After optimization of structural solution ， I must prepare the bom and drawing circuit diagram as soon as possible.
1 selection the suitable components.
At first，The power circuits core component is LNk 306 and LDO, I must find the datasheet and typical circuit. and compare the components lib of our company.as shown in the following figure. input 100-250V AC power (wide voltage input) , The diode is protect the circuit， The output is 12V @ 200mA （ test the voltage was stable ）
In addition ，Mcu power is 3.3V ，so we need a DC-DC buck IC ，I choice LDO ，becase it‘s very affordable and useful，as we know，In traditional design，we also use 7805 and 7803， But our products are powered by batteries for 3.3V，and we use a ups circuits to switching power supply automatic.the LDO output power drop is superior to 7805。
2 Drawing circuits
I use the Altium designer ， as we know ， Set up the schematic library ，here will not carefully described。