TIDT377 December   2023

 

  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 Dimensions
    4. 1.4 Test Setup
  6. 2Testing and Results
    1. 2.1 Efficiency Graph
    2. 2.2 Thermal Images
    3. 2.3 Bode Plots
      1. 2.3.1 Bode Plot With Battery
        1. 2.3.1.1 Bode Plot With Battery During Recharging Phase (Constant Current)
        2. 2.3.1.2 Bode Plot With Battery at Constant Battery Voltage
      2. 2.3.2 Bode Plot With Electronic Load
  7. 3Waveforms
    1. 3.1 Switching
      1. 3.1.1 Transistor Q2 Drain to Source
        1. 3.1.1.1 9-V Input Voltage
        2. 3.1.1.2 36-V Input Voltage
      2. 3.1.2 Transistor Q1 Source to Drain
        1. 3.1.2.1 9-V Input Voltage
        2. 3.1.2.2 36-V Input Voltage
    2. 3.2 Output Voltage Ripple
    3. 3.3 Load Transients
    4. 3.4 Start-Up Sequence
    5. 3.5 Shutdown Sequence

Description

This reference design shows the use of a Buck-Boost capability of a single-ended primary-inductor converter (SEPIC) converter. Since the input and output are separated by a capacitor, this topology can be used to charge a battery with variable VIN as well as variable VOUT. A synchronous peak-current mode controller LM5122 is employed; this IC can drive the high-side sync-FET by means of level shift (RCD network). By applying 9-V to 36-V input, this board can be used to charge two batteries in series with a voltage range of 8 V to 28 V, up to 2-A charging current, or simply used as standard constant-voltage power supply. Both setpoints of output voltage and current are defined by means of two trimmers, even though both references can also be replaced by employing two digital-to-analog converters.