Why are IGBTs used in new energy vehicles?
Jan 05, 2023 View: 424
IGBT is the core component in new energy vehicles, and the global supply is still mainly concentrated in international integrated component manufacturers (IDM). Institutions believe that benefiting from the rapid development of domestic new energy vehicles, IGBT for new energy vehicles has become the number one application area of IGBT in China in 2020, accounting for about 30%.
Today, let's talk about IGBTs specifically from the perspective of technology.
What is IGBT?
IGBT is called Insulated Gate Bipolar Transistor (IGBT), which can be equivalently regarded as a combination of MOS tube and Triode.
The working principle & characteristics of Triode and MOS
Triode
A triode is a current-controlled transistor, which allows a larger current to pass between the collector and emitter by applying a small current at the base. The most applied in the circuit amplification role and switching role.
As shown in the figure above, PNP transistor Q1 in the circuit belongs to the switching role, when the switch KEY1 pressed Q1's base and power GND conductive, current flows from Q1's collector to the emitter at this time, LED1 is lit. Q1 is an ordinary triode, Ice only a few hundred mA. driving a light-emitting diode is more than enough.
The GTR is a type of transistor, a giant transistor, also known as a power transistor because it can work at high voltages and high currents, GTR is also a current-driven device, the on-state resistance between the collector and emitter is very small after conduction, and the current-carrying density is very high. It is possible to achieve very high pathway current. However, in high-power application scenario, it needs to consume higher driving current, so we have to seek new breakthrough point.
Mos tube
MOS tube, also known as insulated grid field effect tube, pay attention to a few words "insulation", "field effect". This will be the biggest difference between MOS and triode.
The main structural feature of the MOS tube is a layer of silicon dioxide insulation between the metal gate and the channel, so it has a very high input impedance. This is the origin of the word "insulating" in its name.
Due to the existence of the insulating layer, after the voltage is applied between the gate and the source, the conductive channel is formed by attracting carriers under the action of electric field, so the working principle can be understood as it is the use of VGS to control the amount of "induced charge" in order to change the "induced charge" formed by these The operating principle can be understood as it uses VGS to control the amount of "induced charge" to change the condition of the conductive channel formed by these "induced charges", and then achieve the purpose of controlling the drain current. So this is the origin of the "field effect" in its name.
In some high-voltage drive scenarios, the need for high voltage MOS, so you have to make adjustments from the structure, the internal structure has to be made very thick, while bringing a new problem is to lead to increased on-resistance. Different voltage MOS tube, its on resistance in the on resistance of the proportion of different parts of the distribution of resistance.
For example, the epitaxial layer resistance of the 30V MOS tube is only 29% of the total on-resistance, and the epitaxial layer resistance of the 600V MOS tube is 96.5% of the total on-resistance. To obtain a high blocking voltage, it is necessary to use a high resistivity epitaxial layer with increased thickness. This is the reason for the high on-state resistance of high withstand voltage MOS.
Advantages and disadvantages of transistors and MOS tubes.
Triode (specifically GTR giant transistor)
- Advantages: many carriers, low on-resistance.
- Disadvantages: current control method, consumption of larger drive current.
MOS (specifically high-voltage MOS)
- Advantages: high input impedance, almost no consumption of drive current.
- Disadvantage: large on-resistance.
So how should I choose in some high-voltage, high-current drive scenarios? For qualified and efficient circuits, the disadvantages of any of the above MOS tubes and transistors are not allowed to exist, and will greatly affect the efficiency of the circuit, while generating a relatively difficult to overcome heat, affecting the life of the entire product.
Applications of IGBTs
IGBT is the core device for energy conversion and transmission, also known as the "CPU" of power electronics devices, mainly used in aerospace, rail transportation, smart grid, electric vehicles and new energy equipment and other fields.
The following are the specifications of FGH60N60SMD from Centson Semiconductor, mainly used in solar inverters, UPS, welding machines, etc. As you can see, the withstand voltage can reach 600V and Ice can reach 120A at room temperature.
Why are IGBTs used in new energy vehicles?
01 Application in charging pile
When charging the battery with 220V AC mains power, it needs to convert AC power into DC power to charge the battery through the power conversion circuit designed by IGBT, and at the same time, the 220V voltage has to be converted to above the appropriate voltage to charge the battery pack.
For example, Tesla's fast charging is high power DC charging, the charging power is generally up to 40kW or more, converting AC power from the grid into DC power, delivering it to the fast charging port of the car, and the electrical energy goes directly to the battery charging.
02 Application in motor drive
New energy vehicles use three-phase asynchronous AC motors, and the DC power from the battery cannot drive the motor rotation directly. When the battery is discharged to drive the motor, the circuit composed of IGBTs converts the DC power into AC power used by the AC motor, and at the same time plays a role in the control of frequency and voltage conversion of the AC motor.
The following is a simple diagram of a DC power supply that uses the switching action of IGBTs to drive motor rotation. The controller is responsible for outputting signals that control IGBTs 1 to 6 to turn on and off, thus converting the DC power from the battery into AC power that can drive the rotation of a three-phase asynchronous AC motor.
03 Application in Vehicle Air Conditioning
The working principle of the on-board air conditioner of a new energy vehicle is the same as that of an electric drive, i.e., the DC power from the battery is converted into AC power through an inverter, which drives the air conditioner compressor motor to work.
04 Inverter
Some new energy vehicles are also equipped with an interface that outputs 220V/50Hz AC to the outside. This process converts the DC power from the battery into AC power through an inverter circuit, and IGBT is also an indispensable device in this process.
Conclusion
IGBT is a power semiconductor device, which can be said to be one of the core technologies of electric vehicles, and the good or bad of IGBT directly affects the release speed of electric vehicle power. Tesla Model X uses 132 IGBT tubes, of which 96 for the rear motor and 36 for the front motor IGBTs account for about half of the cost of the motor drive system.