Abstract:
A portable lighting device with an energy-saving control circuit is disclosed. The energy-saving control circuit includes an illumination control switch electrically connected in series with a lamp unit; an illumination-setting unit having a plurality of illumination-setting keys for setting a plurality of illumination levels for the lamp unit and generating an illumination control signal corresponding to one of the illumination levels; and a control unit for receiving said illumination control signal from the illumination-setting unit, and outputting an adjustable pulse-width modulation signal to control the illumination control switch, thereby adjusting the illumination of the lamp unit in accordance with the illumination level set by the illumination-setting unit.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a portable lighting device, and more particularly to a lighting device with an energy-saving control circuit.  
           [0003]    2. Description of the Prior Art  
           [0004]    Generally, a portable lighting device, such as a flashlight, includes only a power switch to control the on or off of a bulb of the lighting device, and the illumination of the bulb thereof is not adjustable. Such portable lighting device has very high bulb illumination when its battery is new, and will have weak bulb illumination as soon as the battery is low. A new battery powers the portable lighting device for about 30 minutes on average and needs replacement frequently that inevitably brings inconvenience to a user.  
           [0005]    There are different means to solve the problem of power supply to the portable lighting device, such as providing a charging circuit in the portable lighting device, using a rechargeable battery for the portable lighting device, etc., so that the portable lighting device may be conveniently charged when it is not in use. However, these means do not solve the problem of high power consumption by the portable lighting device, and do not enable a user to adjust the illuminative level of the portable lighting device according to actual need and environmental requirements.  
           [0006]    It is therefore tried by the inventor to develop a portable lighting device, of which an electronic switch is switched on and off through pulse width modulation, so that the bulb illumination of the lighting device is adjustable by changing the pulse width ratio to achieve the purpose of reducing electric energy consumed by the portable lighting device.  
         SUMMARY OF THE INVENTION  
         [0007]    A primary object of the present invention is to provide a portable energy-saving lighting device, in which an electronic switch is switched on and off through pulse width modulation, so that the bulb illumination of the lighting device is adjustable by changing the pulse width ratio to achieve the purpose of reducing electric energy consumed by the portable lighting device.  
           [0008]    Another object of the present invention is to provide a portable energy-saving lighting device that may serve as a charging circuit to charge a rechargeable battery in the lighting device with a commercial power or an automobile power supply, and automatically stops charging when the battery is fully charged.  
           [0009]    A further object of the present invention is to provide a portable energy-saving lighting device that may serve as an emergency light at a power failure. The portable lighting device functions like a charging circuit when the supply of commercial power is in a normal condition, and automatically switches its power supply to the battery thereof when a power failure occurs.  
           [0010]    A still further object of the present invention is to provide a portable energy-saving lighting device that may serve as an emergent help light in case of a disaster or accident by actuating an emergent help light enabling switch thereof to send out Morse code signal or flash light signal.  
           [0011]    A still further object of the present invention is to provide a portable energy-saving lighting device that may serve as a dim light at home to provide adjustable illumination. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein  
         [0013]    [0013]FIG. 1 is a front perspective view of a portable energy-saving lighting device according to a first embodiment of the of the present invention in the form of a flashlight;  
         [0014]    [0014]FIG. 2 shows a flashlight similar to that of FIG. 1 but having differently structured illumination-setting keys;  
         [0015]    [0015]FIG. 3 is a front perspective view of a portable energy-saving lighting device according to a second embodiment of the of the present invention in the form of an emergency light;  
         [0016]    [0016]FIG. 4 is a control circuit diagram for the present invention; and  
         [0017]    [0017]FIG. 5 illustrates different pulse-width modulation signals for controlling the bulb illumination of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    Please refer to FIG. 1 that is a perspective view of a portable energy-saving lighting device  10  according to a first embodiment of the present invention in the form of a flashlight. As shown, the flashlight  10  mainly includes a lamp unit  11 , a power switch  12 , a plurality of batteries  13 , a battery compartment cap  14 , and a plurality of indicating lights  15 .  
         [0019]    The flashlight  10  is further provided at a suitable position with a plurality of illumination-setting keys  16 , with which a user may conveniently control an illuminative level of the lamp unit  11 . In the illustrated embodiment, there are five illumination-setting keys  16  separately representing five different illuminative levels, for example, 20%, 40%, 60%, 80%, and 100%. The user may depress one of these illumination-setting keys  16  to set the lamp unit  11  to a desired illuminative level by changing the pulse width of an output signal to the light  11 . When the user is in an environment that does not need high illumination, or when the user wants to save electric energy, he or she may simply depress one of the illumination-setting keys  16  representing a lower illuminative level to reduce the illumination of the lamp unit  11 .  
         [0020]    In the flashlight  10  according to the first embodiment of the present invention, the illumination-setting keys  16  may also be limited to only two keys, namely, an illumination-up key and an illumination-down key, as shown in FIG. 2. In this case, the illumination of the lamp unit  11  is digitally adjusted. The user needs only to depress the illumination-up key and the illumination-down key to increase and reduce, respectively, the illuminative level of the lamp unit  11 . For example, the present invention may be so designed that each time the up or the down key is depressed, a pulse width of the flashlight is increased or decreased, respectively, by 10%. Of course, it is also possible to control changes in pulse width through a known variable resistor, in order to adjust the illumination of the lamp unit  11 .  
         [0021]    Moreover, the flashlight  10  according to the first embodiment of the present invention is also provided with a plurality of function keys  17  for users to perform other functions provided with the present invention. These functions may include, for example, a power-failure emergency light, an emergent help light, a dim light, etc.  
         [0022]    [0022]FIG. 3 is a perspective view of a second embodiment of the portable energy-saving lighting device  10  of the present invention in the form of an emergency light. The emergency light  10  mainly includes at least one lamp unit  21 , a power switch  22 , a plurality of indicating lights  23 , a plurality of illumination-setting keys  24 , and a plurality of function keys  25 .  
         [0023]    Please refer to FIG. 4 that is a control circuit diagram for the portable energy-saving lighting device of the present invention. The control circuit includes a control unit  30  for controlling various functions provided with the present invention and the illuminative level of the lamp unit thereof; a power converting and charging circuit  31  for converting an alternating power source ACV into a direct output voltage Vout, so that a rechargeable battery  32  of the present invention is charged with the output voltage Vout in normal times and can be used in an emergency, such as a power failure; at least one bulb  33  for emitting light; and a bulb illumination control switch  34  for turning on or off the bulb  33 , as well as controlling the illumination of the bulb  33 .  
         [0024]    In the present invention, the illumination of the bulb  33  is controlled through pulse width modulation. Please refer to FIG. 5 that shows different pulse-width modulation signals for controlling the bulb illumination in the present invention. As mentioned above, the portable energy-saving lighting device  10  of the present invention uses the control unit  30  to control the illumination of the bulb  33  and to select other functions available from the present invention.  
         [0025]    An illumination-setting unit  36  includes a plurality of setting keys for the user to set a desired illuminative level for the bulb  33 . When the user depresses a key on the illumination-setting unit  36  (see FIG. 4) to set a desired illuminative level for the bulb  33 , a setting signal is sent to and received by the control unit  30 . On receipt of the setting signal, the control unit  30  sends out an illumination control signal S 1  to the bulb illumination control switch  34  for the same to control the illumination of the bulb  33 .  
         [0026]    Each key on the illumination-setting unit  36  may be preset to a preset illuminative level, such as 50% or other percentage. The bulb illumination is controlled with the control unit  30  through pulse width modulation. More specifically, the control unit  30  turns the bulb illumination control switch  34  on or off at a high frequency. In this way, electric energy is saved while human eyes would not perceive the on and off of the bulb  33  at high frequency.  
         [0027]    For example, when an illumination-setting key  36  representing an illuminative level of 50% is depressed, the control unit  30  will output a high-frequency pulse signal to the bulb illumination control switch  34 , so that the latter is on for an average of 50% of the time period during which the portable energy-saving lighting device is switched on, and disabled (off) during the rest 50% of time. Or, when an illumination-setting key  36  representing an illuminative level of 100% is depressed, the bulb illumination control switch  34  is enabled all the time. Or, when an illumination-setting key  36  representing an illuminative level of 10% is depressed, the bulb illumination control switch  34  is enabled for an average of 10% of the time period during which the portable energy-saving lighting device is switched on, and disabled during the rest 90% of time. However, since the bulb illumination control switch  34  is alternately on and off at high frequency, and due to the after-vision of human eyes, the user would not perceive a flicker bulb  33  while an object of saving electric energy has been achieved.  
         [0028]    The control circuit diagram of FIG. 4 also includes a battery charge status detecting circuit  35  electrically coupled to the control unit  30  for detecting a charge status of the rechargeable battery  32 . An emergent help light enabling switch  37  is also coupled to the control unit  30  for enabling an emergent help signal light provided with the present invention. When the user, for example, encounters a disaster or gets lost in mountains or the wild, he or she may use the emergent help light enabling switch  37  to send out a series of flash light signals for help.  
         [0029]    The control circuit of the present invention also includes a charge indicating light  39  that lights up when the portable energy-saving lighting device is in the course of charging; and a battery-low indicating light  40  that lights up when the battery  32  is low.  
         [0030]    The portable energy-saving lighting device  10  of the present invention may be designed to include many other functions. The user may select a desired function through a function-selecting switch block  38 . When doing so, the function-selecting switch block  38  sends out a function-selecting signal S 2  that is received and executed by the control unit  30 . For example, the user may manually switch the portable energy-saving lighting device  10  from an emergency light to a flashlight or a dim light for using outdoors.  
         [0031]    When the user selects the function-selecting switch for a charger, the power converting and charging circuit  31  is enabled to charge the rechargeable battery  32 . Meanwhile, the battery charge status detecting circuit  35  would detect a power level of the rechargeable battery  32  from time to time. In the event the battery  32  is detected as being low in power, the battery-low indicating light  40  would light up. And, when the portable energy-saving lighting device  10  is in the course of charging, the charge indicating light  39  will become on. The battery charge status detecting circuit  35  is also capable of detecting the charging condition of the battery  32 . When the battery  32  is fully charged, the circuit  35  sends a signal to the control unit  30 , so that the power converting and charging circuit  31  automatically stops charging under control of the control unit  30 .  
         [0032]    The present invention may also serve as a battery discharge protection. When the battery  32  discharges and an output voltage of the battery  32  exceeds a specified limit thereof, the present invention will immediately cause the battery  32  to stop discharging to avoid a damage battery.  
         [0033]    The present invention may also serve as an emergency light during a power failure. When the supply of commercial power is in a normal condition, the power converting and charging circuit  31  works as a charging circuit to charge the battery  32 ; and when there is a power failure, the power converting and charging circuit  31  of the present invention automatically switches to the battery  32  to supply power needed for the present invention to function normally.  
         [0034]    The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.