JP2001160747A - Semiconductor switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct current limiting control corresponding to the state of overcurrent even in the case that incomplete short-circuit or the like is generated on a load side and to prevent useless power consumption. SOLUTION: A load short-circuit abnormality detection processing circuit 200 switches resistance elements R11 and R12 for overcurrent reference value generation corresponding to the current of a load 102 and performs overcurrent detection by a first overcurrent reference value corresponding to R11 and R12 or a second overcurrent reference value corresponding to only R11. In the case that a large current larger than the second overcurrent reference value flows in first prescribed time by a 1 msec timer circuit, an FET QA with a built-in temperature sensor is immediately OFF-controlled by overcurrent interruption control. After the lapse of the first prescribed time, in the case that a middle current larger than the first overcurrent reference value and smaller than the second overcurrent reference value flows, the FET QA with the built-in temperature sensor is repeatedly ON/OFF-controlled by the current limiting control and the FET QA with the built-in temperature sensor is controlled to an OFF state after the lapse of second prescribed time by an integration circuit 201.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor switching device which uses a power semiconductor as a switching element to turn on and off a relatively large current to a vehicle light or the like. The present invention relates to a semiconductor switching device that performs overcurrent protection control by current limitation when a current slightly larger than a rated load current during operation flows.

[0002]

2. Description of the Related Art Conventionally, power M
OS / FET and IGBT (Insulatedgate bipolar tran
2. Description of the Related Art A semiconductor switching device which turns on and off a relatively large current by using a switching device as a switching element is well known. As such a semiconductor switching device, an insulated gate type semiconductor switching device including an overheat protection control circuit and an overcurrent protection control circuit integrated is known (for example, Japanese Patent Application Laid-Open No. 5-95633, "Power Control Device").
JP-A-6-244414, "Protection circuit for semiconductor element and semiconductor device having the same" JP-A-6-244414, JP-A-9-244414
-331625, "Intelligent power switch and switching device", Japanese Patent Application Laid-Open No. 11-11331
No. “Electric power steering control device” publication example).

[0003] In such a semiconductor switching device, the overcurrent protection control circuit compares the voltage at which the current to the load is detected with a threshold value of the reference voltage, and determines the overcurrent when a short circuit occurs on the load side. Judgment is performed, and switching control is performed to forcibly turn off the switching element based on the judgment.

In such overcurrent protection control, since a large current flows when the load is completely short-circuited, an off control in which the switching element is immediately cut off from energizing the load for circuit protection and safety is performed. I'm trying to do it. However, in the state of the incomplete short circuit, the off control for the switching element does not operate, and a current slightly larger than the rated load current at the time of the switching operation may continue to flow. In such a case, a relatively large current flows wastefully, resulting in a large power consumption and a problem of promoting the deterioration and breakage of the circuit.

[0005] As a specific example, if an incomplete short circuit or the like occurs on the load side in a car in a state where a key switch is in a non-on state (alternator is in a non-operating state) and a relatively large current flows through a headlamp or the like. However, a relatively large current flows continuously, and the battery capacity becomes short immediately.

[0006]

As described above, in the conventional semiconductor switching device, even when an incomplete short circuit or the like occurs on the load side, the off control of the overcurrent protection control for the switching element may not operate. Therefore, there is a problem that a current larger than the rated load current during the switching operation continues to flow unnecessarily, resulting in a large power consumption.

The present invention has been made in view of the above circumstances, and an incomplete short circuit or the like has occurred on the load side, and a moderate overcurrent slightly larger than a rated load current value which is a current at the time of a switching operation has occurred. Also in this case, it is an object of the present invention to provide a semiconductor switching device capable of executing current limiting control according to an overcurrent state and preventing unnecessary power consumption.

[0008]

A semiconductor switching device according to the present invention comprises a semiconductor switching element for turning on / off a power supply to a load, a current detection value for the load, and a first overcurrent for judging an overcurrent state. An overcurrent detection means for detecting an overcurrent by comparing a reference value or a second overcurrent reference value larger than the first overcurrent reference value for determining an overcurrent of a large current; Performing an overcurrent cutoff control for turning off the semiconductor switching element when a large current is greater than an overcurrent reference value, wherein the detected current value is greater than the first overcurrent reference value and less than the second overcurrent reference value; Sometimes the semiconductor switch is repeatedly turned on.
Load current control means for performing current limit control for limiting the load current by off control.

Preferably, the overcurrent detecting means includes a first overcurrent detecting means for detecting the first overcurrent when the detected current value exceeds the first overcurrent reference value and the overcurrent state occurs.
Overcurrent detection of a large current is performed for a predetermined time, and then overcurrent detection of a medium current is performed based on the first overcurrent reference value.

[0010] Preferably, the load current control means controls the semiconductor switching element to an off state after performing the on / off control repeatedly for a second predetermined time.

Preferably, the semiconductor switching element, the overcurrent detection means, and the load current control means are mounted as a one-chip device.

In the above configuration, when an overcurrent state occurs due to a short circuit on the load side, the overcurrent detecting means is provided with the first
A medium current (medium overcurrent) greater than the overcurrent reference value and smaller than the second overcurrent reference value or a large current (large overcurrent) greater than the second overcurrent reference value is detected. For example, when the current detection value exceeds the first overcurrent reference value and becomes an overcurrent state, the first overcurrent reference value is switched to the second overcurrent reference value to perform the overcurrent detection of the large current for the first predetermined time. And then the second
The overcurrent detection is performed by switching from the overcurrent reference value to the first overcurrent reference value. The load current control means performs overcurrent cutoff control for turning off the semiconductor switching element at a large current, and repeatedly turns on and off the semiconductor switch at a medium current.
Current limit control for limiting the load current is performed by the off control. After the second predetermined time elapses after the current limit control is performed, the semiconductor switching element is turned off.

Thus, when a large current flows due to a complete short circuit or the like on the load side, the switching element is immediately turned off and the current flowing to the load is interrupted. When a moderate overcurrent that is larger than the value and close to the rated load current value flows, current limitation is repeatedly performed by on / off control.
As described above, appropriate load current control is performed according to the overcurrent state, so that a relatively large useless current is prevented from flowing to the load via the switching element, and unnecessary power consumption is suppressed. Can be reduced.

By configuring the semiconductor switching device as a one-chip device, the device configuration can be reduced in size, the mounting space can be reduced, and the device cost can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram and a circuit diagram showing a basic configuration according to an embodiment of the semiconductor switching device of the present invention. FIG. 2 is a configuration of a load short-circuit abnormality detection processing circuit which is a main part of the semiconductor switching device according to the present embodiment. 3 is a block diagram and a circuit diagram showing In FIG. 2, only the essential parts of the components corresponding to FIG. 1 are shown.

First, a semiconductor switching device having a basic configuration will be described with reference to FIG. The semiconductor switching device of the present embodiment is configured as a one-chip switching device 110, and the present applicant has proposed this basic configuration in Japanese Patent Application No. 11-140421.

The switching device 110 has a power supply 1
01 is connected to the supply voltage VB line,
A load 102 such as a lamp or a motor is connected as an external element. Also, the on-
Switch SW1 and resistance element R1 for giving an OFF instruction
0 is provided and connected to the supply voltage VB line and the switching device 110.

The switching device 110 includes a temperature sensor FET / QA having a switching function as a semiconductor switching element and its own temperature protection function, and is provided on a path for supplying the supply voltage VB from the power supply 101 to the load 102. , The drain D-source S of the FET QA with a built-in temperature sensor is connected in series. The switching device 110 controls power supply by switching control of the temperature sensor built-in FET / QA, and includes a drive control unit, an overheat protection unit, a load current detection unit, etc. This is an integrated circuit that is integrated and mounted on a PC.

The switching device 110 includes a charge pump circuit 305 and a drive circuit 111 as drive control means for controlling ON / OFF of the FET QA with a built-in temperature sensor. The drive circuit 111 includes a source transistor having a collector connected to the output of the charge pump circuit 305 and a sink transistor having an emitter connected to the ground potential connected in series.
Based on the switching signal by switching off, the source transistor and the sink transistor are turned on / off to output a signal for driving and controlling the temperature sensor built-in FET QA. When the supply voltage VB is, for example, 12 [V], the output voltage of the charge pump is, for example, VB + 10
[V] is set.

Further, a shutoff latch circuit 306 is provided as a means for protecting the temperature sensor built-in FET QA from overheating.
The cutoff latch circuit 306 realizes an overheat cutoff function which is also added to the thermal FET, and uses a built-in temperature sensor (not shown) to notify that the temperature of the temperature sensor built-in FET QA has risen to a temperature higher than a specified value. If detected, the detection information to that effect is held in the latch circuit, and the overheating cutoff FET (not shown) connected between the gate and the source of the temperature sensor built-in FET QA is turned on. Thus, the temperature sensor built-in FET QA is forcibly turned off. The information held by the latch circuit is output via the terminal T14 and can be used as a diagnosis (diagnosis) information signal by, for example, a microcomputer (not shown).

Further, an overcurrent detection control section 301 and an undercurrent detection section are provided as load current detecting means for the FET QA with a built-in temperature sensor. The overcurrent detection control unit 301 includes:
Specifically, FE as the second semiconductor switching element
It is realized by T · QB, resistance elements R1, R2, R5, Rr1, diode D1, and comparator CMP1. That is, the FET QA with built-in temperature sensor, the FET QB connected in parallel to the load 102, and the resistance element Rr1 are means for generating a first reference voltage in overcurrent detection, and the source SB potential of the FET QB is determined by the comparator. It is supplied to the inverting input terminal (-) of CMP1.
The non-inverting input terminal (+) of the comparator CMP1 is supplied with a voltage obtained by dividing the voltage VDSA between the drain D and source S of the FET QA with a built-in temperature sensor by the resistance elements R1 and R2 via the resistance element R5. Have been.

That is, as the reference voltage generating means, a first reference voltage having a voltage characteristic substantially equivalent to the voltage of the load connected to the source S of the FET QA with a built-in temperature sensor is connected to the FET QB on the same chip and the external circuit. Generated by the resistance element Rr1. The comparator CMP1 compares the first reference voltage with the voltage between the source S of the FET QA with built-in temperature sensor and the ground to detect a difference therebetween, thereby detecting an overcurrent.

When a complete short circuit (dead short circuit) occurs on the load 102 side by the overcurrent detection control unit 301, the output of the comparator CMP1 becomes valid (high level: hereinafter, referred to as H level) and the drive is started. Circuit 1
11 turns off the FET QA with a built-in temperature sensor. When an incomplete short circuit (rare short) having a certain short-circuit resistance occurs, the temperature sensor built-in F
On / off control (so-called current limit control) for repeating on / off operations of the ET / QA is performed.
In general, when a short circuit occurs on the load side, even if it is a dead short circuit, the temperature sensor FET QA often repeats the ON / OFF operation because of the resistance of the wiring and the like. The period from when the FET QA with a built-in temperature sensor changes from the OFF state to the ON state until the voltage VDSA between the drain D and the source S is saturated is a so-called pinch-off operation of the FET. That is, when an excessive current as described above flows, the FET QA with a built-in temperature sensor operates in the pinch-off region, and the on / off control is repeated. With such ON / OFF control, the supply voltage VB
In the power supply path from the line to the load, it is possible to protect the circuit including the temperature sensor built-in FET / QA against excessive current.

Here, the setting of the first reference voltage, that is, the setting of the resistance value of the resistance element Rr1 is performed as follows. That is, normally, the FET QA with a built-in temperature sensor has n F
Since ET (having the same characteristics as FET and QB) is connected in parallel, the resistance element Rr
1 may be set to [resistance value of load 102 × n], that is, the load resistance components are substantially equivalent when viewed from each of the temperature sensor built-in FET QA and the FET QB. In this case, it is appropriate to use a value of the short-circuit resistance at the time of incomplete short-circuit (rare short) (that is, a value in which the resistance element Rr1 is slightly larger than the resistance value of the load 102) as the resistance value of the load as a setting reference. is there. In FIG. 1, the output of the comparator CMP1 is supplied only to the drive circuit 111. However, the output can be output to the outside via a terminal and used for other control or the like.

Next, the undercurrent detecting section specifically includes F
ET / QC, resistance element Rr2 and comparator CMP2
Has been realized. That is, the FET QC and the resistance element Rr2 are means for generating a second reference voltage in detecting an undercurrent, and the source SC potential of the FET QC is supplied to the inverting input terminal (-) of the comparator CMP2. The non-inverting input terminal (+) of the comparator CMP2 is connected to the source S of the temperature sensor built-in FET QA.
A potential is supplied.

That is, a second reference voltage having a voltage characteristic substantially equivalent to the source voltage of the temperature sensor built-in FET QA is connected to the FET QC on the same chip and the resistance element Rr of the external circuit.
2 is generated. And the comparator CMP2
, The second reference voltage and the temperature sensor built-in FET QA
Undercurrent detection is performed by comparing these source voltages with each other and detecting these differences.

The undercurrent detector detects the load 102
When a disconnection failure or the like occurs on the
The output of P2 becomes valid (low level: hereinafter, referred to as L level), and an undercurrent detection signal is sent to the terminal T1 as a signal indicating that the load is open (for example, lamp disconnection information).
5 to the outside. Here, the setting of the second reference voltage, that is, the setting of the resistance value of the resistance element Rr2 is performed as follows. Similarly to the first reference voltage (the resistance element Rr1), the resistance value of the resistance element Rr2 may be set to [the resistance value of the load 102 × n]. It is appropriate to use a value on the order of resistance.

In addition to the drive control means, overheat protection means and load current detection means described above, the switching device 1
10 includes a power supply Enable 302 and masking (rush current mask circuit) 30 for avoiding overcurrent determination of the rush current.
3. ON / OFF to perform cutoff control by integrating the number of ON / OFF times
An OFF counting integration circuit 304 is also provided. Since these components are not directly related to the overheat cutoff control and the overcurrent protection control of the present invention, the description is omitted.

Finally, the characteristics of the switching device 110 can be summarized as follows.
This is advantageous for large current circuits because it eliminates the need for a shunt resistor for detecting the current flowing in the power supply path, and is advantageous for large current circuits. Second, it has high current sensitivity and high current detection accuracy. Third, it is simple. Drive control with built-in temperature sensor F
The ET / QA can be controlled on / off, and the overheating cutoff function and the ON / OFF counting and integrating circuit 304 enable high-speed processing as compared with the program processing of a microcomputer or the like. The circuit configuration can be reduced in size, the mounting space can be reduced, and the device cost can be reduced. Fifth, the current detection is based on the drain-source voltage VDSA of the FET / QA with a built-in temperature sensor.
Since the detection is performed by detecting a difference between the reference voltage and the second reference voltage, forming the FETs QB and QC and the FET QA with a built-in temperature sensor on the same chip allows a common-mode error factor in current detection, that is, a power supply Voltage fluctuations,
It is possible to eliminate the effects of temperature drift, lot-to-lot variation, and the like.

Here, the ON / OFF operation of the temperature sensor built-in FET QA will be described in more detail. Built-in temperature sensor F
When the ET / QA transitions to the ON state, the drain current ID
QA rises toward the final load current value determined by the circuit resistance. Further, the gate-source voltage VTGSA of the FET QA with a built-in temperature sensor takes a value determined by the drain current IDQA, and the brake is applied by the Miller effect of the capacitor CGD due to the decrease in the drain-source voltage VDSA. Stand up. In addition, FET
The gate-source voltage VTGSB of QB is determined by the fact that the FET QB operates as a source follower with Rr1 as a load.

Since the gate-source voltage VTGSA of the FET QA with a built-in temperature sensor increases as the drain current IDQA increases, the gate-source voltage becomes VTGSB <VTGSA. VDSA = VTGSA + VTG
D, VDSB = VTGSB + VTGD, so that VDSA
-VDSB = VTGSA-VTGSB. Here, the gate-source voltage difference VTGSA-VTGSB is equal to the drain current IDQA.
-IDQB, the current ID flowing through the temperature sensor built-in FET QA by detecting VTGSA-VTGSB.
The difference between QA and the current IDQB flowing through the FET QB can be obtained. IDQB approaches a current (IDQA / n) corresponding to IDQA as VDSB decreases (in this case, VDSA also decreases).

The drain-source voltage V of the FET QB
DSB is directly input to the comparator CMP1, and the voltage VDSA between the drain and source of the FET QA with a built-in temperature sensor is obtained by dividing the voltage VIN divided by the resistance elements R1 and R2 into the comparator C1.
Input to MP1. That is, VIN = VDSA × R1 / (R1 + R2) (1) is input to the comparator CMP1.

Immediately after the temperature sensor built-in FET QA transitions to the ON state, the input voltage VIN of the comparator CMP1 is changed.
Is VDSB> VIN with respect to the drain-source voltage VDSB of the FET QB, but the temperature sensor built-in FET QA
As the drain current IDQA increases, VIN increases and finally exceeds VDSB. At this time, the output of the comparator CMP1 changes from H level to L level, and the temperature sensor built-in FET QA is turned off.

Assuming that the drain-source voltage VDSA when the temperature sensor built-in FET QA transitions to the off state is a threshold value VDSAth, the following equation is established. VDSAth−VDSB = R2 / R1 × VDSB (2) Therefore, the overcurrent determination value is determined based on the equation (2).

That is, the drain current IDQA increases as time elapses after the temperature sensor built-in FET QA transitions to the ON state, and when the overcurrent determination value is exceeded and the drain-source voltage VDSA becomes larger than VDSAth. , The temperature sensor built-in FET QA transitions to the off state.

After the FET QA with a built-in temperature sensor transits to the OFF state, the drain current IDQA decreases and the input voltage VIN of the comparator CMP1 again changes to the FET QB.
VDSB> VIN for the drain-source voltage VDSB of
Becomes At this time, the output of the comparator CMP1 changes from the L level to the H level, and the temperature sensor FET
The QA is turned on. As described above, the FET QA with a built-in temperature sensor repeats the transition to the ON state and the OFF state in the pinch-off region.

Next, the configuration of the load short-circuit abnormality detection processing circuit 200 shown in FIG. 2 will be described. The semiconductor switching device of the present embodiment has a load short-circuit abnormality detection processing circuit 200 corresponding to the load short-circuit abnormality detection processing means of FIG. 2 integrated and mounted in the same package in addition to the basic configuration of FIG. It has become.

This load short-circuit abnormality detection processing circuit 200
The resistance elements R11 and R12 for generating first and second overcurrent reference values connected in series to the source of the reference FET QB and the current detection value of the temperature sensor built-in FET QA correspond to the first overcurrent reference. And a comparator CMP1 that outputs an H level when the value is larger than the value. Also,
An integration circuit 201 including a resistance element and a capacitor (RC) for integrating the H level output from the comparator CMP1 for a predetermined integration period is provided.

The 1 msec timer circuit 20 counts 1 msec with respect to the H level signal from the comparator CMP1 and outputs an H level signal during the counting.
2 is further provided, and an output signal of the 1 msec timer circuit 202 is input to a gate, and H
Switching FE that conducts (non-conducts) by a level (or L level) signal and short-circuits (opens) resistive element R12
T · QS is provided. Further, each input terminal is connected to the source of the current mirror FET / QC and the source of the temperature sensor built-in FET / QA, and an amplifying element 203 for differentially amplifying these input currents, and a second element based on the reference voltage Vref1. A comparator CMP2 for comparing the overcurrent reference value with the output of the amplification element 203 is provided. Further, a comparator CMP3 for comparing the integrated output of the integrating circuit 201 with an overcurrent integration reference value based on the reference voltage Vref2 is provided.

Further, the comparators CMP1 and CMP
AND gate circuit 20 for obtaining a logical product output of the comparison result of 2
4, the output of the AND gate circuit 204 and the comparator C
An OR gate circuit 205 for obtaining a logical sum output with the comparison result of MP3;
Is provided.

That is, FET QB, switching F
ET / QS, resistance elements R11, R12, comparator C
The overcurrent detection means is constituted by MP1 and the driving circuit 11
1, integration circuit 201, 1 msec timer circuit 202, amplification element 203, AND gate circuit 204, OR gate circuit 205, latch circuit 206, comparator CMP2
The load current control means is constituted by the CMP3.

The load short-circuit abnormality detection processing circuit 200 shown in FIG. 2 is provided together with the configuration of the overcurrent detection control unit 301 shown in FIG. 1 and one of them (the configuration shown in FIG. 1 or the configuration shown in FIG. 2).
Can be switched by using diode switching or the like to operate. Further, instead of the configuration of the overcurrent detection control unit 301 and the like shown in FIG. 1, only the load short-circuit abnormality detection processing circuit 200 shown in FIG. 2 may be provided, and any of these configurations is included in the present invention.

Next, the operation of the embodiment corresponding to the present invention will be described. As shown in FIG. 1 and FIG.
01 is connected to an energizing path for supplying the supply voltage VB to the load 102 with a temperature sensor built-in F as a semiconductor switching element.
The drain D-source S of the ET / QA is connected in series, and the switching control of the FET / QA with a built-in temperature sensor is performed based on the on / off of the switch SW1, thereby supplying the supply voltage VB to the load 102. The basic operation of the semiconductor switching device that is turned off (on / off) is executed.

Here, the operation when a short circuit occurs on the load side and an excessive current flows will be described in detail. The load short-circuit abnormality detection processing circuit 200 shown in FIG. 2 performs overcurrent cutoff control that immediately shuts off the temperature sensor built-in FET / QA according to the magnitude of the current detection value when a short circuit occurs on the load 102 side. , A current limit control for repeatedly turning on / off the temperature sensor built-in FET QA for a predetermined period. Specifically, in the case of a moderate overcurrent (medium current, for example, 5 amps [A] or more and 30 [A] or less) slightly larger than the rated load current value of the switching operation, the current limiting control is performed for the second predetermined time. FE with built-in temperature sensor
T.QA is turned off, and in the case of an overcurrent larger than that (large current, for example, 30 [A] or more), the temperature sensor FET QA is immediately turned off. This prevents a relatively large current from continuing to flow even when an intermediate short current flows due to an incomplete short circuit or the like, and wasteful power consumption can be reduced.

FIG. 3 is a timing chart showing the operation of the load short-circuit abnormality detection processing circuit 200. In the present embodiment, it is determined whether or not an overcurrent state has occurred due to a load short circuit or the like based on a first overcurrent reference value (here, 5 [A]), and it is a medium overcurrent due to an incomplete short circuit. Whether the current is a large overcurrent due to a complete short circuit or not is determined by a second overcurrent reference value (here, 30 [A]).

As shown in FIG. 3A, when a short circuit or the like occurs in the load 102, the current (current detection value) flowing through the power supply path is set based on the combined resistance value of the resistance elements R11 and R12. When the value exceeds 1 overcurrent reference value (5 [A]: larger than the rated load current value of the switching operation and corresponding to a current detection value close to the rated load current value), the output of the comparator CMP1 changes from the L level. Invert to H level. At this time, the H level output of the comparator CMP1 is input to the integration circuit 201, and the integration circuit 201
To a predetermined value. The H level output of the comparator CMP1 is set to 1 msec by the timer circuit 2
02, and the 1 msec timer circuit 202 is activated.

The 1 msec timer circuit 202 is provided as shown in FIG.
As shown in (b), an H-level signal is output for a 1 msec count period, and this H-level signal is input to the gate of the switching FET QS and the switching F
ET / QS is turned on (conducting). This switching FE
When T.QS is turned on, both ends of the resistance element R12 are short-circuited, and the overcurrent reference value is changed from the first overcurrent reference value to the second overcurrent reference value (30) based only on the resistance value of the resistance element R11.
[A]: corresponds to overcurrent determination of large current due to complete short circuit). At this time, the output of the comparator CMP1 is once inverted to L level.

In the amplifying element 203, a temperature sensor built-in FE
Source output of T / QA and FET / Q for current mirror
C is differentially amplified with the source output of C.
Is compared with the reference voltage Vref1 (corresponding to the current detection value of 15 [A]) by the comparator CMP2. Here, as shown by the solid line in FIG.
When it becomes larger, the output of the comparator CMP2 is inverted to the H level. Further, the detected current value is 30 [A].
When it becomes larger, the output of the comparator CMP1 is inverted to the H level by the determination based on the second overcurrent reference value.

Comparator CMP1 and Comparator C
The output of MP2 is input to the AND gate circuit 204,
The output of the AND gate circuit 204 is the OR gate circuit 205
Through the latch circuit 206. Then, a control signal for off control is input from the latch circuit 206 to the drive circuit 111, and the FET / QA with a built-in temperature sensor is forcibly and immediately turned off. That is, when a large current flows due to a complete short circuit, the temperature sensor built-in FET QA is forcibly shut off within 1 msec.

When the 1 msec timer circuit 202 times out as shown in FIG. 3B when the current detection value is 5 [A] or more and 30 [A] or less, an L level signal is output from the 1 msec timer circuit 202 to the switching FET. The signal is input to the gate of QS and turned off (non-conducting). When the switching FET QS is turned off, the overcurrent reference value is switched from the second overcurrent reference value to a first overcurrent reference value (equivalent to 5 [A]) based on a combined resistance value of the resistance elements R11 and R12. Thus, the above-described repetitive ON / OFF control (current limit control) of the temperature sensor built-in FET QA is performed. At this time, in the integrating circuit 201, FIG.
As shown in (c), the output of the comparator CMP1 is integrated during an integration period corresponding to a second predetermined time during which the on / off control is repeatedly performed.

The voltage value (overcurrent integral value) due to the electric charge accumulated in the capacitor of the integrating circuit 201 is calculated by a comparator CMP3 at a reference voltage Vref2 (overcurrent integral reference value: product of arbitrary current and time (for example, electric charge Q = 10 [A] x 1
0 [msec]). Here, the overcurrent integration value in the integration circuit 201 becomes larger than the overcurrent integration reference value (the integration period ends).
Then, the output of the comparator CMP3 is inverted from L level to H level. The output of the comparator CMP3 is input to the latch circuit 206 through the OR gate circuit 205. Then, a control signal for off control is input from the latch circuit 206 to the drive circuit 111, and the FET with a built-in temperature sensor is input.
QA is forcibly turned off. That is, when a moderate overcurrent flows due to an incomplete short circuit, the current limit control is performed until the second predetermined time (integration period) elapses, and then the temperature sensor built-in FET QA is forcibly shut off.

The above-described integration period of 10 A × 10 msec is a time during which no element destruction occurs due to an increase in the internal temperature of the FET / QA with a built-in temperature sensor due to repeated ON / OFF control. This time is the temperature sensor built-in F
What is necessary is just to change suitably according to the structure of the interruption | blocking latch circuit provided in ET / QA.

By the end of the integration period, the detected value of the current flowing through the temperature sensor FET QA is 5
Returning to [A] or less (rated load current value or less),
The output of the comparator CMP1 is inverted to L level. At this time, the capacitor voltage of the integration circuit 201 discharges through a discharge resistance element (not shown), and returns to the initial state. In this case, the L-level switch switching signal due to the turning off of the switch SW1 shown in FIG.
When it is reset by being input to 6, the drive circuit 111 is turned on and reset to the initial state.

During the 1 msec shown in FIG. 3 (b), for a current of 30 [A] or less, the comparator C
Since the output of MP1 is not inverted to the H level, the driving circuit 11
1 does not turn off. When a large current of 30 [A] or more occurs, the drive circuit 111 is turned off and the temperature sensor built-in F
ET / QA is controlled to be off. At this time, 30
FE with built-in temperature sensor for excessive current value close to [A]
Due to the variation of the overheat cutoff temperature of the T / QA, the overheat cutoff may be executed to be turned off.

FIG. 4 is a diagram for explaining a specific setting of the resistance values of the resistance elements R11 and R12 for generating the overcurrent reference value in the load short-circuit abnormality detection processing circuit 200.

Here, the number ratio of the FETs QA with a built-in temperature sensor and the FETs QB for reference (that is, the overcurrent detection sense ratio) is set to 1000, and VB =
12 [V]. Note that Vb = Vr. The resistance value Rr of only the resistance element R11 or the combined resistance of the resistance elements R11 and R12 is, as shown in FIG.
Overcurrent [A] (corresponding to the first overcurrent reference value for medium or less overcurrent detection) or more or 30 [A] (corresponding to the second overcurrent reference value for large overcurrent detection) or more This is for detecting a case, and is obtained by the following equation (3).

Rr = 12 [V] / (5 [A] / 100
0) = 2.4 [kΩ] (in case of overcurrent detection of 5 [A] or more) Rr = 12 [V] / (30 [A] / 1000) = 400 [Ω] (3) (30 [A] ] In the case of overcurrent detection above

As described above, the switching of the resistance value Rr for generating the overcurrent reference value is performed by turning on / off (conducting / non-conducting) the switching FET / QS through the comparator CMP1, the integrating circuit 201 and the 1-msec timer circuit 202. Performed by As a result, the overcurrent cutoff control by the large overcurrent detection at 30 [A] is executed for 1 msec after the overcurrent state is reached, and the current limit by the small overcurrent detection at 5 [A] after 1 msec has elapsed. Control (repeated on / off control) is executed.

As described above, according to the present embodiment, when the load side is short-circuited and an overcurrent state is detected, the overcurrent reference value is set to the second value during the first predetermined time (1 msec) for judging complete short-circuit. It switches to the overcurrent reference value (corresponding to 30 [A]) and detects overcurrent of 30 [A] or more. If a large overcurrent flows due to complete short circuit, etc., the FE with built-in temperature sensor
T · QA is forcibly controlled to be immediately turned off. And
After the lapse of the first predetermined time (1 msec), the overcurrent reference value is switched to the first overcurrent reference value (corresponding to 5 [A]), and 5
[A] The above overcurrent detection is performed, and when a moderate overcurrent close to the rated load current value flows due to an incomplete short circuit or the like, the on / off control of the temperature sensor built-in FET / QA is performed and the load 102 side is performed. Limit the current flowing through. further,
After the current limit control is performed for the second predetermined time (corresponding to 10A × 10 msec, which is the integration period), the temperature sensor built-in FET / QA is controlled to the off state.

As a result, when a large short-circuit or the like occurs on the load side and a large overcurrent flows, the overcurrent cutoff control is immediately executed to cut off the current. Even when a moderate overcurrent that is slightly larger than the rated load current value, which is the current during operation, occurs, the current limiting control is performed, and appropriate load current control is performed according to the state of the overcurrent. As a result, the temperature sensor built-in FE
Since a relatively large useless current is prevented from flowing to the load via T · QA, power consumption can be reduced.

By configuring the semiconductor switching device as a one-chip switching device 110, the device configuration can be reduced in size, the mounting space can be reduced, and the device cost can be reduced. further,
FET • QB, on the same switching device 110
Since the QC and the FET / QA with a built-in temperature sensor are mounted, power supply voltage fluctuations and temperature drifts occur at the same time,
Since there is no characteristic difference between the semiconductor elements and no variation between production lots occurs, an operation error hardly occurs and a highly accurate and stable operation can be obtained.

In the above-described embodiment, the load short-circuit abnormality detection processing circuit 200 shown in FIG. 2 has been described as being mounted in the same package as the semiconductor switching device body. However, the present invention is not limited to this. Instead, the present invention also includes a configuration in which a load short-circuit abnormality detection processing circuit is provided as an external circuit in the semiconductor switching device shown in FIG.

Further, 1 msec in the operation of the embodiment
And the time such as 10 A × 10 msec are not particularly limited and are changed as a design matter. The setting of the L level and the H level is also a matter of design, and is inverted depending on the polarity of the element used.

[0064]

As described above, according to the present invention, when an incomplete short circuit or the like occurs on the load side and a moderate overcurrent slightly larger than the rated load current value, which is the current during the switching operation, occurs. In such a case as well, the current limiting control can be executed according to the state of the overcurrent, and the effect that unnecessary power consumption can be prevented can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram and a circuit diagram showing a basic configuration according to an embodiment of a semiconductor switching device of the present invention.

FIG. 2 is a block diagram and a circuit diagram showing a configuration of a load short-circuit abnormality detection processing circuit which is a main part of the semiconductor switching device according to the embodiment.

FIG. 3 is a timing chart showing an operation of the load short-circuit abnormality detection processing circuit of FIG. 2;

FIG. 4 is a diagram for explaining specific setting of a resistance value of a resistance element for generating an overcurrent reference value in a load short-circuit abnormality detection processing circuit.

[Explanation of symbols]

 Reference Signs List 101 power supply 102 load 110 switching device 111 drive circuit 200 load short-circuit abnormality detection processing circuit 201 integration circuit 202 1 msec timer circuit 203 amplifying element 204 AND gate circuit 205 OR gate circuit 206 latch circuit CMP1 to CMP3 comparator QA Temperature sensor built-in FETs QB, QC FET QS Switching FET R11, R12 Resistance element SW1 Switch

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 5G004 AA04 AB02 BA03 BA04 CA05 DA04 DC04 DC07 DC12 EA01 5G053 AA01 AA02 BA01 BA04 CA02 EA03 EA09 EB02 EC03 FA05 5J055 AX12 AX15 AX32 AX56 AX64 BX16 CX22 DX53 DX53 EX02 EX04 EX06 EX11 EX24 EY01 EY02 EY03 EY10 EY12 EY13 EY17 EY21 EZ01 EZ07 EZ08 EZ10 EZ25 EZ31 EZ43 EZ55 FX04 FX32 FX33 FX38 GX01 GX02 GX04 GX05

Claims (4)

[Claims] A semiconductor switching element for turning on / off a power supply to a load; a current detection value for the load; and a first overcurrent reference value for determining an overcurrent state or determining a large overcurrent. Overcurrent detection means for detecting an overcurrent by comparing a second overcurrent reference value larger than the first overcurrent reference value, and the semiconductor switching when the current detection value is a large current larger than the second overcurrent reference value Overcurrent cutoff control for turning off the element is performed, and when the current detection value is higher than the first overcurrent reference value and lower than the second overcurrent reference value, the semiconductor switch is repeatedly turned on and off at a middle current to control the load. A semiconductor switching device, comprising: load current control means for performing current limit control for limiting current. 2. The overcurrent detection means according to claim 2, wherein when the detected current value exceeds the first overcurrent reference value and becomes an overcurrent state, the second overcurrent reference value causes an overcurrent of the large current for a first predetermined time. 2. The semiconductor switching device according to claim 1, wherein current detection is performed, and thereafter, overcurrent detection of a medium current is performed based on the first overcurrent reference value. 3. The semiconductor switching device according to claim 1, wherein said load current control means controls said semiconductor switching element to an off state after performing said on / off control repeatedly for a second predetermined time. . 4. The semiconductor switching device according to claim 1, wherein said semiconductor switching element, overcurrent detection means, and load current control means are implemented as a one-chip device.