A vehicle and control circuit and control method for limp-home mode thereof

Abstract

The application discloses a vehicle and a limp-home mode control circuit and control method thereof, wherein the control circuit comprises a first power-on precharge circuit and a fault mode control circuit; the first power-on precharge circuit comprises a filter capacitor and a first triode; the collector of the first triode is connected with a safety failure pin of a system basic chip; wherein through the synergistic effect of the charging state of the filter capacitor and the switching state of the first triode, when the system basic chip is powered on for the first time, a short-time low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit, and the fault mode control circuit is prevented from outputting a limp-home mode control signal; and when the system basic chip fails, according to a long-time low-level signal generated by the safety failure pin, the fault mode control circuit is triggered to output the limp-home mode control signal. The application not only improves the stability and safety of the system, but also provides users with more reliable and comfortable driving experience.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automotive electronics, in particular to a vehicle and a limp-home mode control circuit and control method thereof. BACKGROUND

[0002] Under the development trend of EEA3.0 electronic and electrical architecture, the peripheral loads of the vehicle are gradually integrated into the regional control unit. In this evolution process, from the dual perspectives of comprehensive cost and system safety, the industry gradually adopts a system basis chip (SBC) with multiple power output and integrated functional safety features to replace multiple discrete power chips without functional safety guarantee.

[0003] During the power-on process of the SBC chip, the safety failure pin will generate a low-level pulse signal of about 100ms. This signal is part of the chip's own power-on self-test mechanism, and after self-test, the pin will restore and maintain a long high-level state. When the SBC chip detects an internal failure during operation, the safety failure pin will change to a continuous low-level output. This low-level signal is the key control signal for triggering the vehicle to enter the Limphome mode. However, how to accurately distinguish between the short low-level pulse of the SBC chip during the first power-on and the long low-level signal in the fault state at the circuit design level becomes a key to ensure the stable operation of the vehicle control system and avoid false triggering of the Limphome mode.

[0004] Currently, there are mainly two kinds of conventional schemes for the trigger mechanism design of entering the Limphome mode:

[0005] Scheme one, a monitoring circuit is constructed by using a gate circuit or a special communication chip, aiming to monitor the reset state of the microcontroller unit (MCU) in real time. When the MCU resets, the monitoring circuit changes the output logic state, which is used as the trigger condition for entering the Limphome mode.

[0006] Scheme two, the safety failure pin monitoring function of the SBC chip is used. When the pin detects that the SBC chip has an abnormal condition causing the level to flip, the vehicle directly enters the Limphome mode.

[0007] However, both of the above schemes have obvious defects:

[0008] Firstly, in the circuit design architecture, both of them only consider the situation of one of MCU or SBC chip abnormal, ignoring the possibility of MCU and SBC chip abnormal at the same time in the complex automotive electronic system running environment, which greatly reduces the reliability and stability of the system in the face of complex fault scenarios.

[0009] Secondly, from the signal recognition accuracy level, both schemes do not effectively distinguish the short-time low-level pulse of the SBC chip safety failure pin at the first power-on and the long-time low-level signal in the fault state. This inaccurate signal recognition mechanism is easy to cause the vehicle to enter the Limphome mode due to misjudgment in the actual vehicle running process, seriously affecting the normal use experience of the user and reducing the overall usability and comfort of the vehicle. SUMMARY

[0010] The technical problem to be solved by the embodiments of the present application is to provide a vehicle limp-home mode control circuit to improve the safety and stability of the automotive electronic system under the EEA3.0 architecture and optimize the user experience.

[0011] To solve the above technical problems, the present application provides a vehicle limp-home mode control circuit, comprising:

[0012] a first power-on pre-charging circuit and a fault mode control circuit;

[0013] The first power-on pre-charging circuit comprises a filter capacitor and a first triode; the collector of the first triode is connected with the safety failure pin of the system base chip;

[0014] Wherein, through the synergistic effect of the charging state of the filter capacitor and the switching state of the first triode, the short-time low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit when the system base chip is powered on for the first time, preventing the fault mode control circuit from outputting the limp-home mode control signal; and according to the long-time low-level signal generated by the safety failure pin when the system base chip fails, triggering the fault mode control circuit to output the limp-home mode control signal.

[0015] Preferably, the base of the first triode is connected with the positive electrode of the filter capacitor and the safety failure pin of the system base chip, the emitter is connected with the positive electrode of the storage battery, and the negative electrode of the filter capacitor is grounded.

[0016] Preferably, the fault mode control circuit comprises a second triode, the base of the second triode is connected with the collector of the first triode, the emitter of the second triode is connected with the positive electrode of the storage battery, and the collector is connected with the limp-home mode control signal.

[0017] Preferably, when the system base chip is powered on for the first time, the end voltage of the filter capacitor is 0, the first transistor is turned on, the base and the emitter of the second transistor are at the same potential, the second transistor is turned off, and the short low-level signal is shielded by the second transistor, thereby preventing the output of the limp-home mode control signal.

[0018] Preferably, when the system base chip fails, the filter capacitor is fully charged, the first transistor is turned off, the long low-level signal makes the base voltage of the second transistor lower than the emitter voltage, the second transistor is turned on, and the output of the limp-home mode control signal is triggered.

[0019] Preferably, the fault mode control circuit further comprises a third transistor, the base of the third transistor is connected to the control signal of the microcontroller, the collector is connected to the base of the second transistor, and the emitter is grounded.

[0020] When the microcontroller fails, the control signal of the microcontroller changes from low to high, the base voltage of the third transistor is higher than the emitter voltage, the third transistor is turned on, the base voltage of the second transistor is lowered, the second transistor is turned on, and the output of the limp-home mode control signal is triggered.

[0021] Preferably, the first power-on precharge circuit further comprises a switching diode, the anode of the switching diode is connected to the positive electrode of the filter capacitor, and the cathode is connected to the emitter of the first transistor, which is used to discharge the charge of the filter capacitor when the regional control unit is powered off, and ensure that the end voltage of the filter capacitor is 0 when powered on next time.

[0022] The present application also provides a vehicle limp-home mode control method, which is based on the vehicle limp-home mode control circuit and comprises the following steps:

[0023] When the system base chip is powered on for the first time, the short low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit through the cooperation of the charging state of the filter capacitor and the switching state of the first transistor, thereby preventing the fault mode control circuit from outputting the limp-home mode control signal.

[0024] When the system base chip fails, the long low-level signal generated by the safety failure pin is used to trigger the fault mode control circuit to output the limp-home mode control signal through the cooperation of the charging state of the filter capacitor and the switching state of the first transistor.

[0025] Preferably, the fault mode control circuit comprises a second transistor and a third transistor, the base of the second transistor is connected with the collector of the first transistor, the emitter of the second transistor is connected with the positive pole of the battery, and the collector is connected with the limp-home mode control signal; the base of the third transistor is connected with the control signal of the microcontroller, the collector is connected with the base of the second transistor, and the emitter is grounded.

[0026] The control method further comprises: when the microcontroller fails, the base voltage of the third transistor is higher than the emitter voltage by the control signal of the microcontroller changing from low level to high level, the third transistor is turned on, and the base voltage of the second transistor is lowered, the second transistor is turned on, and the output of the limp-home mode control signal is triggered.

[0027] The application further provides a vehicle comprising the vehicle limp-home mode control circuit.

[0028] The application has the following beneficial effects: the application effectively distinguishes the short-time low-level signal during the first power-on self-checking of the SBC chip and the long-time low-level signal in the fault state by adding the power-on pre-charging circuit, avoids the short-time false action of the wiper, low beam and other loads during the first power-on, and significantly improves the user experience. At the same time, the SBC and MCU fault signal processing circuit is optimally designed, the fault signals of the two are logically processed, the limitation of only considering single chip failure in the prior art is solved, and it is ensured that the system can reliably enter the Limphome mode when any of the SBC or MCU fails, thereby improving the reliability of system operation and the safety of user driving. In addition, the application ensures that the brake light, low beam, wiper and other key safety function loads can reliably enter the Limphome mode after the control circuit fails, further enhancing the safety of the user during driving. The application not only improves the stability and safety of the system, but also reduces the development cost, and provides a more reliable and comfortable driving experience for the user. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 It is a structural schematic diagram of a vehicle limp-home mode control circuit according to an embodiment of the application. DETAILED DESCRIPTION

[0031] The following description of the embodiments is made with reference to the accompanying drawings, which are presented to illustrate specific embodiments in which the application can be practiced.

[0032] Referring to Figure 1 The vehicle limp-home mode control circuit provided by the embodiment of the application comprises:

[0033] The first power-on pre-charging circuit and the fault mode control circuit;

[0034] The first power-on pre-charging circuit comprises a filter capacitor and a first triode; the collector of the first triode is connected with a safety failure pin of a system basic chip;

[0035] The short-time low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit by the synergistic effect of the charging state of the filter capacitor and the switching state of the first triode when the system basic chip is powered on for the first time, so as to prevent the fault mode control circuit from outputting the limp-home mode control signal; and the long-time low-level signal generated by the safety failure pin is used to trigger the fault mode control circuit to output the limp-home mode control signal when the system basic chip fails.

[0036] Through the above setting, the first power-on pre-charging circuit is added, so that the problem that the existing circuit cannot distinguish the short-time low-level signal of the SBC chip powered on for the first time from the long-time low-level signal in the fault state is solved, and the user experience is improved.

[0037] Specifically, the first triode Q1 of the first power-on pre-charging circuit is a PNP triode, the base of the first triode Q1 is connected with the positive pole of the filter capacitor C1, and the negative pole of the filter capacitor C1 is grounded; the emitter of the first triode Q1 is connected with the positive pole of the battery (DC), and the collector is connected with the safety failure pin FS_SBC of the system basic chip.

[0038] The fault mode control circuit comprises a second triode Q2 and a third triode Q3, the second triode Q2 is a PNP triode, and the third triode Q3 is an NPN triode; the base of the second triode Q2 is connected with the collector of the first triode Q1, the emitter is connected with the positive pole of the battery (DC), and the collector is connected with the limp-home mode control signal FS_CTRL. The base of the third triode Q3 is connected with the control signal FS_MCU of the microcontroller MCU, the collector is connected with the base of the second triode Q2, and the emitter is grounded.

[0039] The first power-on pre-charging circuit added by the application can distinguish the short-time low-level signal of the SBC chip powered on for the first time from the long-time low-level signal in the fault state, which will be described below.

[0040] (I) short-time low-level signal of first power-on

[0041] The first transistor Q1 is used as a switch, and its on state depends on the terminal voltage of the filter capacitor C1. Therefore, at the first power-on, the terminal voltage of the filter capacitor C1 is 0, and the first transistor Q1 is in the open (on) state. After the first transistor Q1 is turned on, its collector voltage (i.e. the base voltage of the second transistor Q2) is the same as the emitter voltage (i.e. the battery voltage). And the emitter voltage of the second transistor Q2 is also the battery voltage, so the base and emitter of the second transistor Q2 have the same potential, and there is no potential difference between the base and emitter, and no current flows from the base to the second transistor Q2. Since there is no base current, the second transistor Q2 cannot form enough collector current to turn on, so the second transistor Q2 is in the off state.

[0042] The FS_SBC signal output by the safety failure pin FS_SBC of the SBC chip is used to indicate the working state of the SBC chip. At the first power-on, FS_SBC will be in a low state for a short time (about 100 ms), and then return to normal. As mentioned earlier, at the first power-on, although the FS_SBC signal is low, the first transistor Q1 is turned on, and the second transistor Q2 is turned off, so the FS_SBC signal is shielded outside the second transistor Q2. Therefore, the FS_SBC signal will not be transmitted to the FS_CTRL signal through the second transistor Q2, and will not cause the FS_CTRL to be pulled high, thereby avoiding the false action of the load related to the limp home mode of the function safety in the later stage.

[0043] It should be noted that in the embodiment of the present application, the first power-on pre-charging circuit further comprises a switching diode D1, the anode of the switching diode D1 is connected to the anode of the filter capacitor C1, and the cathode is connected to the emitter of the first transistor Q1. As mentioned earlier, the terminal voltage of the filter capacitor C1 must be 0 at the first power-on to turn on the first transistor Q1. However, after the regional control unit is powered off, there may still be charges in the filter capacitor C1, so it is necessary to quickly discharge the charges in the filter capacitor C1. The switching diode D1 provides a path for charge discharge, so that the charges in the filter capacitor C1 can be discharged when the regional control unit is powered off, ensuring that the terminal voltage of the filter capacitor C1 is 0 at the next power-on.

[0044] (II) Long low signal in fault state

[0045] When the SBC chip is working normally, the FS_SBC signal is high. If the SBC chip has a persistent fault, the FS_SBC signal will remain low for a long time. At this time, the filter capacitor C1 has been fully charged, causing the base voltage of the first transistor Q1 to rise, causing the first transistor Q1 to change from the open state to the closed state.

[0046] When the first transistor Q1 is off, the low level signal of FS_SBC can directly act on the base of the second transistor Q2, at this time, the base voltage of the second transistor Q2 will be lower than the emitter voltage, so that the second transistor Q2 is turned on. The positive voltage of the battery can be directly acted on the Limphome control signal FS_CTRL through the second transistor Q2. Therefore, the FS_CTRL signal is activated and directly controlled by the battery, so as to trigger the corresponding fail-safe mode or limp-home mode.

[0047] As a further improvement of the embodiment of the present application, the SBC chip and the safety failure pin group or logic of the MCU are combined, and the Limphome mode can be entered when the SBC or MCU fails, so as to improve the reliability of the Limphome circuit. Specifically:

[0048] When the SBC chip fails, as described above, the FS_SBC signal of the safety failure pin of the SBC will change from high level to continuous low level. The first transistor Q1 is off, and the second transistor Q2 is turned on, so that the FS_CTRL signal can be directly controlled by the battery.

[0049] When the MCU fails, the control signal FS_MCU of the MCU will change from low level to continuous high level. The base of the third transistor Q3 receives a high level signal, so that the base voltage of the third transistor Q3 is higher than the emitter voltage, and the third transistor Q3 is turned on. After the third transistor Q3 is turned on, the base of the second transistor Q2 is pulled to the ground (GND) and is lower than the emitter voltage, so that the second transistor Q2 is turned on. After the second transistor Q2 is turned on, the positive voltage of the battery can be directly acted on the Limphome control signal FS_CTRL through the second transistor Q2. Therefore, the FS_CTRL signal is activated and directly controlled by the battery, so as to trigger the corresponding fail-safe mode or home mode.

[0050] Through the above design, the control circuit of the present application can automatically switch to the Limphome mode directly controlled by the battery when the SBC or MCU fails, so as to ensure that the rear load can still work normally in the case of failure, and avoid system failure.

[0051] The following two examples are used to illustrate the role of the vehicle limp-home mode control circuit in the embodiment of the application. Assuming that a car is in normal driving, when the SBC chip in the regional control unit has a voltage abnormality fault, the safety fail pin FS_SBC changes from high level to a continuous low level signal. At this time, the second transistor Q2 of the control circuit in the embodiment of the application is turned on, the Limphome control signal FS_CTRL is directly controlled by the battery, thereby ensuring that the loads affecting the safety functions of the car such as the brake light, the low beam light, the wiper, and the like can continue to work normally, the vehicle can enter the limp-home mode, the basic driving safety state is maintained, and the key loads are prevented from stopping working due to the failure of the control circuit, thereby ensuring the safety of the user in the case of such a sudden fault, allowing the user to safely drive the vehicle to the maintenance site for repair, and avoiding the user from being in a dangerous situation due to the sudden loss of key safety functions of the vehicle. For another example, in a high-temperature environment for a long time, the MCU has a watchdog failure or other abnormal conditions, the MCU control signal FS_MCU changes from low level to a continuous high level signal, according to the circuit design of the application, the third transistor Q3 and the second transistor Q2 of the control circuit in the embodiment of the application are turned on in sequence, and the Limphome control signal FS_CTRL is also directly controlled by the battery, thereby ensuring the continuous operation of the loads related to the safety functions, maintaining the basic safety driving ability of the vehicle, and improving the safety of the user in a complex and possibly faulty driving environment.

[0052] In the embodiment of the application, the first transistor Q1, the second transistor Q2 and the third transistor Q3 are all SOT23 (Small Outline Transistor) packages, the switching diode D1 is an SOD-123 package, and the filter capacitor C1 is a 1205 (the length of the package size is 1.2 mm, and the width is 0.5 mm) package. Figure 1 Each resistor shown is a 0402 (the length of the package size is 0.04 inches, and the width is 0.02 inches) package.

[0053] Corresponding to the vehicle limp-home mode control circuit described in the first embodiment of the application, the second embodiment of the application further provides a vehicle limp-home mode control method, which is implemented based on the vehicle limp-home mode control circuit and includes the following steps.

[0054] When the system base chip is powered on for the first time, the short-time low level signal generated by the safety fail pin is shielded outside the fault mode control circuit through the cooperative action of the charging state of the filter capacitor and the switching state of the first transistor, and the limp-home mode control signal output by the fault mode control circuit is prevented.

[0055] When the system base chip fails, through the cooperation of the charging state of the filter capacitor and the switching state of the first triode, according to the long-time low-level signal generated by the safety failure pin, the limp-home mode control signal output by the fault mode control circuit is triggered.

[0056] Preferably, the fault mode control circuit comprises a second triode and a third triode, the base of the second triode is connected with the collector of the first triode, the emitter of the second triode is connected with the positive pole of the battery, and the collector is connected with the limp-home mode control signal; the base of the third triode is connected with the control signal of the microcontroller, the collector is connected with the base of the second triode, and the emitter is grounded.

[0057] The control method further comprises: when the microcontroller fails, through the control signal of the microcontroller changing from low level to high level, the base voltage of the third triode is higher than the emitter voltage, the third triode is turned on, and the base voltage of the second triode is lowered, the second triode is turned on, and the output of the limp-home mode control signal is triggered.

[0058] Corresponding to the vehicle limp-home mode control circuit described in the above embodiment one of the present application, the embodiment three of the present application further provides a vehicle comprising the vehicle limp-home mode control circuit described in the above embodiment one of the present application.

[0059] For the working principle and process of the above embodiment, refer to the description of the above embodiment one of the present application, which will not be repeated here.

[0060] As can be seen from the above description, compared with the prior art, the present application effectively distinguishes the short-time low-level signal during the first power-on self-test of the SBC chip and the long-time low-level signal in the fault state by adding the power-on pre-charging circuit, avoids the short-time misoperation of the wiper, low beam and other loads during the first power-on, and significantly improves the user experience. At the same time, the SBC and MCU fault signal processing circuit is optimally designed, the fault signals of the two are processed by OR logic, the limitation of only considering single chip failure in the prior art is solved, and it is ensured that the system can reliably enter the Limphome mode when any of the SBC or MCU fails, improving the reliability of system operation and user vehicle safety. In addition, by ensuring that the brake light, low beam, wiper and other key safety function loads can reliably enter the Limphome mode after the failure of the control circuit, the safety of the user during the use of the vehicle is further enhanced. The present application not only improves the stability and safety of the system, but also reduces the development cost, and provides the user with a more reliable and comfortable driving experience.

[0061] The above merely provides the preferred embodiment of the application, and cannot allude the protection scope of the application, therefore any equivalent changes made according to the claims of the application shall be within the scope of the application.

Claims

1. A limp-home mode control circuit for a vehicle, characterized by, The application relates to a limp-home mode control circuit for a vehicle, which comprises a first-time power-on pre-charging circuit and a fault mode control circuit. The first-time power-on pre-charging circuit comprises a filter capacitor and a first triode; the collector of the first triode is connected with a safety failure pin of a system base chip. The short-time low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit through the cooperation of the charging state of the filter capacitor and the switching state of the first triode when the system base chip is powered on for the first time, so that the output of the limp-home mode control signal of the fault mode control circuit is prevented; and when the system base chip is faulty, the long-time low-level signal generated by the safety failure pin is used to trigger the output of the limp-home mode control signal of the fault mode control circuit. The base of the first triode is connected with the positive pole of the filter capacitor, and the emitter is connected with the positive pole of a storage battery; the negative pole of the filter capacitor is grounded.

2. The control circuit of claim 1, wherein, The fault mode control circuit comprises a second triode, the base of the second triode is connected with the collector of the first triode, the emitter of the second triode is connected with the positive pole of the storage battery, and the collector is connected with the limp-home mode control signal.

3. The control circuit of claim 2, wherein, When the system base chip is powered on for the first time, the terminal voltage of the filter capacitor is 0, the first triode is turned on, the base and the emitter of the second triode have the same potential, the second triode is cut off, and the short-time low-level signal is shielded by the second triode, so that the output of the limp-home mode control signal is prevented.

4. The control circuit of claim 3, wherein, When the system base chip is faulty, the filter capacitor is fully charged, the first triode is cut off, the base voltage of the second triode is lower than the emitter voltage due to the long-time low-level signal, the second triode is turned on, and the output of the limp-home mode control signal is triggered.

5. The control circuit of claim 3, wherein, The fault mode control circuit further comprises a third triode, the base of the third triode is connected with a control signal of a microcontroller, the collector is connected with the base of the second triode, and the emitter is grounded.

6. The control circuit of claim 3, wherein, When the microcontroller is faulty, the control signal of the microcontroller changes from low level to high level, the base voltage of the third triode is higher than the emitter voltage, the third triode is turned on, the base voltage of the second triode is lowered, the second triode is turned on, and the output of the limp-home mode control signal is triggered. The first-time power-on pre-charging circuit further comprises a switching diode, the positive pole of the switching diode is connected with the positive pole of the filter capacitor, and the negative pole is connected with the emitter of the first triode, which is used for discharging the charge of the filter capacitor when the regional control unit is powered off, so that the terminal voltage of the filter capacitor is 0 when powered on next time.

7. The control circuit of claim 1, wherein, The control method is based on the vehicle limp-home mode control circuit as claimed in claim 1 and comprises the following steps:

8. A limp-home mode control method for a vehicle, characterized by, When the system base chip is powered on for the first time, the short-time low-level signal generated by the safety failure pin is shielded outside the fault mode control circuit through the cooperation of the charging state of the filter capacitor and the switching state of the first triode, so that the output of the limp-home mode control signal of the fault mode control circuit is prevented; and when the system base chip is faulty, the long-time low-level signal generated by the safety failure pin is used to trigger the output of the limp-home mode control signal of the fault mode control circuit. ​ When the system base chip fails, through the coordination of the charging state of the filter capacitor and the switching state of the first transistor, according to the long low level signal generated by the safety failure pin, the limp-home mode control signal is triggered to be output by the fault mode control circuit.

9. The control method according to claim 8, characterized by, The fault mode control circuit comprises a second transistor and a third transistor, the base of the second transistor is connected with the collector of the first transistor, the emitter of the second transistor is connected with the positive pole of the battery, and the collector is connected with the limp-home mode control signal; the base of the third transistor is connected with the control signal of the microcontroller, the collector is connected with the base of the second transistor, and the emitter is grounded; The control method further comprises: when the microcontroller fails, the base voltage of the third transistor is higher than the emitter voltage by the control signal of the microcontroller changing from low level to high level, the third transistor is turned on, the base voltage of the second transistor is reduced, the second transistor is turned on, and the output of the limp-home mode control signal is triggered.

10. A vehicle characterized by comprising: The vehicle limp-home mode control circuit comprises the vehicle limp-home mode control circuit according to any one of claims 1 to 7.

Images