Current Mode Power Supply 30Ps203; Function Description Of The Current Mode Power Supply; General Description Of Mc44603; Pin Connections - Philips DVD 950 Service Manual

GB 56 10.

10. Current mode power supply 30PS203

10.1 Blockdiagram
MAINS
7110
2.5V
Error
Amplifier
Current
Sense
Input
Voltage
Feedback

10.1.1 Function description of the current mode power supply

MOSFET 7125 is used as a power switch controlled by the
controller IC 7110. When the switch is closed, energy is
transferred from the mains into the transformer. This energy is
then supplied to the load when the switch is opened. By control
of the switched-on time, the energy transferred in each cycle is
regulated so that the output voltages are independent of load
or input voltage variations. The controlling device MC44603P is
an integrated pulse width modulator. A clock signal initiates
power pulses at a fixed frequency. The termination of each
output pulse occurs when an analogue of the inductor current
reaches a threshold established by the error signal. In this way
the error signal actually controls the peak inductor current on
cycle-by-cycle basis.

10.2 General description of 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 demagnetisation detection for reduced
switching stresses on transistor and diodes, and a high current
totem pole output ideally suited for driving a power MOSFET. It
DVD 950 Current mode power supply 30PS203
Rectifier
Lightning
Protection
EMI
FILTER
6129
Supply Init
Demagnet.
OSC.
Mgmt
Output Vc
Sense
+
S
-
Out
- R Q
Buffer
+
latch
Gnd
Soft-Start Overvoltage
Control Mgmt
6240
5131
1
2121
6250
7125 5
6260
Rsense
6230
6132
6210
6220
7
9
GNDs
7200
7201
REGULATION
Figure 10-1
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.

10.3 Pin connections

Foldback Input
Overvoltage Protection(OVP)
Current Sense Input
Demag. Detection
+12V
7233
2240 +5V Stand By
-8V Stand By
2250
-40V
2260
+6V Stand By
7236
+5V
2230
Stand By
+3V3
2210
GND
CL 96532065_064.eps
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VCC 1 16 Rref
VC 2 15 R Frequency Standby
Output 3 14 Voltage feedback Input
4 13
Gnd Error Amp Output
5 12 R Power Standby
Sof-Start/Dmax/
6 11
Voltage Mode
7 10 CT
8 9
Sync Input
Figure 10-2
CL 96532065_057.eps
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