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A power supply is a device or assembly that takes electrical energy from a source and delivers it to a load in the form the load needs. In electronics that usually means converting AC from the wall into regulated DC. It can also mean changing one DC voltage into another. This glossary defines the term and the vocabulary used to specify, compare and match supplies.
What is a power supply?
“Power supply” names a function, not one voltage, connector or product. The supply sits between a source (mains, a battery, another DC rail) and a load (a circuit, device or piece of equipment). It adapts the source’s power to what the load can use. Monolithic Power Systems and Acopian both describe it in these terms: accept the available input power and convert it to the form the application requires.
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OMRON’s industrial automation glossary gives a narrower, DC-focused wording. It describes a device that supplies the required stabilized DC power, converted from commercial AC or from DC power. That fits most electronics, but it is not the whole category. A supply may be an external adapter, a module inside a computer, a bench instrument or a small converter on a circuit board.
What does a power supply do?
- Converts the input to a usable type, for example AC to DC, or DC at one voltage to DC at another.
- Regulates the output so it stays within specified limits as input or load conditions change.
- Delivers enough current for the load to draw what it needs.
Not every supply does all three equally well. Regulation in particular is a specification, not a given.
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- Hold up time is 16 millisecond minimum within 60 percent load. Input frequency range 50 - 60 in Hz
Core terms
Load
The circuit, device or equipment that receives power from the supply.
Input voltage
The voltage the supply receives from its source. Supplies are designed for a permitted input range, so check it against your source rather than assuming. Bel Fuse’s glossary treats input voltage range as a standard term.
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Output voltage
The nominal voltage delivered to the load. Bel’s glossary defines it as the nominal output voltage setting of a power supply.
Output current rating
The current the supply can provide under stated conditions. The load decides how much current is actually drawn, and the rating is the supply’s capability. A supply is not forcing its full rated current into the device. Adafruit’s example of a 9 V DC, 500 mA supply shows the idea. It can deliver up to 500 mA at 9 V, and a device that needs less simply draws less.
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- Delivers 500 Watt Continuous output at plus 40 degree. Compliance with Intel ATX 12 Volt 2.31 and EPS 12V 2.92 standards
- 80 PLUS Certified, 80 percentage efficiency under typical load
- Supports (2) PCI E 6plus2pin Connectors. Active (PFC) Power Factor Correction, MTBF: 100,000 hours
- Industry Grade Protections: (OPP) Over Power Protection, (OVP) Over Voltage Protection, (SCP) Short Circuit Protection
- High Quality Components
AC and DC
OSHA’s electrical glossary defines alternating current (AC) as current that flows back and forth, and direct current (DC) as current that flows in one direction. Wall outlets supply AC, and most electronics run on DC, which is why conversion is so common.
Regulated and unregulated supply
A regulated supply is designed to hold its output voltage (or current) within specified limits as input or load varies. Adafruit notes that an unregulated supply can produce a voltage above its nominal value under some conditions, typically when lightly loaded. That matters for sensitive equipment.
Rank #4
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- Fully modular design
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DC-to-DC converter
A supply that accepts DC input and produces DC output, usually at a different voltage.
Derating
Reducing the allowed output current under specified conditions, often at elevated operating temperature. The actual limits are in the unit’s datasheet.
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- 80 PLUS GOLD CERTIFIED: Delivering gold-level performance with 92% efficiency, ensuring effective power transmission to your components.
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- Support ATX 3.1 & PCIe 5.1: Compliant with the ATX 3.1 standard to fuel high-performance PC components with stability, efficiency, and power spike resistance. Meanwhile, supporting PCIe 5.1 platform withstands 2x transient power excursions from the GPU.
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- RGB Silent Fan & RGB Lighting Model: This 140mm low-noise fan comes with a silent mode, it outperforms standard 120mm fans in terms of quietness, heat dissipation capability and durability. What's more, the psu features ARGB lighting model, allowing you to adjust the lights style according to your needs.
Common types of power supply
| Type | What it does | Notes |
|---|---|---|
| AC-to-DC supply | Converts AC input to DC output | Typical of wall adapters and the supplies inside electronics |
| DC-to-DC supply | Takes DC in and gives a different DC out | Used where a DC rail must be stepped to another voltage |
| Linear supply | Controls output with a linear pass element | Per IEEE, the excess of input over output voltage is dissipated as heat, so efficiency falls when that difference is large |
| Switch-mode supply (SMPS) | Uses switching conversion | Common in adapters and electronic equipment; check each model’s noise, efficiency, thermal limits and protections |
| Bench supply | Test equipment that powers a circuit under test | Usually adjustable; useful for learning and prototyping |
Linear versus switch-mode is a design choice, not a quality ranking. Efficiency, heat, noise, size and cost depend on the particular design and its operating conditions, so avoid assuming one topology is always quieter, safer or better.
For circuit testing, an adjustable bench DC power supply lets you set voltage and a current limit. Pick one whose ranges and protections fit the project. NYU’s Interactive Telecommunications Program, for example, uses a regulated 12 V, 1000 mA switching supply as a circuit-power example.
How to compare or match power supplies
Bel’s glossary and the educational sources point to the same axes for comparison:
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- Output voltage and current
- Regulation accuracy, ripple and noise
- Conversion topology, efficiency and heat
- Isolation and protections
- Physical format, connector and polarity
- The conditions (such as temperature) under which ratings apply
Checklist for replacing or choosing a supply
- Read the device’s required voltage and whether it needs AC or DC.
- Match the output voltage to that requirement.
- Choose a supply whose current rating meets or exceeds what the device needs.
- Check connector size and plug polarity. NYU specifically warns readers to verify polarity.
- Confirm the supply’s input range suits your mains or source, and look for any required safety certification.
A matching plug does not mean a supply is compatible. These are general guidelines, and the device manual and the supply’s datasheet take precedence.
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