Temperature controlled radiating fan

A temperature controlled radiating fan comprises a temperature detector, a control circuit, a power control circuit, a regulator, a loading circuit, and a driving circuit. The temperature detector is connected to the control circuit. The output of the control circuit is connected to the power control circuit. The output of the power control circuit is connected to the loading circuit. The output of the loading circuit is connected to the driving circuit. The power control circuit is connected to the regulator. Thereby, the rotary speed of the fan motor is varied according to a voltage variation, so that the characteristic of the rotary speed of the fan motor is linearly changed.

FIELD OF THE INVENTION
 The present invention relates to a temperature controlled radiating fan,
 and especially to radiating fan wherein the rotary speed of the fan motor
 is varied according to a voltage variation, so that the characteristic of
 the rotary speed of the fan motor is linearly changed.
 BACKGROUND OF THE INVENTION
 In the prior art temperature controlled radiating fan, a pulse width
 modulation (PWM) serves to change the modulation way of the rotary speed
 of the fan motor, such as those disclosed in Taiwan Patent No. 0327486,
 "DC brushless fan PWM control circuit", No. 0152583, "PWM DC brushless
 radiating fan", and No. 0146147, "AC motor stageless speed change PWM
 control".
 However, the prior art designs have the disadvantages of larger volume,
 many components, high manufacturing cost, worse linearity. Thus, there is
 an eager demand for a temperature controlled radiating fan having a
 control circuit which is varied linearly according to a voltage variation.
 SUMMARY OF THE INVENTION
 Accordingly, the primary object of the present invention is to provide a
 temperature controlled radiating fan. The temperature controlled radiating
 fan comprises a temperature detector, a control circuit, a power control
 circuit, a regulator, a loading circuit and a driving circuit. Thereby,
 the rotary speed of the fan motor is varied according to a voltage
 variation, so that the characteristic of the rotary speed of the fan motor
 is linearly changed.
 Another object of the present invention is to provide a temperature
 controlled radiating fan which has the advantages of a small volume, a low
 cost and a preferred characteristic.
 The various objects and advantages of the present invention will be more
 readily understood from the following detailed description when read in
 conjunction with the appended drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 With reference to FIGS. 1 and 2, The temperature controlled radiating fan
 of the present invention is illustrated herein. The temperature controlled
 radiating fan has a temperature detector 1, a control circuit 2, a power
 control circuit 3, a loading circuit 4, a regulator 5, a driving circuit
 6, and other unit.
 The temperature detector 1 is a thermistor (NTS). The resistance of the
 thermistor is inversely proportional to the temperature variation. Namely,
 as temperature increases, the resistance of the resistance reduces. As
 temperature reduces, the resistance of the thermistor increased.
 The input end of the control circuit 2 is connected to the temperature
 detector 1 and is formed by connecting the transistor Q1, resistor R1 and
 R2. The control circuit 2 is operated according to the variation of the
 resistance of the temperature detector 1. Namely, when the resistance of
 the temperature detector 1 reduces so that the voltage between two ends of
 the resistor R3 is larger than that between the base and emitter of the
 transistor Q1, the transistor Q1 is conductive. On the contrary, the
 transistor Q1 will not conduct.
 The power control circuit 3 is connected to the collector of the transistor
 Q1 of the control circuit 2 and is formed by connecting the power source
 Vcc, transistor Q2, and resistor R4. The transistor Q2 of the power
 control circuit 3 is actuated when the transistor Q1 is conductive.
 The regulator 5 is connected to the collector of the transistor Q2 of the
 power control circuit 3 and is formed by connected a transistor Q3, a
 resistor R5, a Zener diode Z1, and other elements.
 The regulator 5 provides power to the fan motor when the motor rotates in a
 low speed. That is, when the transistor Q2 does not conduct, the voltage
 of the Zener diode ZD1 is larger than the voltage between the base and
 emitter of the transistor Q3 so that the transistor Q3 is conductive and
 thus sustained in a low potential.
 The loading circuit 4 is connected to the collector of the transistor Q2 of
 the power control circuit 3 and the emitter of the transistor Q3 of the
 regulator 5. The loading circuit is formed by connecting inductance L1 and
 L2. The output end of the loading circuit 4 is connected to a driving
 circuit 6 formed by IC U1 and U2 and capacitor C1 and C2.
 The loading circuit 4 is actuated by the stimulation of the output voltage
 of the power control circuit 3 and the regulator 5.
 Referring to FIG. 3, the characteristic curve of the fan motor and
 temperatures are illustrated.
 As temperature is between 0-T1, the resistance of the temperature detector
 1 increases so that the transistor Q1 does not conduct. Now, the
 transistor Q3 conducts so that the emitter of the transistor Q3 is
 retained in a low level. Therefore, the coils L1 and L2 are stimulated due
 to the low level and thus, the rotary speed of the fan motor is retained
 in a preset value (r1).
 When the temperature (T1-T2) increase, the resistance of the temperature
 detector reduces, and thus, the transistor Q1 conducts. As a result, the
 potential of the collector in the transistor Q1 reduces. Therefore, the
 transistor Q2 conducts so that the rotary speed of the fan motor (r1-r2)
 is linearly varied according to the potential of the collector of the
 transistor Q2.
 As temperature is increased to a predetermined value (T2) so that the
 collector of the transistor Q2 is retained in a high level. Then, the
 rotary speed of the fan motor is retained in a setting value (r2).
 Referring to FIG. 4, in the present invention, a protecting element (diode)
 7 can be connected between the loading circuit 4 and the regulator 5 for
 preventing that the transistor Q3 is burned out.
 In summary, the voltage adjusting of the present invention has the
 following advantage:
 (1) A good working characteristic curve.
 (2) A small volume.
 (3) Less peripheral components.
 (4) Lower cost.
 Although the present invention has been described with reference to the
 preferred embodiments, it will be understood that the invention is not
 limited to the details described thereof. Various substitutions and
 modifications have been suggested in the foregoing description, and others
 will occur to those of ordinary skill in the art. Therefore, all such
 substitutions and modifications are intended to be embraced within the
 scope of the invention as defined in the appended claims.