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Difficulty: MediumCapacitors

In a linear DC power supply circuit, a technician places a smoothing filter capacitor in parallel with the load resistor following a bridge rectifier. What primary function does this capacitor perform in this circuit?

  1. A
    It converts the oscillating alternating current input directly into pulsating direct current.
  2. B
    It stores energy in a magnetic field to maintain a continuous, uninterrupted current flow.
  3. It charges during peak rectified voltage and releases stored electrical energy when voltage falls, reducing ripple voltage.Answer
  4. D
    It acts as a low-resistance conductor to continuously dissipate excess DC voltage into ground.

Answer

It charges during peak rectified voltage and releases stored electrical energy when voltage falls, reducing ripple voltage.
A parallel filter capacitor functions as an electrostatic energy reservoir across the load. During peak outputs from the rectifier, the capacitor absorbs electrical charge. As the pulsating rectified input falls toward zero, the capacitor supplies stored energy to the load, filling the troughs between pulses and significantly attenuating the unwanted AC ripple voltage.

Step-by-Step Solution

1
Identify the component and its circuit role after the rectifier stage.
The component is a capacitor placed in parallel with the DC load resistor as a power supply filter.
The output of a rectifier consists of pulsating DC with substantial AC ripple that must be smoothed into a steady DC voltage level.
2
Analyze the electrostatic charge and discharge mechanism of the capacitor across the voltage cycle.
The capacitor quickly charges to peak output voltage during the rising edge of each rectified pulse, then discharges its stored charge into the load when the rectifier output drops below the capacitor voltage.
This continuous charge-discharge cycle fills in the valleys between rectified pulses, stabilizing the output voltage and minimizing ripple.

Key Concept

Capacitive filtering and ripple voltage reduction in DC power supplies
Estimated Time:1m 0s
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Topics

Capacitors

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