Abstract: A drive circuit for a brushless DC fan motor for rotating a rotor (permanent magnet) by a rotating magnetic field produced by turning on/off the flow of electric current to field coils by a signal to control terminals of switch elements in which switch sections are each connected in series with the field coils. When connecting capacitors for absorbing a current spike in parallel with the switch sections of the switch elements, resistors are each connected between the field coil and switch section, through which the capacitors are connected in parallel with the switch sections. A discharge current of the capacitors which absorbed a current spike when turning on the switch elements is passed via the resistors, thereby eliminating a current spike.

Abstract: A booster circuit for a pre-drive circuit of a brushless direct current single-phase motor. When a series pair of power FETs of the drive circuit turn on, one boost control switching element of the pre-drive circuit turns on, another series pair of power FETs of the drive circuit turn off, and the other boost control switching element of the pre-drive circuit turns off. The booster circuit provides a continuous stable output voltage to the motor.

Abstract: A pre-drive circuit for a brushless DC single-phase motor permits a cost reduction and an easy adjustment for the control input voltage of a switching device adjacent to a power source in a wider range, especially in increasing the control input voltage. In a drive circuit having four switching devices making up an H-bridge circuit with a motor coil being sandwiched therebetween, a control voltage exceeding a power supply voltage is required to turn ON the switching devices adjacent to the power source. The pre-drive circuit changes the duty ratio of the control voltage controlling motor speed. A circuit unit for generating pulse signals for controlling the switching devices uses an inexpensive logic circuit.

Abstract: There is provided a brushless DC fan motor which can eliminate an oscillator for PWM, control the motor speed at a low cost with high accuracy, and efficiently adjust the temperature in a housing for electronic appliances when radiating the heat in the housing. The brushless DC fan motor with the rotational speed thereof controlled by controlling the voltage of a control input terminal of a drive circuit comprises a differential amplifier in which the voltage signal for controlling the speed is inputted in a first input terminal and the reference voltage signal is inputted in a second input terminal. The differential amplifier is linear in the input-output characteristic, and can set the rise characteristic of a desired gradient, and control the motor speed with high accuracy without using the PWM signal for the input signal. The voltage signal from the output terminal of the differential amplifier is given to the control input terminal of the drive circuit.

Abstract: A drive circuit for a brushless DC fan motor for rotating a rotor (permanent magnet) by a rotating magnetic field produced by turning on/off the flow of electric current to field coils by a signal to control terminals of switch elements in which switch sections are each connected in series with the field coils. When connecting capacitors for absorbing a current spike in parallel with the switch sections of the switch elements, resistors are each connected between the field coil and switch section, through which the capacitors are connected in parallel with the switch sections. A discharge current of the capacitors which absorbed a current spike when turning on the switch elements is passed via the resistors, thereby eliminating a current spike.

Abstract: A pre-drive circuit for a brushless DC single-phase motor permits a cost reduction and an easy adjustment for the control input voltage of a switching device adjacent to a power source in a wider range, especially in increasing the control input voltage. In a drive circuit having four switching devices making up an H-bridge circuit with a motor coil being sandwiched therebetween, a control voltage exceeding a power supply voltage is required to turn ON the switching devices adjacent to the power source. The pre-drive circuit changes the duty ratio of the control voltage controlling motor speed. A circuit unit for generating pulse signals for controlling the switching devices uses an inexpensive logic circuit.

Abstract: There is provided a brushless DC fan motor which can eliminate an oscillator for PWM, control the motor speed at a low cost with high accuracy, and efficiently adjust the temperature in a housing for electronic appliances when radiating the heat in the housing. The brushless DC fan motor with the rotational speed thereof controlled by controlling the voltage of a control input terminal of a drive circuit comprises a differential amplifier in which the voltage signal for controlling the speed is inputted in a first input terminal and the reference voltage signal is inputted in a second input terminal. The differential amplifier is linear in the input-output characteristic, and can set the rise characteristic of a desired gradient, and control the motor speed with high accuracy without using the PWM signal for the input signal. The voltage signal from the output terminal of the differential amplifier is given to the control input terminal of the drive circuit.

Abstract: A booster circuit for a pre-drive circuit of a brushless direct current single-phase motor. When a series pair of power FETs of the drive circuit turn on, one boost control switching element of the pre-drive circuit turns on, another series pair of power FETs of the drive circuit turn off, and the other boost control switching element of the pre-drive circuit turns off. The booster circuit provides a continuous stable output voltage to the motor.

Abstract: A pre-drive circuit for a brushless DC single-phase motor controls a motor rotational speed by driving a drive circuit for the motor. The drive circuit includes four switching elements, namely, two power-supply-side switching elements and two ground-side switching elements connected in an H configuration bridge across a motor coil of the motor. A control voltage above a power supply voltage is required to turn on the two power-supply-side switching elements. The pre-drive circuit to produce a signal for controlling the switching elements is formed of an inexpensive logic circuit. Signals for controlling the two power-supply-side switching elements are amplified to a voltage level above a power supply voltage by 4 V by operational amplifiers. Drive signal input circuits for feeding signals for controlling the two ground-side switching elements to control input terminals of the two ground-side switching elements are formed of mere respective resistors.

Abstract: There is provided a current limiting circuit to eliminate any harsh grating noise attributable to the decrease in an ON-OFF frequency of an electrified current from a normal range, for example, below 1 kHz when starting a brushless DC fan motor.

Abstract: A drive circuit for a brushless DC fan motor for rotating a rotor (permanent magnet) by a rotating magnetic field produced by turning on/off the flow of electric current to field coils by a signal to control terminals of switch elements in which switch sections are each connected in series with the field coils. When connecting capacitors for absorbing a current spike in parallel with the switch sections of the switch elements, resistors are each connected between the field coil and switch section, through which the capacitors are connected in parallel with the switch sections. A discharge current of the capacitors which absorbed a current spike when turning on the switch elements is passed via the resistors, thereby eliminating a current spike.

Abstract: A pre-drive circuit for a brushless DC single-phase motor controls a motor rotational speed by driving a drive circuit for the motor. The drive circuit includes four switching elements, namely, two power-supply-side switching elements and two ground-side switching elements connected in an H configuration bridge across a motor coil of the motor. A control voltage above a power supply voltage is required to turn on the two power-supply-side switching elements. The pre-drive circuit to produce a signal for controlling the switching elements is formed of an inexpensive logic circuit. Signals for controlling the two power-supply-side switching elements are amplified to a voltage level above a power supply voltage by 4 V by operational amplifiers. Drive signal input circuits for feeding signals for controlling the two ground-side switching elements to control input terminals of the two ground-side switching elements are formed of mere respective resistors.

Abstract: A pre-drive circuit for a brushless DC single-phase motor permits a cost reduction and an easy adjustment for the control input voltage of a switching device adjacent to a power source in a wider range, especially in increasing the control input voltage. In a drive circuit having four switching devices making up an H-bridge circuit with a motor coil being sandwiched therebetween, a control voltage exceeding a power supply voltage is required to turn ON the switching devices adjacent to the power source. The pre-drive circuit changes the duty ratio of the control voltage controlling motor speed. A circuit unit for generating pulse signals for controlling the switching devices uses an inexpensive logic circuit.

Abstract: A drive circuit for a brushless DC fan motor for rotating a rotor (permanent magnet) by a rotating magnetic field produced by turning on/off the flow of electric current to field coils by a signal to control terminals of switch elements in which switch sections are each connected in series with the field coils. When connecting capacitors for absorbing a current spike in parallel with the switch sections of the switch elements, resistors are each connected between the field coil and switch section, through which the capacitors are connected in parallel with the switch sections. A discharge current of the capacitors which absorbed a current spike when turning on the switch elements is passed via the resistors, thereby eliminating a current spike.

Abstract: There is provided a current limiting circuit to eliminate any harsh grating noise attributable to the decrease in an ON-OFF frequency of an electrified current from a normal range, for example, below 1 kHz when starting a brushless DC fan motor.

Abstract: There is provided a brushless DC fan motor which can eliminate an oscillator for PWM, control the motor speed at a low cost with high accuracy, and efficiently adjust the temperature in a housing for electronic appliances when radiating the heat in the housing. The brushless DC fan motor with the rotational speed thereof controlled by controlling the voltage of a control input terminal of a drive circuit comprises a differential amplifier in which the voltage signal for controlling the speed is inputted in a first input terminal and the reference voltage signal is inputted in a second input terminal. The differential amplifier is linear in the input-output characteristic, and can set the rise characteristic of a desired gradient, and control the motor speed with high accuracy without using the PWM signal for the input signal. The voltage signal from the output terminal of the differential amplifier is given to the control input terminal of the drive circuit.