E-mobilty – main inverter market trends

Worldwide, the hybrid and electric vehicle (xEV) market is growing exponentially, showing the highest growth rates in the automotive sector for decades. This market trend is mainly driven by legislation on the reduction of emissions. Many upcoming standards will not penalize CO2 emissions of individual vehicles, but that of the entire fleet sold by an OEM. The European Union for example has set a limit of 95 g/km fleet average from 2021 and will reduce it to 59 g/km by 2030. As a result, car manufacturers need to electrify a wide range of vehicles: from small city cars to large long-range sedans and SUVs. OEMs and Tier1-suppliers need scalable and cost-efficient solutions to meet those ambitious targets.

Infineon supports system suppliers with the widest product portfolio of power semiconductor solutions for xEV main inverters in the industry – ranging from chips to discrete solutions and entire modules. At the heart of Infineon’s xEV module portfolio stands the HybridPACK™ Drive. The lead product was introduced in 2017 and is now complemented with an entire product family (Fig. 1 & 2). This power module family provides power scalability between 100 kW and 175 kW and an easy design-in concept to support Tier 1 suppliers and automotive OEMs in the development of a cost-effective platform approach for main inverters. Adding to the spectrum, Infineon also introduced a 1200 V Silicon IGBT chip in this product family, enabling higher vehicle working voltages necessary for fast charging purposes with battery voltages of 700 V or more. The demanding requirements of Commercial, Construction and Agriculture vehicle (CAV) applications like buses and trucks can also be met. In a next step, the family will also implement Silicon Carbide chip technology, which achieves a doubled power density compared to Si based devices.

The key requirements for xeV main inverters are

  • High efficiency
  • High power density and current capability
  • Long lifetime and reliability
  • competitive cost-performance ratio

To meet those requirements, Infineon introduced the first HybridPACK Drive power module with the EDT2 IGBT-chip generation in 2017. The key improvements compared with previous power module generations are a reduction of power losses, higher current capability and ease of mounting. The first two aspects are mainly achieved by the new IGBT chip generation in the module. The EDT2 technology sets benchmarks in terms of current density combined with short circuit ruggedness and increased blocking voltage and ensures reliable inverter operation under harsh environmental conditions. The EDT2 chips also reduce power losses at light loads. This significantly improves the system efficiency in a real driving cycle. The module comes with high clearance and creepage distances. This makes the new module family well suited for increased system working voltages.

To simplify the customer’s assembly process the power modules have mechanical guiding elements and press-fit pins for the signal terminals (Fig. 1). Thus time-consuming selective solder processes can be avoided, which results in cost savings and improved reliability on system level. As the pins are not integrated into the power module housing, a flexible control pin adjustment is granted for an optimized circuitry on the DCB. This flexibility also enables functional upgrades like sensor integration for future designs.

Infineon, HybridPACK Drive family

Fig. 1:Typical module appearance of the HybridPACK Drive family. All Si IGBT family members have the same top side appearance.

Two connector tab types are offered, which enable either a fast welding process or a classic screw connection to the system. A long tab version is also in production to implement phase current sensors directly on the power tabs.

Technical features

With increased market demand for electric vehicles leading to the necessity to build-up a new energy vehicle fleet with all kinds of performances, the HybridPACK Drive module is a very good match to enable highest flexibility for system designers.

Different power classes are achieved by an adaption of the cooling system (Fig. 2). The baseplate of the module is connected with the cooler of the inverter. Changing the design of the baseplate influences the capability of thermal dissipation of the module (Table).

Different power classes

Fig. 2:Different power classes are realized by changing the cooling performance and the chip technology.

technical features of HybridPACK

Table:Main technical features of HybridPACK™ Drive variants.

The HybridPACK Drive Flat offers the lowest performance in the product family by using a flat baseplate without any structure. Thus, customers who have already implemented the existing Pin-Fin module in their system benefit from reusing the same footprint for lower current densities.

For increased power the Wave module establishes a Ribbon Bond baseplate structure for direct cooling. It closes the performance gap between the Flat version and the Pin-Fin module.

On the upper end of the family, the Performance module is equipped with the already well-known Pin-Fin baseplate and shows the highest cooling performance. A dedicated ceramic material enables higher current capabilities and extends the power class portfolio to 175 kW.

All three new variants use the same EDT2 chipset as the first launched variant. The EDT2 technology has been designed for automotive power based on the micropattern trench cell concept (Fig. 3) and was developed to achieve a high performance as well as a high robustness with good controllability and short circuit robustness.

EDT2 IGBT

Fig. 3:Vertical cell geometry structure of non-punch-trough, Trenchstop, micropattern trench concept and EDT2 IGBT (from left to right).

Compared to prior IGBT generations the EDT2 implements a new cell structure, which reduces the gate charge and increases the current density. At the same time, the switching softness and good thermal short circuit capability in the EDT2 remains. Due to an optimized field-stop structure, the die thickness and base material resistivity can remain and the collector-emitter voltage can be increased by 100V to 750 V. The trenchstop concept (Fig. 3) and thin wafer technology were already implemented in the earlier chip generation, leading to significantly improved conduction and switching losses. This technology was benchmark in industrial applications and was qualified for autmotive applications with the rise of electric mobility. Earlier chip generations were based on non-punch through concepts.

The micropattern trench concept of the EDT2 allows an optimization of the carrier profile. This allows a reduction of charge carriers within the drift zone, which have to be removed during the turn-off phase (tail current) in order to minimize total power losses. These two measures allow a significant reduction in conduction losses (Vcesat) and turn-off switching losses (Eoff). The increase in the blocking voltage provides more design margin at turn-off when the chip is exposed to a voltage spike caused by the current drop di/dt and the system inductance. The chip also has a lower turn-off loss at high bus voltages.

Fig. 4 depicts a turn-off characteristic of the trenchstop IGBT3 and the microtrench pattern like EDT2 IGBT in the same module with a gate driver circuit at Vdc=400 V and Tvj=25°C. The gate-emitter (Vge)-curve clearly shows that the Miller plateau is significantly reduced resulting in a faster switching event and significantly lower turn-off energy per switching event. This enables highly efficient inverter designs for normal operation. Despite the short Miller plateau, the EDT2 IGBT is easy to control. Especially at extremely high current situations like overcurrents and short circuit, the EDT2 is not switching faster than the IGBT3, which makes such extreme situations easy to handle and leads to high system reliability.

trenchstop IGBT3

Fig. 4:Comparison of switching behavior of a trenchstop IGBT3 and the micropattern trench like EDT2 IGBT in the same module (Vdc=400 V, Tvj=25°C).

To meet the requirements of high DC-link voltages, i.e. for fast charging applications, the IGBT4 1200 V technology is now available as an alternative variant of the Performance module. It is also based on a Pin-Fin baseplate and performance ceramic but uses a different chipset. With the implementation of IGBT4 dies, which offer best thermal resistance Rth performance compared to the EDT2 HybridPACK Drive variants in the same configuration, 1200 V blocking voltage within the HybridPACK Drive Family is enabled. The square trench cell of the IGBT4 provides a best compromise between low gate charge and a carrier profile for balancing the conduction and turn-off losses. In combination with the substrate resistivity, thickness, fields stop and collector-side p doping the IGBT4 1200V is focused on softness, in particular on smooth switching capabilities for applications with high system inductance currents (Lstray*I). This results in high EMI compatibility and low voltage spikes during turn-off.

The HybridPACK Drive is qualified according to the European qualification guideline for power modules for use in power electronics converter units in motor vehicles. Being part of the ECPE (European Center for Power Electronics) Working Group AQG 324 Infineon works closely with automotive partners. Based on the former German LV 324 (´Qualification of Power Electronics Modules for Use in Motor Vehicle Components - General Requirements, Test Conditions and Tests´) the ECPE Guideline defines a common procedure for characterization of power modules as well as for environmental and lifetime testing of power electronic modules for automotive applications.

Evaluation Kit HybridKIT

Infineon offers the HybridKIT Drive and HybridKIT Drive Sense, which are easy to use evaluation kits for a B6-bridge full xEV main inverter application. The kits support system designers in fast and efficient evaluation of the HybridPACK Drive.

The evaluation kit is equipped with the HybridPACK Drive lead type power module, a gate driver board with latest EiceDriver-technology, a microcontroller logic board with Aurix-microcontroller, preinstalled software, DC-link capacitor and cooler. Designed for the use in a laboratory environment the HybridKIT Drive can drive active and passive loads up to 150 kW for DC voltages up to 500 V. As the devices are intended to be used with a cooler, the system is prepared for fluid cooling and can reach high efficiency values up to 99% even on light load conditions. (Fig. 5)

Infineon_HybridKIT

Fig. 5:Typical appearance of an evaluation kit HybridKIT of the HybridPACK Drive.

For more information, visit www.infineon.com/hybridpack

Maike Müller, product marketing manager for Automotive High Voltage Modules at Infineon Technologies
Tomas Reiter, application engineer for Automotive High Voltage Modules at Infineon Technologies