How a Power Supply Works

This article describes in easy terms the operation of a Basic Power Supply unit of the kind used with telecommunications instrumentality (switchboards, physics house exchange systems, plan-sets, etc).

So, what is a power supply? The term power provide is a lot of normally abbreviated to PSU, this may be wont to  electronic device to be ready to work. So, the facility supply unit is use to come up with a voltage that may be supply in associate device in accordance with the wants of the mains voltage from that device. Telecommunications instrumentality and notebook is meant to control on lower voltages than electrics domestic Mains voltage. So as to scale back this voltage a PSU (Power Supply Unit) is employed.

To provide a useable low voltage the PSU desires a number of criteria :

1. Scale back the Mains 220V AC (Alternating current) voltage to a lower level, examples 5VDC. 
2. Convert this Lower Voltage from AC to DC (Direct current), this use Diode and Capacitor to converting.
3. Regulate the DC output to make amends for varied load (current demand)
4. Give Protection against excessive input/output voltages, it use Regulator supply system.

1. Reduction of AC Mains

This is achieved by employing a device called a electrical device associate magnetic attraction device consisting of associate ferric email iron core that incorporates a sizable amount of turns of wire wound around it, called the first Winding. The ends of those turns of wire being connected to the input voltage, in this case Mains AC.

A second range of turns of wire-protected measure wound round the coil, this set being called the coil.

The distinction between the quantity of turns provides simplest way of reducing a high AC voltage to a lower one.

2. Conversion of AC to DC

To convert our currently low AC voltage to DC we tend to use a Rectifier Diode connected to the coil.

This is a chemical element diode, that has operation analogous to a bicycle Tyre valve (as the valve solely permits air to flow into the Tyre, the diode solely permits current to flow in one direction).

As our low AC voltage are going to be functioning at a frequency of 50 - 60Hz (Mains AC frequency) it's fascinating to scale back the inherent hum on this to a lower level.

This is achieved by a method called Smoothing (filtering out the bumps within the AC).

A simple thanks to scale back the hum is to use Full Wave Rectification.

Today this is often typically done by four diodes during a bridge configuration called a Bridge Rectifier. (This will be four individual diodes or an infatuated self contained package)

3. Give Regulation of Output Voltage, [SEE next article from about REGULATOR.

The capacitance could be a device capable of storing energy the quantity of energy and therefore the time it remains hold on counting on the worth. In a straightforward PSU the simplest thanks to give regulation to make amends for varied load conditions is to use a try of comparatively high price Electrolytic Capacitors.

Their values during this case being within the between of 470uF to 4700uF counting on the applying and therefore the quantity of current needed from the output of the unit. One of these capacitors and Electrolyte Capacitors is connected across the DC output of the rectifier diode(s) or bridge, this electrical device conjointly providing an additional degree of smoothing the output wave.

The second electrical device is connected via an occasional price, medium to high electric power resistance, that assists in limiting this demand.

4. Protection against excessive voltages

In a straightforward PSU the simplest thanks to do that is by providing fuses at the input to the electrical device, usually within the live facet of the mains provide, conjointly at the DC outputs.
In the event of associate excessive input voltage, or excessive current being drawn from the output, one amongst these fuses ought to commonly blow protective the PSU and therefore the instrumentality connected to that.
The electrical device might also be fitted with an indoor or external thermal fuse, which can open if the electrical device becomes hot thanks to the said conditions.

How a Power Supply Works