SNVAA94 November   2023 LM5113-Q1 , LMG1205 , LMG1210

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. Introduction
  5. Bootstrap Overcharge
  6. Modeling Bootstrap Overcharge
  7. Changing Bootstrap Components
  8. Zener Diode Method
  9. Schottky Diode Method
  10. Overvoltage Clamp Method
  11. Active Switch Method
  12. Synchronous GaN Bootstrap Method
  13. 10Other Methods of Preventing Bootstrap Overcharge
    1. 10.1 Reducing Dead Time
    2. 10.2 Opting for a Bias Supply
    3. 10.3 Adjusting for Gate Voltage
  14. 11Summary
  15. 12References

Opting for a Bias Supply

A floating bias supply, such as UCC12041-Q1, can bias the high side instead of a bootstrap circuit. These floating bias supplies reference HS and keep Cboot consistently at the set voltage, even if HS goes negative. Floating bias supplies bypass of the overcharging issue entirely and allows for 100 percent duty cycle operation of the driver.

The bias supply option solves the problem but is potentially costlier. A bias supply is more expensive than a bootstrap circuit. Therefore, using a bias supply is rare in non-isolated gate drive circuits.