Table of Contents
1. The Impact of Switching Frequency on SMPS Power Loss
2. Experimental Verification: SiC Schottky Diode Performance in PFC Boost Converters
3. Comparative Performance Advantages of SiC Diodes at Different Frequencies
4. System-Level Benefits of SiC Schottky Diodes
5. SHYSEMI SiC Technology in Practice
Keywords: SiC Schottky Diode, SMPS, Reverse Recovery, MOSFET, PFC, EMI Filter, Parasitic Capacitance, Power Topology
Introduction
Switch-mode power supplies (SMPS) play a crucial role in modern electronics, from consumer devices to industrial systems. In applications such as portable computers, the power supply can account for over 10% of total system weight.
To achieve higher power density and conversion efficiency, designers typically optimize along three main directions:
1.Reducing total power loss, thereby minimizing the size of heat sinks or cooling fans.
2.Increasing switching frequency, which enables smaller passive components and EMI filters.
3.Employing SiC Schottky diodes to achieve lower power dissipation, higher switching frequency, and overall system miniaturization.
1. The Impact of Switching Frequency on SMPS Power Loss
While soft-switching technologies can mitigate switching losses and support higher operating frequencies, they typically require additional passive components, which increases circuit complexity and hinders compact design.
By contrast, hard-switching topologies are structurally simpler and more compact, yet their switching losses inherently limit achievable frequency. In such topologies, the use of unipolar devices — such as MOSFETs and Schottky diodes, which exhibit no minority-carrier storage effect — is highly advantageous.
These devices are influenced only by parasitic capacitances, resulting in shorter switching times and reduced current–voltage overlap during transitions. This directly translates to lower switching losses and improved system efficiency.
Traditional silicon Schottky diodes offer benefits such as low forward voltage drop and minimal reverse recovery, but their breakdown voltage is limited, making them suitable only for low-voltage applications.
In contrast, SiC Schottky diodes, based on wide-bandgap material properties, exhibit a breakdown electric field 10× higher than silicon and a thermal conductivity comparable to copper. These features allow blocking voltages up to 3,500 V, breaking through the long-standing material limitations of silicon devices.
Consequently, hard-switching topologies employing power MOSFETs in combination with SiC Schottky diodes offer a practical pathway to high-frequency, high-efficiency power conversion.
2. Experimental Verification: SiC Schottky Diode Performance in a PFC Boost Converter
A performance evaluation was conducted by Infineon Technologies on a 400 W continuous conduction mode (CCM) PFC boost converter employing a hard-switching topology.
Key Parameters:
Input Voltage Range:85–265 V
Output Power: 400 W
Output Voltage: 385 V
Power Factor Compliance: EN61000-3-2
Conducted Emission Compliance: EN55011 Class B
Main Devices: SiC Schottky Diode (SDP04S60) and Power MOSFET (SPP20N60C3)
Efficiency Results:
At 140 kHz, efficiency reached 93%, with total power loss of 28 W.
At 500 kHz, efficiency decreased slightly to 91.5%, with total power loss of 34 W.
Observations:
EMI filters, input rectifiers, and shunt resistors exhibited negligible change in power loss, meaning their physical size can remain unchanged.
Winding losses decreased with higher frequency, allowing the PFC choke to be reduced in size.
The bulk capacitor maintained its size due to hold-up time requirements, though it introduced increased power dissipation.
Switching losses of power semiconductors rose significantly, necessitating enhanced thermal management (e.g., larger heat sinks).
3. Comparative Performance Advantages of SiC Diodes at Different Frequencies
At 140 kHz, replacing a standard ultrafast silicon diode with a SiC Schottky diode in a 400 W converter reduced total power loss by 8.7 W and improved efficiency by approximately 2%.
Replacing a 70 kHz ultrafast diode with a 140 kHz SiC Schottky diode reduced total loss by 4 W, achieving >1% efficiency gain.
At 350 kHz, substituting a 70 kHz ultrafast diode with a SiC Schottky diode of equivalent thermal dissipation capability allowed a 65% reduction in PFC choke volume while maintaining equal total power loss and thermal performance.
4.System-Level Benefits of SiC Schottky Diodes
The advantages of SiC Schottky diodes extend far beyond individual device performance. They are fundamentally reshaping power system design by enabling:
4.1 High-Frequency System Architectures
SiC technology eliminates the frequency ceiling of traditional hard-switching circuits, allowing significant reductions in the size and weight of passive components while maintaining superior efficiency.
4.2 Ultra-High Power Density
By combining low switching loss with high-frequency operation, designers can employ smaller magnetic cores and simplified thermal solutions, paving the way for smaller, lighter, and more compact power supplies.
4.3 Extended High-Temperature and High-Voltage Capabilities
Exceptional thermal stability and high breakdown strength make SiC diodes ideal for server power supplies, on-board chargers (OBCs) in electric vehicles, photovoltaic inverters, and industrial motor drives, where high reliability and efficiency are paramount.
5.SHYSEMI SiC Technology in Practice
At SHYSEMI, our SiC Schottky diodes are among our most competitive product lines.
Our SiC MOSFET modules for High-Voltage Power Distribution (HPD) have already entered mass production at the Beijing Automotive Research Institute, demonstrating tangible benefits in real-world applications:
5–8 % improvement in inverter efficiency,
Higher power density,
Superior thermal stability,
Faster switching speed,
Simplified circuit design.
6.Conclusion
In summary, SiC Schottky diodes do more than enhance performance — they redefine the operational boundaries of boost converters.
Through intrinsic material and structural advantages, SiC technology enables the next generation of high-frequency, high-efficiency, and high-density power systems.
Choosing SiC Schottky diodes is not merely an upgrade — it is a strategic step toward the future of advanced power electronics. For further information or technical collaboration, please contact SHYSEMI.