Who should use IGBT and MOSFET? Did you choose the right one?

[Guide]semiconductor power devices mainly include power diodes, power transistors, thyristors, MOSFETs, IGBTs, etc. Among them, MOSFET and IGBT are voltage-controlled switching devices, which have the advantages of fast switching speed, easy drive, and low loss. The full name of IGBT is an insulated gate power tube. It is a composite full-controlled voltage-driven semiconductor power device composed of a bipolar transistor (BJT) and a MOSFET. It has both the high input impedance of MOSFET and the low conduction voltage drop of BJT. Aspects of advantages. With the rise of new energy vehicles, smart home appliances, 5G, rail transit and other industries, MOSFET and IGBT have also ushered in the spring of development.

However, in practical applications, engineers will encounter the same confusion: the selection of devices is really a headache. In this regard, the editor feels the same. Today, let’s take a look at the similarities and differences between MOSFET and IGBT, and which parameters should be focused on when selecting models.

Similarities and differences between MOSFET and IGBT

Both MOSFET and IGBT are solid-state semiconductor devices integrated on a single piece of silicon, and both belong to voltage control devices. In addition, IGBT and MOSFET have insulation between the gate and other terminals, and both devices have high input impedance. In application, both IGBT and MOSFET can be used as static Electronic switches.

Although there are many points in common, there are still many differences between IGBT and MOSFET in terms of performance parameters and applications.

In structure, MOSFET and IGBT look very similar, but they are different. IGBT consists of emitter, collector and gate terminals, while MOSFET consists of source, drain and gate terminals. There is a PN junction in the IGBT structure, and the MOSFET does not have any PN junction.

In terms of characteristic parameters, the main differences between MOSFET and IGBT are reflected in the following 9 aspects:

● In the low current area, the turn-on voltage of the MOSFET is lower than that of the IGBT, which is also its advantage. However, the forward voltage characteristic of IGBT is better than that of MOSFET in the high current region. In addition, because the forward characteristic of MOSFET has a strong positive dependence on temperature, the high temperature characteristic of IGBT is better, and the turn-on voltage is lower than that of MOSFET.

● IGBT is suitable for medium to very high current conduction and control, while MOSFET is suitable for low to medium current conduction and control.

● IGBT is not suitable for high frequency applications, it can run well at a frequency of thousand Hz. MOSFET is particularly suitable for very high frequency applications, and it can operate well at megaHz frequencies.

● The switching speed of IGBT is relatively low, while the switching speed of MOSFET is very high.

● IGBT can withstand very high voltage and high power, MOSFET is only suitable for low to medium voltage applications.

● IGBT has a longer turn-off time, while MOSFET has a shorter turn-off time.

● IGBT can handle any transient voltage and current, but when a transient voltage occurs, the operation of the MOSFET will be disturbed.

● MOSFET devices are low-cost and cheap, while IGBTs are still relatively high-cost devices.

● IGBT is suitable for high-power AC applications, and MOSFET is suitable for low-power DC applications.

Because of the above-mentioned differences, MOSFET and IGBT have their own focus in application. Generally, the rated voltage of MOSFET is about 600V, while the rated voltage of IGBT can reach 1400V. From the perspective of rated voltage, IGBTs are mainly used for higher voltage applications. From the perspective of operating frequency, IGBTs are usually used at a switching frequency below 20kHz, at which time they have higher switching losses than unipolar MOSFETs.

Taken together, IGBT is the first choice for low frequency (less than 20kHz), high voltage (greater than 1000V), small or narrow load or line changes, high operating temperature, and rated output power applications exceeding 5kw. And MOSFET is more suitable for low voltage (less than 250V), large duty cycle and high frequency (greater than 200KHz) applications.

Who should use IGBT and MOSFET? Did you choose the right one?

Figure 1: Performance comparison of different types of transistors (Source: TOSHIBA)

Key electrical parameters of MOSFET

The advantages of MOSFET determine that it is very suitable for high frequency and high switching speed applications. In a switching power supply (SMPS), the parasitic parameters of the MOSFET are very important. It determines the conversion time, on-resistance, ringing (overshoot during switching) and back-gate breakdown, which are closely related to the efficiency of the SMPS .

As a power switch, the selected MOSFET should have extremely low on-resistance, low input capacitance (that is, Miller capacitance), and extremely high gate breakdown voltage, which is even high enough to handle any peak voltage generated by the inductance. In addition, the lower the parasitic inductance between the drain and the source, the better, because the low parasitic inductance can minimize the voltage peak during the switching process.

For gate driver or inverter applications, it is usually necessary to choose a MOSFET with low input capacitance (facilitating fast switching) and higher driving capability.

Key electrical parameters of IGBT

The main advantage of IGBT is that it can handle and conduct medium to ultra-high voltage and large current, has very high gate insulation characteristics, and produces very low forward voltage drop during the current conduction process, even when a surge voltage occurs, the IGBT The operation will not be disturbed. The disadvantage is that IGBTs are not suitable for high frequency applications. Compared with MOSFET, the switching speed is slower and the turn-off time is longer.

In practical applications, the inverter technology does not have the same requirements for IGBT parameters, and the requirements for IGBTs are different.

Taken together, the following parameters are crucial in the selection of IGBT.

● One is the rated voltage. Under the condition of switching operation, the rated voltage of the IGBT is usually higher than twice the DC bus voltage.

● The second is the rated current. Due to the current overload when the load is electrically started or accelerated, it is required that the IGBT can withstand 1.5 times the overcurrent within 1 minute.

● The third is the switching speed.

● The fourth is the gate voltage. The working state of the IGBT has a great relationship with the forward gate voltage. The higher the voltage, the smaller the switching loss and the smaller the forward voltage drop.

IGBT and MOSFET in new energy vehicles

The electrification of automobiles is the general trend. Now, governments of various countries have set their own carbon peak and carbon neutral targets. It is of great significance to switch from traditional ICE vehicles to pure electric vehicles. Stricter global CO2 emission requirements continue to accelerate the process of electrification of vehicles. It is estimated that the compound annual growth rate (CAGR (VOL)) of electric vehicles/hybrid vehicles (EV/HEV) from 2021 to 2026 will reach 20.1%. The CAGR (VOL) of battery electric vehicles (BEV) called zero-emission vehicles (ZEV) will be as high as 29.7%.

Who should use IGBT and MOSFET? Did you choose the right one?

Figure 2: The growth of EV/HEV in the next 5 years (Source: onsemi)

The motor control system, engine control system, and body control system of new energy vehicles all need to use a large number of semiconductor power devices. Its popularity has opened a window for growth in the automotive power semiconductor market. Among all kinds of semiconductor power devices, the products with the strongest growth in the future will be MOSFET and IGBT modules.

According to the analysis results of IC Insights, a research institution, in 2016, the global MOSFET market reached 6.2 billion U.S. dollars, and the compound annual growth rate of the MOSFET market is expected to reach 3.4% from 2016 to 2022. It is estimated that by 2022, the global MOSFET market will be close to 7.5 billion U.S. dollars.

IGBT is the core device of the high-voltage system of new energy vehicles. Its core application is the main drive inverter. In addition, it also includes high-voltage auxiliary systems such as on-board charger (OBC), battery management system, on-board air conditioning control system, and steering. In DC and AC charging piles, IGBTs are also widely used. In new energy vehicles, MOSFETs are mainly used in automotive low-voltage electrical appliances, such as electric seat adjustment, battery circuit protection, DC motors for wipers, and LED lighting systems.

IGBT and MOSFET “core” product recommendation

AFGHL25T120RHD is a low-cost 1200V 25A IGBT of Onsemi’s automotive grade. The module complies with the AEC Q101 specification and has a rugged and cost-effective field resistance II trench structure. It can provide excellent performance in demanding switching applications, while providing low on-voltage and minimum switching loss. It can be used in systems such as EV/HEV PTC heaters, electric compressors, and on-board chargers.

Another MOSFET module of ON Semiconductor, FAM65CR51ADZ1, is a 650V power integrated module (PIM) with a boost converter, which is mainly used in the on-board charger (OBC) in EV/HEV. It can allow The design of the system is more compact, efficient and reliable.

Infineon Technologies (Infineon) has an extremely rich IGBT power module product portfolio. These product series have different circuit structures, chip configurations and current and voltage levels, covering most of the applications on the market. They are available in chopper, DUAL, PIM, four-unit, six-unit, twelve-unit, three-level, booster or single-switch configuration, and current levels range from 6A to 3600A. The applicable power of the IGBT module is as small as a few hundred watts and as high as several megawatts.

For example, Infineon’s HybridPACK series provides multiple versions based on 6 different packages, optimized for different inverter performance levels between 100kW and 200kW, and expanded the power range of IGBT modules for EV/HEV. The HybridPACK Drive in this series is a very compact power module, optimized for EV/HEV vehicle traction applications, with a power range of 100kW to 175kW, which can achieve the highest efficiency in the actual drive cycle of electric vehicles, even in harsh environments The inverter can be operated reliably under conditions.

Who should use IGBT and MOSFET? Did you choose the right one?

Figure 3: Power module HybridPACK Drive IGBT module used in the main inverter of electric vehicles (Source: Infineon)

Among them, HybridPACK Drive Flat module (FS660R08A6P2Fx) and Wave module (FS770R08A6P2x) are low-performance products in the HybridPACK Drive product family. They are economical and cost-effective. They are suitable for 100kW to 150kW inverters. As the high-end product in the product portfolio, the target application of the HybridPACK Drive Performance module (FS950R08A6P2B) is a 200kW inverter. Due to the use of special ceramic materials instead of the commonly used alumina, its heat dissipation performance has been improved by more than 20%, and a higher current carrying capacity can be achieved.

Infineon’s 600V, 650V and 800V N-channel power MOSFETs are mainly aimed at high-performance automotive applications. CoolMOS N-channel MOSFETs are the company’s representative product series, suitable for low- to high-power applications. A clever balance is achieved between high performance and price.

Concluding remarks

Power semiconductor devices, also known as power electronic devices, are the core devices for power electronic devices to realize electrical energy conversion and circuit control. The operating frequency of silicon-based MOSFETs developed in the 1980s reached the megaHz level. With the emergence of silicon-based IGBTs, power devices have found a solution between high-power and high-frequency.

In uninterruptible power supply (UPS), industrial inverter, power control, motor drive, pulse width modulation (PWM), switching power supply (SMPS) and other switching applications, MOSFET and IGBT have obvious performance due to their superior characteristics Better than other switching devices. Among them, MOSFET is mainly used for lower voltage and power systems, while IGBT is more suitable for higher voltage and power applications.

Driven by the demand for new energy vehicles, smart home appliances, and 5G, the market scale of IGBTs and MOSFETs continues to expand, and more and more companies enter this field. How to find the product that best meets your needs in a diverse market is a headache. In fact, no matter how complicated, you only need to pay attention to the main parameters we introduced above, and I believe you will definitely find a satisfactory product.

Source: Mouser Electronics