High-frequency AC field (100-300 kHz), which could generate tumor treating fields (TTFields) has been FDA-approved for glioblastoma multiforme (GBM) treatment. How to design a high-frequency AC field with low input battery (3.7 V) power is important for outdoor stimulation with a long treatment time.This study utilizes an LCLC step-up resonant circuit integrated with a linear isolated transformer (LCLLC) to generate a 200 kHz AC field using low DC input. Theoretical circuit analysis investigated the excitation inductance’s impact on voltage gain under capacitive bio-loads. An experimental prototype was developed based on selected parameters, generating 200 kHz AC waveforms (66 V output, voltage gain: 17.8) with 5.1 W input power from a 3.7 V battery, sustaining 8.7-hour operation. Coupled insulated electrodes demonstrated high-efficacy AC field delivery. CCK-8 assays confirmed that generator stimulation significantly inhibited U251 glioblastoma cell proliferation. The theoretical analysis showed that the adjustment of excitation inductance of linear isolated transformer in LCLLC circuit could benefit to achieve a high voltage gain with low input power. This work developed a low-power 200 kHz AC field generator powered by 3.7 V DC batteries, achieving high voltage gain (17.8) and significant cell proliferation inhibition, enabling portable tumor-treating field applications.