Design of Switching Power Supply Monitoring System Based on CAN Bus Technology Zhang Jian, Li Hua (Automatic Control Department of Armored Force Engineering College, Beijing Parts and Software Design) discussed the design flow chart of field node and PC software.
With the rapid development of China's power electronics technology, industrial electrical equipment is increasingly strict with the requirements of power systems and power supplies, and the quality and level of maintenance management required by them are getting higher and higher. The wide application of computer technology in the field of power supply further requires centralized monitoring, less people or unattended requirements for power supply equipment. In order to change the traditional manual monitoring system and improve the management level of electrical equipment, the author developed a distributed monitoring system for the widely used switching power supply. In recent years, computer companies, equipment manufacturers, research institutes and other departments have developed power monitoring systems with different characteristics, among which the data acquisition network control parts are different. These monitoring systems are highly targeted and are used exclusively for switching power supplies. There are not many monitoring systems, and the cost is high for some small and medium-sized electrical equipment or test equipment, and the portability is relatively poor. The portable power supply developed by our room has an input voltage of 220V or 380V AC, and the output is 24V00A. It has the characteristics of large capacity, small size, high efficiency, etc., and can be connected in any parallel, with automatic current sharing and other functions. According to the use and maintenance requirements of the electrical equipment, multiple switching power supplies can be connected in parallel to form a power supply system, and the monitoring system is used to realize remote monitoring of the power supply system. The system can monitor the operation status of the power supply equipment in real time, and can even monitor the working status of the power equipment at the same time according to the needs. The working parameters of the power supply can be set remotely through the field or the computer, and have the characteristics of fault location, alarm monitoring, etc., and can be dynamic. The site is extended to the site, which has the advantages of convenient maintenance and strong scalability.
1 system structure field node for data acquisition and control, using bus-type network structure, CAN bus 2.0A protocol, communication medium is twisted pair. The on-site node samples the analog quantity, compares the data with the preset value, and adjusts the parameters of the switching power supply according to the control law to make the switching power supply reach the working requirement. And pass the data to the host computer. Here, field node monitoring function may be implemented using two kinds of chip A microcontroller with CAN port, and the other TI's DSP. TMS320F243. Microcontroller as the core plate features a power supply system and a control CC1 The algorithm is relatively simple, the network data throughput is not large, and the control precision and real-time requirements are not very high. The function board CC2 with TMS320F243 as the core is mainly used for network data throughput, and the internal control algorithm of the power supply is more complicated. Field equipment, real-time, high-precision control system. Which function board is used in a specific application, depending on the requirements of the field device. And these two functions can communicate with each plate, which is very flexible in terms of the composition of the network, both the two functions may be used singly plate, may be used in combination, to meet the needs of different power supply system consisting of a switching power supply, thus saving Expenditure fully reflects the flexibility of the system. Extension panel has two functions sampling interface can monitor the status of electrical equipment, while the remote monitoring staff to better understand the operation of the device.
From the composition of the power supply system, improve real-time monitoring aspects to consider are recommended to use the following network of structures.
1.1 Networking Mode For a power supply system consisting of fewer switching power supplies, you can use a daisy chain to form a network, for example.
When the accuracy of the switching power supply is high, CC1 can be replaced by CC2. Since the CAN adapter card supports the CAN2.0A protocol, the DSP supports the CAN2.0B protocol, and the DSP must be used when communicating with the CAN adapter card. packet format into a standard format is provided, where the DSP identifier valid only 5 to 12.
For the power supply system composed of more switching power supplies, the data transmission amount in the network is very large, and when strict control precision is required, the multi-level network structure is adopted, and the maintenance is also very convenient. According to the actual situation, CC1 and CC2 can also be mixed. Currently, the monitoring system can monitor 16 field nodes as needed.
1.2CAN design In the design of this system, the stability is the first. In order to improve the efficiency and stability of network communication, we must first ensure that the network bandwidth is greater than the frame rate of the network and avoid the data loss of the node. In this system, the number of field nodes is small. By setting the identifier to the power number to be monitored by the system and adding an appropriate delay time in the software, the efficiency of receiving and transmitting frames of the system can be greatly improved. The design method of the system CAN is as follows: determine the maximum distance between the switching power supply and the upper computer in the system, as the basis for determining the propagation segment in the system bit time, and if necessary, considering the future system expansion, the extended maximum Distance is the basis for the propagation segment. The disadvantage of this is that the current bit rate of the network is slow.
Determine the system bit rate. If the system uses CC2 to communicate with the CAN adapter card, the bit rate of the CAN adapter card must be the same as the bit rate of the DSP. However, since the clock frequency of the CAN adapter card and the DSP are different, it is better to ensure that the respective system clocks Tscl are the same when configuring the respective registers, which can often reduce the error rate. And when determining the bit rate, there are often multiple configurations to choose from, and the parameter configuration with the highest oscillator tolerance range should be selected.
The maximum oscillator tolerance range is determined by the node in the system that has the highest oscillator tolerance range. The maximum oscillator tolerance range must satisfy the following two conditions: I, fmin (phase buffer segment 1, phase buffer segment 2) itdf <synchronous jump width 1: df2* (13 * bit time - phase buffer segment 2)': Df20* bit time If the bit rate is low, you can ignore this step.
If the bit rate is high, the requirements must be strict. First, determine the delay between the CAN adapter card and the DSP input and output delay time and the maximum signal propagation time in the network. The configuration is the propagation segment in time. Total share between inches Shearwater: / share the number is even, the phase should be when "sowing Segment 1 Segment 2 = phase or phase segment 1 Phase Segment 2 = + 1, and the phase of the minimum length of the buffer section 2 does not It should be less than the information processing time of the controller. Normally, it should be greater than 2 time shares.
Determine the bandwidth of the network, that is, the reciprocal of the transmission time of one frame (sent by the node farthest from the host computer in the network). Then determine the frame rate of the network, that is, the number of data frames generated by the network per unit time. In order to ensure that the bandwidth is greater than the frameout rate, a certain delay time is set in the software. If the system expands the node, the delay time should be reconsidered.
2 system hardware design CC2 in the network communication and control functions are mainly implemented by TMS320F243, CC1 in the network communication and control functions are mainly implemented by the 196CA microcontroller. The TMS320F243 chip has 8 channels of A/D and 6 channels of PWM output. The chip also has a CAN controller that fully complies with the CAN2.0B protocol. It is connected to TI's CAN transmitter SN75LBC031, and the data transmission rate can reach 500kbps/s. The real-time requirements of the monitoring system. There are digital tubes and keyboards on the function board, which can observe the working condition of the equipment on the spot, and can input the setting parameters dynamically, or set the power working parameters remotely through the computer. The communication function of CC1 is completed by the CAN controller on the 196CA, and the control is completed by the MCU with its peripheral devices, mainly A/D, D/A conversion chip and voltage controlled oscillator. The main functions of these two function boards are the same. Due to space limitations, only CC2 will be introduced here. Its hardware design is shown in the block diagram.
The node structure considers that when the network is fully loaded, the data transmission amount will be large. In order to improve the real-time performance of the monitoring, the network has universality and scalability, and the computer is connected to the CAN network through a CAN adapter card to improve the network data processing capability. And it makes the system easy to connect with other management networks, which is convenient for unified scheduling and management. To this end, the intelligent PCCAN card produced by Sanxingda Company is selected, which provides 9 functions, which can fully meet the needs after testing.
3 function board software design TMS320F243 program is written in assembly language, the flow chart is shown.
In order to avoid interference, the power supply outputs the same series of triangular wave comparisons, making the output into an observable pulse. By detecting the pulse width, the value of the power supply voltage and current is obtained. After filtering and data analysis, the data is transmitted to the upper computer.
The CAN controller configuration in DSP is based on the following two formulas: TSEG1=register value +1; TSEG2=register value 1:1, which is the most important place for readers to pay attention to, not to be confused with the configuration of CAN adapter card, otherwise it will The data in the network could not be received.
The function of CC1 is basically the same as that of CC2, which is omitted here.
4 PC software design The host computer realizes the remote monitoring function of the site node, analyzes and processes the large amount of data sent by the site node, and realizes the automatic control of the site node according to the preset control strategy, realizing the requirement of real-time control, and also can also According to the user's needs, let the user manually control the site node, the situation of the node can be dynamically displayed on the computer.
The upper computer software function is mainly realized by the nine functions provided by the adapter card. In order to better use computer resources, the software is designed by thread method. The software is written in C++BUILDER. The software design flow chart is shown.
The CAN adapter card provides PCCAN.DLL, PCCAN.LIB, PCCAN.H. When writing the application, copy PCCAN.DLL, PCCAN.LIB and PCCAN.H to the directory where the application is located. But BCB can't use the library function written in C language. At this time, you can use the tool IMPLIB brought by BCB to generate the LIB that BCB can refer to. The specific operation is as follows: Enter the directory where IMPLIB is located under DOS and type implibXXX.libPCCAN.dll, then Copy the generated XXX.lib to the application directory, and add EXTERN to all declared functions in PCCAN.h. Add xxx.lib to the application option and add "INCLUDEPCCAN.H*" to the front of the program. All CAN adapter card functions are called in the application 71994-2014 ChinaAcademicJournal program.
There are two bus timing registers in the CAN controller on the CAN adapter card. The bus timing register 0 can determine the value of the baud rate prescaler and the synchronous jump width. The lower 6 bits are used to determine the system clock. The upper 2 bits are used to determine the sync jump width. Bus timing register 1 determines the bit period width, the sample point position, and the number of samples taken at each sample point, and is calculated as follows: tTSEGi = tsd (8TSEG1. 1), where tcik is the clock period of the on-board oscillator. Here we need to pay attention to tTSEGi and tTSEG2. Their algorithms are the same as TSEG1 in Equation 1*1 and TSEG2 in Equation 1-2. If DSP is used in the network, it must be distinguished in the calculation process.
5 Conclusion After running and testing, the system proves that the data quality of the on-site node is reliable and the acquisition accuracy is high. The CAN bus technology makes the wiring flexible. The communication method breaks through the traditional master/slave limitation, and has fast response and real-time. Good character. The flexible use of the two function boards can meet the requirements of the extended equipment after the expansion, and has the advantage of strong expansion.
With the rapid development of China's power electronics technology, industrial electrical equipment is increasingly strict with the requirements of power systems and power supplies, and the quality and level of maintenance management required by them are getting higher and higher. The wide application of computer technology in the field of power supply further requires centralized monitoring, less people or unattended requirements for power supply equipment. In order to change the traditional manual monitoring system and improve the management level of electrical equipment, the author developed a distributed monitoring system for the widely used switching power supply. In recent years, computer companies, equipment manufacturers, research institutes and other departments have developed power monitoring systems with different characteristics, among which the data acquisition network control parts are different. These monitoring systems are highly targeted and are used exclusively for switching power supplies. There are not many monitoring systems, and the cost is high for some small and medium-sized electrical equipment or test equipment, and the portability is relatively poor. The portable power supply developed by our room has an input voltage of 220V or 380V AC, and the output is 24V00A. It has the characteristics of large capacity, small size, high efficiency, etc., and can be connected in any parallel, with automatic current sharing and other functions. According to the use and maintenance requirements of the electrical equipment, multiple switching power supplies can be connected in parallel to form a power supply system, and the monitoring system is used to realize remote monitoring of the power supply system. The system can monitor the operation status of the power supply equipment in real time, and can even monitor the working status of the power equipment at the same time according to the needs. The working parameters of the power supply can be set remotely through the field or the computer, and have the characteristics of fault location, alarm monitoring, etc., and can be dynamic. The site is extended to the site, which has the advantages of convenient maintenance and strong scalability.
1 system structure field node for data acquisition and control, using bus-type network structure, CAN bus 2.0A protocol, communication medium is twisted pair. The on-site node samples the analog quantity, compares the data with the preset value, and adjusts the parameters of the switching power supply according to the control law to make the switching power supply reach the working requirement. And pass the data to the host computer. Here, field node monitoring function may be implemented using two kinds of chip A microcontroller with CAN port, and the other TI's DSP. TMS320F243. Microcontroller as the core plate features a power supply system and a control CC1 The algorithm is relatively simple, the network data throughput is not large, and the control precision and real-time requirements are not very high. The function board CC2 with TMS320F243 as the core is mainly used for network data throughput, and the internal control algorithm of the power supply is more complicated. Field equipment, real-time, high-precision control system. Which function board is used in a specific application, depending on the requirements of the field device. And these two functions can communicate with each plate, which is very flexible in terms of the composition of the network, both the two functions may be used singly plate, may be used in combination, to meet the needs of different power supply system consisting of a switching power supply, thus saving Expenditure fully reflects the flexibility of the system. Extension panel has two functions sampling interface can monitor the status of electrical equipment, while the remote monitoring staff to better understand the operation of the device.
From the composition of the power supply system, improve real-time monitoring aspects to consider are recommended to use the following network of structures.
1.1 Networking Mode For a power supply system consisting of fewer switching power supplies, you can use a daisy chain to form a network, for example.
When the accuracy of the switching power supply is high, CC1 can be replaced by CC2. Since the CAN adapter card supports the CAN2.0A protocol, the DSP supports the CAN2.0B protocol, and the DSP must be used when communicating with the CAN adapter card. packet format into a standard format is provided, where the DSP identifier valid only 5 to 12.
For the power supply system composed of more switching power supplies, the data transmission amount in the network is very large, and when strict control precision is required, the multi-level network structure is adopted, and the maintenance is also very convenient. According to the actual situation, CC1 and CC2 can also be mixed. Currently, the monitoring system can monitor 16 field nodes as needed.
1.2CAN design In the design of this system, the stability is the first. In order to improve the efficiency and stability of network communication, we must first ensure that the network bandwidth is greater than the frame rate of the network and avoid the data loss of the node. In this system, the number of field nodes is small. By setting the identifier to the power number to be monitored by the system and adding an appropriate delay time in the software, the efficiency of receiving and transmitting frames of the system can be greatly improved. The design method of the system CAN is as follows: determine the maximum distance between the switching power supply and the upper computer in the system, as the basis for determining the propagation segment in the system bit time, and if necessary, considering the future system expansion, the extended maximum Distance is the basis for the propagation segment. The disadvantage of this is that the current bit rate of the network is slow.
Determine the system bit rate. If the system uses CC2 to communicate with the CAN adapter card, the bit rate of the CAN adapter card must be the same as the bit rate of the DSP. However, since the clock frequency of the CAN adapter card and the DSP are different, it is better to ensure that the respective system clocks Tscl are the same when configuring the respective registers, which can often reduce the error rate. And when determining the bit rate, there are often multiple configurations to choose from, and the parameter configuration with the highest oscillator tolerance range should be selected.
The maximum oscillator tolerance range is determined by the node in the system that has the highest oscillator tolerance range. The maximum oscillator tolerance range must satisfy the following two conditions: I, fmin (phase buffer segment 1, phase buffer segment 2) itdf <synchronous jump width 1: df2* (13 * bit time - phase buffer segment 2)': Df20* bit time If the bit rate is low, you can ignore this step.
If the bit rate is high, the requirements must be strict. First, determine the delay between the CAN adapter card and the DSP input and output delay time and the maximum signal propagation time in the network. The configuration is the propagation segment in time. Total share between inches Shearwater: / share the number is even, the phase should be when "sowing Segment 1 Segment 2 = phase or phase segment 1 Phase Segment 2 = + 1, and the phase of the minimum length of the buffer section 2 does not It should be less than the information processing time of the controller. Normally, it should be greater than 2 time shares.
Determine the bandwidth of the network, that is, the reciprocal of the transmission time of one frame (sent by the node farthest from the host computer in the network). Then determine the frame rate of the network, that is, the number of data frames generated by the network per unit time. In order to ensure that the bandwidth is greater than the frameout rate, a certain delay time is set in the software. If the system expands the node, the delay time should be reconsidered.
2 system hardware design CC2 in the network communication and control functions are mainly implemented by TMS320F243, CC1 in the network communication and control functions are mainly implemented by the 196CA microcontroller. The TMS320F243 chip has 8 channels of A/D and 6 channels of PWM output. The chip also has a CAN controller that fully complies with the CAN2.0B protocol. It is connected to TI's CAN transmitter SN75LBC031, and the data transmission rate can reach 500kbps/s. The real-time requirements of the monitoring system. There are digital tubes and keyboards on the function board, which can observe the working condition of the equipment on the spot, and can input the setting parameters dynamically, or set the power working parameters remotely through the computer. The communication function of CC1 is completed by the CAN controller on the 196CA, and the control is completed by the MCU with its peripheral devices, mainly A/D, D/A conversion chip and voltage controlled oscillator. The main functions of these two function boards are the same. Due to space limitations, only CC2 will be introduced here. Its hardware design is shown in the block diagram.
The node structure considers that when the network is fully loaded, the data transmission amount will be large. In order to improve the real-time performance of the monitoring, the network has universality and scalability, and the computer is connected to the CAN network through a CAN adapter card to improve the network data processing capability. And it makes the system easy to connect with other management networks, which is convenient for unified scheduling and management. To this end, the intelligent PCCAN card produced by Sanxingda Company is selected, which provides 9 functions, which can fully meet the needs after testing.
3 function board software design TMS320F243 program is written in assembly language, the flow chart is shown.
In order to avoid interference, the power supply outputs the same series of triangular wave comparisons, making the output into an observable pulse. By detecting the pulse width, the value of the power supply voltage and current is obtained. After filtering and data analysis, the data is transmitted to the upper computer.
The CAN controller configuration in DSP is based on the following two formulas: TSEG1=register value +1; TSEG2=register value 1:1, which is the most important place for readers to pay attention to, not to be confused with the configuration of CAN adapter card, otherwise it will The data in the network could not be received.
The function of CC1 is basically the same as that of CC2, which is omitted here.
4 PC software design The host computer realizes the remote monitoring function of the site node, analyzes and processes the large amount of data sent by the site node, and realizes the automatic control of the site node according to the preset control strategy, realizing the requirement of real-time control, and also can also According to the user's needs, let the user manually control the site node, the situation of the node can be dynamically displayed on the computer.
The upper computer software function is mainly realized by the nine functions provided by the adapter card. In order to better use computer resources, the software is designed by thread method. The software is written in C++BUILDER. The software design flow chart is shown.
The CAN adapter card provides PCCAN.DLL, PCCAN.LIB, PCCAN.H. When writing the application, copy PCCAN.DLL, PCCAN.LIB and PCCAN.H to the directory where the application is located. But BCB can't use the library function written in C language. At this time, you can use the tool IMPLIB brought by BCB to generate the LIB that BCB can refer to. The specific operation is as follows: Enter the directory where IMPLIB is located under DOS and type implibXXX.libPCCAN.dll, then Copy the generated XXX.lib to the application directory, and add EXTERN to all declared functions in PCCAN.h. Add xxx.lib to the application option and add "INCLUDEPCCAN.H*" to the front of the program. All CAN adapter card functions are called in the application 71994-2014 ChinaAcademicJournal program.
There are two bus timing registers in the CAN controller on the CAN adapter card. The bus timing register 0 can determine the value of the baud rate prescaler and the synchronous jump width. The lower 6 bits are used to determine the system clock. The upper 2 bits are used to determine the sync jump width. Bus timing register 1 determines the bit period width, the sample point position, and the number of samples taken at each sample point, and is calculated as follows: tTSEGi = tsd (8TSEG1. 1), where tcik is the clock period of the on-board oscillator. Here we need to pay attention to tTSEGi and tTSEG2. Their algorithms are the same as TSEG1 in Equation 1*1 and TSEG2 in Equation 1-2. If DSP is used in the network, it must be distinguished in the calculation process.
5 Conclusion After running and testing, the system proves that the data quality of the on-site node is reliable and the acquisition accuracy is high. The CAN bus technology makes the wiring flexible. The communication method breaks through the traditional master/slave limitation, and has fast response and real-time. Good character. The flexible use of the two function boards can meet the requirements of the extended equipment after the expansion, and has the advantage of strong expansion.
Motion control sensor is an original part that converts the change of non-electricity (such as speed, pressure) into electric quantity. According to the converted non-electricity, it can be divided into pressure sensor, speed sensor, temperature sensor, etc. It is a measurement, control instrument and Parts and accessories of equipment.
Remote Control Motion Sensor,Photocell And Motion Sensor,Homeseer Motion Sensor,Lutron Motion Sensor Caseta
Changchun Guangxing Sensing Technology Co.LTD , https://www.gx-encoder.com