Multi-Winding Configuration Optimization of Multi-Output Planar Transformers in GaN Active Forward Converters for Satellite Applications

It is a serious challenge to find the optimal winding configuration that realizes minimum leakage inductance of multi-output multi-winding planar transformers due to the complex coupling relationship. The proposed idea is to build the mathematical model of leakage magnetic field energy and screen out all possible winding configurations to solve the minimum value with MATLAB programming. Then, only limited potential winding configurations need to be three-dimensionally simulated in Maxwell. By analyzing the inductance matrix, the leakage inductance of multi-winding planar transformers is solved. A full gallium nitride (GaN) active clamp forward converter with self-driven synchronous rectifiers (SRs) is presented with complete mode analysis. It is noted that the proposed active clamp technology uses the auxiliary winding with the nonfloating GaN switch compared to the conventional high-side clamping circuit, which is important for the satellite applications. The GaN drive chips for high reliable gate voltage are combined with self-driving. Considering the leakage inductance in each winding and junction capacitance of the GaN high electron mobility transistors, the oscillation frequency and amplitude over the switches are modeled quantitatively, which is important to minimize powertrain loop at MHz. The explanation of the root cause of the voltage spike in the converter is also presented. A prototype with 1 MHz, 100 V input, 5 V/6 A and ±12 V/0.83 A outputs was built to verify the proposed techniques.