TP4056 3.7V Lithium Battery Charger Circuit

The TP4056 battery charger is designed to safely and efficiently charge a single rechargeable 3.7V lithium battery. The circuit board can operate with a DC 5V 1A input and can be powered by a smartphone charger's USB mini cable. It charges Li-Ion/Li-Pol batteries to their nominal voltage of 4.2V with a steady current (programmable) of 1000mA while continuously monitoring the voltage level for Battery Overcharge protection.

Two different color LEDs are included on the TP4056 circuit board to indicate the charging status. The red LED light during the charging process and automatically switches to blue LED light when the lithium battery is fully charged. The circuit is available with or without Battery Short-circuit protection feature.

Here, we will discuss and explain the workings of this 3V7 lithium battery charger along with its circuit diagram.

Circuit Diagram

Schematic of tp4056 3.7v lithium battery charger without short-circuit protection is shown below.

Working Explanation

The working principle of the TP4056 3.7V lithium battery charger circuit is simple, and the main component is an intregrated circuit TP4056E SOP8.

• Download/View: TP4056 Datasheet - NanJing Top Power ASIC Corp.

The positive input DC supply voltage powers the TP4056 IC (U1) through the Vin pin, where the ceramic capacitor (C1) filters incoming noise.

When the IC (U1) senses a connected Lithium Ion/Pol battery with a voltage less than 4.2V at the BAT pin, it initially turns on the input CE pin.

The input voltage (usually 5V to 8V) passes through the CE pin, and the internal circuit of the IC regulates it to a fixed 4.2V. The constant current is achieved by connecting a programmable resistor (R3) from the IC's PROG pin to GND, setting the charge current at 1 Amp.

As a result, the device begins charging the battery through the BAT pin. Simultaneously, the CHRG pin turns on, and the LED (D1) emits red light. A ceramic capacitor (C2) further filters any remaining noise from the charging output.

The programmable resistor can be replaced with different resistor values, affecting the charging current. To program it with a resistor value, use the formula below:

I_BAT = (V_PROG / R_PROG) x 1200

[Where, I_BAT is the battery charging current, V_PROG is a constant reference voltage of 1V, R_PROG is the resistor value, and 1200 is the maximum input current in milliampere of the IC TP4056.]

During the charging process, the IC's body pin EP generates some heat, which is typically normal. Additionally, the IC features overtemperature protection, but it is disabled by default, with the TEMP pin grounded.

Again, when the battery is fully charged (i.e., at 4.2V) or when there's no load, the IC (U1) turns off the input CE pin and activates the STDBY pin to indicate that the battery is fully charged by emitting a blue light from LED (D2).

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