DC Power Supply Concepts Quiz

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Questions and Answers

What percentage of electronic equipment is powered from low voltage DC supplies?

95% (correct)

50%

85%

70%

What is the primary function of a transformer in a DC power supply?

Regulates voltage

Converts DC to AC

Steps down AC voltage (correct)

Stores energy

Which characteristics do electronic components require from a DC supply?

High noise and low regulation

Well regulated and low noise (correct)

Mixed AC and DC characteristics

Poor response to load changes

What is commonly used to convert AC mains into low voltage DC supplies?

Power supply system Signup and view all the answers

Which of the following concepts is crucial for the operation of a regulated power supply?

Voltage Regulation Signup and view all the answers

What is the typical input AC voltage for many DC power supplies?

220 V RMS Signup and view all the answers

Which type of voltage regulator is typically used in a basic DC power supply?

Zener diode regulator Signup and view all the answers

What is not a requirement for a DC power supply in electronic components?

High frequency output Signup and view all the answers

What does a diode rectifier do in the DC power supply circuit?

It provides a full-wave rectified voltage Signup and view all the answers

Which type of power supply maintains a steady output voltage despite changes in input or load?

Ideal Power Supply Signup and view all the answers

What is the main difference between an ideal and a real DC power supply?

An ideal supply has no output voltage variation under load Signup and view all the answers

How is line regulation defined in the context of DC power supplies?

As the percentage change in output voltage for a change in input voltage Signup and view all the answers

What is the purpose of a capacitor filter in a DC power supply?

To smooth out the voltage after rectification Signup and view all the answers

Which component can keep the DC voltage constant despite changes in input or load conditions?

Regulator Circuit Signup and view all the answers

What is the typical RMS value of AC voltage connected to the transformer in a DC power supply?

220 V Signup and view all the answers

What is line regulation expressed as in the example provided?

0.333%/V Signup and view all the answers

How is load regulation defined?

Percentage change in output voltage for a given change in load current Signup and view all the answers

Based on the examples, what would the line regulation be if the output decreased by 0.5 V?

0.833%/V Signup and view all the answers

From the given data, what is the change in output voltage from no-load to full-load for load regulation?

0.25 V Signup and view all the answers

Which value represents the nominal output voltage in the line regulation example?

15 V Signup and view all the answers

What does the load regulation percentage measure?

Difference in voltage between no-load and full-load Signup and view all the answers

What does a lower load regulation percentage indicate?

Higher stability in output voltage under varying loads Signup and view all the answers

If a voltage regulator outputs 10 V under full-load, and 10.5 V under no-load, what is the load regulation percentage?

1.75% Signup and view all the answers

What is the purpose of applying the amplified difference voltage to the transistor Q1?

To make the load voltage equal to the reference Signup and view all the answers

Which series of integrated circuit voltage regulators is designed for fixed positive outputs?

78xx Signup and view all the answers

How is the output voltage determined for the fixed linear regulator in the 78xx series?

By the last two digits in the part number Signup and view all the answers

Which of the following describes a negative linear regulator?

7905 Signup and view all the answers

What components are integrated within an IC voltage regulator?

Voltage reference, error detector, and control unit Signup and view all the answers

What is a common example of a variable voltage integrated circuit voltage regulator?

LM317 Signup and view all the answers

Which statement about the 79xx series is correct?

It is designed for negative voltage outputs. Signup and view all the answers

What does the configuration of an integrated circuit voltage regulator primarily depend on?

The required output stability Signup and view all the answers

How does the output sample circuit affect the linear voltage regulator's performance?

It senses changes in the output voltage Signup and view all the answers

What is the function of the pass transistor in a series linear voltage regulator?

To maintain a constant output voltage by varying its resistance Signup and view all the answers

What role does the error detector play in a series linear voltage regulator?

It compares the sample voltage to a reference voltage Signup and view all the answers

Which component is essential for amplifying the difference between the reference and sensed voltage in a linear voltage regulator?

Operational amplifier (op-amp) Signup and view all the answers

What does the resistive voltage divider do in a series linear voltage regulator?

Senses any change in the output voltage Signup and view all the answers

What is a characteristic of series linear voltage regulators compared to shunt linear regulators?

They maintain constant voltage regardless of load Signup and view all the answers

What is the adjustable output voltage range for the LM317 regulator?

1.2 V to 37 V Signup and view all the answers

What distinguishes linear power supplies from switched power supplies?

Linear power supplies typically generate less noise Signup and view all the answers

Which of the following describes the primary function of a linear power supply?

To provide a stable DC output voltage Signup and view all the answers

Which component is used for output voltage adjustment in the LM337?

External fixed resistor R1 and variable resistor R2 Signup and view all the answers

What is the maximum output current the LM317 can provide?

1.5 A Signup and view all the answers

What is the significance of the current IADG in the LM317 regulator?

It can be neglected as it is small (50 µA). Signup and view all the answers

Which of the following statements is true regarding both LM317 and LM337?

Both can have their output voltage adjusted with external resistors. Signup and view all the answers

Which resistor values modify the output voltage of the LM317 regulator?

Both R1 and R2 affect the output voltage. Signup and view all the answers

What is the primary difference in the output voltage ranges of the LM317 and LM337?

LM317 provides a positive voltage output while LM337 provides a negative voltage output. Signup and view all the answers

Study Notes

ECE121: Electronics (1) - Lecture 1: Regulated Power Supply

Course: Electronics (1)
Lecture: Regulated Power Supply
Lecturer: Dr. Haitham El-Hussieny
University: Benha University
Semester: Spring 2017

Lecture Outline

Introduction
Concept of Voltage Regulation
A Zener-Regulated DC Power Supply
Basic Linear Voltage Regulator
Integrated Circuit Voltage Regulators

Introduction (DC Power Supply)

Approximately 95% of electronic equipment runs on low-voltage DC supplies.
Power sources can be batteries or AC-to-DC power supplies.
Electronic components need a well-regulated DC supply with low noise and rapid response to load changes.
Components of a DC power supply:
- Transformer: steps down AC voltage to desired DC output level (typically 220 V RMS)
- Rectifier: produces a full-wave rectified voltage
- Filter: smooths the rectified voltage into a DC voltage
- IC Regulator: ensures a stable DC output voltage despite input or load variations
Ideal vs. Real DC Regulated Power Supply:
- Ideal: maintains a constant DC output voltage regardless of input voltage or load changes
- Real: output voltage fluctuates with input voltage or load changes

Concept of Voltage Regulation

Line Regulation: The percentage change in output voltage for a given change in input voltage (expressed as %/V).
- Formula: Line regulation = (ΔV_out/V_out) * 100%/ΔV_in
Example: If a power supply's input voltage drops 5V and its output drops 0.25V, the initial output was 15V; the line regulation is 0.333%/V.
Load Regulation: The percentage change in output voltage for a given change in load current (often expressed as a percentage change from no-load to full-load).
- Formula: Load regulation = (V_NL - V_FL)/V_FL * 100%
Example: A regulator with a 12V no-load output that drops to 11.9V under a full load has a load regulation of 0.840%.

A Zener-Regulated DC Power Supply

Zener Diode: Used as a voltage regulator to provide stable reference voltages.
Constant Output Voltage: The zener diode maintains a nearly constant output voltage across its terminals, even with input voltage variations (within limits).
Current Adjustment: Input voltage changes proportionally affect the zener diode current (I_z), thus limiting input voltage variation based on the minimum and maximum current (I_zk and I_zm) the zener can handle.

Basic Linear Voltage Regulator

Series Linear Regulators: Contain a pass transistor in series with the load between the input and output. The output sample circuit monitors changes in the output voltage. The error detector compares these readings with a set reference voltage and adjusts the transistor to maintain the output at a constant value.
Shunt Linear Regulators: Control current instead of voltage to minimize output voltage variations.

Integrated Circuit Voltage Regulators

IC Regulators: Integrate reference voltage, error detector, and control unit into a single package.
Fixed Voltage Regulators (78xx): Positive output voltages, where last two numbers indicate the regulated voltage output
Example: 7805 is a 5V regulator
Fixed Negative Voltage Regulators (79xx): Negative output voltages; last two numbers designate the regulated voltage.
Variable Voltage Regulators (LM317/LM337): Positive and negative voltage adjustments, depending on external resistor values
Examples: LM317, LM337

Power Supply Project

Students will select an IC regulator, simulate it using Proteus, and design a variable power supply.
Deliverables are due on specific dates.

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Description

Test your knowledge on key concepts related to DC power supplies, including the workings of transformers, rectifiers, and voltage regulation. This quiz will cover the essential characteristics required from a DC supply and the components involved in converting AC to DC power.