Abstract:
A testing system for testing a conversion efficiency of a power supply unit (PSU) includes a power meter, a plurality of switches, a multimeter, a microcontroller unit, and a data processing device. The power meter is utilized to measure an input power supplied to the power supply unit. The multimeter is utilized to measure an output power of PSU. The microcontroller unit is configured for automatically switching the plurality of switches for enabling the multimeter to measure the output power of power supply. The data processing device is utilized to read data measured from the power meter and the multimeter and calculate a conversion efficiency of the PSU.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a testing system, and more particularly to a testing system for testing conversion efficiency of a power supply. 
     2. Description of Related Art 
     Since the energy policy of different countries varies, most of the present power supply devices adopt a specification that maintains a conversion efficiency of the Power Supply Unit (PSU) over 80%. The conversion efficiency is the ratio of direct current (DC) output power to alternating current (AC) input power, expressed in percentage, with 100% being perfect. If a PSU requires an input of 400 W in AC to deliver 300 W in DC, then it has an efficiency of 75%, at this point, and 25% of the power is lost as heat within the power supply. 
     Referring to  FIG. 4 , a typical testing system for testing a conversion efficiency of a PSU  300  includes a AC source  100  applied to the PSU  300 , a power meter  200 , a first multimeter  400 , a second multimeter  500 , a first rotary switch  51 , a second rotary switch S 2 , a third rotary switch S 3 , and a DC electronic load  600 . The switches S 1 , S 2 , S 3  are 1 pole 6 way switches. The power meter  200  is connected between the AC source  100  and the PSU  300  for measuring AC input power to the PSU  300 . The PSU  300  output power rails include: 12V, 12 VCPU (a power rail for CPU), 5V, 3.3V, −12V, and 5 Vaux (standby voltage of 5V). Each of the power rails&#39; output from the PSU  300  is supplied to the DC electronic load  600  via a resistor. The first rotary switch S 1  is turned from one conducting position to another. Thus, the first multimeter  400  is capable of connecting to each of the power rails and measuring an effective output voltage of each of the power rails. The rotary switches S 2 , S 3  are turned from one conduction position to another for connecting the second multimeter  500  to each of the resistors in a parallel connection. Thus, an output current of each of the power rails can be calculated using the formula: I=U/R. An output power of each of the power rails can be calculated by the formula: P=UI. A total output power of the PSU  300  equals the sum of all the output power of the power rails. Then the conversion efficiency of the PSU  300  equal to a ratio of the total output power of the PSU  300  to the AC input power can be calculated to determine whether the PSU  300  achieves the standard. 
     However, the typical testing system needs an operator to manually turn the rotary switches and record the current and voltage of each of the power rails, which is inefficient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a testing system for testing a conversion efficiency of a power supply unit (PSU); 
         FIG. 2  depicts a single chip microcontroller (hereinafter MCU) and one peripheral circuit coupled to the MCU; 
         FIG. 3  depicts other peripheral circuits coupled to the MCU; and 
         FIG. 4  depicts a typical testing system, according to the prior art, for testing a conversion efficiency of a power supply unit (PSU). 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIG. 1 , an embodiment of a testing system for testing a conversion efficiency of a PSU  20  includes an MCU  10 , an AC switch  30 , a power meter  40 , an AC source  50 , a computer  60 , a DC electronic load  70 , and a plurality of switches K 1 -K 13 . The PSU  20  is capable of outputting power rails of 12V, 12 Vcpu, 5V, 3.3V, −12V, 5 Vaux respectively coupled to resistors R 1 , R 2 , R 3 , R 4 , R 5 , R 6 . The power rails output from the PSU  20  are supplied to the DC load  70  via the resistors R 1 -R 6 . The computer  60  is a data processing device for calculating a conversion efficiency of the PSU  20 . 
     The MCU  10  sends a signal to control the AC switch  30  and sends a power supply on (PSON) signal to the PSU  20 . The AC switch  30  is configured to electrically connect/disconnect the AC source  50  to/from the PSU  20 . When the AC source  50  is electrically connected to the PSU  20  and the PSON signal is at a low level (logic “0”), the PSU  20  is powered on and outputs the power rails. 
     The MCU  10  further sends signals to control On/Off states of the switches K 1 -K 13 . The switch K 13  is a double pole-double throw switch. When the switch K 13  is turned to a contact point A and ground in a first closed position, the multimeter  80  can measure an effective voltage of each of the power rails after each of the switches K 1 -K 6  is closed in turn. For example, if the switch K 13  is turned to the contact point A and ground (GND) and the switch K 1  is closed, and keeping other switches open, the multimeter  80  is connected to power rail of 12V and capable of measuring the effective voltage of the 12V power rail. If the switch K 13  is turned to the contact point A and ground (GND) and the switch K 2  is closed, keeping other switches open, the multimeter  80  can measure the effective voltage of the 12 Vcpu power rail. 
     When the switch K 13  is turned to contact points B&amp;C and at a second closed position, the multimeter  80  can measure a voltage drop across each of the resistors R 1 -R 6 . For example, if the switch K 13  is turned to contact points B&amp;C and the switch K 7  is turned to a closed position, keeping other switches open, the multimeter  80  and the resistor R 1  are connected in parallel, and the multimeter  80  can measure the voltage drop across the resistor R 1 . A current flow through each of the resistors R 1 -R 6  can be calculated using the formula: I=U/R. An output power of each of the power rails can be calculated using the formula: P=UI. Then a total output power of the PSU  20  equal to a sum of the output powers of all the power rails (P=P 1 +P 2 +P 3 + . . . Pn) can be calculated. 
     An AC input power applied to the PSU  20  can be measured by the power meter  50 . Thus, a conversion efficiency of the PSU  20  that equals a ratio of the total output power to the AC input power can be calculated. 
     Referring also to  FIGS. 2 and 3 , pins P 2 . 0 -P 2 . 6  of the PSU  20  respectively connect to a first switch circuit  11 , a second switch circuit  12 , a third switch circuit  13 , a fourth switch circuit  14 , a fifth switch circuit  15 , a sixth switch circuit  16 , and a seventh switch circuit  17 , for controlling On/Off states of the switches K 1 -K 13 . A pin P 13  of the PSU  10  sends an alternating current switch (AC SW) signal to control the AC switch  30  for electrically connecting the AC source  50  to the PSU  20 . A pin P 10  of the PSU  10  sends a low level PSON signal to the PSU  20  to power on the PSU  20 . 
     The first switch circuit  11  includes a first PNP transistor Q 1 , a first diode D 1 , and the switches K 1 , K 7 . A base electrode of the transistor Q 1  connects to the pin P 2 . 0  of the MCU  10  via a resistor. An emitting electrode of the transistor Q 1  is fed with a power source VCC. A collecting electrode of the transistor Q 1  is connected to a cathode of the first diode D 1 . An anode of the first diode D 1  is connected to ground. The switch K 1  is a single pole-single throw relay switch, and the switch K 7  is a double pole-single throw relay switch. The first diode D 1 , switches K 1 , K 7  are connected in parallel. When the pin P 2 . 0  of the MCU  10  sends a high level signal to the base electrode of the transistor Q 1 , the transistor Q 1  is rendered non-conductive; a voltage level of the collecting electrode of the transistor Q 1  is low; and there is nearly no current flowing through a relay coil (not shown) of each of the switches K 1 , K 7 , thereby keeping the switches K 1 , K 7  open. When the pin P 2 . 0  of the MCU  10  sends a low level signal to the base electrode of the transistor Q 1 , the transistor Q 1  is rendered conductive; a voltage level of the collecting electrode of the transistor Q 1  is high; and there is an electric current (exceeding a threshold current to turn on the relay switch) flowing through the relay coil of each of the switches K 1 , K 7 , thereby turning on the switches K 1 , K 7 . 
     The second switch circuit  12  includes a second PNP transistor Q 2 , a second diode D 2 , and the switches K 2 , K 8 . The switch K 2  is a single pole single throw relay switch, and the switch K 8  is a double pole single throw relay switch. 
     The third switch circuit  13  includes a third PNP transistor Q 3 , a third diode D 3 , and the switches K 3 , K 9 . The switch K 3  is a single pole single throw relay switch, and the switch K 9  is a double pole single throw relay switch. 
     The fourth switch circuit  14  includes a fourth PNP transistor Q 4 , a fourth diode D 4 , and the switches K 4 , K 10 . The switch K 4  is a single pole single throw relay switch, and the switch K 10  is a double pole single throw relay switch. 
     The fifth switch circuit  15  includes a fifth PNP transistor Q 5 , a fifth diode D 5 , and the switches K 5 , K 11 . The switch K 5  is a single pole single throw relay switch, and the switch K 11  is a double pole single throw relay switch. 
     The sixth switch circuit  16  includes a sixth PNP transistor Q 6 , a sixth diode D 6 , and the switches K 6 , K 12 . The switches K 6 , K 12  are both double pole single throw relay switches that are controlled by the MCU  10 . 
     In one embodiment, an operation principle of each of the second switch circuit  12 , the third switch circuit  13 , the fourth switch circuit  14 , the fifth switch circuit  15 , and the sixth switch circuit  16  is similar to that of the first switch circuit  11  described above. 
     The seventh switch circuit  17  includes a seventh PNP transistor Q 7 , a seventh diode D 7 , and the switch K 13 . The switch K 13  is a double pole double throw relay switch. The switch K 13  is controlled by the MCU  10  and capable of turning to a first closed position (an original position) electrically connecting to the contact point A and ground (GND) or a second closed position electrically connecting to the contact points B&amp;C. When the pin P 2 . 6  of the MCU  10  sends a high level signal to a base electrode of the transistor Q 7 , the transistor Q 7  is rendered non-conductive; a voltage level of a collecting electrode of the transistor Q 7  is low; there is nearly no a current flow through a coil (not shown) of the relay switch K 13 ; and the switch K 13  remains at the first closed position (original position). When the pin P 2 . 6  of the MCU  10  sends a low level signal to a base electrode of the transistor Q 7 , the transistor Q 7  is rendered conductive; a voltage level of a collecting electrode of the transistor Q 7  is high; a current flow through the coil (not shown) of the relay switch K 13  exceeds a threshold current that turns the switch K 13  to the second closed position from the first closed position. 
     During testing, the switches K 1 -K 13  is switched on/off according to a sequence predetermined by the MCU  10 , and the multimeter  80  measures the effective output voltage on each of the power rails of the PSU  20 , measures the drop voltage across each of the resistors R 1 -R 6 , and sends the measured data to the computer  60 . The power meter  40  measures the AC input power supplied to the PSU  10  and sends the measured data to the computer  60 . The computer  60  stores data of the resistors R 1 -R 7  and has great data processing capability to calculate the current flow of each of the power rails of the PSU  20  using the formula I=U/R, the total output power of the PSU  20 , and the conversion efficiency of the PSU  20 . Then the computer  60  compares the conversion efficiency of the PSU  20  with the standard ratio (such as 80%) and determines whether the conversion efficiency of the PSU  20  meets the standard. 
     While the present disclosure has illustrated by the description preferred embodiments, and while the preferred embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications within the spirit and scope of the present disclosure will readily appear to those skilled in the art. Therefore, the present disclosure is not limited to the specific details and illustrative examples shown and described.