SLAAEH7 February   2024 MSPM0L1306

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 System Description
    2. 1.2 Design 1: High Efficiency Design with 50kHz
    3. 1.3 Design 2: Space Optimized Design with 250kHz
    4. 1.4 Design 3: MCU Driven Design with Flexible Switching Frequency
      1. 1.4.1 Selection of MOSFETs
      2. 1.4.2 Efficiency Test
        1. 1.4.2.1 Current Consumption of PWM (Ipwm) Test
        2. 1.4.2.2 Efficiency Test Set Up
        3. 1.4.2.3 Efficiency Test Results at 50kHz Switching Frequency
        4. 1.4.2.4 Efficiency Test Results at 250kHz Switching Frequency
  5. 2Design File
    1. 2.1 Schematics
    2. 2.2 Bill of Materials
  6. 3Summary
  7. 4References

1.3 Design 2: Space Optimized Design with 250kHz

Design 2 focuses on optimizing the board space by reducing the size of the transformer, Table 1-1 outlines the comparison of two transformers on different features. Design 2 and design 3 (with high switching frequency) use a customized smaller size transformer with 9.60 x 5.51 x 4.83mm3.

Table 1-1 Comparison of Transformer Specifications
Turns Ratio (NP:NS) Magnetizing Inductance Lm (mH) V-t Product (V-μs) Isolation (VAC, 1 Minute) Dimensions (mm3) Operating Temperature Range (°C) Manufacturer
Design 1 1:1.25 > 3 100 1500 9.78 × 9.14 × 10.54 –40 to 100 WURTH ELEKTRONIK
Design 2, 3 1:1.5 >0.6 10 800 9.60 x 5.51 x 4.83 –40 to 100 WURTH ELEKTRONIK

Figure 2-11 shows the detailed schematic of design 2, in order to use a smaller size transformer, the switching frequency has to be increased. This can be realized by using TPS60403 with a frequency of 250kHz. In this design, power consumption of charge pump is higher due to higher switching frequency. As a result, design 2 will be slightly less efficient than design 1. However, it can still achieve more than 80% efficiency with 3.6V input and nearly 70% efficiency with 1.8V input.

GUID-20240102-SS0I-1CL0-RBHB-KJTXJ8G685GZ-low.svg Figure 1-2 Schematic of Design 2