Abstract: A speed control circuit for a dc brushless motor includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.

Abstract: A motor speed control circuit includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of a power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.

Abstract: A speed-control drive circuit for a D.C. brushless fan motor includes a pulse width modulation input end for receiving an external pulse width modulation signal for controlling (and changing) the motor speed, and a motor winding drive circuit. The motor winding drive circuit and the pulse width modulation input end are connected to a set of motor windings. The pulse width modulation signal controls the motor winding drive circuit to cause excitation/unexcitation of the set of motor windings and to alternately changes a direction of current such that the set of motor windings adjusts a speed of the fan motor in response to excitation of the set of motor windings responsive to the pulse width modulation signal. The speed of the fan motor increases when an operational period of the pulse width modulation signal increases, and the speed of the fan motor decreases when the operational period of the pulse width modulation signal decreases.

Abstract: A speed control circuit for a dc brushless motor includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.

Abstract: A rotation detection circuit of a dc brushless motor using a fixed bias voltage includes a transistor, and a signal adjuster. The signal adjuster is connected in series between the transistor and driver circuit of the dc brushless motor, for adjusting a signal output by the driver circuit to the according to a fixed bias voltage. The signal adjuster can be selectively supplied with a fixed bias voltage or connected in series with a zener diode. The signal adjuster can be adjusted according to the characteristics of the motor driver circuit, thereby enhancing the design of the rotation detection circuit.

Abstract: A safety-guard detective circuit of a fan motor includes a resistor being adapted to limit a large current input into the motor driver circuit, and a discharge member being adapted to perform grounding to discharge the large current limited by the resistor. The resistor and the release member are commonly connected to the third lead of the motor driver circuit.

Abstract: A dual current-limiting circuit for a dc brushless motor includes an over-current detective circuit, an operation detective circuit, and a current-limiting circuit. The over-current detective circuit produces a voltage signal used to determine whether an over-current has been input to the motor. The operation detective circuit also produces a voltage signal used to determine whether the motor is being operated in a normal manner. The current-limiting circuit decides to turn on a first switch of a first current-limiting circuit and to subsequently turn on a second switch of a second current-limiting circuit depending upon the two voltage signals. The current-limiting circuit is capable of suppressing current passing through a coil at a low voltage level, which is inadequate to damage a driver circuit and still adequate to restart the motor if an abnormal input current is eliminated.

Abstract: The dual current-limiting circuit for dc brushless motor includes an over-current detective circuit, an operation detective circuit, and a current-limiting circuit. The over-current detective circuit produces a voltage signal being used to determine whether the motor has been input over current. The operation detective circuit also produces a voltage signal being used to determine whether the motor is operated in normal. The current-limiting circuit decides to turn on a first switch of a first current-limiting circuit and to subsequently turn on a second switch of a second current-limiting circuit depending upon the two voltage signals. The current-limiting circuit is capable of suppressing current passing through a coil at low voltage level, which is inadequate to damage a driver circuit and still adequate to restart the motor if the great abnormal input current is eliminated.

Abstract: The conversion circuit for a DC brushless motor in accordance with the present invention mainly comprises a rectifier circuit, a power smoothing circuit, and a low-voltage stabilizing circuit. The conversion circuit is used for converting alternating current into direct current for a driver circuit of the motor.

Abstract: The conversion circuit for a DC brushless motor in accordance with the present invention mainly comprises a rectifier circuit, a power smoothing circuit, and a low-voltage stabilizing circuit. The conversion circuit is used for converting alternating current into direct current for a driver circuit of the motor.

Abstract: The speed control circuit in accordance with the present invention mainly includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of power supply to thereby determine the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltage according to the high or low operating voltage.

Abstract: A speed-control drive circuit for a D.C. brushless fan motor comprises a pulse width modulation input end for receiving a pulse width modulation signal and a motor winding drive circuit. The motor winding drive circuit and the pulse width modulation input end are connected to a set of motor winding. The pulse width modulation signal controls the motor winding drive circuit to cause excitation/unexcitation of the set of motor winding and to alternately change a direction of current such that the set of motor winding adjusts a speed of the fan motor in response to excitation of the set of motor winding responsive to the pulse width modulation signal. The speed of said fan motor increases when an operational period of the pulse width modulation signal increases, and the speed of the fan motor decreases when the operational period of the pulse width modulation signal decreases.

Abstract: A safety-guard detective circuit of a fan motor includes a resistor being adapted to limit a large current input into the motor driver circuit, and a discharge member being adapted to perform grounding to discharge the large current limited by the resistor. The resistor and the release member are commonly connected to the third lead of the motor driver circuit.

Abstract: A rotation detective circuit of a dc brushless motor using a fixed bias voltage includes a transistor, and a signal adjuster. The signal adjuster is connected in series between the transistor and a driver circuit of the dc brushless motor, for adjusting signal output a fixed bias voltage from the driver circuit to the transistor. The signal adjuster can be selectively applied a fixed bias voltage manner or connected in series with a zener diode. The signal adjuster can be adjusted according to the feature of the motor driver IC, thereby enhancing the design of the rotation detective circuit.

Abstract: A single-phase motor comprises a [US79KUA] two-phase motor driver IC, a conversion circuit, and a coil for a motor. The driver IC includes two outputs that are serially connected to the conversion circuit and then connected to the coil. The conversion circuit includes two transistors respectively connected two ends of the coil. The outputs of the driver IC respectively send out alternate on/off signals to respectively turn the transistors on and off, thereby controlling directions of current passing the coil. Thus, the coil generates alternative magnetic fields as a result of alternative directions of the current to thereby drive the rotor.

Abstract: A single-phase motor comprises a [US79KUA] two-phase motor driver IC, a conversion circuit, and a coil for a motor. The driver IC includes two outputs that are serially connected to the conversion circuit and then connected to the coil. The conversion circuit includes two transistors respectively connected two ends of the coil. The outputs of the driver IC respectively send out alternate on/off signals to respectively turn the transistors on and off, thereby controlling directions of current passing the coil. Thus, the coil generates alternative magnetic fields as a result of alternative directions of the current to thereby drive the rotor.