Abstract: A fan motor with variable frequency/constant speed control comprises a frequency comparator, a differential integrating circuit, and a differential amplifier. The frequency comparator calculates a frequency difference between a frequency of an external pulse signal input and a frequency of a speed signal detected from the fan. The differential integrating circuit converts the frequency difference into a voltage signal which is inputted to a negative terminal of the differential amplifier. A predetermined voltage is connected to a positive terminal of the differential amplifier. A voltage value at the negative terminal of the differential amplifier is compared with a voltage value at the positive terminal of the differential amplifier to thereby change a voltage outputted to an input end of the fan.

Abstract: A fan motor with constant speed control comprises a microprocessor system, a bus control logic, a register for actual fan speed, a register for fan state, a register for speed set-up, a linear variable voltage circuit control logic, and a braking/running enabling control logic. The microprocessor system is connected via the bus control logic to the register for actual fan speed, the register for fan state, and the register for speed set-up. The register for fan state sets up enabling of braking and running by means of controlling output voltage by the braking/running enabling control logic. The register for speed set-up sets up speed values by the microprocessor system. After comparing a speed value to an actual fan speed signal by the linear variable voltage circuit control logic, the linear variable voltage circuit control logic generates a linear variable voltage (drive voltage) which is outputted to the fan via the braking/running enabling control logic.

Abstract: A fan motor with constant speed control comprises a microprocessor system, a bus control logic, a register for actual fan speed, a register for fan state, a register for speed set-up, a linear variable voltage circuit control logic, and a braking/running enabling control logic. The microprocessor system is connected via the bus control logic to the register for actual fan speed, the register for fan state, and the register for speed set-up. The register for fan state sets up enabling of braking and running by means of controlling output voltage by the braking/running enabling control logic. The register for speed set-up sets up speed values by the microprocessor system. After comparing a speed value to an actual fan speed signal by the linear variable voltage circuit control logic, the linear variable voltage circuit control logic generates a linear variable voltage (drive voltage) which is outputted to the fan via the braking/running enabling control logic.

Abstract: A fan motor with variable frequency/constant speed control comprises a frequency comparator, a differential integrating circuit, and a differential amplifier. The frequency comparator calculates a frequency difference between a frequency of an external pulse signal input and a frequency of a speed signal detected from the fan. The differential integrating circuit converts the frequency difference into a voltage signal which is inputted to a negative terminal of the differential amplifier. A predetermined voltage is connected to a positive terminal of the differential amplifier. A voltage value at the negative terminal of the differential amplifier is compared with a voltage value at the positive terminal of the differential amplifier to thereby change a voltage outputted to an input end of the fan.

Abstract: A variable speed fan motor controlled by a reference voltage comprises a reference voltage circuit and a differential amplifier. The reference voltage circuit outputs a proper reference voltage that is inputted to a negative terminal of the differential amplifier. When the reference voltage inputted to the negative terminal of the differential amplifier is reduced, a drive voltage outputted by the differential amplifier is increased to thereby increase the speed of the fan. When the reference voltage inputted to the negative terminal of the differential amplifier is increased, the drive voltage outputted by the differential amplifier is reduced to thereby decrease the speed of the fan.

Abstract: A thermal control variable speed fan motor comprises a rectifying circuit, a differential amplifier, and a temperature-sensing circuit. The rectifying circuit converts a speed signal detected from the fan into a voltage that is outputted to a negative terminal of the differential amplifier. A positive terminal of the differential amplifier is connected to the temperature-sensing circuit that is connected in series with a power source. The temperature-sensing circuit includes a temperature sensor having a resistance that varies in response to a change in ambient temperature. When ambient temperature rises, the drive voltage outputted by the differential amplifier increases and the fan speed increases. When ambient temperature reduces, the drive voltage decreases and the fan speed decreases, thereby changing the fan speed linearly by thermal control.

Abstract: A fan motor having a two-step speed control includes a buffer circuit, a control voltage terminal, and a fan. The buffer circuit is mounted between a voltage source and a source terminal of the fan. The buffer circuit includes a resistor and a transistor. The control voltage terminal is connected to a transistor of the buffer circuit to control conduction or non-conduction of the transistor, thereby changing the voltage of the source terminal of the fan. The varying voltage waveforms are smooth linear waveforms such that rotating speed of the fan is increased or decreased gradually during switching between a low-speed operation mode and a high-speed operation speed.

Abstract: A fan motor whose speed is controlled by an operating period of pulse waves includes first and second rectifying circuits, a voltage comparison circuit, and a differential amplifier. A pulse wave is inputted into the first rectifying circuit, an actual speed signal detected from the fan is inputted into the second rectifying circuit, and the pulse wave and the speed signal are compared in the voltage comparison circuit. After comparison, a comparison voltage is outputted to a negative terminal of the differential amplifier. A partial voltage from a source voltage is connected to a positive terminal of the differential amplifier. The differential amplifier outputs a drive voltage after calculating a voltage difference between the comparison voltage and the partial voltage. Speed of the fan is changed in response to a change in the value of the drive voltage.