600 V IGBT IPM Achieves Industry Top-Class Low Noise and Low LossesThree Features and Proprietary Functions Resolve IGBT IPM Issues

–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?

To start with, the most important point about the BM6437x series is that they achieve both noise performance and low losses that are among the best in the industry*.
*As of April 29 2021, ROHM survey

–Up till now, you haven’t said anything about noise.

I think that in essence, all the manufacturers are making efforts to reduce losses in IGBT IPMs in order to reduce power consumption. Reducing losses in IGBTs generally means reducing switching losses and conduction losses. To reduce switching losses, raising the switching speed is generally effective, but this causes radiated emissions (EMI) to increase. Recently low losses have been prioritized to the extent that EMI has increased, and measures to satisfy EMC (electromagnetic compatibility) requirements have not been adequate, and so in addition to low losses, low noise has also come to be demanded. The 6437x series of IGBT IPMs were developed with special efforts made in this area, aiming at compactness and even greater ease of use.

I will be explaining the features of these products, but first I would like to summarize the BM6437x series, to help in understanding those features.

The BM6437x series are IPMs that encapsulate IGBTs, gate drivers, bootstrap diodes, and fast recovery diodes for regeneration in a single package that function as DC input, 3-phase AC output IGB inverters. The products have a V_CES rating of 600 V; there are four types, with I_C ratings of ±15 A/±20 A/±30 A/±35 A. The package is HSDIP25.

Block diagram and packages of the BM6437x series of IGBT IPMs

The following are the three main features of these series.

• 1. Combines low noise and low loss figures that are top-class in the industry
• 2. Greatly improved precision of the temperature monitoring function, possibly enabling omission of an external thermistor
• 3. Erroneous mounting can be detected after board mounting using a product identification function

The first of these I brought up earlier as the most important point: these products are top-class in the industry in terms of both low noise levels and low losses. The BM6437x series have peak radiated emission levels that are at least 6 dB lower than general products, achieved by optimization of the IGBTs and the soft recovery performance of the internal FRDs (fast recovery diodes). The internal IGBTs are the latest generation of devices, with reduced conduction losses and switching losses, so that power losses are lowered by 6% (at fc=15 kHz) compared with conventional s products.

These low-noise characteristics and loss levels are among the best in the industry, and as I explained earlier, although there is a tradeoff involved when higher switching frequencies, raised in order to reduce losses, tend to result in increased radiated emissions, the twin maladies of losses and noise are both suppressed to a very high degree.

–I see that it is important that both losses and noise are low. What advantages result from this?

By keeping radiated emissions low while reducing power consumption of the installed equipment, alleviation of EMC countermeasures can be expected. In essence, a noise filter is necessary, but it may be possible to use a simpler filter compared with conventional devices. In some cases, it may also be possible to lead to fewer components and lower costs.

–And the second feature area was greatly improved precision of the temperature monitoring function?

Many general products guarantee a temperature monitoring precision at 90°C of ±5% (equivalent to 5°C). The BM6437x series succeed in greatly improving on this, guaranteeing a precision at 90°C of ±2% (equivalent to 2°C), comparable to the value for thermistors. Because these new models offer this performance, it may be possible to dispense with the external thermistors that until now have been used for high-precision temperature monitoring; when it is possible, the number of components and design man-hours can be reduced.

–The third feature is, after mounting on a board, the ability to detect erroneous mounting by means of a product identification function. What kind of function is this?

Ordinarily, the part number of an IPM is stamped on the bottom surface of the package, so that after mounting on a board, the part number is not visible. This is also the case for the BM6437x series, but there are models that use the same package but have different current ratings, and there are products of other manufacturers that use the same package as well, so that even when erroneous mounting occurs, the mounted device cannot be identified on the basis of external appearance. In order to make possible identification of a product after mounting, the BM6437x series are newly provided with a function that enables identification of the product by measuring the resistances between specific pins.

–And how exactly do you identify a device?

Quite a unique function, isn’t it. You have described three major features; is there anything else I should know?

In addition to these three features, the protection functions of the BM6437x series are very convenient; allow me to explain them. IGBT IPMs handle large amounts of power, and so protection functions are vital. In addition to being equipped with basic protection functions, the BM6437x series are also provided with FO pins that can be used to notify an external device in the event that protection has been activated.

The internal protection circuits include short circuit protection (SCP); control power supply under-voltage-locked-out circuit (UVLO); and thermal shutdown circuit (TSD);. UVLO is provided on both the high and low sides, but the other two circuits are protection functions provided on only the low side. These are well-known protection functions, and essentially protect the IPM itself from failure and the like.

The FO pin is for fault output. When a protection circuit is actuated, outside equipment can be notified of that fact; but instead of simply setting a flag, the length of the output signal is used to indicate which protection function has been actuated. As indicated in the table, if for example it is the short-circuit protection, and the protection function operating time (event time) is 45 µs or less, then FO outputs a 45 µs signal. By using an external control MCU to detect this signal time, it can be determined which type of protection has been actuated, and this can be recorded as well. Application notes explain the protection functions and the FO output, and they should be consulted for further details.

–I see. This is what puts the “intelligent” in IPM.

Yes. The incorporation of such functions is another advantage of these IPMs.

–We are approaching the end, but could you please introduce the BM6437x series lineups and applications?

As I explained briefly at the outset, the BM6437x series are 600 V IGBT IPMs, available in four types with current ratings of 15 A, 20 A, 30 A or 35 A.

Product Lineup

Part No.	Current Ratings (A)	Collector- Emitter Voltage VCES (V)	Temperature Monitoring Function	TSD*	Package (mm)
BM64374S-VA	15	600	Yes	Yes	HSDIP25 (38.0mm×29.4mm×3.5mm)
BM64375S-VA	20
BM64377S-VA	30
BM64378S-VA	35
BM63373S-VC	10				HSDIP25VC (38.0mm×33.7mm×3.5mm)
BM63374S-VC	15
BM63375S-VC	20
BM63377S-VC	30
BM63573S-VA	10			No	HSDIP25 (38.0mm×29.4mm×3.5mm)
BM63574S-VA	15
BM63575S-VA	20
BM63577S-VA	30
BM63573S-VC	10				HSDIP25VC (38.0mm×33.7mm×3.5mm)
BM63574S-VC	15
BM63575S-VC	20
BM63577S-VC	30

*TSD: Thermal Shut Down

The BM6437x series were developed for inverters used with motors in major home appliances and industrial equipment. Main applications include the following.

• ・Inverter devices for control of AC 100 to 240 Vrms （DC 400 V or lower) class motors
• ・Inverters for air conditioners, washing machines, refrigerators, and other major home appliances
• ・Inverters for smaller industrial equipment such as small-capacity motors used in industrial robots
• ・Other compressor or motor-equipped applications in which inverter control is required

There are specific examples of these; by all means please consult them.
https://www.rohm.com/solution/industry/motor/motor-iso-240v-ac-servo

–Could you please summarize everything, then?

IGBT IPMs incorporate discrete IGBTs, driving circuits, and protection circuits in a single package, and therefore they feature a simple, space-saving design. They are thus highly convenient devices, but in recent years there have been demands for power devices that are more compact and have lower power consumption. The BM6437x series are new IGBT IPM products that were developed with these demands in mind.

I have described three major feature areas of the BM6437x series. In particular, I think that the achievement of low noise performance and low losses that are both in the top class for the industry is a major contribution. As I explained, these new products help resolve the problem of inadequate EMC countermeasures to the increase in radiated emissions that result from the emphasis on low losses, while also leading to reduction in the number of components and design man-hours.

In addition, these products are provided with unique functions, such as a temperature monitoring function with precision rivaling that of thermistors, a product identification function, and an FO pin that provides notification of the type of protection function that has been actuated. These IGBT IPMs are well-suited to motor inverter applications for major appliances and small industrial equipment.

I was not able to explain the product specifications or details of the various functions, but in addition to the data sheets and applications, I hope your readers will review the materials presented in “Related Information”. For a summary of the specifications, I think it will be useful to consult “600 V IGBT IPMs: BM6437x6337x Series –Specifications–” in TECH INFO: Product Key Points on Tech Web.

–Thank you very much.