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Electronic Circuits

Electronic Circuits. POWER SUPPLIES. Electronic Circuits. INTRODUCTION. The System Half-Wave Rectification Full-Wave Rectification RMS to Average Filters Multipliers Ripple and Regulation Zener Regulator. Circuit A. Circuit B. Power Supply. Circuit C. Electronic Circuits.

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Electronic Circuits

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  1. Electronic Circuits POWER SUPPLIES

  2. Electronic Circuits INTRODUCTION • The System • Half-Wave Rectification • Full-Wave Rectification • RMS to Average • Filters • Multipliers • Ripple and Regulation • Zener Regulator

  3. Circuit A Circuit B Power Supply Circuit C Electronic Circuits The power supply energizes the other circuits in a system. Thus, a power supply defect will affect the other circuits.

  4. Circuit A Circuit B ac Power Supply Circuit C Electronic Circuits dc dc dc Most line operated supplies change ac to dc.

  5. The cathode makes this the positive end of the load. ac Half-wave pulsating dc Electronic Circuits + + 0 0 - - A series rectifier diode changes ac to dc.

  6. The cathodes make this the positive end of the load. Electronic Circuits + 0 Full-wave pulsating dc + - 0 ac - Two diodes and a transformer provide full-wave rectification.

  7. Electronic Circuits Only half of the transformer secondary conducts at a time. VLOAD is equal to one-half the total secondary voltage. C.T. VTOTAL ½ VTOTAL

  8. Electronic Circuits + + ac 0 0 - Full-wave pulsating dc - The bridge circuit eliminates the need for a transformer.

  9. Electronic Circuits + + ac 0 Full-wave pulsating dc 0 - - Reversing the diodes produces anegativepower supply.

  10. Electronic Circuits Power Supply Review Most line-operated power supplies change ac to ________. dc A single diode achieves ________ -wave rectification. half Two diodes and a center-tapped transformer provide ________ -wave rectification. full four A bridge rectifier uses ________ diodes. The positive end of the load is the end in contact with the diode ________. cathodes

  11. ac Vac Vdc Vac Vac Vdc Vdc Ignoring diode loss, the average dc is 45% of the ac input for half-wave. Converting rms to average

  12. Vac Vdc Vac Vdc Ignoring diode loss, the average dc is 90% of the ac input for full-wave. ac

  13. +200 V 0 V -200 V 20 ms 40 ms 0 ms 3 f 120 V 60 Hz Three-phase rectification is used in commercial, industrial and vehicular applications. Full-wave, 3 f bridge Vdc = 1.35 x Vrms = 162 V

  14. Three-phase rectifier output 200 160 120 Vdc = 1.35 x Vrms = 162 V Volts 80 40 0 20 30 40 0 10 Time in milliseconds

  15. Review Electronic Circuits The average dc voltage with half-wave is equal to ______ of the ac voltage. 45% The effective ac voltage in a two-diode, full-wave rectifier is _______ of the secondary voltage. half The average dc voltage with a full-wave rectifier is _________ of the effective ac voltage. 90% The average dc voltage with a bridge rectifier is equal to ________ of the ac voltage. 90% The average dc voltage with a 3 f bridge rectifier is equal to ________ of the ac voltage. 135%

  16. Filter capacitor Discharge VP ac Charge A relatively large filter capacitor will maintain the load voltage near the peak value of the waveform. Electronic Circuits + 0 -

  17. VP Electronic Circuits Discharge time is less. + ac 0 - Full-wave is easier to filter since the discharge time is shorter than it is for half-wave rectifiers.

  18. Vac Vdc ac Adding a filter capacitor increases the dc output voltage. Vac Vdc Ignoring diode loss and assuming a large filter, the dc output is equal to the peak value for both half-wave and full-wave.

  19. Vac Vdc Vac Vdc Ignoring diode loss and assuming a large filter, the dc output is equal to the peak value for both half-wave and full-wave. ac

  20. Vac Vdc ac Vac Vdc Ignoring diode loss and assuming large filters, the dc output is twice the peak ac input. Full-wave doubler

  21. The charge on C1 adds to the ac line voltage and C2 is charged to twice the peak line value. C1 is charged. C1 ac C2 Electronic Circuits Half-wave voltage doubler

  22. Electronic Circuits Review (Ignore diode loss and assume a light load for this quiz.) The dc output in a well-filtered half-wave supply is _____ of the ac input. 141% The dc output in a well-filtered full-wave supply is _____ of the ac input. 141% The dc output in a well-filtered half-wave doubler is _____ of the ac input. 282% The dc output in a well-filtered full-wave doubler is _____ of the ac input. 282%

  23. Electronic Circuits Vac Vdc An ideal dc power supply has no ac ripple. ac ripple = 0% Vac Vdc

  24. ac 1.32 Vac ac ripple = 12 Vdc Electronic Circuits Vac Vdc x 100% = 11 % Real power supplies have some ac ripple. Vac Vdc

  25. The voltage does not change. Vac Vdc Electronic Circuits An ideal power supply has perfect voltage regulation.

  26. VFL 1 V x 100 % = 12 V ac Vac Vac Vdc Vdc Electronic Circuits DV x 100 % Voltage Regulation = = 8.33 % The output of a real supply drops under load.

  27. I V Electronic Circuits Reverse Bias in Volts 6 2 4 8 10 0 12 5 10 Reverse Current in mA 15 Vrev 20 25 30 35 The voltage across a conducting zener is relatively constant.

  28. Vac Vac Vdc Vdc If the zener stops conducting, the regulation is lost. Electronic Circuits Vac A shunt zener diode can be used to regulate voltage. Vdc ac

  29. Electronic Circuits Review The voltage regulation of an ideal power supply is ___________. 0% The ac ripple output of an ideal power supply is ___________. 0% V in a real power supply should be as ___________ as is feasible. small The ac component of an ideal dc power supply should be as ________ as is feasible. small A device that is commonly used to regulate voltage is the ________ diode. zener

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