BQ24780SRUYR Power Path Management: Key Technology in Charging Systems

In the charging system of multi-cell lithium battery devices, how to balance the contradiction between system power supply and battery charging is a key problem in power management. The BQ24780SRUYR launched by Texas Instruments (TI) is not only an efficient synchronous step-down charging controller, but also provides a reliable and flexible Power supply solution for modern electronic products with its intelligent Power Path Management function.

1. What Is Power Path Management?

• In conventional charging designs, system power and battery power often compete on the same path:If the battery takes priority, the system might shut down when battery capacity is low.
• If the system takes priority, the battery may charge inefficiently or not at all.

Power Path Management (PPM) addresses this issue by intelligently switching power paths to dynamically balance system and battery power. When an adapter is connected, the system draws power directly from it; any remaining current is used to charge the battery. If the adapter is removed, the system seamlessly switches to battery power.

2. How BQ24780SRUYR Enables Smart Path Management

The BQ24780SRUYR integrates a complete path management architecture with the following key elements:

1. ACFET and RBFET Control

It controls external input MOSFETs (ACFET/RBFET) to detect adapter presence and manage system connection, while also supporting hot-plug protection.

2. BATFET Control

Manages battery-side MOSFETs to connect or disconnect the battery from the system. This enables dynamic source switching based on system load requirements.

3. Dynamic Power Management (DPM)

If the adapter cannot supply enough current for both system and charging needs, BQ24780SRUYR automatically reduces the battery charging current to prioritize system stability.

4. Input Current Limiting

Via the I²C register (Input Current Limit Register, 0x3F), users can set a safe adapter current limit to prevent overloading and ensure proper path transitions.

3. Application Examples

In a laptop equipped with the BQ24780SRUYR:

• When the 90W adapter is inserted, the system consumes 45W of power, and the remaining 45W is used to charge 4 lithium batteries.
• If the user runs a high-load program and the system power consumption rises to 80W, the BQ24780SRUYR automatically reduces the battery charging current to accommodate the remaining 10W.
• After unplugging the adapter, the chip immediately switches to battery power supply, the system operates without interruption, and the user experience is smooth and imperceptible.

4. Conclusion

The smart power path management feature of the BQ24780SRUYR is a key differentiator that addresses core issues such as power distribution, load priority, and seamless source switching. It provides a stable and adaptive foundation for modern battery-powered devices.

Choosing a charger IC with built-in intelligent path management is not just a technical choice-it's a commitment to efficiency, user experience, and long-term reliability in system design.