Low-side control circuit and control method

Abstract

The application discloses a low-side control circuit and a control method, and belongs to the technical field of vehicle-mounted electronics. The low-side control circuit is composed of a redundant current on-off path through a first switching unit and a second switching unit. When any switching unit fails and is short-circuited, the other switching unit with normal function can still independently perform a shutdown operation, thereby effectively avoiding the risk of mis-opening of the second load caused by single-point failure. The protection branch connected between the first switching unit and the ground terminal can inhibit voltage transients and surges in the circuit, further improving the reliability and safety of the system in a complex electrical environment and reducing the failure rate.

Description

Technical Field

[0001] This application relates to the field of automotive electronics technology, and in particular to low-side control circuits and control methods. Background Technology

[0002] In automotive electronic systems, low-side drive circuits are a common topology that achieves control through a closed-loop ground path for the load, widely used in body controllers to control loads such as relays, solenoid valves, and indicator lights. These circuit designs are typically based on transistors, field-effect transistors, or dedicated driver chips, offering advantages such as simple structure and low cost. However, in practical applications, it has been found that due to the inherent failure probability of semiconductor devices, when the switching devices in the low-side drive circuit fail (e.g., short-circuit breakdown), the controlled load may be erroneously activated under unexpected circumstances. This functional malfunction caused by a single point of failure poses a potential risk in scenarios involving safety or critical functions. Although selecting highly reliable devices can reduce the failure rate, it is impossible to completely eliminate such hidden dangers from the circuit architecture. Therefore, how to further improve reliability at the circuit design level and reduce the risk of load malfunction due to single-point failure has become a pressing technical problem in this field. Summary of the Invention

[0003] To address the safety hazard of potential load malfunctions due to single-point failures, a low-side control circuit and control method are provided to achieve highly reliable redundant shutdown and reduce the risk of erroneous function activation from the circuit architecture level.

[0004] This application provides a low-side control circuit, including:

[0005] The control unit includes a first control terminal and a second control terminal;

[0006] The first switching unit has its input terminal connected to the first control terminal, and its first output terminal is used to connect one end of the second load, while the other end of the second load is used to connect to the positive terminal of the power supply.

[0007] The second switching unit has a first terminal connected to the second control terminal, a second terminal connected to the second output terminal of the first switching unit, and a third terminal used for grounding.

[0008] A protection branch is provided, one end of which is connected to the first output terminal of the first switch unit, and the other end of which is used for grounding.

[0009] Optionally, the second switching unit employs a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

[0010] Optionally, the second switching unit uses an NMOS field-effect transistor. The gate of the NMOS field-effect transistor serves as the first terminal of the second switching unit and is connected to the second control terminal. The source of the NMOS field-effect transistor serves as the second terminal of the second switching unit and is connected to the second output terminal of the first switching unit. The drain of the NMOS field-effect transistor serves as the third terminal of the second switching unit and is used for grounding.

[0011] Optionally, the control unit is used to synchronously control the first control terminal and the second control terminal to output enable signals, so that the first switching unit and the second switching unit are turned on simultaneously, so as to turn on the second load;

[0012] The control unit is further configured to shut down at least one of the first switching unit and the second switching unit by controlling the output of a disable signal from the first control terminal and / or the second control terminal, thereby shutting down the second load.

[0013] Optionally, the protection branch includes:

[0014] A first transient voltage suppression element, one end of which serves as one end of the protection branch and is connected to the first output terminal of the first switching unit;

[0015] The second transient voltage suppression element has one end connected to the other end of the first transient voltage suppression element, and the other end of the second transient voltage suppression element is used as the other end of the protection branch for grounding.

[0016] Optionally, the first switching unit employs a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

[0017] Optionally, the first switching unit uses an NMOS field-effect transistor, with the gate of the NMOS field-effect transistor serving as the input terminal of the first switching unit and connected to the first control terminal, the drain of the NMOS field-effect transistor serving as the first output terminal of the first switching unit and connected to one end of the second load, and the source of the NMOS field-effect transistor serving as the second output terminal of the first switching unit and connected to the second terminal of the second switching unit.

[0018] Optional, also includes:

[0019] The third switching unit is connected in series between the first control terminal and the input terminal of the first switching unit.

[0020] Optionally, the third switching unit is one of a manual switch, a fuse, or an electronic switch.

[0021] This application provides a control method based on the above-described low-side control circuit, comprising:

[0022] The first control terminal outputs a first control signal to control the on / off state of the first switch unit;

[0023] The second control terminal outputs a second control signal to independently control the on / off state of the second switching unit;

[0024] The on / off state of the second load is determined by the logical AND relationship between the on / off states of the first switching unit and the second switching unit.

[0025] The beneficial effects of the above technical solution are as follows:

[0026] The low-side control circuit of this application forms a redundant current switching path through the first and second switching units. If either switching unit fails and short-circuits, the other functional switching unit can still independently perform a shutdown operation, effectively avoiding the risk of a second load being falsely turned on due to a single point of failure. The protection branch connected between the first switching unit and the grounding terminal can suppress voltage transients and surges in the circuit, further improving the reliability and safety of the system in complex electrical environments and reducing the failure rate. Attached Figure Description

[0027] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0028] Figure 1 The circuit diagram for the existing low-side control circuit;

[0029] Figure 2 This is a schematic diagram of a circuit fault.

[0030] Figure 3 This is a circuit diagram of one embodiment of the low-side control circuit described in this application. Detailed Implementation

[0031] The advantages of this application are further illustrated below with reference to the accompanying drawings and specific embodiments.

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0033] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0034] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0035] In the description of this application, it should be understood that the numerical labels before the steps do not indicate the order of the steps, but are only used to facilitate the description of this application and to distinguish each step, and therefore should not be construed as a limitation of this application.

[0036] This invention primarily addresses the problem of low-side control circuit malfunction in vehicle-mounted modules, proposing a highly reliable low-side control circuit. For example... Figure 1 The diagram shows a typical basic model of a low-side control circuit in the prior art, comprising: a microcontroller unit (MCU) chip U1, a low-side drive switch (LSD switch) chip U2, a switch S1, a protection branch consisting of two transient voltage suppressor transistors D1 and D2, and a first load R1. This circuit exhibits several potential failure modes in practical applications, which may lead to abnormal control functions. For example... Figure 2 As shown in Table 1, some typical failure modes and their impact analysis are referenced in Table 1:

[0037] Table 1

[0038] serial number Failure Mode Cause of the fault Circuit output status during fault ① Transient voltage suppressor diodes D1 / D2 were damaged by a short circuit. Electrostatic discharge (ESD) failure, with a short circuit as the failure model. After a short circuit, the circuit output state is low. ② Short circuit damage between the source and drain of low-side switch U2 Overcurrent stress (EOS) damage to the MOSFET leads to a short circuit between the drain and source; a short circuit between the drain and source pins causes solder bridging in the manufacturing process. After a short circuit, the circuit output state is low; ③ Short circuit damage between the gate and drain of low-side switch U2 Overcurrent stress (EOS) damage to the MOSFET causes a short circuit between the gate and drain; a short circuit between the gate and drain pins leads to solder bridging in the manufacturing process. When S1 is off, there is no effect; when S1 is on, the external terminal is high. ④ Switch S1 short circuit (open circuit) damage Switch failure, failure mode is short circuit or open circuit. When short-circuited, the circuit output is low; when open-circuited, the circuit function fails and cannot be controlled. ⑤ Short circuit damage between the MCU chip output pin and adjacent pins MCU output pin fault, short circuit between output pin and ground. When S1 is open, there is no effect; when S1 is on, the circuit function fails and cannot be controlled. ⑥ Short circuit damage between the MCU chip's input power supply and output pins MCU output pin fault, short circuit between the output pin and the MCU chip input power supply. When S1 is open, there is no effect; when S1 is closed, the circuit output state is low.

[0039] The above fault analysis reveals that existing single-channel low-side drive circuits pose a potential risk of load malfunction or control failure due to single-point failure. To improve reliability at the circuit architecture level, circuit design optimization is necessary. This invention introduces redundant switches and corresponding control logic to ensure that the circuit can still be safely shut down even when a single component experiences a specified fault, thereby significantly reducing the risk of malfunction.

[0040] Based on the above-mentioned fault issues, please refer to Figure 3 This application provides a low-side control circuit with high reliability and redundant shutdown, which reduces the risk of erroneous function activation from the circuit architecture level. The circuit includes: a control unit U3, a first switching unit U4, a second switching unit Q1, and a protection branch.

[0041] Control unit U3 includes a first control terminal and a second control terminal;

[0042] The first switching unit U4 has its input terminal connected to the first control terminal, and its first output terminal is used to connect one end of the second load R2, while the other end of the second load R2 is used to connect to the positive terminal of the power supply.

[0043] The second switch unit Q1 has a first end connected to the second control terminal, a second end connected to the second output terminal of the first switch unit U4, and a third end used for grounding.

[0044] A protection branch is provided, one end of which is connected to the first output terminal of the first switch unit U4, and the other end of which is used for grounding.

[0045] In this embodiment, the low-side control circuit forms a redundant current switching path through the first switching unit U4 and the second switching unit Q1. If either switching unit fails and short-circuits, the other functional switching unit can still independently perform a shutdown operation, effectively avoiding the risk of the second load R2 being erroneously turned on due to a single-point failure. The protection branch connected between the first switching unit U4 and the ground terminal can suppress voltage transients and surges in the circuit, further improving the reliability and safety of the system in complex electrical environments.

[0046] In a preferred embodiment, the second switching unit Q1 is a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

[0047] In this embodiment, when the current flowing through the second switching unit Q1 increases abnormally or the chip temperature exceeds the safety threshold, its built-in protection circuit will quickly activate and autonomously cut off the current path. This feature not only isolates the anomaly in the initial stage of the fault, preventing the fault from spreading to the front-end control unit U3 or the power network, but also effectively reduces the probability of triggering the redundant shutdown mechanism due to the overload damage of a single switching unit, thereby improving the availability and long-term operational stability of the entire low-side control circuit under complex operating conditions.

[0048] In a preferred embodiment, the second switching unit Q1 is an NMOS field-effect transistor. The gate of the NMOS field-effect transistor serves as the first terminal of the second switching unit Q1 and is connected to the second control terminal. The source of the NMOS field-effect transistor serves as the second terminal of the second switching unit Q1 and is connected to the second output terminal of the first switching unit U4. The drain of the NMOS field-effect transistor serves as the third terminal of the second switching unit Q1 and is used for grounding.

[0049] In this embodiment, the second switching unit Q1 uses an NMOS field-effect transistor, which fully utilizes its low on-resistance and fast switching speed, thus reducing system conduction losses and improving response speed. Simultaneously, this connection allows the second switching unit Q1 to reliably control the on / off state of the main circuit to ground. Its gate drive signal can be directly provided by the low-voltage control circuit, simplifying the drive design and ensuring good coordination with the first switching unit U4 in control logic, further enhancing the redundancy turn-off reliability of the dual-switch series structure.

[0050] In a preferred embodiment, the control unit U3 is used to synchronously control the first control terminal and the second control terminal to output enable signals, so that the first switching unit U4 and the second switching unit Q1 are turned on simultaneously, so as to turn on the second load R2;

[0051] The control unit U3 is also used to turn off at least one of the first switching unit U4 and the second switching unit Q1 by controlling the output of a disable signal from the first control terminal and / or the second control terminal, so as to turn off the second load R2.

[0052] In this embodiment, the control unit U3 is configured to synchronously control the enable signal outputs of the first control terminal and the second control terminal, thereby enabling the first switching unit U4 and the second switching unit Q1 to conduct simultaneously, thus reliably powering on the second load R2. When it is necessary to turn off the second load R2, the control unit U3 controls the first control terminal and / or the second control terminal to output a disable signal, ensuring that at least one of the two switching units is reliably turned off. This control strategy ensures the low impedance characteristics of the current path during normal operation, while forming a redundant turn-off condition based on a logical "AND" relationship during turn-off. This allows the normal turn-off action of any switching unit to independently cut off the second load R2 circuit, effectively preventing the second load R2 from being accidentally turned on even in a single-point failure scenario, significantly improving the functional safety level of the system.

[0053] In a preferred embodiment, the protection branch may include:

[0054] The first transient voltage suppression element D3 has one end serving as one end of the protection branch and connected to the first output terminal of the first switching unit U4.

[0055] The second transient voltage suppression element D4 has one end connected to the other end of the first transient voltage suppression element D3, and the other end of the second transient voltage suppression element D4 is used as the other end of the protection branch for grounding.

[0056] In this embodiment, the protection branch is composed of a first transient voltage suppression element D3 and a second transient voltage suppression element D4 connected in reverse series. This structure is connected between the output terminal of the first switching unit U4 and ground, and can bidirectionally clamp the voltage of this node. When the second load R2 is an inductive second load R2 or when positive or negative voltage transients and surges occur due to line interference, this protection branch can act quickly to limit the voltage within a safe range, thereby preventing overvoltage stress from damaging the first switching unit U4, the second switching unit Q1, and the control unit U3. This protection mechanism, combined with the built-in protection function of the switching unit, provides multi-level overvoltage protection for the entire low-side control circuit, enhancing its robustness and durability in complex electromagnetic environments such as automotive electrical environments.

[0057] In a preferred embodiment, the first switching unit U4 is a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

[0058] In this embodiment, the first switching unit U4 employs a field-effect transistor with integrated overcurrent and overheat protection. This device can quickly activate its internal protection mechanism and actively shut down when it experiences abnormally large currents or excessively high junction temperatures. This not only provides immediate localized current limiting and shutdown for fault currents in the event of serious faults such as short circuits to ground, effectively preventing the spread of fault effects to downstream control circuits, but also enables self-protection before the switching unit faces permanent damage due to abnormal overheating. Combined with the similar protection function of the second switching unit Q1, the two together construct a distributed fault management capability, improving the overall reliability of the system in coping with electrical and thermal stresses from the source and reducing the failure rate.

[0059] In a preferred embodiment, the first switching unit U4 is an NMOS field-effect transistor. The gate of the NMOS field-effect transistor serves as the input terminal of the first switching unit U4 and is connected to the first control terminal. The drain of the NMOS field-effect transistor serves as the first output terminal of the first switching unit U4 and is connected to one end of the second load R2. The source of the NMOS field-effect transistor serves as the second output terminal of the first switching unit U4 and is connected to the second terminal of the second switching unit Q1.

[0060] In this embodiment, the first switching unit U4 uses an NMOS field-effect transistor, with its gate, drain, and source connected to the first control terminal, the second load R2 terminal, and the second terminal of the second switching unit Q1, respectively. Placing the NMOS device between the power supply and the second switching unit Q1 allows its body diode to form a freewheeling path under specific operating conditions, while also allowing it to withstand the main voltage stress in the circuit. This layout maintains consistency with the NMOS device in the second switching unit Q1 in terms of electrical parameters and driving characteristics, which is beneficial for the synchronous matching of control signals and simplifies the design of the driving circuit. This series connection structure of identical devices not only ensures impedance matching and current balance between the two switches in the on state, but also enables the other identical switch to reliably turn off due to consistent electrical characteristics when a single switch fails and short-circuits, thereby ensuring the effective execution of the redundancy protection mechanism.

[0061] In a preferred embodiment, the low-side control circuit may further include:

[0062] The third switch unit S2 is connected in series between the first control terminal and the input terminal of the first switch unit U4.

[0063] In this embodiment, a third switch unit S2 is connected in series between the first control terminal and the input terminal of the first switch unit U4. This third switch unit S2 can be used as a maintenance switch, an emergency shutdown switch, or a function enable switch. Its connection allows operators or the host system to reliably cut off the control signal path of the first switch unit U4 by controlling this switch unit without disconnecting the main power supply, thereby forcibly shutting off the second load R2 circuit. This adds a physical isolation level to the system's shutdown mechanism, providing convenience and safety when circuit maintenance, testing, or manual isolation of the second load R2 is required in emergencies, further improving the system's maintainability and safety design.

[0064] This application effectively improves the fault tolerance of the vehicle-mounted low-side control circuit by introducing redundant switching units and adjusting the circuit topology. When any critical switching device in the circuit fails and short-circuits, another functional switching unit connected in series can still independently disconnect the circuit, thereby preventing the second load R2 from being mistakenly turned on. This redundancy design at the architectural level, combined with the selection of automotive-grade high-reliability components, not only significantly reduces the overall failure rate of the system, but also ensures that the circuit function can still be maintained in a safe state when a single point of failure occurs, greatly avoiding subsequent functional abnormalities caused by control circuit failure.

[0065] In a preferred embodiment, the third switching unit S2 is one of a manual switch, a fuse, or an electronic switch.

[0066] In this embodiment, when a manual switch is used, the system can be provided with an intuitive local hard-wired shutdown capability, facilitating on-site operation and emergency intervention. When a fuse is used, it can actively melt and disconnect the control path to prevent the fault from escalating when an overcurrent fault occurs in the control signal circuit, while also serving as a one-time failure indicator. When a controlled electronic switch (such as another MOSFET or relay) is used, remote or automatic control of the shutdown function can be achieved. This flexibility in configuration allows the circuit to adapt to the specific requirements of different application scenarios regarding safety, maintainability, and control methods, enhancing the practicality and applicability of the solution.

[0067] This application also provides a control method based on the above-described low-side control circuit, comprising the following steps:

[0068] The first control terminal outputs a first control signal to control the on / off state of the first switch unit U4;

[0069] The second control terminal outputs a second control signal to independently control the on / off state of the second switch unit Q1;

[0070] The on / off state of the second load R2 is determined by the logical AND relationship between the on / off states of the first switch unit U4 and the second switch unit Q1.

[0071] In this embodiment, independent control signals are output to the first and second control terminals to drive the first and second switching units U4 and Q1, respectively, which are connected in series. The final conduction state of the second load R2 is determined by a logical AND operation between the on / off states of the two switching units. When the second load R2 is normally on, the control unit U3 synchronously outputs an enable signal, enabling both switching units to conduct simultaneously. During the shutdown operation, only one control terminal needs to output a disable signal to shut down the corresponding switching unit, thus cutting off the entire circuit. This embodiment ensures that even if a single switching unit fails and short-circuits due to a fault, the other switching unit can still respond to the control signal and perform an effective shutdown. This achieves redundant shutdown functionality at the logic level and fundamentally avoids the risk of malfunction of the second load R2 due to a single point of failure, reducing the failure rate.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A low-side control circuit, characterized in that, include: The control unit includes a first control terminal and a second control terminal; The first switching unit has its input terminal connected to the first control terminal, and its first output terminal is used to connect one end of the second load, while the other end of the second load is used to connect to the positive terminal of the power supply. The second switching unit has a first terminal connected to the second control terminal, a second terminal connected to the second output terminal of the first switching unit, and a third terminal used for grounding. A protection branch is provided, one end of which is connected to the first output terminal of the first switch unit, and the other end of which is used for grounding.

2. The low-side control circuit according to claim 1, characterized in that, The second switching unit uses a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

3. The low-side control circuit according to claim 2, characterized in that, The second switching unit uses an NMOS field-effect transistor. The gate of the NMOS field-effect transistor serves as the first terminal of the second switching unit and is connected to the second control terminal. The source of the NMOS field-effect transistor serves as the second terminal of the second switching unit and is connected to the second output terminal of the first switching unit. The drain of the NMOS field-effect transistor serves as the third terminal of the second switching unit and is used for grounding.

4. The low-side control circuit according to claim 1, characterized in that, The control unit is used to synchronously control the first control terminal and the second control terminal to output enable signals, so that the first switching unit and the second switching unit are turned on at the same time, so as to turn on the second load; The control unit is further configured to shut down at least one of the first switching unit and the second switching unit by controlling the output of a disable signal from the first control terminal and / or the second control terminal, thereby shutting down the second load.

5. The low-side control circuit according to claim 1, characterized in that, The protection branch includes: A first transient voltage suppression element, one end of which serves as one end of the protection branch and is connected to the first output terminal of the first switching unit; The second transient voltage suppression element has one end connected to the other end of the first transient voltage suppression element, and the other end of the second transient voltage suppression element is used as the other end of the protection branch for grounding.

6. The low-side control circuit according to claim 1, characterized in that, The first switching unit uses a field-effect transistor, which integrates overcurrent protection and / or overheat protection functions.

7. The low-side control circuit according to claim 6, characterized in that, The first switching unit uses an NMOS field-effect transistor. The gate of the NMOS field-effect transistor serves as the input terminal of the first switching unit and is connected to the first control terminal. The drain of the NMOS field-effect transistor serves as the first output terminal of the first switching unit and is connected to one end of the second load. The source of the NMOS field-effect transistor serves as the second output terminal of the first switching unit and is connected to the second terminal of the second switching unit.

8. The low-side control circuit according to claim 1, characterized in that, Also includes: The third switching unit is connected in series between the first control terminal and the input terminal of the first switching unit.

9. The low-side control circuit according to claim 8, characterized in that, The third switching unit is one of a manual switch, a fuse, or an electronic switch.

10. A control method based on the low-side control circuit according to any one of claims 1 to 9, characterized in that, include: The first control terminal outputs a first control signal to control the on / off state of the first switch unit; The second control terminal outputs a second control signal to independently control the on / off state of the second switching unit; The on / off state of the second load is determined by the logical AND relationship between the on / off states of the first switching unit and the second switching unit.

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