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Passive Voltage Regulation A passive voltage regulator may be used if the power supply consistently produces a voltage greater than what the components on the circuit require. This type of voltage regulator essentially consists of a resistor with a particular set of performance characteristics. A passive voltage regulator reduces the incoming voltage to the desired output level and dumps the excess energy as heat. Passive regulators frequently require a heat sink to dissipate this unneeded heat. Active Voltage Regulation Circuits that require the voltage to increase will require an active voltage regulator. Such voltage regulators typically use some type of negative feedback loop to control the voltage. This means that a voltage outside the desired range causes the voltage regulator to bring the voltage back to its specified range. In turn, this action causes the voltage regulator to stop modifying the voltage of the circuit. Mains Regulation Voltage regulators on a main AC power line to control the very large voltage changes on these types of circuits. The transformer on a mains line has multiple taps that control the circuit voltage. When the output voltage of the mains regulator drops below a minimum value, the regulator connects to a tap with a higher voltage. Similarly, when the output voltage rises above a maximum value, the regulator connects to a tap with a lower voltage. AC Voltage Stabilization AC voltage stabilization refers to the regulation of relatively minor fluctuations in AC voltage. These voltage regulators are routinely used in a home to keep the voltage within the range needed by household appliances. AC voltage regulators use a servomechanism that continually responds to minute changes in the transformer`s voltage to keep the house voltage within a narrow range. DC Voltage Stabilization DC voltage stabilizers control the voltage in a circuit that uses a battery. They use a shunting device such an avalanche breakdown diode, voltage regulator tube or zener diode to conduct only at a specified voltage. The shunt will carry as much current as needed to output this voltage. In order for a DC voltage stabilizer to operate safely, the current from the power supply may not exceed the maximum safe voltage limit of the shunting device. This is typically accomplished by including a series resistor in the circuit.

Voltage regulators are a good tool to have around the house in order to verify whether an appliance or electrical outlet is putting out the needed power to operate. You can even test equipment like tractors, generators, power supplies, electronically operated toys and your own car battery. But how do you know if the voltage meter is working properly itself? 1.Connect the voltage meter to the contact poles of a vehicle battery. While a car is running in idle, the voltage should read between 12 and 13 volts. 2.Raise the idle of the engine by having someone slowly set on the gas pedal. Volts should raise to between 14 and 15 volts. 3.Watch the voltage meter and if the needle is jumping around, does not go above 12 volts or goes higher than 16 volts, your regulator is not working correctly.

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages. Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line. Electronic voltage regulators A simple voltage regulator can be made from a resistor in series with a diode (or series of diodes). Due to the logarithmic shape of diode V-I curves, the voltage across the diode changes only slightly due to changes in current drawn or changes in the input. When precise voltage control and efficiency are not important, this design may work fine. Feedback voltage regulators operate by comparing the actual output voltage to some fixed reference voltage. Any difference is amplified and used to control the regulation element in such a way as to reduce the voltage error. This forms a negative feedback control loop; increasing the open-loop gain tends to increase regulation accuracy but reduce stability. (Stability is avoidance of oscillation, or ringing, during step changes.) There will also be a trade-off between stability and the speed of the response to changes. If the output voltage is too low (perhaps due to input voltage reducing or load current increasing), the regulation element is commanded, up to a point, to produce a higher output voltage–by dropping less of the input voltage (for linear series regulators and buck switching regulators), or to draw input current for longer periods (boost-type switching regulators); if the output voltage is too high, the regulation element will normally be commanded to produce a lower voltage. However, many regulators have over-current protection, so that they will entirely stop sourcing current (or limit the current in some way) if the output current is too high, and some regulators may also shut down if the input voltage is outside a given range. Article From https://en.wikipedia.org/wiki/Voltage_regulator