For the car DVR, the first thing to do is to narrow the dynamic voltage and current. How to ensure the normal operation of the on-board DVR, stable voltage and current are very important, but on the other hand, the input power of the device is fixed. It can be known from W=U*I that the current is also changing when the voltage changes. The direction of current change is always the opposite. So if the starting voltage is made lower, the relative starting current will increase. The macro is so simple, but it can do this function stably and ensure the normal operation of the equipment. It takes a lot of work. The first thing to do is to protect the circuit design. You must know that the power supply board of the car DVR has to be within 1 hour. After experiencing hundreds of impacts, the protection circuit is not doing well, but the power board is damaged, and the board is burned directly by the power board.