Abstract:
The present invention relates to a safety output device for use in a power converter that includes a converter main body adapted for outputting a direct-current electric power at a predetermined voltage. The safety output device is adapted for being associated with an electricity consuming device that is powered by the power converter and comprises a wire set adapted for being electrically connected to the converter main body, a sensing controller for measuring a voltage difference in the wire set, and a switch adapted for being actuated by the sensing controller to permit electric conduction from the converter main body to the electricity consuming device when the voltage difference is detected to be substantially equal to the predetermined voltage.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a safety output device, and more particularly, to a safety output device for use in a power converter. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    The electronic circuits present in many of the electronic appliances pertain to the digital circuits that are designed to consume direct-current low voltage electricity. However, the electric power supplied by a power plant is normally in the form of alternating current with a much higher voltage. As such, voltage conversion must be carried out before the electric power is supplied to the electronic appliances from a wall socket. As portability becomes a growing trend in electronic products, it is no longer practicable to build a converter in the miniaturized portable electronics. It makes a wide variety of converters become indispensable in modern life and almost all types of the major electronic appliances such as portable audio/video players, mobile phones, MP3 and laptop computers are accompanied with converters of their own. 
         [0003]    Due to commercial consideration, converters provided by different manufacturers have their own individual specifications and may vary in output voltage, adapter size and so on, whereas the standard household voltage may also vary from country to country. Although efforts have been made by manufacturers to make converters tolerable to the ordinary incoming voltage ranging from 110 volts to 220 volts and capable of converting the incoming voltage into a particular outgoing voltage, the magnitude of the outgoing voltages and the size of adapters remain to be standardized. 
         [0004]    Because of the diversity of electronic appliances, each family or even each user must possess a large number of converters of various specifications, which would turn out to be burdensome once the electronic products to which the converters are connected are out of order. In response to consumer demands, converters that provide variable output voltages and have changeable adapters are now available in the market, which would significantly reduce the number of converters that one should have at home and further ease the inconvenience of carrying different types of converters during leisure or business travel. 
         [0005]    However, as shown in  FIG. 1 , a conventional power converter  12  is configured to adjust the output voltage by providing a slide switch  14  that is associated with the output wire and changing the resistance of the resistor mounted in the slide switch  14  to thereby operatively change the voltage level of the electric power that is to be output via the output terminal  13 . Unfortunately, the actuator  15  of the switch  14  in this configuration will get loose gradually after a long time use and, therefore, the output voltage will become unstable due to the occurrence of miscontact. Accidental miscontact that occurs during the operation of the switch  14  can be a serious risk for personal safety and performance of electronic products. 
         [0006]    On the other hand, in considering the cost effectiveness and portability, manufacturers of portable electronic products normally build safety circuits in the converters that are exclusively useful for their own products, while asking consumers not to use converters of other types. Generally, the laptop computers available in the market are manufactured to tolerate a 5% plus/minus variation in the ideal voltage level. In other words, damage would occur to the intrinsic circuits of the laptop computers if the incoming voltage goes beyond the predicted range. In the case where the original parts are either missing or not on hand, a user may have to acquire a non-original converter from the market, which may not have a circuit design for monitoring the output voltage and enabling an alarm in response to detection of the occurrence of an output fault. Even if the non-original converter is equipped with a monitoring device in the voltage-transforming circuit, the user may still have to face a risk of abrupt output voltage fluctuation caused by a structural defect between the monitoring device and the output port due to inferior quality control. 
         [0007]    Therefore, there exists a need for a miniature safety output device that is cost-effective as compared to the portable electronic appliances to which it may be connected and is capable of ensuring that the electric output from any type of power converters is at a level demanded by the specifications of the portable electronic appliances to which it may be connected. The present invention provides the best solution in response to the need. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, an object of the present invention is to provide a safety output device for use in a power converter, which is extremely safe as it will decline to transmit electric power at an undesired voltage level. 
         [0009]    Another object of the invention is to provide a safety output device for use in a power converter, which has a simple and compact structure that will not adversely affect the portability of the electronic appliances to which it is connected. 
         [0010]    It is still another object of the invention to provide a safety output device for use in a power converter, which has the advantage of low manufacture cost. 
         [0011]    It is still another object of the invention to provide a safety output device for use in a power converter, which is capable of continuously monitoring the voltage/current output from the power converter and cutting off the power supply to an electronic appliance in response to detection of the occurrence of an output fault, thereby ensuring that damage will not occur to the electronic device as a result of the output fault. 
         [0012]    It is still another object of the invention to provide a power converter having a safety output device mounted therein, which is extremely safe as it will prevent damage to the electronic appliances to which it is connected. 
         [0013]    The present invention therefore provides a safety output device for use in a power converter, where said power converter has a converter main body adapted for outputting a direct current electric power at a predetermined voltage and where said safety output device is adapted for being electrically connected to an electricity consuming device that is powered by the power converter, the safety output device comprising: a wire set adapted for being electrically connected to the converter main body, including a high level wire and a low level wire that are configured to receive the electric power from the converter main body; a sensing controller for measuring a voltage difference between the high level wire and the low level wire; and a switch adapted for being actuated by the sensing controller to permit electric conduction from the converter main body to the electricity consuming device when the voltage difference between the high level wire and the low level wire is substantially equal to the predetermined direct current voltage. 
         [0014]    In the context of the invention, the term “electrically connected to” is defined as a condition where two or more components are electrically communicated to enable the flow of electrical current, either by way of direct coupling or through one or more intermediate components such as an adaptor, an electrical wire or the like. 
         [0015]    The invention allows users to readily choose an appropriate safety output device that is well compatible with the electronic appliance to which it is to be connected, by reference to the voltage and current specifications of the electronic appliance provided by the manufacturer, and connect the same to a charging port of the electronic appliance. If the incoming voltage from the power converter is at an undesired level, the safety output device will decline to transmit electric power to the electronic appliance, so that a good quality of power supply can be obtained. In particular, the safety output device according to the invention may be configured to continuously monitoring the quality of power supply, so as to ensure the safety of using electrical equipments. The safety output device according to the invention further presents advantages of simple circuit design, low manufacture cost and compact size, so that the portability and performance of electronic devices are not adversely affected by the weight and size of the safety output device. The invention enables users to acquire appropriate safety output devices for the precious electronic appliances of their own and utilize the same in conjunction with any types of converters available in the market without worrying about any damage that may otherwise occur to their electronic appliances. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other objects, features and effects of the invention will become apparent with reference to the following description of the preferred embodiments taken in conjunction with the accompanying drawings, in which: 
           [0017]      FIG. 1  is a perspective view of a conventional power converter; 
           [0018]      FIG. 2  is a perspective view of a power converter according to the first preferred embodiment of the invention, illustrating the technical relationship among a safety output device, a converter main body and an electronic appliance; 
           [0019]      FIG. 3  is a circuit diagram for the converter main body shown in  FIG. 2 ; 
           [0020]      FIG. 4  is a circuit diagram for the safety output device shown in  FIG. 2 ; and 
           [0021]      FIG. 5  is a bock diagram illustrating a power converter according to the second preferred embodiment of the invention. 
           [0022]      FIG. 6  is a schematic diagram outlining the structure of the second preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 2  is a schematic diagram of a power converter, as well as a safety output device provided therein, according to the first preferred embodiment of the invention. In this embodiment, the power converter may by way of example be connected to a wall socket  8  and therefore receives an incoming voltage of 110 volts. The electronic appliance that is to be powered by the power converter is hereafter referred to as an electricity consuming device. For the sake of elucidation, the electricity consuming device according to this embodiment may by way of example be a mobile phone  9  that is designed to receive a charging voltage of 5 volts DC. Of course, it would be appreciated by those skilled in the art that the incoming voltage mentioned above can be either 220 volts AC or 12 volts DC supplied by an automobile power supply, and that the electricity consuming device may pertain to any type of electronic appliances. 
         [0024]    As an abnormally large value of the charging voltage may cause the lithium battery used in the mobile phone  9  to overheat or even catch fire, the voltage given to the mobile phone  9  should not exceed the required level. In this embodiment, the safety output device is configured in the form of an adapter that is compatible with and pluggable into a charging port of the mobile phone  9 . 
         [0025]    The power converter according to this embodiment comprises a safety output device  2  and a converter main body  3 . The converter main body  3  according to this embodiment includes a plug  30  that serves as an input port adapted for being electrically connected to the wall socket  8 , an output wire  34  that serves as an output port, and a housing  32  coupled between the plug  30  and the output wire  34 , wherein the housing  32  accommodates a voltage-transforming unit  36  and a voltage-selecting unit  38 , as shown in  FIG. 3 . The voltage-transforming unit  36  is provided with a voltage-transforming circuitry in which, for example, a feedback control amplifier  360  is provided to allow feeding of a reference voltage Vref to a non-inverting input terminal  362 , and an inverting input terminal  364  is connected to an output terminal  366  to thereby follow the reference voltage Vref. The inverting input terminal  364  can be selectively connected to one of a plurality of circuits arranged within a switch  380  that serves as the voltage-selecting unit  38 . Each circuit is provided with a resistor  382  with the respective resistors  382  having different resistances from one another. 
         [0026]    When a resistor  382  of a certain resistance is connected to ground by the switch, the resistance ratio of the two resistors  382  and  384  will determine the voltage at the output terminal Vout, as the voltage at the inverting input terminal  364  is correlated with the reference voltage Vref at the non- inverting input terminal  362 . In the case where the resistor  382  connected to the amplifier is switched from one to the other, the resistance ratio of resistors  382  and  384  is changed and, as a result, the output voltage Vout is changed accordingly. Of course, it would be appreciated by those skilled in the art that the power converter according to the invention is not limited to those providing variable output voltages but also includes those which convert an input voltage into a fixed output voltage. For the preferred circuitries for providing variable output voltages, please refer to R.O.C. Patent Application No. 97106821 assigned to the applicant. 
         [0027]    As shown in  FIG. 4 , the safety output device according to the invention has a wire set including a high level wire  20  and a low level wire  22  that are electrically connected to separate output terminals of the converter main body. In this embodiment, the potential of the low level wire  22  is defined to be zero, so that the low level wire is connected to ground as shown in the Figure. However, it would be appreciated by those skilled in the art that such an aspect should be regarded as illustrative in nature and not as restrictive. In this embodiment, the low level wire  22  is provided with a switch, which may by way of example be a metal-oxide-semiconductor field-effect transistor (MOSFET)  26  having a gate electrode connected to a voltage difference sensing controller  24  that acts as a control unit for controlling the electrical conduction between the drain and source of MOSFET  26 . 
         [0028]    In this embodiment, the voltage difference sensing controller  24  is provided with two comparators  240  and  242 . When a reference voltage Vref is fed to the non-inverting input terminal  246  of the comparator  240 , the potential at the inverting input terminal  244 , namely, 
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         [0029]    Meanwhile, the comparator  242  utilizes the potential at the inverting input terminal, namely, 
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         [0000]    the output terminal of the comparator  242  will output high level signals to confirm that the potential of the high level wire  20  exceeds the predetermined lower limit 
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         [0000]    On the contrary, if the potential of the high level wire  20  is too low, the comparator  242  will output low level signals, whereby a downstream AND gate maintains the disconnection of the source and drain of MOSFET  26  to protect the electricity consuming device from under-voltage damage. 
         [0030]    The invention further provides a second preferred embodiment as illustrated in  FIG. 5 , which differs from the first preferred embodiment in that the sensing controller further comprises a current-sensing controller  25 ′ connected in series with the wire set to thereby detect the current level of the wire set. In addition to monitoring the voltage difference between the two wires in the wire set by virtue of a voltage difference sensing controller  24 ′ to thereby prevent damage to the electricity consuming device caused by a non-ideal voltage, the safety output device according to the invention is preferably configured to turn off the switch  26 ′ immediately using the current-sensing controller mentioned above, in response to the event that the current level of the wire set exceeds a predetermined level due to the occurrence of an internal short circuit fault in the electricity consuming device, whereby damage to the electricity consuming device is further reduced. 
         [0031]    Of course, it would be appreciated by those skilled in the art that the safety output device according to the invention is not limited to those formed of a single-part configuration and adapted for directly coupling to an electronic appliance. In response to the fact that the charging ports of portable electronics, including laptop computers and personal digital assistants, are constructed by different manufacturers with widely diverse dimensions, the safety output device  2 ′ according to the second preferred embodiment of the invention, as shown in  FIG. 6 , is provided with an adapter  3 ′ that is configured to match with the charging port of the electronic appliance to which it is to be coupled. Only the adapter  3 ′ has to be manufactured with various specifications particularly suited for coupling to the charging ports of the electronic appliances. The safety output device  2 ′ itself is of a universal specification and, as a result, the manufacture cost thereof is significantly reduced. 
         [0032]    The safety output device  2 ′ according to this embodiment may be further provided with an LED  27 ′ which is electrically connected to the voltage difference sensing controller  24 ′ in such a manner that when the voltage difference detected by the voltage difference sensing controller  24 ′ deviates from a predetermined value beyond a predetermined deviation, the LED  27 ′ flashes to indicate the occurrence of an output fault while the downstream switch  26 ′ is kept in the OFF state. 
         [0033]    To improve the quality of power supply to the greatest extent possible, the safety output device according to the invention is optionally provided with a voltage stabilizing circuit  28 ′ to thereby provide stable electricity to the downstream electronic appliances. Of course, all of the electronic circuits mentioned above can be incorporated in a single integrated circuit according to the modern technology, instead of being fabricated as discrete components. 
         [0034]    Accordingly, the invention enables a user to protect any electronic appliance from over-voltage damage by acquiring a suitable safety output device according to the invention and mounting the same to a charging port of the appliance. The safety output device according to the invention does not only ensure that the voltage received by the appliance is kept in an ideal range, but also prevents over-current damage by selectively cutting out the power supply. The safety output device according to the invention may further be provided with a voltage stabilizing circuit to improve the stability of the powder supply to the appliance. In particular, the safety output device according to the invention presents advantages of low manufacture cost and compact size, so that the portability and performance of the appliance are not adversely affected by the weight and size of the safety output device. The safety output device according to the invention enables a user to utilize any types of converters available in the market without worrying about any damage that may occur to the appliance. 
         [0035]    While the invention has been described with reference to the preferred embodiments above, it should be recognized that the preferred embodiments are given for the purpose of illustration only and are not intended to limit the scope of the present invention and that various modifications and changes, which will be apparent to those skilled in the relevant art, may be made without departing from the spirit and scope of the invention.