A display device according to the present invention includes a switching regulator control circuit formed of TFTs. A digital switching regulator control circuit is composed of an AD converter circuit, a CPU, a pulse generation circuit or the like. An analog switching regulator control circuit is composed of an error amplifier circuit, a triangle wave generation circuit, a PWM comparator or the like. By integrally forming the switching regulator control circuit on a display device, the problem of the conventional portable information equipment as to the reduction in size and weight can be solved.