SLUAAO7 March   2023 BQ24640 , BQ25173 , BQ25713 , BQ25798

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Supercapacitors Charging Key Care-Abouts and Implementations
    1. 2.1 Supercap Charge Profile
    2. 2.2 Linear Based Supercap Charger
    3. 2.3 Switch-Mode Buck Converter Based Supercap Charger
    4. 2.4 Modifying Li-ion Chargers to Charge Supercaps
    5. 2.5 Using a Li-ion Buck-Boost Integrate FET Charger to Charge a Supercap or Li-ion Battery
    6. 2.6 Using a Buck-Boost Controller with External FETs to Charge a Supercap
  5. 3Summary
  6. 4References

1 Introduction

Most super capacitors (supercaps) can be discharged down to 0 V and recharged to their maximum voltage with the manufacturer recommended charge current. A simple voltage regulating LED driver with constant current, usually regulated by sensing a low side, series current sense resistor, then a voltage clamp can be used to charge a super capacitor. However, using a dedicated charging IC that provides both output voltage and current regulation, as well as input power regulation, temperature sensing, thermal regulation and other safety features allows for more precise and safer charging. Also, there is no series sense resistor creating an undesirable voltage drop, especially during discharge. This application note provides a design for charging supercaps using either dedicated supercap chargers or simple modifications to Li-ion battery chargers.