Transformer + Rectifier + Smoothing + Regulator

 

The regulated DC output is very smooth with no ripple. It is suitable for all electronic circuits.

Further information: Transformer | Rectifier | Smoothing | Regulator

Transformer + Rectifier + Smoothing

 

The smooth DC output has a small ripple. It is suitable for most electronic circuits.

Further information: Transformer | Rectifier | Smoothing

Transformer & Rectifier

 

The varying DC output is suitable for lamps, heaters and standard motors. It is not suitable for electronic circuits unless they include a smoothing capacitor.

Further information: Transformer | Rectifier

Transformer

Transformer

Transformer circuit symbol

Transformer

Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC.

Step-up transformers increase voltage, step-down transformers reduce voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage (230V in UK) to a safer low voltage.

The input coil is called the primary and the output coil is called thesecondary. There is no electrical connection between the two coils, instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is stepped up.

The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.

turns ratio =	Vp	=	Np	and	power out = power in
	Vs		Ns		Vs × Is = Vp × Ip

Vp = primary (input) voltage Np = number of turns on primary coil Ip  = primary (input) current

Vs = secondary (output) voltage Ns = number of turns on secondary coil Is  = secondary (output) current

Transformer

Transformer only

 

The low voltage AC output is suitable for lamps, heaters and special AC motors. It is not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor.

Further information: Transformer