JP7238830B2 - load drive circuit - Google Patents

Description

The present invention relates to load driving circuits.

2. Description of the Related Art Conventionally, in a load drive circuit for driving an inductive load such as a solenoid, there is known a technique for monitoring an abnormality of a solenoid or a drive transistor.

For example, a solenoid load monitoring circuit disclosed in Patent Document 1 measures a potential difference across each solenoid connected in parallel to a battery. When the drive transistor connected between the solenoid and ground is OFF, the solenoid load monitoring circuit determines that the drive transistor has a leak failure if the potential difference across the solenoid is greater than the reference voltage.

JP-A-10-338125

In the circuit configuration of Patent Document 1, there is no current path bypassing each solenoid, and when a leakage failure of a drive transistor corresponding to a certain solenoid is detected, the energization to that solenoid cannot be cut off individually. Therefore, even if the drive transistors corresponding to some solenoids have a leak failure, it is necessary to stop supplying the battery voltage to all the solenoids at once, resulting in a complete loss of system functions.

In this specification, when a leakage current flows, it is expressed as "an inductive load has a leakage abnormality", not only when it is caused by the inductive load itself, but also when it is caused by wiring or elements corresponding to each inductive load. . Similarly, when the inductive load itself and corresponding wiring and elements are normal and no leakage current flows, it is expressed as "the inductive load is normal."

SUMMARY OF THE INVENTION The present invention was created in view of the above points, and its object is to drive normal inductive loads and continue at least some system functions in the case of minor leakage faults in some of the inductive loads. The object is to provide a drive circuit.

The present invention is a load drive circuit for driving multiple inductive loads (SL1-SL3) connected in parallel between a battery and ground. The inductive load is, for example, a solenoid or the like that opens and closes a valve by an electromagnetic attraction force generated by energizing a coil. Hereinafter, the battery side will be referred to as upstream, and the ground side will be referred to as downstream. This load drive circuit includes a safe relay (RY), a high side switch (TH), a low side switch (TL), a control circuit (44), and switch drive circuits (8H, 8L).

A safe relay is commonly provided for a plurality of inductive loads, and can cut off power supply from the battery to the plurality of inductive loads. A high-side switch is connected in parallel with each inductive load between the upstream end and the downstream end of each inductive load, and switches conduction and interruption of the current path. A low-side switch is connected between the downstream end of each inductive load and the ground, and switches conduction and interruption of the current path.

The control circuit generates switching signals for the high-side switch and the low-side switch, and determines in the initial check after starting the load drive circuit whether or not there is a leak abnormality in which a leak current flows from the downstream end of each inductive load to the ground. do. The switch drive circuit switches ON/OFF of the high side switch and the low side switch according to the switching signal.

The control circuit turns ON the safe relay, turns ON the high side switch corresponding to each inductive load, and turns OFF the low side switch in the first judgment stage of the initial check, and judges whether or not there is a leakage abnormality. do. When the control circuit determines that one or more inductive loads have a leak abnormality in the first determination stage, the second determination stage of the initial check determines whether the leak current is within the allowable range and is a "minor leak abnormality". , to determine whether the leakage current exceeds the allowable range or not is an “intrinsic leakage abnormality”. For example, "slight leakage abnormality" refers to a state in which a leakage current that does not pose a problem for the withstand current performance of the switch is flowing.

When the control circuit determines that there is a minor leak abnormality, the control circuit prohibits driving the inductive load determined to be abnormal while maintaining the ON state of the high-side switch and the OFF state of the low-side switch in the first determination stage, Permits driving an inductive load that is determined to be normal. Further, when the control circuit determines that there is an intrinsic leak abnormality, it turns off the safe relay and prohibits driving of all the inductive loads.

In the present invention, by turning on the high-side switch at the time of the initial check, it is possible to prevent the leakage current from flowing through the inductive load to be judged and the occurrence of malfunction or the like. In addition, by prohibiting the driving of only the inductive loads that are judged to be abnormal and permitting the driving of the inductive loads that are judged to be normal in the event of a minor leak abnormality, it is possible to avoid the complete loss of system functions and at least partially system functions can continue. In addition, by prohibiting the driving of all inductive loads at the time of the intrinsic leakage abnormality, it is possible to reliably realize a fail-safe.

FIG. 2 is a circuit configuration diagram of the load drive circuit according to the first embodiment; 4 is a flowchart of leak abnormality determination processing according to the first embodiment; FIG. 4 is a circuit configuration diagram of a load drive circuit according to a second embodiment; 9 is a flowchart of leak abnormality determination processing according to the second embodiment; The circuit block diagram of the load drive circuit by 3rd Embodiment. 10 is a flowchart of leak abnormality determination processing according to the third embodiment;

A plurality of embodiments of the load drive circuit according to the present invention will be described below with reference to the drawings. In a plurality of embodiments, substantially the same configurations are denoted by the same reference numerals, and descriptions thereof are omitted. The first to third embodiments are collectively referred to as "this embodiment". In this embodiment, the plurality of "inductive loads" to be driven by the load drive circuit are, for example, a plurality of solenoids constituting control valves for opening and closing hydraulic paths in a hydraulic brake system of a vehicle.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2. FIG. First, FIG. 1 shows the overall configuration of a plurality of solenoids SL1, SL2, and SL3 (hereinafter referred to as “plurality of solenoids SL1-SL3”) to be driven by the load drive circuit and the load drive circuit 40. As shown in FIG. It is meaningless that the number of solenoids is three in FIG. 1, and the number may be two or four or more. A plurality of solenoids SL1-SL3 are connected in parallel between a battery (not shown) and ground, and are commonly applied with a battery voltage Vb. Hereinafter, the battery side will be referred to as "upstream" and the ground side will be referred to as "downstream."

A load drive circuit 40 drives a plurality of solenoids SL1-SL3. The load drive circuit 40 includes a safe relay RY and a control circuit 44 commonly provided for all the solenoids SL1-SL3, and first to third solenoid drive circuits provided individually for each of the solenoids SL1-SL3. . 1 corresponds to the load driving circuit 40 except for the plurality of solenoids SL1 to SL3 in FIG. A safe relay RY can cut off the power supply from the battery to the plurality of solenoids SL1-SL3.

In the first embodiment, the reference numerals of the first to third solenoid drive circuits are "461", "462" and "463". A detailed configuration of the first solenoid drive circuit 461 is illustrated. The second and third solenoid drive circuits 462 and 463 simply represent that a plurality of circuits having the same configuration as the first solenoid drive circuit 461 are provided, and detailed illustration is omitted.

In the following description, the first to third solenoid drive circuits of the first embodiment are represented by "solenoid drive circuit 461". In this case, it means "one unit drive circuit for one solenoid". Also, the solenoid to be driven is represented by "solenoid SL1". The solenoid drive circuit 461 includes a high-side switch TH, a low-side switch TL, current sensors 5H and 5L, current detection circuits 6H and 6L, and switch drive circuits 8H and 8L corresponding to the switches TH and TL.

The high-side switch TH is connected in parallel with the solenoid SL1 between the upstream end and the downstream end of the solenoid SL1, and switches between conduction and interruption of the current path. The low-side switch TL is connected between the downstream end of the solenoid SL1 and the ground, and switches between conduction and interruption of the current path.

The switch drive circuits 8H and 8L switch ON/OFF of the high side switch TH and the low side switch TL, respectively, according to the switching signal generated by the control circuit 44 . As common technical knowledge for preventing short circuits, the high side switch TH and the low side switch TL are never turned on at the same time. When the high side switch TH is ON and the low side switch TL is OFF, the solenoid SL1 is not energized and is in a non-driven state. When the high side switch TH is OFF and the low side switch TL is ON, the solenoid SL1 is energized. That is, the solenoid SL1 is driven.

A current flowing through the high-side switch TH is defined as a "high-side current IH", and a current flowing through the low-side switch TL is defined as a "low-side current IL". A high-side current sensor 5H and a low-side current sensor 5L detect a high-side current IH and a low-side current IL, respectively. The high-side current detection circuit 6H and the low-side current detection circuit 6L process the output signals of the corresponding current sensors 5H and 5L and output them to the control circuit 44 .

In normal driving, the control circuit 44 generates switching signals for the high-side switch TH and the low-side switch TL by duty control, for example, based on an external command signal. At this time, feedback currents IH and IL may be obtained from the current detection circuits 6H and 6L to perform current feedback control. The control circuit 44 also commands opening and closing of the safe relay RY.

By the way, in the load drive circuit 40 having such a configuration, there is a possibility that a leak current flows from the downstream end of the solenoid SL1 to the ground. As the leakage paths, as indicated by broken lines in FIG. 1, a path LPa flowing from the downstream end of the solenoid SL1 to the ground and a path LPb flowing inside the low-side switch TL are assumed.

Therefore, after starting the load driving circuit 40, it is required to detect the leak abnormality by an initial check before starting the normal driving. Therefore, in the initial check, the control circuit 44 of the present embodiment determines whether or not there is a leakage abnormality in which a leakage current flows from the downstream ends of the solenoids SL1 to SL3 to the ground.

In this specification, when a leak current flows not only due to the solenoid itself, but also due to wiring corresponding to each solenoid or low side switch TL, it is expressed as "solenoid leak abnormality". Similarly, when the solenoid itself, the corresponding wiring and the low-side switch TL are normal and no leakage current flows, it is expressed as "the solenoid is normal".

In the prior art of Patent Document 1 (Japanese Patent Application Laid-Open No. 10-338125), it is necessary to cut off the voltage supply to all the solenoids at once as a measure even if some of the plurality of solenoids have a leak abnormality. Complete loss of system functionality.

On the other hand, the load drive circuit 40 of the present embodiment, when it is determined that there is a leakage abnormality, distinguishes between a "minor leakage abnormality" that is substantially within the allowable range and a "genuine leakage abnormality" that exceeds the allowable range. Then, in the case of a minor leakage abnormality in some solenoids, the purpose is to drive the normal solenoids and continue at least some system functions.

In the first embodiment, the control circuit 44 determines whether there is a leak abnormality in each solenoid SL1-SL3 based on the high-side current IH detected by the current sensor 5H and the output signal processed by the current detection circuit 6H. Furthermore, it determines whether it is a minor leak abnormality or a true leak abnormality.

In the solenoid drive circuit 461 of the first embodiment, it is assumed that the low-side current sensor 5L and the current detection circuit 6L are not used for leak abnormality determination in the initial check, but are used only for feedback control during normal driving. there is Although it is possible to distinguish between the leak path LPa and the leak path LPb based on the low-side current IL, it is not assumed in the first embodiment because there is no realistic need for this.

A leak abnormality determination process according to the first embodiment will be described with reference to the flowchart of FIG. In the description of the flowchart, the symbol "S" means step. S1-S4 correspond to the "first determination stage of the initial check", and S5-S7 correspond to the "second determination stage of the initial check". S8-S10 are measures according to the determination result. Steps other than S3 and S5 are common in the first to third embodiments, and the meanings of the first determination stage and the second determination stage are also common. As for S3 and S5, the symbols "A", "B" and "C" corresponding to each embodiment are added at the end.

The control circuit 44 turns ON the safe relay RY in S1, turns ON the high side switch TH corresponding to each solenoid SL1-SL3, and turns OFF the low side switch TL in S2. In this state, the control circuit 44 determines in S3A whether or not the high-side current IH is equal to or greater than the first current threshold IHth1. The first current threshold IHth1 is set to the upper limit of the error range with respect to 0 [A]. That is, "the high-side current IH is equal to or greater than the first current threshold IHth1" means "the high-side current IH is not substantially 0 [A]".

Hereinafter, the solenoid subject to abnormality determination will be referred to as "subject solenoid SL1". Also, the other solenoids SL2 and SL3 are assumed to be normal. If NO in S3A, in S4 the control circuit 44 determines that the high-side current IH is substantially 0 [A] and that the subject solenoid SL1 is normal. Then, in S8, the control circuit 44 starts normal driving of the target solenoid SL1 by duty control or the like. If YES in S3A, the control circuit 44 determines that the subject solenoid SL1 has a leak abnormality, and proceeds to S5A.

In the second determination step S5A, the control circuit 44 determines whether or not the high side current IH is equal to or greater than the second current threshold IHth2. The second current threshold IHth2 is a value greater than the first current threshold IHth1. For example, if a current equal to or greater than the second current threshold IHth2 continues to flow, the second current may exceed the withstand current value of the high-side switch TH and the low-side switch TL when the leak current flows through the path LPb. It is set as the threshold IHth2. That is, from the standpoint of the withstand current of the switches TH and TL, when a leakage current equal to or greater than the second current threshold IHth2 flows, it is treated as an intrinsic leakage abnormality. On the other hand, even if a current less than the second current threshold IHth2 continues to flow, there is no problem with the current resistance performance of the switches TH and TL, so in this case, it is treated as a minor leakage abnormality.

In short, the second current threshold IHth2 corresponds to "the upper limit of the allowable range of leakage current". In the second determination stage, the control circuit 44 determines whether it is a "minor leak abnormality" in which the leak current is within the allowable range or a "true leak abnormality" in which the leak current exceeds the allowable range.

When the high-side current IH is smaller than the second current threshold IHth2, that is, when NO in S5A, the control circuit 44 determines in S6 that the subject solenoid SL1 has a "minor leak abnormality". In S9, the control circuit 44 continues the "ON state of the high-side switch TH and the OFF state of the low-side switch TL" in the first determination stage and prohibits driving the target solenoid SL1 determined to be abnormal. Also, the control circuit 44 permits the driving of the other solenoids SL2 and SL3 determined to be normal.

When the high-side current IH is equal to or greater than the second current threshold IHth2, that is, when YES in S5A, the control circuit 44 determines in S7 that the subject solenoid SL1 has an "intrinsic leak abnormality". Then, in S10, the control circuit 44 turns off the safe relay RY to prohibit driving of all the solenoids SL1-SL3.

As described above, in the present embodiment, by turning on the high-side switch TH at the time of the initial check, it is possible to prevent the leakage current from flowing through the target solenoid SL1 and the occurrence of malfunction or the like.

In addition, by prohibiting the driving of only the target solenoid SL1 determined to be abnormal in the event of a minor leak abnormality and permitting the driving of the other solenoids SL2 and SL3 determined to be normal, it is possible to avoid a complete loss of system functions. and at least some system functionality can continue. For example, even if one of the control valves that open and close the brake hydraulic paths for four wheels malfunctions, the other three can be driven normally. In addition, by prohibiting the driving of all the solenoids SL1-SL3 at the time of the intrinsic leak abnormality, it is possible to reliably realize a fail-safe.

Furthermore, in the first embodiment, the high-side current IH is acquired by the configuration of the current sensor 5H and the current detection circuit 6H used for current feedback control in normal driving to determine a leak abnormality. No configuration is required. Therefore, it can be easily applied to the existing load driving circuit 40 as well. Further, the detection method based on current generally has better detection accuracy than the detection method based on potential difference.

(Second and third embodiments)
Next, a second embodiment will be described with reference to FIGS. 3 and 4. FIG. As shown in FIG. 3, in the second embodiment, the reference numerals of the first to third solenoid drive circuits are "471", "472", and "473". A detailed configuration of the first solenoid drive circuit 471 is illustrated. The second and third solenoid drive circuits 472 and 473 simply represent that a plurality of circuits having the same configuration as the first solenoid drive circuit 471 are provided, and detailed illustration is omitted. Only the symbols of the high side potential difference comparison circuits 71H and 72H are added to the second and third solenoid drive circuits 462 and 463 of FIG.

The first to third solenoid drive circuits of the second embodiment are represented by "solenoid drive circuit 471". Also, the potential difference between the upstream end and the downstream end of the high side switch TH is defined as "high side potential difference VH". A solenoid drive circuit 471 of the second embodiment has, in addition to the configuration of the solenoid drive circuit 461 of the first embodiment, two high side potential difference comparison circuits 71H and 72H that compare the high side potential difference VH with a threshold. The high-side potential difference VH is also the potential difference generated across the solenoid SL1 when the solenoid SL1 is not driven.

The first high side potential difference comparison circuit 71H compares the high side potential difference VH with the first high side potential difference threshold VHref1. The first high-side potential difference threshold VHref1 is used in the first judgment stage for judging whether or not there is a leakage abnormality. The second high side potential difference comparison circuit 72H compares the high side potential difference VH with a second high side potential difference threshold VHref2. The second high-side potential difference threshold VHref2 is set to a value greater than the first high-side potential difference threshold VHref1, and is used in the second determination stage for determining whether the leakage is minor or true.

The flowchart of FIG. 4 differs from that of FIG. 2 only in S3B and S5B. For other steps, the description of the first embodiment is used. In the first determination step S3B, the control circuit 44 determines whether or not the high side potential difference VH is equal to or greater than the first high side potential difference threshold value VHref1. The first high-side potential difference threshold VHref1 is set to the value of the high-side potential difference VH generated when a leakage current corresponding to the first current threshold IHth1 in FIG. 2 flows. If YES in S3B, the control circuit 44 determines that the subject solenoid SL1 has a leak abnormality, and proceeds to S5B.

In the second determination step S5B, the control circuit 44 determines whether or not the high side potential difference VH is equal to or greater than the second high side potential difference threshold value VHref2. The second high-side potential difference threshold VHref2 is set to the value of the high-side potential difference VH generated when a leakage current corresponding to the second current threshold IHth2 shown in FIG. 2 flows.

When the high side potential difference VH is smaller than the second high side potential difference threshold value VHref2, that is, when NO in S5B, the control circuit 44 determines in S6 that the subject solenoid SL1 has a "minor leak abnormality". When the high-side potential difference VH is equal to or greater than the second high-side potential difference threshold VHref2, that is, when YES in S5B, the control circuit 44 determines in S7 that the subject solenoid SL1 has an "intrinsic leak abnormality".

Next, a third embodiment will be described with reference to FIGS. 5 and 6. FIG. As shown in FIG. 5, in the third embodiment, the reference numerals of the first to third solenoid drive circuits are "481", "482" and "483". A detailed configuration of the first solenoid drive circuit 481 is illustrated. The second and third solenoid drive circuits 482 and 483 simply represent that a plurality of circuits having the same configuration as the first solenoid drive circuit 481 are provided, and detailed illustration is omitted. Only symbols of low-side potential difference comparison circuits 71L and 72L are added to the second and third solenoid drive circuits 462 and 463 of FIG.

The first to third solenoid drive circuits of the third embodiment are represented by "solenoid drive circuit 481". Also, the potential difference between the upstream end and the downstream end of the low-side switch TL is defined as "low-side potential difference VL". The solenoid drive circuit 481 of the third embodiment has, in addition to the configuration of the solenoid drive circuit 461 of the first embodiment, two low-side potential difference comparison circuits 71L and 72L that compare the low-side potential difference VL with a threshold. For example, in a circuit in which a resistor or the like is connected between the low-side switch TL and the ground, a threshold may be set in consideration of a voltage drop caused by the resistor or the like.

The first low-side potential difference comparison circuit 71L compares the low-side potential difference VL with a first low-side potential difference threshold VLref1. The first low-side potential difference threshold VLref1 is used in the first judgment stage for judging whether or not there is a leakage abnormality. The second low-side potential difference comparison circuit 72L compares the low-side potential difference VL with a second low-side potential difference threshold VLref2. The second low-side potential difference threshold VLref2 is set to a value smaller than the first low-side potential difference threshold VLref1, and is used in the second determination stage for determining whether the leakage is minor or true.

The flowchart of FIG. 6 differs from that of FIG. 2 only in S3C and S5C. For other steps, the description of the first embodiment is used. In the first determination step S3C, the control circuit 44 determines whether the low-side potential difference VL is equal to or less than the first low-side potential difference threshold VLref1. The first low-side potential difference threshold VLref1 is set to the value of the low-side potential difference VL generated when a leakage current corresponding to the first current threshold IHth1 shown in FIG. 2 flows. If YES in S3C, the control circuit 44 determines that the subject solenoid SL1 has a leak abnormality, and proceeds to S5C.

In the second determination step S5C, the control circuit 44 determines whether or not the low side potential difference VL is equal to or less than the second low side potential difference threshold VLref2. The second low-side potential difference threshold VLref2 is set to the value of the low-side potential difference VL generated when a leak current corresponding to the second current threshold IHth2 shown in FIG. 2 flows.

When the low-side potential difference VL is greater than the second low-side potential difference threshold VLref2, that is, when NO in S5C, the control circuit 44 determines in S6 that the subject solenoid SL1 has a "minor leak abnormality". When the low-side potential difference VL is equal to or less than the second low-side potential difference threshold VLref2, that is, when YES in S5C, the control circuit 44 determines in S7 that the subject solenoid SL1 has an "intrinsic leak abnormality".

As described above, in the second and third embodiments, the leakage abnormality of the target solenoid SL1 is determined based on the potential difference between both ends of the high-side switch TH or the low-side switch TL. As a result, the same effects as in the first embodiment can be obtained.

In the solenoid drive circuits 471 and 481 of the second and third embodiments, the current sensors 5H and 5L and the current detection circuits 6H and 6L are not used in the leak abnormality judgment of the initial check. However, since it is used for feedback control or the like during normal driving, it is shown in FIGS. 3 and 5 in the same manner as in FIG.

(Other embodiments)
(a) The control circuit 44 may use both the high-side current IH and the potential difference VH, VL across the high-side switch TH or the low-side switch TL to determine the leakage abnormality. Reliability is improved by combining multiple determinations.

(b) In addition to the two-stage threshold for determining leak abnormality, thresholds of three or more stages may be provided to further classify minor leak abnormality or true leak abnormality, and measures may be taken according to the level.

(c) The inductive load to be driven by the load drive circuit is not limited to a solenoid that opens and closes a valve by electromagnetic attraction, but may be any load having an inductance component such as a transformer or motor windings. In addition, the configuration is not limited to the configuration in which the same type of inductive loads are connected in parallel, and different types of inductive loads having the same drive current may coexist.

As described above, the present invention is not limited to such an embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

The control circuitry and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by the computer program. may be Alternatively, the control circuitry and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control circuitry and techniques described in this disclosure can be implemented by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may also be implemented by one or more dedicated computers configured. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium.

40 Load drive circuit 44 Control circuit 8H, 8L Switch drive circuit
SL1-3 ... Solenoid (inductive load),
RY: Safe relay,
TH: high side switch, TL: low side switch.

Claims (3)

A load driving circuit for driving a plurality of inductive loads (SL1-SL3) connected in parallel between a battery and ground, wherein the battery side is represented as upstream and the ground side is represented as downstream,
a safe relay (RY) that is commonly provided for a plurality of the inductive loads and is capable of interrupting power supply from the battery to the plurality of the inductive loads;
a high-side switch (TH) connected in parallel with each of the inductive loads between the upstream end and the downstream end of each of the inductive loads and switching between conduction and interruption of the current path;
a low-side switch (TL) connected between the downstream end of each of the inductive loads and the ground and switching between conduction and interruption of the current path;
generating switching signals for the high-side switch and the low-side switch, and determining presence/absence of a leakage abnormality in which a leakage current flows from the downstream end of each of the inductive loads to the ground in an initial check after starting the load drive circuit; a control circuit (44);
a switch drive circuit (8H, 8L) for switching ON/OFF of the high side switch and the low side switch according to the switching signal;
with
The control circuit is
In the first determination stage of the initial check, whether or not the leak abnormality occurs in a state where the safe relay is turned on, the high side switch corresponding to each inductive load is turned on, and the low side switch is turned off. to determine
If one or more of the inductive loads are determined to be the leakage abnormality in the first determination step, the second determination step of the initial check determines whether the leakage current is within the allowable range and the leakage abnormality is minor, Determining whether the leak current is an intrinsic leak abnormality exceeding the allowable range,
When it is determined that the minor leak abnormality is present,
For the inductive load determined to be abnormal, driving of the inductive load determined to be normal is prohibited while the high-side switch ON state and the low-side switch OFF state in the first determination stage are continued. to allow
When it is determined to be the intrinsic leak abnormality,
A load drive circuit that turns off the safe relay and prohibits driving of all the inductive loads. A high side current sensor (5H) that detects a high side current (IH) that flows through the high side switch, and a high side current detection circuit (6H) that processes an output signal of the high side current sensor. ,
The control circuit determines that the leak abnormality occurs when the high-side current is equal to or greater than a first current threshold (IHth1) in the first determination step, and determines that the high-side current is equal to or exceeds the first current threshold (IHth1) in the second determination step. 2. The load driving circuit according to claim 1, wherein when the current is smaller than a second current threshold (IHth2) larger than one current threshold, the minor leakage abnormality is determined, and when the current is equal to or greater than the second current threshold, the intrinsic leakage abnormality is determined. The high side potential difference (VH), which is the potential difference between the upstream end and the downstream end of the high side switch, is set to a first high side potential difference threshold (VHref1) and a second high side potential difference threshold (VHref1) larger than the first high side potential difference threshold ( VHref2), a high side potential difference comparison circuit (71H, 72H) for comparison, or
A low-side potential difference (VL), which is a potential difference between the upstream end and the downstream end of the low-side switch, is compared with a first low-side potential difference threshold (VLref1) and a second low-side potential difference threshold (VLref2) smaller than the first low-side potential difference threshold. Further comprising a low side potential difference comparison circuit (71L, 72L),
When the high-side potential difference comparison circuit is provided,
The control circuit determines that the leakage abnormality occurs when the high-side potential difference is equal to or greater than the first high-side potential difference threshold in the first determination step, and determines that the high-side potential difference is equal to or greater than the first high-side potential difference threshold in the second determination step. determining that the leakage abnormality is minor when the potential difference is smaller than the second high-side potential difference threshold, and that the leakage abnormality is true when the potential difference is equal to or greater than the second high-side potential difference threshold;
When the low-side potential difference comparison circuit is provided,
The control circuit determines that the leakage abnormality occurs when the low-side potential difference is equal to or less than the first low-side potential difference threshold in the first determination step, and determines that the low-side potential difference is equal to or exceeds the second low-side potential difference in the second determination step. 2. The load driving circuit according to claim 1, wherein the minor leakage abnormality is determined when the potential difference is greater than a threshold, and the intrinsic leakage abnormality is determined when the potential difference is equal to or less than the second low-side potential difference threshold.

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