October / November 2021

32 AUTOMOTIVE POWER www.vicorpower.com Issue 4 2021 Power Electronics Europe www.power-mag.com the powertrain and all the auxiliary loads. Vicor high-density bus converter module technology enables this approach by virtualizing a low-voltage battery (48 V or 12 V) directly from the HV battery (400 or 800 V). Utilizing zero-voltage, zero-current switching (ZVS/ZCS), CM® Bus Converters operate at higher frequencies than conventional converters making them more responsive than a physical battery. For example, the BCM6135 operates at 1.2 MHz and, unlike a conventional ZVS/ZCS resonant converter, the BCM operates within a narrow band frequency (Figure 3). The BCM’s high- frequency operation provides a fast response to changes in load currents and a low-impedance path from input to output. Fixed-ratio conversion, bidirectional operation, fast transient response (higher than 8 MA/s), and a low-impedance path collectively enable the BCM to make HV battery appear like a 48 V 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. The BCM operates as a fixed-ratio converter where the output voltage is a fixed fraction of the input voltage. The BCM6135 converter is isolated and provides 2.5 kW of power in a 61 x 35 x 7 mm package with over 97 % peak efficiency. It can be paralleled easily in an array to deliver even more power. The fixed-ratio nature of the BCM ensures that the virtual battery will stay within its appropriate operating range. For example, the HV battery is guaranteed to stay between 520 V and 920 V on an 800 V battery-powered electric vehicle. A BCM6135 with 1/16 ratio virtualizes a 48 V battery with a voltage range guaranteed to stay between 32.5 and 57.5 V. A BCM6135 1/8 ratio could be used for 400 V EVs (Figure 3, 4). The battery virtualization can also be extended to the 12 V bus with a fixed- ratio converter of 1/4. In that case, galvanic isolation is not required and a NBM™ Bus Converter could be used. Identical in all other features to a BCM, the NBM non-isolated bus converter has all the same benefits previously described: fast transient response, low impedance, and bidirectional operation. The voltage range on the 12 V stays between 8.125 and 14.375 V with a fixed ratio to the HV battery voltage. BCM and NBM technology are ideal transformers connecting each of the vehicle power networks (Figure 5). Ensuring redundancy of power delivery for functional safety loads is essential. Because Vicor power modules are fully scalable in power and delivery, they can be designed to act as redundant PDNs enabling functionally safety-critical loads to be supplied with two dedicated power conversion paths. Ultimately, OEMs could implement localized energy storage to ensure functionally safe operating of critical systems such as ADAS, steering and braking. EV power delivery network at a crossroads The 12-volt lead-acid battery will soon meet its demise in Europe. And the timing is perfect given all the innovation that is driving the redesign of the EV power delivery network. The automotive electrical PDN is at a crossroads with 12 V power delivery. More and more demanding power loads are Figure 2: Optimized E/E architecture eliminates the physical 12 V battery. A virtual 12 V battery is created by transforming the high-voltage battery with Vicor BCM® Bus Converter technology LEFT Figure 3: The fast load transient response of BCM6135 is the key to supporting the 12 V loads (yellow : input voltage (800 V DC), red: output voltage (48 V), blue: output current)