12-8) Fan Motor(Bldc) Drive Circuit - Samsung RSE8KPAS Service Manual

Circuit Descriptions
2-1) CoolSelect ZoneTM Drawer is controlled by a damper to supply or block cold air. For Quick Cool, the damper will be
closed. So cold air is supplied only to CoolSelect ZoneTM Drawer.For Thaw, the evaporator heater of refrigerator is
ON and the damper is controlled by the refrigerator temperature.
2-2) The stepping motor controlled by a Driver IC TA7774P(IC7) operates the damper. The stepping motor uses 4
combined signals to open and close the damper.
Note) To prevent the malfunction from a high humidity, a DC 12V, 1 watt heater is mounted and activated continuously.
12-8) Fan Motor (BLDC) Drive Circuit
1) Motor drive circuit
1-1) This refrigerator adopts a BLDC motor for reduce energy consumption, Motors of the freezer, refrigerator and the
machine compartment are composed of the BLDC. (This circuit is used to other models in common.)
1-2) Operating Principle
In the above circuit, there are similarities between motors in the composition of their circuits. Here comes the F-Fan
motor for example. According to conditions, the F-Fan motor runs High or Low in RPM. To opernte the F-Fan
motor, a specific voltage should be applied to OP-AMP No.2 as shown in the figure. When MICOM No.50 is 0V,
OP-AMP No.2 also becomes 0V. So, the motor does not operate. When MICOM No.50 becomes High (5V), the
forward voltage drop of R701 and D701 (IN4148) will be subtracted from the High voltage and then voltage will
decided through the division with R707 10K. The devided voltage then flows to OP-AMP No.2 amplifying treble
voltage. It applies to the motor. If the voltage at OP-AMP No.2 is 3V, 3V x 3 = 9V applies to the motor. (When the F-
Fan is High, 5V will be output from MICOM No.2 and when it is running in Low RPM, MICOM No.2 becomes 0V
and 5V will be output from MICOM No.49. So, when the F-Fan is turned off, both of MICOM 50 & 49 becomes 0V.)
** Other fan motors run with the same principle.
1-3) Oper
Measure b (F-FAN)
High
11.0V
Conditionally
9.5V
Note) According to conditions, the F-Fan and the C-Fan motors are controlled to High and Low RPM. Generally, the
refrigerator operates in High RPM during the peak using time and it runs in Low RPM when the use of the
refrigerator is slow. (For the purpose of performance improvements, the motor RPM, Voltage and Frequency can
be changed without a notice in advance.)
Voltage of motor
Measure c (R-FAN) Measure d(C-FAN)
In the normal operation, MICOM No. 33, 34, 35 and 42 receive a constant frequency; and
10V MICOM defects the signal to check the failure of motor.
10V
(frequency(Hz)×12 = motor rpm)
9.0V 8.3V
82
Remark