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7.4
Power Supply Unit P816
7.4.1
Description of P816
MOSFET Q825 is used as a power switch controlled by the
controller Q810. When the switch is closed, energy is
transferred from mains to the transformer. This energy is
supplied to the load when the switch is opened. Through
control of the switch-on time, the energy transferred in each
SWITCHING POWER SUPPLY PCB. (P816)
R819
C820
G815
0.22
330k
0.01
J801
(UL/CSA,MITI)
250V
1M(CB)
F820
L820
S815
J820
J821
J828
R810
R801
Q810
10k
82k
MC44603P
C801
82pF
DEMAGINETIZATION
NP0
DETECT
8
DEMAGNETISATION
MANAGEMENT
9
SYNC
IREF
C802
820pF
OSCILLATOR
10
R802
RF
22k
15
STANDBY
R803
RP
4.7k
12
STANDBY
STANDBY
(REDUCED FREQUENCY)
C803
470p
VSB
2.5V
OUT
14
ERROR
AMP
R805 R804
C804
VOLTAGE
15k
15k
4700pF
FEEDBACK
E/A OUT
13
FOLDBACK
FOLDBACK
CURRENT
INPUT
SENSEINPUT
5
7
R806
R808
R807
C809
1k
18k
180k
1500p
Description of controller MC44603
The MC44603 is an enhanced high performance controller that
is specifically designed for off-line and DC-to-DC converter
applications. This device has the unique ability of automatically
changing operating modes if the converter output is
overloaded, unloaded or shorted. The MC44603 has several
distinguishing features when compared to conventional SMPS
controllers. These features consist of a foldback facility for
overload protection, a standby mode when the converter output
is slightly loaded, a demagnetization detection for reduced
switching stresses on transistor and diodes, and a high current
totem pole output ideally suited for driving a power MOSFET. It
can also be used for driving a bipolar transistor in low power
converters. It is optimised to operate in discontinuous mode but
can also operate in continuous mode. Its advanced design
allows use in current mode or voltage mode control
applications.
D802
S1WB
C819
C825
0.1
470pF
250V
/400V
C826
470pF
/400V
C821
120
D803
/400V
D804
C828
470pF
R823
/400V
18k
1/2W
R832
18k
R829
1/2W
10k
16
1
VREF IREF
REFERENCE
SUUPLY
UVL01
BLOCK
INITIZLIZATION
BLOCK
2
LATCH
3
BUFFER
=1
Q
4
THERMAL
VREF VOC
SHUTDOWN
OVER
OVER
6
VOLTAGE
VOLTAGE
IREF
PROTECT
MANAGEMENT
DMAX&
UVL01
SOFT-START
CONTROL
VREF
R816
180
SOFTSTART
&DMAX
11
R809
C810
330
2.2/50V
Figure 7-18 'Blockdiagram P816'
cycle is regulated so that the output voltages are independent
of load or input voltage variations. The controlling device
MC44603 is an integrated pulse width modulator. A clock
signal initiates power pulses at a fixed frequency. The
termination of each output pulse occurs when a feedback
signal of the inductor current reaches a threshold set by the
error signal. In this way the error signal actually controls the
peak inductor current on cycle-by-cycle basis.
L831
L831
1
D851
AG01
L825
D806
4
C827
Q825
14
470pF
2SK2943
/1kV
D807
R825
13
1k
R826
R827
R828
12
1
1.5
1.5
D856
RK46
11
D832
AG01
5
L832
10 µ H
10
6
9
D866
RU4YX
8
7
R812
100
R813
15
Q801
C813
PC123F
2200pF
R887
D881
100
TL431
R835
D835
OPTION
OPTION
D814
R814
AG01
1.8k
R815
1.8k
C814
0.1
+12V
R892
22k
Q891
R891
2SC2878
22k
Pin connections
Foldback Input
Overvoltage Protection (OVP)
Current Sense Input
Demag. Detection
23
Q851
LM317
L853
4.7 µ H
R853
10
R852
220
C854
C851
100/6.3V
0.1
C852
R851
L851
330
560
4.7 µ H
/16V
L856
6.8 µ H
C860
C859
0.1
100/10V
C857
C856
2200
/10V
R861
10k
D861
R862
L861
AG01
1k
1 µ H
D862
Q861
2SC
Q862
R863
C862
10k
2SA
C861
R865
10/50V
10k
+12V
R864
10k
L867
2.2 µ H
L866
C866
C867
Q871
0.1
1000
C868
7908
/16V
D871
AG01
C877
L872
L871
0.1
C871
10uH
C872
0.1
220
C873
R881
R882
/16V
220
3.3k
100
/16V
L873
10uH
C876
R883
220/16V
C882
1.8k
0.022
C881
100
R884
/25V
2.21k
1%
R885
681
1%
R886
R893
10k
C891
100/25
VCC
1
16
VC
2
15
Output
3
14
Gnd
4
13
5
12
6
11
7
10
8
9
Figure 7-19
L854
10 µ H
Q892
C892
100/25
PC123F
C855
0.1
R894
1k
L852
J851
-34V
GND
+5V
+5V
GND
L862
GND
10 µ H
GND
+12V
C864
220/50V
-8V
J852
C869
220
D868
GND
/16V
+12V
GND
R866
1k
+5V
GND
U810
-12V
(-8V)
C875
(-8V)
100
-12V/-8V
/16V
SELECT
JUMPER
U811
-12V
J891
C898
0.1
Rref
R Frequency Standby
Voltage feedback Input
Error Amp Output
R Power Standby
Soft-Start/Dmax/
Voltage Mode
CT
Sync Input
CL 96532076_030.eps
290799
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