Multi-channel full-isolation digital transmitter based on CANOpen protocol

Abstract

The utility model relates to the technical field of industrial automation field data acquisition, in particular to a multichannel full-isolation digital transmitter based on a CANOpen protocol. Comprising an isolation power supply module, the input end of which is connected with a 24V DC power supply, and a switching power supply chip integrated with PWM / PFM dual-mode control drives a high-frequency transformer to generate three paths of isolation output power supplies which respectively supply power to a sensor signal conditioning circuit, an MCU control module, a peripheral circuit of the MCU control module and a CAN interface circuit. According to the utility model, by integrating the PWM / PFM dual-mode controlled switching power supply chip and the high-frequency transformer, three paths of isolated output power supplies are generated and respectively supply power to the sensor signal conditioning circuit, the MCU control module, the peripheral circuit of the MCU control module and the CAN interface circuit, so that the anti-interference performance of the system is effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to industrial automation field data acquisition technical field, concretely is a kind of multi-channel full isolation digital transmitter based on CANOpen protocol. BACKGROUND

[0002] In the field of industrial automation and automobile control, the data acquisition system based on CAN bus is widely used due to its high reliability, strong error correction ability and high transmission efficiency. Especially in multi-channel data acquisition system, compared with serial data acquisition system, multi-channel parallel data acquisition has the characteristics of concurrent high speed and strong real-time, which can significantly improve the efficiency and accuracy of data acquisition. However, there are still some problems in the multi-channel data acquisition system in the prior art that need to be solved:

[0003] Firstly, due to the complexity of industrial field environment, there are many strong interference sources, and the traditional data acquisition system performs poorly in terms of anti-interference performance, especially in the power supply part, its anti-interference ability directly affects the stability and reliability of the whole system. Secondly, the existing multi-channel data acquisition system usually uses fixed range ADC chip, which cannot adaptively adjust the sampling parameter, resulting in difficulty in guaranteeing the measurement accuracy in different resistance value range. In addition, the electrical isolation design between the signal conditioning circuit and MCU in the traditional system is not perfect, which is easy to introduce additional noise and error. SUMMARY

[0004] The utility model provides a kind of multi-channel full isolation digital transmitter based on CANOpen protocol to solve how to build a kind of full isolation digital transmitter with high anti-interference performance and can realize multi-channel parallel data acquisition in complex industrial environment to ensure the technical problem of high accuracy and stability of data acquisition in view of the technical problems existing in prior art.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] A kind of multi-channel full isolation digital transmitter based on CANOpen protocol is provided, comprising:

[0007] The isolation power module is connected to a 24V DC power supply at the input end, and generates three isolated output power supplies through a high-frequency transformer driven by an integrated PWM / PFM dual-mode control switching power supply chip, to supply power to the sensor signal conditioning circuit, MCU control module and its peripheral circuit and CAN interface circuit respectively;

[0008] The multi-channel parallel data acquisition module comprises at least four independent sensor signal conditioning and AD conversion units, each unit comprising a strain sensor differential signal input end, a low-pass filter circuit, an anti-aliasing filter and a 24-bit sigma-delta type AD conversion chip, and a two-wire SPI interface of the AD conversion chip is connected to an SPI bus of the MCU control module through a high-speed capacitive grid isolator;

[0009] The MCU control module adopts a 32-bit vehicle-grade single-chip microcomputer, internally integrates a CAN controller and a CANOpen protocol stack solidified in a FLASH, an SPI bus is connected to the AD conversion chip of each channel through an isolated signal line, and the CAN controller is connected to a CAN interface module through an isolated transceiver.

[0010] The configuration module comprises a DIP switch, high five-bit signal lines of which are connected to a GPIO port of the MCU control module to configure a CAN bus baud rate, and low seven-bit signal lines of which are connected to a GPIO port of the MCU control module to set a node address.

[0011] A logic side power supply of the isolated transceiver of the CAN interface module is powered by one output of the isolated power supply module.

[0012] Further, a voltage detection end of the switching power supply chip is connected to a secondary side winding of a high-frequency transformer through a voltage dividing resistor, a current detection end is connected to a primary winding loop through a sampling resistor, a secondary side winding output end of the high-frequency transformer is rectified through a Schottky diode, and then three isolated output power supplies are obtained through filtering by filter capacitor groups; one output is converted into a 5V power supply by a linear voltage stabilizer to power the CAN interface module, another output is converted into a 5V power supply by a three-terminal voltage stabilizer and a precision reference chip to power sensor signal conditioning circuits in the multi-channel parallel data acquisition module, and a third output is used to power the MCU control module and channel ADC digital power supplies through a pi-type filter circuit.

[0013] Further, each sensor signal conditioning circuit comprises a low-pass filter and an anti-aliasing filter, a gain pin of the AD conversion chip is fixedly connected to a high level to enable 128 times amplification, a conversion rate selection pin is configured as 10SPS or 80SPS, an analog 5V power supply is used as a reference voltage, and a two-wire SPI interface of the AD conversion chip is connected to an SPI bus of the MCU control module through a high-speed capacitive grid isolator.

[0014] Further, the MCU control module is internally integrated with a CAN controller, an SPI bus interface and a FLASH, the FLASH has a complete CANOpen protocol stack solidified therein, supports multiple CANOpen protocols, the SPI bus is connected to AD conversion chips of each channel through isolated signal lines, and the CAN controller is connected to the CAN interface module through an isolated transceiver.

[0015] Further, the high five-bit signal line is connected to a GPIO port of the MCU control module after pull-up resistance to configure a CAN bus baud rate, and the low seven-bit signal line is connected to the GPIO port of the MCU control module after pull-up resistance to set a node address, and the MCU control module further comprises a state lamp circuit for displaying CAN sending, system working and CAN receiving states.

[0016] Further, a logic side power supply of the isolated transceiver is powered by a 5V output of the isolated power supply module, CANH / CANL ends of the isolated transceiver are connected to an external CAN bus through transient suppression diodes and RC absorption circuits, and the logic side and the CAN bus side of the isolated transceiver are isolated through an optical coupling.

[0017] Further, the single-chip microcomputer further comprises an SWD interface for program simulation download, and the MCU control module further comprises a reset circuit composed of a resistor and a capacitor in series, and GPIO ports of the MCU control module are connected to AD conversion chips of each channel through isolated signal lines for high-speed data acquisition and transmission.

[0018] The utility model discloses the beneficial effect is:

[0019] The utility model discloses through the switching power supply chip and high frequency transformer of integration PWM / PFM dual mode control, generates three way isolation output power, respectively to sensor signal conditioning circuit, MCU and its peripheral circuit and CAN interface circuit power supply, effectively improved the anti -interference performance of system. Meanwhile, adopt 24 sigma-delta type AD conversion chip to carry out multichannel parallel data acquisition, and each channel is equipped with low pass filter and anti aliasing filter, has guaranteed the purity and sampling accuracy of signal. MCU control module adopts 32 vehicle level singlechip, and internally integrated with CAN controller and solidified CANOpen protocol stack in FLASH, has realized efficient data processing and communication function. Through the dial switch configuration CAN bus baud rate and node address, has simplified the system setting. In addition, each functional module is through high -speed capacitor grid isolator and carries out electrical isolation, further reduces the influence of noise and interference. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is hardware structure diagram of the utility model.

[0021] Figure 2 The power regulation circuit diagram of the utility model;

[0022] Figure 3 The four channel sensor signal conditioning and AD conversion circuit diagram of the utility model;

[0023] Figure 4 The MCU minimum system circuit diagram of the utility model;

[0024] Figure 5 The baud rate, node address configuration and status lamp circuit diagram of the utility model;

[0025] Figure 6 The isolation CAN interface circuit diagram of the utility model. DETAILED DESCRIPTION

[0026] In order to make the utility model's purpose, technical scheme and advantage more clearly clear, the following combines with the embodiment, to the utility model carries out further detailed explanation. The example of the embodiment is shown in the drawing, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary, only for explaining the utility model, and cannot be understood as limiting the utility model. In addition, it should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model.

[0027] In the description of the utility model, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected, can be mechanical connection, can also be electrical connection or can communicate with each other, can be directly connected, can also be indirectly connected through intermediate medium, can be the communication or interaction relationship between two elements inside two elements. For ordinary skilled in the art, the above-mentioned terms can be understood according to the specific meaning of the utility model.

[0028] The disclosure below provides many different embodiments or examples for implementing various aspects of the present application. In the interest of simplifying the present application, the following description will be directed to particular examples. However, it will be understood that they are included in the present application and are merely meant to be illustrative. Further, the present application can utilize different examples of the various processes and materials, as will be appreciated by one of ordinary skill in the art, and their use in the various examples is intended to be illustrative in nature.

[0029] The present application provides the following preferred embodiments:

[0030] In order to solve the problem of improving the anti-interference performance of the data acquisition system and the precision of multi-channel parallel data acquisition in a complex industrial environment, the embodiment discloses a multi-channel full-isolation digital transmitter based on a CANOpen protocol, and specifically, the embodiment also optimizes the design of a power module, a signal conditioning circuit, an ADC conversion circuit, an MCU control module, and a CAN interface circuit.

[0031] As Figure 1 The hardware structure block diagram of the present application is shown, the system power supply adopts 24VDC widely used in industry, the switching power supply control chip with PFM and PWM functions and intermittent and continuous regulation function is used to control the EPC13 high-frequency transformer magnetic core to obtain three-way isolation output power supply, which is used to supply power to the sensor and its signal conditioning circuit and ADC, MCU and peripheral circuit and CAN interface circuit in the figure, each channel uses 24bit high-resolution ADC, the sensor and signal conditioning circuit are isolated from the MCU circuit through a high-speed capacitor grid isolator, and data interaction is realized through isolated 2-wire SPI. The MCU uses a high-performance vehicle-grade 32-bit STC32 series 51 single-chip microcomputer, which integrates a CAN bus controller, an SPI bus, a large-capacity FLASH, and an SRAM, etc. in the internal FLASH of the MCU, the CANOpen protocol stack is solidified, all functions of the CANOpen protocol are supported, such as SDO, PDO, NMT, node daemon, etc., and the CAN interface chip uses an isolated and transceiving integrated CAN isolation chip.

[0032] As Figure 2The system power supply circuit diagram is shown, wherein U2 is a power supply control chip suitable for various network topologies and output feedback feedback modes produced by a source company, integrates CCM (continuous mode) and DCM (discontinuous mode), and has PWM and PFM adjustment modes, so that the switching power supply has good performance in stability, dynamic response and light load characteristics. T1 is a high-frequency transformer, the magnetic core adopts EPC13, three groups of secondary winding, F1, D7 and D1 provide overcurrent and overvoltage protection and anti-reverse protection functions for the system, R1 and R4 provide voltage detection for U2 to realize overvoltage and undervoltage protection mechanism of U2, R2 provides current detection for U2, R3, C2 and D4 provide high voltage clamping to further realize protection of U2, U4 is a linear optocoupler, which realizes SSR feedback through U6 and related discrete devices, and the secondary winding voltage output is rectified through D2, D3 and D5 and then filtered to obtain three power supplies 8VCC, 8VA and VCC, 8VCC is stabilized by U9 to obtain 5V 5VCC2 for power supply of the CAN interface circuit, 8VA is stabilized by three-terminal voltage regulator U8 and precision reference chip U7 to generate a power supply 5VA with a load capacity of about 1A for power supply of the sensor and the signal conditioning circuit, and 5VA is filtered by a 0-ohm resistor and related capacitors to obtain 5VCC for providing ADC digital power supply of each channel.

[0033] Further, as shown in Figure 3 The shown is four-channel sensor signal conditioning and AD conversion circuit, each channel sensor has independent signal conditioning and AD conversion circuit, 4 parallel sensor signal conditioning circuits are basically same, and the function of the circuit is explained by taking the first channel as an example.

[0034] Further, SIG1+ and SIG1- are differential signals output by the first channel sensor, which are sent to 24-bit sigma-delta type AD conversion chip CS1231 for AD conversion after low-pass filtering and anti-aliasing filtering, and TV2 and TV4 in the figure are transient suppression diodes, which prevent damage of U11 caused by surges. U11 internally integrates 64 times and 128 times PGA, the fourth pin (GAIN) of which is 128 times when connected to high level, the utility model is fixed at 128 times amplification, the 13th pin (SPEED) of which is conversion rate selection, low level is 10 SPS, and high level is 80 SPS. U11 internally integrates a clock, the reference voltage adopts analog 5V power supply 5VA, U15 is a two-in-one-out capacitor grid high-speed isolator, and the two-wire SPI interface and conversion rate configuration of U11 are realized by data interaction of U15 and the related I / O port of the MCU.

[0035] Further, as shown in Figure 4The MCU minimum system circuit is shown.The U1 in the figure is a high-performance 32-bit MCU based on 51 core, which is integrated with CAN bus controller complying with CAN2.0A and CAN2.0B, 128 KB FLASH, 12 KB SRAM, internal low drift clock, power-on reset circuit, and the like, and has high integration and rich internal resources, so that the hardware circuit can be simplified, stability is improved, and the necessary hardware support is provided for software such as CANOpen protocol stack.P1 is a SWD interface, through which program simulation and download can be realized.The network numbers SW1-SW12 in the figure reflect the electrical connection and are connected with dial switches, which are used for setting the baud rate and address of the CAN node, SCK1-SCK4 and SDO1-SDO4 are analog two-wire SPIs, which are used for reading the AD conversion results of each channel, SPD1-SPD4 are used for configuring the conversion rate of the ADC of each channel, and CAN_R and CAN_T are the CAN controller interfaces integrated in the MCU.

[0036] Further, as shown in Figure 5 The CAN bus baud rate, node address configuration and state lamp circuit are shown.S1 is a dial switch, the high 5 bits of which are used for configuring the baud rate of the CAN bus, and the low 7 bits of which are used for setting the ID of the CAN digital transmitter, and the setting range is 0-127, wherein 0 is the broadcast address.RP1 and RP2 are resistors, which provide pull-up function.Three state lamps LED1-LED3 are used for displaying the states of CAN sending, system working and CAN receiving, and the like.

[0037] Further, as shown in Figure 6 The isolation CAN interface circuit of the utility model is shown.U5 in the figure is a special CAN isolating transceiver integrated with isolation and transceiving, which has higher integration and reliability compared with independent isolator and transceiver.R8 and R10 are used for absorbing the bus reflection signal and transient suppression of U3, preventing the damage of surge signal to U5, R13, R14 and C15 further absorb the interference signal on the bus, so that the reliability and stability of CAN bus communication can be improved.

[0038] The utility model has the advantages that the above-mentioned is only the preferred embodiment of the utility model, and is not used to limit the utility model, any modification, equivalent replacement, improvement and the like made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A multi-channel fully isolated digital transmitter based on CANOpen protocol, characterized in that, The application relates to a multi-channel parallel data acquisition module, which comprises at least four independent sensor signal conditioning and AD conversion units, each unit comprising a strain sensor differential signal input end, a low-pass filter circuit, an anti-aliasing filter and a 24-bit sigma-delta type AD conversion chip, wherein two-wire SPI interfaces of the AD conversion chips are connected with an SPI bus of an MCU control module through high-speed capacitive grid isolators. The MCU control module adopts a 32-bit vehicle-grade single-chip microcomputer, internally integrates a CAN controller and a CANOpen protocol stack solidified in a FLASH, the SPI bus is connected with the AD conversion chips of each channel through isolated signal lines, and the CAN controller is connected with a CAN interface module through an isolated transceiver. The configuration module comprises a code switch, high five-bit signal lines of which are connected with GPIO ports of the MCU control module to configure a CAN bus baud rate, and low seven-bit signal lines of which are connected with GPIO ports of the MCU control module to set a node address. A logic side power supply of the isolated transceiver of the CAN interface module is powered by one-way output of the isolated power supply module. A voltage detection end of the switching power supply chip is connected with a secondary side winding of the high-frequency transformer through a voltage dividing resistor, a current detection end is connected with a primary winding loop through a sampling resistor, and a secondary side winding output end of the high-frequency transformer is rectified through a Schottky diode and then filtered through a filter capacitor group to obtain three-way isolated output power supply. One-way output is converted into 5V power supply through a linear voltage stabilizer to power the CAN interface module, another-way output generates 5V power supply through a three-terminal voltage stabilizer and a precision reference chip to power the sensor signal conditioning circuit in the multi-channel parallel data acquisition module, and third-way output powers the MCU control module and each channel ADC digital power supply through a pi-type filter circuit.

2. The multi-channel fully isolated digital transmitter based on CANOpen protocol as claimed in claim 1, wherein, Each sensor signal conditioning circuit comprises a low-pass filter and an anti-aliasing filter, a gain pin of the AD conversion chip is fixedly connected with a high level to enable 128 times amplification, a conversion rate selection pin is configured as 10 SPS or 80 SPS, an analog 5V power supply is used as a reference voltage, and two-wire SPI interfaces of the AD conversion chip are connected with the SPI bus of the MCU control module through high-speed capacitive grid isolators. The MCU control module internally integrates a CAN controller, an SPI bus interface and a FLASH, the FLASH solidifies a complete CANOpen protocol stack, supports multiple CANOpen protocols, the SPI bus is connected with the AD conversion chips of each channel through isolated signal lines, and the CAN controller is connected with the CAN interface module through an isolated transceiver.

3. The multi-channel fully isolated digital transmitter based on CANOpen protocol according to claim 1 or 2, characterized in that, ​ 4. The multi-channel fully isolated digital transmitter based on CANOpen protocol as claimed in claim 1, wherein, ​ 5. The multi-channel fully isolated digital transmitter based on CANOpen protocol as claimed in claim 1, wherein, The high five signal line is connected to the GPIO port of the MCU control module after pull-up to configure the CAN bus baud rate, and the low seven signal line is connected to the GPIO port of the MCU control module after pull-up to set the node address, the MCU control module further comprises a state lamp circuit for displaying CAN sending, system working and CAN receiving states.

6. The multi-channel fully isolated digital transmitter based on CANOpen protocol as claimed in claim 1, wherein, The logic side power supply of the isolation transceiver is powered by a 5V output of the isolation power module, the CANH / CANL end of the isolation transceiver is connected to the external CAN bus through transient suppression diodes and RC absorption circuits, and the logic side and the CAN bus side of the isolation transceiver are isolated through optical coupling.

7. The multi-channel fully isolated digital transmitter based on CANOpen protocol as claimed in claim 1, wherein, The single-chip microcomputer further comprises an SWD interface for program simulation download, and the MCU control module further comprises a reset circuit composed of a resistor and a capacitor in series, and the GPIO port of the MCU control module is connected to the AD conversion chip of each channel through an isolated signal line for high-speed data acquisition and transmission.

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