Enhanced dynamic regulation in Buck Converters: integrating input-voltage feedforward with voltage-mode feedback

DC-DC buck converters in automotive and aerospace applications are often required to handle large disturbances in their input supply and abrupt variations in their loads. This paper proposes a systematic method to combine input-voltage feedforward (IVFF) and voltage-mode feedback (VFB) controllers, aiming to enhance the closed-loop performance of these DC-DC converters. This method relies on the stability boundary locus approach to help select the proper control parameters that achieve strong dynamic stability across the full operating range regardless of practical implementation challenges. Also, an optimization approach is employed to minimize the passive components’ area within the compensator, achieving a 79% reduction in integration size compared to conventional designs. The controller was fabricated in a 0.35- μm CMOS technology, occupying a core area of 0.438 mm2. The prototype chip was experimentally tested to regulate a buck converter that leverages an e-GaN half-bridge while operating at 1 MHz. Measurement results show a remarkable closed-loop performance against line and load variations, reaching up to ±80 V/ms and ±535 mA per 150 μs , respectively. The output remains stable, showcasing very small (<100 mV) to non-existent spikes and fast recovery periods. In addition, the system shows fast startup times ( <100μs ) with small overshoots (<1%) observed at the output. The system power efficiency, tested across various loads, peaks at 95.14% while operating at 695 mA load current. It is shown that the combined-controller approach entirely eliminates transient voltage spikes, offering up to 100% improvement in dynamic performance over a standalone VFB controller.

Mots clés

buck converter; controller design; DC-DC converter; dynamic regulation; feedforward; GaN half-bridge; high-voltage circuits; stability boundary locus; voltage-mode feedback