Two-Switch Flybacks Outperform LLC Resonant Converters On Most Parameters
by Jiri Jirutka, STMicroelectronics, Prague, Czech Republic, How2Power Today, Jan 16 2019
Focus:
This article demonstrates how new QR resonant PWM controllers and SiC MOSFET-
compatible gate drivers are making the two-switch flyback converter a lower cost,
higher-performance alternative to the LLC resonant converter, especially in cases with
high-voltage input. In particular, the aim was to reach the possibility of using
STMicroelectronics’ QR PWM controllers for a high efficiency, high power factor LED
driver at output power up to 150 W or a high-voltage input, high efficiency power
supply with output power up to 300 W at parameters comparable or better than an LLC
resonant converter. Four options were developed and tested, two based on the HVLED001
HPF QR PWM controller and two on the STCH02/03 low standby QR PWM controller, with
usage of the L6385E standard HV MOSFET driver and with an innovative ac-coupled
transformer-based MOSFET driver, finally optimized and tested for use with SiC
MOSFETs. This transformer gate driver version is also applicable for high input
voltage above 1 kV.
What you’ll learn:
- How to understand the benefits of a QR PWM controller and a transformer-based gate driver in two-switch flybacks
- How to understand the advantages of two-switch flybacks versus LLC resonant converters
- How to extend use of dual-switch flybacks to applications with high-voltage input and simplify driving of SiC MOSFETs
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