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Voltage Regulation Basics: Discrete and Integrated Voltage Regulators

This chapter explains the basic concepts of voltage regulation, including rectification, filtering, and voltage regulation, in both discrete and integrated voltage regulators. It covers topics such as line regulation, load regulation, types of regulators, linear IC voltage regulators, adjustable IC regulators, and switching voltage regulators.

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Voltage Regulation Basics: Discrete and Integrated Voltage Regulators

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  1. Chapter 21 Discrete and Integrated Voltage Regulators

  2. Basic Power Supply • The rectifier converts the ac line input to pulsating dc. • The filter reduces the variations in the rectifier output. • The voltage regulator reduces the ripple (variations) in the filter output voltage.

  3. Voltage Regulation • The ideal voltage regulator maintains a constant load voltage despite predictable variations in line voltage and load demand.

  4. Line Regulation • Line regulation – The change in regulator output voltage that occurs per unit change in input voltage. • The lower its line regulation rating, the higher the quality of a voltage regulator. • For the ideal voltage regulator, line regulation = 0.

  5. Line Regulation Units • mV/V – The change in output voltage (in microvolts) per 1 V change in input voltage. • ppm/V – Parts per million per volt. Another way of expressing microvolts per volt. • %/V – The percentage change in output voltage per 1 V change in the input voltage. • % – The total percentage of change in output voltage that can occur over the rated range of input voltages. • mV (or mV) – The actual change in output voltage that may occur over the rated range of input voltages.

  6. Load Regulation • Load regulation – A rating that indicates the change in regulator output voltage per unit change in load current. • The lower its load regulation rating, the higher the quality of a voltage regulator. • For the ideal voltage regulator, load regulation = 0.

  7. Load Regulation Units • mV/mA – The change in output voltage (in microvolts) per 1 mA change in load current. • %/mA – The percentage change in output voltage per 1 mA change in load current. • % – The total percentage of change in output voltage that may occur over the rated range of load current values. • mV (or mV) – The actual change in output voltage that may occur over the rated range of load current values. • W – V/mA, expressed as a resistance. The product of this rating and DIL gives you the corresponding value of DVL.

  8. Types of Regulators • Series regulator – A voltage regulator connected in series with the load. • Shunt regulator – A voltage regulator connected in parallel with the load.

  9. Pass-Transistor Regulator • Pass-transistor regulator – A regulator that uses a series transistor to maintain a constant load voltage.

  10. Darlington Pass-Transistor Regulator • Darlington pass-transistor regulator – A series regulator that uses a Darlington pair in place of a single pass-transistor regulator.

  11. Series Feedback Regulator • Series feedback regulator – A series regulator that uses an error-detection circuit to improve the line and load regulation characteristics of other pass-transistor regulators.

  12. Basic Series Feedback Regulator

  13. Series Feedback Regulator With Short-Circuit Protection

  14. Shunt Feedback Regulator • Shunt feedback regulator – A circuit that uses an error detector to control the conduction of a shunt transistor.

  15. Linear IC Voltage Regulator • Linear IC voltage regulator – A device used to hold the output voltage from a dc power supply relatively constant over a specified range of line and load variations.

  16. Types of Linear IC Regulators • Fixed-positive regulator – A regulator that provides a predetermined +V output. • Fixed-negative regulator – A regulator that provides a predetermined –V output. • Adjustable regulator – A regulator whose output voltage can be set to any value within specified limits. • Dual-tracking regulator – A regulator that provides equal +V and –V outputs.

  17. Linear IC Regulator Ratings • Dropout voltage (VI – VO) – The minimum allowable difference between the input and rated output voltages. • Quiescent current (IB) – The portion of the regulator input current that is not delivered to the load. • Ripple rejection (RR) – The ratio of regulator input ripple to regulator output ripple.

  18. Adjustable IC Regulators • Input/output voltage differential (Vd) – The maximum allowable difference between Vin and Vout for an adjustable IC regulator.

  19. Complete Dual-Polarity Power Supply

  20. Using a Pass-Transistor to Increase Maximum Current

  21. Linear IC Regulator With Short-Circuit Protection

  22. Switching Voltage Regulators • Linear regulator – One designed to provide a continuous path for current between the regulator input and the load. • Switching regulator – One designed so that the current path between the regulator input and the load is not continuous.

  23. Basic Switching Regulator • Power switch – A term used to describe the pass-transistor in a switching regulator.

  24. Pulse-Width Modulation (PWM)

  25. Variable Off-Time Modulation

  26. Switching Regulator Configurations

  27. IC Switching Regulator Circuit

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