SLVAFH1A December   2022  – December 2023 TPS62933 , TPS62933F , TPS62933O , TPS62933P

 

  1.   1
  2.   Create an Inverting Power Supply Using a TPS6293x Buck Converter With Internal Compensation
  3.   Trademarks
  4. 1Configuring the Buck Converter for Inverting Buck-Boost Topology Application
  5. 2Choosing the Correct Buck Converter for Inverting Power Application
    1. 2.1 Output Voltage Range
    2. 2.2 Input Voltage Range
    3. 2.3 Output Current Range
  6. 3Selecting Applicable External Components for Inverting Power Application
    1. 3.1 Resistor Divider
    2. 3.2 Inductor and Output Capacitor Selection
      1. 3.2.1 Inductor Selection
        1. 3.2.1.1 Output Current
        2. 3.2.1.2 Inductor Current Ripple
      2. 3.2.2 Output Capacitor Selection
        1. 3.2.2.1 Large Load Transient
        2. 3.2.2.2 Output Ripple Voltage
    3. 3.3 Input Capacitors
    4. 3.4 Bypass Capacitor
    5. 3.5 Enabling and Adjusting UVLO
  7. 4Experimental Results
  8. 5Summary
  9. 6References
  10. 7Revision History

3.2.1.2 Inductor Current Ripple

Considering the current ripple in the inductor, when the inductor value is too small, then the current ripple will be so large that it causes more power loss in the inductor and capacitors, and also reduces the lifetime of the components. Too large of an inductor value causes a larger size and it is not good for the power density. Usually, you can choose an applicable inductor value that lets r = 0.4, to get Equation 7.

Equation 7. ∆ I L m a x = V I N m a x × D m i n L m i n × f s ≤ 0.4 × I O U T m a x 1 - D m i n

For this example, VINmax = 16 V, VOUT = –12 V, IOUTmax = 1.2 A, and fs = 500 kHz, so Lmin = 12.5 µH.