ECE121: Electronics (1) - Regulated Power Supply

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Questions and Answers

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

  • 85%
  • 95% (correct)
  • 75%
  • 50%

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

  • 220 V RMS (correct)
  • 110 V RMS
  • 440 V RMS
  • 330 V RMS

Which component of a DC power supply converts AC mains into low voltage DC supplies?

  • Transformer
  • Zener Diode
  • Voltage Regulator
  • Rectifier (correct)

What characteristics must a DC power supply provide for electronic components?

<p>Well regulated and low noise (A)</p> Signup and view all the answers

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

<p>To step down AC voltage (D)</p> Signup and view all the answers

Which of the following describes the role of a Zener-regulated DC power supply?

<p>It provides voltage regulation. (B)</p> Signup and view all the answers

What type of voltage regulator is commonly used in integrated circuits?

<p>Basic Linear Voltage Regulator (A)</p> Signup and view all the answers

What is likely NOT a requirement for a DC power supply used in electronics?

<p>High ripple voltage (B)</p> Signup and view all the answers

What is the purpose of a transformer in a DC power supply?

<p>To step down AC voltage to a lower level for DC output (A)</p> Signup and view all the answers

What type of rectification is provided by the diode in a DC power supply?

<p>Full-wave rectification (B)</p> Signup and view all the answers

Which component is primarily used for filtering the voltage in a basic DC power supply?

<p>Capacitor (A)</p> Signup and view all the answers

What distinguishes an ideal DC power supply from a real DC power supply?

<p>An ideal power supply provides constant voltage despite changes (B)</p> Signup and view all the answers

How is line regulation defined in the context of voltage regulation?

<p>The change in output voltage relative to input voltage change (A)</p> Signup and view all the answers

What happens to the output voltage of a real power supply when the load changes?

<p>It changes under load or line changes (C)</p> Signup and view all the answers

Which of the following voltage regulation components is typically used in a Zener-regulated power supply?

<p>Zener diode (B)</p> Signup and view all the answers

What is the initial function of the basic capacitor filter in a DC power supply?

<p>To smooth out the rectified voltage (C)</p> Signup and view all the answers

What is the primary control element in a series linear voltage regulator?

<p>A pass transistor (D)</p> Signup and view all the answers

What role does the output sample circuit play in a series linear voltage regulator?

<p>It senses changes in output voltage. (C)</p> Signup and view all the answers

How does the error detector function in a series linear voltage regulator?

<p>By comparing the sample voltage with a reference voltage. (C)</p> Signup and view all the answers

Which component is used to sense changes in output voltage in a series linear voltage regulator?

<p>A resistive voltage divider (D)</p> Signup and view all the answers

What is the main goal of a series linear voltage regulator?

<p>To maintain a constant output voltage (C)</p> Signup and view all the answers

In a series linear voltage regulator, what happens when the output voltage decreases?

<p>The error detector activates the control element to compensate. (D)</p> Signup and view all the answers

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

<p>To provide a stable output voltage (D)</p> Signup and view all the answers

What type of circuit amplifies the difference voltage in a series linear voltage regulator?

<p>A differential amplifier circuit (D)</p> Signup and view all the answers

Which power supply type is a series linear voltage regulator categorized under?

<p>Regulated power supply (C)</p> Signup and view all the answers

How does the zener diode maintain a nearly constant output voltage?

<p>By allowing input voltage variations within limits (A)</p> Signup and view all the answers

What determines the limitations on input voltage variation for a zener diode?

<p>The minimum and maximum current values (C)</p> Signup and view all the answers

What happens to the zener current (IZ) as input voltage (VIN) changes?

<p>IZ changes proportionally with VIN (A)</p> Signup and view all the answers

Under which condition does the zener diode operate effectively?

<p>Within specified current limits (C)</p> Signup and view all the answers

What is one of the key characteristics of a zener-regulated DC power supply?

<p>It provides stable reference voltages (C)</p> Signup and view all the answers

Which configuration of a zener diode is important for operation?

<p>Reverse-biased configuration (C)</p> Signup and view all the answers

What happens to output voltage in a zener-regulated power supply when the load increases?

<p>Output voltage remains nearly constant (C)</p> Signup and view all the answers

What is the maximum output voltage that the LM317 regulator can provide?

<p>37 V (C)</p> Signup and view all the answers

What type of current can the LM317 provide to a load?

<p>1.5 A (B)</p> Signup and view all the answers

Which component is essential for voltage adjustment in both LM317 and LM337?

<p>Variable Resistor R2 (B)</p> Signup and view all the answers

What can be neglected when calculating the output current for LM317 and LM337?

<p>IADG, which is small 50 µA (D)</p> Signup and view all the answers

How does the output voltage range of the LM337 compare to that of the LM317?

<p>Similar range but with only negative values (C)</p> Signup and view all the answers

What is the role of the external fixed resistor R1 in both LM317 and LM337 circuits?

<p>To assist in voltage adjustment (D)</p> Signup and view all the answers

What will the output voltage be if R1 and R2 are set to their minimum values for the LM317?

<p>1.2 V (D)</p> Signup and view all the answers

What is the function of the amplified difference voltage in a basic op-amp series regulator?

<p>To maintain output voltage at a reference level (B)</p> Signup and view all the answers

What do the last two digits in the part number of a fixed voltage linear regulator indicate?

<p>The output voltage (A)</p> Signup and view all the answers

Which of the following is a feature of integrated circuit voltage regulators?

<p>They contain the reference voltage, error detector, and control unit in one package (A)</p> Signup and view all the answers

Which IC series is used for positive output linear regulation?

<p>78xx (D)</p> Signup and view all the answers

What characterizes the 79xx series voltage regulators?

<p>They are fixed negative voltage regulators (C)</p> Signup and view all the answers

What is a common application of a Zener-regulated DC power supply?

<p>To provide a stable reference voltage (C)</p> Signup and view all the answers

What is the primary component of a basic linear voltage regulator?

<p>Transistor (C)</p> Signup and view all the answers

Which of the following describes variable voltage integrated circuit regulators?

<p>They do not have a fixed output voltage (A)</p> Signup and view all the answers

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Flashcards

Diode Rectifier's Role

The AC voltage is converted to DC voltage.

Transformer's Function

The voltage is reduced from the initial source voltage to the desired DC voltage.

Capacitor Filter's Purpose

A capacitor filter smooths out the ripples in the DC voltage, providing a more stable output.

Role of Regulator Circuit

The regulator circuit maintains a constant DC voltage, even when input or load conditions change.

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Line Regulation

The percentage change in the output voltage for a given change in the input voltage.

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Ideal Power Supply

An ideal power supply provides a constant DC voltage regardless of changes in input or load.

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Real Power Supply

A real power supply's output voltage is not constant and changes with varying input or load conditions.

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Line Regulation Definition

It measures the percentage change in output voltage due to a change in the input voltage. It is expressed in units of (%/V).

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DC Power Supply Importance

DC power supplies are essential for powering most electronic devices and ensure stable and reliable operation.

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Concept of Voltage Regulation

A regulated DC power supply maintains a constant output voltage regardless of changes in load or input voltage.

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Regulated DC Power Supply

A regulated DC power supply involves components that ensure constant output voltage, even with variations.

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Zener Diode Function

A Zener diode is a crucial component in regulated DC power supplies. It maintains a constant voltage across it, even when the current changes.

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Zener Diode in Regulation

Zener diodes are used to regulate DC power by creating a fixed voltage reference. This reference is essential for maintaining a steady output voltage from the power supply.

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Zener Regulated DC Power Supply

A Zener-regulated DC power supply utilizes a Zener diode to regulate the output voltage. It effectively provides a stable DC voltage output.

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Basic Linear Voltage Regulator

A basic linear voltage regulator utilizes a transistor and a reference voltage to regulate the output. It effectively stabilizes the output voltage.

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Integrated Circuit Voltage Regulators

Integrated circuit voltage regulators are compact chips that provide a stable DC voltage output. They offer convenience and efficiency.

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Series Linear Voltage Regulator

A type of voltage regulator that uses a pass transistor in series with the load to control the output voltage.

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Output Sample Circuit

A circuit that monitors the output voltage and sends feedback to the control element.

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Error Detector

This compares the output sample voltage with a reference voltage.

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Pass Transistor

The control element in a series linear voltage regulator, often a transistor.

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Reference Voltage

The desired output voltage set by the regulator.

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Error Voltage

The voltage difference between the reference voltage and the output sample voltage.

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Op-amp Circuit

This circuit amplifies the error voltage to control the pass transistor.

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Resistive Voltage Divider

This circuit uses resistors to measure changes in the output voltage.

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Voltage Regulator

A device that ensures a stable output voltage despite changes in input voltage or load.

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Linear Voltage Regulator

A type of voltage regulator where the output voltage remains constant even when the input voltage or load changes.

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Fixed Positive Linear Regulator (78xx)

A type of integrated circuit voltage regulator that provides a fixed positive output voltage, typically indicated by the last two digits in the part number (e.g., 7805 for 5V).

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Fixed Negative Linear Regulator (79xx)

A type of integrated circuit voltage regulator that provides a fixed negative output voltage, also indicated by the last two digits in the part number (e.g., 7905 for -5V).

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Variable Voltage Regulator

An integrated circuit voltage regulator that can provide a variable output voltage, allowing for adjustable voltage outputs.

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Positive and Negative Output Variable Voltage Regulators (LM317 and LM337)

A type of variable voltage regulator that can provide both positive and negative output voltages, offering more flexibility.

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Zener Diode Voltage Regulation

A zener diode can act as a voltage regulator, ensuring a stable output voltage even when the input voltage changes within a certain range.

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Zener Diode Output Stability

The zener diode maintains a nearly constant output voltage across its terminals, even when input voltage varies within limits.

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Zener Diode Current Limits

The zener diode operates within specific current limits, represented by IZK (minimum current) and IZM (maximum current).

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Zener Diode Operation: No-Load

When the load is disconnected (no-load), the zener diode's current IZ is defined by the input voltage and the series resistance.

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Zener Diode Operation: Full-Load

When a load is connected, the zener diode and load share the current. The load current IL reduces the zener current IZ.

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Zener Diode Voltage Regulation Limits

The zener diode's ability to regulate voltage is limited by its current limits (IZK and IZM). The input voltage variation must be within a range that allows the zener to operate within these limits.

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Zener Power Supply: Voltage and Current Control

By adjusting the series resistor (R) in a zener-regulated power supply, you can control the output voltage and current.

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LM317: Positive Variable Regulator

A type of integrated circuit voltage regulator designed to output a positive adjustable voltage.

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LM337: Negative Variable Regulator

A type of integrated circuit voltage regulator designed to output a negative adjustable voltage.

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R1 (External Fixed Resistor)

An external resistor used with the LM317 or LM337 to set the desired output voltage. It, along with R2, determines the output voltage.

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R2 (External Variable Resistor)

An external variable resistor used with the LM317 or LM337 to adjust the output voltage. It, along with R1, determines the output voltage.

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Minimum Output Voltage

The minimum output voltage possible for the LM317 or LM337.

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Maximum Output Voltage

The maximum output voltage possible for the LM317 or LM337.

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Maximum Output Current

The maximum current that can flow through the LM317 or LM337 to the load.

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Internal Current (IADG)

A small current used internally in the LM317 or LM337 which can be neglected.

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Study Notes

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

  • The course is ECE121: Electronics (1), lecture 1 covers regulated power supplies
  • The lecturer is Dr. Haitham El-Hussieny
  • The institution is Benha University, Faculty of Engineering (Shoubra)
  • The lecture date is Spring 2017

Lecture Outline

  • Introduction to DC power supplies
  • Concept of voltage regulation
  • Zener-regulated DC power supply
  • Basic linear voltage regulator
  • Integrated circuit voltage regulators

Introduction

  • Approximately 95% of electronic devices use low-voltage DC power supplies
  • Power sources can be batteries or AC-to-DC converters
  • Electronic components need well-regulated DC power with low noise and fast response to load changes

Components of DC Power Supplies

  • AC (typically 220 V RMS) is passed through a transformer to lower the voltage to the desired DC output level
  • A rectifier converts AC to pulsating DC
  • A filter smooths the pulsating DC to a smoother DC voltage
  • A regulator maintains a constant DC voltage despite input or load changes

Ideal vs. Real DC Regulated Power Supply

  • Ideal power supplies maintain a constant DC voltage regardless of input voltage or load changes
  • Real power supplies have output voltages that change with load or input variations

Concept of Voltage Regulation

  • Line regulation is the percentage change in output voltage for a given change in input voltage
    • Line regulation = [(ΔVout / Vout) * 100%] / ΔVin (expressed in % / V)
  • Example: If the input voltage decreases by 5V and the output voltage by 0.25V, with a nominal output of 15V, the line regulation is 0.333%/V

Load Regulation

  • Load regulation is the percentage change in output voltage for a given change in load current
    • Load regulation = [(VNL - VFL) / VFL] * 100% (expressed as a percentage, where VNL is no-load voltage and VFL is full-load voltage)
  • Example: If the no-load voltage is 12V and the full-load voltage is 11.9V, the load regulation is 0.840%

A Zener-Regulated DC Power Supply

  • Zener diodes can be used as voltage regulators to provide stable reference voltages
  • Output voltage remains nearly constant despite input voltage changes (within limits)
  • Output voltage changes proportionally with input voltage changes, but output voltage changes stay within limits

Basic Linear Voltage Regulator

  • Series voltage regulators use a pass transistor in series with the load
  • Output circuit senses output voltage changes
  • Error detector compares sample voltage with a reference voltage, causing the control element to compensate to maintain constant output voltage
  • Example: A resistive voltage divider, and an op-amp to adjust

Integrated Circuit Voltage Regulators

  • IC regulators combine the reference voltage, error detector, and control units in one package
  • Types: fixed voltage (e.g., 78xx series for positive, 79xx for negative) and variable voltage (e.g., LM317 for positive, LM337 for negative)
  • The last two digits in the part number denote the output voltage (e.g., 7805 is a 5V regulator)
  • LM317 and LM337 are variable voltage regulators; external components set output voltage, allow adjustments from 1.2V to 37V

Power Supply Project

  • Students are required to individually simulate a 12V power supply using IC regulators in Proteus and submit by a specific date.
  • Each team should simulate a variable power supply (+ve or -ve) and submit by another date

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