A CAN bus activity detection and wake-up circuit, electronic device

Abstract

The utility model discloses a kind of CAN bus activity detection and wake-up circuit, electronic equipment belong to CAN bus communication technical field, comprising: CAN bus interface circuit, signal detection and processing circuit and controller, wherein: the input end of CAN bus interface circuit is connected CAN bus;Signal detection and processing circuit include voltage comparator, the same phase input end and the opposite phase input end of voltage comparator respectively receive CANH signal and CANL signal after CAN bus interface circuit electrical isolation, the output end of voltage comparator is connected to the wake-up pin of controller;Controller is used to monitor the level state of wake-up pin, when the level of this wake-up pin is effective state, control electronic equipment switches from hibernate mode to normal working mode.The utility model introduces electrical isolation and voltage difference detection mechanism, solve the false wake-up problem caused by common-mode interference or bus noise in prior art, realize reliable wake-up under low power consumption.

Description

Technical Field

[0001] This utility model belongs to the field of CAN bus communication technology, and more specifically, relates to a CAN bus activity detection and wake-up circuit and electronic equipment. Background Technology

[0002] In industrial control, automotive electronics, and various low-power embedded systems, the CAN (Controller Area Network) bus is widely used due to its high reliability and good anti-interference capabilities. To achieve energy saving and consumption reduction, many CAN bus-based devices or nodes need to have sleep and wake-up functions, that is, to enter a low-power sleep state when there is no communication demand, and to be woken up in time when communication activity occurs on the bus.

[0003] In existing technologies, there are several solutions for implementing CAN node sleep and wake-up. Some solutions rely on the system's main controller sending specific sleep commands, lacking the ability to autonomously detect bus activity status. Other solutions, while possessing some bus activity detection capabilities, often have relatively simple detection mechanisms. For example, some solutions determine activity status by directly monitoring the CAN bus signal level. This method is susceptible to common-mode interference or bus noise, leading to frequent false wake-ups, significantly increasing overall power consumption, and affecting system stability and reliability.

[0004] Furthermore, electrical isolation is essential in applications with high system security requirements. However, when combining isolation technology with a reliable bus activity detection mechanism, achieving accurate wake-up with low false alarms in high-noise environments while ensuring system isolation security remains a pressing issue.

[0005] Therefore, there is an urgent need in this field for a wake-up solution that can effectively combine electrical isolation technology and accurately and reliably detect CAN bus activity, so as to reduce false wake-up rate while ensuring system security and further improve system energy efficiency and reliability. Utility Model Content

[0006] To address the shortcomings of existing technologies, this invention provides a CAN bus activity detection and wake-up circuit and electronic device.

[0007] The present invention adopts the following technical solution.

[0008] The first aspect of this utility model provides a CAN bus activity detection and wake-up circuit, applied to electronic devices, the circuit comprising: The CAN bus interface circuit, signal detection and processing circuit, and controller include: The input terminal of the CAN bus interface circuit is connected to the CAN bus and is used to electrically isolate the CANH signal and the CANL signal. The signal detection and processing circuit includes a voltage comparator. The non-inverting input and inverting input of the voltage comparator receive the CANH signal and the CANL signal, which are electrically isolated by the CAN bus interface circuit, respectively, and are used to detect the voltage difference between the CANH signal and the CANL signal. The output of the voltage comparator is connected to the wake-up pin of the controller. The controller is used to monitor the level of the wake-up pin. When the level of the wake-up pin is active, it controls the electronic device to switch from sleep mode to normal operation mode.

[0009] Optionally, the CAN bus interface circuit includes a transceiver, a magnetic coupling device, and a first matching resistor network, wherein: The transceiver includes a CANH signal terminal and a CANL signal terminal; The first matching resistor network is connected to the CANH signal terminal and the CANL signal terminal, and is used to provide input signals to the magnetic coupling device.

[0010] Optionally, the first matching resistor network includes a first resistor, a second resistor, and a third resistor, wherein: The first resistor is connected in series between the CANH signal terminal and one end of one winding of the magnetic coupling device; The second resistor is connected in series between the CANL signal terminal and the other end of one winding of the magnetic coupling device; The third resistor is connected in parallel across the two ends of one winding of the magnetic coupling device.

[0011] Optionally, the signal detection and processing circuit includes a second matching resistor network, a clamping protection circuit, and a comparison and driving circuit, wherein: The second matching resistor network is connected to the output terminal of the CAN bus interface circuit and is used to perform impedance matching on the CANH and CANL signals output by the CAN bus interface circuit. The clamping protection circuit is connected between the two output terminals of the second matching resistor network and is used to provide overvoltage protection for the impedance-matched CANH and CANL signals. The comparison and drive circuit is connected to the two output terminals of the second matching resistor network to perform level comparison on the CANH signal and the CANL signal, and outputs the corresponding level to the wake-up pin of the controller based on the level comparison result.

[0012] Optionally, the second matching resistor network includes a fourth resistor, a fifth resistor, and a sixth resistor, wherein: The fourth resistor is connected in parallel across the two ends of the winding on the other side of the magnetic coupling device; The fifth resistor is connected in series between one end of the other winding of the magnetic coupling device and the non-inverting input of the voltage comparator. The sixth resistor is connected in series between the other end of the winding on the other side of the magnetic coupling device and the inverting input of the voltage comparator.

[0013] Optionally, the clamping protection circuit includes a clamping device connected between the non-inverting input and the inverting input of the voltage comparator.

[0014] Optionally, the comparison and drive circuit includes a voltage comparator, a seventh resistor, a tenth resistor, and a diode, wherein: The non-inverting input of the voltage comparator is grounded via the seventh resistor; The tenth resistor is connected in series between the output terminal of the voltage comparator and the inverting input terminal of the voltage comparator; The anode of the diode is connected to the output of the voltage comparator, and the cathode is connected to the wake-up pin of the controller.

[0015] Optionally, the voltage comparator is used to compare the voltage magnitudes of the CANH signal and the CANL signal. When there is a voltage difference between the CANH signal and the CANL signal, it outputs a high level; otherwise, it outputs a low level.

[0016] The second aspect of this utility model provides an electronic device, which includes a CAN bus activity detection and wake-up circuit as described in the first aspect of this utility model.

[0017] Compared with the prior art, the beneficial effects of this utility model include at least the following: 1. This utility model solves the problem of false wake-up caused by common-mode interference or bus noise in the prior art by introducing electrical isolation and voltage difference detection mechanism, and realizes reliable wake-up under low power consumption.

[0018] 2. This utility model achieves electrical isolation and impedance matching of CAN bus signals by using magnetic coupling devices and matching resistor networks, thus solving the problems of isolation safety and signal distortion.

[0019] 3. This utility model solves the impedance mismatch problem in signal transmission by configuring specific resistors in the first matching resistor network, thereby achieving better signal quality.

[0020] 4. This utility model solves the problems of bus signal overvoltage and noise interference by combining a second matching resistor network, a clamping protection circuit, and a comparison and drive circuit, and achieves more accurate voltage difference detection.

[0021] 5. This utility model solves the problem of signal fluctuation at the comparator input terminal by configuring the resistors in the second matching resistor network, and achieves stable voltage comparison.

[0022] 6. This utility model solves the problem of overvoltage potentially damaging the voltage comparator by using a clamping protection circuit, thus achieving circuit protection.

[0023] 7. This utility model solves the problem of unstable wake-up signal generation by comparing the voltage comparator and feedback resistor in the drive circuit, and realizes reliable wake-up signal output.

[0024] 8. This utility model directly compares the voltage difference between CANH and CANL using a voltage comparator, solving the delay and cost problems caused by complex detection circuits and achieving rapid response.

[0025] 9. By integrating the circuit into the electronic device, this utility model solves the problems of high power consumption and unreliable wake-up, achieving energy saving and stable operation. Attached Figure Description

[0026] Figure 1 The circuit detection schematic diagram provided according to the embodiment of this utility model includes: magnetic coupling device U1, transceiver U5, voltage comparator U3, clamping device U2, microcontroller U4, first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, seventh resistor R7, tenth resistor R10, diode D1, and first capacitor C1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. The described embodiments are merely some embodiments of this utility model, not all embodiments. Based on the spirit of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0028] This utility model provides a CAN bus activity detection and wake-up circuit in Embodiment 1, which is applied to electronic devices, such as... Figure 1 As shown, the circuit includes: The CAN bus interface circuit, signal detection and processing circuit, and controller include: The input terminal of the CAN bus interface circuit is connected to the CAN bus and is used to electrically isolate the CANH signal and the CANL signal. The signal detection and processing circuit includes a voltage comparator U3. The non-inverting input and inverting input of the voltage comparator U3 receive the CANH signal and the CANL signal after electrical isolation by the CAN bus interface circuit, respectively, and are used to detect the voltage difference between CANH and CANL. The output of the voltage comparator U3 is connected to the wake-up pin of the controller. The controller is used to monitor the level of the wake-up pin. When the level of the wake-up pin is active, it controls the electronic device to switch from sleep mode to normal operation mode.

[0029] It should be noted that this utility model solves the problem of false wake-up caused by common-mode interference or bus noise in the prior art by introducing electrical isolation and voltage difference detection mechanisms, and realizes reliable wake-up under low power consumption.

[0030] Preferably, the CAN bus interface circuit includes a transceiver U5, a magnetic coupling device U1, and a first matching resistor network, wherein: The transceiver U5 includes a CANH signal terminal and a CANL signal terminal; The first matching resistor network is connected to the CANH signal terminal and the CANL signal terminal, and is used to provide input signals to the magnetic coupling device U1.

[0031] It should be noted that this invention achieves electrical isolation and impedance matching of CAN bus signals by using magnetic coupling devices and matching resistor networks, thus solving the problems of isolation safety and signal distortion.

[0032] More preferably, the first matching resistor network includes a first resistor R1, a second resistor R2, and a third resistor R3, wherein: The first resistor R1 is connected in series between the CANH signal terminal and one end of one winding of the magnetic coupling device U1; The second resistor R2 is connected in series between the CANL signal terminal and the other end of one winding of the magnetic coupling device U1; The third resistor R3 is connected in parallel to both ends of one winding of the magnetic coupling device U1.

[0033] For example, the transceiver U5 can be the MAX14883 model; The resistance of the first resistor R1 is 1kΩ, the resistance of the second resistor R2 is 1kΩ, and the resistance of the third resistor R3 is 200Ω. The magnetic coupling device U1 can be selected from the Si866x series.

[0034] It should be noted that this invention solves the impedance mismatch problem in signal transmission by configuring specific resistors in the first matching resistor network, thereby achieving better signal quality.

[0035] Preferably, the signal detection and processing circuit includes a second matching resistor network, a clamping protection circuit, and a comparison and driving circuit, wherein: The second matching resistor network is connected to the output terminal of the CAN bus interface circuit and is used to perform impedance matching on the CANH and CANL signals output by the CAN bus interface circuit. The clamping protection circuit is connected between the two output terminals of the second matching resistor network and is used to provide overvoltage protection for the impedance-matched CANH and CANL signals. The comparison and drive circuit is connected to the two output terminals of the second matching resistor network to perform level comparison on the CANH signal and the CANL signal, and outputs the corresponding level to the wake-up pin of the controller based on the level comparison result.

[0036] It should be noted that this invention solves the problems of bus signal overvoltage and noise interference by combining a second matching resistor network, a clamping protection circuit, and a comparison and drive circuit, thus achieving more accurate voltage difference detection.

[0037] More preferably, the second matching resistor network includes a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6, wherein: The fourth resistor R4 is connected in parallel to both ends of the winding on the other side of the magnetic coupling device U1; The fifth resistor R5 is connected in series between one end of the other winding of the magnetic coupling device U1 and the non-inverting input of the voltage comparator U3; The sixth resistor R6 is connected in series between the other end of the winding on the other side of the magnetic coupling device U1 and the inverting input of the voltage comparator U3.

[0038] It should be noted that this invention solves the problem of signal fluctuation at the comparator input terminal by configuring the resistors in the second matching resistor network, thus achieving stable voltage comparison.

[0039] More preferably, the clamping protection circuit includes a clamping device U2, which is connected between the non-inverting input and the inverting input of the voltage comparator U3.

[0040] It should be noted that this utility model solves the problem of overvoltage potentially damaging the voltage comparator through a clamping protection circuit, thus achieving circuit protection.

[0041] More preferably, the comparison and drive circuit includes a voltage comparator U3, a seventh resistor R7, a tenth resistor R10, and a diode D1, wherein: The non-inverting input terminal of the voltage comparator U3 is grounded via the seventh resistor R7; The tenth resistor R10 is connected in series between the output terminal of the voltage comparator U3 and the inverting input terminal of the voltage comparator U3; The anode of diode D1 is connected to the output terminal of voltage comparator U3, and the cathode is connected to the wake-up pin of the controller.

[0042] It should be noted that this invention solves the problem of unstable wake-up signal generation by comparing the voltage comparator and feedback resistor in the drive circuit, and achieves reliable wake-up signal output.

[0043] More preferably, the positive power input terminal of the voltage comparator U3 is connected to the supply voltage VCC, and the negative power input terminal is grounded; The power supply voltage VCC is grounded via the first capacitor C1.

[0044] For example, the resistance of the fourth resistor R4 is 200Ω, the resistance of the fifth resistor R5 is 1kΩ, the resistance of the sixth resistor R6 is 1kΩ, the resistance of the seventh resistor R7 is 100kΩ, and the resistance of the tenth resistor R10 is 100kΩ. Clamping device U2 can be model BAV99; The voltage comparator U3 can be the OPZ503 model; The capacitance of the first capacitor C1 is 0.1μF; Diode D1 is model number 1N4148.

[0045] More preferably, the voltage comparator U3 does not require positive feedback or a reference voltage; it is used only to directly compare the voltages at the non-inverting and inverting input terminals. When the voltage at the non-inverting input terminal is higher or lower than the voltage at the inverting input terminal (i.e., there is a voltage difference between CANH and CANL), it outputs a high level; when the voltages at the non-inverting and inverting input terminals are equal (i.e., the CAN bus is idle), it outputs a low level.

[0046] It should be noted that this invention directly compares the voltage difference between CANH and CANL using a voltage comparator, thus solving the delay and cost problems caused by complex detection circuits and achieving a fast response.

[0047] Preferably, the controller is a microcontroller (MCU) (U4).

[0048] Preferably, the controller monitors the level of the wake-up pin (WK_UP). When the WK_UP pin is high (active), the controller controls the electronic device to switch from sleep mode to normal operation mode; when the WK_UP pin is low, the controller keeps the electronic device in sleep mode.

[0049] In Embodiment 2, this utility model provides an electronic device that includes a CAN bus activity detection and wake-up circuit as described in Embodiment 1 of this utility model.

[0050] It should be noted that by integrating the circuit into the electronic device, this utility model solves the problems of high power consumption and unreliable wake-up, and achieves energy saving and stable operation.

[0051] This embodiment provides a system application example based on the aforementioned CAN bus activity detection and wake-up circuit. The system aims to achieve low-power operation and reliably wake up from valid communication activity on the bus.

[0052] The system mainly includes the following functional units: Microcontroller (MCU): As the control core of the system, it is responsible for monitoring wake-up signals and managing the power consumption mode of the device.

[0053] CAN bus interface circuit: It consists of a CAN transceiver (U5), a magnetic coupling isolation device (U1) and an external resistor network. It is responsible for connecting the physical CAN bus and providing electrical isolation and conditioning for CANH and CANL signals.

[0054] Signal detection and processing circuit: It consists of a voltage comparator, a clamping protection device (U2) and RC components. Its core function is to detect the bus activity status and generate a corresponding wake-up signal.

[0055] Power conversion circuit: Used to convert the input power into the operating voltage required by each chip in the system.

[0056] The working principle and process of this system include: The system's operation is based on the characteristics of the CAN bus differential signal: when the bus is idle, the voltages CANH and CANL are equal; when there is data transmission, a dominant level (i.e., voltage difference) is generated between CANH and CANL.

[0057] The signal detection logic of this system includes: The two inputs of the voltage comparator receive the isolated CANH and CANL signals, respectively. When the bus is idle (CANH=CANL), the voltages at the two input terminals of the voltage comparator are equal, and its output is low, which is sent to the microcontroller's wake-up pin (WK_UP). When there is data activity on the bus (CANH ≠ CANL), the output of the voltage comparator flips to a high level regardless of whether CANH is higher or lower than CANL, thus making the WK_UP pin high.

[0058] The system's state control includes: Wake-up process: The microcontroller continuously monitors its WK_UP pin. Once the pin level changes from low to high, the microcontroller determines that there is valid activity on the bus, and then controls the entire system to exit sleep mode and enter normal working state to execute the corresponding communication and control tasks.

[0059] Entering or Maintaining Sleep Mode: The microcontroller can autonomously enter sleep mode based on specific instructions or conditions. During sleep mode, if the WK_UP pin remains low for a set time limit, the microcontroller will maintain the system's sleep state, thereby achieving energy saving.

[0060] Furthermore, this timeout is a configurable parameter, and its specific value depends on the communication protocol cycle of the target application scenario. For example, in a typical multi-split air conditioning system application, the cycle for completing one round of data transmission is approximately 40 seconds. Therefore, if no bus activity is detected for 40 seconds, it is reasonable to conclude that the system has entered a stable low-power idle state, in which case the timeout can typically be configured to 40 seconds.

[0061] Through the above methods, the system described in this embodiment achieves accurate and reliable detection of CAN bus activity, has the advantages of strong anti-interference ability and low false wake-up rate, and effectively optimizes overall energy consumption.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. A CAN bus activity detection and wake-up circuit, applied to electronic devices, characterized in that, The circuit includes: The CAN bus interface circuit, signal detection and processing circuit, and controller include: The input terminal of the CAN bus interface circuit is connected to the CAN bus and is used to electrically isolate the CANH signal and the CANL signal. The signal detection and processing circuit includes a voltage comparator. The non-inverting input and inverting input of the voltage comparator receive the CANH signal and the CANL signal, which are electrically isolated by the CAN bus interface circuit, respectively, and are used to detect the voltage difference between the CANH signal and the CANL signal. The output of the voltage comparator is connected to the wake-up pin of the controller. The controller is used to monitor the level of the wake-up pin. When the level of the wake-up pin is active, it controls the electronic device to switch from sleep mode to normal operation mode.

2. The CAN bus activity detection and wake-up circuit according to claim 1, characterized in that: The CAN bus interface circuit includes a transceiver, a magnetic coupling device, and a first matching resistor network, wherein: The transceiver includes a CANH signal terminal and a CANL signal terminal; The first matching resistor network is connected to the CANH signal terminal and the CANL signal terminal, and is used to provide input signals to the magnetic coupling device.

3. The CAN bus activity detection and wake-up circuit according to claim 2, characterized in that: The first matching resistor network includes a first resistor, a second resistor, and a third resistor, wherein: The first resistor is connected in series between the CANH signal terminal and one end of one winding of the magnetic coupling device; The second resistor is connected in series between the CANL signal terminal and the other end of one winding of the magnetic coupling device; The third resistor is connected in parallel across the two ends of one winding of the magnetic coupling device.

4. The CAN bus activity detection and wake-up circuit according to claim 3, characterized in that: The signal detection and processing circuit includes a second matching resistor network, a clamping protection circuit, and a comparison and driving circuit, wherein: The second matching resistor network is connected to the output terminal of the CAN bus interface circuit and is used to perform impedance matching on the CANH and CANL signals output by the CAN bus interface circuit. The clamping protection circuit is connected between the two output terminals of the second matching resistor network and is used to provide overvoltage protection for the impedance-matched CANH and CANL signals. The comparison and drive circuit is connected to the two output terminals of the second matching resistor network to perform level comparison on the CANH signal and the CANL signal, and outputs the corresponding level to the wake-up pin of the controller based on the level comparison result.

5. The CAN bus activity detection and wake-up circuit according to claim 4, characterized in that: The second matching resistor network includes a fourth resistor, a fifth resistor, and a sixth resistor, wherein: The fourth resistor is connected in parallel across the two ends of the winding on the other side of the magnetic coupling device; The fifth resistor is connected in series between one end of the other winding of the magnetic coupling device and the non-inverting input of the voltage comparator. The sixth resistor is connected in series between the other end of the winding on the other side of the magnetic coupling device and the inverting input of the voltage comparator.

6. The CAN bus activity detection and wake-up circuit according to claim 4, characterized in that: The clamping protection circuit includes a clamping device connected between the non-inverting input and the inverting input of the voltage comparator.

7. The CAN bus activity detection and wake-up circuit according to claim 4, characterized in that: The comparison and drive circuit includes a voltage comparator, a seventh resistor, a tenth resistor, and a diode, wherein: The non-inverting input of the voltage comparator is grounded via the seventh resistor; The tenth resistor is connected in series between the output terminal of the voltage comparator and the inverting input terminal of the voltage comparator; The anode of the diode is connected to the output of the voltage comparator, and the cathode is connected to the wake-up pin of the controller.

8. The CAN bus activity detection and wake-up circuit according to claim 1, characterized in that: The voltage comparator is used to compare the voltage magnitudes of the CANH and CANL signals. When there is a voltage difference between the CANH and CANL signals, it outputs a high level; otherwise, it outputs a low level.

9. An electronic device, characterized in that, It includes a CAN bus activity detection and wake-up circuit as described in any one of claims 1-8.

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