Power Supply Block Diagram Explanation

Need Of Regulated Voltage Power Supply:

  • The combination of rectifier and filter can produce a DC voltage which is almost pure ripple free voltage. The combination of rectifier and filter can be used as a DC power supply for certain application such as eliminators for Walkman or for rechargeable battery cell charger.
  • However the problem with this type of DC supply is that its output voltage will not remain constant in the event of fluctuations in AC input voltage or changes in the load current. Therefore type of power supply is called as as unregulated power supply.
  • But the expensive electronic instrument cannot use such a DC power supply. Because they need a DC power supply whose output voltage remains constant inspite of variations input voltage or load current.

Power Supply Block Diagram With Explanation:

power supply block diagram
  • The diagram above shows the power supply block diagram explanation containing 5-blocks a step down transformer, rectifier, filter, regulator and load.
  • The AC mains voltage is applied to a step down transformer. It reduces the amplitude of AC voltage and applies it to a rectifier.
  • The rectifier is usually bridge type full wave rectifier. It converts the AC voltage into a pulsating DC voltage. So the ripple in the pulsating DC is reduced by the filter which is connected after the rectifier.
  • The filter can be C type, L type, LC type or CLC type. The output or the filter is smooth DC voltage with a small ripple. The combination of transformer, rectifier and filter is called as the unregulated power supply.
  • Similarly the output of the unregulated power supply is connected at the input of the voltage regulator circuit to keep the output voltage constant. So the voltage regulator circuit can be either a series voltage regulator or a shunt voltage regulator.
  • Even though the output voltage of the regulated power supply remains almost constant, partially it does not remain exactly constant. It changes slightly due to changes in certain parameters, such as load current, input voltage or temperature.
  • Thus we get a contant DC voltage at the output of the regulated DC power supply.

Output Waveforms At Different Blocks:

Circuit Diagram of Power Supply Explanation:

  • The C is a filter capacitor which is connected across the load. The value of capacitor is very large i.e a few hundred micro farads in order to reduce the ripple successfully.
  • The electrolytic capacitors are normally used as filter capacitors. The filter capacitors is connected across (in shunt with) load, this filter is called as shunt capacitor.
  • Similarly as shown in the circuit diagram it uses zener diode as a voltage regulator. However, voltage regulator circuit should keep the load voltage constant inspite of changes in its input voltage or load current or load current and temperature.
  • The zener diode regulator is a shunt type voltage regulator because the control element zener diode is connected in parallel with the load resistance.


  1. We get a very high quality (pure) DC output voltage.
  2. Very low ripple contents in the voltage output.
  3. Output voltage remains constant inspite of variation in input voltage, load current or temperature.
  4. It is possible to get a variable regulated output voltage.


  1. Regulated power supplied in laboratories.
  2. Use in every electronics instrument.
  3. In operational amplifier circuits.
  4. In logic circuits.

For more information on Switch Mode Power Supply


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