With an increasing number of electric vehicles on the roads, the construction of charging stations is progressing rapidly. Faster charging speeds have become a key focus of charging station development.
Well-functioning and efficient chargers are crucial for the active formation of charging infrastructure. However, faster charging speeds also generate higher levels of heat, posing challenges to the safety of the charging process. In this article, learn more about the development of electric vehicle charging technology and the importance of cooling systems for heat dissipation during charging, along with thermal management solutions for your design.
Next-generation thermal management technologies for electric vehicle charging
As electric vehicles become a primary mode of transportation, battery range and even faster charging speeds will become integral components of global economic viability. The improvement of these electric vehicle charging systems requires advancements in multiple areas of technology, including thermal management.
With the growing demand for faster chargers, various changes are taking place in implementation methods. One notable change is the shift towards direct current (DC) chargers, which might sound confusing since all battery systems operate on DC. However, the crucial distinction lies in where the power conversion from alternating current (AC) to DC occurs. In typical residential applications, the most common approach involves conventional AC chargers used for communication, filtering, and controlling the flow of AC power to the vehicle, after which the onboard DC charger rectifies the power and charges the battery. In contrast, DC chargers rectify the power before transmitting it as high-voltage DC to the vehicle. One significant advantage of DC chargers is the ability to eliminate many weight and size constraints by relocating power conditioning hardware from the electric vehicle to an external structure.
With the elimination of weight and size constraints, DC chargers can easily integrate more components, thereby enhancing current throughput and operating voltage. These chargers utilize cutting-edge semiconductor devices, filters, and power resistors for power rectification, all of which generate significant amounts of heat. While filters and resistors contribute notable amounts of heat, the primary source of heat in electric vehicle charging systems is the Insulated Gate Bipolar Transistor (IGBT), a semiconductor device widely used over the past few decades. This powerful device has brought many opportunities to the charging domain, but adequately cooling it remains a significant challenge.
IGBTs are essentially a cross between a FET and a BJT, capable of withstanding high voltages, low on-resistance, fast switching speeds, and remarkable heat tolerance, making them well-suited for high-power applications like electric vehicle chargers. Because IGBTs serve as rectifiers or inverters in these charging circuits, they switch frequently, generating substantial heat. The thermal challenge today is that the heat dissipation requirement for IGBTs has increased from 1.2 kW three decades ago to over 12.5 kW today, a more than tenfold increase, and this demand is expected to continue rising.
There are two factors that contribute to the cooling of IGBTs. First, the surface area of IGBTs is approximately twice that of a CPU. Second, they can operate at higher temperatures, with an operating temperature of 170°C compared to modern CPUs, which typically operate at around 105°C. However, the most direct and reliable thermal management solution is a combination of heat sinks and forced ventilation.
The thermal resistance within semiconductor devices like IGBTs is typically very low, while the thermal resistance between the device and surrounding air is relatively high. Adding a heat sink greatly increases the surface area available for dissipating heat into the surrounding air, reducing thermal resistance. Furthermore, moving air over the heat sink further enhances its efficiency. The advantage of this simple cooling system is that, when installed correctly, passive heat sinks will never fail, and fans are a mature and highly refined technology, known for their reliability.
Cooling system component and thermal monitoring placement techniques
An essential component of any cooling system is how components are placed to optimize airflow and maximize heat dissipation. Insufficient spacing between components can restrict airflow and limit the size of available heat sinks. Therefore, critical heat-generating components should be strategically placed throughout the system to facilitate effective overall cooling.
While careful placement of heat-generating components is necessary, the placement of thermal sensors is equally important. In large systems like DC electric vehicle chargers, a control system used to monitor temperature levels in real-time can enable active thermal management. Automatically adjusting cooling mechanisms based on temperature readings can optimize performance and prevent overheating by limiting current output or adjusting fan speeds. However, these automatic adjustments depend on the quality of input data. If temperature sensors are inaccurately placed, the system's response will correspondingly be inaccurate.
Electric vehicle charging stations are typically installed outdoors, exposed to various environmental conditions. Designing weatherproof enclosures with adequate ventilation to withstand rain and extreme temperatures is crucial for maintaining optimal thermal conditions. The design of airflow paths and vents must prevent water ingress while not restricting airflow.
One of the most concerning external factors is the solar heat generated by sunlight striking the charger enclosure, which can significantly increase internal temperatures. While this is a valid concern, the most effective solutions often involve simple yet direct approaches. Using carefully designed shading devices and ensuring sufficient airflow between the shading device and the charging unit can significantly reduce the environmental temperature around the charger.
DC fans and centrifugal blowers with versatile options and custom features
Same Sky offers a diverse range of DC fans and centrifugal blowers tailored for various cooling needs. Their lineup includes axial fans and centrifugal blowers with frame sizes ranging from 20 to 172 mm and airflow ranging from 0.33 to 382 CFM. These DC fans from Same Sky come standard with automatic restart protection and utilize ball bearings, sleeve bearings, or Same Sky's advanced omniCOOL™ system construction. They also come with various options and customization features, making them ideal forced-air cooling solutions for heat dissipation in applications.
The DC axial fans from Same Sky are rated for 5, 12, 24, and 48 Vdc and offer options for tachometer signals, rotation detector, and PWM control signals. They can achieve speeds of up to 25,000 RPM and are available in models with IP68 protection ratings, suitable for harsh environments.
Same Sky offers centrifugal blowers in frame sizes ranging from 35 to 120 mm. These blowers feature ball bearing, sleeve bearing, or omniCOOL™ system construction, with rated voltages of 5, 12, and 24 Vdc. They come with automatic restart protection and provide an airflow range of 0.57 to 44.2 CFM, with various speed options up to 20000 RPM, making them ideal for high-back pressure applications.
You can visit Same Sky's website through Arrow Electronics to find the blowers and fans that suit your needs.
The best heat sink for natural convection or forced-air cooling systems
Same Sky offers a range of heat sinks suitable for board-level and ball grid array (BGA) designs. Their aluminum and copper heat sinks are compatible with TO-218, TO-220, TO-252, and TO-263 transistor packages, as well as BGA packages. These heat sinks conveniently measure thermal resistance under four conditions, helping you easily select the best heat sink for natural convection or forced-air cooling systems.
Same Sky's heat sink types include BGA heat sinks and board-level heat sinks. Their BGA heat sinks are compatible with BGA devices, made from aluminum or copper, and are available with a black anodized or clean finish, with adhesive or PCB mounting options. Same Sky's BGA heat sinks support a variety of sizes ranging from 8.5 x 8.5 mm to 69.7 x 69.7 mm, with heights from 5 to 25 mm. Measured under four thermal resistance conditions, Same Sky's BGA heat sinks have power dissipation ratings ranging from 1.92 to 21.74 W at 75°C.
Same Sky's board-level heat sinks are designed with various standard extrusions and stampings, compatible with TO-218, TO-220, TO-252, and TO-263 transistor packages. These heat sinks are made from aluminum or copper and feature black anodized, blue anodized, or tin-plated material finishes. They support a range of standard shapes and sizes from 8 mm to 70 mm, as well as profiles from 4 mm to 45 mm.
The board-level heat sinks from Same Sky can be further categorized into extruded heat sinks and stamped heat sinks. Same Sky's extruded heat sinks offer aluminum fin structures with larger surface areas to enhance heat dissipation in high-power applications. When measured under four thermal resistance conditions, these extruded heat sinks have power dissipation ratings ranging from 1.93 to 16.7 W at 75°C. The extruded heat sinks from Same Sky are made from aluminum and feature a black or blue anodized finish, compatible with TO-218 and TO-220 transistor packages.
Same Sky's stamped heat sinks are made from aluminum or copper and feature black anodized or tin-plated material finishes, making them ideal for low-power PCB cooling applications. These stamped heat sinks support various transistor packages with dimensions ranging from 8 to 50.8 mm in width and 4 to 25.4 mm in height. When measured under four thermal resistance conditions, these heat sinks have power dissipation ratings ranging from 2.1 to 10.29 W at 75°C.
You can visit the website of Arrow Electronics to search for Same Sky's heat sinks that meet your requirements.
Conclusion
As the number of electric vehicles and chargers continues to grow, the technologies they rely on will also evolve and improve. Considering the potential increase in charging power and capacity, it's essential to ensure that thermal management systems can adapt to changing demands over time. The rapid growth in power density of IGBTs used in electric vehicle chargers presents unique challenges for thermal management. The requirements for effectively and safely manufacturing these chargers will become increasingly stringent, demanding higher levels of thermal management than ever before. Same Sky offers a diverse range of thermal management components along with industry-leading thermal design services to assist customers with their needs at any time!