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Power Supply Circuits and Voltage Regulation Flashcards

7 cards from real ISCET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the primary purpose of a filter capacitor placed after a rectifier in a DC power supply?

    Answer: To smooth the pulsating DC output by reducing ripple

    A filter capacitor charges to the peak voltage and slowly discharges between peaks, reducing the ripple and smoothing the pulsating DC into a more stable output.

  2. A half-wave rectifier is connected to a 120V RMS transformer secondary. What is the approximate average DC output voltage (ignoring diode drop)?

    Answer: 54V

    For a half-wave rectifier, Vavg = 0.318 × Vpeak = 0.318 × (120 × 1.414) ≈ 0.318 × 169.7 ≈ 54V.

  3. In a full-wave bridge rectifier, how many diodes conduct simultaneously during each half-cycle of the AC input?

    Answer: Two

    In a bridge rectifier, current flows through two diodes in series during each half-cycle — one on the top rail and one on the bottom rail.

  4. The ripple factor (r) of a power supply filter is best described as:

    Answer: The ratio of RMS ripple voltage to average DC output voltage

    Ripple factor r = Vrms(ripple) / Vdc, and a lower value indicates a better-filtered, more stable DC output.

  5. A 7812 three-terminal linear voltage regulator produces which regulated output voltage?

    Answer: 12V

    The 78XX series regulators output a voltage equal to the last two digits; the 7812 outputs a fixed +12V regulated output.

  6. What is the minimum PIV (Peak Inverse Voltage) rating required for diodes in a full-wave bridge rectifier with a 24V RMS transformer secondary?

    Answer: 33.94V

    In a bridge rectifier, each diode must withstand a reverse voltage equal to Vpeak = 1.414 × 24V ≈ 33.94V.

  7. Which type of voltage regulator uses a zener diode connected in parallel with the load as its primary regulation element?

    Answer: Shunt regulator

    A shunt regulator places the regulation element (zener diode or transistor) in parallel with the load to clamp the output voltage at a fixed level.