Electronic voltage regulators:

Electronic voltage regulators operate through comparing the actual output voltage to a few internal fixed reference voltages. Any type of difference is amplified and employed to control the regulation element in such a manner as to reduce the voltage error. This makes a negative feedback control loop; increasing the open-loop gain tends to get increase regulation accuracy but get reduce stability. There will as well be a trade-off among the stability and the speed of the response to changes. If the output voltage is very much low (perhaps because of input voltage reducing or load current increasing), regulation element is commanded up to a point to generate a higher output voltage - by dropping less of the input voltage (for linear series regulators and buck switching regulators), or to illustrate input current for longer periods (boost-type switching regulators); if the output voltage is very much high, the regulation element will generally be commanded to generate a lower voltage. Though, many regulators have over-current protection, that is why they will completely stop sourcing current (or limit the current in some way) if the output current is very much high and some regulators may also shut down if the input voltage is outside a specific range.