There are variety ways of building 3.3V power supply, such as using voltage divider, voltage regulator and DC-DC converter.

本设计设计手机充电器系统，实现由交流220V电能到直流4.2V电能的转换，进而为手机等设备充电。在系统控制中采用了变压、整流、滤波、稳压、分压、电压检测等电路，并且具有一定的充电提示和充满电自动断电的功能。 本设计采用Proteus（V7.1）软件仿真进行演示。-Based on Proteus simulation design phone charger system, implemented by 220V AC power to DC 4.2V power conversion. I

分频器，利用quartus软件或者modelsim软件对频率进行分频，也可在硬件上观察出对信号的分频-Frequency divider, quartus software or modelsim software is used to analyse the frequency divider, can also be used on hardware to detect the signal frequency division