Introducing On-board Film Capacitors for EV Chargers (OBC)
2022-10-21
In recent years, as people have become more aware of environmental responsiveness, automobile manufacturers are required to work harder on exhaust gas regulations. According to this situation, many automobile manufacturers are shifting their development focus from conventional vehicles with an internal combustion engine to electric vehicles (EVs), and the EV-related market is expanding year by year. However, there are many challenges to overcome for EVs to become commonplace, such as mileage, charging infrastructure, and safety. This article will introduce film capacitors for the on-board charger (OBC), an EV charger developed by Panasonic to realize next-generation EVs as an example.
Product lineup for OBCs
Increasing the capacity of the battery, which is the most important component for extending the mileage of EVs, is a key factor, which will require the design of higher output EV chargers. In order to meet such need, Panasonic has a lineup of ECQUA, ECWFG, and EZPV series on-board film capacitors that feature compatibility with high current, high reliability, and high safety, contributing to the design and development of high-power OBCs.
Panasonic's technology to achieve high reliability
We have developed parts that are ideal for automotive applications that require high reliability by ensuring high-dimensional humidity resistance and thermal shock resistance through our proprietary enclosure sealing technology and aluminum vapor deposition, and by complying with the AEC-Q200.
Figures 2 and 3 show the results of the moisture resistance load test (85°C, 85%, 240 VAC) and the high-frequency step-up load test after humidity resistance stress application (60°C, 95%, 275 VAC, 1000 h) on the combination of high humidity resistance enclosure and aluminum vapor deposition (blue line) as well as the combination of general-purpose packaging and Zn deposition (red line).
The results of the moisture resistance load test indicate that the capacitance decreases due to oxidation of Zn deposition and tan δ (resistance component) is also high in the combination of conventional general-purpose packaging and Zn deposition. However, the combination of high humidity resistance enclosure and aluminum vapor deposition is highly resistant to moisture and almost no deterioration of characteristics is seen.
In addition, when the capacitor surface temperature rise is compared in a high-frequency step-up load test after humidity resistance stress application, the temperature rise is intense due to significant tan δ deterioration caused by humidity resistance stress, which tends to lead to short circuiting in the combination of conventional general-purpose packaging and Zn deposition. However, in the combination of high humidity resistance enclosure and aluminum vapor deposition, defects are unlikely to occur because temperature rise is small under high-frequency load.
Panasonic's technology to achieve high safety
In order to ensure the safety of equipment, it is required to take measures towards design for high end-of-life safety of each part. In response to such demand, Panasonic's film capacitors are equipped with a security mechanism（fuse function）
Normally, if a dielectric breakdown occurs somewhere inside the capacitor, it will lead to total destruction. However, Panasonic's film capacitors are divided into many capacitor cells using high-definition pattern technology. Therefore, even if a dielectric breakdown occurs, the relevant cell is cut off（fuse function）so that the destruction does not progress to the entire capacitor. By optimally placing the fuse section on the deposition film so that the circuit is opened in its failure mode, ignition or smoke accidents caused by the short circuit mode are prevented, contributing to high safety of the product set (Fig. 4).
Summary
This article introduced the high current, high reliability, and high safety film capacitor technology that contributes to the higher output and safety of EV chargers. In the environmentally friendly vehicle market, including EVs, which is expected to keep growing, there will be an even greater demand for higher performance, high reliability, and safety of individual components. Panasonic Industry will contribute to further improvement of equipment performance through a broad product lineup and the development of highly functional devices.
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