Transcript Elektroniczne Układy i Systemy Zasilania

SWITCH-MODE POWER
SUPPLIES AND SYSTEMS
Lecture No 2
Silesian University of Technology
Faculty of Automatic Control, Electronics
and Computer Sciences
Ryszard Siurek Ph.D., El. Eng.
Power supply status indications



Optical indication (usually different colour LEDs)
- green
normal operation
- red
failure (protection circuit activation)
- yellow
warning (e.g. mains voltage decay
and battery operation)
Contact indication (rely)
- contacts closed
normal operation
- contacts open
power failure
Power Fail Signal or PF
UOUT
DU
Dt > 1ms
t
PF
„1”
Dt
„0”
t
DU < 5%Uo

Power Good Signal
UOUT
DU
DU < 5%Uo
t
„1”
PG
„0”
t
Output voltage hold-up time
UIN
t
95% Uo
UOUT
Uo
tp
t
tp –
hold-up time
(up to several ms)
Power Supply protection
Overcurrent protection
1. Constatnt current (CC) limiting
2. Power limiting
UU
wOUT
y
constant current
Uo
power limiting
switch-off
Io = Inom Imax
Izw
ISC
Iw y
I
OUT
3. Output current fold-back
U wy
UOUT
nominal
working
punkt pracy w
warunkach point
normalnych
Uo
resistive load
non-linear
load
charakterystyka
U=f(I) obciazenia
U<Uo
possible
start-up
operating point
hipotetyczny
punkt pracy
Izw
ISC
4. Power supply switch-off (fuses
5. Thermal protection
I o = I nom I max
I wy
I
OUT
Over-voltage protection
UOUT
regulated
voltage level 2
UOUTmax
Uo
FS – feedback loop
(voltage regulation)
FS1
UOUT
FS2
switch-off
t
UM - voltage monitoring circuit
UM
switch-off
UOUT
power supply switching-off
typical implementation
UOUT
crowbar type overvoltage protection activates overload or short-circuit
protection circuit
Power leads voltage drop compensation
Is = 0
+S
Power
Supply
Io
Uo
U1
rs
DUs
Ro Uo
rs
-S
DUs
U1 = Uo + 2DUs
Feedback circuit controls voltage across +S & -S
Parallel operation of power supplies
Increasing of the the total output power
Power
Supply # 1
I1
U01
I1, I2
Power Supply # 1
100% load
I0
I2
U0
Power
Supply #2
I1max
U02
I1
I2
I0
I1max
2I1max
~U
U01 =
02
U01 > U02
I1max = I2max
Overload protection circuit with current (power) limitation is required
Parallel connection with non-balanced output currents
CS - current share
Power
Supply # 1
CS
additional
connection
CS
Power
Supply # 2
U01
I1
I0
I1, I2
U0
I2
I1max
U02
I1
I2
I1max = I2max
U01 > (<) U02 (may slightly differ)
I0
I1max
2I1max
Power Supply # 1 (master) forces adequate
changes of UO2 to keep I2 close to the actual
value of I1
Parallel connection with current share facility (balanced output currents)
Paralleling of power supplies for redundancy
(output voltage security)
UIN1
D1
Power
Supply # 1
I1
U01
I0
I2
U0
UIN2
Power
D2
Supply # 2
U01 ~
= U02
I1max = I2max
I0
< I1max, I2max
U02
Redundancy 1 + 1
Redundancy n + x
- „n” modules necessary to supply load current
- „x” modules which can fail simultaneously