This paper presents the design of a 300-Watt isolated power supply for MOS gate driver circuit in medium and high voltage applications. The key feature of the developed power supply is having a very low circuit input-to-output parasitic capacitance, thus maximizing its noise immunity. This makes it suitable for modular stacking applications. The converter is a voltage-controlled current source, utilizing a transformer that has an extremely low inter-winding parasitic capacitance. The experiments show that an overall circuit input-to-output parasitic capacitance of 10 pF can be achieved. Design analysis and experimental results are provided to prove the feasibility of the converter.