LED display just why there will be a screen and light when electricity line

LED display screen has just electricity come when you least expect them to take a few seconds and bright lines or screen flowers are the reasons? When the display control card and computer has the HUB distribution board and the screen after the connection is in order, power supply + 5 v power supply controller makes its normal work, please do not directly connected to 220 v voltage. The screen out there for a few seconds of light or screen. These are all normal, remind the user's screen is about to start work. Generally this phenomenon normal work for about 2 seconds, the screen will work properly.