Samsung PS42P2SBX/XEC, Service Manual

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Circuit Operation Description
5-4 Samsung Electronics
(1) AC-DC Converter
PDP-42PS o400V DC from the common AC power supply using the active PFC booster con-
verter. This converter is designed for improving the power factor and preventing the noise with high
frequency and finally becomes the input power system for the switching regulator on the output side.
(2) Auxiliary Power Supply
The auxiliary power supply is a block generating power of •Ï-com for remote controlling. Once the
power plug is inserted, this block always comes into operation, causing •Ï-com to get into the stand-
by state for the output. Thus, this output is called the stand-by voltage. And with the relay ON signal
inputted through the remote controller, this block turns the mechanical switch of relay to ON for dri-
ving the main power supply.
(3) Implementation of Sustain Voltage
As the main part of a SMPS for PDP, sustain voltage must supply a high power, +165V/ 1.4A. It is
designed using forward converter basically. At the output stage two 90V converters are connected
serially for high efficiency and reduction of system size against a single 180V converter.
(4) Implementation of Small Power Output (Va, V(D), V(A), Vfan, V9, Vsamp, Ve, Vset, Vscan, V12, and
Vg)Vset, Ve, and Vscan used DC-DC module. V(D), Va, V12, and Vfan used forward converter, and
Vsamp used flyback converter. V(A), V9, and Vg are simply implemented using switching regulator.
5-1-3 Requirements of PDP SMPS
Since SMPS does not operate alone, but it operates with the load of the whole system, it should be designed
carefully considering the load of the system. In addition, it should be designed considering emerging issues
such as EMC, and protection against heat as well as system stability especially.
5-1-3(A) SAFETY AND REMOTE CONTROL CAPABILITY
Stability is one of the most important requirements for SMPS. SMPS should be designed to prevent
abnormal status due to abnormal load variation so as to keep the system stable, and guarantee customer
safety.
The protection circuits of SMPS include over-current protection (OCP), over voltage protection (OVP),
and under voltage lock-out (UVLO), and short circuit protection circuit. Although each circuit can be
implemented by various procedures, the most popular is implementing with comparator that compares
current value with that of standard and determine abnormality of the circuit.
In addition, surge current protection, insulation management, and static electricity protection circuit
should be added, because it uses commercial power source as an input.
PDP SMPS should be designed using auxiliary power and relay to provide remote control capability.