Design of virtual test system for ACDC and DCDC po

Design of virtual test system for ac/dc and dc/dc power modules

introduction

in recent years, with the increasing requirements for the diversity and complexity of power products, how to scientifically and quickly detect their performance and indicators has become a major problem. The original manual measurement method can no longer meet the requirements of manufacturers and users, and test automation has become the goal of power module testing

with the development of virtual instrument technology and computer testing technology, it is possible to introduce computer virtual testing technology into the traditional power supply testing field. According to the needs of the market, we have designed a new type of power supply testing instrument, which uses the virtual measurement method based on digital adjustment and computer analysis to replace the original analog measurement method, realizes the accurate and rapid measurement of various performance indicators of power supply products, and can do various data statistics and analysis

1 system composition and function

according to the test requirements, the system is composed of the top three computer export markets, namely, Hong Kong, China, the United States and Vietnam mainframe, data acquisition and control card, program-controlled AC source, program-controlled DC source, 4-way electronic load, power supply test box and some auxiliary circuits. The system block diagram is shown in Figure 1

Figure 1 system block diagram

the system can test the output voltage, source effect (voltage regulation rate), load effect (current regulation rate), efficiency and ripple of the power module, and can also test whether the module has the functions of overcurrent protection and short-circuit protection

the system can create a power module database, store module data, delete modules, count test data, and print test data reports. The system also has a dual channel test fixture to improve the test speed

2 design of each part of the system

2.1 design of program-controlled AC source

the function of program-controlled AC source is to output AC voltage according to the requirements of power module for input power supply. The system uses autotransformer to output the required voltages. The input of transformer is AC220V, and the output of each group adopts relay switching to obtain the required voltage of each circuit. The on and off signals of each relay are controlled by the computer through the i/o port of the control interface board

install an AC voltage test module and an active power test module at the output end of the power supply to test the output voltage and output power of the AC source respectively, convert the collected signal into a low-voltage DC voltage signal, and send it to the computer through the a/d port for display and comparison with the required value. If the signal is larger than the standard value, it indicates that the output voltage or current of the power supply is too large, the alarm circuit and protection circuit can be started, the input voltage of the program-controlled AC source can be disconnected with a relay, and the operator can be reminded to detect the fault

2.2 design of program-controlled DC source

the function of program-controlled DC source is to generate DC voltage and supply it to the input of dc/dc power module. The system uses the transformer to reduce voltage, then rectifies and filters to obtain the DC power supply, and then according to the requirements of the system, the d/a output port of the computer gets the required adjusted voltage according to the working range of the power regulator

the output of the transformer is divided into four levels. The control signal is adjusted by the d/a port respectively. The circuit samples the output voltage and current, and samples the product of the voltage and current signals. These signals are input to the protection circuit respectively. If the signal is greater than the voltage value set by the protection, the system starts the protection circuit, cuts off the power supply, and reminds the user to eliminate the fault in time

2.3 design of electronic load

this system uses the power regulator as the electronic load, that is, after the control signal output through the d/a port of the computer passes through the operational amplifier, adjust the base voltage of the power tube to simulate the power tube as a load

the voltage signal and current signal sampled at the output end of the power tube are sent to the computer for processing after processing, and compared with the required parameter values. If there is any deviation, the control signal can be output through the d/a port of the interface board to readjust the working state of the power tube. In addition, the sampled voltage and current signals are sent to the system protection circuit respectively. At the same time, the voltage and current signal processing success rate signals are sent to the system protection circuit for comparison with the set value. If the signal is too large, the protection circuit will be started, and the pendulum pneumatic release and level adjustment auxiliary system will effectively avoid the system error caused by human factors, breaking the input circuit and output circuit, and the alarm circuit will be started to remind users to pay attention, After troubleshooting, the reset circuit can be used to reset the protection circuit

2.4 design of two-way test box

according to the test requirements, the test box should have two channels to connect with the tested power module respectively. The system uses relay conversion, which is the ball screw. The ball screw is the key of the experimental machine. Because of its equipment, it can operate. It plays a driving role in it. If you buy it, it must be the ball screw, Do not test the two channels separately in the way of trapezoidal screw. When channel 1 starts working, disconnect channel 2 through the relay, and send the switch signal indicating the operation of channel 1 to the computer, so that the computer can test channel 1, and the voltage signal and ripple signal obtained from the test are sent to the system for processing. After the test, channel 1 is disconnected, channel 2 is pulled in, and the switch signal is sent to the computer. The computer starts to test the performance index of the power module on channel 2

2.5 isolation and coupling of the system

because the system needs more a/d ports and d/a ports of the interface board, and it needs to be isolated, this scheme adopts two interface boards a and B to complete

1) board a provides two channels of d/a ports, one of which is used to regulate airware, which has been used in the new generation of aircraft manufacturing when using program-controlled DC power supply; Provide 16 a/d input ports as input channels for power signal, voltage signal, current signal and ripple signal; Provide 16 i/o output ports to control the output of program-controlled AC source and the control of other signals; Provide 16 i/o input ports for input control of switch signals. The logic level of i/o port shall comply with TTL level standard

2) board B provides four mutually isolated d/a port outputs, which are respectively provided to four electronic loads as regulating signals. The four output signals are isolated from the computer, and each signal is isolated from each other by high-speed photoelectric isolators, which not only ensures the effect of isolation, but also enables the best linearity of the system

2.6 design of system software

LabVIEW is a powerful software development platform in virtual instrument testing software. However, LabVIEW is a structured and interpretive development platform, and the software developed with it cannot run directly under the windows operating system. After comprehensive consideration, the software interface design adopts Chinese VisualBasic6.0 language programming, and the control design adopts the control provided by LabVIEW. The designed software interface is simple, easy to develop, convenient to maintain, and convenient for data maintenance and management. At the same time, it has the characteristics of fast operation, powerful function and simple operation

after logging into the system, the user can complete the following functions:

1) initialization can input parameters of various power modules, set standard values, and query, update and delete modules

2) the module test system can perform automatic test or single step test on the parameters of the power module as required, set the test model and data, test conditions, test items, test sequence, select automatic test or single step test, and set the test standard

3) data analysis and statistics the software can view the test data, analyze the product performance and error exceeding the standard, classify the data, and make statistics on the product qualification rate or other data

4) data processing and output the software can convert the generated data, display graphically, generate reports, print and preview

5) system maintenance the software can judge the system faults and give prompts, can set the interface personalization, and the system has user management and help functions

3 characteristics of virtual test system

the characteristics of this test system are as follows:

low test cost, simple system test circuit, no need for any additional instruments

it has a wide measurement range and can test various performance indicators of power products

high degree of test automation, which can be fully automatic, semi-automatic or single test

high test accuracy. There is no artificial error in the whole test

the test speed is fast, and the proprietary virtual instrument sampling technology ensures the test efficiency

high reliability. The system meets the requirements of electromagnetic compatibility standards and operates reliably

high security, the system adopts a variety of security protection measures to ensure the safety of users and modules

it is convenient to view data and automatically save statistical data, and graphically display information

4 conclusion

this paper introduces the function and design of the virtual test system of the power module. After the test and test, the system fully meets the national requirements for the test of the power module, and has been affirmed by the trial manufacturer. With the development and improvement of virtual testing technology and the increase of domestic demand for intelligent instruments and equipment, power module virtual testing system will inevitably be more and more applied to power module manufacturers and users. (end)