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The increased use of 48V battery subsystems, in addition to conventional 12 V networks, is causing a noticeable change in the design of HEV/EV power systems. 48V delivers more power without the penalty of heavy cabling to reduce the power loss in the wire harness leading to extended drive range. With this change, the vehicle power distribution architecture is transitioning from traditional centralized to zonal approach where power distribution, communication and load actuation are grouped together based on location in the vehicle rather than by function, as shown in Figure 1. Zonal architecture reduces system complexity and gives original equipment manufacturers (OEMs) more modularity.

Figure 2 shows a typical power distribution where multiple power sources are used to realize redundant power supply for a zone control module. Ideal diodes, as discussed in the white paper, "Basics of Ideal Diodes," are great for applications that require reverse current blocking and/or reverse polarity. Since ideal diodes offer reverse current protection, they are also useful in applications where combining multiple supplies increases system redundancy [2]. However, the existing ideal diode controllers in the market are only rated for 72V absolute max and have limitations to support certain 48V system designs.

This article discusses the challenges of designing an ORing stage for a 48V system and how a cascaded ideal diode configuration enables a reliable ORing solution to safely handle the input supply interruptions and external transient events.