SNVA940 November   2021 LM5157 , LM5157-Q1 , LM51571-Q1 , LM5158 , LM5158-Q1 , LM51581 , LM51581-Q1

 

  1.   Trademarks
  2. 1LM5157 Boost Design Example
  3. 2Calculations and Component Selection
    1. 2.1  Switching Frequency
    2. 2.2  Inductor Calculation
    3. 2.3  Slope Compensation Check
    4. 2.4  Inductor Selection
    5. 2.5  Diode Selection
    6. 2.6  Output Capacitor Selection
    7. 2.7  Input Capacitor Selection
    8. 2.8  UVLO Resistor Selection
    9. 2.9  Soft-Start Capacitor Selection
    10. 2.10 Feedback Resistor Selection
    11. 2.11 Control Loop Compensation
      1. 2.11.1 Crossover Frequency (fcross) Selection
      2. 2.11.2 RCOMP Selection
      3. 2.11.3 CCOMP Selection
      4. 2.11.4 CHF Selection
    12. 2.12 Power Loss and Efficiency Estimation
  4. 3Implementation Results
  5. 4Small Signal Frequency Analysis
    1. 4.1 Boost Regulator Modulator Modeling
    2. 4.2 Compensation Modeling
    3. 4.3 Open Loop Modeling

2.5 Diode Selection

The power diode must be rated for the average load current and the output voltage with some margin. It should also be able to handle the loss dissipation under the full load. The schottky diode is recommended due to the small reverse recovery time and charge. For this design a 45 V reverse voltage, 10 A average forward current schottky diode is selected. The conduction loss is calculated in Equation 11.

Equation 11. P D _ con = V F ∙ 1 - D ∙ I SUPPLY = 490 mV ∙ 1 - 0.5 ∙ 12 V ∙ 1.6 A 6 V = 0.78 W

where

  • VF is the forward voltage drop of the diode