EHB 231 Chap 2 Diode Circuits

8/15/2019 EHB 231 Chap 2 Diode Circuits

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Slide 1Mustafa Karaman EHB 231 Elektronik - I Chapter 2: Diode Circuits


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Slide 2 Mustafa Karaman EHB 231 Elektronik - I Chapter 2: Diode Circuits

• Rectifier circuits

• Zener diode circuits

• Clipper and clamper circiuts

• Multiple diode circuits

Chapter 2 Diode Circuits


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DC Power Supply

AC

220V (rms)

50 Hz-

+

V s

+

-

Voltage

Transformer

Diode

rectifier Filter

Voltage

Regulator Load


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Diode Model

V S

V 0

VD0

0

Slope=R/R+r D

V S

V 0

VD0

VS

VD0V

t

Input and output waveforms for r D


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Transfer characteristic assuminga constant junction voltage

Full-wave rectifier

+

V 0 -

D1

-

V s +

R+

ac

-D2

+

V s -

V 0

VD00

Slope=1

- VD0

Slope=-1

v Input and output waveforms

V S

V 0 VS

VD0

t

- V S


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Bridge (full-wave) rectifier

Input and output waveforms

V S

V 0 VS

2VD0

V

t

- V S

ac

-

+

V s

+

-D2

D4+ V 0 - D1

RL

D3


7/25Slide 7 Mustafa Karaman EHB 231 Elektronik - I Chapter 2: Diode Circuits

Voltage & Current WaveformsIn Peak Rectifier Ckt (CR >>T).

+- RV S

I D

C+V 0 -

I C

I R

V 0

Vr

T

V p

t t 2 t 1

t

Conduct ion

interval

t

t

I L

I D



A 5-V Regulated Power Supply

D1

D2

1

0

3

5

6 7

4

2

14:1

14:1

V 0

+

-

R 100 M Isolation

R

500

load

R=160

C

583 F

5.1 V

R =0.5s

V

120V - rms

@ 60 Hz

ac

10 V

0 V

2 V

4 V

6 V

8 V

0 50 100 150 200

Smoothing-capacitor voltage

Loading voltage

v( 7,4 ) v( 6,4)

Time, ms


9/25Slide 9Mustafa Karaman EHB 231 Elektronik - I Chapter 2: Diode Circuits

Voltage-Doubler Circuit & Waveforms

+

-

1 32 D2

D1

c120V

– 20V

V(2)

Time (ms) – 20V

0V

V(3)

10V

– 10V

V(1)

2



Limiting & Clamping Ckts: Example-1

+

V 1

-

R

+

V 0

-

1

1

0.7

V0

V1

Describe transfer characteristic of the circuit

For V i < V DO = 0,7V

Diode is O.C.

V 0 =V i

+

0,7V

+V i-

+V 0-

V 0 =V i for V i




1

1

-0.7

V0

V1

+

V 1

-

R

+

V 0

-

Describe the transfer characteristic

For V i > -V T = -0,7V

Diode is O.C.

V 0 =V i

0,7V

+

+V i-

+V 0-

Transfer characteristics

V 0 =V i for V i > -0,7V= -V DO V 0 =0,7 V for V i -0,7V

+V i

-

+V 0-

For V i -V DO = -0,7V

Diode is S.C.

V 0 =-V DO =-0,7V




+

V 1

-

D1

D2

R

+

V 0

-

+0.7

-0.7

V0

V1

For

-V DO =-0.7




5 V

R

+

V 1

-

+

V 0

-

1

1

5.7

+5.7

V0

V1

Describe the transfer characteristics of the circuit

V V for V < 5v+ 0.7v

V = 5v+ 0.7v for V 5v+ 0.7v

o i i

o i

io

DOi

VV

O.C.isDiode

5.7V5vVFor

5.7vV5vV

S.C.isDiode

, 5.7vV5vV

For

DOo

DOi

5 V

R

+

V i

-

+

V 0

-

0.7 V+

+

+

V i

- 5 V

R

+

V 0

-

+




)()( 21 DOi DO vvvvv z z

DZ1 and DZ2 are OC ivv 0

R

+

v i

-

1Z

2 Z

+

v 0

-

Descr ibe th e transfer character is t ic of th e circuit

v 0

1

1

DO Z V V

1

DO Z V V

2

v i

v). z ( vvi 702 ). z ( z vvvv D O 70210

v). z ( vvi 702 70

220 . z z vvvv

DO

DZ1 is SC and DZ2 is OC

DZ1 is OC and DZ2 is SC

i 0 v v = for )0.7v z ( 0.7v) z ( 2 i 1 v v v

0.7v) z ( 10 v v for 0.7v) z ( 2 i v v

0.7v) z ( 10 v v 0.7v) z ( 2 i v v for



Additional Examples



+ v D (t) –

i D (t)

If v D 0 & i D >0

OC

SC

v D

i D

0OC

SC

Ideal Diode Model



I R(t)=?

Example 1 :

0.5cos(t) V1

~

1 V

+vR(t)

–

I.D.

Limiting & Clamping Ckts: Ex. 1

V

0

0,51

I S 1+0.5cos(t)(t)=

0.5cos(t)t

1,5

л/2 л 3л/2 2л

1V



Assume that diode is OC

i d (t)=0 for all t

V d (t) = 1+0.5cos(t)

V d (t) > 0

Assumption is not correct !

+ v d

(t) –

id(t)

0.5cos(t) V 1~

1 V

Ω

i d (t) = V s (t) / RV s (t) = i d (t) . R

= V R (t)

i d > 0 for all t

diode is SC for all t

Assumption is correct!

Assume that diode is SC

i d (t)

0.5cos(t) V 1~

1 V

Ω



i d (t) = ?

+v s (t)

–

~

+ v R (t) –

R = 1

+v d (t)

–

ID

v s (t) = 0.5 + sin(t) (V)

v s (t )

π/2

t

-1.0

0.5

1.5

0.5

0.0

1.0

D: ON

π 3π/2 2π

v s (t ) = 0.5 + sin (t )


D: OFF D: ON D: OFF



+v s (t)

–

+ v R (t) –

~ +v d (t)

–

i d (t) For Vs(t) > 0

Assume that: DIODE SC

V d (t) = 0

i d (t) = V s (t) / R

= 0.5+sin(t) A

i d (t) > 0

Assumption is correct!V R (t) = i d (t) . R = V s (t)

1 Ω

~

+ v R (t) –

1

+v d (t) –

For V s (t)


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R

+

v 0 (t )

-

~v i (t)

V a

ID

R

Plot v 0(t) & v 0(t) vs v i(t) .

+v d (t)

-

i d (t)

Diode: SC v d (t) = 0, i d (t) > 0

i d (t) = (v i (t) - Va ) / R

v i (t) > Va

v 0 (t) = V a

Diode: OC v d (t) < 0, i d (t) = 0

- v i (t) + i d (t).R + V a + v d (t) =0

v d (t) = v i (t) - V a < 0

v i (t) < V a

v 0 (t) = v i (t)

~ v i (t)

+

v 0 (t)

-

R

~ v i (t)

V a

i d (t)

i d (t)


+

v 0 (t)

-

V a


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va

0

v 0 (t)

v i (t) va

( v 0 (t) vs v i (t) )

v(t)

va

0

t

v i (t)

v 0 (t)


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v i (t)

+

v 0 (t)

-

~

V a

R s

R 0

ID+

v d (t) -

i d

Plot v 0 (t), v 0 (t) vs vi (t) .

Diode: SC

+

v 0 (t)

~

v a

R s

R 0

+

v d (t)

-

i d (t) v i (t)



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+

v 0 (t)

-

~

v a

R s

R 0

+

v d (t)

-

i d (t)

v i (t)

diode: OC

v d (t) < 0, i d (t) = 0 v i (t)+ R s . i d (t) + v d (t)

+ R 0 . i d (t) + v a =0

v d (t) = v i (t) - v a < 0

v i (t) < v a

v 0 (t) = v i (t)

va

v(t)

0 t

v i (t)

v 0 (t)

R0/(R0+ Rs)

va

0

v0(t)

vi(t)va

va. RsR0+ Rs

EHB 231 Chap 2 Diode Circuits

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Transcript of EHB 231 Chap 2 Diode Circuits