Abstract:
An exemplary voltage testing device includes a testing circuit and an oscillograph. The testing circuit includes a filtering unit, a rectifier unit, and a voltage dividing unit. The filtering unit receives and filters an alternating current (AC) voltage. The rectifier unit receives the filtered AC voltage and rectifies the filtered AC voltage into a first direct current (DC) voltage. The voltage dividing unit receives the first DC voltage, and dividess the first DC voltage into a second DC voltage equaling an effective value of the AC voltage, thereby the second DC voltage is tested and displayed on the oscillograph.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure generally relates to testing devices, and particularly to a voltage testing device for testing parameters of an alternating current (AC) power supply in a computer system. 
         [0003]    2. Description of the Related Art 
         [0004]    A power supply unit (PSU) in a computer transforms an AC voltage into different steady direct current (DC) voltages. The AC voltage of the PSU is supplied by an AC power supply. In testing performance of the PSU, the AC voltage output to the PSU should be tested, for example, testing the AC voltage value output by the AC power supply and a power margin of the AC power supply when the PSU is turned on and off. 
         [0005]    The AC voltage output by the AC power supply is generally tested by a typical testing device, such as an ATE testing device, which is expensive, and takes up too much space, thereby being inconvenient to reduce cost of the testing. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment. 
           [0008]      FIG. 1  is a block diagram of a voltage testing device, according to an exemplary embodiment, and showing the voltage testing device connected to an AC power supply. 
           [0009]      FIG. 2  is a partial circuit diagram of the voltage testing device shown in  FIG. 1 . 
           [0010]      FIG. 3  is a schematic view of the voltage testing device shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  is a block diagram of a voltage testing device  100 , according to an exemplary embodiment. The voltage testing device  100  is connected to an AC power supply  200 , and configured for testing an AC voltage output by the AC power supply  200 . The AC power supply  200  is also connected to a PSU  300 , and supplies the AC voltage to the PSU  300 . 
         [0012]    The voltage testing device  100  includes a port  11 , a testing circuit  13 , a first test terminal out 1 , a second test terminal out 2 , and an oscillograph  15 . 
         [0013]    The port  11  can be electronically connected to the AC power supply  200  through a plug. The port  11  receives the AC voltage from the AC power supply  200  through the plug. 
         [0014]      FIG. 2 , is the testing circuit  13  of the embodiment. The testing circuit  13  includes a filtering unit  131 , a rectifier unit  133 , and a voltage dividing unit  135 . 
         [0015]    The filtering unit  131  can be a typical filter or a filtering circuit having a filtering function. The filtering unit  131  is connected to the port  11 , and is thereby connected to the AC power supply  200  through the port  11  to filter the AC voltage from the AC power supply  200 . 
         [0016]    The rectifier unit  133  is connected to the filtering unit  131 , and receives the filtered AC voltage from the filtering unit  131  to rectify the filtered AC voltage into a first DC voltage. In this embodiment, the rectifier unit  133  is a bridge circuit, and includes a first diode D 1 , a second diode D 2 , a third diode D 3 , and a fourth diode D 4 . A first output of the filtering circuit  131  is connected between the first and second diodes D 1 , D 2 . A second output of the filtering circuit  131  is connected between the third and fourth diodes D 3 , D 4 . A first terminal of the voltage dividing circuit  135  is connected between the second and third diodes D 2 , D 3 , and used for receiving the first DC voltage. A second terminal of the voltage dividing circuit  135  is connected between the first and fourth diodes D 1 , D 4 , and is also connected to ground. 
         [0017]    The testing circuit  13  further includes a capacitor C 1 . One terminal of the capacitor C 1  is connected between the second and third diodes D 2 , D 3 . The other terminal of the capacitor C 2  is connected to ground. The capacitor C 1  is configured for cooperating with the filtering unit  131 , and making the rectifier unit  133  output a pure first DC voltage. In one embodiment, a capacitance of the capacitor C 1  is about 1 μF. 
         [0018]    The voltage dividing unit  135  receives the first DC voltage output by the rectifier unit  133 , and divides the first DC voltage into a second DC voltage. In detail, the voltage dividing unit  135  includes a first resistor R 1 , a second resistor R 2 , and a third resistor R 3 . One terminal of the first resistor R 1  is connected between the second and third diodes D 2 , D 3 . The other terminal of the first resistor R 1  is connected to ground through the second and third resistors R 2 , R 3  which are connected in series. 
         [0019]    The first test terminal out 1  is connected between the first and second resistors R 1 , R 2 . The second test terminal out 2  is connected to ground. 
         [0020]    Referring to  FIG. 3 , the oscillograph  15  includes a testing probe  151  and a grounding probe  152 . The testing probe  151  is connected to the first test terminal out 1 . The grounding probe  152  is connected to the second test terminal out 2 . Thus, the oscillograph  15  can test and display the second DC voltage value through the connection between the testing probe  151  and the first test terminal out 1 , and the connection between the grounding probe  152  and the second test terminal out 2 . 
         [0021]    The voltage testing device  100  further includes a housing  17 . The port  11 , the first test terminal out 1 , and the second test terminal out 2  are all mounted on a surface of the housing  17 . The testing circuit  13  is mounted in the inner of the housing  17 , thereby preventing injury to an operator due to an exposed AC voltage. 
         [0022]    In use, the testing circuit  13  is received in the housing  17 , and establishes a connection with the port  11 , the first test terminal out 1 , and the second test terminal out 2 . Then, the voltage testing device  100  is electronically connected to the AC power supply  200  through the port  11 , and the testing probe  151  and the grounding probe  152  of the oscillograph  15  are respectively connected to the first and second test terminals out 1 , out 2 . The filtering unit  131  receives and filters an AC voltage from the AC power supply  200 , thereby transmitting the filtered AC voltage to the rectifier unit  133 . The rectifier unit  133  rectifies the filtered AC voltage into a first DC voltage Vout, and the first DC voltage Vout can be calculated according to the following formula (1): 
         [0000]        V out=√{square root over (2)}*Vac  (1)
 
         [0000]    where the parameter Vac is an effective value of the AC voltage. 
         [0023]    Then, the voltage dividing unit  135  receives the first DC voltage Vout, and divides the first DC voltage Vout into a second DC voltage Vdc. The second DC voltage Vdc can be calculated according to the following formula (2): 
         [0000]    
       
         
           
             
               
                 
                   Vdc 
                   = 
                   
                     Vout 
                     * 
                     
                       
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                       
                         
                           R 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0024]    According to the above formulas (1) and (2), the parameter Vdc can be calculated according to the following formula (3): 
         [0000]    
       
         
           
             
               
                 
                   Vdc 
                   = 
                   
                     
                       2 
                     
                     * 
                     Vac 
                     * 
                     
                       
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                       
                         
                           R 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0025]    Thus, via selecting corresponding first to third resistors R 1 -R 3 , and making the resistances of the first to third resistors R 1 -R 3  satisfy the following formula (4): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       2 
                     
                     * 
                     
                       
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                       
                         
                           R 
                            
                           
                               
                           
                            
                           1 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           R 
                            
                           
                               
                           
                            
                           3 
                         
                       
                     
                   
                   = 
                   1 
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0026]    In this way, the effective value of the AC voltage Vac will equal to the second DC voltage Vdc, thereby the second DC voltage Vdc being displayed on the oscillograph  15  instead of the effective value of the AC voltage Vac. 
         [0027]    Accordingly, in use of the voltage testing device  100 , the operator only needs to select corresponding first to third resistors R 1 -R 3 , and make the resistances of the first to third resistors R 1 -R 3  satisfy a corresponding formula. Then a test of an AC voltage output to the PSU  300  can be effectively transformed into a test of a DC voltage, thereby simplifying a structure of voltage testing device  100 , and reducing a cost of the testing. 
         [0028]    In the present specification and claims, the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. Further, the word “comprising” does not exclude the presence of elements or steps other than those listed. 
         [0029]    It is to be also understood that even though numerous characteristics and advantages of exemplary embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of arrangement of parts within the principles of this disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.