A new injection-molded surface-mount intelligent power module for low-power motor drive

Summary

This article introduces a new injection-molded surface mount (SMD) intelligent power module (IPM) for low-power motor drive, suitable for refrigerators, dishwashers and fans and other white goods applications, with small size and reliability High characteristics. By adopting new packaging technology and thinner reverse-conducting IGBT (RC-IGBT) chips, the new surface mount IPM not only successfully integrates three-phase full-bridge circuits, IGBT gate drive ICs, and BSD (Bootstrap Diode) In a compact surface-mount package, and built-in protection functions including upper and lower arm interlock, temperature signal analog output, short circuit protection, and control side power supply undervoltage protection. This series of modules are manufactured using injection molding packaging technology, with good thermal expansion coefficient matching, achieving a sufficiently small package size, which helps to significantly reduce the overall size and design complexity of the variable frequency drive system. In short, this series of products can greatly simplify and shorten the design process of inverter power stage in home appliances.

1. Summary

As one of the most important measures to deal with global warming, the use of variable frequency drives in low-power household appliances applications such as indoor/outdoor fans of air conditioners, dishwasher drainage/recirculation pumps, refrigerator compressors, etc. has developed rapidly in recent years. Due to the limited internal space of such products, one of the most important requirements for inverter system design is to strictly limit the size of the inverter drive board.

The traditional variable frequency drive solutions in this kind of home appliance applications often use discrete components to realize the three-phase switching circuit topology, which requires a large number of electronic components and complex assembly processes. Therefore, there is a need for a device solution that can highly integrate key components such as IGBT, FWD (freewheeling diode), driver IC, and BSD (bootstrap diode) and have a compact package. To meet this market demand, Mitsubishi Electric has developed a series of surface mount IPM products with rated specifications of 1A/600V and 3A/600V, which can provide good solutions for low-power home appliance applications.

The package outline and internal circuit block diagram of surface mount IPM series products are shown in Figure 1 and Figure 2 respectively.

Figure 1 Surface mount IPM package outline

Figure 2 Block diagram of internal circuit of surface mount IPM

In order to integrate as many discrete components as possible into the IPM package, we adopted an RC-IGBT chip that integrates IGBT and FWD into a single chip to ensure that there is enough space for other chips/device packages. At the same time, bootstrap circuit components such as IGBT gate drive IC and BSD are also integrated into this compact package.

2. New RC-IGBT chip technology

Based on Mitsubishi Electric's ultra-thin wafer process and the 7th generation of CSTBTTM chip technology, the new RC-IGBT chip perfectly integrates IGBT and FWD in the same chip, and uses a microfabrication process to achieve low VCE (sat) and low power loss , In order to obtain better cell spacing and improve the carrier storage effect. Figure 3 shows the structure comparison between the 7th generation IGBT chip and the previous generation chip.

Figure 3 Comparison of the structure of the 7th generation IGBT and the previous generation chip

Thanks to the new chip technology, compared with the previous generation RC-IGBT, under the same chip size, the on-voltage drop of the new RC-IGBT is reduced by about 50%. Figure 4 shows the comparison of the turn-on voltage drop between the new RC-IGBT and the previous generation RC-IGBT.

Figure 4 Comparison of the turn-on voltage drop between the new RC-IGBT and the previous generation RC-IGBT (Tj=25°C and VGE=15V)

Compared with other DIPIPMTM products, the performance of the new surface mount IPM has been optimized and can work at a higher PWM carrier frequency to meet the needs of household appliances such as fans and blowers. Figure 5 shows the relationship curve of the output current, temperature rise and power loss of 1A/600V surface mount IPM products.

Figure 5 1A/600V surface mount IPM power loss and temperature rise versus current curve

(Vcc=300V, fc=20kHz, pf=0.8, M=1, Tj=125 ℃, 3-phase modulation)

3. Package and function

Due to the huge amount of demand, the home appliance market has more stringent cost requirements. The reduction in the size of the inverter control board is one of the effective ways to achieve the cost goal, and the reduction in the package size of the power module will make a huge contribution to achieving this goal.

Figure 6 Comparison of ultra-small DIPIPMTM (left) and surface mount IPM (right) packages

The new surface mount IPM has a very compact package size. Through the use of RC-IGBT, the number of power chips can be reduced to half of the ultra-small DIPIPMTM series. The size of the ultra-small DIPIPMTM and the new surface mount IPM module is as follows Shown in Figure 6.

Some new packaging technologies have been used in the design of new surface mount IPM products, and successfully integrated BSD and other bootstrap circuit components inside the module to further reduce the demand for external components, making it comparable to other similar sizes on the market The products are different.

In addition, some value-added functions have also been designed into the new surface mount IPM products, such as the integrated upper/lower arm interlock function to prevent large current from damaging the power chip during pass-through; integrated BSD chip with 100Ω current limiting resistor , Lower resistance to ensure a more stable upper arm power supply; temperature signal analog output function (VOT) adopts laser trimming technology, through the built-in control LVIC high-precision temperature conversion circuit to achieve, by monitoring the analog signal of the output voltage, you can Use DIPIPMTM closer to the highest endurable junction temperature. Fig. 7 is the VF-IF curve of BSD, and Fig. 8 is the output characteristic curve of VOT.

Figure 7 VF-IF curve of bootstrap diode

Figure 8 VOT output characteristics of the new surface mount IPM (1A/600V)

4. Electrical characteristics

The main electrical characteristics (inverter part and control part) of the new 1A/600V surface mount IPM are shown in Table 1.

Table 1 1A/600V brand new surface mount type IPM electrical characteristics parameters (If there is no special instructions, all are tested at Tj=25℃)

5 Conclusion

By adopting RC-IGBT power chip technology, Mitsubishi Electric has developed a new series of injection molded surface mount IPM products for white goods applications in pursuit of high reliability and high cost performance. The new module integrates IGBT gate drive IC (HVIC/LVIC) and bootstrap circuit components (BSD, etc.). Compared with the current ultra-small DIPIPMTM products, the package size is reduced by about 50%, which will contribute to energy-saving The establishment of society.