How does an increase in input AC voltage impact the output of an unregulated power supply_______________?
Show answer Hide answer
Answer: A. Increases
Explanation
An unregulated power supply lacks any active feedback control circuitry to compensate for fluctuations in the incoming mains voltage. Consequently, any increase in the input alternating current voltage passes directly through the transformer and rectifier stages. This uncompensated transfer results in a proportional increase in the output direct current voltage delivered to the load. Unregulated power supplies typically consist only of a transformer, a diode bridge rectifier, and a simple filter capacitor. Feedback control loops in regulated supplies automatically adjust for input surges to keep output voltages steady. Alternating current mains voltages frequently fluctuate throughout the day based on local grid electrical demand.
Stating that the output decreases contradicts the direct proportional relationship found in simple open loop power supplies. Saying the output remains the same ignores the complete absence of voltage stabilization or feedback regulation circuits. Option D is incorrect because an increase in input AC voltage directly causes the unregulated DC output voltage to rise.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Which description most accurately portrays a Zener diode?
Show answer Hide answer
Answer: C. It is a constant-voltage device
When operating in its reverse breakdown region, a Zener diode maintains an almost constant voltage across its terminals. Even when the current passing through the diode changes significantly, the terminal voltage remains...
Q2. Through which breakdown mechanism does a Zener diode with an extremely narrow depletion layer fail____________?
Show answer Hide answer
Answer: B. Zener
Extremely narrow depletion layers created by heavy doping generate intense internal electric field strengths. These high electric fields facilitate quantum mechanical tunneling, which defines the Zener breakdown mechanis...
Q3. When does a Zener diode maintain an approximately constant load voltage________________?
Show answer Hide answer
Answer: D. Operating in the breakdown region
A Zener diode exhibits a stable and constant terminal voltage only when it is actively operating in its reverse breakdown region. In this specific operational zone, large current changes produce minimal fluctuations in t...
Q4. What portion of an AC supply can an SCR effectively control____________?
Show answer Hide answer
Answer: D. Positive or negative half-cycles
A Silicon Controlled Rectifier is a unidirectional semiconductor switch that can be triggered into conduction during either half cycle. By applying a gate trigger pulse at the correct phase angle, an SCR can control powe...
Q5. What characteristic behavior is associated with the breakdown voltage of a Zener diode?
Show answer Hide answer
Answer: D. It is approximately constant
Within its specified operating limits in reverse breakdown, the voltage across a Zener diode remains nearly constant. Even as current through the diode fluctuates, the terminal voltage changes by only a very small amount...
Q6. What happens to the DC output voltage when the load current drawn from an unregulated power supply rises _____________?
Show answer Hide answer
Answer: B. Decreases
When the load current drawn from an unregulated power supply increases, the internal voltage drops across internal impedances also rise. These internal voltage drops include transformer winding resistance, diode forward...