SLVAFL5 September   2023 TPS61299

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction of Water Heater
  5. 2Low Voltage Start-up Boost Converter Introduction
    1. 2.1 General Introduction About TPS61299
    2. 2.2 Introduction about Traditional Start-up Process
    3. 2.3 Down Mode and Boost Mode Operation
  6. 3TPS61299 Ultra-low Voltage Start-up Design
    1. 3.1 Ultra Low Voltage Start-up Set up
    2. 3.2 The Way AVIN influence Start-up Process
    3. 3.3 The Way Vout Influence Start-up Process
    4. 3.4 The Way L Influence Start-up process
      1. 3.4.1 Why With the Larger Inductance, The Smaller PVIN Start-up Can Be Achieved?
      2. 3.4.2 Why Does The Inductance Continue to Increase, The Minimum PVIN to Start Up Is Not Lower
      3. 3.4.3 Why 80 mV Can Start Normally While 70 mV Fail to?
  7. 4Ultra-low Voltage Start-up Design
    1. 4.1 Test Waveform
  8. 5Summary
  9. 6References

3.4.3 Why 80 mV Can Start Normally While 70 mV Fail to?

Figure 3-8 and Figure 3-9 are the test waveforms when L=2.2 uH, AVIN=0.7 V, VOUT Target =3.3 V, and PVIN are 70 mV and 80 mV respectively. Figure 3-8, shows that PVIN=70 mV, and the output has not been raised to the target voltage.

GUID-20230828-SS0I-FVFM-0B28-W8L5HJQGHWLZ-low.pngFigure 3-8 PVIN=70 mV (VOUT=2.0 V, Fail to Start up)
GUID-20230828-SS0I-PGVP-9KT6-NDFTFT2ZQR5P-low.pngFigure 3-9 PVIN=80 mV (VOUT=3.3 V)

Inductor current under different PVIN are shown in Figure 3-10. When PVIN is only 70 mV, the input power signal is already quite weak, so when Ton_max is reached, the electric energy stored in the Ton stage is only enough to raise the output to 2.0 V, as is shown in Figure 3-10. When PVIN=80 mV, the power input is also relatively weak, But it can ensure that before Ton_max, the device can ensure that the electric energy storage is enough to raise the output to 3.3 V.

GUID-20230823-SS0I-CKPC-27F5-RZ6SNK48CWRQ-low.svg Figure 3-10 Inductor Current Curves for Different PVIN