Samsung HPS5033X/XAC Service Manual page 124

4. Basic Function
① Remote Control
This power circuit has the function of remote control by using the relay (250V, 10A)
② Free Voltage
This power circuit has the free voltage input range.
③ Power Factor Correction
This power circuit has the PFC for high power factor (higher than 0.9)
④ Protection
This power circuit has the function of short / O.V.P / O.C.P for the protection of part's damage.
5. Explanation of Circuit Blocks
① Filter Circuit
Line filter consists of Common Mode Reactor L8102¡¤ L8103, Normal Mode Reactor L8101, X-condenser C8101ㆍC8106,
Line by-pass condenser(Y-con) C8104ㆍC8105 and surge protection parts ; NR8101ㆍNR8102ㆍNR8103ㆍNR8104ㆍ
SQ8104ㆍSQ8105.
This block reduces the high frequency ground noise from the original ac power source.
② Rectifier / DC link Circuit
This rectifier circuit creates the dc regulated voltage from AC input line.
【Power Source】
ㆍSub-power Source
The half-wave AC voltage through the D8151 creates the sub-dc source in C8121.
ㆍMain-power Source
The full-wave AC voltage through the RC8101 creates the main-dc source for PFC input.
③ Inrush Current Protection Circuit
In a transient response interval of the AC source injection, the high inrush current flows from ac source to this power board
because of an input capacitor having the low impedance. At that interval, the part¡¯s damage is quite within the realms of
possibility. The inrush current protection circuit removes this possibility in a transient interval by adding thermistor (TH8101,
TH8102). After PFC input capacitor is fully charged, (in steady state), the relays (RL8101, RL8102) are ON and input normal
current flows through them without any overheat.
④ Sub-Power Circuit
【Basic Operation】
This Stand-by block is controlled by SMPS operation ; On/off switching FET inside of PRC [pulse ratio controlled] IC
(STR-V152).
Using the switching operation, we can get the energy in an input capacitor [C8121] to transmit to output-port for STD 5V, dc
source for Micom and PFC controller. The PRC controller STR-V152 can be operated by injection of the Start-up current to
8 pin of it. Output voltage is also controlled by following method ;
Controlled op-amp [Z8171] keeps the output voltage to be constant in steady state by compensating an error voltage
between the dividing-resistors (R8174, RX8172 and R8175) and its reference 2.5V. And then output small signal voltage of
op-amp induces a Photocoupler current level on the feedback line. Dc source voltage for PFC controller comes from
secondary side link in a main transformer (3~5 pin).
【Protection Function】
ㆍOver Voltage Protection
When the Vcc voltage is higher than O.V.P level [Vcc(OVP)=31.2V(TYP)], Latch is on and power board is shut down. After
Latch is on, this power board can not operate before the voltage of an electric capacitor C8123 is fully discharged for about 5
minutes.
ㆍOver Current Protection
O.C.P function in STR-V152 can be obtained by sensing the MOS-FET's drain peak current per 1 pulse (Pulse by Pulse
method). This sensing value comes from the voltage across sensing-resistor(R8122) between OCP(FET source,3Pin) and
GND(5Pin). Thus, this power board can protect any part's damage caused by over current flowing.
ㆍOver Load Protection
If there is an overload state in output ports due to some reason, this power board operates in UVLO mode for protection of
IC's damage.
Samsung Electronics
Circuit Description
13-3