Voltage regulator:

using voltage regulators

Device or circuit that maintains constant output voltage (within certain limits) in spite of changing line voltage and/or load current.

With the exception of shunt regulators, all voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element.

If the output voltage is too low, the regulation element is commanded to produce a higher voltage. If the output voltage is too high, the regulation element is commanded to produce a lower voltage. In this way, the output voltage is held roughly constant. The control loop must be carefully designed to produce the desired tradeoff between stability and speed of response.

The image shows a simple zener voltage regulator. It is a shunt regulator and operates by way of the zener diode's action of maintaining a constant voltage across itself when the current through it is sufficient to take it into the zener breakdown region. The resistor R1 supplies the zener current I_Z as well as the load current I_R2 (R2 is the load). R1 can be calculated as -

  where, V_Z is the zener voltage, and I_R2 is the required load current.