Abstract:
A power-protection apparatus is provided. The apparatus includes an over-voltage protection unit for generating an over-voltage detection signal when the power supply of the load is over the upper limit of a predetermined voltage range; an under-voltage protection unit for generating an under-voltage detection signal when the power supply of the load is under the lower limit of the predetermined voltage range; a working-state detection unit for receiving a control signal and generating a working-state detection signal when the level time-change rate of the control signal is over a time-change rate threshold; and a power-control unit coupled to the over-voltage protection unit, the working-state detection unit and the under-voltage protection unit for controlling the on and off of the power supply according to the over-voltage detection signal, the under-voltage detection signal or the working-state detection signal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 102,104,324, filed in Taiwan, Republic of China on Feb. 5, 2013, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to power-protection apparatuses of motors, and in particular to power-protection apparatuses that save energy. 
     Description of the Related Art 
     The prior art provides various circuit-protection methods to prevent the expensive and delicate motors from damage. 
     The prior art provides three methods for over-voltage protection: method I—improving circuit-element specifications; method II—protecting circuits by using a transient voltage suppressor (TVS); and method III—protecting circuits by using an operational amplifier (OP). 
     For method I, improving circuit-element specifications means raising the cost, and less choice for the circuit elements. Therefore, method I applies only to simple circuits and is rarely employed. For method II, although using TVS is the mainstream approach, this method is only suitable for eliminating transient high voltage or surges with low power, such as ESD, and circuits may break when the high voltage is sustained. For method III, the OP not only has a higher cost and limited input voltage, but also has complicated circuit design and a slower circuit-reaction speed. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a power-protection apparatus for protecting a load. The apparatus comprises an over-voltage protection unit for generating an over-voltage detection signal when the power supply of the load is over the upper limit of a predetermined voltage range; an under-voltage protection unit for generating an under-voltage detection signal when the power supply of the load is under the lower limit of the predetermined voltage range; a working-state detection unit for receiving a control signal, and generating a working-state detection signal when the pulse width of the control signal is over a predetermined pulse width; and a power-control unit coupled to the over-voltage protection unit, the working-state detection unit and the under-voltage protection unit for controlling the on and off of the power supply according to the over-voltage detection signal, the under-voltage detection signal and the working-state detection signal. 
     The present invention provides a power-protection method for protecting a load. The method comprises: generating an over-voltage detection signal when the power supply of the load is over the upper limit of a predetermined voltage range; generating an under-voltage detection signal when the power supply of the load is under the lower limit of the predetermined voltage range; receiving a control signal, and generating a working-state detection signal when the pulse width of the control signal is over a predetermined width; and turning off the power supply when receiving an over-voltage detection signal, an under-voltage detection signal, or a working-state detection signal. A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a block diagram of the power-protection apparatus according to an embodiment of the present invention; 
         FIG. 2A  is a schematic diagram of the over-voltage protection unit according to an embodiment of the present invention; 
         FIG. 2B  shows the signals in the over-voltage protection unit in  FIG. 2A ; 
         FIG. 3A  is a schematic diagram of the under-voltage protection unit according to an embodiment of the present invention; 
         FIG. 3B  shows the signals in the under-voltage protection unit in  FIG. 3A ; 
         FIG. 4A  is a schematic diagram of the working-state detection Unit according to an embodiment of the present invention; 
         FIG. 4B  shows the signals in the working-state detection unit in  FIG. 3A ; 
         FIG. 5  is a flow chart of the power-protection method according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     The power-protection apparatus of the present invention is used to protect the fan motor.  FIG. 1  is a power-protection apparatus according to an embodiment of the present invention. In this embodiment, the motor  150  obtains a power supply P from a power source via a power management unit  160 , and the rotation speed of the motor  150  is controlled by a rotation-speed control signal S C , which is received from the outside via a micro-control unit  170 . 
     The present invention provides a specific power-protection apparatus  100 , where the power-protection apparatus  100  is coupled to the motor  150 . The power-protection apparatus  100  of the present invention comprises an over-voltage protection unit  110 , an under-voltage protection unit  120 , a working-state detection unit  130  and a power-control unit  140 . The components of the present invention will be further described in detail in accordance with  FIGS. 2A, 2B, 3A, 3B, 4A, and 4B  in the following paragraphs. 
       FIG. 2A  is a schematic diagram of the over-voltage protection unit  110  according to an embodiment of the present invention.  FIG. 2B  shows the signals in the over-voltage protection unit  110  in  FIG. 2A . The over-voltage protection unit  110  of the present invention can produce an over-voltage detection signal when the power supply P of the motor is over the upper limit V+ of a predetermined voltage range. The over-voltage detection signal can be used by the power-control unit  140 , which will be described later. As shown in  FIG. 2A , the over-voltage protection unit  110  of the present invention comprises a voltage subtractor  112 . The voltage subtractor  112  can subtract the part of the power supply P which is over the upper limit V+ of the predetermined voltage range for directly producing an over-voltage detection signal. As shown in  FIG. 2B , when the power supply P has a part that exceeds the upper limit V+ of the predetermined voltage range, the voltage subtractor  112  directly subtracts that part and produces an “over-voltage detection signal SH” (high level). In other words, when the power supply P is not over the upper limit V+ of the predetermined voltage range, the voltage subtractor  112  will not affect the original level of the power supply P and produce any over-voltage detection signal. In some embodiments, the voltage subtractor  112  comprises at least one Zener diode. With the mentioned structure, the over-voltage protection unit  110  of the present invention has no TSV or OP of the prior art that additionally consumes power, thereby saving energy. As shown in  FIG. 2A , the over-voltage protection unit  110  of the present invention can further comprise a regulator circuit  114 . The regulator circuit  114  can regulate the signals provided by the voltage subtractor  112  so as to make the signals exhibit an ideal waveform that can be accepted by the power-control unit  140  (for example, the square waveform of the over-voltage detection signal SH′, as shown in  FIG. 2B ), thereby avoiding malfunctions. 
       FIG. 3A  is a schematic diagram of the under-voltage protection unit  120  according to an embodiment of the present invention.  FIG. 3B  shows the signals in the under-voltage protection unit  120  in  FIG. 3A . In contrast to the over-voltage protection unit  110 , the under-voltage protection unit  120  of the present invention can produce an under-voltage detection signal when the power supply P of the motor is under the lower limit V− of the predetermined voltage range. The under-voltage detection signal can be used by the power-control unit  140 , which will be described later. In an embodiment, as shown in  FIG. 3A , the under-voltage protection unit  120  of the present invention comprises a voltage subtractor  122 . The voltage subtractor  122  can subtract the part of the power supply P which is under the lower limit V− of the predetermined voltage range to directly produce the under-voltage detection signal. As shown in  FIG. 3B , when the power supply P has apart that is lower than the lower limit V− of the predetermined voltage range, the voltage subtractor  122  filters out that part and produces an under-voltage detection signal S L  (low level). In other words, when the power supply P is not under the lower limit V− of the predetermined voltage range, the voltage subtractor  122  will not affect the original level of the power supply P and produce any under-voltage detection signal. In some embodiments, the voltage subtractor  122  comprises at least one Zener diode. With the aforementioned structure, the under-voltage protection unit  120  of the present invention has no TSV or OP of the prior art which consume additional power, and thus it saves energy. As shown in  FIG. 3A , the under-voltage protection unit  120  of the present invention can further comprise a regulator circuit  124 . The regulator circuit  124  can regulate the signals provided by the voltage subtractor  122  so as to make the signals exhibit waveforms that can be accepted by the power-control unit  140  (for example, the square waveform of the under-voltage detection signal S L′  as shown in  FIG. 3A ) and avoid malfunctions. 
       FIG. 4A  is a schematic diagram of the working-state detection unit  130  according to an embodiment of the present invention.  FIG. 4B  shows the signals in the working-state detection unit  130  in  FIG. 4A . The working-state detection unit  130  of the present invention is configured to receive the rotation-speed control signal S C . As shown in  FIG. 4A , the working-state detection unit  130  produces a working-state detection signal S S  (with expected signal level) when the pulse width of the rotation-speed control signal S C  exceeds a predetermined pulse width D. The working-state detection signal S S  can be used by the power-control unit  130 , which will be described later. As shown in  FIG. 4B , the working-state detection unit  130  of the present invention further comprises a signal converter  132 . In an embodiment, the signal converter  132  comprises a charging/discharging circuit (for example, an RC circuit) that can control the charging/discharging characteristic of the circuits. As shown in  FIG. 4B , the signal converter  132  can convert the rotation-speed control signal S C  which has a varied rotation speed in a period into a working-state detection signal S S  (low level) through charging and discharging characteristic of the circuits. As shown in  FIG. 4A , the working-state detection unit  130  of the present invention further comprises a regulator circuit  134 . The regulator circuit  134  regulates the signals provided by the signal converter  132  so as to make the signals exhibit waveforms that can be accepted by the power-control unit  140  (for example, the square waveform of the working-state detection signal S S′  as shown in  FIG. 4B ) to avoid malfunctions. 
     The power-control unit  140  of the present invention is coupled to the over-voltage protection unit  110 , the under-voltage protection unit  120  and the working-state detection unit  130  to control the on and off of the power supply P according to the over-voltage detection signal S H  (or S H′ ), the under-voltage detection signal S L  (or S L′ ) and working-state detection signal S S  (or S S′ ). Specifically, the power-control unit  140  comprises logic elements (such as AND, and OR gates), and can turn off the power supply P of the motor  150  when receiving an over-voltage detection signal S H  (or S H ′), an under-voltage detection signal S L  (or S L′ ), or a working-state detection signal S S  (or S S′ ). In other words, when none of the over-voltage detection signal S H  (or S H′ ), the under-voltage detection signal S L  (or S L′ ), or the working-state detection signal S S  (or S S′ ) is detected by the power-control unit  140 , it means that the power supply P and the rotation-speed control signal S C  are in a normal condition, and the power supply P can safely drive the motor  150 . The present invention thus provides multiple protections for the motor  150 . In some embodiments, as shown in  FIG. 1 , the power-control unit  140  controls the motor  150  via the power management unit  160  and the micro-control unit  170 . However, in other embodiments, the present on should not be limited thereto. 
     In order to save energy, the working-state detection unit  130  and the under-voltage protection unit  120  in a preferred embodiment of the present invention are both coupled between the over-voltage protection unit  110  and the power-control unit  140  so that they can immediately stop operation once receiving the over-voltage detection signal S H . 
     According to the power-protection apparatus described above, the present invention also provides a power-protection method.  FIG. 5  is a flow chart of the power-protection method according to an embodiment of the present invention. The power-protection method is used to protect a motor. The method comprises the steps of producing an over-voltage detection signal when the power supply of the motor is over the upper limit of a predetermined voltage range (step S 502 ); producing an under-voltage detection signal when the power supply of the motor is under the lower limit of the predetermined voltage range (step S 504 ); receiving a rotation-speed control signal, and producing a working-state detection signal when the pulse width of the rotation-speed control signal is over a predetermined pulse width (step S 506 ); and turning off the power supply when receiving the over-voltage detection signal, the under-voltage detection signal, or the working-state detection signal (step S 508 ). Since those skilled in the art can understand the power-protection method of the present invention by referring to the power-protection apparatus described above, the detail of the power-protection method will not be discussed further. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.