A light source driving device includes a resolution analyzing part, a dimming block adjusting part, a local dimming part and a light source unit. The resolution analyzing part obtains an image resolution. The dimming block adjusting part adjusts the size or the number of dimming blocks generating light in a local dimming method in response to the resolution. The local dimming part generates a local dimming signal for individually driving the dimming blocks in response to the image data and the size or the number of dimming blocks. The light source unit is driven by the local dimming signal to generate light. The size or the number of the dimming blocks is adjusted to be optimized for the obtained image resolution, so that regardless of the image resolution, a local dimming signal corresponding to the size and the number of the dimming blocks may be generated.