Wind speed detecting circuit capable of detecting the timing for replacing dust-proof element of electronic device

A wind speed detecting circuit includes a heating unit, a first temperature sensor, a second temperature sensor, a control unit and a driving unit. The first temperature sensor detects a first temperature of an internal portion of an electronic device, thereby generating a first detecting signal. The second temperature sensor detects a second temperature of the heating unit, thereby generating a second detecting signal. The control unit generates a modulation signal according to the first detecting signal and the second detecting signal. In response to the modulation signal, the driving unit generates a driving signal to control operations of the heating unit, so that a temperature difference between the first temperature and the second temperature is maintained constant. A specified relation between the wind speed and the modulation signal facilitates discriminating whether a dust-proof element of the electronic device needs to be replaced.

FIELD OF THE INVENTION

The present invention relates to a wind speed detecting circuit, and more particularly to a wind speed detecting circuit for discriminating whether a dust-proof element of an electronic device needs to be replaced with a new one.

BACKGROUND OF THE INVENTION

With increasing development of high technology industries, various electronic devices such as power supply apparatuses, air conditioners or projectors become indispensable in our daily lives. During operations of these electronic devices, a great amount of heat is generated. The system stability and the use lives of these electronic devices are dependent on the capability of removing heat.

Take a power supply apparatus for example. The power supply apparatus usually has a fan for quickly removing heat generated during operation of the power supply apparatus. The fan may provide forced airflow for exhausting warm air from the internal portion of the power supply apparatus to the airflow outlet of the power supply apparatus. In addition, a dust-proof element (e.g. an air filter) is usually arranged at the airflow outlet of the electronic device in order to obstruct dust from entering the internal portion of the electronic device and/or exhausting to the environment.

In a case that the dust-proof element has been used for a prolonged period, the degree of dust accumulation becomes more serious and thus the airflow induced by the fan fails to pass through the dust-proof element. Under this circumstance, the heat-removing capability of the power supply apparatus is reduced and the performance of the power supply apparatus is deteriorated. For providing unobstructed airflow, the dust-proof element needs to be periodically cleaned or replaced with a new one.

Conventionally, three mechanisms are used for discriminating whether the dust-proof element needs to be replaced. According to a first mechanism, a notifying signal is generated when the dust-proof element has been used for a certain time period. The first mechanism fails to comply with diverse conditions of using different power supply apparatuses. According to a second mechanism, a notifying signal is generated when the pressure of the airflow passing through the dust-proof element is lower than a threshold value. Since pressure of the airflow is very tiny, it is difficult to accurate measure airflow pressure. In other words, the second mechanism usually erroneously generates the notifying signal. According to a third mechanism, a notifying signal is generated when an intensity of a transmissible light or a reflective light received by an optical receiver is below a threshold value. Since the optical receiver is often contaminated by the dust, the optical receiver will erroneously generate the notifying signal. Under this circumstance, an additional dust cleaner is necessary to clean the optical receiver.

There is a need of providing a wind speed detecting circuit capable of detecting the timing for replacing dust-proof element of electronic device so as to obviate the drawbacks encountered from the prior art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wind speed detecting circuit for accurately discriminating whether a dust-proof element of an electronic device needs to be replaced with a new one.

In accordance with an aspect of the present invention, there is provided a wind speed detecting circuit for detecting a wind speed of an airflow passing through a dust-proof element of an electronic device. The wind speed detecting circuit includes a heating unit, a first temperature sensor, a second temperature sensor, a control unit and a driving unit. The first temperature sensor is used for detecting a first temperature of an internal portion of the electronic device, thereby generating a first detecting signal. The second temperature sensor is connected with the heating unit for detecting a second temperature of the heating unit, thereby generating a second detecting signal. The control unit is connected with the first temperature sensor and the second temperature sensor for generating a modulation signal according to the first detecting signal and the second detecting signal. The driving unit is connected with the heating unit and the control unit for generating a driving signal to control operations of the heating unit in response to the modulation signal, so that a temperature difference between the first temperature and the second temperature is maintained constant. A specified relation between the wind speed and the modulation signal facilitates discriminating whether the dust-proof element needs to be replaced.

In accordance with another aspect of the present invention, there is provided an electronic device. The electronic device includes a fan for inducing airflow, a dust-proof element facing to the fan for obstructing dust contained in the airflow, and an electronic wind speed detecting device having a wind speed detecting circuit for detecting the airflow passing through the dust-proof element at a relatively low wind speed ranged from 0 to 6 m/s and discriminating whether the dust-proof element needs to be replaced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic perspective view illustrating an electronic device according to the present invention. As shown inFIG. 1, the electronic device1principally comprises a fan11, a dust-proof element12and a wind speed detecting device13′. The fan11is used to induce airflow for exhausting warm air from the internal portion of the electronic device1. It is preferred that the fan11is operated at a constant rotating speed. An example of the dust-proof element12includes but is not limited to a filter. The dust-proof element12is usually arranged at the airflow outlet of the electronic device1for sheltering the airflow outlet in order to obstruct dust from entering the internal portion of the electronic device1. Due to the dust-proof element12, the electronic device1can be operated in a dust-proof environment. The wind speed detecting device13′ is disposed on the dust-proof element12. The wind speed detecting device13′ has a wind speed detecting circuit13(as shown inFIG. 2) for detecting the wind speed of the airflow passing through the dust-proof element12. According to the wind speed of the airflow passing through the dust-proof element1, the degree of dust accumulation on the dust-proof element12is realized and thus the user can discriminated whether the dust-proof element12needs to be replaced with a new one. In this embodiment, the electronic device1is a power supply apparatus. The present invention is applied to any electronic device having a fan and a dust-proof element. For example, the electronic device1may be an air conditioner, a vacuum cleaner or a projector. The location of the wind speed detecting device13′ is not restricted to the airflow outlet. That is, the wind speed detecting device13′ may be arranged at the location where stable airflow can pass through.

FIG. 2is a schematic circuit block diagram illustrating a wind speed detecting circuit according to an embodiment of the present invention. As shown inFIG. 2, the wind speed detecting circuit13principally comprises a heating unit131, a driving unit132, a first temperature sensor133, a second temperature sensor134and a control unit135. The heating unit131is connected with the driving unit132and the second temperature sensor134.

The heating unit131is an electric heating element for generating thermal energy. According to a driving signal generated from the driving unit132, the temperature of the heating unit131is adjustable.

The first temperature sensor133is connected with the control unit135for detecting the temperature of the internal portion of the electronic device1or the wind temperature of the wind passing through the dust-proof element12. That is, the first temperature sensor133is used for detecting the temperature of the airflow that is induced by the fan11and contacted with the first temperature sensor133. When the internal temperature of the electronic device1or the wind temperature of the wind passing through the dust-proof element12is detected by the first temperature sensor133, the first temperature sensor133generates a first detecting signal to the control unit135. The second temperature sensor134is connected with the heating unit131and the control unit135for detecting the temperature of the heating unit131, thereby generating a second detecting signal to the control unit135.

The control unit135is connected with the first temperature sensor133, the second temperature sensor134and the driving unit132. By comparing the first detecting signal with the second detecting signal, the control unit135generates a modulation signal to the driving unit132. An example of the modulation signal includes but is not limited to a pulse width modulation (PWM) signal. In this embodiment, the modulation signal is a pulse width modulation (PWM) signal. The driving unit132is connected with the heating unit131and the control unit135. In response to the PWM signal transmitted from the control unit135, the driving unit132generates a driving signal to the heating unit131to control operations of the heating unit131. That is, in response to the driving signal, corresponding electric energy is supplied to the heating unit131and thus the heating unit131generates thermal energy.

In this embodiment, under control of the control unit135, the duty cycle of the PWM signal is changed according to the first detecting signal and the second detecting signal. As the duty cycle of the PWM signal is changed, the magnitude of the electric energy supplied form the driving unit132to the heating unit131is adjusted. Consequently, there is a constant temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1.

As the wind speed of the airflow passing through the dust-proof element12is increased, more thermal energy generated from the heating unit131is removed away. In this case, the duty cycle of the PWM signal is increased under control of the control unit135, and thus more electric energy is supplied from the driving unit132to the heating unit131. As such, the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1will be kept constant. On the other hand, as the wind speed of the airflow passing through the dust-proof element12is decreased, less thermal energy generated from the heating unit131is removed away. In this case, the duty cycle of the PWM signal is decreased under control of the control unit135, and thus less electric energy is supplied from the driving unit132to the heating unit131. As such, the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1will be also kept constant. In other words, as the wind speed of the airflow passing through the dust-proof element12is increased or decreased, the duty cycle of the PWM signal is correspondingly increased or decreased.

In an embodiment, the wind speed of the airflow passing through the dust-proof element12and the duty cycle of the PWM signal generated from the control unit135comply with a linear relation. The linear relation can reduce the circuitry complexity of the wind speed detecting circuit13. In some embodiments, the wind speed of the airflow passing through the dust-proof element12and the duty cycle of the PWM signal generated from the control unit135comply with a nonlinear relation. Under this circumstance, a look-up table correlating the wind speed of the airflow passing through the dust-proof element12to the duty cycle of the PWM signal generated from the control unit135needs to be previously established. According to the look-up table, the duty cycle of the PWM signal is adjusted as the wind speed of the airflow is changed.

Hereinafter, the uses of the wind speed of the airflow passing through the dust-proof element to discriminate whether the dust-proof element will be illustrated in more details with reference toFIG. 3.FIG. 3is a schematic plot showing a relation between the wind speed of the airflow passing through the dust-proof element and duty cycle of the PWM signal generated from the control unit. In this embodiment, the wind speed of the airflow passing through the dust-proof element12and the duty cycle of the PWM signal generated from the control unit135comply with a linear relation.

If the electronic device1is initiated and the fan11is in an off status, the wind speed is zero. In this case, the duty cycle of the PWM signal generated from the control unit135is very low (e.g. 178). According to the duty cycle of the PWM signal, little less electric energy is supplied from the driving unit132to the heating unit131. As such, the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1is maintained at a constant value.

If the fan11is operated at a specified rotating speed and only little dust is accumulated on the dust-proof element12, the airflow induced by the fan11can smoothly pass through the dust-proof element12. In this case, the wind speed of the airflow passing through the dust-proof element12is increased (e.g. 6 m/s) and more heat generated from the heating unit131is removed. As such, the temperature of the heating unit131is decreased. For maintaining the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1at the constant value, the duty cycle of the PWM signal generated from the control unit135is increased (e.g. 580). Since the duty cycle of the PWM signal is increased, more electric energy is supplied from the driving unit132to the heating unit131. As such, the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1is maintained at the constant value.

If the fan11is operated at a specified rotating speed but much dust is accumulated on the dust-proof element12, the airflow induced by the fan11fails to smoothly pass through the dust-proof element12. In this case, the wind speed of the airflow passing through the dust-proof element12is decreased (e.g. 3 m/s) and only little heat generated from the heating unit131is removed. Due to the poor heat-removing capability, the temperature of the heating unit131is increased. For maintaining the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1at the constant value, the duty cycle of the PWM signal generated from the control unit135is decreased (e.g. 393). Since the duty cycle of the PWM signal is decreased, less electric energy is supplied from the driving unit132to the heating unit131. As such, the temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1is also maintained at the constant value.

From the above discussion, a smaller duty cycle of the PWM signal generated from the control unit135indicates a lower wind speed of the airflow passing through the dust-proof element12but a larger degree of dust accumulation on the dust-proof element12. Otherwise, a larger duty cycle of the PWM signal generated from the control unit135indicates a higher wind speed of the airflow passing through the dust-proof element12but a smaller degree of dust accumulation on the dust-proof element12. In accordance with a key feature of the present invention, the wind speed of the airflow passing through the dust-proof element12is realized by indirectly detecting the duty cycle of the PWM signal generated from the control unit135. Since the wind speed of the airflow passing through the dust-proof element12is inversely related to the degree of dust accumulation on the dust-proof element12, the user can discriminate whether the dust-proof element12needs to be replaced with a new one according to the duty cycle of the PWM signal.

In an embodiment, the heating unit131includes a resistor that is known in the art. It is preferred that the resistor is a low temperature coefficient resistor. An example of the low temperature coefficient resistor includes but is not limited to a metal oxide film resistor. In an embodiment, the heating unit131includes a tungsten wire or an alloy, which is more thermal-resistant and costly than the resistor. Moreover, the first temperature sensor133and the second temperature sensor134are temperature-sensing integrated circuits.

In an embodiment, the constant temperature difference between the temperature of the heating unit131and the temperature of the internal portion of the electronic device1is 40° C. The constant temperature difference is varied according to the practical requirements.

FIG. 4is a schematic circuit block diagram illustrating a first variant example of the wind speed detecting circuit shown inFIG. 2. As shown inFIG. 4, the control unit135includes a difference amplifying circuit135aand a micro controller135b. The input terminals of the difference amplifying circuit135aare respectively connected to the first temperature sensor133and the second temperature sensor134. The output terminal of the difference amplifying circuit135ais connected to the input terminal of the micro controller135b. By comparing the first detecting signal with the second detecting signal, the difference amplifying circuit135agenerates a difference amplifying signal to the micro controller135baccording to the comparing result. The input terminal of the micro controller135bis connected to the output terminal of the difference amplifying circuit135a. The output terminal of the micro controller135bis connected to the driving unit132. According to the difference amplifying signal transmitted from the difference amplifying circuit135a, the micro controller135bgenerates a pulse width modulation with an adjustable duty cycle.

FIG. 5is a schematic circuit block diagram illustrating a second variant example of the wind speed detecting circuit shown inFIG. 2. In this embodiment, the wind speed detecting circuit13further includes a humidity detecting unit136. The humidity detecting unit136is connected with the control unit135for detecting the humidity in the internal portion of the electronic device1, thereby generating a first compensating signal to the control unit135. Under control of the control unit135, the duty cycle of the PWM signal is changed according to the first compensating signal.

FIG. 6is a schematic circuit block diagram illustrating a third variant example of the wind speed detecting circuit shown inFIG. 2. In this embodiment, the wind speed detecting circuit13further includes a rotating speed detecting unit137. The rotating speed detecting unit137is connected with the control unit135for detecting the rotating speed of the fan11according to a current, a voltage or a cycle control signal generated when the fan11is rotated, thereby generating a second compensating signal to the control unit135. Under control of the control unit135, the duty cycle of the PWM signal is changed according to the second compensating signal.

FIG. 7is a schematic circuit block diagram illustrating a fourth variant example of the wind speed detecting circuit shown inFIG. 2. In this embodiment, the wind speed detecting circuit13further includes a warning unit138. The warning unit138is connected with the control unit135. If the duty cycle of the PWM signal generated from the control unit135is below a first threshold value, the warning unit138will issue a warning signal to notify the user that the dust-proof element12needs to be replaced with a new one.

As known, the wind speed of the airflow passing through the dust-proof element is usually unstable due to a drift of the airflow. The unstable wind speed of the airflow causes unsteady PWM signal and thus the warning signal is erroneously generated from the warning unit138. For preventing from erroneously generating the warning signal, if the duty cycle of the PWM signal generated from the control unit135is below the first threshold value, the warning unit138will not instantly issue the warning signal. On the other hand, after the duty cycle of the PWM signal is below the first threshold value and the duty cycle of the PWM signal has been continuously below a second threshold value for a certain time interval, the warning unit138will issue a warning signal to notify the user that the dust-proof element12needs to be replaced with a new one. Even if the wind speed of the airflow passing through the dust-proof element suddenly drops because the airflow outlet is temporarily obstructed by an foreign article for example, the warning unit138will not instantly issue the warning signal. As a consequence, the possibility of erroneously generating the warning signal is reduced.

From the above description, the electronic wind speed detecting device is used for detecting the airflow passing through a dust-proof element of an electronic device at a relatively low wind speed ranged from 0 to 6 m/s, which can't be detected by a mechanical wind speed detecting device. The wind speed of the airflow passing through the dust-proof element is realized by indirectly detecting the duty cycle of the PWM signal generated from the control unit. Since the wind speed of the airflow passing through the dust-proof element is inversely related to the degree of dust accumulation on the dust-proof element, the user can discriminate whether the dust-proof element needs to be replaced with a new one according to the duty cycle of the PWM signal. In comparison with the prior art, the wind speed detecting device can determine the timing of replacing the dust-proof element in a more accurate and cost-effective manner.