Regulated Power Supply Specifications

Regulated Power Supply: 

The output voltage of a power supply stage changes due to the line supply voltage variation as well as the load current variation. When the line voltage decreases the output decreases and when it increases it increases. The output voltage of the power supply gets reduced with increasing load currents. The reason for the decrease in output voltage in a power supply stage with increase in load current is the drop across the rectifying diode, the drop across the transformer and the drop across the filter choke or the resistor.

From the characteristics desired out of a power supply stage we know that the output must be maintained constant irrespective of the line voltage change or load current change. In order to keep the output voltage constant for changing line voltage or changing load current we include a regulator circuit in a power supply stage.

A regulated power supply is one which generates constant supply voltage irrespective of the load variations or input variations.

Voltage regulation and current regulation also is carried on in the regulator circuit. From simple zener voltage regulator to feedback controlled voltage regulator there can be many types of voltage regulator circuits. Switched mode regulator circuits are also used.

Voltage regulation is to maintain the magnitude of the output voltage constant. Current regulation is to maintain a specific amount of load current and to limit the maximum magnitude of the load current. The regulator circuits will also be provided with short circuit protection.


The following are the important specifications of a regulated power supply. The specifications differ from manufacturer to manufacturer. However, majority of them are common.

1. Input voltage: 230 V 50 Hz mains voltage
2. Output voltage: As per requirement of the circuit
3. Load regulation: 0.01% or even better
4. Ripple: Less than 1 mV RMS or even better
5. Protection: Short circuit protection for indefinite period set by current limit control.

Output Voltage:

The output voltage may be a fixed value. This is the condition for power supplies used with equipment where the output voltage desired may be for example 48 V, 24, V 12 V, etc. Further there can be more than one independent output voltages derived from the same circuit.
Output voltage in case of laboratory type power supplies has a facility for coarse and fine variation of voltage and in such cases the maximum voltage will be specified. Ex. 0-30 V, This voltage will be maintained constant, by virtue of the regulator circuit, irrespective of variation in line voltage or load current variation.

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