Abstract:
Disclosed herein is a DC uninterruptible power system which is composed of a AC voltage and frequency detecting circuit, an AC to DC conversion and charging circuit, a DC voltage conversion circuit, a load detecting circuit, an output voltage detecting circuit, and a control circuit. The UPS of the present invention can minimize the power loss due to one stage conversion so as to improve system efficiency, and maintain a stable output voltage. Beside, a lighting equipment is installed for illuminating surroundings in case the utility voltage becomes abnormal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an uninterruptible DC power system, (DC UPS) and more particularly, to an uninterruptible DC power system to be served as an emergency power source which is capable of effectively reducing the line loss when applied to electric appliances attached with AC/DC switchable power suppliers (SW power).  
           [0003]    2. Description of the Prior Art  
           [0004]    Utility electric power is relied on by common domestric consumers as their power source for electric appliances. In case of the occurrence of abnormal states such as power outage, an undervoltage, or a over voltage, or an abnormal frequency, the user&#39;s loads loose their power supply so that the unterruptible power system (UPS) whose battery unit normally under floating charge state from the utility source takes over the responsibility for an emergency source to supply the emergency power to those user&#39;s loads which have lost the utility power supply.  
           [0005]    Normally, the power output of a conventional UPS is in the form of AC. The operational principle of an UPS is inputting the AC utility power by way of an AC to DC converter so as to store the DC energy in the UPS by a DC charging circuit, and then supplies the stored DC electric power to the loads by converting back to AC when the utility power is out thereby serving as a stand by power source. Meanwhile, in the aforesaid UPS scheme, the electric power is firstly converted from AC to DC, and then converted back from DC to AC, through repeated conversion of electric power as such, the electrical circuits used for such repeated conversion of power become complicated with increased circuit loss as well.  
           [0006]    Therefore, an invention devoting to resolving aforesaid disadvantages of current UPS so as to upgrade the quality of the UPS is definitely necessary. The present inventor has delved into this matter with long time efforts and come to realization of the present invention.  
         SUMMARY OF THE INVENTION  
         [0007]    It is a first object of the present invention to provide a newly developed DC UPS which is capable of reducing electric power loss during conversion so as to improve the efficiency and effectiveness of the system, and start a lighting equipment in case the utility AC voltage becomes abnormal.  
           [0008]    It is a second object of the present invention to provide a newly developed DC UPS which is capable of maintaining a stable output voltage without being influenced by the input source.  
           [0009]    It is a third object of the present invention to provide a newly developed DC UPS which is capable of performing power conversion by only one stage so as to minimized the complexity of the circuit scheme and also improve environmental conscious effect.  
           [0010]    To achieve the aforesaid objects, the DC UPS of the present invention is composed of at least a AC voltage and frequency detecting circuit, an AC to DC conversion and charging circuit, a DC voltage conversion circuit, a load detecting circuit, an output voltage detecting circuit, and a control circuit. It is essentially emphasized that the invention is devoted to reducing the power loss owing to power conversion so as to improve the system efficiency and save energy. Moreover, the DC UPS of the present invention can maintain a stable output voltage, and by means of detecting utility AC voltage, a lighting equipment can be turned on to illuminate surroundings in case the utility supply voltage is found to be abnormal. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The above objects and other advantages of the present invention will become more apparent by describing in detail the preferred embodiments of the present invention with reference to the attached drawings in which:  
         [0012]    [0012]FIG. 1 is a layout scheme of the DC UPS in a first embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a layout scheme of the DC UPS in a second embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is an electric circuit diagram of the DC UPS in a first embodiment of the present invention;  
         [0015]    [0015]FIG. 4 is an electric circuit diagram of the DC IPS in a second embodiment of the present invention; and  
         [0016]    [0016]FIG. 5 is an illustrative diagram in which the DC UPS of the present invention is applied to an AC/DC switchable power supplier (SW power). 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    The DC UPS provided by the present invention is well applicable to an electrical appliance using the SW power as its power supplier so as to reduce circuit loss due to power conversion and improve system efficiency and saving energy by only one stage conversion.  
         [0018]    Except the complexity in the circuit design is minimized, the invention further contributes to environmental security protection and maintaining a stable output voltage.  
         [0019]    Referring to FIG. 1 and FIG. 3, in which a layout scheme (FIG. 1) and an electric circuit diagram (FIG. 3) of the DC USP in a first embodiment of the present invention are shown. This embodiment belongs to an ON-LINE system which essentially comprises a lighting equipment  10 , an AC voltage and frequency detecting circuit  11 , an AC to DC conversion and charging circuit  12 , a battery unit  13 , a DC voltage conversion circuit  14 , a load detecting circuit  15 , an output voltage detecting circuit  16 , an inner system power source  17 , a controller circuit  18 , and a switch  19 . So far there is an utility AC available, a signal is delivered to the controller circuit  18  from the AC voltage and frequency detecting circuit  11  to actuate the AC to DC conversion and charging circuit  12  and the switch  19  for outputting DC power and charging the battery unit  13 .  
         [0020]    After finishing charging the battery unit  13 , a notification signal is sent to the controller circuit  18  for interrupting the charging circuit  12  so as to protect the battery unit  13 . In case the voltage, or frequency etc. of the utility AC power is found to be abnormal, the controller circuit  18  is informed by the AC voltage and frequency detecting circuit  11  of this state so as to start operation of the DC voltage conversion circuit  14  for continuously supplying power to the loads thereby attaining the uninterrupted power supply, and turn on the lighting equipment  10  to illuminate surroundings.  
         [0021]    The inner system power source  17  is for supplying power to the inner components of UPS. Besides, the controller circuit  18  can control the output voltage at a predetermined value according to the detected results obtained by the output voltage detecting circuit  16 . And, the load detecting circuit  15  is for detecting whether there is an overloading at the output terminal and informing the controller circuit  18  of the detected results.  
         [0022]    In the first embodiment, in addition to servicing for the electric appliances equipped with the SW power, a DC to AC inverter may be added to the present invention for supplying AC power to other appliances which have no attached SW power.  
         [0023]    Referring to FIG. 2 and FIG. 4, in which a layout scheme (FIG. 2) and an electric circuit diagram (FIG. 4) of the UPS in a second embodiment of the present invention are shown. This embodiment belongs to an OFF-LINE system which essentially comprises a lighting equipment  20 , an AC voltage and frequency detecting and charging circuit  21 , a battery unit  22 , a DC to AC convertion circuit  23 , a load detecting circuit  24 , and output voltage detecting circuit  25 , an inner system power source  26 , a controller circuit  27 , and an electromagnetic switch  28 . So far there is an utility AC input, the AC voltage and frequency detecting and charging circuit  21  delivers a signal to the battery unit  22  informing that it is to be charged and informing the controller circuit  27  for actuating the electromagnetic switch  28  to output an AC power.  
         [0024]    When finished charging of the battery unit  22 , a signal is sent to the controller circuit  27  to stop charging so as to protect the battery unit  22  from being overcharged. In case the voltage, or frequency etc. of the utility AC power is found to be abnormal, the controller circuit  27  is informed by the AC voltage and frequency detecting and charging circuit  21  of this state so as to start operation of the DC voltage conversion circuit  23  and the electromagnetic switch  28  continuously supplying power to the loads thereby attaining the aim of uninterrupted power supply.  
         [0025]    The inner system power source  26  is for supplying power to the inner components of UPS. Besides, the controller circuit  27  can control the output voltage at a predetermined value according to the detected results obtained by the output voltage detecting circuit  25 . And, the load detecting circuit  24  is for detecting whether there is an overloading at the output terminal and informing the controller circuit  27  of the detected results.  
         [0026]    In the second embodiment, in addition to servicing for the appliances equipped with the SW power, a DC to AC inverter may be added to the present invention for supplying AC power to other appliances which have no attached SW power.  
         [0027]    Referring to the illustrative diagram shown in FIG. 5 in which the UPS of the present invention is applied to an AC/DC switchable power supplier (SW power). If the utility AC power supply is working normally, the power is stored in a battery unit  31  after AC to DC conversion. In case the utility power fails to keep its normal state which being detected by a detecting circuit  32 , a controller circuit  33  sends a signal to an electromagnetic switch  35  of a SW power  34  which actuates a DC voltage conversion circuit  36  to produce a high DC voltage. This high DC voltage is stepped down to a low voltage DC as an output power via another DC voltage conversion circuit  37 .  
         [0028]    It emerges from the description of the above embodiments that the invention has several noteworthy advantages which are not found in any conventional UPS, in particular;  
         [0029]    1. The power loss in conversion is reduced which leads to energy saving and improving system efficiency.  
         [0030]    2. The output voltage is not affected by variation of the input voltage so that the UPS of the present invention can always maintain a stable output voltage.  
         [0031]    3. Power conversion is performed through only one stage so that the circuit scheme is simplified which also results in an environmental conscious effect.  
         [0032]    4. In addition to taking over the mission of continuously supplying power to the loads, the UPS of the present invention is capable of turning on its lighting equipment so as to illuminate surroundings.  
         [0033]    Only two preferred embodiments of the present invention are exemplified to shown its versatility and novelty, it is to be understood that the present invention is capable of use in various other combination and environments and is capable of changes or modification within the scope of inventive concept as expressed in appended claims.