SLVAF01 October   2020 TPS55340

 

  1.   Trademarks
  2. 1Switching Node Voltage Stress from Flyback
    1. 1.1 Reflected Voltage, VOR
    2. 1.2 Leakage Inductance Factor
  3. 2Mitigating Voltage Spike on Switch Node
    1. 2.1 Zener or TVS Clamping
    2. 2.2 Forward Recovery Characteristic of Blocking Diode
  4. 3Design Example with TPS55340
    1. 3.1 Initial Key Designs and Test Results
    2. 3.2 Redesign Procedure to Mitigate Vsw
    3. 3.3 Using Blocking Diode that has a good Tfr
  5. 4Summary
  6. 5References

3.3 Using Blocking Diode that has a good Tfr

Use Blocking Diode (MURS105T3G, On-semi) from TPS55340EVM-148 that has a characteristic as shown in Figure 3-4.

Maximum Forward Recovery Time

(iF = 1.0 A, di/dt = 100 A/µs, Rec. to 1.0 V)

tfr

25ns
GUID-20200927-CA0I-F97K-CVNH-KDVZ9NLFWBQS-low.pngFigure 3-4 Final Test Result After changing Blocking Diode

After changing blocking diode, Vsw was measured to around 32 V which has up to 80~85% of it's AMR, 40 V with some margin.