Comprehensive comparative analysis of
MOS transistor and IGBT
Introduction
In the field of power electronics, MOSFETs and IGBTs (Insulated Gate Bipolar Transistors) are two core power devices widely used in switching power supplies, motor control, new energy inverters, and other fields. Although both belong to voltage controlled devices, there are significant differences in their structure, working principle, and applicable scenarios. This article will deeply compare the characteristics of the two from multiple dimensions, providing reference for engineering applications.
1、 The difference between structure and working principle
1. Structural composition
MOS transistor:
Composed of three terminals: source (S), drain (D), and gate (G), it adopts a metal oxide semiconductor (MOS) structure. Its core is to control the conductive channels in the semiconductor through the electric field effect, without a PN junction structure.
Classification: N-channel/P-channel, Enhanced/Depleted.
Features: Extremely high input impedance (up to 10 ^ 15 Ω), simple driving circuit.
IGBT：
The structure combines MOSFET and bipolar junction transistor (BJT), including emitter (E), collector (C), and gate (G) terminals. Internally, the input stage of MOSFET drives the output stage of BJT, forming a PN junction.
Structure: The input stage is MOSFET, and the output stage is PNP type BJT.
Features: Combining the high input impedance of MOSFET with the low conduction voltage drop of BJT.
2. Working principle
MOS transistor:
Control the conductive channel between the source and drain electrodes through gate voltage regulation. When the gate voltage exceeds the threshold, an inversion layer (N-channel or P-channel) is formed to achieve current conduction; When the voltage is below the threshold, the channel disappears and the current is cut off.
Control mode: pure voltage control, no current amplification effect.
Switching characteristics: The switching speed is extremely fast (up to MHz level), but the on resistance is relatively high.
IGBT：
The gate voltage first controls the partial conduction of MOSFET, and then drives BJT into saturation state. The conduction process is divided into two stages:
MOSFET conduction stage: The gate voltage causes the MOSFET to form a conductive channel, and the collector current begins to flow.
BJT amplification stage: The output current of MOSFET serves as the base current of BJT, driving it into deep saturation and achieving high current conduction.
Control method: Combining voltage control with current amplification.
Switching characteristics: The switching speed is slow (usually<20kHz), but the conduction voltage is reduced.
2、 Performance parameter comparison
1. Conductivity characteristics
MOS transistor:
Low current advantage: In low current (<10A) scenarios, the on resistance (RDS (on)) is low and the conduction loss is small.
High temperature characteristics: The conduction voltage increases significantly with temperature, while the performance decreases significantly at high temperatures.
Applicable scenarios: Low voltage and high frequency applications (such as mobile phone chargers, LED drivers).
IGBT：
Advantages of high current: In high current (>50A) scenarios, the collector emitter saturation voltage drop (VCE (sat)) is lower and the conduction loss is smaller.
High temperature stability: The conduction voltage changes less with temperature, and the performance is better at high temperatures.
Applicable scenarios: High voltage and high current applications (such as electric vehicle inverters, industrial motor control).
2. Switch characteristics
MOS transistor:
Switching speed: extremely fast (up to 1MHz), suitable for high-frequency switching power supplies (such as DC-DC converters).
Switching loss: low, but high static loss due to conduction resistance.
Driving requirements: The gate driving voltage is low (such as 17-18V required for 200V MOS transistor), and the driving circuit is simple.
IGBT：
Switching speed: slow (usually<20kHz), long turn off time (microsecond level).
Switching loss: relatively high, but can be optimized through soft switching technology.
Drive requirements: The gate drive voltage is fixed (15V ± 1.5V), and a complex drive circuit is required to prevent misguidance and short circuits.
3. Voltage and current capacity
MOS transistor:
Voltage endurance range: usually<600V, suitable for medium and low voltage scenarios.
Current capability: The current of discrete devices is generally less than 200A, but after modularization, it can be increased to several hundred amperes.
IGBT：
Voltage endurance range: up to 1400V or above, modular products have higher voltage endurance (such as 3300V).
Current capability: The current of discrete components can reach 400A, and after modularization, it can reach thousands of amperes (such as IGBT modules used in rail transit).
3、 Application scenario analysis
1. Typical applications of MOS transistors
Low voltage and high frequency scenarios:
Switching power supply (such as PC power supply, mobile phone fast charging).
High frequency inverters (such as wireless charging, PD fast charging).
Audio amplifier (low noise characteristic).
Consumer Electronics:
Lithium battery protection board, smart wearable device (SOT packaging with small volume).
Drone and balance car motor drive (fast response).
2. Typical applications of IGBT
High voltage and high-power scenarios:
Electric vehicle main drive inverter (circuit above 600V).
Industrial frequency converters and welding machines (capable of withstanding high current surges).
Smart grid, rail transit (high voltage resistance, large capacity).
In the field of new energy:
Solar inverter (DC-AC conversion).
Wind power converter (high voltage, high current adaptability).
4、 Balancing Cost and Efficiency
1. Cost comparison
MOS transistor:
Mature technology and low cost (especially for medium and low voltage products).
Under high-frequency applications, there is no need for complex heat dissipation design, and the system cost is low.
IGBT：
The manufacturing process is complex (requiring consideration of MOSFET and BJT characteristics) and the cost is high.
In high voltage and high current scenarios, modular products have outstanding cost-effectiveness.
2. Efficiency comparison
MOS transistor:
Higher efficiency in low voltage scenarios (lower conduction loss).
In high-frequency applications, the proportion of switch losses is small and the overall efficiency is excellent.
IGBT：
Higher efficiency in high-pressure scenarios (reduced conduction voltage).
In low-frequency applications, although the switching loss is high, the advantage of conduction loss is significant.
5、 Summary and selection suggestions
1. Summary of core differences
Characteristic MOSFET IGBT
Three terminal field-effect transistor structure, no PN junction composite structure, containing PN junction
Control method: pure voltage control, voltage control+current amplification
Switching speed is extremely fast (MHz level) and slow (<20kHz)
Voltage resistance<600V>1400V
Current capability discrete devices<200A discrete devices>400A
Typical applications include low voltage and high frequency, consumer electronics high voltage and high power, industrial and new energy
2. Selection suggestions
Select MOS transistor:
Scenarios with working voltage<600V and switching frequency>100kHz (such as switching power supplies and high-frequency inverters).
Low voltage applications that are cost sensitive and do not require high efficiency, such as LED drivers.
Select IGBT:
Scenarios with working voltage>1000V and current>50A (such as electric vehicles and industrial motor control).
High voltage and high-power systems that require extremely high efficiency and reliability, such as rail transit and smart grids.
6、 Future Development Trends
MOS transistor:
The application of wide bandgap semiconductors such as GaN and SiC will further enhance their high-frequency and high-voltage performance.
Improvements in packaging technology, such as Cu Clip process, reduce on resistance and increase power density.
IGBT：
The seventh generation IGBT technology (such as FS-IGBT) reduces the conduction voltage drop by optimizing the field stop layer.
Modularization and integration (such as IPM intelligent power module) simplify system design and improve reliability.
Conclusion
As the two pillar devices in the field of power electronics, MOS and IGBT differ fundamentally in their structural design and working principles. MOS transistors dominate the consumer electronics market with their advantages in high frequency and low voltage, while IGBT has become the core of the industrial and new energy fields with its high voltage and high current capabilities. In the future, with the breakthrough of wide bandgap semiconductors, both will achieve further optimization of performance and cost in a wider range of scenarios.
