A method for a display driver circuit configured to drive a display panel includes steps of: determining whether a plurality of first data codes corresponding to first data voltages to be output through a multiplexer to data lines in the display panel during a first horizontal line period equal; determining whether each of the first data codes equals a corresponding second data code among a plurality of second data codes corresponding to second data voltages to be output through the multiplexer to the data lines during a second horizontal line period immediately after the first horizontal line period; and in response to that the first data codes equal and each of the first data codes equal the corresponding second data code, outputting a control signal to keep a switch of the multiplexer staying in a turn-on state after the switch is turned on for outputting a first data voltage.