TIDA035 October   2020

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Two-point Insulation Resistance Measurements
  5. 3Equation Verification by Simulation
  6. 4Op-amp Caused Error Analysis
    1. 4.1 Input offset voltage
    2. 4.2 Input bias current
    3. 4.3 Open-loop gain
  7. 5Summary
  8. 6References

5 Summary

This addendum presents an approach to adapt the existing reference design TIDA-01513 to calculate the exact insulation resistances for two-point leakage errors. It is a necessary feature as dictated in many International Standards. This is applicable in HEVs and EVs as battery management systems, traction inverters, DC/DC converters, onboard chargers, and other subsystems operate at high voltage (higher than 60 V). The insulation resistance measurement error is caused by many factors such as resistance tolerance, op-amp non-ideal performance error, and ADC tolerance. The complete error analysis is beyond the scope of this document. However, the effect of the op-amp non-idealities on the measured insulation resistance is presented, and can serve as a starting point for further analysis.