Abstract:
A high-potential output stage includes an output circuit to power a load with a variable high potential when it receives a low-level active input logic signal. It also includes a driving circuit which produces a high-level control logic signal as a function of the input logic signal to drive the output circuit which is powered by a DC high potential. The output stage also synchronizes the input logic signal with variations of the variable high potential.
Abstract:
A method for controlling cells of a plasma screen of array type, formed of cells arranged at the intersections of lines and columns, including the step of sequentially applying to each line an activation potential and, during the activation of a line, applying an activation potential to selected columns, in which, while a line is activated, the selected columns are non-simultaneously activated.
Abstract:
A method for testing output connections of at least one driver circuit that drives a plasma display panel. According to the method, at least one output of the driver circuit is switched to a high level for a predetermined time period. The output of the driver circuit is switched to a low level, and the time to discharge the output of the driver circuit with a constant discharge current is measured. It is determined whether a capacitive load is connected to the output of the driver circuit based on the measured time to discharge. In one preferred method, these steps are repeated for each of the outputs of the driver circuit. A driver circuit for driving a plasma display panel is also provided. The driver circuit includes driver output stages, and means for selectively sinking a constant discharge current from the output of at least one of the driver output stages to ground. Additionally, the driver circuit includes means for producing a measuring logic pulse whose duration is a function of a time required to discharge the output, and means for determining whether a capacitive load is connected to the output based on the measuring logic pulse.
Abstract:
A more accurate voltage-to-time and then time-to-voltage conversion is accomplished by tailoring the amplitude versus time characteristics of the pulses generated in the voltage-to-time conversion. One embodiment includes applying a ramped voltage supply to an amplifier coupled between the voltage/time converter and the time/voltage converter. The ramped supply is arranged to condition the amplitude of a portion of respective pulses to include a slope similar to the ramped voltage applied to the time/voltage converter. This tends to effect a more accurate response in the time/voltage converter.
Abstract:
The present invention is a video drive apparatus of the two ramp type which includes facility to selectively adjust the brightness and/or the contrast of an image reproduced on a display device. In this apparatus, at least one of the ramp signals is generated digitally by for example a counter. Provision is made to change the counting rate of such counter which effects a change in display contrast. Provision is also made to selectively change the phase of the ramp signal applied to the second stage relative to the start of respective pulses of the PWM signal thereby effecting brightness changes in the reproduced image.
Abstract:
A method of and an apparatus for determining sound propagation speed in a medium which is subject to variations in this speed. A measuring tube containing the medium is energized by a loudspeaker (ultraacoustic transducers) with a controllable energizing frequency in resonance with the measuring tube containing a column of the medium to be evaluated. The resonant output frequency is detected and modulated with a low frequency signal and the mean value of the modulated output signal is formed and counted. For a predetermined count, the elapsed time is measured and from this value the propagation velocity is calculated.
Abstract:
A high-potential output stage includes an output circuit to power a load with a variable high potential when it receives a low-level active input logic signal. It also includes a driving circuit which produces a high-level control logic signal as a function of the input logic signal to drive the output circuit which is powered by a DC high potential. The output stage also synchronizes the input logic signal with variations of the variable high potential.
Abstract:
A method and circuit for displaying an image by activation of pixels of an array screen based on an image stored in digital form in memory point rows of a frame memory, having a stand-by mode that provides, at a frequency proportional to the display frequency, a cyclic succession of offset values; and for each row address of the frame memory, activating pixels of a screen line associated with said address offset by a same offset value based on the read states of the row associated with the address, and/or activating pixels of a screen line associated with the row address based on the read states of the frame memory row associated with the address offset by a same offset value.
Abstract:
The invention concerns a drive circuit for a plasma panel consisting of cells arranged at the intersections of lines and columns, comprising, for each column of the panel, a column drive unit (14′) for selecting the column by applying a voltage window, the column having a different capacitance (C2) depending on whether or not the neighboring columns are selected, each drive unit (14′) comprising first elements (T1, C, CS1) for changing the capacitance in a first predetermined time interval during the low-to-high transition of the voltage window, and second elements (T2, 28) for discharging said capacitance in a second predetermined time interval during the high-to-low transition of the voltage window, the second elements being controlled on the basis of an estimation of the capacitance obtained from data (Qi−1, Qi+1) indicating whether or not the neighboring columns of said columns have been selected.
Abstract:
A method for the control of a display screen whose pixels are cells producing light is used to minimize certain image defects known as excess brightness defects caused by major variations in the number of cells activated. For this purpose, the invention operates on the sub-division of the activation times of the cells during a given cycle time to reduce a time during which cells, selected as a function of their luminance level, are the only ones to be activated. The disclosed method can be applied especially to the control of alternating type plasma panels.