Download V in - V out

MALVINO
Electronic
PRINCIPLES
SIXTH EDITION
Regulated Power
Supplies
Chapter 24
Power supply regulation
Vline
Vout
RL
VNL - VFL
Load regulation =
x 100%
VFL
VHL - VLL
Line regulation =
x 100%
VLL
A zener diode shunt voltage regulator
RS
Power
supply
Vin
VZ
RL Vout
Vout = VZ
Vin - Vout
IS =
RS
IL =
Vout
RL
IZ = I S - IL
Improved shunt voltage regulator
RS
Power
supply
Vin
VZ
RL Vout
Vout = VZ + VBE
Vin - Vout
IS =
RS
IL =
Vout
RL
IC  IS - IL
Zener follower is a series voltage regulator.
Power
supply
RS
Vin
PD  (Vin - Vout)IL
Vout = VZ + VBE
VZ
RL
Vout
Two-transistor
voltage regulator
Vout =
R3 + R4
R4
(VZ + VBE)
+Vin
R1
R2
Q2
R3
Q1
VZ
RL
R4
Vout
Improved
voltage regulator
Vout =
R2 + R3
R3
VZ
+Vin
R2
R1
RL
VZ
R3
Vout
Regulator with
current limiting
Vout =
Q1
R2 + R3
R3
VZ
+Vin
R4
R1
R5
VZ
R2
Q2
RL
VBE
ISL =
R4
R3
Vout
VL
Simple current-limiting
Vreg
Constant current
region
VBE(Q2)  0.6 V
ISL
IL
Foldback
current limiting
Q1
+Vin
R7
K=
R6 +R7
VBE
ISL =
KR4
R4
R6
R1
R7
R2
RL
R5
VZ
Q2
R3
(1-K)Vout
Imax = ISL +
KR4
Foldback current-limiting
VL
Vreg
Foldback current
region
ISL
Imax
IL
Monolithic regulator with current booster
Vin
Q1
1
R1
LM78XX
3
2
Vout
RL
Current booster with current limiting
R2
Q2
Vin
Q1
1
R1
LM78XX
3
2
Vout
RL
DC-to-DC converter
+Vin
R1
Q2
T1
vin
Q1
Q3
R2
RL
Switching regulators
• The pass transistor is switched between
cutoff and saturation.
• Better efficiency than linear.
• Topologies:
– Buck: steps the voltage down
– Boost: steps the voltage up
– Buck-boost: inverts the input voltage
Buck regulator
Q
L
+Vin
D
C
RL
R2
PWM
Vout = DVin
VREF
R1
Boost regulator
Vkick
Vp
+Vin
L
Q
D
C
RL
R2
PWM
Vp = Vin + Vkick
VREF
R1
Buck-boost regulator
Q
+Vin
L
D
C
RL
R2
PWM
VREF
R1
Monolithic buck regulator
5 IN
OUT
4
L
+Vin
D
LT1074
C1
C3
RL
R2
COMP
2
FB
3
R1
R3
C2
1
Vout =
R1 + R2
R1
(2.21 V)
Using the charge pump of the MAX633 IC
+15 V
+Vin
4
IN
OUT
CP
MAX633
5
C3
6
-12 V
C1
D2
1,3,7
D1
C2