Inverter control modules and reference designs accelerate time- to-market

by Mike Sandyck, Managing Director at CISSOID

The push to electrify mobility requires power system designers to overcome the numerous challenges associated with designing for a market that is notoriously demanding in terms of quality, performance, and reliability.

These challenges encompass issues such as thermal management, hardware integration, software development, and proper control of any power semiconductors; in particular, meeting the stringent gate-drive requirements of wide-bandgap devices such as silicon-carbide (SiC) MOSFETs, which are essential to maximize energy efficiency and, ultimately, maximize the vehicle’s driving range.

Inverter design challenges

Engineers need a quick and easy solution to overcome these technical challenges. Finding a ready-made module that they can use within their system is an attractive option. However, they need to be certain that all their design challenges are answered.

A reference design can offer the perfect opportunity to see how an appropriate solution can be achieved, demonstrating component selection and integration. A good reference design should propose solutions to circuit layout challenges, provide thermal calculations for reliability, integrate peripheral components such as sensors and filters, and include provisions to ensure electromagnetic compatibility meeting applicable industry standards. Portions of the printed circuit board (PCB) in the reference design may be directly re-usable in production modules. Assisted by a good reference design, engineers can then tackle other challenges themselves to productize the total solution.

To further accelerate time-to-market (TTM), CISSOID has used its own proven reference designs to create a series of turnkey SiC Inverter Control Modules (ICMs) dedicated to the E-mobility market. These software-powered SiC ICMshelp engineers create functionally safe, robust, and modular E-motor drives. The modules make the engineering solutions put forward in CISSOID’s reference designs easily accessible as a ready-made, ready-to-use solution.

Developers can choose from a series of modules for powering and controlling high voltage SiC traction inverters with battery voltages up to 850V at output powers up to 350kW and peak efficiency in excess of 99%.

These Inverter Control Modules bring together CISSOID’s 3-phase 1200V/340A-550A SiC MOSFET Intelligent Power Modules (IPMs) with a new control board. This board is based on an OLEA T222 Field Programmable Control Unit(FPCU), supplied in partnership with Silicon Mobility.

Additionally, Silicon Mobility’s OLEA APP INVERTER application software is integrated to ensure precise control, optimum electrical performance, and high reliability. This software implements advanced motor control algorithms, including Field Oriented Control (FOC) and Flux Weakening (FW), which help to maintain efficiency at high speeds.

Software integration

When designing a power module, the inverter-control software always has a critical impact on application performance. The fast-switching speeds of the power semiconductors, particularly at the elevated frequencies applicable to SiC devices, can create EMC issues that are often difficult to cure and can require in-depth understanding of motor-drive design.

The software CISSOID selected for this series of ICMs solves these EMC issues at source by supporting a variety of modulation schemes, such as space vector pulse width modulation (SVPWM). SVPWM simplifies the computation of the three-phase output voltage to the motor required to lower harmonic distortion and reduce torque ripple. There is also support for digital PWM (DPWM); a concept that allows simultaneous control of multiple inverter switching parameters to optimize key performance criteria, including efficiency, reliability, and dynamic response, as well as EMC.

In addition, the OLEA APP INVERTER software incorporates features to minimize voltage ripple and handles dead time compensation. It’s capable of managing high-speed control loops operating at switching frequencies up to 100kHz.

Based on CISSOID’s proven SiC-MOSFET three-phase power modules, this portfolio of turnkey ICMs—named the CXT-ICM3SA series—enables engineers to quickly build high-speed motor drives that deliver very high efficiency. These SiC power modules have demonstrated extremely low losses and high-temperature operating capability, with dI/dt and dV/dt immunity and high common-mode noise immunity, thereby relieving designers of these concerns. The optimized gate-driver ensures fast rise and fall times, high peak current capability, and low output impedance, and also takes care of electrical and thermal protection.

The ultra-fast real-time FPCU is an application-specific processor dedicated to e-motor control, capable of high switching frequencies and with onboard programmable hardware, enabling faster system response time to critical events while off-loading the processor cores and enhancing functional safety. Both the FPCU and the control software are ISO-26262 ASIL C/D certified and AUTOSAR 4.3 compliant.

Completing the design

CISSOID helps users of these modules to further accelerate time-to-market by providing the complete SiC inverter reference design that includes key peripheral elements such as current sensors, a high-performance DC-Link capacitor, and EMI filter. This allows engineers to quickly begin motor bench testing of the ICM. Both the ICM and the reference design can be obtained from CISSOID, together with the motor control software and on-site technical support.