How efficient is a power supply?

A power supply’s efficiency is simply the ratio between the energy it consumes and the energy it supplies. No device can be perfectly efficient; there will always be losses in heat or electromagnetic fields.

What is the difference between efficiency and power supply efficiency?

Below is a formula for calculating efficiency and a high-level summary of these differences is as follows: In the context of a power supply, efficiency refers to how effectively the supply converts electrical input power (from the source) into output power (for the load device) without losing energy as heat or other forms of waste.

What is the difference between output power and input power?

1) The difference between output power and input power is the power being dissipated (primarily as heat). A power supply with 90% efficiency will lose 10% as heat. A power supply with 95% efficiency will lose 5% as heat, which means it will get only half as hot as the first example.

Does power supply efficiency depend on load?

The efficiency will also depend on the load. A power supply’s efficiency under no load will be different from that at the typical operating load or the maximum rated load. The change in efficiency with changes in loading will be non-linear and is typically at its highest value at or near the normal operating load.

What happens if a power supply has 95% efficiency?

A power supply with 95% efficiency will lose 5% as heat, which means it will get only half as hot as the first example. A power supply with 97.5% efficiency will lose 2.5% as heat, which means it will get only quarter as hot as the first example. This means that even a small efficiency difference can result in a big operational difference.

What is the efficiency curve for a power supply without load?

Efficiency without load is always 0%. This is because when the converter runs, it will consume a small amount of "housekeeping" power to run the switching circuits while delivering no output power (zero load current). This means a typical efficiency curve for a power supply will show zero efficiency at no load.