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Choosing between different charging topologies

Perico Eldelospalotes
Intellectual 505 points

Hi!

The two main topologies of battery chargers with power path included are:

1.- Regulator (LDO or Buck) connected directly to the system and battery.

2.- Regulator connected to the battery and a path via external transistors connects the input power source directly to the system. Battery is attached to the system only when no input source is connected.

Somebody could tell me the main advantages and disadvantages of these 2 options? I need to choose a battery charger and I am not sure which topology to choose. Please, ignore the battery chemistry, capacity, charging current, etc, as the important thing for me now is which topology to choose based on the advantages and disadvantages of each one.

Thank you in advance!!

  • 0
    TI__Expert 7730 points

    The second topology has two main advantages:

    1. The system can instant turn on once the input adaptor is applied and doesn't need to wait for the depleted battery to be charged.

    2. The battery charging current can be measured separately from the current that goes to the system load. This is useful when you want to accurately control when you want to terminate the charging.

    One obvious advantage of this is the external FET adds extra size and cost. However, we do have chargers that employ the second topology yet eliminate the needs for the external FET by integrating the FET inside the chip. Please specify your needs on current level, preference on linear/switch mode, etc for further recommendation.

    Thanks,

    Wenjia