Why is 48V distributed power architecture redefining automotive power supply? Chat with Vicor engineers!
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Automotive OEMs must meet lower CO2 emissions standards while improving vehicle features and performance to remain competitive. This major challenge is being overcome through vehicle electrification, which is changing the power supply network for pure electric vehicles (EVs), hybrid electric vehicles (HEVs), and internal combustion vehicles (ICVs). The addition of higher voltage batteries such as 48V, 400V, and 800V to meet the increased power demand, in turn, increases the complexity of the power supply architecture and brings new requirements for the size and weight of automotive power converters and regulators for battery charging, power conversion, and power delivery.
Vicor is enabling vehicle electrification with high-density, scalable, modular power delivery solutions close to the power grid. Our components replace bulkier discrete solutions found in many cars today, redefining the power delivery grid while making cars lighter, faster, and with greater range.
Vicor Power Delivery Networks for Charging, Conversion and Distribution
With the deployment of 400V and 800V charging stations, vehicle compatibility with any station requires simple and efficient conversion between the two voltages. The NBM6123 uses a 63 x 23 mm CM-ChiP package and provides 6kW of fixed ratio conversion between 400V and 800V, enabling a high-efficiency, high-density, scalable solution for battery-to-charging station compatibility. The bidirectional capability of the NBM6123 allows the same module to perform buck-boost conversion. In addition, the NBM6123 can also be used to provide 400V power to air conditioners and in-vehicle electronics during 800V charging, thereby minimizing battery balancing circuits.
Converting the car's main high-power high-voltage battery using traditional solutions adds weight and creates a huge demand for space in the car. In addition to the converter itself, a secondary intermediate battery is also required. The BCM6135 module supports the integration of standard 800V and 400V batteries into the 48V power supply network, which can reduce weight and space occupation. In addition, the BCM6135 also provides bidirectional power conversion and fast transient response, without the need for 48V intermediate energy storage. The BCM6135 virtualizes the high-voltage battery, making it look like a 48V battery in the system.
The new 48V power delivery network needs to support legacy 12V loads with higher power demands, new drives, steering, and brake-by-wire high-power systems. As loads increase, providing greater power at 48V requires high-density modules rather than more bulky discrete solutions. Vicor offers several modules for 48V power delivery. These devices include fixed ratio and regulated converter solutions that support 48V and 12V loads. These converters can be deployed in a single housing or throughout the vehicle with a smaller and lighter 48V distribution network. The DCM and PRM modules provide regulated 48V to 12V output and regulated 48V to 48V output, respectively. The NBM provides bidirectional fixed ratio conversion of 48V to 12V or 12V to 48V.
Why 48V technology?
Since we are asking why, let’s talk about the advantages of 48V bus power distribution as a disruptive technology. Some opinions in the industry are summarized as follows:
Increase power and reduce emissions. The increase in power can make the internal combustion engine run more efficiently, helping OEMs meet emission regulations more quickly. Mild hybrid vehicles with start-stop functions have been launched, which can temporarily shut down the engine when coasting, braking or stopping, and then quickly restart to provide partial power. The electric motor of a mild hybrid vehicle is used to supplement the energy of the internal combustion engine and cannot provide power for the vehicle alone.
48V electrical system supporting conventional 12V system
Recover and store energy. The 48V system uses a large-capacity lithium battery and a regenerative braking system. Through regenerative braking or recovery braking, the kinetic energy lost when the car decelerates can be converted into electrical energy and stored in the 48V large-capacity battery. The recovered energy can also be used to support the electrical devices of the internal combustion engine. Regenerative braking can use the stored energy to propel the vehicle forward when changing from parking to accelerating, thereby achieving a faster speed than usual.
· Meet high-power electricity demand. 48V system cars will not have the situation that people complain about when 12V system cars turn off the heating, ventilation and air conditioning (HVAC) power outage. For loads that rely on high current, such as stability control or air conditioning compressors, the 48V system can achieve safety and comfort functions, and is superior in performance and efficiency.
Utilize surplus energy. The stored energy can be used at any time to defrost the windows or heat the seats. Now, more and more OEMs are using new infrared heating panels to directly heat without wasting electricity to heat the rest of the car. However, the challenge of infrared heating panels is that each seat requires about 500 watts of power, which is almost unbearable for the 12V electrical system.
Therefore, the demand for 48V bus power distribution is becoming more and more obvious, but if 48V MHEV wants to solve the problem of automobile electrification in the future, it still needs the help of semiconductor manufacturers at the source of the supply chain.
>> Click here to learn more about Vicor's automotive solutions
In 2022, the prestigious British Touring Car Championship (BTCC) will add a new dimension as it becomes the industry’s first major touring car championship to feature MHEV cars, using the new Delta Motorsport intelligent power-dense battery pack, which eliminates the need for an alternator, saving weight and improving reliability.
BTCC to launch MHEV championship soon
BTCC regulations allow drivers to tactically use motors to improve vehicle performance and increase vehicle acceleration. To this end, Delta Motorsport has designed a new battery pack and related electronics. The new 48V lithium-ion battery pack uses innovative intelligent power management and a high-power density DC-DC converter and voltage regulation system. The battery pack powers the inverter-motor combination and uses the regenerative power it generates, while the high-power density converter can power all circuits and devices in the car. The power density and power management level achieved by this architecture does not require the use of an AC generator system, thereby further reducing weight and improving performance and reliability.
Nick Carpenter, Delta Motorsport's director of engineering, said the system uses a modular power delivery network (PDN) to achieve small size, light weight and high performance. The hybrid system's three-phase brushless motor is connected to the battery through a bidirectional inverter, which delivers battery power to the motor and returns the regenerative power generated by the motor to the battery.
Nick Carpenter: Modular PDN enables small size, light weight and high performance
“During the initial speed-restricted run to the pitlane, the electric motor drives the car in pure electric mode (electric motor only, no combustion engine), and then when the driver demands increased performance during the race, the electric motor drives the car in MHEV mode (together with the combustion engine),” he said.
Let’s take a look at the innovations in battery pack intelligence and management.
Battery Pack and Battery Management System: This controls all battery voltages and ensures that the battery can handle the maximum possible charge and discharge voltages at any time while communicating with the motor-inverter controller. Based on the battery state of charge (SoC), the system continuously calculates and provides updated information to the controller on the amount of current the battery can provide or accept, reducing power demand at low SoC and limiting regeneration at high SoC. The system also monitors the temperature of all available batteries in real time and feeds the results into the available power calculation. In addition, if a problem occurs, it can open the contactor to safely isolate the battery pack.
Control and Power Management
Power network: 48VDC supplies power to four parallel DC-DC converters, which together provide regulated 13.8V power at up to 92 amps (about 1.2 kW). The load is shared by the four converters, although the load can be fully supported with just three converters (i.e., N+1 or aviation-grade redundancy).
Hybrid layout
DC-DC Converter: The power system uses four Vicor DCM3623 isolated regulated DC-DC converter ChiP (converter in package) power modules to provide a regulated 13.8V output from the battery pack at up to 92 amps. Due to its small form factor, the converter is mounted on a micro-perforated cooling plate that extends into direct thermal contact between the battery cells. The battery management system’s data logs and diagnostics record the performance of the DC-DC converter, check for fault conditions, and provide feedback on all accurate current flows in the vehicle.
This modular power component performed well in the initial battery pack testing, without derating and without voltage sag. It is critical that the power network retains the largest volume for the battery cells it supplies, rather than the power components themselves. Therefore, this power network has shown great advantages. The scalability and easy parallel connection of DCM modules realizes a modular power architecture, allowing Delta to achieve the required small-size DC-DC PDN customization without sacrificing power.
Delta also uses a small 60W isolated converter, the Vicor PI3105, for uninterruptible power supplies (UPS) to power the battery pack electronics to maintain safety system operation when isolated from the vehicle power supply; it also allows the electronics to be powered independently of the vehicle to enable remote connection for system inspection.
Comparing 12V and 48V power supply networks
Future cars will inevitably require smaller, lighter and more efficient power products to meet the growing performance demands. As OEMs turn to 48V batteries capable of handling high power, a modular approach can improve the efficiency of the power supply network through smaller and lighter cables and connectors, thereby reducing power consumption and weight.
Paul Yeaman, director of application engineering at Vicor, believes that the high density and high efficiency of 48V are crucial to automotive power. He said: "For the automotive industry, the 48V MHEV system is a shortcut to quickly launch new vehicles with lower emissions, longer mileage and lower fuel consumption. It also provides exciting new design options for improving performance and reducing CO2 emissions."
Paul Yeaman: 48V MHEV system is a shortcut to rapid vehicle innovation
Comparing the traditional 12V centralized architecture and the 48V distributed architecture, it is not difficult to find that the centralized 48V-12V DC-DC converters (SilverBox) are mostly bulky and have thick wiring harnesses because they use an earlier low-frequency switching PWM topology. In addition, they also bring single points of failure to a large number of critical powertrain systems.
Traditional 12V centralized power distribution architecture
48V Distributed Architecture
A distributed power architecture with modular power components uses smaller, lower-power 48-12V converters to distribute power to 12V loads in the vehicle. The simple power equations P = V I and PLOSS = I2R show why 48V power distribution is more efficient than 12V.
Compared to 12V systems, for a given power level, 48V systems have four times lower current and 16 times lower power consumption. At 1/4 the current, cables and connectors are smaller, lighter, and less expensive. In addition, the distributed power architecture has significant advantages in thermal management and power system redundancy.
94% and 98% efficient DC-DC converters
“Introducing 48V MHEV systems offers OEMs significant advantages once the design is complete,” said Yeaman. “Of course, overcoming the reluctance to change to the long-standing 12V power supply network is likely to be the biggest challenge. Changing the power supply usually requires new technologies that have been extensively tested, and may also require new suppliers who respect the automotive industry’s high safety and quality standards for power supply.”
>> Click here to learn more about Vicor's automotive solutions
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