Battery ChargerLCD-LED Display

Lithium Battery Charger using BQ24103 Schematic Circuit Diagram

The BQ24013 serves as a user-friendly charge controller compatible with lithium-ion and lithium-polymer batteries. One of its notable features is the integrated power MOSFETs, capable of handling charge currents up to 2 A. Its high switching frequency of 1.1 MHz reduces the need for a large external coil, enhancing efficiency significantly compared to linear charging circuits. Another advantage is its ability to charge both single-cell and two-cell series-wired battery packs.

The charging status is indicated by two LEDs: D1 lights up during charging, and D2 signals when the battery is fully charged. The charge current can be configured using external resistors, allowing adjustment of three currents: the initial (precharge) current, the main charge current, and the charge termination current. In the provided configuration, the precharge current is 67 mA, the charge current is 667 mA, and the termination current is also set at 67 mA.

Lithium Battery Charger using BQ24103 Schematic Circuit Diagram

Charging Process Integrity: IC Safeguards and Voltage Limitation

The IC plays a crucial role in ensuring the proper charging process, especially in preventing the lithium chemistry cell from exceeding its maximum permissible voltage. This limitation is vital for the safety of lithium cells.

Jumper Configuration: Critical Precaution for Single and Double Cell Charging

Attention must be given to jumper JP1, which should only be installed when charging two cells. When charging a single cell, the jumper must remain absent; failure to remove it could result in a dangerous situation involving explosion or fire due to an excessively high charging voltage.

Supply Voltage Considerations: Single Cell vs. Dual Cell Charging

For single-cell charging, the minimum required supply voltage is 5 V, while for charging two cells, it should not drop below 9 V. The IC’s datasheet specifies its operational range up to 16 V.

IC Packaging and Prototype Design: Challenges and Benefits

The IC is unfortunately available solely in a QFN20 package, which poses challenges during soldering. However, the compact nature of this package allows the construction of a complete 2 A charging circuit within a minimal area of 2.5 cm² on the printed circuit board, providing a significant advantage in terms of size efficiency.

Component Selection and Considerations: Inductor, Resistor, and Capacitor Choices

For the prototype, a 4.7 μH inductor with a DC resistance (DCR) of 0.082 Ω (82 mΩ) and a current rating (DCI) of 1.72 A was selected for L1 with a charging current of 670 mA. If aiming for a charge current of up to 2 A, an inductor with a DCR lower than 0.025 Ω (25 mΩ) and a current rating of 4 A or more is recommended.

A Vishay 150 mΩ SMD resistor in an 0805 package (available from suppliers like Farnell) was used for R5. As for C3, a ceramic barrier-layer capacitor with a working voltage of 25 V was chosen. If an electrolytic capacitor is utilized, it must have an extremely low equivalent series resistance (ESR).

IC Variants and Prototype Choice: Optimal Selection for BQ24103A

Various versions of the IC are available, each with distinct specifications. For this prototype, the BQ24103A variant was employed, providing specific functionalities tailored to the project’s requirements. Comprehensive information about the available IC versions can be found at the provided link [2].

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