Introduction to Voltage Regulators
All electronic circuits require one or more stable sources of continuous electric current.
Power supplies built with a transformer, a rectifier and a filter (non-regulated power supplies) do not provide enough quality because of their output voltage, that is changing with the current that flows through the load and because of the changes on the line voltage.
They also have a significant amount of ripple voltage that has the same frequency of the network. This is why they are not generally suitable for most applications.The picture 1 shows a block diagram of a typical regulated power supply.
At the input there is an electric transformer that is connected to a 110/220 VAC in order to reduce the input amplitude.
- Rectifier diodes rectified the signal, that is filtered (usually through a capacitor) to produce an unregulated DC output.
- A voltage regulator provides much more regulated output.
The function of the voltage regulator is to provide a stable and fixed voltage and to give energy to other circuits from a poor quality power source. In addition, voltage regulators must be able to provide currents from few tens of milliamps, in the case of small voltage regulators, up to several amps, in the case of the big ones.
After the operational amplifier, the voltage regulator is probably the most widely used integrated circuit.