Research On Alternating Square Current Source With Wide Frequency And Constant Amplitude

The undeveloped status in electromagenetic transmitting technonlogy restricts the development of electromagenetic detecting device. Focused on the electromagenetic transmitting technonlogy and adopes it in targeting therapy. In the fields of geophysical exploration, it is necessary to create a pulse current source with changing edge of high linearity, high stability, short turn direction time and better positive and negative consistency. However, obtaining an ideal square current especially with high inductor load, small loop resistance and low input voltage is very difficult. This paper uses the idea of circuits in existence for reference, analyses pulse current circuits in theory, raises one kind of wide-frequency and constant amplitude current source circuit.1)The thesis analyzes the development,the problems and trends of the electromagenetic transmitting technonlogy,and factors which effects the quality of transmitting current, and cognizes that cutting short the rising time can minish the waveform aberration, improve the frequency width and work efficiency.It concludes that alternating square current with high current, short direction-changing delay, and linear changing-edge, good consistency between rising-edge and declining-edge is the trend of electromagenetic transmitting technonlogy.2)In order to solve the problems,such as the nonideality waveforms of load current's rising edge and changing of flat part with power supply,a rising-edge constant voltage clamping idear, a rising-edge enhancing constant current amplitude circuit and a constant current modulating strategy are proposed. The paper labors the working principle and design thought of control circuit, at last parameters are calculated in theory and simulation and experiment are done to confirm the theoretical analysis. The results proves that a high precision, high slope square source with changing-edge linear is designed. The current value is independent of voltage source, work frequency and load inductance.3)To control the power device accurately, a method using optical fiber link to transmit the drive signals is proposed, a isolated drive is developed. The experiment results proved that optical fiber isolation drive takes on the ability of high speed, short delay time, high isolation voltage, hige EMI immunity and credibility. Its drive delay is less than 90ns, which meets requirements.4)For the key equipment of targeting therapy, adoping the electromagenetic transmitting technonlogy into medical field, the idear about steep bipolar pulse magnetic field is proposed and a targeting oscillating magnetic field generator is developed. Comparative experiments proved that bipolar steep pulse magnetic field is more suitable for magnetic drug focus and controlled in targeting therapy than sinusoidal and unipolar. The circuit loss is small, the magnetic induction intensity reaches 1.3T and the effect of foucing and ossilating is well.