How to discern a charger depends on how its work performance, safety requirements and electromagnetic compatibility is.
Different types of batteries have different charging requirements, the parameters of a charger are mainly charging method, charge current, charge voltage.
(1) Charging method: how to charge is based on the constant voltage or constant current. Given the current lithium-ion battery, charger charging current with limiting constant voltage mode shall be adopted, that is, charging at constant voltage automatically converted when the charging at limited current to the limited voltage.
(2) Charging current: specifies the maximum output current of the charger. The size of the charging current shall be applied to the size of the battery capacity, generally should not exceed 1C5A.
(3) charging voltage: specifies the maximum output voltage of charger.The charging voltage is depends on limit voltage of battery charged; when charging the lithium-ion battery with nominal voltage of 3.6V, the maximum output voltage of charger required is typically 4.2V (in fact, the phone is equipped with a lithium-ion battery with protection device, so the charger output voltage can also be slightly higher than 4.2V, but the voltage is not more than 4.5V in order to ensure safety).
2. Safety requirements
Popular terms is to ask the circuit structure, mechanical structure and electrical properties of the product shall comply with certain safety requirements, regardless of the product in a normal or abnormal operating state (such as output overload or short circuit, the internal component failure or circuit failure, etc.) work state, must not endanger the safety of persons and property. To achieve this purpose, the charger product safety requirements (such as electric shock protection performance, insulation performance, temperature, etc.) shall comply with the requirements of China mainland’s compulsory standards as specified in GB4943-2001.
3, electromagnetic compatibility
For chargers products, the electromagnetic compatibility requirements mainly reflects in electromagnetic harassment. Electromagnetic disturbance is divided into conduction harassment and radiation harassment. the many advantages of switching power supply contribute to the switching power supply circuit for universal charger. But the switching power supply of high-frequency switching devices produces high-frequency harmonic signals. These high frequency signals propagate through the power terminal via the grid or via space radiation result in the electromagnetic pollution to the environment, troubling the work around electronic devices,even may cause serious adverse effects on human health and the safe operation of the grid. Therefore, in order to reduce the electromagnetic pollution to the environment, the power terminal (or interface terminal) disturbance voltage for the electronic products working and radiation disturbance field strengths shall be less than a certain limit. For mobile phone battery charger,the disturbance voltage and disturbance field strength must comply with the requirements of the China mainland’s mandatory standards GB9254-1998 Class B limits.