Ingredients for efficient powertrain electrification

Source:EE Times Aisa
2017/06/09
PV:194

In this paper, Infineon Technologies shows that 'full-featured' gate drivers and high performance rotor positon sensor system ease drivetrain electrification for hybrid and electric vehicles.

Drivetrain electrification calls for high-performance semiconductors designed to automotive quality standards. Expertise in both power semiconductors and automotive electronics is thus essential to successfully serve the emerging hybrid and electric vehicle (H/EV) market. Infineon provides all the ingredients necessary to design efficient H/EV systems.

Key parts of an H/EV implementation are the main inverter, DC/DC converter, auxiliary inverters/converters, on-board charger and battery management. Highly reliable semiconductors like power modules, microcontroller, drivers, sensors, etc. (figure 1) have to support a wide range of inverter power classes, enabling compact and cost-efficient system designs offering high energy efficiency. This design goal is for example supported by the power modules of the HybridPACK family, enabling solutions across all power classes for HEV and EV (from 10kW to 150kW). The EiceDRIVER gate driver products offer the perfect feature set to drive and control the IGBTs. The family includes single and dual channel automotive IGBT gate drivers providing galvanic isolation and bidirectional signal transmission. High-performance 32bit microcontrollers like the AURIX Family are the perfect complement to the product portfolio for energy-efficient electric drivetrains, while position sensors enable closed-loop feedback of motor position for complex control like Field Oriented Control (FOC).

 

201706_EETA_HEV_components_Infineon_Fig1_crFigure 1: Key parts of an (H)EV implementation - power modules, high performance microcontrollers and drivers.  


Optimized gate drivers

The latest generation of EiceDRIVER solutions play a valuable role in enabling cost effective inverter designs and facilitating ASIL system certification for (H)EV applications.

Target applications for the 1EDI2001AS and the 1EDI2002AS are (H)EV inverters using 400V, 600V and 1200V IGBTs. Both drivers provide galvanic isolation, bi-directional signal transmission, active short-circuit support and optimized IGBT switching capabilities. These products have a standard SPI for control and diagnosis, with transmission speed up to 2Mbd. Safety-related functions include over-current protection, run time monitoring of all power supplies, oscillators, gate signals and output stage. System-level diagnosis including error injection as well as weak turn-on is also supported.

An additional member of the EiceDRIVER family is the 1EDI2010AS. This product has an integrated ADC on the secondary side that can be used for evaluating DC-link voltage, temperature over an NTC or an on-IGBT temperature diode. The data is available over SPI.

The 1EBN1001AE is a single-channel IGBT booster, compatible with the1EDI20xxAS family. It is based on high-performance bipolar technology and replaces buffer stages based on discrete devices. Because of its thermally optimized exposed pad package, it is able to drive and sink peak currents up to 15A. This makes it suitable for most inverter systems in automotive applications. It features support for active short-circuits and for active clamping. It is supplied in an exposed pad PG-DSO-14 package.

Together the gate drivers and the booster can save significant PCB area of up to 20% in the sub-system and also eliminate up to 60 discrete components needed in today’s solutions.

Rotor position sensor system for brushless motor control

Brushless motors are frequently used in (H)EV applications. These highly efficient motors rely on fast and accurate rotor position sensors for commutation, as these sensor parameters have a significant impact on startup behavior, dynamics, torque ripple and efficiency.

There are different principles to detect the rotor position: electromechanical resolver (inductive) and magnetic. Resolver based sensor systems have some limitations (analogue output, complex circuit, high system costs, space constraints, sensitivity to stray fields and positioning tolerances, etc.). The 32bit AURIX microcontroller family, with its delta-sigma ADC to perform carrier signal generation and software-based encoding, already helps to save external resolver IC and hence system cost by about 20%.

On the other hand, magneto resistant (xMR) angle sensors with AMR (Anisotropic-Magneto-Resistance) or GMR (Giant-Magneto-Resistance) technology offers high precision accuracy, combined with low sensitivity against position tolerances.

 

201706_EETA_SensorPlacement_Infineon_Fig2_cr


 

Figure 2: The integration of the sensor system into the shaft end ensures robustness against magnetic stray fields and saves constructed space.

To implement a xMR sensor system the influence of magnetic stray fields from interfering sources like power electronics, inductivities, capacities, cables and the stray field generated by motor have to be taken into account. Infineon recently has shown, that an integration of the complete sensor system inside the shaft end will comply with all requirements. The shaft that surrounds the magnetic circuit acts as a perfect shielding against magnetic disturbance fields. Additional magnetic shielding measures, which would drastically increase system costs, can be avoided. The magnetic circuit will be completely integrated into the shaft end as well as most parts of the sensor module (figure 2). Only small constructed space which is needed for mounting of the sensor module had to be considered outside the shaft. With respect to accuracy the system evaluation results are very promising: The maximum measured angle error (figure 3) of the tested GMR sensor was <0.3°, while the related parameter for the AMR sensor was <0.14°. This high precision was stable over a large safe operating area, while misplacements in the mm range still enabled high precision angle detections.

 

201706_EETA_SensorMeasurements_Infineon_Fig3_cr

Figure 3: Best-in-class accuracy independent of positioning tolerances for the TLE5309D sensor, providing an AMR chip and a GMR chip in one package.  

In many cases the rotor positon sensor plays a relevant role in functional safety concepts according to ISO26262. Infineon offers angle sensors in a dual-sensor package that allows the integration of two redundant sensors in the place of one. The TLE5309D, in particular, meets the highest functional safety requirements by using a combination of AMR and GMR technology, which not just offers redundancy, but also integrated diversity in a single product.



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