Design and Implementation of a 1 MHz GaN-Based Quadratic Boost Converter with Hybrid Peak Current Mode Control

This paper presents the design, modeling, and hardware implementation of a 1 MHz Gallium Nitride (GaN) quadratic boost converter. Developed as a versatile experimental shield for an STM32 microcontroller development board, the proposed hardware enables direct measurement of all state variables to facilitate the experimental evaluation of advanced control algorithms. Based on a comprehensively derived state-space model, discrete-time Voltage Mode Control (VMC) is initially analyzed, highlighting the difficulties arising from the nature of the cascaded system. During large-signal operation at 1 MHz, this simple control strategy is highly vulnerable to dangerous current surges and oscillatory transients. To mitigate these instabilities, a hybrid Peak Current Mode Control (PCMC) strategy is proposed and implemented. An inner high-speed analog loop provides cycle-by-cycle current limiting, operating the power stage as a voltage-controlled current source to provide an input current limit as protection, even during inter-sample periods, where a slower digital controller remains “blind”. The shield architecture is especially useful here, since it allows the usage of built-in high-speed comparators of the microcontroller. Furthermore, this study investigates the complications arising from executing the outer digital control loop at sampling frequencies (100 kHz and 10 kHz) substantially lower than the switching frequency. Non-linear simulations reveal that at lower sampling rates, the control effort becomes too aggressive, causing the output to oscillate around a setpoint rather than stabilize. Applying a digital filter—specifically, Exponential Moving Averaging (EMA) to the controller output—is implemented to stabilize the reference signal. Both non-linear Simulink simulations and hardware experiments validate the proposed filtered PCMC architecture.