BLOWER FAN CONTROLLER [MANUAL AIR CONDITIONER]

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Purpose

• The blower fan controller controls the blower motor rotation speed.

Function

• The blower fan controller controls the built-in power MOS FET using pulse signals and changes the blower motor operational voltage.

• Temperature increase is suppressed by installing the fin to the upper part of the blower fan controller.

• The blower fan controller is equipped with a fail-safe function for the purpose of protecting the internal circuits.

Construction

• The blower fan controller is installed to the A/C unit.

• The blower fan controller is built into the PWM circuit.

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PWM (Pulse Width Modulation) circuit

• The PWM circuit controls the blower motor rotation speed using pulse.

• The PWM circuit decides duty ratio (pulse ON time) based on the signals from the climate control unit and turns the power MOS FET on/off at high speed.

• With the power MOS FET turned on, current flows between the drain and source while current is flowing to the gate.

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• The rotation of the blower motor is fast when the power MOS FET ON period is long (duty ratio is high), and it is slow when the period is short (duty ratio is low).

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• The PWM circuit lowers the electric power loss to suppress heat generation in the circuit by performing duty control which uses power MOS FET ON/OFF operation.

Operation

1. When the blower fan controller receives a blower speed request signal from the climate control unit, it controls the drive circuit to determine the duty ratio for the blower motor rotation.

2. The power MOS FET is turned on or off based on the duty ratio determined by the drive circuit.

3. When the power MOS FET is turned on, the blower motor circuit is established and the motor rotates.

4. The power MOS FET is turned on or off at high speed repeatedly to control the blower motor rotation. Therefore the motor rotation speed is controlled.

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Fail-safe

• The blower fan controller stops output when the following conditions are detected:

― Motor lock

• The blower motor locks and over-current flows.

― Abnormal temperature

• The power MOS FET increases abnormal temperature due to half-lock (over-current such as motor-lock is not detected) of the blower motor.