PFC Efficiency Improvement Using SiC Power Schottky Rectifiers
by Frederic Gautier and Cyril Borchard, STMicroelectronics, Tours, France, How2Power Today, Jan 26 2010
Focus:
Energy-saving regulations are forcing designers to consider the use of new power converter topologies and more-efficient electronic components such as high-voltage silicon-carbide (SiC) Schottky rectifiers. Use of SiC Schottky rectifiers in place of silicon rectifiers can improve the efficiency of the active power-factor correction (PFC) circuitry that's found in many SMPS designs. But to maximize the effectiveness of SiC Schottkys, power supply designers should understand the underlying technology and the key device parameters that must be considered when designing SiC Schottky diodes into an SMPS. Article discusses properties of SiC Schottkys and compares them with silicon diodes. Diode characteristics including turn off (influence of reverse recovery charge) and turn on. Article also addresses SiC Schottky power losses in PFC circuits, impact of switching speed on losses, EMI, and change in forward voltage as a function of junction temperature. Article presents an electrothermal Pspice model to simulate junction-temperature of the SiC Schottky in PFC applications during the transient phases (startup and line dropout); simulation examples are presented; basic design-rules are given for avoiding trouble with SiC boost diodes during the transient phases of operation.
What you’ll learn:
- How to account for unique forward-mode behavior of SiC Schottkys when designing PFC boost converters
- How to simulate junction-temperature rise of SiC Schottkys in PFC boost converters
- How to avoid pitfalls of SiC boost diodes during the transient phases of operation
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