A 40W Dual-Inductor Hybrid Converter with Flying-Capacitor-Tapped Auxiliary Stage for Fast Transient Response in 48V PoL Automotive Applications

Advancements in autonomous vehicles have led to a proliferation of onboard electronics, frequently making use of high-performance automotive-grade processors. To satisfy the resulting stringent operating requirements, the dc-dc Power Management Unit (PMU) of the processor must maintain strict voltage regulation, which is typically achieved with large and costly decoupling capacitors. This work proposes an auxiliary-assisted 4-to-1 Dual-Inductor-Hybrid (DIH) converter for fast transient response in 48V-1V applications. The auxiliary converter operates by tapping one of the flying capacitors of the DIH converter and regulates the output voltage using a capacitor-current-based Constant-On-Time control scheme. The 4-to-1 DIH converter acts as the main stage and delivers dc power from the 48V bus by regulating the auxiliary inductor current to avoid drawing dc power through the auxiliary stage. The auxiliary capacitance requirements are relaxed by leveraging the flying capacitor of the DIH converter as an energy reservoir. In simulation, the proposed system operates with a low auxiliary capacitance of 4.7 μF, which creates a 1V deviation on the auxiliary voltage during 20A load transients. A 40W experimental prototype demonstrates the feasibility of the proposed system, achieving a peak efficiency of 93.8%. The prototype regulates the output voltage of 1 V within ±60 mV with an output capacitor of only 650 μF while experiencing load transients up to 12.5 A.