Using Forced-Frequency Resonant Zero-Voltage Switching In USB PD Adapters
by Jimmy Wang, Infineon Technologies, Shenzhen, China, How2Power Today, Sep 15 2020
Focus:
Capable of supplying anything from 5 to 20 V and supporting power levels up to 100 W,
USB-C cables, which implement the USB Power Delivery (PD) specification, may be the
only thing we need to power our laptops, as well as to connect a wide range of
peripherals to them. USB PD also enables faster charging of smartphone batteries. This
article discusses some of the challenges in designing USB PD-based power adapters and
how they can be addressed using a switching technique known as forced-frequency
resonant zero voltage switching (ZVS) in a DCM-operated flyback topology. The forced-
frequency resonant form of ZVS supports operation at frequencies above 100 kHz,
enabling use of an embedded planar transformer. A reference design based on a
controller developed to implement this technique, the XDPS21071, is presented, its
principles of operation and other circuit details are explained, and a prototype and
measurements of its efficiency are presented and discussed.
What you’ll learn:
- How to understand the drawbacks of quasi-resonant flybacks operating in discontinuous conduction mode
- How to understand the principles of operation and benefits of forced-frequency resonant zero voltage switching (ZVS) in a DCM-operated flyback converter
- How to improve the performance of USB PD-based power adapters using forced-frequency resonant zero voltage switching
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