Patent ID: 6297608
Filing Date: 2001-10-02
Classification: F04D

Abstract:
A drive circuit for a speed automatically adjusted fan, comprising:two coils (V1, V2) in a DC fan, being connected to a power source;an actuating circuit (10), providing a Hall integrated circuit, and a first and a second transistors (Q1, Q2) to connect with the coils (V1, V2) respectively;a current control circuit (30), providing a third transistor (Q3) and a resistor (R3) to connect the first transistor (Q1) and the second transistor (Q2); anda temperature control circuit (20), providing a first end connecting with the power source too, and a second end being grounded;characterized in that the temperature control circuit (20) has a heat sensitive resistor RN(NTC) near the first end thereof and a resistor (R4) near the second end thereof, and a base pole of the third transistor (Q3) in the current control circuit (30) connects with the temperature control circuit through the resister (R3) and a collector of the third transistor (Q3) connects with a respective emitter of the first and the second transistor (Q1, Q2);whereby, the higher an ambient temperature surrounding the heat sensitive resistor RN(NTC) is, the smaller a resistance of the heat sensitive resistor RN(NTC) is such that more current may be flowed into the current control circuit and the speed of the fan becomes faster.