Strategic Partnership Yields SiC Inverter Reference Design
Cissoid and Silicon Mobility are expanding their partnership with a collaborative silicon carbide inverter reference design for electric vehicle motor drives.
Recently announced at the Applied Power Electronics Conference (APEC) 2023, Cissoid and Silicon Mobility are introducing a comprehensive silicon carbide (SiC) inverter reference design for electric vehicle (EV) and other electric motor drive applications up to 350 kW/850 V.
The new reference platform will incorporate Cissoid’s high voltage, 3-phase (1200 V/340 A-550 A) SiC Intelligent Power Module with Silicon Mobility’s OLEA T222 FPCU (Field Programmable Control Unit) and advanced motor control algorithms to form a complete, and efficient, high voltage electric motor inverter.
As part of the joint reference platform program, Cissoid will also serve as distributor for Silicon Mobility’s OLEA App Inverter software, designed to assist customers with their electric drivetrain systems integration work.
Cissoid and Silicon Mobility SiC inverter reference platform. Image used courtesy of Cissoid
SiC Power Modules
Cissoid’s power modules are constructed using the company’s SiC power FET and gate driver technologies. Each power module incorporates six power FETs in three half-bridge configurations to support three-phase (U, V, and W motor phases) power inverter applications. Along with the SiC power FETs, the modules also integrate the isolated FET gate drive circuitry to simplify system design, improve circuit performance and reduce design size.
Leveraging the low on-resistances, fast switching speeds, and high withstand voltages offered by wide bandgap silicon carbide, Cissoid’s portfolio of intelligent power modules support load currents ranging from 340 A to 550 A at voltages as high as 1200 V and sub 3 mΩ on-resistances (RDSON).
External PWM pins accept 5 V logic signals from the external system controller (Silicon Mobility) to control the FET operation through the isolated gate drive circuitry. An external 18 V supply (VCC) provides the voltages needed to drive the wide bandgap SiC FETs through their on/off sequencing.
3-phase, 1200 V SiC MOSFET Intelligent Power Module. Image used courtesy of Cissoid
Each power phase within the module has an onboard, transformer-isolated, and regulated flyback DC-DC converter that generates the positive and negative supply voltages (from the external 18 V gate drive supply) needed to drive the FETs.
Flyback DC-DC converter generates gate drive voltages from VCC. Image used courtesy of Cissoid
The reference platform also incorporates current sensors, EMI filtering, and DC link capacitors sourced through partner Advanced Conversion Inc.
Liquid cooling is used to help with thermal management.
Controller Board and Software
Silicon Mobility’s OLEA T222 FPCU controller chip and software algorithms are used to control the sequencing of the power module SiC FETs to generate the three-phase motor drive currents. The reference design uses Space Vector PWM modulation.
The control system can accommodate many e-motor types, including ASM, PMSM, and WRSM, and has a configurable number of pole pairs.
OLEA inverter motor controller with software. Image used courtesy of Silicon Mobility
Advantages of Reference Platforms
When designing a complex platform like an EV traction inverter, numerous circuit structures and design parameters must be considered. Reference platforms, like the joint Cissoid and Silicon Mobility effort, remove much of the guesswork for design engineers by offering a turnkey solution that incorporates all of the needed software and hardware into a complete design. This eliminates design risk, reduces development time, and can improve the system's performance.
According to Cissoid CEO Dave Hutton, customers have historically had two options for high-power inverter designs: develop all of the hardware internally and integrate third-party software or purchase an off-the-shelf inverter that might not be configurable to the specific application.
The Cissoid and Silicon Mobility inverter reference platform combines benefits from both options, allowing system designers to leverage a proven and tested hardware/software integration that leaves room for customization.
