TIDT403 August   2024

 

  1.   1
  2.   Description
  3.   Features
  4.   Applications
  5. 1Test Prerequisites
    1. 1.1 Voltage and Current Requirements
    2. 1.2 Required Equipment
    3. 1.3 Considerations
    4. 1.4 Dimensions
  6. 2Testing and Results
    1. 2.1 Efficiency Graphs
    2. 2.2 Efficiency Data
    3. 2.3 Thermal Performance
    4. 2.4 Bode Plots
    5. 2.5 Light Load Efficiency Optimization
    6. 2.6 Switching Frequency Choice
  7. 3Waveforms
    1. 3.1 Switching
    2. 3.2 Output Voltage Ripple
    3. 3.3 Overcurrent Protection
    4. 3.4 Load Transients
    5. 3.5 Turn ON and OFF
  8. 4References
  9.   Trademarks

2.5 Light Load Efficiency Optimization

Considering the converter is working in synchronous rectification status, the light load efficiency is very low. There are two options we can adopt to optimize the load. One option is decreasing the switching frequency and another option is burst mode. Of course, we also can combine the two options into one. As shown in Table 2-9, decreasing the switching frequency at light load contributes to higher efficiency with maximum 4% efficiency promotion.

Table 2-9 Light Load Efficiency at 400Vin, 9Vout

Vin (V)

Vout (V)

 Load (A) Switching

Frequency (kHz)

 Efficiency

Optimized

 Efficiency

Before

400

9

20

133.7

86.67%

82.92%

400

9

40

133.7

91.88%

89.85%

400

9

60

179.2

92.82%

92.21%

400

9

80

179.2

93.63%

93.09%

400

9

100

200

93.43%

93.38%

Light load efficiency image is shown in Figure 2-13.

PMP41078 Light Load Efficiency at 400Vin, 9VoutFigure 2-13 Light Load Efficiency at 400Vin, 9Vout