![]() ![]() Even though it converts DC to DC, the BCM uses a transformer to convert AC to AC at high efficiency, scaling the magnitude by the K factor and using the switching blocks to convert between AC and DC. Fixed-ratio conversion, bidirectional operation, fast transient response (higher than 8megaamps per second), and a low-impedance path collectively enable the BCM to make HV battery appear like a 48V battery, which we term “transformation.” This ability to transform a power source is both the key benefit and key differentiator when compared to conventional converters.įigure 4: Functional block diagram of BCM Bus Converter. The BCM’s high-frequency operation provides a fast response to changes in load currents and a low-impedance path from input to output. For example, the BCM6135 operates at 1.2MHz and, unlike a conventional ZVS/ZCS resonant converter, the BCM operates within a narrow band frequency (Figure 3). Utilizing zero-voltage, zero-current switching (ZVS/ZCS), Vicor BCM® Bus Converters operate at higher frequencies than conventional converters making them more responsive than a physical battery. A virtual 12V battery is created by transforming the high-voltage battery with Vicor BCM Bus Converter technology. OEMs were very creative to bypass the 12V power limitation and complex electrical architectures have been designed in recent years with two 12V batteries, one 24V battery for power steering and several DC-DC converters between them.įigure 2: Optimized E/E architecture eliminates the physical 12V battery. This legacy architecture originated when vehicles had an alternator, a sensitive 12V PDN that needed regulation to charge the battery, keep the radio operating during cranking event or maintain incandescent headlights at the right intensity. A high-voltage-to-12V DC-DC converter regulates the 12V bus (with efficiency hit) and the pre-regulator provides the suitable internal rail voltage for each load (Figure 1). From a global system view for an EV, HEV or PHEV, there is redundancy of series regulator stages. In a typical automotive 12V PDN, all the 12V loads connected to the 12V bus have internal pre-regulators able to convert wide input voltage range typically from 6 to 16V to regulated rails of 5V, 3.3V or lower. Maintaining a physical 12V battery means maintaining an inefficient PDN with unnecessary redundancy. By contrast, eliminating the 12V battery altogether removes 13kg from the vehicle and can improve the cargo space by 2.4%. What it does add is weight, vehicle packaging complexity, and system cost it also reduces overall vehicle reliability. ![]() įurthermore, adding a bulky DC-DC converter from HV to 12V (with voltage and current regulation feature) is needed to recharge the 12V Li-Ion battery and supply the electrical loads. It is the direction taken for instance by Tesla and Hyundai. The 12V Li-ion battery needs a Battery Management System (BMS) to control the charging and maintain the full battery operation over the vehicle life. Simply replacing the 12V lead-acid battery with a 12V Li-ion battery saves ~55% weight however, it has a high cost impact. There are many benefits to the latter option, but both merit further exploration. The other option is to support a 12V PDN powered from the primary 400V or 800V battery in EV and HEV/PHEV. While it does slightly reduce weight, it retains the decades-old legacy of the 12V PDN, which yields no additional benefits. Replacing the 12V lead-acid battery with a 12V Li-ion battery is one option. There are two primary options for solving this equation. When considering potential solutions, OEMs must take into account a number of key factors: adding more power to support new features with better performance, increasing efficiency for longer range and better thermal management, reducing CO 2, optimizing cable routing, reducing harness weight and meeting EMI requirements are some of the variables within this complex equation. High-density, high-power and efficient power modules used to interconnect high-voltage, 48V and 12V PDNs offer the most flexible and scalable solution to this impending challenge. The 12V battery and power delivery network (PDN) are standard across the globe, supporting hundreds of loads, including some critically related to safety, so the solution will need to be both innovative and robust. While this may seem like a daunting task, it also presents a tremendous opportunity to eliminate the environmentally toxic battery while also reducing weight in a vehicle and improving overall efficiency. Europe has decreed that no new cars will have lead-acid batteries after 2030, creating a considerable challenge for OEMs to find alternative solutions. Yes, the 12V lead-acid car battery is dead. By Nicolas Richard, Director Automotive Business Development, Vicor Europe
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