Display device, controlling method thereof and driving device for display panel

A display device, comprising:

• a main display panel;
• a main driving unit for driving the main display panel, the main driving unit comprising a first driving voltage generating unit operative to generate a plurality of first driving voltages to be supplied to the main display panel and a first driving voltage terminal that outputs the first driving voltages;
• a sub display-panel;
• a sub-driving unit for driving the sub display panel, the sub driving unit comprising a second driving voltage generating unit for generating a plurality of second driving voltages, a source power terminal for receiving source power, a second driving voltage terminal that outputs the second driving voltages, and a switching unit adapted to switch the source power supplied from the source power terminal to the second driving voltage generating unit;
• and
• a controller coupled to the switching unit, the controller being operative to instruct the switching unit to switch off the source power to the second driving power generating unit if the main display panel is in a standby mode in which an image is not displayed on the main display panel.