A Multipulsed Power Source With Rectangularity Improvement for Magnetic Resonance Sounding

The rectangular pulsed power source is the key component of the pulse magnetic resonance sounding system, which requires high amplitude, short trailing time, and low amplitude decrease. Switching mode topologies, especially full-bridge topologies, are widely used to generate pulsed current. However, due to the complex pulse shape, the supply voltage drop in the traditional scheme leads to a sharp decrease in current amplitude and severe residual ringing. In this article, a phase-shifted full-bridge control model is designed based on the single-period energy calculation method, which can effectively maintain the stability of pulse amplitude when input voltage drops. Furthermore, a load-damping coefficient adjustment network based on short-circuit resistors is also applied for the fast turn-OFF. As a result, the control strategy for generating multipulse with rectangularity improvement is proposed. Experiment results show that the peak value of the rectangular current pulse is 236.5 A, the trailing time of residual current is about 0.4 ms, and the current amplitude decrease is only about 2% for a single pulse. The waveform quality is significantly improved, which supports the detection of deep groundwater and multiple parameters in MRS systems.