초록 ▼

A fan system includes a fan, a hysteresis circuit including a temperature sensor, a first operational amplifier having a negative input end coupled to the temperature sensor, and a second operational amplifier having a negative input end coupled to an output end of the first operational amplifier an

A fan system includes a fan, a hysteresis circuit including a temperature sensor, a first operational amplifier having a negative input end coupled to the temperature sensor, and a second operational amplifier having a negative input end coupled to an output end of the first operational amplifier and having a positive input end coupled to a power supply for outputting a first voltage when the temperature sensed by the temperature sensor is greater than a first temperature, and for outputting a second voltage when the temperature sensed by the temperature sensor is lower than a second temperature. The fan system further includes a fan switch coupled to the hysteresis circuit and the fan for controlling a rotational speed of the fan according to the first voltage or the second voltage outputted from the hysteresis circuit. The first temperature is greater than the second temperature.

대표청구항 ▼

What is claimed is: 1. A fan system with hysteresis character, the fan system comprising: a fan; a hysteresis circuit comprising: a temperature sensor; a first operational amplifier having a first negative input end coupled to the temperature sensor and a first output end; and a second operational

What is claimed is: 1. A fan system with hysteresis character, the fan system comprising: a fan; a hysteresis circuit comprising: a temperature sensor; a first operational amplifier having a first negative input end coupled to the temperature sensor and a first output end; and a second operational amplifier having a second negative input end coupled to the first output end and having a second positive end coupled to a first power supply for outputting a first voltage when the temperature sensed by the temperature sensor is greater than a first temperature, and for outputting a second voltage when the temperature sensed by the temperature sensor is lower than a second temperature and a second output end; and a fan switch comprising a metal-oxide semiconductor (MOS) coupled to the hysteresis circuit and the fan for controlling a rotational speed according to the first voltage or the second voltage outputted by the hysteresis circuit; wherein the first temperature is greater than the second temperature. 2. The fan system of claim 1 wherein when power level of a first positive input end is greater than power level of the first negative input end, the first output end is open, and when power level of the second positive input end is higher than the power level of the second negative input end, the second output end is open. 3. The fan system of claim 1 wherein the hysteresis circuit further comprises a pull-high resistor coupled to the second output end and a second power supply for enhancing the voltage of the fan switch when the second output end is open. 4. The fan system of claim 1 wherein the temperature sensor is a negative temperature coefficient heat sensitive conductance. 5. The fan system of claim 1 wherein the fan system further comprises: a bipolar junction transistor comprising an emitter, a collector, and a base, the emitter being coupled to a third power supply, and the collector being coupled to the fan; wherein the MOS comprises a source, a drain, and a gate, the drain being coupled to the base of the bipolar junction transistor, the source being coupled to a ground end, and the gate being coupled to the hysteresis circuit for receiving voltage signals transmitted from the hysteresis circuit in order to control on and off of the bipolar junction transistor. 6. The fan system of claim 5 wherein the fan switch further comprises a resistor, an end of the resistor coupled to the fan, another end of the resistor coupled to the third power supply that is also coupled to the emitter of the bipolar junction transistor. 7. The fan system of claim 5 wherein the fan system further comprises a capacitance coupled to the collector of the bipolar junction transistor for storing electric charge supplied to rotate the fan. 8. An interface capable of controlling fan speed according to temperature change, the interface comprising: at least one electronic component, the electronic component generating different temperatures according operation condition; a fan; a hysteresis circuit, comprising: a temperature sensor coupled to the electronic component; a first operational amplifier having a first negative input end coupled to the temperature sensor and a first output end; and a second operational amplifier having a second negative input end coupled to the first output end, and a second positive input end coupled to a first power supply for outputting a first voltage when the temperature sensed by the temperature sensor is greater than a first temperature, and for outputting a second voltage when the temperature sensed by the temperature sensor is lower than a second temperature and a second output end; and a fan switch comprising a metal-oxide semiconductor (MOS) coupled to the hysteresis circuit and the fan, the fan switch is utilized for controlling the fan speed according to the first voltage or the second voltage outputted by the hysteresis circuit; wherein the first temperature is greater than the second temperature. 9. The interface of claim 8 wherein the temperature sensor is a negative temperature coefficient heat sensitive conductance. 10. The interface of claim 8 wherein the fan switch further comprises: a bipolar junction transistor comprising an emitter, a collector, and a base, the emitter being coupled to a third power supply, and the collector being coupled to the fan; wherein the MOS comprises semiconductor (MOS) a source, a drain, and a gate, the drain being coupled to the base of the bipolar junction transistor, the source being coupled to a ground end, and the gate being coupled to the hysteresis circuit for receiving voltage signals transmitted from the hysteresis circuit in order to control on and off of the bipolar junction transistor. 11. The interface of claim 10 wherein the fan switch further comprises a resistor, an end of the resistor coupled to the third power supply that is also coupled to the emitter of the bipolar junction transistor. 12. The interface of claim 10 wherein the fan switch further comprises a capacitance coupled to the collector of the bipolar junction transistor for storing electric charge supplied to rotate the fan. 13. The interface of claim 10 wherein the interface is a display interface.