TIDUF85A August   2024  – December 2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
      1. 2.1.1 Subsystems
        1. 2.1.1.1 Arc Detection Channels
          1. 2.1.1.1.1 Isolated Current Measurement
          2. 2.1.1.1.2 Band-Pass Filter
          3. 2.1.1.1.3 Analog-to-Digital Conversion
          4. 2.1.1.1.4 Arc Detection Using Embedded AI Models
        2. 2.1.1.2 Arc Labeling Circuit
          1. 2.1.1.2.1 Isolated String Voltage Measurement
          2. 2.1.1.2.2 Isolated Arc Voltage Measurement With Isolated Comparator
          3. 2.1.1.2.3 Window Comparator for Advanced Labeling
    2. 2.2 Design Considerations
      1. 2.2.1 Current Sensor and Input Stage
      2. 2.2.2 Analog Band-Pass Filter
      3. 2.2.3 Arc-Labeling Circuit
        1. 2.2.3.1 String Voltage Sensing
        2. 2.2.3.2 Arc Gap Voltage Sensing
        3. 2.2.3.3 Differential to Single-Ended Conversion
        4. 2.2.3.4 Window Comparator for Arc Labeling
      4. 2.2.4 Auxiliary Power Supply
      5. 2.2.5 controlCard and Debug Interface
    3. 2.3 Highlighted Products
      1. 2.3.1 TIEVM-ARC-AFE
      2. 2.3.2 TMDSCNCD28P55X – TMDSCNCD28P55X controlCARD Evaluation Module
        1. 2.3.2.1 Hardware Features
      3. 2.3.3 OPA4323 – Quad, 5.5V, 20MHz, Zero-Cross Low-Noise (6nV/√Hz) RRIO Operational Amplifier
      4. 2.3.4 OPA323 – Single, 5.5V, 20MHz, Zero-Cross Low-Noise (6nV/√Hz) RRIO Operational Amplifier
      5. 2.3.5 AMC3330 – ±1V Input, Precision Voltage Sensing Reinforced Isolated Amplifier With Integrated DC/DC
      6. 2.3.6 AMC23C11 – Fast-Response, Reinforced, Isolated Comparator With Adjustable Threshold and Latch Function
  9. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Signal Chain Verification
      1. 3.1.1 Hardware Requirements
      2. 3.1.2 Test Setup
      3. 3.1.3 Test Results
    2. 3.2 Arc Testing
  10. 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 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author
  12. 6Revision History

2.2.3.2 Arc Gap Voltage Sensing

To sense the arc gap voltage, a similar circuit as for the string voltage sensing is used. The sense resistor R110 is increased; however, to increase sensitivity for lower voltage and allow a lower threshold for AMC23C11.

Equation 4. V out = V in × 6490 Ω ( 10 × 316000 Ω + 6490 Ω ) ≈ V in × 0 . 00205

Typical arc gap voltages are in a range from 10V to 50V depending on the string current. It is important to not exceed the maximum allowed input voltage of AMC3330. This is the maximum string voltage. In case the gap is to wide and the arc extinguishes the full string voltage is applied to this voltage divider. Assuming this scenario 1500V is applied, which leads to a input voltage of 3.1V across R110. This is far outside the linear range, but still within the absolute maximum rating.

In addition a isolated comparator AMC23C11 is used to indicate when the arc gap voltage is above a threshold. This threshold is programmed using R128. A 100μA current source is implemented int the REF pin off AMC23C11 to generate the threshold voltage. R128 is selected to the minimum of 200Ω, resulting in a voltage of 20mV at the REF pin. This equals an input voltage of 9.75V. Figure 2-7 shows the schematic.

TIDA-010955 Schematics Arc Voltage Sensing Figure 2-7 Schematics Arc Voltage Sensing