SLUAAV9 March   2024 LM2005 , LM2101 , LM2103 , LM2104 , LM2105 , LM25101 , LM27222 , LM2724A , LM5100A , LM5100B , LM5100C , LM5101 , LM5101A , LM5101B , LM5101C , LM5102 , LM5104 , LM5105 , LM5106 , LM5107 , LM5108 , LM5109 , LM5109A , LM5109B , LM5109B-Q1 , LM5113-Q1 , LM76003 , LMG1205 , LMG1210 , SM72295 , SM74104 , TPS28225 , TPS28225-Q1 , TPS28226 , TPS2832 , TPS2836 , TPS2837 , UC2950 , UCC27200 , UCC27200-Q1 , UCC27200A , UCC27201 , UCC27201A , UCC27201A-DIE , UCC27201A-Q1 , UCC27211 , UCC27211A , UCC27211A-Q1 , UCC27212 , UCC27212A-Q1 , UCC27222 , UCC27282 , UCC27282-Q1 , UCC27284 , UCC27284-Q1 , UCC27288 , UCC27289 , UCC27301A , UCC27301A-Q1 , UCC27311A , UCC27311A-Q1 , UCC27710 , UCC27712 , UCC27712-Q1 , UCC27714

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Design and Potential Risk in Certain Application Scenario
  6. 3Analysis of Potential Problem
    1. 3.1 High Duty Cycle Causes High Current Stress in Bootstrap Diode
      1. 3.1.1 Mode 1
      2. 3.1.2 Mode 2
      3. 3.1.3 Mode 3
      4. 3.1.4 Mode 4
    2. 3.2 Influence by the Extra Voltage Source
  7. 4Design Recommendation
  8. 5Summary
  9. 6References

4 Design Recommendation

To achieve this design properly, V2 must be larger than V1.

Equation 3. V2>V1

When V2 is larger than V1, bootstrap diode can keep reverse bias all the time which means V1 can only provide power to internal circuits of gate driver and low side FET. Energy to drive high side FET can come from V2.

Based on the previous analysis, we can also improve the current ability of gate driver to avoid the risk. The suggestion is to add external bootstrap diode such as Schottky or fast recovery diode.

Or we can just use half-bridge gate driver without built-in bootstrap diode. Because in this design, bootstrap diode can always work in reverse bias, so we can just simply remove this diode and the requirement of power supply’s amplitude can not exist. For example, we can use UCC27888 to simplify the design process.