PC Power Supply+12V distribution

The +12V output is very important in PC

power supplies because the CPU and VGV

both require a +12V input.

The +12V output can be subdivided into a

single +12V rail and multiple +12V rails.

+12V distribution

The single output is mainly used for a single device whose

maximum power consumption may exceed the 240VA limitation

(which may trigger Over Current Protection, OCP) or when two or

more power-intensive devices cannot be effectively distributed

among multiple +12V rails, a single rail with a large output is then

required.

Single +12V rail

Single +12V railAdvantages:

1. Mainstream design.2. Compatibility issues rarely occur.3. No power dispersion on power distribution.4. Without current protection, problems almost

never happen. 5. No need to keep track of which devices are

connected to which rail.6. Makes cable connections easier to manage, and

you generally need fewer cables so you can keep the case neater.

Disadvantages:1. Insufficient power can become significant when

using high-power devices.2. Even with the OCP, the direct output current

may still damage components.3. A single +12V output will be significantly

affected when the output is unbalanced. 4. In the event of a short circuit and the power

supply responding slow, the shorted component may be burnt.

5. In prolonged high or full load work conditions, both the heat dissipation and power conversion of the power supply will be unsatisfactory, power tends to be lost, and the service life will be shortened significantly.

The purpose of multiple +12V rails is to prevent

excessive voltage drops caused by a single high-power

device that affects operation of other devices.

Each rail is limited for a maximum output of 240VA (no

more than 20A in the case of 12V).

Multiple +12V rails

Multiple +12V railsAdvantages:1. No insufficient power even when using high-power accessories.2. Each +12V rail has independent short circuit protection, providing a complete safeguard.3. Two independent +12V outputs will only affect each other to a minimal extent under any

conditions.4. Splits a single +12V source into multiple +12V outputs, with each wire having a limited

output current. This makes the circuit configuration safer.5. Since the power supply works at (relatively) low-load conditions most of the time, it

greatly helps with heat dissipation control or integral conversion efficiency, thus service life of the power supply is therefore prolonged significantly.

6. In the event of a short circuit, the power supply will react quickly to cut off the power, therefore protecting system components.

Disadvantages:1. Standard accessories in the case rarely require multiple +12V rails.2. Distribution of the multiple rails must be designed carefully so as to prevent excessive

over current protection.3. The load of each rail must be able to be read to have a comprehensive understanding of

the power output. If rail splitting is poor, wasted wattage will occur.

Which one is better?

In current multiple rail switching power supplies, the difference between a single large output rail and multiple small output rails is only in the setting of output distribution. For general applications, single rails differ little from multiple rails. However, for users with high-end CPUs, CPUs with compressed overclocking functions, or dual CPU platforms in combination with high-power single or dual VGA cards, using a high-output single rail power supply can minimize disturbances from OCP activation due to the output limitations and poor circuit distribution of multiple rail configurations.

Which one is better?

In summary, the single +12V rail is more economical and easier to use than multiple +12V rails. Therefore, it’s more common to find the single +12V rail power supply in the end user market.

Multiple +12V rails provide more comprehensive protection than a single +12V rail. System Integration will more tend to bundle the Multiple +12V rails power supply in the system. In fact, they all have their pros and cons. As for which one is the better choice, it all depends on what the user’s requirements are.

ERN SeriesAvailable Wattage 300, 350, 400, 450, 500, 550, 600W

Dimension 140mm (L) × 150 mm (W) × 86mm (H)

General Specification

Efficiency Level 80PLUS Sliver

Erp Lot <0.5W

Input Voltage 100~240Vac

Efficiency 85%@ 20% load; 88%@ 50% load; 85%@ 100% load

Output Voltage+3.3V +5V +12V -12V +5Vsb

300W 21A 15A 24A 0.3A 3A

350W 21A 15A 28A 0.3A 3A

400W 24A 14A 33A 0.3A 3A

450W 24A 15A 36A 0.3A 3A

500W 24A 20A 39A 0.3A 3A

550W 24A 22A 42A 0.3A 3A

Model Available - Single 12V rail ERN Series

EGN SeriesAvailable Wattage 400, 450, 500, 550, 600W

Dimension 140mm (L) × 150 mm (W) × 86mm (H)

General Specification

Efficiency Level 80PLUS GOLD

Erp Lot <0.5W

Input Voltage 100~240Vac

Efficiency 90%@ 20% load; 92%@ 50% load; 89%@ 100% load

Output Voltage+3.3V +5V +12V1 +12V2 +12V3 +12V4 -12V +5Vsb

400W 16A 16A 18A 18A - - 0.3A 3A

450W 16A 16A 18A 18A - - 0.3A 3A

500W 16A 16A 18A 18A - - 0.3A 3A

550W 16A 16A 18A 18A 18A - 0.3A 3A

600W 20A 18A 18A 18A 18A 18A 0.3A 3A

Model Available - Multiple 12V rail EGN Series

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