# Power Supply Terminology

Power supply terminology:

To Understand and study about DC-DC converters, Linear Power supply design, SMPS Design, we have to be familiar with various power supply terminology like Line/Load regulations, surge voltage, Transients etc. In this post, we had given definitions of various power supply terminology.

This post will serve as a quick reference for us, during the detailed study of advanced power electronics topics like switch mode power supply design.

Line Regulation:
Maintaining the output voltageVOUT steady when VIN varies over its stated operating range VINMIN to VINMAX (minimum input to maximum input) is called as line regulation.

Mathematically, line regulation is expressed as
dV/ VO × 100%

Maintaining regulation when IO varies over its operating range IOMIN to IOMAX (minimum load to maximum load) is referred as load regulation. Mathematically, load regulation is expressed as
dIO/VO × 100% (from IOMIN to IOMAX).

Loop Response:
The property of any converter to provide quick regulation (correction) under external disturbances is referred to as its Loop Response. Clearly, the loop response is a combination of its ‘step-load response’ and its ‘line transient response.’

Efficiency
Any regulator/power supply carries out the process of power conversion with an Efficiency, defined as
η = PO / PIN
where PO is the ‘output power,’ equal to
PO = VO × IO
and PIN is the ‘input power,’ equal to
PIN = VIN × IIN
Here, IIN is the average or dc current being drawn from the source.

The difference between input voltage to output voltage of a regulator [VIN − VO ] is commonly called as Headroom of the linear regulator.

Dropout:
The minimum possible headroom is known as dropout.

Low DropOut Regulators (LDO):
Regulators which can continue to work (i.e. regulate their output), with VIN barely exceeding VO, are called Low DropOut regulators, or LDOs.

This is the amount of time it requires the power
supply to recover to within load regulation limits in response to a step change in the load.

Surge:
A defined period of time where the input voltage will
exceed the VIN(HIGH) specification that the unit must survive and during which it may need to operate.

Transients:
These are very high voltage “spikes” (+/-) that are
characteristic of the input power system.

Holdup Time:
It refers to the time period during which the output voltages are maintained within tolerance after removal of the input supply.

Hold-Up Time is the amount of time (in milliseconds) that a power supply can maintain output within the specified voltage range after a loss of input power.  The hold up time of the power supply ensures that, If a short interruption in input power occurs the system will continue to run without resetting or rebooting. Now a days the power supply system should have 15-50 milliseconds of hold up time.

Point Of Regulation:
The POR is the point at which a power generation source senses and regulates the system voltage. The POR should be at the input terminals of the line contactor connecting the power source to the load bus.

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### 1 Response

1. DWA says:

How would one test the Zener Diode for breakdown failure?
TV sometimes comes on normal then breaks down after few minutes (loosing sound....also a test pattern is added to Video portion.