High-side switch circuit with self-diagnosis function

Abstract

The application belongs to the technical field of high-side power output control, and particularly relates to a high-side switch circuit with a self-diagnosis function. The high-side switch circuit comprises a high-side switch, a self-diagnosis circuit and a control unit. When the control unit receives an instruction to turn on the high-side switch, the control unit sends a diagnosis start instruction to the self-diagnosis circuit to perform a load type judgment process. When the load type is a capacitive load or an inductive load, the load is pre-charged to reduce current impact when the high-side switch is turned on. By setting the high-side switch circuit comprising the self-diagnosis circuit, the load can be preliminarily diagnosed before the high-side switch circuit is turned on. When the load is an inductive load or a capacitive load, pre-charging is performed to reduce current impact when the high-side switch is turned on. Thus, the phenomenon of excessive current of the high-side switch circuit at the moment of turning on is avoided due to the load, and the problem of over-current false protection is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-side power output control, and particularly relates to a high-side switch circuit with a self-diagnosis function. BACKGROUND

[0002] The high-side switch in the high-side switch circuit is usually a MOSFET (metal oxide semiconductor field effect transistor), which has the advantages of small conduction impedance, no electric spark, small size and the like, and is widely used in automobile parts to replace traditional relay circuits. To prevent the MOSFET from being damaged in a fault mode, semiconductor manufacturers use a MOSFET combined with a short-circuit protection circuit, an overcurrent protection circuit and an overheat protection circuit to uniformly package the MOSFET to form a high-side switch, so that when the current or temperature exceeds a threshold value, the high-side switch immediately starts a self-protection function to close the output channel. Under normal circumstances, the protection mechanism can effectively protect the high-side switch from being burned by a short-circuit current, but when a capacitive load or an inductive load is driven, because the impact current is too large when the back-end load is started, the protection threshold of the high-side switch is easily broken, the overcurrent protection of the high-side switch is triggered, and thus the load cannot be normally started. In addition, under the condition that the load circuit is short-circuited, the high-side switch is opened, even if the protection function of the protection mechanism is effective and the MOSFET is closed, the short-circuit impact current has caused irreversible damage to the MOSFET, seriously affecting the service life of the high-side switch, and when the short-circuit capacity is large enough, the high-side switch is directly damaged, resulting in serious failure of the vehicle function.

[0003] To solve the problem, the main solution in the industry is to use multiple high-side switches in parallel to use other high-side switches when a high-side switch in one branch fails to enhance the output capacity. However, this method has the disadvantage that the protection performance is reduced after parallel connection due to the discreteness of the characteristics of components. SUMMARY

[0004] The application aims to provide a high-side switch circuit with a self-diagnosis function to solve the problem of false protection of the high-side switch control circuit with a protection function in the prior art.

[0005] To solve the above technical problems, the application provides a high-side switch circuit with a self-diagnosis function, comprising a high-side switch and a control unit, the high-side switch is arranged between a power supply and a load, the control unit controls the high-side switch to control the on-off of the high-side switch, and the high-side switch circuit further comprises a self-diagnosis circuit, the self-diagnosis circuit comprises a signal acquisition circuit and a driving circuit, the driving circuit comprises a driving switch and a current-limiting resistor which are connected in series between the power supply and the load and are connected in parallel with the high-side switch, and the driving switch is connected to the control unit; the acquisition circuit comprises a power supply end voltage detection port and a load end voltage detection port, the power supply end voltage detection port is connected to the control unit through a power supply end acquisition circuit, and the load end voltage detection port is connected to the control unit through a load end acquisition circuit.

[0006] The control unit is used for sending a diagnosis start instruction to the driving switch to control the driving switch when receiving a start instruction of the high-side switch, so as to realize the conduction or block of the power supply of the circuit in which the driving switch is located to the load, and the power supply end voltage signal and the load end voltage signal are acquired after the diagnosis start, and the load type is judged according to the power supply end voltage signal and the load end voltage signal, and the pre-charging treatment is performed when the load type is an inductive load type or a capacitive load type, so as to reduce the current impact when the high-side switch circuit is started.

[0007] The high-side switch circuit provided by the application can preliminarily diagnose the load before the high-side switch circuit is started, and the pre-charging treatment of the corresponding load is required when the diagnosis result is an inductive load or a capacitive load, so that there is no current impact when the high-side circuit is started, and the phenomenon that the current of the high-side switch circuit is too large at the moment of starting due to the load is avoided, and the problem of overcurrent false protection is avoided.

[0008] Further, when the load type is an inductive load type or a capacitive load type, the pre-charging treatment is that the control unit controls the driving circuit of the self-diagnosis circuit to be conducted for a set time.

[0009] When the load type is an inductive load type or a capacitive load type, the pre-charging treatment is performed on the load to reduce the capacity of the load, so as to avoid the existence of impact current when the high-side switch circuit is started, affect the normal starting of the high-side switch circuit, and avoid the false protection of the overcurrent protection circuit of the high-side switch circuit, and the pre-charging treatment is performed by using the driving circuit of the self-diagnosis circuit, so as to avoid the cost of setting the pre-charging circuit again.

[0010] Further, the diagnostic control is to control the drive switch to open for a set first time, and then control the drive switch to close for a set second time; the power end voltage signal comprises: an average value V ad1 of the power end voltage signal in the first time period ad4 , and an average value V ad2 of the power end voltage signal in the second time period ad3 .

[0011] Because the voltage data when the circuit is opened and closed are different due to different load types, by collecting the voltage data when the diagnostic circuit is opened and closed, and by averaging the voltage data when opened and the voltage data when closed, the specific load type can be analyzed.

[0012] Further, the basis for judging the load type according to the power end voltage signal and the load end voltage signal is:

[0013] If V ad1 -V ad2 >V diff , V ad2 >V min , and V ad3 >V min , it is judged as a capacitive load.

[0014] If V ad1 -V ad2 <V diff , V ad2 >V min , and V ad3 <V min , V ad4 -V ad3 >V diff , it is judged as an inductive load.

[0015] Wherein, V min is a low voltage threshold value of the high-side switch output end, and V diff is a voltage difference threshold value of the high-side switch.

[0016] Further, the load type further comprises an open circuit load type and a short circuit load type; when the load type is the open circuit load type or the short circuit load type, the control unit refuses to execute the open high-side switch instruction, and sends an alarm information to the open high-side switch instruction issuing unit.

[0017] When the external load is short-circuited or open-circuited, that is, the external load is faulty, the instruction of turning on the high-side switch circuit is not executed, and the external load fault information is sent to the command issuing unit, so that when the external load is faulty, the high-side switch circuit is prevented from being turned on to cause damage to the high-side switch circuit or the load, and the process of reliably controlling the high-side switch circuit is ensured, that is, the irreversible damage of the MOSFET caused by the short-circuit impact current after the high-side switch circuit is turned on in the prior art is avoided, the service life of the high-side switch is seriously affected, when the short-circuit capacity is large enough, the high-side switch is directly damaged, the vehicle function is seriously disabled, and then the command of turning on the high-side switch circuit by the external load is refused by the control unit when the external load is short-circuited, and the vehicle safety is protected.

[0018] Further, the judgment basis of the open-circuit load type and the short-circuit load type is:

[0019] If V ad1 -V ad2 <V diff , V ad2 >V min and V ad3 <V min , V ad4 -V ad3 <V diff , the load is judged to be open-circuited.

[0020] If V ad1 -V ad2 >V diff , V ad2 <V min and V ad3 <V min , the load is judged to be short-circuited.

[0021] Wherein, V min is a low-voltage threshold value of the high-side switch output end, V diff is a voltage difference threshold value between the high-side switch, V ad1 is the average value of the power supply end voltage signal in the on driving switch time period, V ad2 is the average value of the load end voltage signal in the on driving switch time period, V ad3 is the average value of the load end voltage signal in the block driving switch time period, and V ad4 is the average value of the power supply end voltage signal in the block driving switch time period.

[0022] Further, the load type further includes a resistive load type; when the load type is a resistive load, the control unit executes the instruction of turning on the high-side switch; and the judgment basis of the resistive load type is:

[0023] If V ad1 -Vad2 V diff V ad2 V min V ad3 V min V min V diff V ad1 V ad2 V ad3 V ad3 .

[0024] When the external load is a resistive load, there is no inrush current when the high-side switch is turned on, so the high-side switch can be directly turned on, i.e., the high-side switch turning-on instruction can be executed.

[0025] Further, the drive switch includes two triodes, i.e., a first switch tube and a second switch tube, the emitter and the collector of the first switch tube are respectively connected to the power supply end and the load end, and the base of the first switch tube is connected to the collector of the second switch tube; the emitter of the second switch tube is connected to the ground, and the base of the second switch tube is connected to the control unit.

[0026] By connecting the control unit to the control end of the second switch tube (i.e., the base of the second switch tube), the conduction and disconnection of the second switch tube can be controlled, and the control end of the second switch tube is connected to the control end of the first switch tube, so as to control the on-off of the first switch tube through the switching state of the second switch tube, and the conduction and disconnection of the first switch tube can be controlled through the control unit, thereby realizing the self-diagnosis process of the high-side switch circuit, and compared with directly controlling one switch tube to realize the on-off state of the self-diagnosis circuit, using two switch tubes and controlling the state of one switch tube through the state of the other switch tube improves the reliability of the control. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a high-side switch circuit structure with a self-diagnosis function according to the present application;

[0028] Figure 2 is a control method flow chart of the high-side switch circuit with a self-diagnosis function according to the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and examples.

[0030] High-side switch circuit with self-diagnosis function

[0031] The high-side switch circuit with self-diagnosis function of the embodiment comprises a high-side switch, a self-diagnosis circuit and a control unit, the high-side switch is a high-side switch circuit with an overcurrent protection circuit, the high-side switch is connected in series between a power supply and a load, and is used for conducting or blocking the power supply of the load, the self-diagnosis circuit comprises a signal acquisition circuit and a driving circuit, the driving circuit comprises a driving switch and a current-limiting resistor connected in series between the power supply and the load, the driving switch is connected to the control unit, so as to send a diagnosis start signal to the driving switch when the control unit receives a start signal of the high-side switch circuit, to control the on-off of the driving switch, to realize the conducting or blocking of the power supply of the load in the circuit where the driving switch is located, the acquisition circuit comprises a power supply end acquisition circuit and a load end acquisition circuit, the power supply end acquisition circuit is connected to a power supply end voltage detection port and the control unit, to acquire the power supply end signal after the diagnosis start, and the load end acquisition circuit is connected to a load end voltage detection port and the control unit, to acquire the load end signal after the diagnosis start; the control unit is used for receiving the power supply end voltage signal and the load end voltage signal, judging the load type, and performing the pre-charge processing of the corresponding load when the load type is a capacitive load type or an inductive load type (the inductive load type and the capacitive load type are not simply inductors and capacitors, but the equivalent circuits presented by the back-end load circuit), to reduce the current impact when the high-side switch circuit is started.

[0032] By setting the high-side switch circuit comprising a high-side switch, a self-diagnosis circuit and a control unit, the load can be preliminarily diagnosed before the high-side switch circuit is started, and the pre-processing of the corresponding load is needed when the diagnosis result is an inductive load or a capacitive load, to avoid the current impact when the high-side switch circuit is started, and the phenomenon of excessive current of the high-side switch circuit at the starting moment caused by the load is avoided by setting the circuit, and the problem of false protection is avoided.

[0033] As Figure 1As shown, the high-side switch circuit includes a third switch tube Q3, a fourth switch tube Q4, a resistor R6, a resistor R7, a resistor R8, and a resistor R9, and the specific connection relationship is that the third switch tube Q3 is connected in series between the power supply end and the load end, the resistor R6 is connected between the drain and the gate (i.e. the control end) of the third switch tube Q3, the gate of the third switch tube Q3 is further connected to the drain of the fourth switch tube Q4 through the resistor R11, so as to control the on-off of the third switch tube Q3 through the fourth switch tube Q4, the gate (i.e. the control end) of the fourth switch tube Q4 is connected to the ground through the resistor R9 and is connected to the control unit through the resistor R8, so as to transmit the control signal of the control unit to the control end of the fourth switch tube Q4, and then the fourth switch tube Q4 can make the switching state corresponding to the control signal transmitted by the control unit, and the switching state of the fourth switch tube Q4 is reflected to the control end of the third switch tube Q3, so as to realize the on-off control of the third switch tube Q3, and then realize the on-off control of the power input end and the power output end.

[0034] The self-diagnosis circuit includes a first switch tube Q1 (PNP type triode), a second switch tube Q2 (NPN type triode), a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, and a resistor R10, and the specific connection relationship is that the first switch tube Q1 is connected in series between the power supply end and the load end (not in the same branch as the third switch tube), and the current-limiting resistor R4 is further connected in series between the first switch tube Q1 and the load end, the resistor R1 is connected between the emitter and the base of the first switch tube Q1 (the base of the first switch tube Q1 is the control end of the first switch tube Q1), the control end of the first switch tube Q1 is further connected to the collector of the second switch tube Q2 through the resistor R2, so as to realize the on-off control of the first switch tube Q1 through the switching state of the second switch tube Q2, the emitter of the second switch tube Q2 is connected to the ground, the base (i.e. the control end) of the second switch tube Q2 is connected to the control unit through the resistor R3, so as to transmit the control signal of the control unit to the control end of the second switch tube Q2, and then the second switch tube Q2 can make the switching state corresponding to the control signal transmitted by the control unit, and the switching state of the second switch tube Q2 is reflected to the control end of the first switch tube Q1, so as to realize the on-off control of the first switch tube Q1; the resistor R5 is connected between the power supply end and the control unit, and the resistor R6 is connected between the load end and the control end, so as to transmit the signals of the power supply end and the load end to the control unit.

[0035] The control unit is used to realize the control of the high-side switch circuit, the control of the self-diagnosis circuit, and the reception and processing of signals, i.e. when the high-side switch circuit is turned on, the self-diagnosis circuit is controlled accordingly, the data of the power supply end and the load end in the diagnosis process is received during the self-diagnosis process, the received data is analyzed to obtain the load type of the load end, and the corresponding control process of turning on the high-side switch is performed, such as Figure 2As shown, the specific control method for a high-side switching circuit with self-diagnostic function is as follows:

[0036] 1) When a command to open the high-side switch circuit is received, the self-diagnostic control circuit begins to perform self-diagnosis.

[0037] In this embodiment, the self-diagnostic circuit controls the second switch Q2 to turn on and off by outputting a high or low level from the control unit. When the second switch Q2 is on, the electrical node of resistor R2 near the second switch Q2 is pulled low, thereby creating a voltage difference across resistor R1. This voltage difference can turn on the first switch Q1. When the second switch Q2 is off, the voltage at the electrical node of resistor R2 near the second switch Q2 is reduced by the power supply terminal (i.e., Figure 1 The voltage difference across resistor R1 disappears, and the first switch Q1 is turned off.

[0038] In this embodiment, the self-diagnostic process is controlled as follows: First, the first switch Q1 of the self-diagnostic circuit is turned on for a duration T1 (e.g., 50ms). During this time, the power supply will provide a small current to the downstream load through the first switch Q1 and resistor R4. Then, the first switch Q1 is turned off for a duration T2 (e.g., 50ms, i.e., T1 = T2 in this embodiment), thus completing the control of the self-diagnostic process. The total diagnostic time T of this self-diagnostic process is... diag =T1+T2.

[0039] 2) During the self-diagnosis process, data is collected from the power supply end and the load end.

[0040] During the diagnostic process, the voltage data of the power supply terminal is collected at a set sampling rate through the acquisition circuit containing resistor R5, and the voltage data of the load terminal is collected at a set sampling rate through the acquisition circuit containing resistor R10. In this embodiment, the voltage of the power supply terminal and the load terminal is sampled at a rate of 1ms / time, and the corresponding voltage data is recorded.

[0041] 3) Determine the load type based on the data from the power supply and load sides.

[0042] The average value V of the power supply terminal voltage during cycle T1 is calculated using voltage sampling data acquired during the self-diagnosis process. ad1 The average value V of the load terminal voltage during period T1 ad2 The average value V of the load terminal voltage during period T2 ad3 And the average value V of the power supply terminal voltage during cycle T2. ad4 And based on the pre-obtained low voltage threshold value (V) at the high-side switch output. min Based on experimental data, this embodiment uses V min =4.8V) and the voltage difference threshold across the high-side switch (Vdiff Based on the test data obtained, in this embodiment, V diff = 2.5V) is compared with the calculated V ad1 , V ad2 , V ad3 and V ad4 , and after comparison, the load type of the load end is determined, the load type of the load end in this embodiment includes inductive load, capacitive load and resistive load, and through the above comparison, it can also be obtained whether the load end is faulty, if faulty, the specific fault type can also be obtained, the fault type of the load end in this embodiment includes short circuit and open circuit, the specific data comparison and the judgment method of the load type and the fault type of the load end are as follows:

[0043] ①If V ad1 -V ad2 <V diff , V ad2 >V min and V ad3 <V min , V ad4 -V ad3 <V diff , it is judged that the external load is open circuit.

[0044] Because when the load is open circuit, after the first switch tube Q1 is opened, the voltage of the load end is soon the same as the voltage of the power supply end, and after the first switch tube Q1 is closed, the voltage of the load end is immediately 0, therefore, in the T1 period, V ad1 -V ad2 <V diff and V ad2 >V min , in the T2 period, V ad3 <V min and V ad4 -V ad3 <V diff , the external load is in a fault state, and the fault type is open circuit.

[0045] ②If V ad1 -V ad2 >V diff , V ad2 <V min and V ad3 <V min , it is judged that the external load is short circuit.

[0046] Because when the load is short circuit, after the first switch tube Q1 is opened, because the external load is short circuit to the ground, the voltage of the load end will be continuously pulled down by the grounding point and be at a low potential, and after the first switch tube Q1 is closed, the voltage of the load end is still at a low potential, therefore, in the T1 period, V ad1 -V ad2 >Vdiff and V ad2 <V min , V ad3 <V min , V

[0047] ③If V ad1 -V ad2 >V diff , V ad2 >V min and V ad3 >V min , then the external load is judged as capacitive load.

[0048] Because when the external load is capacitive load, after the first switch tube Q1 is opened, the capacitive load is in charging state, that is, after the first switch tube Q1 is opened, the voltage at the load end rises from 0, but because the charging current is limited by the resistor R4, the average value of the voltage at the load end will continue to be less than the average value of the voltage at the power supply end, and after the first switch tube Q1 is closed, the capacitive load is in discharging state, so after the first switch tube Q1 is closed, the voltage value can still be detected at the load end, so in the T1 period, V ad1 -V ad2 >V diff and V ad2 >V min , in the T2 period, V ad3 >V min , the external load is capacitive load.

[0049] ④If V ad1 -V ad2 <V diff , V ad2 >V min and V ad3 <V min , V ad4 -V ad3 >V diff , then the external load is judged as inductive load.

[0050] Because when the external load is inductive load, after the first switch tube Q1 is opened, the inductive load can establish a magnetic field, so there are V ad1 -V ad2 <V diff and V ad2 >V min , and after the first switch tube Q1 is closed, based on the energy storage of the inductive load itself, an induced voltage will be generated across the inductor, which is opposite in direction to the external voltage, and because the load and the control unit are grounded, V ad3 will collect negative voltage in this time, so V ad4 >Vad3 Therefore, if V ad1 -V ad2 <V diff , V ad2 >V min and V ad3 <V min , V ad4 -V ad3 >V diff , the external load is a capacitive load.

[0051] ⑤If V ad1 -V ad2 >V diff , V ad2 >V min and V ad3 <V min , the external load is judged as a resistive load.

[0052] Because when the external load is a resistive load, after opening the first switch tube Q1, the resistive load and the resistor R4 form a voltage divider, resulting in V ad1 -V ad2 >V diff , V ad2 >V min , and after closing the first switch tube Q1, the voltage at the load end is immediately 0, so that in the T1 period, V ad1 -V ad2 >V diff and V ad2 >V min , in the T2 period, V ad3 <V min , the external load is a resistive load.

[0053] 4) According to the load type, the corresponding start control of the high-side switching circuit is carried out.

[0054] ①When the external load is open, the control unit refuses the command of the external opening of the high-side switching circuit, and feeds back the fault information to the command issuing unit. When the external load is open, that is, the external load has a fault, so the instruction of opening the high-side switching circuit is not executed, and the external load fault information is sent to the command issuing unit, thereby avoiding opening the high-side switching circuit when the external load is faulty, causing damage to the high-side switching circuit or the load, and thereby ensuring the reliable process of controlling the high-side switching circuit.

[0055] ②When the external load is short-circuited, the control unit refuses the command of the external to open the high-side switch circuit, and feeds back the fault information to the command issuing unit. When the external load is short-circuited, that is, the external load is faulty, therefore, the instruction of opening the high-side switch circuit is not executed, and the external load fault information is sent to the command issuing unit, thereby avoiding opening the high-side switch circuit when the external load is faulty, causing damage to the high-side switch circuit or the load, and thereby ensuring the reliable control process of the high-side switch circuit, that is, avoiding the irreversible damage to the MOSFET caused by the short-circuit impact current after opening the high-side switch circuit in the prior art, which seriously affects the service life of the high-side switch, and when the short-circuit capacity is large enough, the high-side switch may be directly damaged, resulting in serious failure of the vehicle function, and thereby the control unit refuses the command of the external to open the high-side switch circuit when the external load is short-circuited, thereby protecting the safety of the vehicle.

[0056] ③When the external load is a capacitive load, the control unit performs pre-charge processing on the load, that is, the first switch tube Q1 is opened for a T3 time period (for example, 100 ms, the setting of this time is to reduce the capacity of the capacitive load, to avoid the impact current of the capacitive load after opening the high-side switch circuit, causing the high-side switch circuit to fail to open), then the high-side switch circuit is opened, and the first switch tube Q1 is closed again after 5 ms. By pre-charging the capacitive load when the external load is a capacitive load, the capacity of the capacitive load is reduced, so that the capacity of the capacitive load is not enough to generate an impact current, and then the high-side switch circuit is opened, thereby avoiding the problem of false protection of the high-side switch circuit due to the impact current of the capacitive load at the moment of opening the high-side switch circuit, and based on the setting time (for example, the setting time in this embodiment is 5 ms) after opening the high-side switch circuit, the pre-charge is closed again, thereby avoiding the situation that there is still an impact current when the pre-charge is directly turned off and the high-side switch circuit is opened again.

[0057] ④When the external load is an inductive load, the control unit performs pre-charge processing on the load, that is, the first switch tube Q1 is opened for T4 (for example, 50 ms, the setting of this time is to reduce the capacity of the inductive load, to avoid the impact current of the inductive load after opening the high-side switch circuit, causing the high-side switch circuit to fail to open), then the high-side switch circuit is opened, and the first switch tube Q1 is closed again after 5 ms. As the inductive load and the capacitive load will have an impact current at the moment of opening the high-side switch circuit, pre-charge processing is required when the external load is an inductive load, to reduce the capacity of the inductive load, to avoid the impact of the impact current at the moment of opening the high-side switch. And based on the setting time (for example, the setting time in this embodiment is 5 ms) after opening the high-side switch circuit, the pre-charge is closed again, thereby avoiding the situation that there is still an impact current when the pre-charge is directly turned off and the high-side switch circuit is opened again.

[0058] ⑤When the external load is a resistive load, the control unit directly opens the high-side switch circuit. When the external load is a resistive load, there is no inrush current after the high-side switch circuit is opened, so the high-side switch circuit can be directly opened.

[0059] Through the control method of the embodiment, the type of the external load or the type of the external fault can be accurately judged, and when the external load has a fault, the command to open the high-side switch circuit is refused to be executed, and the external load fault signal is transmitted to the command issuing end, thereby avoiding irreversible damage to the high-side switch circuit after the high-side switch is opened when the external load has a fault. When the external load is an inductive load or a capacitive load, the external load is pre-charged to reduce the capacity of the external load, and then when the high-side switch circuit is opened, there is no impact of inrush current, which helps the smooth opening of the high-side switch. That is, through the setting of the high-side switch circuit with a self-diagnosis function and the control method of the embodiment, the process of safely and smoothly opening the high-side switch circuit is realized.

[0060] The above is only a preferred embodiment of the present application and is not used to limit the present application. The patent protection scope of the present application is subject to the claims, and any equivalent structural changes made by applying the content of the specification and drawings shall be included in the protection scope of the present application.

Claims

1. A high-side switching circuit with self-diagnosis function, comprising a high-side switch provided between a power supply and a load, and a control unit which controls the high-side switch to control on-off of the high-side switch, characterized in that, The self-diagnosis circuit comprises a signal acquisition circuit and a driving circuit, and the driving circuit comprises a driving switch connected in series between a power supply and a load and connected in parallel with the high-side switch, wherein the driving switch comprises a first switch tube connected in series between a power supply end and a load end, a current-limiting resistor connected in series between the first switch tube and the load end, a control end of the first switch tube connected to a collector of a second switch tube, an emitter of the second switch tube grounded, and a control end of the second switch tube connected to the control unit; and the acquisition circuit comprises a power supply end voltage detection port connected to the control unit through a power supply end acquisition circuit and a load end voltage detection port connected to the control unit through a load end acquisition circuit. The control unit is configured to, when receiving the high-side switch opening instruction, send a diagnosis opening instruction to the driving switch, perform diagnosis control on the driving switch, realize conduction or block of power supply of a circuit in which the driving switch is located to the load, and acquire a power supply end voltage signal and a load end voltage signal after diagnosis opening, and determine the load type according to the power supply end voltage signal and the load end voltage signal, and perform pre-charging processing when the load type is an inductive load type or a capacitive load type, so as to reduce current impact when the high-side switch circuit is opened.

2. The high-side switch circuit with self-diagnosis function according to claim 1, characterized in that, When the load type is the inductive load type or the capacitive load type, the pre-charging processing is that the control unit controls the driving circuit of the self-diagnosis circuit to be conducted for a set time.

3. The high-side switch circuit with self-diagnosis function according to claim 1, characterized in that, The diagnostic control involves: controlling the drive switch to turn on for a set first time, and then controlling the drive switch to turn off for a set second time; the power supply voltage signal includes: the average value V of the power supply voltage signal within the first time period. ad1 And the average value V of the power supply terminal voltage signal during the second time period. ad4 The load-side voltage signal includes the average value V of the load-side voltage signal within the first time period. ad2 and the average value V of the load-side voltage signal during the second time period. ad3 .

4. The high-side switch circuit with self-diagnosis function according to claim 3, characterized in that, The load type is determined according to the power supply end voltage signal and the load end voltage signal. If , and then the load is judged as capacitive. If , and , then the load is judged as a sensitive load. Wherein, V min is a low voltage threshold value of the high-side switch output end, V diff is a voltage difference threshold value across the high-side switch.

5. The high-side switch circuit with self-diagnosis function according to claim 1, characterized in that, The load type further comprises an open-circuit load type and a short-circuit load type; when the load type is the open-circuit load type or the short-circuit load type, the control unit refuses to execute the high-side switch opening instruction, and sends an alarm information to a unit that sends the high-side switch opening instruction.

6. The high-side switch circuit with self-diagnosis function according to claim 5, characterized in that The open-circuit load type and the short-circuit load type are determined according to the power supply end voltage signal and the load end voltage signal. If , and , then the load is open circuit. If , and then a short circuit of the load is determined. V min V is a low voltage threshold value of the high-side switch output end, V diff V is a voltage difference threshold value between the two ends of the high-side switch, V ad1 V is an average value of the power end voltage signal in the conduction driving switch time period, V ad2 V is an average value of the load end voltage signal in the conduction driving switch time period, V ad3 V is an average value of the load end voltage signal in the blocking driving switch time period, V ad4 V is an average value of the power end voltage signal in the blocking driving switch time period.

7. The high-side switch circuit with self-diagnosis function according to claim 1, characterized in that, The load type further comprises a resistive load type; when the load type is the resistive load type, the control unit executes the high-side switch opening instruction; and the resistive load type is determined according to the power supply end voltage signal and the load end voltage signal. If , and then the load is judged as resistive. V min V diff V ad1 V ad2 V ad3 V ad3 .

8. The high-side switch circuit with self-diagnosis function according to claim 1, characterized in that, The driving switch comprises two triodes, namely a first switch tube and a second switch tube, an emitter and a collector of the first switch tube are respectively connected to a power supply end and a load end, a base of the first switch tube is connected to a collector of the second switch tube, an emitter of the second switch tube is grounded, and a base of the second switch tube is connected to the control unit.

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