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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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