How TP4056 Li-Ion Charger Circuit Works
Lithium-ion batteries power nearly all our portable electronics and safely charging them is crucial. The TP4056 is a popular, robust, and affordable chip for this task. Understanding its circuit is a fundamental step for anyone building battery-powered projects. Let's explore how a typical TP4056 charger circuit functions, from charging your battery to protecting it.What This Circuit Does
This circuit provides a complete solution for charging a single-cell (3.7V nominal) Li-Ion battery and protecting it from common hazards like overcharge, over-discharge, and over-current. It takes a standard 5V USB input and delivers a regulated charging current to the battery, while also offering a protected output for your device.
Key Components Explained
A few integrated circuits and passive components work in harmony to make this charger reliable.TP4056 Li-Ion Charger (U7)
This is the heart of our charger. The TP4056 (U7) is a complete constant-current/constant-voltage (CC/CV) linear charger for single-cell lithium-ion batteries. It takes 5V power from the USB+ and USB- inputs (Pin 4 VCC and Pin 3 GND). Its charging current is set by a resistor connected to the PROG pin (Pin 2). In this circuit, R13 (1.2k) is connected to PROG, setting the charge current to approximately 1 Ampere. The BAT pin (Pin 5) connects directly to the battery's positive terminal. The CHRG (Pin 7) and STDBY (Pin 6) pins drive indicator LEDs, showing whether the battery is actively charging or fully charged/in standby. The CE (Pin 8) pin is connected to USB+, keeping the charger always enabled. The EP (Pin 9), typically a ground connection for thermal dissipation, is shown connected to the input positive rail in this schematic.
Battery Protection (U6 DW01S & Q3 FS8205A)
Safety is paramount with Li-Ion batteries. This circuit includes dedicated protection using the DW01S (U6) and FS8205A (Q3).- DW01S (U6): This IC monitors the battery's voltage and current. It connects to the battery's positive (VDD, Pin 5) and negative (VSS, Pin 6) terminals to detect overcharge and over-discharge conditions. It also monitors current via the CSI (Pin 2) pin in conjunction with the FS8205A.
- FS8205A (Q3): This is a dual N-channel MOSFET package. It acts as a switch in the battery's negative current path. The DW01S controls the gates (G1, G2) of these MOSFETs. If a fault condition (overcharge, over-discharge, over-current) is detected, the DW01S turns off the appropriate MOSFET, disconnecting the battery from the charger or the load.
Supporting Cast: Resistors and Capacitors
- R13 (1.2k): Programs the TP4056's charging current.
- R11 (1k) & R12 (1k): Current-limiting resistors for LED3 (charging indicator) and LED4 (charge complete indicator).
- R14 (1k): Connects the common drain of FS8205A to the CSI pin of DW01S, crucial for current sensing.
- R15 (100): A series resistor between B+ and OUT+, providing some output protection or stability.
- C1 (0.1uF) & C2 (0.1uF): Decoupling capacitors that filter noise on the input and for the DW01S, ensuring stable operation.
- C3 (10uF): An output capacitor that smooths the battery voltage for the connected load.
Step-by-Step Operation
Powering Up and Charging
When you connect a 5V USB power source to the USB+ and USB- terminals, power flows to the TP4056. If a discharged Li-Ion battery is connected to the B+ and B- terminals, the TP4056 initiates charging. It first charges at a constant current, determined by R13 (around 1A in this circuit). During this phase, LED3 (the charging indicator) lights up. As the battery voltage approaches its full charge (4.2V), the TP4056 transitions to constant voltage mode, gradually reducing the charging current. Once the current drops below a certain threshold, the battery is considered fully charged. LED3 turns off, and LED4 (charge complete indicator) lights up.
The Role of Protection
The DW01S(battery protection IC) and FS8205A (dual N-channel enhancement mode power MOSFET IC) continuously monitor the battery. If the battery voltage exceeds 4.25V (overcharge), the DW01S turns off the charging MOSFET within the FS8205A, preventing further current from entering the battery. If the battery voltage drops below 2.4V (over-discharge), the DW01S turns off the discharging MOSFET, preventing the battery from being damaged by deep discharge. The DW01S also detects over-current by monitoring the voltage drop across the FS8205A MOSFETs (with the help of R14) and will disconnect the battery if the load draws too much current, protecting against shorts or excessive power draw. This integrated protection is vital for the longevity and safety of your Li-Ion battery.Practical Applications
The TP4056 charger is a cornerstone for many DIY electronics projects requiring portable power. I’ve personally used this charger with my Arduino-based Bluetooth RC car to keep its battery topped up. Learning which pin does what was made much faster using the TP4056 Chip Pinout Explorer, which greatly aided in circuit design and troubleshooting. Next, I plan to integrate it to power my Bluepill board for various IoT applications, demonstrating its versatility across different embedded systems.
This simple yet effective circuit ensures your Li-Ion batteries are charged safely and efficiently, making it an indispensable tool in your electronics toolkit. Now that you understand its workings, you can confidently integrate it into your next battery-powered creation!
