Study On Trapezoidal Pulse Current Source

The electromagnetic detection instrument is composed generally of the exciting field source, the receive instrument and so on.The performance and quality of exciting field source affect directly the geologic body induction signal quality. The ideal exciting field source is the bipolarity rectangular square-wave, but the ideal bipolarity rectangular square-wave is extremely difficult to achieve, in particular to launche the bipolarity rectangular square-wave in the big perceptual load. At present, the bipolarity square-wave front rises as the index rule, the back edge is the slanting step wave, namely the non-instantaneous shutdown, the actual wave is approximate to the trapezoidal wave.This paper analyzes the characteristics of conventional electromagnetic transmission circuit, designs the trapezoidal pulse current source circuit, carries out simulation analysis and experiment. The things that has been done are mainly in the following areas:①The paper has analyzed the electromagnetic emission technology, the existence question and the trend of development in the domestic and foreign at present, has analyzed the factor that influents the quality of emission current,has used the constant current and the front constant pressure clamp thought, has realized electric current front fast linearity rise;As constant high-speed turn-off technologies, controll the front clamping voltage to change the front steepness; Has made the rise edge and the drop edge adjustable, adjust the rise edge and the drop edge to make the rise edge and the drop edge symmetrical.②Propose the phase shifting control and the driving signal synthesis strategy. The main circuit phase shifting control circuit and the driving signal synthesis electric circuit complement each other skillfully, in this situation that need not increase the electronic switching in the main circuit,modulates under-bridge arm switch driving signal, address constant current electric current after flow and constant flow question, and the question of output load electric current unstable effectively.③Launch a cutting-edge linear lifting circuit, constant voltage clamp circuit, output current control circuit and system software design, implement single,bipolar emission of the trapezoidal pulse current source.④Design the IGBT driver circuit of the main circuit. At the same time, increase the driving signal synthesis electric circuit. ⑤Design a trapezoidal pulse current source control system,the system monitoring program, LCD display program, data processing, alarm procedures, etc. are studied.⑥In order to solve the question that the harmonic wave when under PWM control is too big, and the question that the efficiency is low in the underloading time, the paper has studied the high efficiency pulse cross cycle tone circuit in the underloading situation, has designed a section pulse cross cycle modulation pressure-rise DC/DC converter. And applicate it in trapezoidal pulse current supply rise along constant pressure clamp and drop along in constant pressure clamp energy outer loop sucessfully.The linear increase, linear decline, short rise delay, fall short delay, before and after along the symmetry, positive and negative symmetry, high stability of the trapezoidal pulse current launch are achieved in a large inductive load, which is of great significance to promote the development of electromagnetic detection technology.