LTspice-Based Analysis and RCD Clamp Implementation for Performance Improvement in a Planar Transformer Flyback Converter

High-frequency flyback converters are attractive for compact isolated power supplies, yet transformer parasitics can introduce severe voltage stress on the primary switch. In planar transformers, tight geometric constraints improve repeatability and thermal behavior, but leakage inductance remains a dominant cause of drain-voltage overshoot during turn-off. This paper presents an LTspice-based study of a planar-transformer flyback converter and evaluates a series RCD clamp as a practical improvement to limit drain stress. The transformer is modeled using coupled inductors to represent magnetizing and leakage effects, and key waveforms are examined, including gate drive, drain voltage, primary current, and output voltage. Simulation results show that the RCD clamp reduces the peak drain-voltage overshoot (from the kV range down to approximately the 1.0–1.1 kV range in this design) while maintaining stable output regulation around 5 V. The presented workflow provides a rapid, reproducible approach for assessing stress-mitigation circuits in high-frequency planar flyback converters.