The series voltage regulator format or as it is sometimes referred to as a serial step regulator is the format most commonly used to provide final voltage regulation in a linear voltage regulator circuit. As its name suggests, the series voltage regulator or the series-step voltage regulator operates using a variable element in series with the load.
Basics of the Series Voltage Regulator
The series voltage regulator or the voltage regulator in series use a variable element placed in series with the load. By changing the element resistance in series, the voltage dropped through it can be varied to ensure that the voltage across the load remains constant.
The advantage of the serial voltage regulator is that the amount of current drawn is actually used by the load, although some will be consumed by any circuit associated with the regulator. Unlike the bypass regulator, the series controller does not draw the full current even when the load does not require any current. As a result, the series controller is considerably more efficient.
Transistor Series Voltage Regulator
In the following figure, you can see a simple voltage regulator series that is using a transistor and a Zener diode.
You can see in the figure that the load current is passing through the series transistor Q1 and that is why we call the circuit a voltage regulator in series. You can see that we fed the d.c. not regulated. supply through the input terminals so that we can get the regulated through the load. Here, the zener diode provides the reference voltage.