What is the difference between a tranformer and a rectifier which are found in a computer power supply?

Answer 1

Transformer is a device that works only with AC (alternating current), and is frequently use to step up (increase) or step down (decrease) the voltage level. Therefore we can say that, in order to maintain or to bring the voltage level up to our requirement we use Transformer.

Though there are many classifications of Transformer, but more or less there purpose is almost the same, however only the function of instrument Transformers (includes current transformer & potential/voltage transformer) is bit different. Voltage transformer is used with high voltage power systems and is use to bring the voltage level up to the rating where it can be measured easily by ordinary instruments (usually 120V). Similarly current transformer is used to bring the high rating of the current up to the value where it can be measured easily (usually 5A).

Rectifier is a device that is used to convert the Alternating current into Direct current or in short AC to DC converter is called rectifier. Rectifier is also classified as half wave, full wave, bridge, etc, but more or less there purpose is almost the same, except for the difference in their conduction pattern (half wave conduct for half cycle, full wave conduct in both directions for complete cycle). Conduction pattern of rectifier is determined by the number and working of diodes (the major component of rectifier).

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Abdul Haseeb E & I Inspection Engineer at RICI Dammam, Saudi Arabia email: abdulhaseebb@gmail.com

Answer 2

A Transformer is used to step down the power supply from the ac line input.

It is a large, heavy soft iron core surrounded by coils of wire.

A rectifier is a semiconductor device used to convert this step down AC voltage to DC. A rectifier gives pulsating DC which then needs to be smoothed by a capacitor before output.

Most modern power supplies use a 'Switched Mode' system, which does away with the heavy transformer taking full power.

The AC mains is rectified first and smoothed to give a high voltage DC.

This high voltage DC is chopped up by a power transistor, into small pulses, which are again smoothed by a capacitor. Voltage and current regulation is controlled by electronics. Transformers are found in SMPSU's, but their role is to provide feedback and monitoring of the process.