Apparatus and method for preventing poor operation of key due to chattering noise

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my applications entitled APPARATUS AND METHOD FOR PREVENTING POOR OPERATION OF KEY DUE TO CHATTERING NOISE filed in the Korean Industrial Property Office on 27 th of May 1997 and there duly assigned Serial No. P97-20949 by that Office.

1. Technical Field

The present invention relates to an apparatus and method for preventing poor operation of a key due to chattering noise, and specifically, to an apparatus and method for preventing poor operation of a key due to chattering noise. In that regard, “chattering noise” is the repeated opening and closing of contact points of tactile switches of a control button section attached to a display monitor because of external causes.

2. Related Art

Electric and electronic products generally employ microcomputers to control their additional devices. The microcomputer is also used to control a display monitor of a computer and each of its circuit blocks.

In particular, the microcomputer with a display monitor receives horizontal and vertical synchronous signals from the computer associated with the display monitor, and drives corresponding horizontal and vertical deflection circuits, as well as a high voltage circuit, to generate the necessary voltages for control of the display on a cathode ray tube (CRT) contained within the display monitor.

In addition, the display monitor typically includes a control button section containing switches for controlling (for example) horizontal position, vertical position, horizontal size, etc., of the image displayed on the CRT of the display monitor. Moreover, such a control button section often employs tactile switches which employ a contact point method. A problem arises in that, when a user employs the tactile switches, they can generate a chattering noise representing instability of the contact point due to physical and electrical causes externally created. This presents a problem to the operation of the display monitor, and therefore there is a need for the development of an apparatus and method for preventing poor operation of a key resulting from poor operation of a tactile switch of a control button section of a display monitor due to chattering noise generated in the tactile switch.

An object of the present invention is to provide an apparatus and method for preventing poor operation of a key due to poor operation of a tactile switch of a control button section of a display monitor as a result of chattering noise generated in the tactile switch.

To accomplish the object of the present invention, there is provided an apparatus for preventing poor operation of a key due to chattering noise, including: a control button section for generating a key signal to control a display monitor; and a microcomputer which contains a control program for preventing poor operation of a key due to chattering noise in the key signal generated by the control button section, by detecting the key signal when the chattering noise is generated, determining if the key signal is in a normal state or not, and processing the key signal.

A method of preventing poor operation of a key due to chattering noise according to the present invention includes the steps of: (a) detecting a key input voltage with an AD port of a microcomputer; (b) determining whether the key input voltage detected in step (a) is within the limits of a minimum and maximum voltage required for an effective key; (c) setting a key flag when it is determined that the key input voltage is within the limit required for an effective key; (d) resetting the key flag when it if determined that the key input voltage is not within the limit required for an effective key; (e) confirming the key flag setting from steps (c) and (d); (f) executing a key input according to a key execution voltage when step (e) confirms that the key flag is set; and (g) ignoring the key input when step (e) confirms that the key flag is not set.

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols represent the same or similar components, wherein:

FIG. 1 is a block diagram showing a configuration of the inner circuit of a display monitor;

FIG. 2 is a block diagram showing a configuration of the inner circuit of a display monitor including an apparatus for preventing poor operation of a key according to the present invention;

FIG. 3 is a flow diagram showing a method for preventing poor operation of a key according to the present invention; and

FIGS. 4A and 4B are diagrams showing waveforms of chattering noise generated in a tactile switch and filtered chattering noise, respectively.

FIG. 1 is a block diagram showing a configuration of the inner circuit of a display monitor. Referring to FIG. 1, a computer 100 includes a CPU 110 for receiving and processing a key signal generated by a user, and for generating data depending on the processed result, and a video card 120 for receiving the data from CPU 110 , for processing it to obtain a video signal (R,G,B), and for generating a horizontal synchronous signal H-SYNC and a vertical synchronous signal V-SYNC for synchronizing the video signal (R,G,B).

A display monitor 200 , which receives the video signal (R,G,B) from video card 120 of computer 100 and processes it to display it as an image, includes: a control button section 210 for generating switch signals for controlling images displayed on display monitor 200 ; a microcomputer 220 for receiving horizontal and vertical synchronous signals H-SYNC and V-SYNC, respectively, from video card 120 and switch signals from control button section 210 , and for processing them to determine the resolution and frequency of the video signal (R,G,B) and to generate a vertical oscillation pulse and a horizontal oscillation pulse; a vertical deflection circuit 230 for receiving the vertical oscillation pulse from microcomputer 220 so as to generate a vertical sawtooth wave current which is provided to a deflection yoke DY; a horizontal deflection circuit 240 for receiving the horizontal oscillation pulse from microcomputer 220 so as to generate a horizontal sawtooth wave current which is provided to the deflection yoke DY; a high voltage circuit 250 for providing a high voltage to the anode (A) of a cathode ray tube (CRT) 290 according to the cycle of the horizontal oscillation pulse generated by microcomputer 220 ; a video pre-amplifier 260 for receiving the video signal (R,G,B) from video card 120 of computer 100 and amplifying it to a predetermined level; a video main amplifier 270 for sufficiently amplifying the video signal (R,G,B) amplified by video pre-amplifier 260 to a predetermined level so as to display it on the CRT 290 according to the cycle of the horizontal sawtooth wave current and vertical sawtooth wave current generated by the deflection yoke DY; and a power circuit 280 for supplying DC voltage required for operating each circuit block of the display monitor 200 .

The operation of each circuit block of display monitor 200 with the above configuration is described below in detail. Horizontal and vertical synchronous signals H-SYNC and V-SYNC, respectively, generated by video card 120 of computer 100 are applied to microcomputer 220 which stores data for controlling the display monitor picture. Microcomputer 220 also receives a switch signal generated when control button section 210 is used. Control button section 210 includes a horizontal position (H-POSI) switch 211 for controlling the horizontal position on display monitor 200 , a vertical position (V-POSI) switch 212 for controlling the vertical position, a horizontal size (H-SIZE) switch 213 for controlling the horizontal size, and a pin switch 214 for controlling a distortion-in-pin phenomenon which is generated in display monitor 200 . Control button section 210 may includes more switches as needed.

When the switch signal is generated by control button section 210 , microcomputer 220 receives the switch signal and the horizontal and vertical synchronous signals H-SYNC and V-SYNC, respectively. Microcomputer 220 then reads picture control data previously stored according to the applied signals, and corrects it, generating the horizontal and vertical oscillation pulses. Vertical deflection circuit 230 receives the vertical oscillation pulse from microcomputer 220 so as to provide the vertical sawtooth wave current corresponding to vertical synchronous signal V-SYNC to deflection yoke DY, thereby determining a vertical scanning cycle. Horizontal deflection circuit 240 receives the horizontal oscillation pulse from microcomputer 220 , so as to generate the horizontal sawtooth wave current corresponding to horizontal synchronous signal V-SYNC to deflection yoke DY, thereby determining a horizontal scanning cycle.

The CRT 290 , which displays an image according to the cycles of the horizontal sawtooth wave current and vertical sawtooth wave current generated by deflection yoke DY, receives the video signal (R,G,B) output from video card 120 as amplified by video pre-amplifier 260 and video main amplifier 270 , and scans it according to the cycles of the horizontal sawtooth wave current and vertical sawtooth wave current which flow through deflection yoke DY, thereby displaying the image. The anode (A) attached on one side of the CRT 290 receives high voltage multiplied by high voltage circuit 250 depending on the cycle of the horizontal oscillation pulse output from microcomputer 220 , and forms an anode field inside the CRT 290 according to the applied high voltage so as to control the luminance of the image.

Power circuit 280 , which supplies DC voltage required for each circuit block of display monitor 200 , receives alternating current (AC) and rectified it in a rectifier 281 to form a direct current (DC) voltage required at the secondary side of a switching transformer 282 and outputs it through a voltage output port 283 . Control button section 210 for controlling the display monitor 200 has a tactile switch using a contact point method. However, this generates a chattering noise representing instability of the contact point due to physical and electrical causes externally created.

FIG. 2 is a block diagram showing a configuration of the inner circuit of a display monitor including an apparatus for preventing poor operation of a key according to the present invention. Referring to FIG. 2, the display monitor includes: a control button section 10 for generating key signals for controlling the picture of the display monitor or its function; a microcomputer 20 for receiving a horizontal synchronous signal H-SYNC and a vertical synchronous signal V-SYNC generated by a computer (shown in FIG. 1) to determine the resolution and frequency mode of a video signal (R,G,B) generated by the computer, the microcomputer 20 containing a control program for preventing poor operation of a key due to chattering noise in a key signal output from control button section 10 by detecting the key signal when the chattering noise is created so as to determine whether or not the key signal is in normal state, and to process it, the microcomputer 20 generating horizontal and vertical oscillation pluses according to the key signal applied thereto; a vertical deflection circuit 30 for receiving the vertical oscillation pulse from microcomputer 20 so as to provide a vertical sawtooth wave current to deflection yoke DY; a horizontal deflection circuit 40 for receiving the horizontal oscillation pulse from microcomputer 20 so as to provide a horizontal sawtooth wave current to deflection yoke DY; a video pre-amplifier 50 for amplifying the video signal (R,G,B) output from the computer to a predetermined level; and a video main amplifier 60 for amplifying the video signal amplified by video pre-amplifier 50 sufficiently to display it on a CRT 70 according to the cycles of the horizontal sawtooth wave current and vertical sawtooth wave current generated by the deflection yoke DY.

Control button section 10 includes a plurality of tactile switches SW 1 to SW 5 and resistors R 1 to R 4 which operate by DC voltage (5V) induced through a resistor R 5 , and which control the function of the display monitor and the image displayed thereon. Microcomputer 20 includes an AD port for detecting the key signal when control button section 10 generates chattering noise. With the aforementioned display monitor for preventing poor operation of a key due to the chattering noise, the algorithm of a control program for preventing poor operation of a key stored in microcomputer 20 is explained below with reference to FIG. 3 .

FIG. 3 is a flow diagram showing a method for preventing poor operation of a key according to the present invention. Referring to FIG. 3, the method for preventing poor operation of a key comprises: a step S 21 in which microcomputer 20 detects with its AD port a key input voltage V AD according to a key signal output from control button section 10 , a step S 22 of determining whether the key input voltage V AD detected in step S 21 is within the limits defined by a minimum voltage V min-r and a maximum voltage V max-r required for an effective key operation; a step S 23 of setting a key flag when it is determined in step S 22 that the key input voltage V AD is within the limits required for effective key operation; a step S 24 of resetting the key flag when it is determined in step S 22 that the key input voltage V AD is not within the required limits; a step S 25 of confirming the key flag set in key flag setting step S 23 and the key flag resetting step S 24 ; a step S 26 of executing a key input according to a key execution voltage V old when the key flag is set as confirmed in step S 25 , and a step S 27 of ignoring the key input when the key flag is not set as confirmed in step S 25 .

Key flag setting step S 23 comprises: a step S 23 a of determining whether the noise filtering factor MAXn corresponds to a specific number (n) when it is determined that the key input voltage V AD is within the required limits of step S 22 ; a step S 23 b of replacing the key input voltage V AD with the key execution voltage V old and setting the key flag when it is determined that noise filtering factor MAXn corresponds to the specific number (n) in step S 23 a ; and a step S 23 c of increasing the specific number (n) in order to set the next key flag when it is determined that the filtering noise factor MAXn does not correspond to the specific number (n) in step S 23 a.

Key flag resetting step S 24 comprises: a step S 24 a of determining whether the specific number (n) is “0” when it is determined that the key input voltage V AD is not within the limits required in step S 22 ; a step S 24 b of resetting the key flag when it is determined that the specific number (n) is “0” in step S 24 a ; a step S 24 c of resetting the minimum voltage V min-r and maximum voltage V max-r required for effective key operation when the key flag is reset in step S 24 b ; and a step S 24 d of decreasing the specific number (n) when it is determined that it is not “0” in step S 24 a.

The operation of the display monitor of the present invention, which prevents poor operation of a key due to chattering noise using the above-described method, is described below with reference to FIGS. 4A and 4B. With this display monitor, video pre-amplifier 50 of FIG. 2 receives the video signal (R,G,B) generated by the computer and amplifies it to a predetermined level. The amplified video signal is sufficiently amplified by video main amplifier 60 so as to be applied to the CRT 70 which scans the sufficiently amplified video signal (R,G,B) according to the cycles of the horizontal sawtooth wave and vertical sawtooth wave current formed in deflection yoke DY, thereby displaying it. The horizontal sawtooth wave current and vertical sawtooth wave current are formed in deflection yoke DY in such a manner that microcomputer 20 receives horizontal and vertical synchronous signals H-SYNC and V-SYNC from the computer to generate the horizontal and vertical oscillation pulses, and sends the horizontal and vertical oscillation pulses to horizontal and vertical deflection circuits 30 and 40 , respectively, which process them. The horizontal sawtooth current and vertical sawtooth wave current generated in deflection yoke DY by horizontal and vertical deflection circuits 30 and 40 , respectively, determine the horizontal and vertical scanning cycles of the video signal (R,G,B) applied to the CRT 70 and display the video signal according to the scanning cycles.

When a user wants to control an image on the display monitor which operates as described above, he uses control button section 10 . That is, the user selects one of tactile switches SW 1 to SW 5 of control button section 10 to control an image displayed on the CRT. When switch SW 1 is a tactile switch for controlling the horizontal position, for example, the user uses it to control the horizontal position of the image displayed on the display monitor. In this case, switch SW 1 generates a key signal which is applied to the AD port of microcomputer 20 through resistors R 1 to R 4 and is detected by microcomputer 20 . In other words, microcomputer 20 executes the control program to read key input voltage V AD , which is the key signal of switch SW 1 selected from tactile switches SW 1 to SW 5 of control button section 10 , in step S 21 .

In key input voltage V AD range determining step S 22 , it is determined whether the key input voltage V AD read by microcomputer 20 is within the limits of the minimum voltage V min-r to maximum voltage V max-r required for effective key operation, as shown in FIG. 4A (V min-r ≦V AD ≦V max-r ). When it is within the limits, it is determined whether a predetermined number (n) of a noise filtering factor corresponds to the number of noise filtering factor (MAXn) in step S 23 a of key flag setting step S 23 . That is, it is determined whether the predetermined number (n) of a noise filtering factor in the effective range of the key, as shown in FIG. 4A, corresponds to the number of noise filtering factor (MAXn) showing the number of dots seen in FIG. 4A (n=MAXn). When they correspond to each other, key flag setting step S 23 b is executed to set the key flag, replacing key input voltage V AD with key execution voltage V old (V old =V AD ). On the contrary, when they do not correspond to each other, predetermined number (n) of the noise filtering factor increases (n=n+1) to set the key flag in step S 23 c.

When it is determined that key input voltage V AD is not within the limits of the minimum voltage V min-r and maximum voltage V max-r required for effective key operation in step S 22 , it is determined whether the predetermined number (n) corresponds to “0” in step S 24 a of key flag resetting step S 24 . When the predetermined number (n) corresponds to “0”, it is determined that the key signal of the tactile switch selected from control button section 10 of FIG. 3 is not in a normal state. Then, the key flag is reset in step S 24 b , and step S 24 c is executed to reset the minimum range V min-r and maximum range V max-r in accordance with effective key operation, thereby resetting the key flag. When the predetermined number (n) is not “0” in step S 22 , it is decreased (n=n−1) in step S 24 d so as to set the key flag according to the previous key signal.

When the key flag is set in key flag setting step S 23 and key flag resetting step S 24 , this is confirmed in step S 25 . When it is confirmed that the key flag is set, the key signal of switch SW 1 of the tactile switches of control button section 10 is filtered, as shown in FIG. 4B, and this filtered signal is detected by microcomputer 20 in key input execution step S 26 . When it is determined that the key flag is not set in step S 25 , key ignoring step S 27 is executed so as to ignore the key signal input through the AD port of microcomputer 20 , thereby obtaining the filtered output as shown in FIG. 4 B. When microcomputer 20 detects the key signal generated by tactile switch SW 1 for controlling the horizontal position, it controls horizontal and vertical deflection circuits 30 and 40 , respectively, in order to correct the horizontal position. Under the control of microcomputer 20 , horizontal and vertical deflection circuits 30 and 40 , respectively, generate a current signal which is corrected and sent to deflection yoke DY, thereby controlling the horizontal position of an image displayed on the CRT 70 . As described above, similar to switch SW 1 , tactile switches SW 2 to SW 5 operate according to their control functions to prevent poor operation of a key due to chattering noise.

According to the present invention, when the chattering noise is created at the tactile switch of the control button section 10 of the display monitor, the AD port of the microcomputer 20 detects the chattering noise to determine whether a key is operating normally or not. Accordingly, poor operation of the keys due to the chattering noise is prevented.

It will be apparent to those skilled in the art that various modifications and variations can be made in the apparatus and method for preventing poor operation of a key due to chattering noise of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.