Method for compensating perturbations caused by demultiplexing an analog signal in a matrix display
The present invention relates to a method of compensating for the disturbances due to the demultiplexing of an analogue signal with regard to a circuit comprising N data lines, wherein the demultiplexing is carried out by sample-and-hold circuits whose input receives the analogue signal and whose output is connected to one of the N data lines, the N sample-and-hold circuits being operated in succession by a sampling signal (ECHi). During the application of the sampling signal (ECHi, V 1 ) to one of the sample-and-hold circuits, an opposite compensation level (V 3 ) which is lower than the level of the sampling signal is applied to the N−1 sample-and-hold circuits. Application in particular to LCD screens.
1. Method of compensating for disturbances due to demultiplexing an analogue signal with regard to a circuit comprising N data lines, N being a positive integer, wherein the demultiplexing is carried out by sample-and-hold circuits whose input receives the analogue signal and whose output is connected to one of the N data lines, the method comprising steps of:
providing a sampling signal comprising a first level V 1 configured to turn on the sample-and-hold circuits, a second level V 2 configured to keep the sample-and-hold circuits off, and a third level V 3 also configured to keep the sample-and-hold circuits off, wherein a difference in level between the levels V 1 and V 3 is greater than a difference in level between the levels V 1 and V 2 ; and
operating the sample-and-hold circuits in succession by applying the first level V 1 of the sampling signal to a first one of the sample-and-hold circuits to turn on the first one of the sample-and-hold circuits while applying the third level V 3 of the sampling signal to sample-and-hold circuits other than the first one of the sample-and-hold circuits.
2. The method according to claim 1 , wherein the providing step includes providing the levels V 1 , V 2 , and V 3 of the sampling signal such that (V 2 −V 3 )=(V 1 −V 2 )/(N−1).
3. The method according to claim 1 , wherein the transition times for going from the second level V 2 to the first level V 1 and from the second level V 2 to the third level V 3 are identical, and in that the transition times for going from the first level V 1 to the second level V 2 and from the third level V 3 to the second level V 2 are identical.
4. The method according to claim 1 , wherein the sample-and-hold circuits comprise transistors and the step of operating the sample-and-hold circuits in succession includes applying the sampling signal to a control electrode of each of the transistors.
5. The method according to claim 4 , wherein the transistors are FET transistors.
6. The method according to claim 1 , wherein the circuit comprising N data lines is a matrix display.
7. The method according to claim 6 , wherein the matrix display is an LCD screen, an LED screen or an OLED screen.
8. The method according to claim 6 , wherein the analogue signal is demultiplexed with the aid of P blocks of M sample-and-hold circuits, P and M being chosen to be positive integers and so that N=P×M.