Abstract
This article presents a fully integrated, self-packaged flyback dc-dc converter designed for low-power applications, utilizing a quasiplanar multilayer printed-circuit board (PCB) platform. The innovative design incorporates a custom-designed, high-density toroidal transformer wrapped in dielectric boards and an internally developed GaN E-mode high electron mobility transistor (HEMT) power transistor, along with associated drivers and passive devices, to enhance conversion efficiency and reduce form factor. The operational principles and design methodologies of the converter are detailed, highlighting its distinctive quasiplanar structure transformer with a fully embedded magnetic core. All off-the-shelf devices are integrated within the metallic layers and air cavities inside the PCB frame. The prototype, designed for 24 V-to-16 V conversion at 0.2 MHz with a power output of 3.2 W, achieves a peak efficiency of 87.2%. It maintains an efficiency above 83.5% for output currents ranging from 0.084 to 0.2 A and features a compact form factor of 95 × 65 mm 2 . Thermography validation confirms that the surface temperature of the device layer remains below 44.1°C during operation.