Regulated Power Supplies - Essay Example

The zener diode will take up the variations in current required to keep the voltage across the diode the same. Limitations: the zener diode cannot accommodate an infinite variation of current. There is a minimum level of current it must carry to maintain the voltage, and if too much current is taken, and then it will overheat, and could be destroyed. When designing a simple regulator circuit, it is necessary to design the circuit to accommodate the likely variations. b) Transistor series regulator: A voltage regulator whose circuit has a transistor in series with the output voltage, a Zener diode, and a resistor chosen so that the Zener diode is approximately in the middle of its operating range is termed as transistor series regulator.

Mode of operation: The basis of operation of the circuit hinges around controlling the conductance of this series element by a control voltage. If the voltage of the output is tending to rise, then this will be detected and the control voltage will be adjusted to reduce the conductance of the series element which will cause the voltage across the series element to rise. As the series element and the load form a potential divider circuit, any voltage increase across the series control element will cause the voltage across the load to fall.

Similarly if the voltage across the load is tending to fall too low, then this will be detected, the control voltage for the series element will then cause the conductance of the series element to rise and the voltage across the load will be maintained. This is a typical form of negative feedback system. The control voltage must have a reference against which the output can be compared. This is often provided by a voltage reference circuit based around a zener diode. The output voltage from the regulator is taken, often through a potential divider, and compared