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

4.1 Test Waveform

According to the experimental test and analysis in the Section 3, , it's recommended to choose lower AVIN, lower VOUT and higher inductance, to achieve ultra low VIN start-up. However, AVIN should be higher than UVLO, which means the minimum AVIN is 0.7 V. To keep the ton from reaching ton_max， inductance of 1.5 uH or 2 uH is recommended. Considering all the above analysis, a typical solution is proposed to achieve extremely low voltage startup, as is shown in Table 4-1. The corresponding schematic is shown in Figure 2-2. The specific solution reference design is as follows:

Table 4-1 Design Parameters
PARAMETERS VALUES
PVIN (SW) 80 mV
AVIN (VIN) 0.7 V
VOUT 3.3 V
L 1.5 uH or 2.2 uH
R1 0 Ω
C1 10 uF
C2 10 uF
LOAD OPEN

The start up process is shown in Figure 4-1.

GUID-20230823-SS0I-LK8F-BPFN-NQCLCRLXNNS6-low.svg Figure 4-1 80 mV PVIN Start-up Waveform

In conclusion, an ultra low-power input solution using BOOST converter TPS61299 is proposed and verified in this paper. And to optimize the start-up process, elements such as AVIN, VOUT and L are studied about how they influence the start-up. Finally, considering the practical inductance, and expected VOUT, a optimized solution with lower PVIN application is recommended and verified.