STDA040 August   2026 BQ76907-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2E-latch System Architecture
  6. 3Typical Design
    1. 3.1 Motor Drivers
    2. 3.2 Network Connection
    3. 3.3 Microcontroller
    4. 3.4 Backup Power
      1. 3.4.1 Discussion of Energy Requirements
        1. 3.4.1.1 Energy Needed By A Single Motor
        2. 3.4.1.2 Requirements for Multiple Motors
        3. 3.4.1.3 Usable energy stored
        4. 3.4.1.4 Derating the Capacitance
      2. 3.4.2 Charging Circuit
      3. 3.4.3 Discharging Circuit
      4. 3.4.4 Bidirectional Charge and Discharge Circuits
      5. 3.4.5 Cell Balancing Circuit
    5. 3.5 Position Sensors
  7. 4Future Trends and Innovations
  8. 5Conclusion
  9. 6References

3.4.3 Discharging Circuit

If the supercapacitor stack supplies a sufficient voltage to drive the motor, a diode or switch circuit can be used to connect the backup supply directly to the motor driver circuit. For example a series of five supercapacitors can be charged to about 13.5V, sufficient to supply motors designed for a 12V battery system. However, as discussed above, the usable energy from the supercapacitors is limited by the minimum voltage needed to reliably drive the motors.

To more effectively use the stored energy, and in cases where the supercap charged voltage is less than the minimum motor voltage, the discharge circuit can use a step-up (boost) configuration. Selection of the boost circuit components depends on the minimum and maximum supercapacitor voltages, as well as the maximum current needed to driver the motors.

Once the design parameters for the discharging circuit are determined, Texas Instruments has a wide variety of buck and buck-boost chips available, as well as tools such as WEBENCH-CIRCUIT-DESIGNER and POWERSTAGE-DESIGNER .