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

1.4 Test Setup

To avoid mistakes that can lead to unwanted behavior of this SEPIC charger (like setting a current limit threshold on this board less than the constant-current sink set to your electronic load), please observe the following procedure during testing:

  1. Supply the board with the bench PSU (Vin) on J1 (pin 1 positive)
  2. Connect a constant current load to the output on J2 (positive on pin 2)
  3. If this power supply is used as standard PSU (therefore not charging a battery) set “Mode select” on J3 by placing a jumper between pins 1 and 2 (Forced PWM)
  4. Please use “diode emulation mode” as the battery charger
  5. Set the constant current setpoint (ILOAD) of the load to 0.1 A
  6. Set VIN to 24 V and the current limit to 1 A
  7. Turn on VIN and check the output voltage
  8. Rotate the trimmer R22 (VOUT Adjust) so that VOUT is 26 V
  9. If the output voltage does not reach 26 V, then R30 is set to very low current; in this case rotate R30 until VOUT increases. As VOUT increases, then rotate R22 to reach 26 V
  10. Now increase the current limit of the bench PSU Vin to 8 A
  11. Change the electronic load into “constant voltage” and set the voltage at 24 V
  12. At this point the output current is dependent on the position of R30, while VOUT is fixed by the load to 24 V
  13. Now rotate R30 until the output current is 2 A
  14. Start measuring the standard parameters as desired, versus output current
  15. Please remember that if you are using this charger with a battery, the converter must be set in “diode emulation mode” by moving the jumper over J3 from pins 1-2 to 2-3; in this case keep the diode emulation mode always on