Language 
Switching Losses of SiC: MOSFET Switching Loss Calculation and Performance of SiC Modules
In modern power electronics, switching loss is one of the most critical factors affecting system efficiency. With rising switching frequencies
in electric vehicle inverters, industrial drives and renewable energy systems, engineers must carefully evaluate the loss and switching
behaviour of MOSFETs.
Since the adoption of silicon carbide technology, SiC MOSFETs deliver significantly lower switching losses compared with conventional
silicon devices. Nevertheless, accurate calculation of MOSFET switching losses based on datasheets remains essential for proper thermal
design and device selection.
This article covers:
How to perform MOSFET switching loss calculations
Methods to estimate MOSFET power losses in practical systems
How SiC technology reduces switching losses
How high-performance modules such as Ruilin Semiconductor RL800N1200A (2mΩ SiC) improve inverter efficiency
1. What are SiC Switching Losses?
Switching losses occur during the transition between the ON-state and OFF-state of power semiconductor devices.
When a MOSFET switches, voltage and current exist simultaneously for a short period. This overlap causes energy dissipation.
The switching loss can be expressed by the formula:
Psw = 1/2 × Vds × Id × (tr + tf) × fsw
Where:
Vds = drain-source voltage
Id = drain current
tr = rise time
tf = fall time
fsw = switching frequency
This formula forms the fundamental basis for MOSFET power loss calculations used by engineers in power stage design.
2. MOSFET Power Loss Calculation
Total losses of a MOSFET consist of two main components:Conduction Losses + Switching Losses
2.1 Conduction Losses
Pcond = I² × Rds(on)
Conduction losses depend on:
Operating current of the device
On-state resistance Rds(on)
2.2 Switching Losses
Switching losses increase with:
Switching frequency
Voltage level
Switching speed
Therefore, both conduction losses and switching losses must be considered in MOSFET power loss calculations. Thanks to intrinsic
material properties, SiC MOSFETs achieve reductions in both types of losses.
3. Calculating MOSFET Switching Losses from Datasheets
Engineers commonly calculate MOSFET switching losses using parameters provided in datasheets.
Datasheets typically specify:
Turn-on energy Eon
Turn-off energy Eoff
Total switching loss can be estimated as:
Psw = (Eon + Eoff) × fsw
This method is widely adopted when evaluating devices from manufacturers such as Infineon. For instance, many Infineon application
notes on MOSFET switching loss calculations recommend using switching energy values under specified test conditions.
However, engineers must also take the following factors into account, as they can substantially affect actual switching losses:
Practical gate resistance
System parasitic inductance
Operating temperature
4. Understanding Switching Losses in SiC MOSFETs: Towards Near-Lossless Switching
The development of SiC MOSFET technology aims to reduce switching losses to achieve near-lossless switching performance.
Compared with conventional silicon IGBTs, SiC MOSFETs offer:
✅ Faster switching speed
✅ Lower output capacitance
✅ Negligible reverse recovery losses of diodes
Thanks to these characteristics, switching losses of SiC devices can be far lower than those of traditional silicon devices. In
high-frequency applications such as electric vehicle inverters, reduced switching losses can improve system efficiency by several
percentage points. Additional benefits include:
Smaller heat sinks
Higher power density
Support for higher switching frequencies
5. Case Study: Switching Loss Analysis of Ruilin RL800N1200A SiC Module
To illustrate the impact of SiC technology, we analyse a high-current SiC power module RL800N1200A.
Typical characteristics:
Current rating: 800A
Voltage rating: 1200V
Ultra-low Rds(on): 2mΩ
Optimised switching performance
Ultra-low on-resistance greatly reduces conduction losses:
Pcond = I² × Rds(on)
For example, under the same current conditions, reducing resistance from 4mΩ to 2mΩ cuts conduction losses by
approximately 50%.Furthermore, optimised gate structure and low parasitic inductance enhance switching performance
and lower SiC switching losses.
Such high-power SiC modules are ideal for applications including:
Electric vehicle traction inverters
Industrial power converters
Renewable energy systems
6. Design Considerations to Reduce MOSFET Losses
Engineers designing high-efficiency power converters can adopt multiple strategies to minimise MOSFET losses:
Select devices with low Rds(on) to suppress conduction losses
Optimise gate driver design; select appropriate gate resistance to balance losses and EMI
Reduce parasitic inductance via optimised module layout and PCB design to mitigate voltage overshoot and switching energy
Adopt advanced high-performance SiC modules for superior switching and thermal performance
7. Conclusion
Accurate MOSFET switching loss calculation is critical for developing high-efficiency power electronic systems.
By mastering:
MOSFET power loss calculation principles
Switching loss estimation methods based on datasheets
The loss advantages of SiC MOSFET technology
Engineers can significantly improve system efficiency and reliability.
Modern SiC modules such as Ruilin RL800N1200A (2mΩ) demonstrate how advanced semiconductor technology reduces switching
losses and enables high-power, high-efficiency inverter systems.
As power electronics technology continues evolving, optimisation of SiC switching losses will play a vital role in next-generation
systems for electric vehicles, renewable energy and industrial applications.
Frequently Asked Questions(FAQs)
Q1: How to calculate MOSFET switching losses?
A:Switching losses can be calculated using the turn-on and turn-off energy values Eon and Eoff provided in datasheets:
Psw = (Eon + Eoff) × fsw Total switching power loss is linearly proportional to the switching frequency.
Q2: Why are switching losses lower for SiC MOSFETs?
A:Compared with silicon devices, SiC MOSFETs feature lower parasitic capacitance and faster switching transitions, which
greatly reduce switching overlap losses.
Q3: What causes MOSFET switching losses?
A:Switching losses arise during transitions between ON and OFF states, when voltage and current overlap for a short time.
Q4: How can MOSFET power losses be reduced?
MOSFET power losses can be reduced through the following approaches:
Select devices with low Rds(on)
Optimise gate driver circuits
Minimise parasitic inductance of the power loop
Deploy high-performance SiC modules
About RichPower Technology
RichPower Technology We are a professional storage and semiconductor solution
provider, focusing on providing high-quality products such as LPDDR, eMMC, eMCP, and SiC power modules,
and providing comprehensive technical support and reliable solutions for industrial, automotive, and IoT systems.
