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## How much is the dispersing power of IGBT?

release time:2022-03-30Author source:Dr. Geng Electrical Electronic TechnologyBrowse:1525

foreword

01

Hello, everyone, I haven't updated my articles for a long time. On the one hand, I'm busy with my work, and I'm really lazy. According to statistics, the average time I spend on my mobile phone after work every day is almost two hours. It's a pity. As a positive and promising young man, how can I allow myself to go down like this? So I quit my mobile phone and keep doing popular science articles!

periodLet's have a chatIGBTDissipate power, often hear friends askIGBTWhat is the maximum current that can run? How high can the switching frequency be? Actually, yes.IGBTAnyone who knows something about application should know that there is no way to give accurate and quantitative results of these problems.IGBTThe switching frequency and output current of the device mainly depend on the heat dissipation of the device. As long as the heat dissipation is good enough, put theIGBTThe generated heat can be taken away in time, then you can.“Overclocking”。The reason why power manufacturers call some tubes fast tubes is that they are optimized.IGBTThe switching speed reduces the switching loss.thatIGBTWhat is the power consumption of heat dissipation during operation?Maybe you don't have a very intuitive concept. Today, we will combine some household appliances andIGBTTake a look at the horizontal comparison of power consumption.

IGBTBrief introduction of loss

02

First, let's briefly introduce the loss of IGBT.IGBTThe loss is mainly divided intoSwitching loss and conduction lossTwo parts. Switching losses are divided intoTurn-on loss and turn-off loss，Because most applications of IGBT areInductive load，In the process of turning on, the collector current rises first, and then the voltage drops. On the contrary, for the turn-off transient state, the collector voltage of IGBT first builds up, and then the current drops, so thatIGBTThe switching process, voltage and current will haveOverlapping part，In this process, the voltage and current are both positive, and the power multiplied by them is also positive, so it willrelease energy。Although IGBT is a power electronic switch, it is different from mechanical switch when conducting, and there will be a voltage drop of several volts, so it will also produce a certain loss, which is called conduction loss.

For most industrial applications,IGBTThere will be a diode inside. Although the diode is a passive device, because the buddy next to it is a switching device, he can't and can't.pay attention to one's own moral uplift without thought of othersHow fast the IGBT turns on, how fast it turns off itself.，However, the innate material characteristics determine that you don't have the ability to turn off at that moment, so that the diode will bear the reverse voltage and reverse current at the same time in a short time. At this time, the multiplied power of the two is positive, so it also needs to release energy. The forward turning-on of the diode will also cause some loss, but it is smaller than the turn-off loss, so the switching loss of the diode mainly refers to the turn-off loss. At the same time, the reverse turn-off requires a certain recovery time, so the switching loss of the diode is also called the reverse recovery loss. Sum of diodesIGBTSimilarly, although the conductance modulation method is adopted to reduce the direct voltage, there are still1-2VThe forward voltage drop of the diode cannot be ignored under high current, which is the conduction loss of the diode. It's not easy to think about diodes, not only under the pressure of big brother next to them, but also by new materials.SiCThe risk of diode replacement shows that the compression resistance of diode is also extraordinary. . . It's a little off topic. Go on. . .

IGBTLoss calculation

03

After knowing the IGBT switching loss, let's look at it again.IGBTThe loss calculation, here Lao Geng wants to show you a wonderful algorithm, the purpose is to let everyone firstIGBTdissipationAnd power and energyHave a deep understanding of the relationship. Here, we take Infineon's 1700V 1400A module as an example for a simple explanation, with the model number ofFF1400R17IP4。The little friends who read the past content may ask Lao Geng why you always take this pipe as an example. Remember a word, I am engaged in high power, and the first thing I came into contact with is this module. I have deep feelings for this module. Let's take a look at the corresponding relationship between switching loss and current of this module, as shown in the following figure.：

It can be seen that as the current increasesIGBTThe switching loss becomes larger, and the loss is also related to temperature. with regard to1400AThe module, with good heat dissipation, can run to800A，Then let's start with800AFor example, it is not difficult to find out from the above figure.IGBT125℃ 800AUnder the current of each turn-on loss is280mJ，The unit can also bemWs，Turn-off loss is420mJ，Then the total switching loss per time is700mJ。supposeIGBTThe switching frequency of is2kHzThe 1s of IGBT will generate 700mJ *2000= 1400J of heat, which is equivalent to 1.4 kWh of electricity consumed in one hour. That 1s generation1400JEquivalent to how much power of electrical equipment? After simple conversion, it can be equivalent to a1400WOld Geng looked around the household appliances, found the hot water kettle steaming, and looked at the famous brand.1500W，Coincidentally, it is similar to the power consumption of the module.

Some friends may say that you are too unprofessional. How can you do that? Yes, the above calculation is really meaningless, because it is divorced from practical application, and at the same time, it doesn't take into account conduction loss, diode loss and so on. Lao Geng's main purpose is to popularize science for everyone.And power and energyThe difference, as long as you feel there is something to gain. in factIGBTThe loss calculation formula is complex, which is related to circuit topology, power factor,PWMModulation and so on. There are many online resources for detailed calculation formulas. You can look for them yourself, and most of them are from a document of Infineon.“Dimensioning program IPOSIM for loss and thermal calculation of Infineon IGBT modules”，If you can't find it, you can also contact Lao Geng. The contact information has been available in the past. The following is based on Infineon'sIPOSIMSimulation software is commonly used in two ways.IGBTFor an example of inverter power dissipation, take a look.IGBTHow big is the loss when working?

Case 1: New Energy Electric Drive

04

Now that new energy electric vehicles are so popular, let's take Infineon HP Drive module FS820R08A6P2B as an example. This is a 6-unit automotive power module. According to friends engaged in new energy, this module is used in Weilai, Geely and GM Buick, and it is a star product. The rated voltage of this module is 750V, the current is 820A, and there are 6 IGBT's inside. The output power of the driver made of this module can reach 200kW, which is absolutely leverage when used in passenger cars. The picture of the module and the internal circuit are shown in the following figure:

Infineon IPOSIM is used for simple power simulation. Under the conditions of battery voltage of 400V, output circuit of 500A and switching frequency of 8kHz, the dissipation power of a single IGBT is 500W, and that of the whole module is about 3000W W. Geng looked around the home appliances again, and found that the power of the water heater for bathing was just 3000W W. What a coincidence. At this time, there must be some friends who will say, Lao Geng, how can you be so calculating? Haha, you know. . . It's hard to imagine that such a palm-sized module can generate so much power consumption when working.

Case 2: Medium Voltage Inverter

05

The heat dissipation power of the above module is not small. Let's build a big module, and take the medium voltage 3300V high power three-level inverter as an example to illustrate. The inverter adopts 4500AV 1200A IHV package module with an output current of 500 A. A total of 12 IGBT modules and 6 diodes are required for the three levels, as shown in the following figure:

At half bus voltage2800V,output current500A，switching frequency1kHzThe simulation data of is shown below, and it can be seen that the switching loss of the three-level outer tube is close.2500W，The switching loss of the tube is only740W，It's mainly related to the working condition of the inverter. Later, when you have the opportunity, you can talk about this topic specifically, so I won't talk about it in this issue.

After simple calculation, the total power consumption of a single three-level bridge arm is 8,400 W, and the total power consumption of those three phases is about 25kW. This power loss is still very large, but at this time, the output power of the inverter is also very large, nearly 3MW. Looking around, it seems that there are no such big appliances in the home. I suddenly thought that I just paid the electricity bill some time ago. I looked at the list. The average monthly electricity bill is 200 kWh, and the electricity bill is 100 yuan, so it is about 7 kWh per day in 3.5 yuan. This electricity consumption should be able to represent most households. If the inverter mentioned above runs at full load, how many users' electricity consumption will the heat generated by IGBT be equivalent to? How much is the electricity bill wasted in a day? Interested friends can calculate by themselves. Here's the answer directly: 89 households, 312 yuan. Are you surprised? It's almost enough electricity for users of a building. Oh, some friends reminded that it should be calculated according to the industrial electricity bill. Well, the price is higher. . .

Some of the above cases are just some simple simulation data, and there is still a certain gap between them and the actual application. Don't be too serious, just take it as popular science. However, it is not difficult to find out how critical the heat dissipation of IGBT is. If such a large amount of heat is not handled well, it will be dangerous. . .

Ok, let's share it here today. If there is anything wrong with the above content, please criticize and correct me! If you feel that you have gained something, please help like it and forward it, so that this article can be seen by more people in need. Thank you!To know more about power electronic hardware, please search WeChat official account's "Dr. Geng's Power Electronic Technology" on WeChat, which will be updated every week to take you to the ocean of power electronic technology!Some of the pictures are from the Internet. If there is any infringement, please contact the author to delete them!

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