Abstract: In a plasma display panel, an analogue brightness value given by a variable resistor is periodically converted into a digital brightness value and stored in a memory. A digital brightness value of a current period is compared with the digital brightness value of the next preceding period stored in the memory, to produce a difference brightness value which is compared with a predetermined brightness value and, if larger than the predetermined value, the brightness value stored in the memory is updated. Alternatively, power consumption of a display device is detected and, when the power consumption is larger than a set point, a brightness value is gradually decreased and, when the power consumption is smaller than the set point, the brightness value is gradually adjusted to a brightness set value.

Abstract: When a MOS transformer switch 14 shifts from an ON state to an OFF state, a fly-back spike voltage is induced from a secondary winding 122 to a primary winding 121. As a result electric charge accumulates in a capacitor 281, via a diode 283 and a voltage, i.e. is the voltage of a battery 10 on to which the voltage between terminals of the capacitor 281 is stacked, is supplied to the DC power-supply voltage input terminal Vcc of a control circuit 16 via a LC low pass filter 34A. Energy stored in the capacitor 281 may be effectively utilized, while the fly-back spike voltage to the control circuit 16 side is cut by a LC low pass filter 34A.