600 V IGBT IPM Achieves Industry Top-Class Low Noise and Low Losses: Advantages and Challenges of Using IGBT IPMs

In April 2021, ROHM released the “BM6437x Series” of new 600 V IGBT IPM (Intelligent Power Module) products. The BM6437x series achieve industry top-class* levels for both noise characteristics and low losses, making possible simplified noise filters and reduced power consumption; incorporated functions contribute to fewer components and less design man-hours. In connection with these BM6437 series, we spoke with Mr. Keitaro Ado, who is a ROHM FAE, regarding matters ranging from development background through to characteristics and product specifications.
*As of April 29, 2021, ROHM survey

–With the release of these new 600 V IGBT IPMs, I’d like to ask about the background to development, features, and product specs in a little more detail. To start with, please tell me about the development background.

The background in which development of the BM6437x series was undertaken included a strong demand for IGB IPMs in power conversion applications such as inverters, and the need for more compact equipment with lower power consumption. It was anticipated that power devices that handle electric power conversion could contribute in these areas.

–I’d like to start with some basic questions. What are reasons for the strong demand for IGBT IPMs in inverter applications and the like?

IGBT IPMs are popular for use in inverters and similar products; this market includes what are positioned as standard products in the industry, as well as products compatible with the former. One reason for this is the advantages of IPM configurations. The main forms taken by power devices are individual elements (discrete semiconductors), power modules, and IPMs. Power modules differ from IPMs in that they incorporate multiple discrete semiconductors in a single package, but require separate driving circuits and protection circuits. IPMs, on the other hand, include driving circuitry and protection circuits in one package, in addition to discrete semiconductors; this is the “intelligent” part of the “Intelligent Power Module”.

–Then, would one advantage of IPMs be the fact that pretty much all the necessary circuits and functions are combined in one package?

That’s right. That is an important point. First, incorporation in an IPM can greatly reduce the board area required for implementation of the same functions. As I think you can imagine, the discrete packages of IGBTs and other power devices must be of a certain size in order to dissipate heat. In addition, the LSIs and peripheral components for driving and protection are also necessary. The graphic shown below compares representative examples. By using an IPM, the board size can be reduced, and consequently the device can be made more compact.

Next, in an IPM the necessary peripheral circuitry and components are combined to complete one function, so that compared with discrete semiconductors, the design is dramatically simplified. Moreover, in addition to a simplified design, the internal circuitry and wiring are optimized so that superior performance is obtained, and functions and characteristics that would require verification and guarantees by the user in the case of a discrete design are, in an IPM, already verified by the manufacturer and some specification items are guaranteed. In recent years, shortening of development and design periods has been an urgent issue for designers, so I think this is likely to be a major advantage.

–From the graphic image, it appears that discrete designs are superior with respect to “customizability”. What specifically does this mean?

To put things simply, an IPM concentrates functions in a complete package, and while there are some products that enable external adjustments of certain functions, in essence, the product is made for use with the given specifications. In the case of a discrete configuration, of course various adjustments become possible, and in some cases optimization, what might be called tuning, is possible. However, this requires a considerable amount of time and quite a bit of expertise. I think the issue of customizability should be thought of as part of a trade-off of sorts.

–Then it appears that IPMs, with their reduced space requirements, can contribute to compactness, and with the required functions concentrated in the module and verified by the manufacturer, design is simplified and can be performed rapidly, and these advantages have resulted in large demand.

That’s right. There are other positives as well, but we can say that these advantages go a long way to resolving issues being faced by today’s design engineers.

–I understand what you say about the strong demand for IGBT IPMs and their compactness as the background of development. Well then, could you discuss the remaining issue, reduction of power consumption?

Reduction of power consumption is essentially a demand made of all equipment and components, but in point of fact, there is a tendency for power consumption to increase.

–Wha…to increase!? After all I’ve been told, I’d have thought it is decreasing.

The newly developed BM6437x series are intended primarily for use in major home appliances and smaller industrial equipment. However, with the popularization of IoT, accompanying automation and more sophisticated functions in such products, there is a tendency toward increased power consumption. With the adoption of IoT, communication functions are added, and a constant current feed is necessary for communication. Hence the standby power consumption increases. In addition, in order to accommodate larger display sizes and more advanced motor functions, the devices that perform driving and control must also be larger-scale and equipped with advanced functions, and consequently power consumption during operation also increases. As a result, further reduction of power consumption is sought, and there are expectations that losses will be reduced in the power devices of power conversion circuits as well. For this to occur, improvements in the characteristics of the IGBTs themselves, and enhancement of driving and control technology through IPM incorporation, are necessary.

–Well then, could you please explain in some detail how the various issues that constituted the development background of the BM6437x series have been addressed?

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