Abstract: A rotation speed control device for a heat-dissipating fan includes an impedance unit, a regulating unit, and a driving circuit. The impedance unit includes a first resistor having a first end connected to a first node, and a second end connected to a second node, and a second resistor having a third end connected to the second node, and a fourth end. The regulating unit is connected to the impedance unit and is configurable for varying an effective impedance of the impedance unit to adjust magnitude of current flowing through the impedance unit. The driving circuit is connected to the impedance unit and is adapted to control rotation speed of the heat-dissipating fan according to the magnitude of the current flowing through the impedance unit.

Abstract: A over heat protection circuit for a brushless dc motor includes a thermal sensitive resistor, a resistor and a transistor. The thermal sensitive resistor and the resistor are commonly connected to a base of the transistor while an emitter of the transistor connecting to a motor coil. The thermal sensitive resistor has a resistance value which can be changed in response to an operational temperature. The thermal sensitive resistor is preset to operate at a safety temperature within a predetermined thermal preference. When the operational temperature of the motor coil exceeds the safety temperature, the over heat protection circuit may to cut off a motor current so that the motor coil is protected.

Abstract: A parallel connected double-phase full-wave brushless dc motor includes a first drive member, a second drive member, a first sensor member, a second sensor member, a first motor coil and a second motor coil. The first drive member is connected to the first sensor member and the first motor coil, and the second drive member is connected to the second sensor member and the second motor coil. Hall signals of the first sensor member and the second sensor member are in control of an alternative direction of a first current and a second current passing through the first motor coil and the second motor coil. Thereby, the first motor coil and the second motor coil are excited in full wave. In operation, the first motor coil and the second motor coil are excited synchronous due to the parallel connection of the first motor coil and the second motor coil.

Abstract: A thermally suppressing circuit includes a restart-charging drive member, a coil set, a restart-charging capacitor, and a charging switch set. The restart-charging drive member is electrically connected to the coil set and the restart-charging capacitor while the charging switch set is connected between the coil set and the restart-charging capacitor. The charging switch set is used to access signals output from the restart-charging drive member. In abnormal operation, as the restart-charging drive member may turn on an auto-restart function to output a high or low voltage signal, the charging switch set is turned on to accelerate charging the restart-charging capacitor to thereby avoid overcurrent passing the coil set.

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 thermally suppressing circuit mainly comprises a restart-discharging drive member, a coil set, a restart-discharging capacitor, and a discharging switch set. The restart-discharging drive member is electrically connected to the coil set and the restart-discharging capacitor while the discharging switch set connected between the coil set and the restart-discharging capacitor. The discharging switch set is used to access signals output from the restart-discharging drive member. In abnormal operation, as the restart-discharging drive member may turn on an auto-restart function to output a high or low voltage signal, the discharging switch set is turned on to accelerate discharging the restart-discharging capacitor to thereby avoid overcurrent passing the coil set.

Abstract: An overvoltage protective circuit includes an overvoltage protective element, a first resistor, a second resistor, a first transistor and a second transistor. The overvoltage protective element is connected a power source to a motor drive circuit, and a ground line for discharging overvoltage. The first resistor is provided with a first voltage reference for the second transistor to turn it on or off. The first transistor is connected with the second transistor to constitute a switch set which is connected between the overvoltage protective element and the motor drive circuit so as to discharge overvoltage supplied from the power source. The second resistor is provided with a second voltage reference for the first transistor to turn it on or off. Supplying overvoltage from the power source, the overvoltage protective element actuates the second transistor to turn on for grounding overvoltage and turning off the first transistor so as to cut off the motor drive circui.

Abstract: A brushless dc motor includes a fan motor drive circuit, an over-current-detecting/current-limiting circuit and a multi-functional speed control circuit. The fan motor drive circuit is connected to the over-current-detecting/current-limiting circuit which is further connected to the multi-functional speed control circuit. The over-current-detecting/current-limiting circuit is adapted to detect a rotational speed and an over-current. Detecting an over-current, the over-current-detecting/current-limiting circuit controls a current at a low voltage level for passing through the fan motor drive circuit and inadequate to destroy it. The multi-functional speed control circuit sends a predetermined speed signal to control the over-current-detecting/current-limiting circuit for carrying out speed control of the brushless dc motor.

Abstract: A limiting circuit for a brushless dc motor in accordance with the present invention comprises a first transistor, a second transistor, a first resistor and a second resistor. The first transistor, the second transistor, the first resistor and the second resistor are arranged in complementary connection to constitute the limiting circuit which has a first terminal connected to a power source and a second terminal connected to a motor drive circuit.

Abstract: A serially connected double-phase full-wave brushless dc motor includes a first drive member, a second drive member, a first sensor member, a second sensor member, a first motor coil and a second motor coil. The first drive member is connected to a power source to thereby obtain a first voltage, and connected to the first sensor member and the first motor coil. The first drive member is further in serial connection with a second drive member and a second sensor member, and provides with a second voltage thereto. The second drive member is connected to the second sensor member and the second motor coil. Hall signals of the first and second sensor members are in control of an alternative direction of the first and second motor coils for conduction, and thereby the first and second motor coils are synchronously excited in full wave by the first and second voltages respectively.

Abstract: A speed control circuit for a brushless dc motor includes a motor drive circuit, a drive member and a PWM control circuit. The motor drive circuit includes at least one coil and at least one transistor serially connected to the coil. The drive member is provided with a plurality of output terminals adapted to output a driving signal to the transistor of the motor drive circuit. The PWM control circuit is in connection between the transistor of the motor drive circuit and the output terminal of the drive member, thereby turning the transistor on or off.

Abstract: A parallel connected double-phase full-wave brushless dc motor includes a first drive member, a second drive member, a first sensor member, a second sensor member, a first motor coil and a second motor coil. The first drive member is connected to the first sensor member and the first motor coil, and the second drive member is connected to the second sensor member and the second motor coil. Hall signals of the first sensor member and the second sensor member are in control of an alternative direction of a first current and a second current passing through the first motor coil and the second motor coil. Thereby, the first motor coil and the second motor coil are excited in full wave. In operation, the first motor coil and the second motor coil are excited synchronous due to the parallel connection of the first motor coil and the second motor coil.

Abstract: A serially connected double-phase full-wave brushless dc motor includes a first drive member, a second drive member, a first sensor member, a second sensor member, a first motor coil and a second motor coil. The first drive member is connected to a power source to thereby obtain a first voltage, and connected to the first sensor member and the first motor coil. The first drive member is further in serial connection with a second drive member and a second sensor member, and provides with a second voltage thereto. The second drive member is connected to the second sensor member and the second motor coil. Hall signals of the first and second sensor members are in control of an alternative direction of the first and second motor coils for conduction, and thereby the first and second motor coils are synchronously excited in full wave by the first and second voltages respectively.

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 double-phase half-wave brushless dc motor in accordance with the present invention includes a first sensor/drive member, a second sensor/drive member, a first motor coil and a second motor coil. Each of the sensor/drive members has two pins for electrical connection. Each of the motor coils is consisted of a first terminal and a second terminal for electrical connection. The first terminals of the first and second motor coils are commonly connected to a power source. The second terminal of the first motor coil is connected to one of the pins of the first sensor/drive member and one of the pins of the second sensor/drive member in common. And, the second terminal of the second motor coil is connected to the other pin of the first sensor/drive member and the other pin of the second sensor/drive member in common.

Abstract: A speed control circuit for a brushless dc motor includes a motor drive circuit, a drive member and a PWM control circuit. The motor drive circuit includes at least one coil and at least one transistor serially connected to the coil. The drive member is provided with a plurality of output terminals adapted to output a driving signal to the transistor of the motor drive circuit. The PWM control circuit is in connection between the transistor of the motor drive circuit and the output terminal of the drive member, thereby turning the transistor on or off.

Abstract: A over heat protection circuit for a brushless dc motor includes a thermal sensitive resistor, a resistor and a transistor. The thermal sensitive resistor and the resistor are commonly connected to a base of the transistor while an emitter of the transistor connecting to a motor coil. The thermal sensitive resistor has a resistance value which can be changed in response to an operational temperature. The thermal sensitive resistor is preset to operate at a safety temperature within a predetermined thermal preference. When the operational temperature of the motor coil exceeds the safety temperature, the over heat protection circuit may to cut off a motor current so that the motor coil is protected.

Abstract: A limiting circuit for a brushless dc motor in accordance with the present invention comprises a first transistor, a second transistor, a first resistor and a second resistor. The first transistor, the second transistor, the first resistor and the second resistor are arranged in complementary connection to constitute the limiting circuit which has a first terminal connected to a power source and a second terminal connected to a motor drive 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: A thermally suppressing circuit mainly comprises a restart-charging drive member, a coil set, a restart-charging capacitor, and a charging switch set. The restart-charging drive member is electrically connected to the coil set and the restart-charging capacitor while the charging switch set connected between the coil set and the restart-charging capacitor. The charging switch set is used to access signals output from the restart-charging drive member. In abnormal operation, as the restart-charging drive member may turn on an auto-restart function to output a high or low voltage signal, the charging switch set is turned on to accelerate charging the restart-charging capacitor to thereby avoid overcurrent passing the coil set.