SLUAAS8 November   2024 TPS1210-Q1 , TPS4810-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2BMS System Overview
  6. 3Application of TPS1210-Q1 and TPS4810-Q1 to accomplish the Battery Disconnect Switch Design
    1. 3.1 Separate Charge and Discharge FET Control
    2. 3.2 Charge, Discharge FET Control With Pre-Charge Functionality
    3. 3.3 Current Sensing for Short Circuit Protection
    4. 3.4 Reverse Polarity Protection
    5. 3.5 Diagnostics
      1. 3.5.1 FET Diagnostics
      2. 3.5.2 Short Circuit Protection Comparator Diagnostics
      3. 3.5.3 Fault Indication
  7. 4Summary
  8. 5References

3.5.1 FET Diagnostics

A diagnosis concept to verify the functional availability of the battery disconnect switch needs to be implemented without disconnecting vehicle loads. Therefore, either a separate by-pass connection or several switched parallel channels shall be used as shown in Figure 3-7.

System Configuration With Switched Parallel Channels for FET DiagnosisFigure 3-7 System Configuration With Switched Parallel Channels for FET Diagnosis

By this arrangement of parallel disconnect switches, one of the paths can be opened and the functionality of the disconnect switch on the other path can be verified during vehicle operation without disconnecting the vehicle loads. The diagnosis is done during low current operating mode of the vehicle. For verification of the availability of the discharge function the voltage (DIAG_x) in between the charge and discharge circuit breaker shall be measured.

The Table 3-1 gives the information on how the diagnostics can be performed for the charge and discharge FETs.

Table 3-1 Input Control Signals Sequence and FET Status
INP1 INP2 Q1 status Q2 status V(DIAG_1) FET diagnosis

result
Low Low Stuck OFF OFF Low
High Low Stuck OFF OFF Low Q1 stuck OFF detected
Low High Stuck OFF ON High
Low Low OFF Stuck OFF Low
High Low ON Stuck OFF High
Low High OFF Stuck OFF Low Q2 stuck OFF detected

The same approach can be followed for determining the diagnostics of Q3 and Q4 as well. Hence, having two separate gate controls enables diagnostic features, which determine the state of the FET. This can help in safe turn ON and OFF of the BMS power path.