, the sign of the inductance equivalent resistance becomes positive, and the load-side resistance increases. Therefore, once the main semiconductor element QA is turned off, the off state is maintained, and when the main semiconductor element QA is turned on, the on state is maintained. On the first reference semiconductor element QB side, since the reference resistance Rr is n = N1 / N2 times larger than the load resistance R, the inductance effect is negligibly small. For this reason, it can be considered that the first reference semiconductor element QB side operates as a pure resistance circuit.

In the first comparator CMP1, the diode
Hysteresis is formed by the gate D1 and the resistor R5. main
When the semiconductor element QA transitions to the off state, the driving circuit 1
The gate potential is grounded by 11 sink transistors.
The cathode potential of the diode D1 is V_SA-0.
7V (forward voltage of Zener diode ZD1)
Therefore, the diode D1 conducts. As a result, the resistance R1
→ A current flows through the path of the resistor R5 → the diode D1, and the first
The signal level V of the "+" input terminal of the comparator CMP1 ₊Is
The above (8) when the drive circuit 111 controls the ON state.
It is larger than the value of the expression. Therefore, immediately after the transition to the off state
Specific drain-source voltage difference V, smaller than before
_DSA-V_DSBThe main semiconductor device QA remains off until
But then V_DSABy increasing
The signal level of the "+" input terminal of the first comparator CMP1.
V₊Is V_DSBSmaller than the first comparator CMP1
Changes from "L" level to "H" level. Obedience
Therefore, the main semiconductor element QA is again turned on.
The Rukoto. Note that the hysteresis characteristics
There are various methods, but this is one example.

The drain of when the main semiconductor element QA transition to the OFF state - source voltage _{V DS A} threshold V
_{Assuming DSAth} , the following equation holds. That is, V _DSAth −V _DSB = R2 / R1 × V _DSB (9) Equation (9) indicates an overcurrent determination value, and is satisfied in a triode characteristic region (ohmic characteristic region) and a pentode characteristic region (drain saturated region).

Next, in the triode characteristic (linear characteristic) region,
The operation will be described. Check that the main line is
When the conductor element QA transitions to the ON state, the main semiconductor element Q
A continuously maintains the ON state. others
The true gate-source voltage V_TGSA, V_TGSB
After reaching the pinch-off voltage, the main semiconductor element QA,
Both the first reference semiconductor element QB and the second reference semiconductor element QC are 3
Operates in the tube characteristic region. Semiconductor used for the power line of the present invention
In the body device, the first reference semiconductor element QB and the main semiconductor
Assuming that the ratio of the channel width W of the element QA is 1: n,
The first reference semiconductor element QB
ON resistance R of_{DS (ON) B}Is the main semiconductor element QA
Resistance R_{DS (ON) A}N times (R
_{DS (ON) B}= NR _{DS (ON) A}). Meanwhile, the first
Source potential of reference semiconductor element QB and first main semiconductor element Q
If the source potential of A is equal to the first reference semiconductor element Q
B drain current I_DQBIs the drain of the main semiconductor element QA.
In current I_DQA1 / n times (I_{D QB}= (1 /
n) · I_DQA). Typical 5A class semiconductor device
ON resistance R _{DS (ON)}If you refer to, for example, the main half
ON resistance R of conductive element QA_{DS (O N) A}To the gate
Source voltage V_GS= 10V, R_{DS (ON) A}
= 30 mΩ. n = N1 / N2 = 10
00, the power supply voltage VB = 12 V, the reference resistance Rr = 2.
If 4 kΩ, then V_DSB= I_DQB× (n · R_{DS (ON) A}) = 5 [mA] × 30 [Ω] = 0.15 [V] (10) V_DSA= I_DQA× 30 [mΩ] · · · · (11) V_DSA-V_DSB= 30 [mΩ] × (I_DQA−5 [A]) (12)

When an abnormality occurs in the load and the drain current _IDQA increases, the value of equation (12) increases. When the overcurrent determination value is exceeded, the main semiconductor element QA is turned off. In this case, the state transits to the off state via the pinch-off point, the operation state in the pentode characteristic region described above, and the off state. Then, the signal level V ₊ of the "+" input terminal of the first comparator CMP1 becomes V after a certain period of time due to the hysteresis by the diode D1 and the resistor R5 shown in FIG.
_It becomes smaller than _DSB , the output of the first comparator CMP1 changes from "L" level to "H" level, and the main semiconductor element QA is again turned on. In this way, the main semiconductor element QA repeats the transition to the ON state and the OFF state, and finally, the overheat cutoff circuit 120 operates to reach the overheat cutoff. If the power supply line returns to a normal state before the overheat interruption (an example of an intermittent short-circuit failure), the main semiconductor element QA continuously keeps on.

FIG. 9A shows the drain current _ID of the semiconductor device (power IC) used for the power supply line of the present invention,
(B) shows the corresponding drain-source voltage _VDS . In the figure, indicates a case of overload, and indicates a case of normal operation. When an overload condition occurs (in the figure)
In this case, the on / off control of the main semiconductor element QA is repeated as described above to greatly change the drain current _ID, and the periodic semiconductor heating action of the main semiconductor element QA causes the main semiconductor element QA to overheat. Hastened.

(Modification of Embodiment) As described above, the description has been given by the above embodiment. However, it should be understood that the description and drawings constituting a part of this disclosure limit the present invention. Absent. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

<First Modification> For example, in the above-described embodiment, the on / off frequency integration circuit 30 as shown in FIG.
4 can be connected to the nodes N51, N52, and N53 in FIGS. 1 and 11 to speed up the interruption of the main semiconductor element QA as the first semiconductor element in the case of an incomplete short circuit. That is, when the number of times of on / off control of the main semiconductor element (first semiconductor element) QA reaches a predetermined number, the main semiconductor element Q
The operation of turning off A can be performed.

As shown in FIG. 2, the on / off frequency integrating circuit 304 includes resistors R131 and R132 connected to the node N53 shown in FIG. 1, a capacitor C131 connected to the node N52 in FIG. Diode D132 and MOS transistor Q13 connected to node N51
1. It includes a backflow prevention diode D131 and a resistor R133.

In the overcurrent control, each time the gate potential of the main semiconductor device (first semiconductor device) QA periodically goes to "H" level, the capacitor C131 is charged via the resistor R132 and the backflow prevention diode D131. Is done. MOS
Since the gate potential of the transistor Q131 is initially lower than the threshold value, the transistor Q131 is off, but when the gate potential rises with the charging of the capacitor C131, the MOS transistor Q131 is turned off.
131 changes to the ON state. MOS transistor Q1
When the transistor 31 changes to the on state, the node N51 on the anode side of the temperature sensor 121 shown in FIG. 11 is pulled down. Semiconductor element Q
Block A.

<Second Modification> The nodes N53 and N53 in FIG.
The overheat cutoff promotion circuit 106 shown in FIG. 3 may be connected to N62 to speed up the cutoff of the main semiconductor element QA. That is, in the case of an overcomplete short circuit, the main semiconductor element QA
By repeatedly performing on / off control of the main semiconductor element QA
When the overheat cutoff is caused to function by the periodic heat generation function, the time until the overheat cutoff may be relatively long. In such a case, the shutdown of the main semiconductor element QA may be accelerated by the overheat shutdown promotion circuit 106.

As shown in FIG.
Is a MOS transistor Q221, a diode D22
1, a resistor R221 to R223 and a capacitor C221. In the overcurrent control, the capacitor C221 is charged via the resistor R222 and the backflow prevention diode D221 every time the gate potential of the main semiconductor element QA periodically goes to "H" level. The gate potential of MOS transistor Q221 is initially at or below the threshold value and is in an off state. However, when the gate potential increases with charging of capacitor C221, MOS transistor Q221 transitions to an on state. The node N62 via the resistor R221
Terminal TG (true gate of main semiconductor element QA)
, A current flows to the ground potential (GND), and the amount of charge stored in the terminal TG (node N62) decreases. For this reason,
Even for the same drain current _ID , the drain-source voltage V _DSA increases, so that the power consumption of the main semiconductor element QA increases and the overheat cutoff is accelerated. The resistance R
The smaller 221 is, the earlier the overheat cutoff is. Also, the resistor R22
3 is a discharge resistance of the capacitor C221, and R222Ｒ
It is desirable to set R223.

<Third Modification> Inrush current mask circuit 303 shown in FIG. 4 may be connected to nodes N52, N53 and N71. The inrush current mask circuit 303 includes MOS transistors Q311 and Q312 connected to the node N71, a diode D311 connected to the node N53, and a node N31.
52, a resistor R313, a capacitor C311 and resistors R311 and R312 are connected. In the inrush current mask circuit 303, the main semiconductor element Q
When A transitions to the ON state, the gate-source voltage V
_GSA is supplied to the gate of the MOS transistor Q312 via the diode D311 and the resistor R312, and the gate-source voltage V _GSA is also supplied to the diode D31.
1 and the MOS transistor Q31 via the resistor R311.
1 gate. MOS transistor Q312
Is connected to the main semiconductor element Q via a capacitor C311.
A is connected to the source SA of A (node N52), and immediately after the main semiconductor element QA transitions to the ON state, the capacitor C311 is not charged.
12, the gate potential of the MOS transistor Q312 cannot be turned on. The MOS transistor Q311 is on while the MOS transistor Q312 is off, and the voltage dividing point supplied to the + terminal (node N71) of the comparator CMP1 is applied to the source SA (node N52) of the main semiconductor element QA. Join.
Therefore, the output of the comparator CMP1 is kept at the “H” level, so that the main semiconductor element Q
A will not transition to the off state.

With the passage of time, the capacitor C311 is charged via the resistor R312, and finally the MOS transistor C311 is charged.
Transistor Q312 transitions to the on state. Accordingly, the MOS transistor Q311 transitions to the off state,
After the masking state ends, the overcurrent detection control functions. The resistor R313 is a discharge resistor for resetting the capacitor C311 after the main semiconductor element QA transitions to the off state. It is desirable to set R312≪R313 so as not to affect the mask time. Further, since the mask time is determined by the time constant of R312 × C311, the mask time can be adjusted by arbitrarily changing the capacitance value of the external capacitor C311 when forming one chip.

When the load 102 of the switching device having the current oscillation type interrupting function according to the embodiment of the present invention is turned on, an inrush current flows several times to several tens times of the stable state. The period during which the inrush current flows varies depending on the type and capacity (size) of the load 102, and is approximately 3 msec to 20 msec.
msec. If the overcurrent control described in the embodiment is performed during the period when the rush current flows, the load 102
Takes a long time to reach a steady state, and the response of the load itself may be poor, such as a delay in lighting of the light. Such a problem can be solved by adding the inrush current mask circuit 303 shown in FIG. 4 to the configuration of FIG.

<Fourth Modification> A first external terminal T ₁₇ and a second external terminal T provided around the semiconductor chip 110 are described.
Various reference resistors can be added to ₁₆ . These first external terminal T ₁₇ and the second external terminal T _16, since there as a pin of the internal (sealed) packages the semiconductor chip 110, a ceramic, an insulating substrate or an insulating metal substrate such as glass epoxy It is possible to add various resistors to these pins in the form of a hybrid IC using the same.

[0062] Figure 5 is a second plurality of second external terminal _{T 16}
, Rrn are connected in parallel, and the values are set to desired values by switching with switches S2, S3,..., Sn. The plurality of second reference resistors Rr2, Rr3,.
Rrn may be provided inside the chip 110, irradiated with an excimer laser or the like, and unnecessary resistance may be removed by blowing to achieve a desired value. The first external terminal _{T 17} a plurality of second reference resistance Rr2, Rr3, · · · · ·, connecting the Rrn in parallel, switches S2, S3, · · · · ·, as switched Sn You may comprise.

As shown in FIG. 6, the second external terminal T
₁₆ (or in-and first external terminal T ₁₇₎ to connect the variable reference resistor Rv, it may be the value to the desired value.

In the configuration as shown in FIG. 5 or FIG.
First reference resistance Rr1 and second reference resistances Rr2, Rr
3, ..., by setting freely RRN (or Rv), in case of connecting the various loads to the external output terminal T ₃ also, the same drain and when the load current in normal operation is flowing - source voltage _{V DS} the second and third semiconductor elements QB, it is possible to generate the QC. Therefore,
The first reference resistance Rr1 and the second reference resistance Rr2
By selecting the respective resistance values of Rr3,..., Rrn (or Rv), various measurements such as undercurrent detection, lamp disconnection detection, and open detection can be performed and controlled.

The first external terminal T ₁₇ and / or the second
Reference resistor connected to the external terminal T ₁₆ need not be a resistance of the ohmic characteristic (linear characteristic). If a non-linear characteristic obtained by simulating the non-linear characteristic of the load in an analog manner is given as a reference resistance, a function corresponding to a wider range of uses, such as checking the characteristics of a lamp, can be added.

As described above, the present invention naturally includes various embodiments and the like not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the claims that are appropriate from the above description.

[0067]

According to the switching circuit of the present invention, the conventional shunt resistor is unnecessary, and not only an overcurrent due to a complete short circuit, but also an abnormality when a rare short circuit such as an incomplete short circuit having a certain short circuit resistance occurs. The current can be detected easily and accurately.

According to the switching circuit of the present invention,
Depending on how to select the respective resistance values of the first reference resistance and / or the second reference resistance, various measurements such as undercurrent detection, lamp disconnection detection, and open detection, and their control can be performed.

Further, according to the switching device of the present invention, the heat loss of the device is suppressed by eliminating the need for the conventional shunt resistor, and not only an overcurrent due to a complete short circuit but also an incomplete short circuit having a certain degree of short circuit resistance. An abnormal current when a rare short circuit occurs can be easily and accurately detected.

Further, since a microcomputer is not required, the chip area can be reduced and the device cost can be significantly reduced, particularly when the control circuit of the semiconductor switch as the main semiconductor element is monolithically integrated on the same semiconductor substrate. Can be reduced.

Further, according to the switching device of the present invention, the value of each of the first reference resistor and the second reference resistor connected to the first external terminal and the second external terminal can be reduced by selecting the respective resistance values. Various measurements, such as current detection, lamp disconnection detection, and open detection, and their control can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a switching device with a current oscillation type cutoff function according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an on / off frequency integration circuit used in a switching device with a current oscillation type interruption function according to a first modification of the present invention.

FIG. 3 is a circuit configuration diagram of an overheat cutoff promotion circuit used in a switching device having a current oscillation type cutoff function according to a second modification of the present invention.

FIG. 4 is a circuit configuration diagram of an inrush current mask circuit used in a switching device with a current oscillation type cutoff function according to a third modification of the present invention.

FIG. 5 is a circuit configuration diagram of a switching circuit with a current oscillation type cutoff function according to a fourth modification of the present invention (part 1).

FIG. 6 is a circuit configuration diagram of a switching circuit with a current oscillation type cutoff function according to a fourth modification of the present invention (part 2).

FIG. 7 is an explanatory diagram for explaining the principle used by the switching device with a current oscillation type interruption function according to the embodiment of the present invention, and shows the rise of the drain-source voltage at the time of transition from the off state to the on state; FIG. 4 is an explanatory diagram of a falling characteristic.

FIG. 8 is a conceptual equivalent circuit diagram focusing on a main semiconductor element (first semiconductor element) of a switching device with a current oscillation type interruption function according to an embodiment of the present invention.

FIG. 9A is a diagram illustrating a switching device with a current oscillation type cutoff function according to an embodiment of the present invention.
FIG. 9B is an explanatory diagram showing a transient response characteristic of the drain current of the main semiconductor element (first semiconductor element), and FIG. 9B is a graph showing a corresponding transient response characteristic of the drain-source voltage.

FIG. 10 is a circuit configuration diagram of a conventional semiconductor switch.

FIG. 11 is a circuit configuration diagram of an overheat cutoff circuit.

[Explanation of symbols]

Reference Signs List 101 power supply 102 load 106 overheat cutoff promotion circuit 110 semiconductor chip 111 drive circuit (control means) 120 overheat cutoff circuit 301 overcurrent detection section 302 current enable section 303 inrush current mask circuit (prohibition means) 304 on / off number integration circuit (number of times) Control means 9 305 Charge pump section 306 Cutoff latch circuit C131, C221, C311 Capacitor CMP1 First comparator CMP411 Second comparator D1, D131, D132, D221, D311 Diode QA Main semiconductor element (first semiconductor element) QF Temperature Sensor built-in transistor QB MOS transistor (second semiconductor switch) QC MOS transistor (third semiconductor switch) Q131, Q221, Q311, Q312 MOS transistor RG Internal resistance R1, R2, R5 131~R133, R221~R
223, R311 to R313, R331, R412, R
413 resistance Rr1 first reference resistor Rr2, Rr3, ·····, Rrn reference resistor (second reference _{resistor) T 1, T 2, T} 3, T 11 ~T 18 input and output terminals ZD1 Zener diode

Claims (6)

[Claims] A first semiconductor element having first and second main electrodes and a control electrode; and a first main electrode connected to the first main electrode and the control electrode of the first semiconductor element, respectively. A second semiconductor element having a control electrode, a second main electrode, a first main electrode, a control electrode connected to the first main electrode and the control electrode of the first semiconductor element, respectively. A third semiconductor element having two main electrodes; a first comparator for comparing the respective main electrode voltages of the first and second semiconductor elements; and a second main element of the first semiconductor element. A first input terminal is connected to the electrode, and a second main electrode of the third semiconductor element is connected to a second input terminal.
And a control voltage supply unit that supplies a control voltage to each control electrode of the first to third semiconductor elements according to an output of the first comparator. An abnormal current flowing through the first semiconductor element is detected, and when an abnormal current occurs, the first semiconductor element is turned on / off to generate a current oscillation, and the first semiconductor element is generated by the current oscillation. A switching circuit for interrupting a conduction state of an element. 2. A load connected to a second main electrode of the first semiconductor element, a first reference resistance connected to a second main electrode of the second semiconductor element, and a load connected to a second main electrode of the second semiconductor element. Second
2. The switching circuit according to claim 1, further comprising a second reference resistor connected to said main electrode. 3. The switching circuit according to claim 2, wherein said second reference resistor is a variable resistor. 4. The switching circuit according to claim 2, wherein said second reference resistor is a resistor having a non-linear characteristic. 5. A first main electrode connected to an external input terminal,
A first semiconductor element having a second main electrode and a control electrode connected to an external output terminal; a first main electrode connected to a first main electrode and a control electrode of the first semiconductor element, respectively; A second semiconductor element having an electrode and a second main electrode connected to a first external terminal; and a first main electrode connected to a first main electrode and a control electrode of the first semiconductor element, respectively. A third semiconductor element having a control electrode, a second main electrode connected to a second external terminal, and a first comparison comparing respective main electrode voltages of the first and second semiconductor elements. A first input terminal is connected to a second main electrode of the first semiconductor element, and a second input terminal is connected to a second main electrode of the third semiconductor element.
And a control voltage supply unit that supplies a control voltage to each control electrode of the first to third semiconductor elements according to an output of the first comparator. An abnormal current flowing through a load connected to the external output terminal is detected, and when an abnormal current occurs, the first semiconductor element is controlled to be turned on / off to generate a current oscillation. A switching device for interrupting conduction between an input terminal and an external output terminal. 6. The switching device according to claim 5, wherein said first to third semiconductor elements, said first comparator, and control voltage supply means are integrated on the same semiconductor substrate.