Lecture 6 Diode Rectifier

8/3/2019 Lecture 6 Diode Rectifier

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RECTIFIER

Tuesday, May 01, 2012Dr. RS

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Half-Wave rectifier


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Block diagram of a rectifier and a dc power supply with a load.

Thomas L. Floyd

Electronic Devices, Electron Flow Version, 5e


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Half-wave rectifier operation. The diode is considered to be ideal.

Thomas L. Floyd



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The effect of the barrier potential on the half-wave

rectified output voltage is to reduce the peak value ofthe input by about 0.7 V.

Thomas L. Floyd


Copyright 2005 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved.


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Vp

0

-VP

2

Vi(t)

t

VD

Vp - VD

0 2

Vo(t)

t


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Figure 23 Average value of the half-wave rectified signal.

Thomas L. Floyd





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Average value of HWR

V

cos2

V

d0dsinV2

1

dtVT

1V

P

0

P

2

0 p

T

0DC


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RMS Value of HWR

4

V

sin4

V

d2cos12

1

2

Vd

2

V

d0dsinV2

1

dtVT

1V

P

0

P

P

0

P

2

0

2

p

T

0

2

rms

2

2

0

2

2

2

2

2

22

1

sin


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VDC

Vrms

t0

t1

t2

t3

Vp

VO

t


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The PIVoccurs at the peak of each half-cycle of the input voltagewhen the diode is reverse-biased. In this circuit, the PIV occurs

at the peak of each negative half-cycle.

Thomas L. Floyd





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Half-wave rectifier with transformer-coupled input voltage.

Thomas L. Floyd





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Thomas L. Floyd





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Center-tapped Full-wave Rectifier


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Figure 211 Full-wave rectification.

Thomas L. Floyd





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Average Value

V2

cos

V

dsinV

1

dtVT

1V

P

0

P

0p

T

0DC


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RMS Value

2

V

sin2

V

d2cos12

1

V

dsinV

1

dtVT

1V

P

0

P

P

0

2

p

T

0

2

rms

2

2

0

2

2

2

221


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Figure 213 A center-tapped full-wave rectifier.

Thomas L. Floyd




B i ti f t t d f ll tifi N t th t th t th h th


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Basic operation of a center-tapped full-wave rectifier. Note that the current through theload resistor is in the same direction during theentire input cycle, so the output voltage

always has the same polarity.

Thomas L. Floyd





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Center-tapped full-wave rectifier with a transformer turns ratio of 1.Vp(pri) is the peak value of the primary voltage.

Thomas L. Floyd





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Center-tapped full-wave rectifier with a transformer turns ratio of 2.

Thomas L. Floyd





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Diode reverse voltage (D2 shown reverse-biased and D1 shown forward-biased).

Thomas L. Floyd





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Full-Wave Bridge Rectifier
http://lecture%205%20bridge%20rectifier.ppt/http://lecture%205%20bridge%20rectifier.ppt/http://lecture%205%20bridge%20rectifier.ppt/http://lecture%205%20bridge%20rectifier.ppt/


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Figure 223

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Dr. RS Tuesday, May 01, 2012


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Figure 220 Operation of a bridge rectifier.

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Figure 221 Bridge operation during a positive half-cycle of the primary and secondary voltages.

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Vp

0

-VP

2

Vi(t)

t

Vp - VD

0 2

Vo(t)

t

27Dr. RS Tuesday, May 01, 2012

i k l d d d b d f


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Figure 222 Peak inverse voltages across diodes D3 andD4 in a bridge rectifierduring the positive half-cycle of the secondary voltage.

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Figure 224 Power supply filtering.

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Figure 230

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Figure 225 Operation of a half-wave rectifier with a capacitor-input filter. The current indicates charging or discharging of the capacitor.

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Figure 226 Half-wave ripple voltage (green line).

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Figure 227 The frequency of a full-wave rectified voltage is twice that of a half-wave rectified voltage.

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Figure 228 Comparison of ripple voltages for half-wave and full-wave rectified voltages with the same filter capacitor and load and derived from thesame sinusoidal input voltage.

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Vr

and VDC determine the ripple factor.

Vp(rect) : unfiltered peak rectified voltage

Vr(pp) : peak to peak ripple voltage

VDC : average value of ripple voltage

rhwr Vr(pp )

VDC

1

2 3fRLC

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rfwr Vr(pp )

VDC

1

4 3fRLC


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Effects of RL and C

Tuesday May 01 2012Dr RS

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C=1000F C=470F

C=100F

R=1500

R=1000

R=500

(a) RLfixed (b) C fixed

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Lecture 6 Diode Rectifier