Abstract: A driving circuit of a fan includes a magnetic pole sensor for generating a magnetic pole sensing signal, a first waveform generator coupled to the magnetic pole sensor for generating a first waveform according to the magnetic pole sensing signal, a second waveform generator for generating a second waveform, a comparison circuit coupled to the first waveform generator and the second waveform generator for comparing the first waveform and the second waveform for generating a third waveform, a control signal generator coupled to the comparison circuit for generating a control signal according to the third waveform and an external signal, and a current generator coupled to the magnetic pole sensor and the control signal generator for outputting current to a coil of a stator of the fan according to the magnetic pole sensing signal and the control signal.

Abstract: A driving circuit of a fan includes a magnetic pole sensor for generating a magnetic pole sensing signal, a first waveform generator coupled to the magnetic pole sensor for generating a first waveform according to the magnetic pole sensing signal, a second waveform generator for generating a second waveform, a comparison circuit coupled to the first waveform generator and the second waveform generator for comparing the first waveform and the second waveform for generating a third waveform, a control signal generator coupled to the comparison circuit for generating a control signal according to the third waveform and an external signal, and a current generator coupled to the magnetic pole sensor and the control signal generator for outputting current to a coil of a stator of the fan according to the magnetic pole sensing signal and the control signal.

Abstract: A noiseless driving circuit for direct current (DC) motor is disclosed. The driving circuit uses a magnetic-field sensing circuit with a Hall sensor to sense the corresponding position of the permanent magnet rotor. According to the corresponding position of the permanent magnet rotor, a linear circuit generates a signal with trapezoid waveform for driving the coil of the DC motor. The coils of the DC motor perform soft switching operations without resulting backing electromotive force (BEMF). Therefore, the noise during the operation of the DC motor can be substantially reduced.

Abstract: A noiseless driving circuit for direct current (DC) motor is disclosed. The driving circuit uses a magnetic-field sensing circuit with a Hall sensor to sense the corresponding position of the permanent magnet rotor. According to the corresponding position of the permanent magnet rotor, a linear circuit generates a signal with trapezoid waveform for driving the coil of the DC motor. The coils of the DC motor perform soft switching operations without resulting backing electromotive force (BEMF). Therefore, the noise during the operation of the DC motor can be substantially reduced.