Display module drive circuit having a digital source driver capable of generating multi-level drive voltages from a single external power source

摘要

A display module drive circuit has a gate driver and a source driver. The source driver has a shift register (1), a sampling memory (2), a hold memory (3), a timing signal generating circuit (4), a voltage control circuit (5), and an output voltage generating circuit (6) having a capacitor and a switch. The timing signal generating circuit (4) generates timing signals (T₀-T₇) having different pulse widths in each of horizontal periods. The number of the timing signals (T₀-T₇) depends on the number of density levels of an image to be displayed. Upon receipt of digital video signals (HnD₀, HnD₁, HnD₂) and the timing signals (T₀-T₇), the voltage control circuit (5) selects one of the timing signals (T₀-T₇) based on the contents of the video signals (HnD₀, HnD₁, and HnD₂) in each horizontal period and outputs a control signal (CON1, CON2) at a specified level for a period corresponding to the pulse width of the selected timing signal. The capacitor of the output voltage generating circuit (6) is charged with an external power voltage while the control signal (CON1, CON2) is being received by the switch, so that a drive voltage is generated. The external power voltage is supplied from an external power source offering an electrical potential which becomes higher with time.