Intelligent Power Modules (IPMs): Concepts, Features, and Applications

What Is an Intelligent Power Module (IPM)?

Here’s the short answer: “Power module” refers to the presence of a power switching component (usually an IGBT), and the module is “intelligent” because it includes additional control and protection circuitry. The goal is to optimize performance and make the overall solution easier to design and implement.  

This terminology might be a bit misleading. When I see the words “intelligent power module,” my intuitive interpretation is “power supply module” (such as a DC/DC converter) plus “processor.” (In all seriousness, immediately after I wrote this sentence, a marketing email popped up in my inbox: “New Miniature 2W AC/DC Power Modules.”)

Basically, I would expect an intelligent power module to be an integrated power supply device that incorporates the digital “intelligence” provided by a microprocessor. I suppose no one can stop me from using the term in this way, because it makes sense, but it’s important to recognize that according to standard usage in the industry, an IPM is an advanced, highly integrated solid-state power switch.

 

Power Transistor Comparison 

For an excellent discussion of semiconductor devices used for high-power switching, take a look at FET vs. BJT vs. IGBT: What’s the Right Choice for Your Power Stage Design?

 

IPM Features

Optimized high-power switching is much more than just turning a FET or IGBT on and off. The following list conveys the features that might be incorporated into a power-switching application, and it also conveys the features that we find in intelligent power modules. 

• Gate-drive circuitry must apply the proper voltage and supply large amounts of current for fast switching.
• Gate-drive logic can also be designed to prevent high-side and low-side IGBTs from conducting simultaneously. This functionality goes by a few different names: shoot-through protection, cross-conduction prevention, or interlock circuitry.
• Protection circuitry should be able to detect and address overcurrent, overtemperature, short-circuit, and undervoltage conditions. If the system needs to keep records of fault events or operational temperatures, some sort of communication functionality will also be required.
• EMI specifications may necessitate specialized switching behavior.
• Space or cost restrictions might oblige a designer to reduce power losses that occur during switching and on-state conduction so that a smaller heatsink or enclosure can be used.
• Some applications require power factor correction (PFC).

 

This diagram illustrates the interlock functionality of the FNB81060T3, a 600 V IPM from ON Semiconductor. Notice how the high-side and low-side gate voltages don’t respond to input signals that would lead to cross conduction.

 

Basically, IPM manufacturers try to integrate any feature or functionality that they can in order to enhance the performance, increase the manufacturability, lower the cost, reduce the size, improve the reliability, simplify the implementation, or accelerate the time to market of a semiconductor-based power-switching circuit.

 

Voltage Specifications

Intelligent power modules are directed primarily at the high-voltage market. “High” is a relative term; in the parlance of low-voltage engineers such as myself, 50 V might qualify as “high,” but that’s actually very low in the context of IPMs.

For example, the lowest maximum voltage rating in Infineon’s CIPOS Nano family is 40 V. The highest is 600 V, and the Nano line is the smallest, lowest-power option in Infineon’s lineup. The Maxi family tolerates voltages up to 1200 V and can dissipate 50 W of power per IGBT.

As another example, Powerex uses the term “low power” to describe IPMs that are specified at 50 A and 600 V. The higher-power modules can handle 75 A. 

 

Form Factor

Intelligent power modules tend to come in through-hole packages that I would describe as somewhat nonstandard. Here are some examples:

 

This is a rendering of the FNB81060T3 (mentioned above).

 

PFC-Integrated Ipm For Low-Power Device

Click here for more information on the CIPOS Mini IPMs from Infineon.

 

Applications

Intelligent power modules are most closely associated with motor control, but they’re also used in uninterruptible power supplies, inverters, and renewable energy systems. The list below indicates some of the intended applications mentioned by manufacturers.

• Home appliances: fans, air purifiers, washing machines, air conditioners, refrigerators, vacuum cleaners
• Industrial: pumps, compressors, HVAC, elevators
• Automotive: AC compressors, oil pumps, on-board charging in electric vehicles

 

CISSOID developed an aerospace IPM that uses silicon carbide (SiC) MOSFETs instead of IGBTs.

 

Conclusion

Intelligent power modules greatly facilitate the task of developing a reliable, efficient, compact circuit for high-power solid-state switching. These versatile components can find a place in many applications, and they will surely grow in popularity and importance as system requirements and performance expectations become more challenging for designers.