Lithium-ion Battery Charger Switch-mode

Introduction

Lithium-ion Battery Charger using Switch-mode technology is the ideal choice for powering up devices quickly, safely, and efficiently. Unlike standard linear charging methods, switch-mode charging uses a control circuit to more accurately control the amount of current going into the Battery Pack, reducing peak input power and maximizing energy efficiency. This revolutionary charging method also cuts down on charge time—sometimes by as much as 50%—allowing you to get back to what you were doing faster than ever before. With cutting-edge technology like this on your side, you never have to worry about running out of device power when you need it most.

Circuit Diagram

of Lithium-ion Battery Charger Switch-mode

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Working Explanation

of Lithium-ion Battery Charger Switch-mode

Lithium-ion batteries are being used more and more frequently in all kinds of appliances. These batteries require a charger for which Maxim's MAX745 is ideal. This battery charger provides all the necessary functions required to recharge such batteries. Upto 4 amperes regulated charging current is provided by this circuit without getting hot.

The per-cell battery voltage regulation limit is set between 4.0 V and 4.4 V using standard 1% resistors, and then the number of cells is set from 1 to 4 by pin strapping. Less than ±0.75% is the total output voltage error.

The charger is available as an evaluation kit, which is an assembled and tested printed-circuit board that implements a step-down, switching power supply designed for charging lithium-ion (Li-ion) batteries. Between 4.0 Volts and 4.4 Volts, the cell voltage can be set.

The Li-ion battery pack is connected between BATT and GND (BATT is positive, GND is negative). The battery may be connected with the charger off without causing damage, or it can be connected after power is applied.

The charging voltage is determined by the potential at junction R3-R9. Replacing these resistors by a multiturn potentiometer enables the voltage to be set very accurately.

The charging current is selected with jumper JP3. Here also, a multiturn potentiometer to replace R5 and Rg enables a more accurate setting.

The number of cells, and thus the charging voltage, is set with jumpers JP1‚ and JP2: both to ground for one cell, only JP2 to VL for two cells, only JP1‚ to VL for three cells, both to VL for four cells.

Switch S1‚ may be replaced by a resistor with a negative temperature coefficient (NTC). When the voltage at pin THM drops below 2.1 V, the circuit is switched off automatically; when the voltage reaches 2.3 V again, the circuit is switched on anew.

Transistor T1‚ is an n-channel FET whose auxiliary gate voltage is derived from capacitor C7.

Diode D1‚ is a freewheeling diode in case T1‚ is cut off. When this happens, the diode is shunted by T2 (which is on) to improve efficiency. This is because the drop across the diode is 0.3-0.4 V, whereas that across a conducting transistor is only 0.1 V.

The three Schottky diodes are fast 3 A, and 40 V types from Motorola. The FETs may be part of a dual FET from International Rectifier. If discrete ones are used, in view of the switching frequency of 300 kHz, types with a high input capacity must not be used: there is a current of only about 20 mA available for driving the gates. The IRF7303 has parameters: 30 V, 5 A, 0.05 ohm, and 520 pF.

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Conclusion

Lithium-ion battery charger switch-mode technology is the most common method of charging Li-ion batteries. This type of charger is known for being efficient, reliable, and cost-effective. Its switch-mode design allows it to precisely control the charging parameters, providing a steady charge rate that won’t overcharge or damage your battery. It also has safety features such as surge protection and temperature sensing to ensure optimal performance. Finally, its small size and lightweight design make it an ideal option for use with portable devices or in tight spaces. With its numerous advantages, it's no wonder why lithium-ion battery charger switch-mode technology is so widely used.