Explain in brief the working of a series regulated power supply.

Q.) Explain in brief the working of a series regulated power supply.

 Subject: electronic devices and circuit

A series regulated power supply is a type of linear power supply that uses a series pass transistor to regulate the output voltage. The series pass transistor is placed in series with the load and its gate is driven by a control circuit. The control circuit senses the output voltage and adjusts the gate voltage of the series pass transistor to maintain the desired output voltage.

The basic operation of a series regulated power supply is as follows:

  1. The transformer steps down the AC mains voltage to a lower AC voltage.
  2. The rectifier converts the AC voltage to a DC voltage.
  3. The filter capacitor smooths out the DC voltage.
  4. The series pass transistor is placed in series with the load.
  5. The control circuit senses the output voltage and adjusts the gate voltage of the series pass transistor to maintain the desired output voltage.

The series pass transistor acts as a variable resistor, adjusting its resistance to maintain the desired output voltage. When the load current increases, the series pass transistor decreases its resistance to allow more current to flow through the load. When the load current decreases, the series pass transistor increases its resistance to reduce the current flow through the load.

The advantages of a series regulated power supply include:

  • Good regulation: The output voltage is maintained within a tight range, even when the load current varies.
  • Low noise: The series pass transistor acts as a low-pass filter, reducing the noise on the output voltage.
  • Fast response time: The control circuit can quickly adjust the gate voltage of the series pass transistor to maintain the desired output voltage.

The disadvantages of a series regulated power supply include:

  • Low efficiency: The series pass transistor dissipates power, which reduces the efficiency of the power supply.
  • Limited output current: The series pass transistor can only handle a limited amount of current, which limits the output current of the power supply.

Series regulated power supplies are commonly used in applications where good regulation and low noise are required, such as in audio amplifiers and laboratory power supplies.