TIDUEZ9B July   2022  – April 2023

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Isolated Current Measurement
    2. 1.2 Band-Pass Filter
    3. 1.3 Analog-to-Digital Conversion
    4. 1.4 Arc Detection Algorithm
    5. 1.5 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Current Transformer Circuit
      2. 2.2.2 Analog Band-Pass Filter
      3. 2.2.3 Analog-to-Digital Conversion
      4. 2.2.4 Power Supply
      5. 2.2.5 Debugging and Status Indication Options
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS259474
      2. 2.3.2 TPS562202
      3. 2.3.3 TPS745
      4. 2.3.4 OPAx322
      5. 2.3.5 ADS8363
      6. 2.3.6 REF5025
      7. 2.3.7 TMDSCNCD280049C
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware and Software Requirements
      1. 3.1.1 Hardware
      2. 3.1.2 Software
        1. 3.1.2.1 Arc Detection Theory
        2. 3.1.2.2 Software Implementation
    2. 3.2 Test Setup
      1. 3.2.1 ControlCARD Configuration
      2. 3.2.2 Setup for Hardware and Software Validation
      3. 3.2.3 Setup for Arc Testing
    3. 3.3 Test Results
      1. 3.3.1 Test Results of Hardware and Software Validation
      2. 3.3.2 Testing With Arcs
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  10. 5About the Author
  11. 6Revision History

3.3.1 Test Results of Hardware and Software Validation

Figure 3-1 shows the setup used for this test. There are sinusoidal input signals with different frequencies applied to the CH1 input and the sampled signal. The computed arc noise is observed within Code Composer Studio. Figure 3-3 and Figure 3-4 show the Expressions window for the external ADC version and for the internal ADC version after loading the software to the controlCARD, but before starting the code.

GUID-20220614-SS0I-3NWK-ZJ5P-WMGSRRH9SSM4-low.png Figure 3-3 Expressions Window for External ADC
GUID-20220614-SS0I-0NX9-LM2W-PQTRXFPBF5ZW-low.png Figure 3-4 Expressions Window for Internal ADC
  • CH1Data: Array to store 1024 samples of the input signal.
  • AD_result: Array in which the computed arc noise is stored. Each element represents the outcome of the analysis of 1024 samples.
  • BufferFillFLagCH1 (only for external ADC): Flag to start the arc detection in case of the external ADC solution. Internal ADC project starts directly after boot up.
  • ArcTunningParams: See Table 3-5. In this case the frequency band for arc detection is set to 30 kHz to 60 kHz.

After starting the software and enabling the continuous refresh option in the expressions window, the displayed values change, as shown in Figure 3-5. The input signal as well as the AD_result variable can be observed in the graphing tool. Figure 3-6 shows the sampled input signal for a 20-kHz sinusoidal input current.

GUID-20220614-SS0I-TCNR-9XFD-XDPWQ1RPKCBN-low.png Figure 3-5 Expressions Window for 20 kHz Sinusoidal Input Current
GUID-20220614-SS0I-KVQB-1M45-79ZFXQSCS90S-low.png Figure 3-6 Graph of CH1Data at 20-kHz Sinusoidal Input Current
Table 3-4 shows the AD_result value for external and for internal ADC software for different input frequencies. For frequencies inside the arc detection frequency band, higher values are observed for AD_result than expected. In general, the change is more significant for the external ADC solution, which is expected because of the higher resolution of 16 bit versus 12 bit of the internal ADC.
Table 3-4 AD_result Values for Different Sinusoidal Inputs With External ADC and Internal ADC
FREQUENCY IN Hz AD RESULT WITH EXTERNAL ADC AD_result WITH INTERNAL ADC
10000 46 23
20000 43 28
30000 89 47
40000 98 67
50000 80 49
60000 77 46
70000 35 33
80000 12 30
90000 16 29
100000 19 25