Let's compare in detail the core differences between IGBT (Insulated Gate Bipolar Transistor) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor), two power semiconductor devices. They are all voltage controlled switching devices, but the differences in internal structure and working principle result in significantly different performance characteristics and application scenarios.
Summary of core differences:
Structural differences:
MOSFET: Essentially a unipolar device (conducting most charge carriers). The basic structure is gate, source, and drain. Current flows in the N-channel (or P-channel) between the source and drain, and the formation and disappearance of the channel are controlled by the gate voltage.
IGBT: Essentially, it is a bipolar device (majority carrier+minority carrier conducting together). It can be seen as adding a P+layer (collector) to the drain terminal of the MOSFET (for N-channel MOSFETs), thereby integrating a PNP bipolar junction transistor (BJT) internally. Therefore, IGBT has a gate, an emitter (corresponding to MOSFET source), and a collector.
Conduction mechanism and pressure drop:
MOSFET: When conducting, the current mainly flows from the source to the drain by the majority carriers (electrons in the N-channel). The on resistance (Rds (on)) is the key factor determining the on voltage drop (Vds (on)). In high voltage (>200V) applications, Rds (on) will significantly increase, leading to a sharp increase in conduction loss. This is the main bottleneck of MOSFETs in high voltage and high current applications.
IGBT: When conducting, the MOSFET part conducts first, providing base current to the internal PNP transistor to make it conductive. The conduction of PNP transistors introduces a conductivity modulation effect: the injected minority carriers (holes) significantly increase the carrier concentration in the drift region, thereby significantly reducing the resistance of the drift region. This enables IGBT to have much lower conduction voltage drop (Vce (sat)) than MOSFET under high voltage (above 600V) and high current, significantly reducing conduction loss.
Switching speed and loss:
MOSFET: Unipolar device, the switching process only involves the injection and extraction of majority carriers, and the switching speed is extremely fast (nanosecond level). The switching losses (turn-on loss Eon and turn off loss Eoff) are usually low, especially suitable for high-frequency applications (tens of kHz to MHz).
IGBT: Bipolar device, which involves the injection, storage, and recombination of minority carriers during the switching process. The switching speed is relatively slow (microsecond level), especially when there is a "tail current" phenomenon during turn off, which is caused by the recombination of stored minority carriers. This leads to higher switching losses (Eon, Eoff), limiting its operating frequency (usually below 100kHz, modern IGBTs can reach several tens of kHz).
Safe workspace:
MOSFET: It has a wide forward bias safe working area and no secondary breakdown problem (due to its unipolar characteristics). Its current handling capability is mainly limited by the on resistance and packaging thermal resistance.
IGBT: There is a risk of jamming effect. When the current flowing through the parasitic thyristor (composed of internal PNP and parasitic NPN transistors) is too high, it may trigger the thyristor to conduct and lock, causing the gate to lose control and the device to be damaged. Special attention should be paid to the driving circuit and load conditions during design to avoid jamming. Its safe working area is constrained by the locking effect and thermal limitations.
Temperature characteristics:
MOSFET: The on resistance Rds (on) has a positive temperature coefficient. The increase in temperature leads to an increase in Rds (on), which limits the further increase in current and is beneficial for current sharing when devices are connected in parallel.
IGBT: The conduction voltage drop Vce (sat) usually has a negative temperature coefficient (especially at low current densities). As the temperature increases, Vce (sat) slightly decreases. This means that in parallel applications, the current may concentrate towards devices with higher temperatures, requiring more careful thermal design and drive matching to ensure current sharing.
Voltage and current capability:
MOSFET: Excellent low voltage (<200V) performance, low on resistance, and fast switching speed. Although high-voltage (>600V) models exist, their on resistance significantly increases, resulting in high costs and low efficiency. The current capability is limited by Rds (on) and packaging.
IGBT: Optimized for high voltage (600V 6500V+) and high current applications. By utilizing the conductivity modulation effect, it is possible to achieve much lower conduction voltage drop than MOSFETs of the same level under high voltage, and has stronger current processing capability (up to several thousand amperes).
Comparison of application scenarios:
|Features | MOSFET | IGBT|
|Core advantages | Ultra high speed switch, low voltage and resistance, high frequency and low switching loss | High voltage and low conduction voltage drop, high current capability|
|Typical voltage |<200V (optimal), up to 1000V+|>600V (mainstream), up to 6500V+|
|Typical frequency | High frequency (tens of kHz MHz) | Medium low frequency (several kHz tens of kHz)|
|Loss focus | Low switching loss (dominant at high frequencies) | Low conduction loss (dominant at high voltages and currents)|
|Key limitations | Significant increase in conduction loss under high voltage | Slow switching speed, high switching loss, and risk of tripping|
|Typical applications | DCDC switching power supply (especially on the low voltage side)<br>Battery protection board<br>Low voltage motor drive (such as drones, power tools)<br>High frequency inverter (such as solar micro inverter)<br>Laptop/mobile phone charger | Industrial motor drive (frequency converter)<br>High power switching power supply (PFC, main transformer)<br>Uninterruptible power supply (UPS)<br>Induction heating<br>New energy generation inverter (photovoltaic, wind power)<br>Electric vehicle main drive inverter<br>Welding machine|
Summary:
MOSFET is the king of speed, with extremely high efficiency in applications with medium to low voltage and high switching frequency, such as switching power supplies and low-voltage motor drives. Its high-voltage model is difficult to match IGBT in terms of conduction loss.
IGBT is the king of high voltage overload, achieving higher overall efficiency in applications with relatively low requirements for high voltage, high current, and switching frequency (such as industrial motor drives, new energy inverters, and electric vehicle main drives) through ultra-low conduction voltage drop. The cost is slow switching speed and high switching losses.
In short: Do you need a high-frequency switch? Choose MOSFET (especially at medium and low voltage). Do you need to withstand high voltage and high current? Choose IGBT (especially when frequency requirements are not strict). The two are complementary in the field of power electronics, covering a wide range of application needs from low power to ultra-high power, from low voltage to ultra-high voltage, and from low frequency to high frequency. With the advancement of technology, such as SiC MOSFET and GaN HEMT, the boundary between the two in the high-frequency and high-voltage fields is gradually blurring and evolving.