Column: Electric Vehicles
of the input voltage. Te BCM6135 is isolated and provides 2.5kW of power in a 61 x 35 x 7mm package with over 97% peak efficiency. It can easily be connected in parallel in an array to deliver even more power. The fixed-ratio nature of the BCM
Figure 4: Functional block diagram of the BCM bus converter. 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. The switching is done at high frequency, and due to the transformer-like energy transfer the conversion it has a fast response to transient load changes and presents a low- impedance path between input and output
ensures that the virtual battery stays within its appropriate operating range. For example, the HV battery is guaranteed to stay between 520V and 920V on an 800V battery-powered electric vehicle. A BCM6135 with 1/16 ratio virtualises a 48V battery with a voltage range that stays between 32.5V and 57.5V. A BCM6135 1/8 ratio could be used for 400V EVs; see Figure 4. Battery virtualisation can also extend to
the 12V bus with a fixed-ratio converter of 1/4. In this case, galvanic isolation is not required and a Vicor 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. Te voltage range on the 12V stays between 8.125V and 14.375V, with a fixed ratio to the HV battery voltage. Te BCM and NBM technologies are ideal transformers, connecting each of the vehicle power networks. Ensuring redundancy of power
Figure 5: E/E architecture with 12V and 48V battery virtualisation based on BCM6135 and NBM2317 modules. The 48V bus also serves as a more efficient source for powering higher loads in a vehicle, such as the A/C condenser, water pump and active chassis stabilisation systems
delivery for functional safety loads is essential. Because Vicor power modules are fully scaleable in power and delivery, they can act as redundant PDNs, enabling safety-critical loads to be supplied with two dedicated power conversion paths. Ultimately, OEMs could implement localised energy storage to ensure functionally safe operation of critical systems such as ADAS, steering and braking.
fast transient response (higher than 8MA/s) and a low-impedance path collectively enable the BCM to make the HV battery appear like a 48V battery, which we call “transformation”. This ability to transform a power source
16 November 2022
www.electronicsworld.com
is both the key benefit and a key differentiator compared to conventional converters. Te Vicor BCM operates as a
fixed-ratio converter, where the output voltage is a fixed fraction
At a crossroads The automotive electrical PDN is at a crossroads with 12V power delivery. More and more demanding power loads are appearing in vehicles whilst trying to keep architectural changes to a minimum. “What are we still doing at 12V?
Twelve volts is very much a vestigial voltage, it’s certainly low,” said Elon Musk, Tesla CEO.
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