Column: Electric Vehicles
3. Incorporating an architecture that performs better than IBA; for example Vicor’s own Factorized Power Architecture (FPA). Moving from a 12V intermediate bus PDN to a 48V PDN is
challenging but also brings advantages. Maximising the 48V power delivery as close as physically possible to the PoL regulators will reduce cable, connector and PCB copper power plane size, weight and cost; see Figure 5. PoL space constraints are oſt en a problem, so the converter must off er high power density and effi ciency. A non-isolated fi xed-ratio bus converter is the best option as long as the PoL regulators can handle the voltage variation on their input, which is determined by the voltage input range to the bus converter, divided by the turns ratio or K factor (VIN = VOUT
/K ). If the bulk power converter is designed with reasonable Figure 4: HV to 48V conversion
regulation tolerances, then this design approach is both feasible and advantageous. For designs where the bulk power converter or bulk power
source (such as a 48V battery) has a wide output voltage range, then regulated DC-DC converters may be required, depending on the PoL regulator input voltage specifi cation. Adding regulation to the 48V-to-12V stage reduces the effi ciency of the converter between 2% and 4%, depending on its topology. To really advance the PDN design, with signifi cantly improved
Figure 5: 48V-to-12V isolation Data centres and exascale computing commonly require
maximum processing power in a confi ned space, so they need advanced, high-density component-cooling techniques. In some cases full immersion cooling is used, where the entire server is placed in a bath of fl uorinert (a coolant liquid). Alternatively, other high-performance computing applications are developing cooling techniques with heat-pipe and cold-plate technologies. In these applications a low-profi le planar package is required for the power conversion and regulation stages of the bulk power system.
Innovating intermediate-bus and PoL power delivery T e opportunities for innovating 48V intermediate-bus PDNs lie in the following areas: 1. Using non-isolated, fi xed-ratio bus converters for 48V-to-12V conversion;
2. Using high power-density, regulated- power module converters;
16 May 2023
www.electronicsworld.com Figure 6: DC-DC conversion and regulation
performance and high current density at the PoL, a new architecture to consider is Vicor’s FPA; see Figure 6. With it, a new type of converter called a “current multiplier” is placed very close to the load; the current multiplier does direct 48V-to-load voltage conversion with high effi ciency and density. T is is highly advantageous in high-current applications, as it reduces the PDN impedance between converter and load, which can be a source of very high power losses and impact di/dt transient performance. Because the current multiplier is a fixed-ratio converter,
an upstream regulation stage is needed to complete the FPA design. To maximise efficiency and density whilst minimising power losses, the regulator module operates with both input and output voltages set to 48V, with the current multiplier K factor chosen to provide the required output voltage for the load.
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