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ElectronicsOverviewOverview: the Property of One-: the Property of One-way Conduction of diodesway Conduction of diodes
1. forward bias1. forward bias (( P is positive and N is nagativP is positive and N is nagativee )) the current flow is significantthe current flow is significant
2. reverse bias2. reverse bias ( ( P is nagativeP is nagative and N is positiveand N is positive ) ) the current flow is very smallthe current flow is very small
3. No any one-way conduction when diodes 3. No any one-way conduction when diodes work beyond Uwork beyond U BK BK
4. Reverse current flow will be influnced by te4. Reverse current flow will be influnced by temperature.mperature.5.The property of saturation of reverse curren5.The property of saturation of reverse current flow.t flow.
ElectronicsChapter6 Sources of Stable DC Voltage(Page 167)
1. Diode Rectifiers
2. Power Supply Filtering
3. Voltage Regulator
Electronics
Sources of Stable DC Voltage
The small power supplyThe small power supply
u4 uou3u2
u1
ACAC
LoadLoad
TransformerTransformer RectifierRectifier FilterFilter RegulatorRegulator
DCDC
Electronics1. Diode Rectifiers
• Half-Wave Rectifier
• Full-Wave Bridge Rectifier
ElectronicsHalf-Wave Rectifier
–
+ +
–
aTrD
uou
b
RL
io动画
u
tO
uo
Ot
U2
U2
?To calculate the average value of output voltage
U0.45oU
Electronics
Full-Wave Bridge Rectifier
-
t
RLu
io
uo
1
23
4a
b
+
–
+
–
-
动画
uo
u
t
U2
U2
Positive half cycle,D1\D3 conduct,D2\D4 are reverse biased
?To calculate the average value of output voltage UUo 0.9
ElectronicsFull-Wave Bridge Rectifier D1
RL uo
D6
D3 D5
D4D2
io
Cb
au
++
–
–
o
Common cathode
Common anode
Electronics
From time From time tt11~~tt22 : :
uuoo==uuabab
D1
RL uo
D6
D3 D5
D4D2
io
Cb
au
++
–
–
o
Output voltage
u:The transformer secondary voltage 动画
u
o
ub uCua
2 t
uo
ott1 t2 t3 t4 t5 t6 t7 t8 t9
Electronics
t1 t2 t3 t4 t5 t6 t7 t8 t9
uo
to
D1
RL uo
D6
D3 D5
D4D2
io
cb
au
++
–
–
o
负载电压
u
o
ua ub uC
2 t
UUo 2.34
ElectronicsHomework
• To calculate the average value of output voltage in half and full-wave rectifier circuits.
• To calculate the average value of current of every diode in half and full-wave rectifier circuits
• To calculate the maximum reverse bias voltage that every diode endures in half and full-wave rectifier circuits
Electronics2.Power Supply Filtering
u RLuo
+ +
– –
~ +C
C: Smoothing Capacitor
Electronics2.Power Supply Filtering
+C
ic
i
–
+ +
–
aD
uou
b
RL
io
= uC
动画
uo
U2
U2
u
tO
tO
25)(3L
TCRτ
((T T — — the period of voltage)the period of voltage)
Electronics
iD
t
uo
U2
tO
O
IIpeakpeak
To choose diodes:To choose diodes: IIOM OM =2 =2 IID D
RLC is larger the peak valure of iD is larger
Electronics3. Voltage Regulator
• Zener Diode Shunt Regulator
• Voltage Regulator
ElectronicsZener Diode Shunt Regulator
U
IUZ
+
–UI RL
+C
IO
UO
+
–
+
–u
IR R
DZ
Iz
Stable voltagecircuit
ElectronicsZener Diode(Page 11)
• UZ(2CW13:5~6.5V)
• Voltage stable constant
(Page 12)
Figure 1.3.2
U
IUZ
ElectronicsZener Diode Shunt Regulator(Page 176)
UO = UZ
UO +UR= UI
IR = IO + IZ
U
IUZ
RL(IO) IR
to assume RL is changed
UO IR (IRR) UO (UZ ) IZ
+
–UI RL
+C
IO
UO
+
–
+
–u
IR R
DZ
Iz
Stable voltagecircuit
Electronics
Ui
T
R2UZ
RL UO
+
–R3+
+
––
+
UB
+
–DZ
+
–Uf
+
–
R11R
1R
Zener Diode Shunt Regulator(Page 177)
there are four parts.
regularamplifie
r
reference sample
Electronics
Z21
1
BO
)(1 URR
RUU
output
Ui
T
R2UZ
RL UO
+
–R3+
+
––
+
UB
+
–DZ
+
–Uf
+
–
R11R
1R
ElectronicsIC Voltage Regulator
Three points
The constant voltage output
Flexible voltage Flexible voltage outputoutput
Positive output78XX
negative output79XX
( 1. 25 ~ 37 V )
Electronics
Introduction of pointsIntroduction of points
W7800
1—input3 —common
2 —output
W7900
1 — common3—input
2 —output
Electronics
(1)(1) constant voltage outputconstant voltage output
UUinputinput-U-Uoutout
putputis moris more than 3Ve than 3V
CO
W7805
CiUi
+
_
+
_
UO
1 2
3
0.1~1F 1F
To improve transiet To improve transiet outputoutputTo imorove the waveTo imorove the wave
Electronics
(2)(2)Both positive and negative voltage Both positive and negative voltage outputoutput
23
220V
24V +C
24V+C
W7815
Ci
+15V1 2
3
Ci
W7915
1CO
CO
– 15V
1F
1F
0.33F
0.33F
1000F
1000F
Electronics?
• What is significant as a voltage source?