SNVAA84 October   2023 LMR36506

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Topology Selection
    2. 1.2 From Buck to Fly-Buck-Boost Converter
  5. 2Specific Implementation of the Fly-Buck-Boost Converter
    1. 2.1 Schematic
    2. 2.2 Bill of Materials
  6. 3Test Results
    1. 3.1 Start-up Behavior
    2. 3.2 System Loop Stability
    3. 3.3 Thermal Behavior
    4. 3.4 VOUT Ripple and SW Node Waveforms
    5. 3.5 Efficiency Data
      1. 3.5.1 Efficiency Data for Balanced Loads
      2. 3.5.2 Efficiency Data for Unbalanced Loads
    6. 3.6 Load Regulation
      1. 3.6.1 Load Regulation for Balanced Loads
      2. 3.6.2 Load Regulation for Unbalanced Loads
  7. 4Summary
  8. 5References

3.2 System Loop Stability

Loop stability is an important factor in the system. The guideline for a stable design is a desired phase margin of at least 45°. The loop stability is measured for the designed fly-buck-boost design with the following conditions:

  1. VIN 16 V, Load resistance of 240 Ω between Pos VOUT and Neg VOUT
  2. VIN 24 V, Load resistance of 170 Ω between Pos VOUT and Neg VOUT
  3. VIN 35 V, Load resistance of 150 Ω between Pos VOUT and Neg VOUT

Gain and phase margin plots measured for the previous conditions are shown in Figure 3-12 with the cross-over frequency of approximately 20 kHz and phase margin in the range of 60°. These test points make sure that the design is stable.

GUID-20230906-SS0I-FGWC-8CKM-XQVMM0VTQXLZ-low.png Figure 3-2 System Loop Stability