A Bipolar Pulse Source Driven by Reverse- Series-Connected Linear Transformers With Its Multiscale Validation

In the application of pulsed electric fields for tumor ablation, bipolar pulses are preferred over unipolar pulses due to their more uniform therapeutic effects and reduced muscle contractions. This study designs a linear transformer driver (LTD) source based on a reverse-series topology structure for generating bipolar pulses. During the discharge phase, the LTD primary modules at all levels are grounded, offering the advantages of low isolation voltage levels and simple and reliable switch control, with theoretically unrestricted induction stacking modules. The bipolar pulse source is composed of structurally identical unipolar modules connected in reverse series in their secondary windings. However, this structure introduces the side effect of reverse inductive adder of induced electromotive forces. Therefore, this study proposes a bipolar complementary short-circuit circuit to eliminate the effects of reverse inductive adder. In addition, a primary charging power supply using a negative-polarity capacitor charging power supply (CCPS) was employed to enhance the stability of the triggering circuit. Finally, a magnetic core reset circuit was designed to achieve a wider output pulse duration and improve the utilization of the magnetic core. The multiscale experiment results demonstrate the robust and stable capability of the bipolar pulse source in the pulse discharge and tumor ablation, with the following parameters: voltage amplitude ranging from 0 to ±5000 V, current amplitude ranging from 0 to ±100 A, pulse duration ranging from 300 ns to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu $ </tex-math></inline-formula>s, and intervals between positive and negative pulses ranging from 0 to 1 ms. All pulse parameters can be flexibly adjusted using a custom-made computer system.