D.C. Power Supply Block Diagram

DC Power Supply Components and Functions

• The step-down transformer in a DC power supply reduces the voltage of the alternating current (AC) input to a lower voltage.

Rectifier Functions

• The rectifier produces a pulsating DC output.
• A half-wave rectifier circuit makes use of only either positive or negative half-cycles of the supply.
• Diode D1 in the half-wave rectifier circuit conducts during the positive half-cycle and blocks during the negative half-cycle.
• The main difference between the positive and negative half-cycles in a half-wave rectifier circuit is that the diode conducts in one and blocks in the other.

Capacitor Functions

• The high-value reservoir capacitor stores a considerable amount of charge in a DC power supply.

Voltage Regulation

• A component such as a voltage regulator provides a constant output voltage in a DC power supply.
• The zener diode is used to regulate the output voltage.

Rectifier Circuits

• The purpose of the load resistor (RL) in the half-wave rectifier circuit is to provide a path for the current to flow.
• The negative half-cycles in a half-wave rectifier circuit are blocked by the diode.
• An important consideration when selecting a diode for a particular application in a half-wave rectifier circuit is its ability to handle the required voltage and current.
• The peak amplitude of the positive half-cycle pulses across RL produced by the half-wave rectifier circuit is equal to the peak voltage applied to diode D1.

AC to DC Conversion

• The rectifier is the component used to convert alternating current (AC) to direct current (DC) in a DC power supply.