A circuit for driving an AC TFEL device which is a complete solid luminescence element, capable of generating positive and negative AC voltages from a single DC voltage by utilizing a relative potential difference and thereby providing a compact voltage supply unit required for driving the AC TFEL device. A circuit is also provided which is constructed to reduce the number of operating voltages required in the refresh drive method and the scan inversion symmetric drive method upon driving the matrix of the AC TFEL device by using a relative potential generating circuit. By employing such a circuit, it is possible to simply provide a voltage supply circuit required in a portable display system using the AC TFEL device and supply a voltage required for the refresh driving and the scanning sequence inversion driving by using only one clock control signal.

Disclosed is a display device for detecting working load of a CPU which includes a resistor having a low resistance connected in series between a power supply and the CPU. The voltage drop across the resistor is amplified by a differential amplifier. The amplified voltage is converted into digital signal by means of an A/D converter. A plurality of LEDs are driven by the digital signal to responsively show the working load state of the CPU.

The present invention relates to a method, load (12) and display device (10) where an output parameter value (V) of a power supply (14) coupled to a separate load (12) is regulated. The load (12) demands at least one such parameter value (V) from the power supply (14). The power supply (14) delivers the output parameter value (V) to the load (12). The load (12) comprises a control signal setting unit (16), which receives information relating to the output parameter value (V) and is connected to the power supply (14) for delivering a control signal (VC). The control signal (VC) includes information relating to the output parameter value (V) and is used by the power supply (14) for regulating the output parameter value (V). This makes the control signal setting unit (16) part of a feedback loop. The parameter value is preferably an output voltage, the load a plasma display panel and the display device a television set.

Energizing an active matrix electroluminescent device with a generally sinusoidal illumination waveform causes the electroluminescent layer to emit light. A sinusoidal waveform minimizes the peak currents reducing the likelihood of burnouts and decreases the imposed voltages on the data lines increasing the likelihood that the high voltage transistors will function as intended. Preferably, the sinusoidal waveform is generated by using a single 12 volt power source which reduces the expense, weight and bulk of the electroluminescent device. The 12 volt power source may be used to operate an operational amplifier that receives a small sinusoidal input signal and produces a low voltage generally sinusoidal waveform that is amplified by a step-up transformer for energizing the transparent electrode layer of the device so as to cause the electroluminescent layer to emit light. Furthermore, the use of a generally low voltage operational amplifier permits the routing of a 12 volt power signal from a remote power source, such as a battery, to a head-mounted active matrix electroluminescent device, reducing safety concerns routing of high voltage signals near the body of the user.

The present invention relates to a method and apparatus for driving an AC-excited thin-film electroluminescent display based on a display matrix of rows and columns, in which method each row of the display matrix is alternately driven by positive (Vwrp) and negative (Vwrn) row drive pulses in which the magnitudes of successive pulses are different, each column of the display matrix is driven individually by modulation voltage pulses synchronized to the row addressing sequence, said pulses having a maximum amplitude (Vm) and an "ON"-state polarity equal to that of the larger-magnitude row drive pulse. According to the invention in a limit-load situation the maximum amplitude of the modulation voltage (Vm) is allowed to drop, the amplitude of the smaller-magnitude row drive pulse (Vwrn) is feedback controlled from the modulation voltage (Vm) so that a drop in the maximum amplitude of the modulation voltage (Vm) is compensated by an increase of the magnitude of the smaller-amplitude row drive voltage (Vwrn), said increase being essentially equal to the drop in the modulation voltage (Vm), and the higher-amplitude row drive voltage (Vwrp) is maintained essentially constant. The circuit configuration according to the invention provides an essential reduction in the power consumption of the display.