EliteSiC Solutions for EV Charging
The boom in the EV market has spurred the development of various industries, with EV charger undoubtedly being one of the most incentivized applications. To meet the growing needs of EV, more and faster charging infrastructures need to be established. Simultaneously, as a crucial means to achieve low-carbon goals, EV charging devices need to be designed efficiently.
The trend towards higher power and greater efficiency in charging modules is expected. By adopting suitable power components and topologies, along with robust controllers, we will have more high-power charging stations, addressing range anxiety and reducing carbon emissions.
Figure 1. Difference between On Board Charger and DC EV Charger
Power conversion stages
The DC EV charger consists of a classic power conversion stage of AC-DC and DC-DC. The front end of the DC charger consists of a three-phase Power Factor Correction (PFC) boost stage, it could be implemented in a variety of topologies (two or three level) and uni- or bi-directional. See AND90142 - Demystifying Three Phase Power Factor Correction Topologies to understand three level and example three level PFC circuit. The voltage level from the grid 400 V - 480 V (Three-phase) / 110 V – 240 V (Single-phase) is boosted up to 500 – 1000 V (and targeting higher). A subsequent DC-DC isolated stage converts the bus voltage into the required output voltage. The output voltage aligns with EV battery voltages (typically 400V or 800V) and need to cover the voltage charging profiles. Therefore, the DC-DC output range might swing from 150V up to 1000V. Specific implementations might be optimized for the 400 V or 800 V level.
The overall system efficiency of a DC EV charger is nowadays around 95%, main losses come from power conversion, cable, transformer. In a high-power system, even 1% losses generate massive heat, so improving efficiency is always a target for charger designers.
DC wallbox (charger)
DC wallbox (charger) is considered a replacement for traditional low-power AC chargers installed in places like parking lots, houses, offices, etc. It must be compact, lightweight and cost-effective. The key value of DC wallbox is that it defines the charging power rather than relying on an OBC. (AC charger is a simple system containing electricity meter and communication interfaces, without a high-power conversion stage.) With adoption of DC wallboxes, some manufacturers consider removing the OBC from their future EVs to decrease vehicle cost. However, this would also bring inconveniences as AC chargers can not be used.
Communication
Communication and connectivity are cornerstones of EV Chargers, fulfilling different functions: between stacked modules on the power stage, CAN, PLC, RS485, which depends on charger OEMs. Between vehicle and charger for the charging sequence. CAN or PLC are usually used. External connectivity for payment, service management, maintenance, software upgrades, preferred communication methods are BLE, Wi-Fi, 4G/5G.
Compliance and standard
There are several standards and protocols worldwide that define the requirements for DC charging, such as the IEC-61851 / SAE1772, GB/T, standards and the CHAdeMO, Combined Charging System (CCS) or Tesla Supercharger protocols. IEC 61000-3-2/4 defines the limitations of harmonics in power.
Discrete vs Power module
There are lots of aspects which influence customer‘s decision, but for high-power products, module solution is highly recommended especially when dealing with multiple discrete MOSFET/IGBT in parallel. Module approach will improve aspects such as the long-term performance caused by imbalanced current and heat, switching timing, wiring connections, etc. Read AND9100 – Paralleling of IGBTs to learn more.
Pairing Gate Drive to EliteSiC
“Energy Infrastructure applications like EV charging, energy storage, Uninterruptible Power Systems (UPS), and solar are pushing system power levels to hundreds of kilowatts and even megawatts. These high-power applications employ half bridge, full bridge, and 3-phase topologies duty cycling up to six switches for inverters and BLDC. Depending on the power level and switching speeds, system designers look to various switch technologies, including silicon, IGBTs, and SiC, to best fit application requirements.
While IGBTs offer superior thermal performance vs. silicon solutions in these high-power applications, EliteSiC by onsemi enables both higher switching speeds and high power. onsemi offers a complete portfolio of SiC MOSFETs ranging from 650V to 1700V breakdown voltage, with RDSONs as low as 12mΩ. But, every SiC MOSFET requires the correct Gate Driver to maximize system efficiencies and minimize the total power losses. This easy-to-use table below pairs the correct Gate Driver to each SiC MOSFET”.
| EliteSiC MOSFETs | Gate Driver: 5kVRMS Galvanic Isolation | ||||||
| GI: 3.75kVRMS | GI: 5kVRMS | ||||||
| 1-Channel (source/sink) | 2-Channel (source/sink/matching) | ||||||
| V(BR)DSS: | RDSON (typ): | Package: | 4.5A / 9A | 6.5A / 6.5A | 7A / 7A | 6.5A / 6.5A / 20ns | 4.5A / 9A / 5ns |
| 650V | 12 – 95mΩ | 3-LD, 4-LD, 7-LD, TOLL, PQFN88 | 4NCP(V)51752 30V Output Swing (SOIC-8) |
13NCD(V)5709x 32V Output Swing (SOIC-8) |
123NCD(V)5710x 32V Output Swing (SOIC-16WB) |
NCD(V)575xx 32V Output Swing (SOIC-16WB) |
1NCP(V)5156x 30V Output Swing (SOIC-16WB) |
| 750V | 13.5mΩ | 4-LD | |||||
| 900V | 16 – 60mΩ | 3-LD, 4-LD, 7-LD | |||||
| 1200V | 14 – 160mΩ | 3-LD, 4-LD, 7-LD | |||||
| 1700V | 28 - 960mΩ | 4-LD, 7-LD | |||||
Gate Driver: Peak Source Current / Peak Sink Current / Total Propagation Delay Matching
1 Supports: External Negative Bias Turn Off
2 Supports: Desaturation (Over current) Protection
3 Supports: Active Miller Clamp (Over current) Protection (clamps VGS preventing accidental turn on during intended turn off)
4 Supports: Internal Negative Bias Turn Off.
"V" Supports Automotive Qualification
| Short Description | |
| NCP51752 | 3.7 kV Isolated High Performance SiC Drivers |
| NCD5709x | 5 kV Isolated Single Channel Gate Driver |
| NCD5710x | 16-pin Wide Body Isolated Gate Driver |
| NCD575xx | 5 kV Isolated Dual Channel Gate Driver |
| NCP5156X | 5 kV Isolated High Speed Dual MOS/SiC Drivers |
| NCV51752 | 3.7 kV Isolated High Performance SiC Drivers |
| NCV5709x | 5 kV Isolated Single Channel Gate Driver |
| NCV5710x | 16-pin Wide Body Isolated Gate Driver |
| NCV575x | 5 kV Isolated Dual Channel Gate Driver |
| NCV5156x | 5 kV Isolated High Speed Dual MOS/SiC Drivers |