Flyback converter with USB power delivery is widely used for fast-charging mobile devices. However, conventional solutions have issues such as lower efficiency, higher cost, a large number of external components, and lower loop gain bandwidth. In this article, a high-efficiency zero-voltage switching (ZVS) flyback converter with primary-and secondary-side control ICs is proposed to solve the aforementioned issues with high integration level. The proposed control replaces optocoupler to achieve ZVS and secondary-side-regulation (SSR) by a pulse transformer. The ICs further integrate the USB power delivery (PD) controller and the constant voltage (CV)/constant current (CC) loop compensation to reduce external components. The proposed control and small-signal model are illustrated and verified by the experiment. The control ICs were fabricated in a 180-nm BCD process. The implemented 20-V/3-A/60-W USB PD flyback converter achieved 93.5% maximum efficiency using Si power switches. The feasibility of the proposed converter is verified by a thorough test of programmable power supply (PPS) with various CC/CV levels and load/line transients. Index Terms-Converter, constant voltage (CV)/constant current (CC), fast-charging, flyback converter, pulse transformer, USB power delivery (PD), zero-voltage switching (ZVS). I. INTRODUCTION U SB power delivery (PD) supporting up to 100 W (20 V/5 A) has become a popular standard for mobile devices' fast-charging solution [1]-[3]. An adapter with the USB-PD specification has the advantage of supplying various devices with a single converter. For example, the converter with the input from the grid can provide a 5-V dc output voltage for cellphone load and a 19-V dc output voltage for laptop computer load. Thus, the carrying adaptors and corresponding electronic trash can be reduced. Moreover, the extended specification of USB PD includes a programmable power supply (PPS) which is suitable for fast-charging mobile devices.
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