Design Of The Testing System Of The Pulse Transformer Magnetic Core

As an important component of switching power supply, the performance of pulse transformer magnetic core is closely related to the one of switching power supply. Comparing with the measurement of electrical parameters, the magnetic parameter measurement is more complicated. As the limitation of technology, the pulse transformer core in current market has difficulty in consistency, which is a big problem to the manufacturers, and the pulse transformer core tester which can meet the requirements of magnetic core screening is also uncommon. In this paper, a magnetic measurement system is designed to measure the magnetic core parameters of the pulse transformer, and can be used in enterprises for the screening of magnetic core products.The paper analyzes the status quo and development trend of dynamic magnetic measurement instrument at home and abroad, which describes the design method of intelligent testing system of pulse transformer core based on the basic principle of dynamic magnetic measurement. The system consists of AC programmable excitation power, data acquisition circuit, data transmission circuit and host computer software component. AC programmable excitation power consists of the adjustable signal source and the high-frequency power amplifier, whose function is to allow core saturated. Adjustable signal source adopts AD9851 DDS chip and AD8400 digital potentiometer and high-frequency power amplifier adopts high- frequency and middle-power pair tubes 2SA1930/2SC5171 and high- frequency and high-power pair tubes 2SA1943/2SC5200. Data acquisition circuit is composed of FPGA and TLC5540 high-speed A/D converter, whose achievement is to realize signal sampling and data storage of H Road and B Road. Data transmission circuit consists of FPGA and USB microprocessor, which transfers the collected data to PC-Buffer. Host computer software is programmed with LabVIEW, which realizes the process of the collected data and through the USB microprocessor outputting controlling signals to control the AC programmable excitation power.According to the requirement of usage frequency in enterprises, the settled frequency scope of system testing is between 10kHZ to 200kHZ, and the scope of outgoing magnetizing current is between 0.05A to 4A, which can measure the magnetic core paremeters in single turn, and also meet the requirement of general lighting devices of measuring by switching power supply magnetic core.; the system adopts digital integration to replace the traditional hardware integration, not only simplifies the circuit to avoid the phase-shift of hardware integration difficult to control, but also improves the testing accuracy and speed. The designed system can test maximum magnetic induction intensity B_m, maximum magnetic field strength H_m, remnant magnetization B_r, coercive force H_c, Amplitude Permeabilityμ_αand squareness ratio B_r/B_m, and be able to draw out the hysteresis loop on the PC.The paper gives the problems of testing process and their solutions. The system tests MnZn ferrite ring, and the test results compares with the testing data of Japanese Iwasaki Corporation SY8232B-H loop tester, whose result shows that the system achieves the desired goal.