JP2000293201A - Failure detection device - Google Patents

Abstract

(57) Abstract: An incomplete short circuit can be detected even when it occurs. A current flowing through a MOS transistor is detected by a mirror MOS transistor, a detection resistor, and a voltage amplifier. . The current flowing through the MOS transistor 10 is transferred to the mirror MOS transistor 10 and the detection resistor 11
And the voltage amplifier 12. The L failure detection circuit 13 compares the detected current values to determine the details of the failure. If the values are not the same, it is determined that an incomplete short circuit has occurred on the side of the smaller current value, and the control circuit 1 can stop the current flowing through the L load 5 based on the determination result. As described above, the failure judgment is made by comparing the current values. Therefore, if the detection resistor is formed in a small area on the IC chip, the relative accuracy of the resistance value can be maintained, the above detection can be performed, and an expensive external resistor or The device can be made without trimming the detection resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault detecting device for detecting a fault around a load in a drive circuit.

[0002]

2. Description of the Related Art As a driving circuit, for example, there is a driving circuit used for driving a switch reluctance motor. The switch reluctance motor is provided with a plurality of phases of windings, each of which is driven by an independent drive circuit. FIG. 4 is a diagram showing the configuration of the one-phase drive circuit. In this drive circuit 93, the MOS transistor 84 and the MOS transistor 86 are connected to both ends of an L load 85 as a winding, and a power supply connected to a power supply terminal 91 flows through the L load 85. The drive circuit 93 operates according to a control signal from the control circuit 81. Drive circuit 9
3 and a control circuit 81, a control system for a switched reluctance motor is formed. In order to improve the reliability of the entire control system, a failure detection circuit 92 is provided in a drive circuit 93 which outputs a large current as shown in FIG. Is generally performed.

The control system shown in FIG. 4 controls a three-phase switch reluctance motor, and the same drive circuit and fault detection circuit are connected to each phase. In the figure, only the W phase is shown for simplicity. The failure detection circuit 92 includes a mirror MOS 87 connected to the MOS transistor 86 and a detection resistor 88.
And a voltage amplifier 89 and an L failure detection circuit 90. The failure mode signal detected by the L failure detection circuit 90 is output to the control circuit 81.

When a control signal is output from the control circuit 81 to the drive circuit of each phase, the drive circuit operates, and a current flows through each phase winding of the motor in order, so that the motor rotates. Since the control system is configured as an integrated circuit, M
The OS transistor 86 is composed of a number of small MOS transistor cells formed on a substrate. Mirror M
The OS transistor 87 includes one or several MOS transistor cells. Assuming that the area ratio of these two transistors, that is, the ratio of the number of MOS transistor cells, is, for example, 100: 1, the ratio of the current values flowing through each becomes approximately 100: 1.

Here, it is assumed that when the MOS transistor 86 is on, both ends of the L load 85 are short-circuited and an excessive current flows. Then, a short-circuit current flows through MOS transistor 86. A short-circuit current also flows through the mirror MOS transistor 87 having the same operation as that of the MOS transistor 86, and a voltage higher than a normal value is generated across the detection resistor 88. This voltage is amplified by the voltage amplifier 89 and the L failure detection circuit 90
Is input to The L failure detection circuit 90 determines that an excessive current is flowing through the drive circuit 93 when the voltage becomes equal to or more than a certain value.

The following four failure modes can be considered by adding a control signal from a control circuit to a current value detected from a drive circuit. Failure mode 1: L load 85 internal short-circuit mode. Failure mode 2: a disconnection mode between points A and B at both ends of the L load 85 in FIG. Failure mode 3: a short-circuit mode between point A and point B and ground. Failure mode 4: Short-circuit mode between point A and point B and between the power supply.

In the failure mode 1, since an excessive current flows through the L load 85, the current can be detected and determined by the L failure detection circuit 90. Failure mode 2 is MOS
If the L failure detection circuit 90 detects that the current does not flow through the detection resistor 88 despite the ON signals being output to the transistors 84 and 86, it can be determined.
In the failure mode 3, as in the failure mode 2, an ON signal is output to the MOS transistors 84 and 86, and the detection resistor 8
8 can be determined by detecting that no current is flowing through the L failure detection circuit 90.

In the failure mode 4, the MOS transistor 8
Despite the off signal being output to 4, 86,
It can be determined by detecting that a current is flowing through the detection resistor 88 by the L failure detection circuit 90.

The L failure detection circuit 90 determines a failure around the load in the above four modes, and outputs a failure mode signal indicating which failure mode the control mode is to the control circuit 81. By receiving the failure mode signal, the control circuit 81 can perform a fail-safe operation such as stopping the operation of each phase or stopping power supply to the failed phase and moving only two phases in an emergency. Can be improved in reliability.

On the other hand, in the field of automobiles, as a recent trend, brake and throttle systems using an electromagnetic actuator (L load drive circuit) are being made by-wire. In this case, a fail-safe function such as failure detection is indispensable to ensure reliability, and further improvement in reliability is required.

If the control system described above is used, even if a failure occurs in the control system due to the fail-safe operation, a certain degree of emergency traveling is possible, so that it can be used as a vehicle travel actuator.

Further, in the application to automobiles (brake, throttle, etc.), the fail-safe function needs to be strengthened in order to further improve reliability. Therefore, in addition to the above four failure modes, as a failure mode requiring further detection, conduction with a certain resistance, that is, leakage of current, or conduction and non-conduction is repeated due to vibration or the like. Such a mode can be assumed.

[0013]

However, in order to cope with these new failure modes, the above-mentioned conventional control system has the following problems. That is, when the control system is considered from mass production, it is naturally necessary to consider the manufacturing variation of the elements constituting the circuit. For example, when the detection resistor 88 is made of a polysilicon thin film resistor, there is generally a variation of about 20% in absolute value. For this reason, if the actual current is flowing at 4 A, the variation width reaches ± 0.8 A, and the detected current value has a variation width of 3.2 A to 4.8 A.

As a result, for example, the MOS transistors 84 and 86 are controlled so that a current of 4 A flows as a current command, and the point A in FIG. 5 is short-circuited with a resistance between the grounds. If the leakage occurs, a current of 3.5 A flows through the detection resistor 88, and the control circuit 81 should determine that a failure has occurred, but the detected current value is 2.8A to 4.2.
A (3.5 A ± 0.7 A), which makes it impossible to make an accurate determination.

In order to increase the detection accuracy of the current value, it is necessary to take measures such as trimming the detection resistor or using an external high-precision resistor. The present invention has been made in view of the above problems,
It is an object of the present invention to provide an inexpensive failure detection device capable of accurately detecting failure contents.

[0016]

According to the present invention, a first switch means connected in series to one end of a load, and a second switch connected in series to the other end of the load. Means and a control circuit for turning on the first switch means and the second switch means to drive the load, the first circuit flowing through the first switch means.
First current detecting means for detecting a current value, second current detecting means for detecting a second current value flowing through the second switch means, comparing the first current value with the second current value, Failure detection means for detecting the failure content of the load or the first switch means or the second switch means, wherein the first current detection means and the second current detection means each have a detection resistor, The first current value and the second current value are detected based on a voltage between both ends of the detection resistor, and at least the detection resistor is formed in a close region on the same semiconductor substrate.

According to a second aspect of the present invention, the first switch means and the second switch means are each formed of a MOS transistor, and the first current detection means and the second current detection means are provided with respective detection resistors. Has a mirror MOS transistor and a voltage amplifier circuit.

According to a third aspect of the present invention, there is provided a first switch group including a third switch means and a fourth switch means connected in series with the third switch means; A sixth switch connected in series with the fifth switch means.
A second switch group comprising: a first switch group and a second switch group, wherein the first switch group and the second switch group are connected in parallel, and a connection point between the third switch means and the fourth switch means is provided. One end of the load is connected, the other end of the load is connected to a connection point between the fifth switch means and the sixth switch means, and the third switch means and the sixth switch means are simultaneously connected. By turning it on,
A second direction different from the first direction is applied to the load by flowing a current in the first direction to the load to drive the load, or simultaneously turning on the fourth switch means and the fifth switch means. A third current detecting means for detecting a third current value flowing through the third switch means and a fourth current value flowing through the fourth switch means in a control circuit for driving the load by flowing the current Fourth current detecting means, a fifth current detecting means for detecting a fifth current value flowing through the fifth switch means, and a sixth current detecting means for detecting a sixth current value flowing through the sixth switch means. And the third current value and the sixth current value or the fourth current value and the fifth current value are compared, and the load, the third switching means, the fourth switching means, or the fifth switch is compared. means Or a failure detecting means for detecting a failure content of the sixth switch means, wherein the third, fourth, fifth and sixth current detecting means each have a detecting resistor, and a voltage across the detecting resistor. Based on the third,
A semiconductor substrate that detects the fourth, fifth, and sixth current values and has at least the same detection resistor provided in the third and sixth current detection means or the same detection resistor provided in the fourth and fifth current detection means; It was formed in the upper adjacent area.

According to a fourth aspect of the present invention, the third switch means, the fourth switch means, the fifth switch means and the sixth switch means are each constituted by a MOS transistor, and the third current detecting means is provided. And a fourth current detecting means, a fifth current detecting means, and the sixth current detecting means, each of which is a mirror MOS connected to the respective detecting resistor.
It had a transistor and a voltage amplifier circuit.

[0020]

According to the first aspect of the present invention, since the detection resistors for detecting the first current value and the second current value are formed in adjacent regions on the same semiconductor substrate, the absolute value of the resistance value is determined. However, the first current value and the second current value detected based on the voltage across the detection resistor have high relative accuracy.

As a result, the failure detection for judging by comparing the first current value and the second current value can detect the failure with high accuracy. The failures include not only complete disconnection and short-circuit, but also failures such as short-circuit and disconnection having a resistance that could not be detected in the past due to variation in detection resistance. Further, it is possible to determine whether the failure site is on the power supply side or the ground side based on the sign of the comparison value. As described above, since the relative accuracy of the detection resistor is ensured by forming the detection resistor in a close area on the same semiconductor substrate, trimming of the detection resistor and use of external components are not required, and the apparatus can be configured at low cost. Can be.

According to the second aspect of the present invention, the first and second switch means are each constituted by a MOS transistor, and the first and second current detection means are respectively a mirror MOS transistor, a detection resistor and a voltage amplifier. Since it is constituted by a circuit, in addition to the effect of the first aspect of the present invention, the whole device can be easily formed as an integrated circuit, and the device becomes more inexpensive.

According to the third aspect of the present invention, a detection resistor for detecting at least the third current value and the sixth current value or the fourth current value and the fifth current value is provided in an adjacent region on the same semiconductor substrate. Therefore, even if there is a variation in the absolute value in manufacturing, the variation in the relative value is low, and therefore, the third value detected based on the voltage across the detection resistor.
The current value and the sixth current value or the fourth current value and the fifth current value have high relative accuracy.

As a result, the failure detection that is determined by comparing the third current value with the sixth current value or the fourth current value with the fifth current value can detect the failure with high accuracy. In addition to a complete short circuit or disconnection, failures such as a short circuit or disconnection having a resistance that could not be detected in the past due to variations in detection resistance can be detected. Further, it is possible to determine whether the failure site is on the power supply side or the ground side by the sign of the comparison value. As described above, since the relative accuracy of the detection resistor is ensured by forming the detection resistor in a close area on the same semiconductor substrate, trimming of the detection resistor and use of external components are not required, and the apparatus can be configured at low cost. Can be.

According to the present invention, the third, fourth, fifth and sixth switch means are respectively constituted by MOS transistors, and the third, fourth, fifth and sixth current detection means are provided. Are constituted by a mirror MOS transistor, a detection resistor and a voltage amplifier circuit, respectively. In addition to the effects of the third aspect of the present invention, the entire device can be easily configured as an integrated circuit, and the cost can be reduced. The device can be configured as follows.

[0026]

Next, embodiments of the present invention will be described with reference to examples. FIG. 1 is a diagram showing a configuration of a control system of a three-phase switched reluctance motor to which a failure detection circuit is attached. The drive circuit 15 is connected to the control circuit 1. The drive circuit 15 is connected to a failure detection circuit 16 as a failure detection device. A failure mode signal when the failure detection circuit 16 detects a failure is output to the control circuit 1.

The drive circuit 15 includes the MOS transistor 4
, MOS transistor 6, diode 2 and diode 3. The drain end of the MOS transistor 4 is connected to the power supply terminal 14, and the source end is connected to the cathode end of the diode 2 at point A. The anode end of the diode 2 is connected to the ground.

The source end of the MOS transistor 6 is connected to ground, and the drain end is connected to the anode end of the diode 3 at point B. The cathode end of diode 3 is connected to power supply terminal 14. Gate terminals of the MOS transistor 4 and the MOS transistor 6 are connected to the control circuit 1 as input terminals of the drive circuit 15. An L load 5 which is a W-phase winding of the three-phase switched reluctance motor is connected to points A and B, and a control signal for driving the W-phase is output from the control circuit 1 to the drive circuit 15.

The failure detection circuit 16 includes a mirror MOS transistor 7, a mirror MOS transistor 10, a detection resistor 8, a detection resistor 11, a voltage amplifier 9, a voltage amplifier 12, and an L failure detection circuit 13. To detect the current flowing through the MOS transistor 4 on the power supply side, the drain end of the mirror MOS transistor 7 is
The source end is connected to the detection resistor 8 at the drain end of the transistor 4.
Is connected to the source terminal of the MOS transistor 4. The gate end of the mirror MOS transistor 7 is
Connected to the gate end of S transistor 4. A voltage amplifier 9 is connected to both ends of the detection resistor 8. Note that a differential amplifier circuit generally composed of an operational amplifier and a resistor can be used as the voltage amplifier.

In order to detect a current flowing through the MOS transistor 6 on the ground side, the mirror MOS transistor 1
The drain end of the MOS transistor 6 is connected to the drain end of the MOS transistor 6, and the source end is connected to the source end of the MOS transistor 6 via the detection resistor 11. The gate terminal of the mirror MOS transistor 10 is connected to the gate terminal of the MOS transistor 6. A voltage amplifier 1 is connected between both ends of the detection resistor 11.
2 are connected.

The value of the current flowing through the MOS transistor 4 and the MOS transistor 6 is obtained as a voltage value by amplifying the voltage across the detection resistor by the voltage amplifier 9 and the voltage amplifier 12. The detected voltage value is output to the L failure detection circuit 13. The control signal of the control circuit 1 input to the drive circuit 15 is also output to the L failure detection circuit 13. The drive circuit 15 and the failure detection circuit 16 correspond to the W-phase winding. Similarly, the drive circuit 15 and the failure detection circuit 16 are provided for the U-phase and the V-phase.
It is omitted in the figure.

The above control system is configured as an integrated circuit on the same semiconductor substrate. FIG. 2 is a diagram showing a layout pattern of a failure detection portion. 21, 22, 23 are
U-phase, V-phase, and W-phase detection resistor formation regions on the power supply side; and 24, 25, and 26, U-phase, V-phase, and W-phase ground (ground) detection resistor formation regions. These resistors are arranged side by side in each phase.

As described above, since the detection resistor is formed in a small area close to each other, the relative variation is suppressed to be low even if the absolute value varies as the manufacturing variation. For example, when formed with a polysilicon resistor, a relative accuracy of about 2% can be obtained for the resistance value. Similarly, when forming U-phase, V-phase, and W-phase voltage amplifiers on an IC chip, the relative accuracy of the characteristics of the voltage amplifiers can be improved by arranging the operational amplifiers, which are components of the voltage amplifiers, close to each other. It is possible to keep.

Next, the operation of the control system will be described. A power supply is connected to the power supply terminal 14, and the control circuit 1 outputs a control signal of each phase of U, V, and W to each drive circuit according to a predetermined control program. In the drive circuit, the MOS transistor 4 and the MOS transistor 6 are turned on / off in accordance with the control signal, a current is supplied to the L load, a rotating magnetic field is generated in the motor, and the motor is driven.

The following four failure modes are set in the L failure detection circuit 13. Failure mode 1: L load internal short circuit mode. Failure mode 2: This is a disconnection mode from point A to point B at both ends of the L load 85 in FIG. Failure mode 3: Including short-circuit failure of diode 2, A
This is a short-circuit mode between the point B and the ground from the point. Failure mode 4: Including short-circuit failure of diode 3, A
This is a short-circuit mode between the point B and the power supply.

The detection resistor for detecting the current flowing through the MOS transistor is formed in a small area on the semiconductor substrate, and the relative accuracy of the current detection value is maintained. Failure detection such as conduction with a certain resistance or repetition of conduction and non-conduction due to vibration (the same state as having a certain resistance) is assumed and detected.
In the failure mode 4 as well, the failure is not assumed to be completely short-circuited as in the failure mode 3 but is assumed to be failure detection such as conduction with a certain resistance or conduction and non-conduction repeated due to vibration or the like. It has become.

Next, detection of a fault using the W phase will be described. In the following description, the current value detected from the power supply side is LH, and the current value detected from the ground side is LL.
And In the L failure detection circuit 13, the voltage amplifiers 9, 12
, The magnitudes of LH and LL are determined.
If LH and LL are the same and are larger than the drive current required by the control signal, it is determined that an excessive current has flowed into the L load 5 as a result of short-circuiting in the L load and a decrease in the internal resistance. A failure signal of mode 1 is output.

On the other hand, if the absolute values of LH and LL are detected to be 0 even though the control signal is an ON signal, no current flows through the L load 5, so that the point A And outputs a failure signal of failure mode 2 which is a disconnection.

When LL is zero but LH is detected to be flowing due to an overcurrent, the current flows from the power supply to the ground through the MOS transistor 4, and a short circuit occurs between the points A and B and the ground. It is determined that there is a failure to occur, and a failure signal of failure mode 3 is output.

In this failure mode 3, not a complete short circuit but a failure detection in which conduction with a certain resistance or conduction and non-conduction is repeated by vibration or the like is assumed, so LL is not zero. Even LH and LL
If the two current values are different from each other, it is determined that the failure is not a complete short circuit, but a failure in which conduction or non-conduction is repeated due to conduction or vibration due to a certain resistance. Outputs a failure signal. The fault includes a short-circuit fault of the diode 2.

When the L failure detection circuit 13 detects that the current value LH flowing through the MOS transistor 4 on the power supply side is zero, but detects that the current value LL on the ground side is an overcurrent, a short-circuit failure of the diode 3 is detected. It is determined that there is a short circuit between point A and point B and the power supply
Output a failure signal. In this mode, as in the failure mode 3, if LH is not zero, LL and LH are compared. If both detected values are detected not to be the same value, not a complete short circuit but a certain resistance. It determines that there is a state in which conduction or non-conduction is repeated due to conduction or vibration, and outputs a failure signal in failure mode 4.
Upon receiving the failure mode signal, the control circuit 1 determines the nature of the failure and performs a corresponding process. For example, it is possible to stop driving to a phase with a failure and perform driving in two phases to shift to a safe mode.

The embodiment is configured as described above, and it is possible to detect not a complete short circuit but a conduction state with a certain resistance or a state where conduction and non-conduction are repeated by vibration or the like. When there is a sign of failure, stop supplying power to the failed phase, and supply power only to the normal phase.
It becomes possible to drive the motor urgently.

As described above, a countermeasure can be taken before a complete short circuit occurs, and damage can be minimized as compared with a case where a complete short circuit is detected and taken. For example, if this embodiment is used for driving the injector of the engine, it is possible to stop the supply of power to the injector showing a sign of failure and to turn on the engine urgently by operating only the cylinder of the normal injector. As a result, a certain degree of emergency traveling is possible, and the reliability as an automobile is improved. Note that this function can be realized without costly trimming of the detection resistor or high-precision external resistor.

In this embodiment, the mirror MOS transistor 7, the detection resistor 8 and the voltage amplifier 9 are the first in the invention.
It constitutes current detection means. Mirror MOS transistor 1
0, the detection resistor 11 and the voltage amplifier 12 constitute the second current detection means in the present invention. The L failure detection circuit 13 constitutes failure detection means in the present invention. Voltage amplifier 9
And the voltage amplifier 12 constitute a voltage amplifying means in the present invention.

Next, a second embodiment will be described. FIG. 3 is a diagram illustrating the configuration of the embodiment. In this example,
An H-type bridge circuit is used as a drive circuit. H
The type bridge circuit includes a circuit 15A and a circuit 15B. The circuit 15A includes a MOS transistor 33, a MOS transistor 38, a diode 32, and a diode 37. On the other hand, the circuit 15B is a MOS transistor 4
3, a MOS transistor 48, a diode 42 and a diode 47.

The drain terminal of the MOS transistor 33 is connected to the power supply terminal 54, and the source terminal is connected to the anode terminal of the diode 32 at the point A. The cathode end of diode 32 is connected to power supply terminal 54. The drain end of the MOS transistor 38 is connected to the cathode end of the diode 37 at the point B, and the source end is connected to the ground. Diode 37
Is connected to the ground.

The drain terminal of the MOS transistor 43 is connected to the power supply terminal 54 and the source terminal thereof is connected to the anode terminal of the diode 42 at a point C. The cathode end of the diode 42 is connected to the power supply terminal 54. The drain end of the MOS transistor 48 is connected to the cathode end of the diode 47 at a point D, and the source end is connected to the ground. Diode 47
Is connected to the ground.

Point A and point B are connected to one end of L load 52, and point C and point D are connected to the other end of L load 52. MOS transistors 33, 38, 43, 48
Is connected to the control circuit 31 as an input terminal of the H-type bridge circuit.

A failure detection circuit 56 is connected to the H-type bridge circuit. The failure detection circuit 56 includes an L failure detection circuit 53 and a mirror MOS connected to each MOS transistor.
It consists of a transistor, a detection resistor and a voltage amplifier.
The drain end of the mirror MOS transistor 34 is connected to the drain end of the MOS transistor 33, and the source is connected to the source end of the MOS transistor 33 via the detection resistor 35. The gate end of the mirror MOS transistor 34 is connected to the gate end of the MOS transistor 33. A voltage amplifier 36 is connected to both ends of the detection resistor 35.

Mirror MOS transistors 39, 44, 4
9, a detection resistor 40, 45, 50 and a voltage amplifier 41,
46 and 51 are connected to the corresponding MOS transistors in the same manner as described above. Each voltage amplifier 36, 41, 46,
The output of 51 is output to the L failure detection circuit 53.

A power supply is connected to the power supply terminal 54 and the control circuit 3
1 is an ON signal to MOS transistors 33 and 48;
By outputting an off signal to the OS transistors 38 and 43, a current flows in the L load 52 in the direction indicated by the arrow 1. By outputting an ON signal to MOS transistors 38 and 43 and an OFF signal to MOS transistors 33 and 48, a current flows through L load 52 in the direction indicated by arrow 2.

The same four failure detection modes as those of the first embodiment are set in the L failure detection circuit 53. That is, failure mode 1: L load internal short circuit mode. Failure mode 2: This is a disconnection mode from the point A to the point D or the point B to the point C at both ends of the L load 52 in FIG. Failure mode 3: a short-circuit mode between point A to point D or point B to point C and ground. Failure mode 4: a short-circuit mode between the power supply and the point A to the point D or from the point B to the point C.

In the failure modes 3 and 4, short circuits each having a resistance are detected. Next, detection of a failure will be described. In the following description, the current value detected from the power supply side is LH, and the current value detected from the ground side is LL.

The L failure detection circuit 53 determines the MOS transistor to be turned on based on the control signal from the control circuit 31. In the case of the MOS transistor 33 and the MOS transistor 48, the detection values from the voltage amplifier 36 and the voltage amplifier 51 are used. Is used to determine the failure. First, the magnitudes of LH and LL are determined. If LH and LL are the same and are larger than the drive current required by the control signal, a short circuit occurs in the L load 52, and a failure mode 1 failure signal is output.

On the other hand, when the absolute values of LH and LL are detected to be 0, no current flows through the L load 52, so that a failure signal in failure mode 2 which is a disconnection from point A to point D is output. If LL is zero, but LH is detected to be flowing with an overcurrent, the current flows from the power supply to the ground through the MOS transistor 33, and a fault that shorts between the points A to D and the ground occurs. It is determined that there is, and a failure signal of failure mode 3 is output.

If LL is not zero, LH and L
The magnitudes of L are compared, and if the two current values are different, it is determined that the failure is not a complete short circuit but is a failure with conduction with a certain resistance or conduction and non-conduction repeated due to vibration, etc., and failure mode 3 Output a failure signal. This failure includes the failure of the diode 47.

When LH is zero, but LL has an overcurrent, A including A failure of the diode 32
It is determined that there is a short circuit between the point D and the power supply from the point, and a failure signal in failure mode 4 is output. If LH is not zero, LL and LH are compared. If the two detected values are not the same value, conduction is not complete short-circuit but conduction with some resistance, or conduction and non-conduction due to vibration, etc. It is determined that a repeated state exists, and a failure signal of failure mode 4 is output.

MOS turned on by L failure detection circuit 53
When it is determined that the transistors are the MOS transistor 38 and the MOS transistor 43, a failure is determined based on the detection values from the voltage amplifier 41 and the voltage amplifier 46. This is the same as above, and the fault location to be determined may be changed from A to C and from D to B.

In this embodiment, the H-type bridge circuit is used as the driving circuit as described above. However, as in the first embodiment, when the MOS transistors connected to both ends of the load become conductive, Since the determination is made by comparing the current values, exactly the same effects as in the first embodiment can be obtained.

In this embodiment, the mirror MOS transistor 34, the detection resistor 35 and the voltage amplifier 36 constitute the third current detecting means of the present invention. The mirror MOS transistor 39, the detection resistor 40, and the voltage amplifier 41 constitute a fourth current detection unit in the present invention. Mirror MOS
Transistor 44, detection resistor 45, and voltage amplifier 46
Constitute the fifth current detecting means in the present invention. The mirror MOS transistor 49, the detection resistor 50, and the voltage amplifier 51 constitute a sixth current detection unit in the present invention.
The L failure detection circuit 53 constitutes failure detection means in the present invention. The voltage amplifiers 36, 41, 46 and the voltage amplifier 51 constitute a voltage amplifying means in the present invention.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram of a three-phase switched reluctance motor showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a layout pattern of a detection resistor for detecting a current.

FIG. 3 is a control circuit diagram showing a second embodiment.

FIG. 4 is a diagram showing a conventional example of a control system to which a failure detection circuit is added.

[Explanation of symbols]

1, 31, 81 Control circuit 2, 3, 32, 37, 42, 47, 82, 83 Diode 4 MOS transistor (first switch means) 6 MOS transistor (second switch means) 33 MOS transistor (third switch) Switch means) 38 MOS transistor (fourth switch means) 43 MOS transistor (fifth switch means) 48 MOS transistor (sixth switch means) 53, 86, 84 MOS transistors 5, 52, 85 L load 7, 10 , 34, 39, 44, 49, 87 Mirror MOS transistor 8, 11, 35, 40, 45, 50, 88 Detection resistor 9, 12, 36, 41, 46, 51, 89 Voltage amplifier 13, 90 L fault detection circuit 14, 54, 91 Power supply terminal 15, 93 Drive circuit 16, 56, 92 Failure detection circuit 20 C chip 21 U-phase power supply side detection resistance formation area 22 V-phase power supply side detection resistance formation area 23 W-phase power supply side detection resistance formation area 24 U-phase ground side detection resistance formation area 25 V-phase ground side Detection resistor formation area 26 W-phase ground side detection resistance formation area 27 Operational amplifier formation area

Claims (4)

[Claims] 1. A first switch means connected in series to one end of a load, and a second switch means connected in series to the other end of the load.
And a control circuit for driving the load by turning on the first switch means and the second switch means to detect a first current value flowing through the first switch means. Current detecting means;
A second current detecting means for detecting a second current value flowing through the switch means, and comparing the first current value with the second current value to determine the load or the first switch means or the second switch. Failure detection means for detecting the failure content of the means, wherein the first current detection means and the second current detection means each have a detection resistor, and the first current value and the second current value are detected based on a voltage across the detection resistor. 2. A failure detection device for detecting a current value, wherein at least the detection resistor is formed in an adjacent region on the same semiconductor substrate. 2. The first switch means and the second switch means are each formed of a MOS transistor, and the first current detection means and the second current detection means are
2. The failure detection device according to claim 1, further comprising a mirror MOS transistor connected to each of said detection resistors and a voltage amplification circuit. 3. A first switch group comprising a third switch means and a fourth switch means connected in series with the third switch means, a fifth switch means and the fifth switch means. A second switch group consisting of a sixth switch unit connected in series, wherein the first switch group and the second switch group are connected in parallel, and the third switch unit and the fourth switch unit are connected in parallel. One end of the load is connected to a connection point with the switch means, and the other end of the load is connected to a connection point between the fifth switch means and the sixth switch means,
The third switch means and the sixth switch means are simultaneously turned on, so that a current flows in the load in a first direction to drive the load, or the fourth switch means and the fifth switch are driven. And a control circuit for driving the load by passing a current in the second direction different from the first direction to the load by simultaneously turning on the means and detecting a third current value flowing through the third switch means. Third current detecting means, fourth current detecting means for detecting a fourth current value flowing through the fourth switch means, and fifth current detecting means for detecting a fifth current value flowing through the fifth switch means. A sixth current detecting means for detecting a sixth current value flowing through the sixth switch means, and comparing the third current value with the sixth current value or the fourth current value with the fifth current value, Load or Failure detecting means for detecting the failure content of the third switch means, the fourth switch means, the fifth switch means, or the sixth switch means, wherein the third, fourth, fifth, and fifth failure means are detected. The sixth
The current detecting means has a detecting resistor and detects the third, fourth, fifth and sixth current values based on the voltage across the detecting resistor, and is provided in at least the third and sixth current detecting means. A fault detecting device, wherein the detected resistor or the detecting resistor provided in the fourth and fifth current detecting means is formed in a close area on the same semiconductor substrate. 4. The third switch means, the fourth switch means, the fifth switch means, and the sixth switch means are each formed of a MOS transistor, and the third current detection means and the fourth current detection are provided. 4. The fault detecting device according to claim 3, wherein the means, the fifth current detecting means, and the sixth current detecting means have a mirror MOS transistor and a voltage amplifier connected to the respective detecting resistors.