An inverter unit including a converter, a transformer, a feedback circuit and an open lamp lock circuit is provided. The converter receives a drive signal, and outputs a duty voltage signal accordingly. The transformer is selectively coupled with a lamp of a display panel module, and receives the duty voltage signal. When the transformer is coupled with the lamp, the transformer outputs an output voltage to the lamp according to the duty voltage signal to light up the lamp. The feedback circuit receives a feedback signal from the lamp, and outputs a feedback voltage signal accordingly. The open lamp lock circuit is coupled with the feedback circuit, receives a control signal, selectively receives the feedback voltage signal, and disables the drive signal selectively according to the feedback voltage signal and the control signal.