Abstract: A cooling fan module for a heat exchanger or the like, has a motor, a fan driven by the motor and a speed controller connected between the motor and a power supply. The speed controller is configured to operate the motor in a high speed mode and a low speed mode. The speed controller includes a high speed branch and a low speed branch connected in parallel. The low speed branch includes a pulse width modulation circuit configured to reduce an average voltage by a fixed duty ratio to achieve a low speed operation of the motor. By eliminating the conventional voltage dropping resistor, the speed controller reduces the power consumption, thus increasing the efficiency of the module, in the low speed mode of operation.

Abstract: A cooling fan module for a heat exchanger or the like, has a motor, a fan driven by the motor and a speed controller connected between the motor and a power supply. The speed controller is configured to operate the motor in a high speed mode and a low speed mode. The speed controller includes a high speed branch and a low speed branch connected in parallel. The low speed branch includes a pulse width modulation circuit configured to reduce an average voltage by a fixed duty ratio to achieve a low speed operation of the motor. By eliminating the conventional voltage dropping resistor, the speed controller reduces the power consumption, thus increasing the efficiency of the module, in the low speed mode of operation.