Study On Transient Electromagnetic Unipolar Trapezoidal Pulse Current Source

In the transient electromagnetic detection field, emission current waveform qualitywill directly affect the sensor signal detection of geological bodies. Classic transientelectromagnetic method theory is based on the unipolar step-wave current sourceincentives, but the conventional transient electromagnetic method use of a bipolarrectangular pulse,and it is very difficult to achieve the desired bipolar pulse in the largeinductive load. The rising edge of the emission current waveform is similar to the indexrose, and the falling edge is inclined step wave,and the actual waveform isapproximately trapezoidal wave. This paper analyzes the idea of the current transmittercircuit topology, and summarizes the strengths and weaknesses of their existence,andproposed a unipolar trapezoidal pulse current source,and carry out simulation analysisand experimental studies. Primarily done the following aspects:①The paper has a comprehensive analysis of the electromagnetic emissiontechnology, the existence question and the trend of development in the domestic andforeign at present,and analyze the key technical problems of the transientelectromagnetic field source.And the paper proposed the rising edge fast linearly rising,consistentence with linear rising and falling edges, and stable load current of unipolarpulse current can be widely used in the field of electromagnetic detection.②This paper proposed the capacitance constant voltage clamp technique forhigh-power electromagnetic transmitter, and usd a constant current source strategies andcutting-edge clamping strategy,achieved rapid linear increasing of emission current.Controlling the clamp voltage can alter the linearity of the cutting-edge.This paperanalyze the advantages and disadvantages of the circuit,and proposed constant capacitorvoltage clamp circuit based on the the TVS,improved the stability of the clampingvoltage and the linearity of rising and falling edges.③For low-power applications, this paper proposed TVS constant voltage clamptechnique. Segmented clamping strategy can guarantee a linear fastly change ofemission current of rising and falling edges, and also ensure the stability of the emissioncurrent.This paper proposed low-voltage clamping voltage value determining method,itcan reduce the switching noise and the current shock. Consistency analysis of the risingand falling slope, laid the foundation for unipolar trapezoidal pulse current applications. ④To carry out a constant current source control circuit, the load current controlcircuit, adjustable clamping voltage source circuit design,and design the MOSFETdriver circuit of the main circuit. At the same time, increase the driving signal synthesiselectric circuit,it achieve the emission of unipolar trapezoidal pulse circuit.In the large inductive loads, it’s of great significance for the development ofelectromagnetic detection technology to achieve the quickly linear changed rising andfalling edge, rising and falling edges of symmetry,high stability current unipolartrapezoidal pulse current source.