本发明揭露了一种用于终端的充电系统、充电方法以及电源适配器，其中，充电系统包括电源适配器和终端，电源适配器包括：第一整流单元、开关单元、变压器、第二整流单元、第一充电界面、采样单元、控制单元，控制单元输出控制信号至开关单元，并根据采样单元采样的电压采样值和/或电流采样值对控制信号的占空比进行调节，以使第二整流单元输出的第三脉动波形的电压满足充电需求；终端包括第二充电界面和电池，第二充电界面与电池相连，当第二充电界面与第一充电界面连接时，第二充电界面将第三脉动波形的电压加载至电池，使得电源适配器输出的脉动波形的电压直接加载至电池，从而可以实现电源适配器的小型化、低成本，提高电池的使用寿命。

The present disclosure provides a system and a method for charging a terminal and a power adapter. The system includes a power adapter and a terminal. The power adapter includes a first rectifier unit, a switch unit, a transformer, a second rectifier unit, a first charging interface, a sampling unit, and a control unit. The control unit is configured to output a control signal to the switch unit and to adjust a duty ratio of the control signal according to a voltage sampling value and/or a current sampling value sampled by the sampling unit so that voltage of a third ripple waveform outputted by the second rectifier unit satisfies charging demands. The terminal includes a second charging interface and a battery. The second charging interface is coupled to the battery. When the second charging interface is coupled to the first charging interface, the second charging interface loads the voltage of the third ripple waveform to the battery, so that voltage of a ripple waveform outputted by the power adapter is directly supplied to the battery, thereby realizing miniaturization and low cost of the power adapter and improving the service life of the battery.