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Electronic Circuits POWER SUPPLIES.

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Presentation on theme: "Electronic Circuits POWER SUPPLIES."— Presentation transcript:

1 Electronic Circuits POWER SUPPLIES

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

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

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

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

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

7 Electronic Circuits VLOAD is equal to one-half the total secondary
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 - Full-wave pulsating dc - The bridge circuit eliminates the need for a transformer.

9 Reversing the diodes produces a negative power supply.
Electronic Circuits + + ac Full-wave pulsating dc - - Reversing the diodes produces a negative power supply.

10 Electronic Circuits Power Supply Review dc half full four cathodes
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 A bridge rectifier uses ________ diodes. four The positive end of the load is the end in contact with the diode ________. cathodes

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

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

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

15 Review Electronic Circuits 45% half 90% 90% 135%
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 Electronic Circuits VP Filter Discharge capacitor + ac Charge -
A relatively large filter capacitor will maintain the load voltage near the peak value of the waveform. + Charge ac -

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

18 Adding a filter capacitor increases the dc output
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. Adding a filter capacitor increases the dc output voltage. Vac Vdc ac

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 Vac Vdc

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

21 Electronic Circuits Half-wave voltage doubler
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 Half-wave voltage doubler

22 (Ignore diode loss and assume a light load for this quiz.)
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.

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

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

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

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

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

29 Review Electronic Circuits 0% 0% small small zener
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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