Modular power supply unit

A modular power supply to the left and a non-modular power supply to the right.

A modular power supply unit, abbreviated MPS, is a type of computer power supply with cables to powered devices attached by removable power connectors instead of permanently fitted. General-purpose non-modular power supplies have all the cables that may be required in any configuration permanently fitted, leading to unconnected cables loose inside the computer; but unused cables are omitted from an MPS configuration.

Some companies, including Kingwin^[1] and Ultra Products^[2], state that they have patented some aspect of their modular interface.

Benefits

Power connections required vary from one computer to another, depending amongst other things on the number of drives (HDD, optical, floppy) fitted. General-purpose power supplies with fixed leads are made with enough leads and connectors to allow for the largest expected configuration; in a more restricted case, bulky leads will be left unconnected inside the equipment housing.

By allowing unused cables to be detached, the clutter of unused cables is eliminated in a modular supply. This provides more visibility into a computer case, more space to work and it decreases likelihood of damage to nearby components from extraneous or dangling unused live power cables. Airflow within a case may also be improved by eliminating superfluous cables.

While only benefitting appearance as perceived by the owner, some modular PSUs have UV-reactive or LED components in the detachable cables, or even inside the unit, to flash lights for purely decorative purposes, making no change to power supply operation^{[citation needed]}. This is done in conjunction with a modified case that allows the lights to be seen.

Disadvantages

• Modular cables and connectors add electrical resistance between the power supply and the hardware components. In practice the resistance of a connection is far too small to cause significant voltage drop^[3], although the additional connections are an additional possible point of failure if they become corroded or damaged.

• Connectors may become accidentally disconnected or not fully engaged, especially inside crowded cases, and modular PSUs have more connections than others at risk. Many PSUs have connectors with locking mechanisms which prevent a connector from falling out or not being fully inserted. Pairs of connectors are also additional components subject to mechanical damage when being plugged in or unplugged carelessly.

• As of early 2011^[update] most modular power supplies used the same connectors as each other, but with different, non-standardized pin-outs. Interchanging cables between brands can damage equipment by applying incorrect voltages, grounds and opens to outputs such as SATA power connectors. There is rarely any visual indication or keyed connector to prevent using an incorrect cable.

References

1. ^ "Kingwin's 'Mach 1' Modular Power Supply". http://kingwin.com/products/cate/power_supplies/mach1_series.asp. 
2. ^ "All New Ultra X3® Modular Power Supplies". http://www.ultraproducts.com/applications/SearchTools/item-details.asp?EdpNo=2937371. 
3. ^ motherboards.org: Modular Power Supplies: The Reality of the Resistance Article describing detailed investigation of the effect of connector resistance on power supplies