Lithium-ion battery charger design requirements
Effect of lithium ion battery safety and effective charging voltage, current and temperature, so chargers to take care of a good control in the design of these three factors.
In accordance with the above request, the charger IC active power path management, the power path management requirements in the load the load current/under unloaded conditions, real time adjustment of lithium-ion battery charging current, effective supervision and management in accordance with USB-IF current limit and soft activation function required by the specification. IC integration within the temperature monitoring function, if IC temperature exceeds the limit value, automatically reduces the charge current. Charger power adapter ensure that 5V DC power supply can charge pressure steady flow, if one has a current, maximum charging current can be set with an external resistor control to avoid USB overload.
Charger also has captive power path management capabilities, when system-side electricity when they exceed the input power supplies constraints; ensure the initiative to activate the discharge function of lithium-ion batteries, while system-side needed to supply its power. Charger consumes minimal battery is lower than 3V, IC inside to set the charging current should be 10% preset current.
Suitable temperature for charging li ion battery are 0~45℃,If the 0.5℃ charging, you can 1℃ Temperature rise as 90℃, charger operates on 35℃ environment temperature, best for lithium batteries, so 2 hour rate charged the current best.
The fundamental problem is that when charging when the charging temperature is too high, therefore, the design must balance between charge current and thermal bodies, due to the portable charger portable products that apply to light. Use the low thermal conductivity of the plastic casing, regardless of the metal fins, finally, reduce the charging current or prolong the charging time of a way to achieve lower operating temperature.
Therefore, the general lithium-ion battery charger for 1500mAh following capacity lithium battery, and for high-voltage, high-capacity lithium-ion battery, you use synchronous switching charger.
After the design of lithium-ion battery charger charging process is divided into three phases:
1.And charging IC to detect whether there is a short circuit or output overload protection mode, such as normal, and then see if battery voltage is 3V , Above 3V Constant current charging direct access below 3V , Then the constant-current 10% the pre charge current;
2. Fast, constant-current charge State: height up to 4.2V;
3.And constant pressure stage: batteries up to 4.2V, voltage no longer increase charge current showed a declining trend until it reaches a constant current of 10% Stop charging.
Future lithium battery charger will provide faster, safer and more comprehensive charging management system.
Company: Dongguan Large Electronics Co., Ltd
Add: Block A, Gaosheng Technology Zone, Nancheng District, Dongguan City, Guangdong Province, CN