Samsung RS21KLMR circuit descriptions
43
10. Circuit Descriptions
10-1) Source Power Circuit ································ 44
10-2) Oscillator Circuit
··································· 44
10-3) Reset Circuit
····································· 44
10-4) Door S/W Sensing Circuit
······························ 45
10-5) Temperature Sensing Circuit
···························· 45
10-6) Key Scan and Display Circuit
···························· 46
10-7) CoolSelect Zone
TM
Panel Circuit ·························· 48
10-8) Fan Motor(BLDC) Drive Circuit
··························· 49
10-9) EEPROM Circuit
··································· 50
10-10) Option Circuit
···································· 50
10-11) Load Drive Circuit
·································· 50
44
Circuit Descriptions
10-1) Source Power Circuit
10-2) Oscillator Circuit
10-3) Reset Circuit
Terminal Oscillation Frequency
Xin(#30)
Xout(#31)
4MHz
4MHz
This circuit shows SMPS(Switch Mode Power Supply) which converts AC input voltage (230V, 50Hz) to a high DC
voltage (about 320V). The input AC source power is converted to DC through a wave rectifier (BD1) and the converted
DC power will generate a constant waveform on the switching transformer using a high speed (100KHz) switching motion
of TOP223Y. The D104 will rectify the generated voltage and transform into a steady 12V DC source power used for the
digital display panel and relays. The regulator (KA7805) finally transforms into 5V DC source power for the control board
and sensor’s circuits.
Caution) Be careful to handle this circuit due to high voltages (AC1 15V, DC170V)
This is oscillator circuit to generate synchronous clocks used to calculate the time for the microprocessor operation.
Note) If the specification of a resonator changes, micro-processor can not work properly .
The reset circuit is to initialize the values RAM ＆ other sectors of micro-processor. When the power is engaged initially,
the reset voltage becomes “Low,” and it keeps “High” in the normal operation.
Terminal Voltage
Vcc
RESET
DC 5V
DC 5V
45
Circuit Descriptions
10-4) Door S/W Sensing Circuit
10-5) T emperature Sensing Circuit
1 ) F-Room door open is picked up based on the state (5V/0V) of the MICOM No.43 Port.
When the F-Room door opens, it becomes short between the Door S/W 1 &2.And,5V is supplied in the following
order. CN30 No.⑨→F-Door S/W → CN30 No.①→R408(1 0K)→MICOM 43 PORT
When the state of MICOM 43 PORT is 0V, the door is picked up as closed. When it is 5V, the door is considered to be
open.
2) R-Room door open is picked up based on the state (5V/0V) of the MICOM No.44 Port.
When the R-Room door opens, it becomes short between the Door S/W 1 &2.And,5Vis supplied in the following order .
CN30 No.⑩→R-Door S/W → CN30 No.⑤→R407(1 0K)→MICOM 44 PORT
When the state of MICOM 44 PORT is 0V, the door is picked up as closed. When it is 5V, the door is considered to be
open.
3) When door open is detected, the MICOM have the relevant Fan Motor stop and the relevant Room Lamp light up.
Depending on the state of Door Open/Close, there are following operations; Lamp On/Off, Fan Motor On/Off and Door
open alarm. So, check relevant items upon A/S.
Terminal Operation Volt(state)
Freezer
(MICOM43PORT)
DOOR OPEN
DOOR CLOSE
0V (LOW)
5V (HIGH)
Ref.
(MICOM44PORT)
DOOR OPEN
DOOR CLOSE
0V (LOW)
5V (HIGH)
# of t
erminal in MICOM Remark
PIN #56 (F-SENSOR)
PIN #57 (F-DEF-SENSOR)
PIN #59 (R-SENSOR)
PIN #60 (R-DEF-SENSOR)
PIN #63 (EXT-SENSOR)
Micom
terminal
voltage may
change
according to
temp.
1) A thermistor with a negative temperature coefficient (NTC) is used for a temperature sensor .
2) Resistors, R 306 ∼ R310 and capacitors, C 301 ∼ C 305 are used for a noise protection purpose.
3) For the F-sensor, the input voltage into the micro processor (MICOM), VF is calculated by (Rth x Vcc)/(R303+ Rth),
where Rth is a corresponding resistance to the thermistor’s output (See Ref. 6 in Appendix).
4) The F-Def sensor is connected with a bimetal and a temperature sensor is in parallel. In a normal operation of the
system, the bimetal is on and 0V is input into the micro-processor. During a defrost cycle, the bimetal will be of f from
54℉, and a divided voltage with R304 enter to the micro-processor to keep sensing the set temperature.
CN30
F-DOOR S/W
124
3
R-DOOR S/W
124
3
HOME BAR S/W
W/R
W/B
ORG
S/BLU
SMW250-13 WHT
1
C708
104
5
C709
104
Vcc
9
10
11
R408
C404
10K
R407
104
C403
10K
104
F
R
43
P42
P43
44
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