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

3.1 Separate Charge and Discharge FET Control

Application Circuit for Separate Charge and Discharge FET ControlFigure 3-1 Application Circuit for Separate Charge and Discharge FET Control

The devices have two gate drivers (G1, G2) and gate control inputs (INP1, INP2) which can be used to control the discharge FET (Q1) and the charge FET (Q2) separately. With this feature, following four different modes of operation of the switches can be supported in the BMS system.

  • Fully ON state with discharge and charge FETs ON – In this mode of operation, current is allowed to flow in both discharge and charge directions.
  • Fully OFF state with discharge and charge FETs OFF – In this mode of operation, the battery is completed disconnected from the load. This condition can happen during system fault conditions.
  • Ideal Diode from battery to load with discharge FET ON and charge FET OFF – In this mode of operation, current is allowed to flow from battery to load only. Battery charging is disabled in this state as the charge FET is turned OFF. Load current flows through the discharge FET and the body diode of the charge FET. This state of the switches can be used in 12V BMS systems when the system is in sleep state but the always ON loads need to be powered. In sleep state of the system the battery cell monitoring and balancing functions are disabled to reduce the system level IQ hence blocking the charging path makes sure that the uncontrolled charging of the battery does not happen.
  • Ideal Diode from load to battery with discharge FET OFF and charge FET ON – In this mode of operation, battery discharging is blocked and only charging is allowed. This condition can happen when the battery voltage level is very low or if the battery is in a deep discharged state.