An Inductor-First Tri-Path Hybrid Buck Converter With Reduced Inductor Current Suitable for USB Power Delivery Adapter

This paper presents an inductor-first tri-path (IFTP) buck converter suitable for USB power delivery adapter to charge 1-2 cell battery. The proposed topology adopts the inductor-first strategy and the tri-path strategy of one inductor path and two capacitor paths to extend the output voltage conversion range, realize the continuous input current, eliminate the input EMI noise, and reduce the inductor current. In addition, a phase-interleaved symmetric inductor-first tri-path (PIS-IFTP) buck converter is proposed to alleviate the inrush current in the flying capacitor under extreme duty cycle of IFTP converter, while further reducing inductor current ripple. Two experimental prototypes for 9 V input to 3-8.4 V ouput have been developed, demonstrating excellent ability of IFTP and PIS-IFTP topologies to reduce inductor current and achieve continuous input current over the whole duty cycle and load range. The experimental results validate that the prototypes provide a wide voltage conversion range of 1/3-1 and a maximum output current of 1.8 A. The peak efficiency of IFTP is 93% at $V_{OUT} \,\, =6.6$ V, while the peak efficiency of PIS-IFTP is 94.5% at $V_{OUT} \,\, =3.3$ V.