The impetus for lower voltages is two-fold: to reduce losses in the power-conversion process, and to allow use of lower-power ICs and circuits.Ī: Absolutely, for both legacy reasons, and due the mandatory needs of some circuits and components. As time went on, the DC rail voltages dropped to 15, 12, 5, and 3.3 V, and now are at the low single digits such as 1.8, 1.2, and even 0.8 V. Q: What are some of the common DC-rail voltages in use?Ī: Older systems used 48 V and 24 V, both of which are below the human-safety threshold. DC rails which are not steady at the right voltage are the equivalent of low or fluttering blood pressure, and will cause system weakness, poor or erratic performance, or even shutdown. Just as with the blood-distribution system, the power rails deliver different amounts of voltage (pressure) and current (volume of flow) via different sized conductors (blood vessels) of course, the total current flow (blood volume) leaves and then returns via a loop to the source. Most electronic functions operate from DC, not AC, with the DC rails derived from other DC supplies (such as batteries) or from the AC line. This FAQ will explore those uses.Ī: They are the pathways used to deliver energy to the system, analogous to the flow of blood through arteries, capillaries, and veins within a body. That simple statement glosses over the wide range of voltages, issues of tolerance and ripple, designations of these rails, and management of both single and multiple rails.

Most circuits and systems now run on DC-voltage power rails.

Speccy rail voltage