SLVAF95 april   2023 TPS7H5001-SP

 

  1.   Abstract
  2.   Trademarks
  3.   Description
  4.   Features
  5.   Applications
  6. 1System Overview
    1. 1.1 Block Diagram
    2. 1.2 Design Considerations
    3. 1.3 System Design Theory
      1. 1.3.1 Switching Frequency
      2. 1.3.2 Transformer
      3. 1.3.3 RCD and Diode Clamp
      4. 1.3.4 Output Diode and MOSFET
      5. 1.3.5 Output Filter and Capacitance
      6. 1.3.6 Compensation
      7. 1.3.7 Controller Passives
  7. 2Test Results
    1. 2.1 Testing and Results
      1. 2.1.1 Test Setup
      2. 2.1.2 Test Results
        1. 2.1.2.1 Efficiency
        2. 2.1.2.2 Frequency Response
        3. 2.1.2.3 Thermal Characteristics
        4. 2.1.2.4 Output Voltage Ripple
        5. 2.1.2.5 Load Step
        6. 2.1.2.6 Start-Up
        7. 2.1.2.7 Shutdown
        8. 2.1.2.8 Component Stresses
  8. 3Design Files
    1. 3.1 Schematics
    2. 3.2 Bill of Materials
    3. 3.3 Assembly Drawings
  9. 4Related Documentation

1.3.6 Compensation

The poles and zeros of a flyback converter are calculated with Equation 33 through Equation 38.

Equation 33. fZESR=1+D2π×Cout×RESR
Equation 34. f Z E S R = 1 + 0 . 33 2 π × 1146   μ F × 0 . 009   Ω = 20 . 52   k H z
Equation 35. fP=12π×Cout×Ro
Equation 36. fP=12π×1146 μF×0.5=278 Hz
Equation 37. f R H P Z = R o u t × ( 1 - D ) 2 2 π × L P R I N p s 2 × D
Equation 38. f R H P Z = 0 . 5 × ( 1 - 0 . 33 ) 2 2 π × 9   μ H 2 . 67 2 × 0 . 33 = 86   k H z

Type IIB compensation was selected to compensate the poles and zeros of the flyback converter. Since the right half-plane zero (RHPZ) of the flyback converter is unable to be compensated, the crossover frequency of the converter needs to be between one fourth to a whole decade below the RHPZ of the converter. Type IIB compensation has 1 pole and 1 zero to help compensate the converter. Place the pole from the compensation by the RHPZ of the converter and place the zero from compensation a decade before the expected crossover frequency. Using these guidelines, the compensation values for the converter were picked for the converter. For the non-isolated portion of the board this means choosing the value of the compensation resistors and capacitors along these guidelines. This allows for the gain to be controlled in the system without changing the poles and zeros of the system. Adding an isolated feedback loop often changes how the compensation is done. Optimization is needed for compensation values, and those values can be validated through testing.