Abstract:
A cost-effective system architecture and apparatus for programmable automatic power supply testing. The system utilizes board level interface between various system testing modules and an Automatic Test Controller (ATC). The ATC receives coded test requests from the software on an industrial PC and control the various testing modules inside ATC to execute the tests. Test results were sent back to the PC and saved in a result file. A single industrial PC can control two or more ATC&#39;s and test two or more power supply units simultaneously. The ATC based test system is lower cost than the conventional Automatic Test Equipment which uses device level interface and standardized test devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     FIELD OF THE INVENTION 
     This invention relates to a cost-effective system architecture and apparatus for programmable automatic power supply testing. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAMLISTING COMPACT DISC APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     An automatic power supply test system is used to test the performance of a power supply. These test systems automatically measure the parameters such as input voltage, current, power, power factor, output voltage, current, ripple and noise, short-circuit protection, over-voltage protection (OVP) and over-current protection (OCP) of a power supply. An automatic power supply test system is often used in power supply production line to ensure products meet the specifications before they are packed for shipment. An automatic power supply test system usually consists of a central computer with application software to control an automatic power source, a power analyzer, an electronic load, a multi-channel DC voltage/current meter, a ripple/noise measurement device and some special circuitry to tests the protection functions. Furthermore, an automatic power supply test system needs to be user programmable so it can be used to test power supplies of various types and power ratings. 
       FIG. 1  is the block diagram of a typical automatic power supply test system existing today. The system has an industrial PC as the central computer. The PC communicates to various system components via a standard communication bus, such as IEEE488 bus. From the PC, a user can edit the test requirement through the application software. For instance, if the user wants to test the efficiency of a power supply, he/she would, through the application software, set the Automatic Power Source  12  to the nominal input voltage of that power supply, set the electronic load  16  to draw the rated output current of that power supply, set the Power Analyzer  13  to measure the input power of the power supply, and set the Precision DC meters  15  to measure the output voltage and current of the power supply. He/she also needs to setup the application software to calculate the efficiency using the collected measurement results and output the efficiency to a desired file and in desired format. 
     While this conventional architecture has the flexibility to allow the user to program each system components freely, its drawback is the relatively high cost. First, to communicate with the PC through IEEE488 bus, every system component needs to have the IEEE488 interface circuitry. Second, the various system components are often standard equipment that has human interface and other features that are not necessary for the automatic test system. 
     The main objective of the current invention is to achieve lower cost system architecture for the same test functionality. Another objective of the current invention is to have two or more test units operating at the same time, controlled by the same PC, sharing the same programmable power source and operated by a single operator in a power supply production line. This allows higher throughput and better work efficiency for the production line. 
     BRIEF SUMMARY OF THE INVENTION 
     One key part of the current invention is the Automatic Test Controller (ATC). It serves as the core of the automatic test system.  FIG. 2  shows the signal flow of the current invention. The ATC has two serial communication links. One serial link  51  connects the ATC with the industrial PC. The other serial link  55  connects the ATC with the programmable power source. The output of the programmable power source sends the power to the ATC via the power cable  56 . The input of the power supply UUT receives power from the ATC via power cable  57 ; and the output of the power supply UUT is connected to the ATC via power cable  58 . A Digital Signal Processor (DSP) chip inside the ATC works as the main control device for the ATC. The various components of the automatic test system, such as power analyzing module, electronic load module and precision multi-channel DC measurement module, etc., are dedicated modules mounted inside the ATC. These modules are linked to the DSP with board level interface, such as General Purpose Input-output (GPIO) pins, Analog-to-Digital Converter (ADC) inputs, Pulse Width Modulated (PWM) outputs and Serial Peripheral Interface (SPI) ports. The dedicated automatic test components described above are much lower cost compared to the standard test devices used in the conventional automatic test systems. The board level interface between various components and the DSP is much lower cost than the external interface, e.g. IEEE488 bus, used in the conventional automatic power supply test systems. 
     In the current invention, an application software is installed on the industrial PC to allow user programming. A library of power supply test sets is included in the application software. The user can select the required test sets to be performed and setup the corresponding parameter limits. The tests are arranged in a “sequence” which consists of multiple test sets. The PC software transmits the test information one test set at a time with a predetermined protocol from PC to the ATC. The PC application software waits for the results from the previous test set returned by the ATC before sending next test set to the ATC. This process repeats until all test sets in the test sequence are completed. The DSP inside the ATC controls various dedicated components of the test system to perform the requested tests and send back the results. Since the communication between the PC and the ATC is limited to only the encoded test requests and test results that is checked and verified for data integrity, a serial link with moderate speed would be sufficient. In the preferred embodiment, a standard RS232 connection is used for communication between the PC and the ATC. 
     Of all the required system components for the automatic test system, only the automatic power source is external to the ATC. This is necessary since one of the objectives of this invention is to use single power source to supply two or more ATC test units. 
     One aspect of the current invention is the ability to handle very long test sequences. Since the requested tests were sent from the PC to the ATC one frame at a time, there is virtually no limit on how many test sets the system can test. The user can pick any test sets in any combination to form the test sequence he/she wishes. 
     In real applications, the user first creates a test sequence file using the application software for a particular power supply he/she wants to test. The user can then setup the test with the test sequence file using the same application software. When the Unit Under Test (UUT) is connected to the ATC and ready to be tested, the user would press a Test START switch on the ATC. The ATC then sends a START signal to the PC software. The PC software responds by sending the test request to the ATC frame by frame according to the test sequence file. The DSP inside the ATC receives the encoded test request from the PC via the serial link  51 . Based on the decoded test request, the DSP sets up the programmable power source via serial link  55  for the pending test. The DSP also sets up other components necessary for the test through board level interface. When one test set is completed, test results are sent back to the application software on the PC via the serial link  51 . The application software on PC would store the results and send the next frame of test request. If it reaches the end of the test sequence, the PC software and the DSP both loop back to wait for the next UUT. 
     Another aspect of the current invention is to allow a single operator to operate two or more test units simultaneously with a single PC and programmable power source. This is achieved by using a “Sync Box” that synchronizes two or more test units (ATCs) so they can share the same programmable power source. Operating two ATC simultaneously further reduces the equipment cost and improves the production line efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  (Prior Art) is the block diagram illustrating the architecture of an existing automatic power supply test system. 
         FIG. 2  is the block diagram illustrating the signal flows of the current invention. 
         FIG. 3  is the block diagram of the preferred embodiment. 
         FIG. 4  is the block diagram of the Automatic Test Controller (ATC). 
         FIG. 5  is the block diagram depicting the communication between the PC and the ATC. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  illustrates the block diagram of the preferred embodiment of the current invention. The industrial PC  101  is connected to two ATC&#39;s via serial links  109  and  110 . The programmable power source  105  supplies power to both ATC&#39;s ( 102  &amp;  104 ). The pace of the two ATC&#39;s is synchronized by the Sync Box  103 . The Sync Box receives requests to set up the programmable power source from both ATC&#39;s via serial links  111  and  112 . The requests generally come at slightly different time instances. The Sync Box waits for both requests to arrive before setting up the programmable power source via serial link  113 . This ensures both ATC&#39;s to have stable power source at specified voltage and frequency for the upcoming test set. The configuration of a typical test set generally consists of the following parts: 1) Set the power source voltage and frequency; 2) set the load type (Constant Current—CC, Constant Voltage—CV or Constant Resistance—CR load) and load value (A, V or Ohm); 3) select parameters to be tested and their limits. Once the test set information is sent to the ATC&#39;s, the DSP inside each ATC sets up the electronic load and other components that are necessary for the test. Once the test configuration is complete, the DSP&#39;s (in ATC 1  and ATC 2 ) enable the power source and the electronic load to the corresponding UUT (UUT 1   106  and UUT 2   107 ). After specified wait time for the UUT&#39;s to power up and get settled down, each DSP would start measurement for the parameters specified in the test set. The test results from both ATC&#39;s are then sent back to the industrial PC via the serial links  109  and  110 . Still referring to  FIG. 3 ,  105  is a barcode scanner that is used to scan the barcode on the UUT&#39;s. When the system is running two ATC&#39;s as is in the preferred embodiment, the operator needs to scan the barcode on the corresponding UUT&#39;s as instructed by the application software. The barcodes will be saved in the result files in the same row as the test data for the corresponding UUT&#39;s.  108  is a printer for error code printout when a UUT fails the test. The error code indicates which specific type of failure has occurred. In practice, for each model of power supply, a table can be generated to list the possible causes of failure for each error code. This will help the factory repair workers to quickly locate the cause of failure and fix the failed unit. 
       FIG. 4  is the block diagram of the Automatic Test Controller (ATC) and some surrounding components for the automatic power supply test system. The area inside the dotted rectangle is ATC 1  (item  200  in  FIG. 4 ). Referring to  FIG. 4 ,  201  is the DSP controller, the main control device of the ATC. In the preferred embodiment, a DSP with greater than 40 MIPS processing power and greater than 128 KB flash memory is used. The power analyzer module  218  is linked to the DSP through an isolated SPI connection. The sensing elements (voltage and current sensors) on the power analyzer module are directly connected to the power input to the UUT. This results in voltage and current measurements with very low error and distortion. The power analyzer module is based on a high precision 24-bit Sigma/Delta ADC and is isolated by high-speed digital isolator. The DSP communicates with the Electronic Load hardware  223  through a PWM channel and some GPIO&#39;s. The set point of the voltage or current for the electronic load is determined by the pulse width of the PWM signal. An RC filter on the Electronic Load filters the PWM signal to obtain the set point value. The type of the load requested is set by GPIO pins from the DSP. The Multi-channel DC measurement module  224  is linked to the DSP via a SPI connection. The measurement module is based on a high precision 24-bit Sigma/Delta ADC. The measurement module measures the voltage and current of the electronic load (which is also the output voltage and current of the UUT). The measurement module also measures the ripple and noise level at the output of the UUT. The ripple/noise measurement module  225  has signal processing circuitry that generates peak to peak ripple/noise levels in high and low bandwidth. The low bandwidth signal is limited to 200 kHz; the high bandwidth signal is limited to 20 MHz. The peak voltage detect circuit  222  is used to catch the transient peak output voltage of the power supply UUT during power up and power down transient. The peak level is sent to an ADC input on the DSP. The block “DC source for OVP” ( 220 ) is a voltage controlled voltage source. It is controlled by the DSP through a PWM output. This DC voltage source is injected to the UUT to raise its output voltage in small steps for Over Voltage Protection (OVP) test. The DSP would monitor the UUT output in every step of voltage increase until the output of the UUT is shut off. If the trigger voltage is within the specified limit, the DSP would report OVP test passed. If the trigger voltage is outside of the specified limit, or if the UUT does not shut off after injected voltage reaches maximum, the DSP would report OVP test failed. Block  221  is a DC voltage source for Bias output. In some test situations, a bias voltage source comes in handy in simulating the real application condition. For instance, when testing a power supply for battery charging applications, the power supply usually has protection feature that would not start unless a proper battery is connected at the output. The bias voltage can be conveniently used to simulate that battery voltage so the power supply (UUT) output can be enabled and tested with the electronic load inside the ATC. 
     The output of the programmable power source  204  is connected to ATC 1  via power cable  208 ; and to ATC 2  via power cable  209 . Block  205  is a Sync box. It receives voltage setup request from ATC 1  via serial link  211 , and from ATC 2  via serial link  213 . After synchronizing the requests, the Sync box sets up the programmable power source via serial link  210 . Inside ATC 1 , the output of the programmable power source is connected to the solid state relay  229  via power cable  208 . The turn-on phase angle of the solid state relay is controlled by the DSP. The isolated voltage sensor  230  sends the input voltage signal to an ADC pin on the DSP. Based on the input voltage signal, the DSP can control the turn-on time of the solid state relay relative to the phase angle of the input voltage. In most tests, the solid state relay is controlled to turn on when the AC voltage is at zero-crossing. This minimizes the inrush current during power up. For inrush current testing, the solid state relay is controlled to turn on at the peak of the sine wave voltage. This creates the consistent condition for testing the inrush current of the UUT. With the control of the solid state relay, the power from the programmable power source is sent to UUT 1   203  through the power analyzer module  218 . The power analyzer module measures the input RMS current and voltage, average power, reactive power, power factor, and harmonic power. An isolated SPI interface is used for communication between the power analyzer module and the DSP. The Inrush current measurement module  217  consists of a current transformer and a peak detection circuit. The captured peak current is sent to the DSP through an ADC channel. 
       219  is an uncommitted relay to provide flexibility for special test conditions. It can be used to connect or disconnect certain external components to create an intended test condition. The uncommitted relay is controlled by the DSP via a GPIO pin.  216  is a light sensor circuitry that sends an analog signal that is proportional to light intensity to an ADC pin on the DSP. The light sensor is useful to test the visual indicators on power supplies.  215  is a user overwrite switch. This is useful for reporting defects that are not tested by the ATC electrical measurement. For example, if the operator visually detected defects, such as a cracked enclosure, he/she can use the user overwrite switch to enter a fault. The ATC will generate a “user detected failure” as the test result.  206  is a barcode scanner. It is used to enter the barcode on a power supply being tested (UUT). If there is no barcode on the power supply, the ATC software will assign a sequential unit number to identify a particular unit.  207  is a Test START switch that generates the test start signal for both ATC  1  and ATC 2 . 
     The application software on the industrial PC has two parts: 1) Test Sequence Programming; 2) Test Execution. 
     In the programming part, various common power supply tests were grouped into test sets. Each test set includes a number of tests that have a given input voltage and frequency and output load type. Following is a list of the test sets and parameters tested in each test set:
         1. Start-up test:
           Inrush Current   Output Voltage Overshoot   Start-up Time   
           2. Idle test:
           No load (Standby) Input Power   No load (Standby) Input Current   No load (Standby) Input Voltage   
           3. Standard CV (Constant Voltage region) test. Output load is Constant Current (CC) or Constant Resistance (CR) load:
           Input Current   Input Power   Input Voltage   Power Factor   Output Voltage   Output Current   Efficiency   Ripple-Noise High Bandwidth (20 MHz)   Ripple-Noise Low Bandwidth (200 KHz)   
           4. Standard CC (Constant Current region) test. Output load is Constant Voltage (CV) or Constant Resistance (CR) load:
           Input Current   Input Power   Input Voltage   Power Factor   Output Voltage   Output Current   Efficiency   
           5. Output Under Voltage (UVLO) test:
           Output Voltage   
           6. Short Circuit test:
           Input Current   Input Power   Input Voltage   Power Factor   Output Average Current   
           7. Over Current test:
           Over Current Protection Point   Trip Point Voltage   
           8. Over Voltage test:
           Over Voltage Protection Point   
           9. Line Regulation test:
           Line regulation   
           10. Load Regulation test:
           Load regulation   
           11. Power Down test:
           Output voltage overshoot   Holdup time   
           12. Support Function test:
           Delay time   Output load discharge
 
The upper and lower specification limits for each parameters listed in each test set are entered by the user. The user can select any test set and put them in any combination he/she wishes to form a test sequence for a specific power supply model. Inside each test set, the user can selectively check only the parameters that are necessary and leave other parameters unchecked (therefore total test time is reduced). Other test conditions such as wait time before measurement, load-on voltage (UUT output voltage threshold at which the electronic load is switched on), etc. can be set during the test sequence programming. Once the test programming is done, a test sequence file will be generated. The test sequence file can be write-protected by password so unauthorized person cannot alter the test sequence.
   
               

     In the test execution part, the application software has provision for a test operator to load the pre-programmed test sequence file to the software test engine. The operator also needs to specify the file name for the test results. Once the test sequence is loaded and result file specified, the operator can click a start button on the application software to begin the test process. 
       FIG. 5  is a block diagram showing the communication between the PC application software and the ATC DSP software during the test process. When the test execution part of the PC application software is entered, it would configure the software and try to establish serial communication with the ATC. If the ATC is powered up and finished initialization and self-test, the communication will be established successfully. Block  301  is the PC configuration, and block  351  is the ATC initialization and self-test. After PC software configuration is completed, the operator can load the test sequence file, select the result file and click the “START” button in the PC application software. At this point, the system enters the test mode. From the PC side, block  303  sends the test sequence header to the ATC. In the ATC side, block  352  sends an acknowledgement back to the PC. 
     The ATC then polls the Test START signal through a GPIO pin on the DSP. The Test START signal is generated when the test operator have connected the UUT to the ATC properly and press a Test START button on the ATC. If a Test START is detected, the ATC will send a Test START signal to block  304  in the PC side. Once received the Test START signal, the PC software will prompt the operator to scan the barcode on the UUT, if the barcode scan option is selected. If the barcode scan is not selected, the PC software will assign a unit number sequentially for the UUT. Once the barcode or unit number is done, the PC software block  306  sends the encoded test parameters for the 1 st  test set (or 1 st  test frame) in the test sequence. Block  354  in the ATC side receives the encoded test info for the  1 st test set, it will decode and execute the test functions according to the test set parameters. The test results will be sent back to the PC. Block  307  on the PC side saves the test result for the 1st test set to the result file. If all the tested parameters are within the limits (passed), the PC software will send the encoded test parameters for the 2 nd  test set in the test sequence to the ATC. If there is a failure in the 1 st  test set, both the PC software and the ATC DSP software will stop testing for the current UUT. The PC software will display a “test failed” message on the PC screen and loop back to block  304  to wait for the Test START signal for the next UUT. The DSP software will sound buzzer and light up a red LED to indicate the failure, then loop back to block  353  to poll the Test START switch for the next UUT. In the case when all parameters passed in the 1 st  test set and the encoded test information for the 2 nd  test set is sent to ATC, Block  355  will decode, execute the test functions and send test results back to the PC software. On the PC side, block  308  saves the test result in the result file. If all the tested parameters are within the limits (passed), the PC software will send the encoded test parameters for the 3 rd  test set in the test sequence to the ATC. If the 2 nd  test set failed, both the PC software and the ATC DSP software will stop testing for the current UUT. The PC software will display a “test failed” message on the PC screen and loop back to block  304 . The DSP software will sound buzzer and light up a red LED to indicate the failure, then loop back to block  353 . On the ATC side, block  356  performs the same task as block  354  or  355 , except it is for the 3 rd  test set. The test process will continue with the same pattern until block  309  on the PC side. Block  309  saves the (n−1) th  test set result and sends the n th  (last) test set information to block  357  on the ATC side. Block  357  decodes, executes the n th  test set and sends the result to block  310  on the PC side. At completion of block  357 , the DSP software loops back to block  353  for the testing of next UUT. On the PC side, block  310  saves the test result for the n th  (last) test set and display a “pass” message on the PC screen. Upon completion of block  310 , the PC software loops back to block  304  for the testing of next UUT. 
     The operator can repeat the above process to test as many number of UUT&#39;s as he/she wishes. When the operator intends to stop the current test and start the testing of a different power supply model, he/she can click a “Release” button on the PC application software. This will disengage the PC application program from the ATC software. He/she can then load the test sequence file for the new power supply model and setup the new result file. The operator can go through the same process described in paragraph [0025] to test the new power supply model. 
     Although only the preferred embodiment has been described, those skilled in the art could make numerous alterations with the disclosed embodiment without departing from the spirit and scope of the current inventive subject matter set forth in the specification and claims. In methodologies directly or indirectly set forth herein, various steps and operations are described in one order of operation, but those skilled in the art will recognize that steps and operations may be rearranged, replaced or eliminated without necessarily departing from the spirit and scope of the present invention. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail and structure can be made without departing in spirit and scope from the invention as defined by the appended claims.