Concept of Intelligent Power Module for Motor Drive Inverters
Inverter designers for small AC motors in consumer and general-purpose industrial applications must meet increasingly difficult and stringent efficiency, reliability, size, and cost constraints. Traditionally, many of these small inverter designs make use of discrete power device packages, as well as the auxiliary components required to realize interface, drive, and protection functionality.
To meet all of the spacing and layout requirements of the gate drivers and discrete power devices combination, this approach necessitates relatively large and complex PCB designs. Another perplexing issue is maintaining consistent performance and reliability when the characteristics of the drivers, such as servo drives and power devices, are mismatched.
An integrated power module, which contains all of the required power devices as well as matched gate drivers and protective functions integrated with low-voltage and high-voltage ICs, is an alternative solution to these problems (LVIC & HVIC). Finally, when compared to a discrete solution, the fully integrated package solution reduces stock handling and assembly time.
Mitsubishi Electric pioneered the DIPIPMTM concept in 1997, based on assembling bare power chips and LV/HVICs using a compact transfer molded lead frame design to maintain optimized and consistently reliable performance while meeting the module’s low cost requirements, building on the success of its Intelligent Power Module (IPM) approach.
With the recent addition of the surface mounted SP2SK module and the high current rated Large DIPIPM+, Mitsubishi Electric’s transfer molded IPMs now cover a power range of several tens of watts to more than 12kW, as shown in the figure below.
Current DIPIPM lineup.
Topology and Protection Functions
In the lower power range, the topologies of hard switching servo drives are similar. The amount of used semiconductors should be kept to a minimum for cost and reliability reasons.
The three-phase full-bridge using Insulated Gate Bipolar Transistors solution can be found in nearly all types of servo drives, home appliance inverters, fan inverters, and pump inverters (IGBT). When compared to MOSFET technology, the advantage of using IGBT is the high blocking capability combined with lower conducting losses.
The topology used in the Super Mini DIPIPMTM series is depicted in the figure below.
The Super Mini DIPIPM series is integrated with the topology.
Consumer and industrial product markets are becoming more active. Smart home technology trends, as well as industry 4.0 (IoT) requirements, drive designers to create next-generation inverters in a shorter time frame and at a lower cost.
Mitsubishi Electric’s transfer-mold modules outperform the market in this category due to their highly integrated, simple-to-implement, and cost-effective solution features. Because of the compact module outline and sophisticated pin design with well-designed clearance and creepage distances, they are able to reduce the size of the inverter.
Furthermore, because each series has several current ratings, the line-up with the different series allows for the design of a scalable platform inverter. With blocking voltages of 600V and 1200V available, common single and three-phase applications are covered. The UL recognized isolated thermal interface with a rating of 2.5kV (1.5kV for the SP2SK module) and a low thermal impedance reduces the effort for a user-safe design while also meeting the higher requirements for industrial use.
Furthermore, the use of organic materials reduces mechanical stress in the module significantly because the thermal expansion coefficients are better matched than ceramic materials. For high power ratings, an additional internal heatsink is molded into the module for improved heat dissipation.
Mitsubishi Electric modules are made up of six IGBTs with independent freewheeling diodes or six reverse-conducting IGBTs (RC-IGBT). One or three high side gate driver ICs, a low side gate driver IC, and three bootstrap diodes with current limiting resistors are integrated for easy control of the IGBT, depending on the series.
The transfer molded modules from Mitsubishi Electric can be powered by a single 15V supply voltage source and controlled directly by an MCU due to the level shifter integrated with the HVIC, eliminating the need for galvanic isolation to control the high side switches. All dies are directly mounted on the lead frame without the use of a PCB within the module, resulting in market-leading lifetime performance.
SLIMDIP, Super Mini DIPIPM, and Large DIPIPM are the internal structures (clockwise).
The low side IGBT emitters are open, allowing an independent current measurement of each single motor phase via shunt resistors. With the ability to detect three-phase currents independently, cutting-edge position-sensor-free machine control can be used in the user’s control framework.
The output signals of the current Measurement shunts are also used for internal short circuit protection, which prevents the module from operating outside of the short-circuit safe area of operation (SCSOA). Furthermore, the modules include a temperature output with a linear temperature-voltage dependency, resulting in simple condition monitoring with the option of incorporating dynamically controlled de-rating and over-temperature protection.
Motor inverters can be found in a wide range of applications. Mitsubishi Electric provides a variety of packages as well as the best solution for each need.
The surface mount SP2SK module is the one with the smallest outline. In addition to the DIPIPM family’s standard protection features, interlock protection is built in, preventing arm shoot-through if the high and low side switches are turned on. Because of the compactness of this module due to the use of RC-IGBT, it is ideal for low power to single-phase applications such as dishwashers or fans.
The SLIMDIP package is ideal for achieving a higher power rating. It utilizes the same RC-IGBT technology as well as through-hole technology to provide exceptional compactness. The time-to-market is greatly reduced by meeting the requirements of price-sensitive platform inverters used in home appliances with power ranges ranging from 0.5kW to 1.5kW and a sophisticated pin design.
Mitsubishi Electric pioneered the transfer mold IPM module market with the Super Mini DIPIPM package. It supports a wide range of current ratings, allowing for the precise selection of the best-fitting module. In addition to the silicon IGBT and silicon MOSFET models, two SiC MOSFET modules based on Mitsubishi Electric’s long experience with silicon carbide are available as a highlight.
Because of their larger size, the Mini DIPIPM packages allow for even better heat dissipation and, as a result, higher power ratings. Furthermore, the longer pin distances enable the use of 1200V IGBTs in some models.
The Large DIPIPM package is designed for high-power inverters with limited space and a PCB-based design. A wide current range is available with blocking voltages of 600V and 1200V.
One of the most recent developments is the DIPIPM+ and large DIPIPM+. The package includes a three-phase rectifier, a three-phase full-bridge, and an optional brake IGBT based on Mitsubishi Electric’s experience and knowledge. With the highest level of integration and compactness, it is the package that provides the most comprehensive solution to the user, shortening the component selection process and lifetime evaluation.