PFC MOSFET for EV Chargers
The active PFC circuit controls the current by turning the MOSFET on and off, synchronizing the power supply voltage and phase, and bringing the input current waveform closer to a sine wave. The power factor correction circuit is mostly after filtering and rectifying the AC power, then carrying out the control adjustment of power factor correction. More and more people have begun to pay attention to new topologies in recent years to reduce losses and improve the efficiency of the whole PFC circuit. The bridgeless PFC topology has received extensive attention among these topologies due to its simple structure, reliability, and fewer peripheral devices in the control circuit. This design saves around 66% losses over a comparable IGBT-based design.
Introduction
The performance of batteries in Electric Vehicles (EVs) is highly dependent on the battery design and the battery performance during charging/discharging. Onboard chargers are built into a vehicle with charging and driver hardware circuits. In the traditional onboard charging system, the AC power is obtained from the grid side, rectified by an uncontrolled rectifier bridge, and fed to the battery. This method lowers the power factor in the circuit and increases the harmonic content of the current in the circuit. The active PFC circuit controls the current by turning the MOSFET on and off, synchronizes the power supply voltage and phase, and brings the input current waveform closer to a sine wave. The power factor correction circuit is mostly after filtering and rectifying the AC power, then carrying out the control adjustment of power factor correction. In recent years, an increasing number of people have started to pay attention to new topologies to lower losses and increase the overall PFC circuit's efficiency. Because of its straightforward design, dependability, and reduced number of peripheral devices in the control circuit, the bridgeless PFC topology has drawn the most attention of any of these topologies. Compared to an equivalent IGBT-based design, a SiC MOSFET-based design reduces losses by about 66%. This boost in efficiency allows designers to either increase power in a design with the same volume or decrease volume in a PFC design if the goal is to deliver the same power.
What is PFC?
The degree of phase divergence between the AC voltage and AC is known as the power factor. Onboard EV chargers with high-frequency switching components cause harmonics to grow, significantly impacting the power factor. Any circuit's power factor ranges from 0 to 1. Therefore, power loss and efficiency both increase with decreasing power factor. To eliminate harmonics or get a power factor closer to 1.0, a power supply circuit can add a power factor correction (PFC) circuit. To reduce the overall apparent power consumption, a power factor correction (PFC) circuit purposefully bends the input current to be in phase with the instantaneous line voltage.
Example of an input current waveform for passive PFC. (Source)
Design Characteristics
Design for (Source)
1. A SiC-Based LLC converter:
The LLC (Inductor- Inductor Capacitor) based converter can work in the closeness of resonant frequency and more efficiencies above the maximum collection of battery store voltage utilized in PEV, so the DC-link voltage can be actively adjusted. The unity power factor is achieved along with low THD in a SEPIC PFE converter and an increase in overall efficiency of the charger of the rated load to full load.
2. Two-phase Interleaved CCM PFC Design:
The input current of harmonic free is realized by pulse width modulation (PWM) control of the cuk converter utilizing a two-loop design, neglecting any battery charging risk by use of LLC controller, to minimize turn-off losses & switching losses, less LLC transformer flux density and then to increase efficiency. The output current is limited. During the CCM, a battery current is controlled over current protection, maximizing the converter efficiency,
Market Players in PFC Staged
Texas Instruments: Single-phase UCC2818A-Q1 controller or two-phase interleaved UCC28070-Q1 controllers operating in CCM PFC mode are developed by Texas Instruments. In addition, TIDA-01604 presents a 6.6-kW totem pole (TTPL) bridgeless power factor correction (PFC) solution for the Onboard Charger.
Infineon: 650 V CoolMOS™ CFD7A Automotive Power MOSFET TO-247 and 1200V CoolSiC™ MOSFETs have been developed by Infineon for current and future HV/LV DC-DC applications in hybrid and electric vehicles having PFC totem Pole topology.
Toshiba: The TB6819AFG PFC control IC from Toshiba raises the power factor by lowering the current harmonic content. Stabilizes the input from AC. Utilizing 2nd Generation SiC MOSFETs, Toshiba's reference design of a PFC circuit for 3-phase, 400 V AC inputs shows how to increase power supply efficiency for uses like electric vehicle (EV) charging stations.
NXP Semiconductors: The TEA1716 is a multi-chip integrated circuit that combines a controller for a half-bridge resonant converter (HBC) with a power factor corrector (PFC) controller. It performs the drive function for the two discrete power MOSFETs in a resonant half-bridge configuration and the discrete MOSFET in an up-converter. The TEA1716 makes it simple to design power supplies that range in output from 90 W to 500 W and are dependable and highly efficient.
On Semiconductors: On Semiconductor's AND9957/D On Board Charger system is based on silicon carbide MOSFET.
ST Microelectronics: The reference design in STDES-7KWOBC onboard charger (OBC) developed by ST Microelectronics embeds two sections: an interleaved totem pole PFC with SiC and a dual galvanic isolated full bridge LLC DC-DC ZVS resonant converter, based on MDmesh DM6 super-junction power MOSFETs.
Application & Features
The key to reducing loss for higher efficiency is to replace the power switch from a conventional IGBT to a SiC MOSFET. It is already widely known that SiC power devices are an advantageous option in high-power applications. Still, to take advantage of their excellent properties, it is necessary to understand the characteristics of SiC power devices. In this respect, the reference design provides standard conditions and helps facilitate the smooth and quick development of the design.
PFC Staged Power Mosfets used for Onboard Charging of EVS must meet the following requirements.
Conclusion
The power exchange between the grid and EV and vice-versa boosts the grid's reliability, stability, and efficiency and expands the overall power generation capacity. Based on the review, it is possible to recommend that a standard power electronics converter and Uni/Bidirectional Charger /discharger system be planned for improved quality-based EVs.
References
Author
Dr. Shalini Mishra
Associate Consultant at Lumenci
Shalini works as an Associate Consultant at Lumenci. Her area of interest is Power electronics and Electrical Drives and condition monitoring of Transformer Insulation. She holds a PhD and a master’s degree from IIT(ISM) Dhanbad.