GB2315632A - Horizontal sync signal diagnosing circuit for a monitor - Google Patents
Horizontal sync signal diagnosing circuit for a monitor Download PDFInfo
- Publication number
- GB2315632A GB2315632A GB9715696A GB9715696A GB2315632A GB 2315632 A GB2315632 A GB 2315632A GB 9715696 A GB9715696 A GB 9715696A GB 9715696 A GB9715696 A GB 9715696A GB 2315632 A GB2315632 A GB 2315632A
- Authority
- GB
- United Kingdom
- Prior art keywords
- signal
- horizontal sync
- horizontal
- sync signal
- abnormal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N17/00—Diagnosis, testing or measuring for television systems or their details
- H04N17/04—Diagnosis, testing or measuring for television systems or their details for receivers
- H04N17/045—Self-contained testing apparatus
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/04—Synchronising
Abstract
A horizontal sync signal diagnosing circuit for a monitor supplies a dummy horizontal sync signal to a horizontal deflecting circuit 40 when an externally-received horizontal sync signal is abnormal and thus is capable of stabilizing the horizontal deflecting circuit. A microprocessor 10 detects an abnormal state of an externally-received horizontal sync signal to generate a control signal to weaken the abnormal horizontal sync signal in case of being abnormal, 20.
Description
HORIZONTAL SYNC SIGNAL DIAGNOSING
CIRCUIT FOR A MONITOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monitor, and more particularly to a horizontal sync signal diagnosing circuit for a monitor, wherein, when an externally-received horizontal sync signal is abnormal, a dummy horizontal sync signal is supplied to a horizontal deflecting circuit for being capable of stabilizing a horizontal deflection coil.
2. Description of the Prior Art
Generally, an electron emitted from a cathode of a Cathode Ray Tube(CRT) accelerates in accordance with a voltage applied to a grid terminal and then is deflected by a magnetic field generated at a deflection coil. The deflected electron collides onto a phosphor screen.
Therefore, a general monitor is equipped with a horizontal deflection coil for deflecting the electron in the horizontal direction and a vertical deflection coil for deflecting it in the vertical direction.
Once a current is supplied to such horizontal and vertical deflection coils, a magnetic field is formed at the horizontal and vertical deflection coils. Then, the electron is deflected in accordance with the produced magnetic field. At this time, a deflecting distance of the electron is in proportion to intensity of the produced magnetic field, and the produced magnetic field is in proportion to the quantity and direction of current flowing through the horizontal deflection coil.
That is, the horizontal deflection coil is supplied with the current of sawtooth waveform as shown in FIG. 1. Here, the electron deflects to the leftmost end point of the phosphor screen at a point a, straightly advances to the center of the phosphor screen at a point b and deflects to the rightmost end point of the phosphor screen at a point c. The electron is again deflected to the leftmost end point at a point a'.
FIG. 2 is a block diagram showing a construction of a general horizontal deflecting circuit. Referring to FIG. 2, a reference numeral 1 denotes a horizontal oscillating section for modulating an externallyreceived horizontal sync signal Hs to generate a horizontal driving signal Hd; and reference numeral 2 denotes a horizontal deflecting section for generating a horizontal deflection signal Hd of sawtooth waveform in accordance with horizontal driving signal Hd.
In the horizontal deflecting circuit for a monitor formed as above, externally-received horizontal sync signal Hs is supplied to horizontal oscillating section 1 which pulsewidth-modulates horizontal sync signal Hs to provide horizontal driving signal Hd corresponding to horizontal sync signal Hs.
Horizontal driving signal Hd is supplied to horizontal deflecting section 2. Then, horizontal deflecting section 2 generates the horizontal deflection signal of sawtooth waveform in accordance with horizontal driving signal Hs, and supplies the generated horizontal deflection signal to a horizontal deflection coil. Thereafter, the horizontal deflection coil forms the magnetic field in accordance with the horizontal deflection signal, and deflects the electron emitted from a cathode in accordance with the magnetic field produced.
The conventional monitor frequently involves a problem. That is, if externally-received horizontal sync signal Hs is abnormal, horizontal deflecting section 2 is inadvertently operated to frequently degrade reliability of the monitor.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a horizontal sync signal diagnosing circuit for a monitor, wherein, when a horizontal sync signal is abnormal, a dummy horizontal sync signal is supplied to a horizontal deflecting section for being capable of stabilizing the monitor.
To achieve the above object of the present invention, a horizontal sync signal diagnosing circuit for a monitor includes a microprocessor for detecting whether an externally-received horizontal sync signal is abnormal or not, and generating a control signal to weaken the abnormal horizontal sync signal when the horizontal sync signal is abnormal. A signal controlling section receives the horizontal sync signal and is switched in accordance with the control signal of the microprocessor to weaken the abnormal horizontal signal and to allow the normal horizontal sync signal to pass therethrough, and a signal generating section generates a dummy horizontal sync signal used as the normal horizontal sync signal when the abnormal horizontal sync signal is weakened.
Additionally, a horizontal deflecting section generates a horizontal driving signal by pulsewidthmodulating an output signal of the signal controlling section and signal generating section, generates a horizontal deflection signal of sawtooth waveform in accordance with the generated horizontal deflection signal, and supplies the generated horizontal deflection signal to a horizontal deflection coil.
According to the preferred embodiment of the present invention, the externally-received horizontal sync signal is supplied to the microprocessor which determines whether the horizontal sync signal is abnormal or not. If the horizontal sync signal is abnormal, a control signal of high level is provided.
When the horizontal sync signal is normal, a control signal of low level is provided. The control signal of high level is supplied to the signal controlling section which in turn mutes the abnormal horizontal sync signal in accordance with the control signal of high level. In the meantime, the signal generating section produces a dummy horizontal sync signal which is supplied to the horizontal deflecting circuit.
Then, horizontal deflecting circuit modulates the dummy horizontal sync signal to produce the horizontal driving signal, generates the horizontal deflection signal of sawtooth waveform in accordance with the horizontal driving signal produced, and supplies the generated horizontal deflection signal to the horizontal deflection coil. Consequently, the horizontal deflection signal of sawtooth waveform is generated in accordance with the dummy horizontal sync signal when the horizontal sync signal is abnormal, so that damage resulting from the abnormal horizontal sync signal can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
The above objects and other advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:
FIG. 1 is a view showing a current sawtooth waveform supplied to a horizontal deflection coil in a conventional monitor;
FIG. 2 is a view showing a construction of the conventional horizontal deflection circuit;
FIG. 3 is a view showing a construction of a horizontal sync signal diagnosing circuit according to an embodiment of the present invention;
FIG. 4 is a view showing a construction of one embodiment of the signal controlling section in FIG.
3; and
FIG. 5 is a view showing a construction of another embodiment of the signal controlling section in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A horizontal sync signal diagnosing circuit for a monitor according to an embodiment of the present invention will be described in more detail with reference to accompanying drawings.
FIG. 3 is a view showing a construction of the horizontal sync signal diagnosing circuit according to an embodiment of the present invention. In FIG. 3, reference numeral 10 denotes a microprocessor for determining whether an externally-received horizontal sync signal Hs is abnormal or not and generating a control signal cltl for muting horizontal sync signal
Hs if horizontal sync signal Hs is in the abnormal condition. A reference numeral 20 denotes a signal controlling section for controlling the output of the horizontal sync signal in accordance with control signal cltl of microprocessor 10.
A reference numeral 30 denotes a signal generating section for generating a dummy horizontal sync signal DHs; and reference numeral 40 denotes a horizontal deflecting circuit for generating a horizontal driving signal Hd by pulsewidth-modulating dummy horizontal sync signal DHs or horizontal sync signal Hs supplied from signal controlling section 20, and supplying generated horizontal driving signal Hd to a horizontal deflection coil (not shown).
Here, the construction of signal controlling section 20 will be described in more detail with reference to FIG. 4.
In FIG. 4, an emitter side of a transistor Q51 switching in accordance with control signal cltl of microprocessor 10 is grounded, and a collector side of transistor Q21 is serially connected with resistors
R21 and R22 for weakening horizontal sync signal Hs.
One side of resistor R21 is connected to the input side of horizontal sync signal Hs, and the other side of resistor R21 is connected to the input side of horizontal deflecting circuit 40. In this embodiment, transistor Q21 is of an NPN-type.
In connection with this embodiment of the present invention formed as above, an operation and effect of the horizontal sync signal diagnosing circuit for the monitor will be described with reference to accompanying drawings.
Horizontal sync signal Hs supplied from video signal processing section 1 is supplied to microprocessor 10 which in turn determines whether horizontal sync signal Hs is abnormal or not. If horizontal sync signal Hs is abnormal, control signal clt of high level is generated. The generated control signal clt of high level is supplied to signal controlling section 20.
Signal controlling section 20 mutes horizontal sync signal Hs in accordance with control signal clt of high level. A step of muting horizontal sync signal
Hs will be described in more detail with reference to
FIG. 4.
Control signal clt of high level is supplied to transistor Q21 of signal controlling section 20, and transistor Q21 is switched to the on state. Therefore, horizontal sync signal Hs supplied from video signal processing section 1 is supplied to the emitter side of transistor Q21 via resistors R21 and R22 and the collector side of transistor Q21.
Accordingly, since horizontal sync signal Ho provided from signal controlling section 20 satisfies the following equation 1, the magnitude of horizontal sync signal Hs is decreased.
R21
Ho = R21 x Hs.. .. equation 1
(R21 +R22) On the other hand, signal generating section 30 generates dummy horizontal sync signal DHs, and generated dummy horizontal sync signal DHs is supplied to horizontal deflecting circuit 40. Thereafter, horizontal deflecting circuit 40 modulates dummy horizontal sync signal DHs to generate horizontal driving signal Hd, generates the horizontal deflection signal of sawtooth waveform in accordance with horizontal driving signal Hd, and supplies the generated horizontal deflection signal to the horizontal deflection coil.
However, when horizontal sync signal Hs is normal, control signal clt of low level is generated.
Control signal clt of low level is supplied to signal controlling section 20.
Signal controlling section 20 allows horizontal sync signal Hs to pass therethrough in accordance with control signal clt of low level. A step of passing horizontal sync signal Hs will be described in more detail with reference to FIG. 4.
Control signal clt of low level is supplied to transistor Q21 of signal controlling section 20, and transistor Q21 is switched to the off state.
Accordingly, horizontal sync signal Hs is supplied to horizontal deflecting circuit 40 via resistor R21.
Horizontal deflecting circuit 40 modulates horizontal sync signal Hs to generate horizontal driving signal Hd, generates the horizontal deflection signal in accordance with generated horizontal driving signal Hd, and supplies the generated horizontal deflection signal to the horizontal deflection coil.
In other words, when horizontal sync signal Hs is abnormal, dummy horizontal sync signal DHs is supplied to horizontal deflecting circuit 40 to stably operate horizontal deflecting circuit 40.
FIG. 5 is a view showing a construction of another embodiment of the signal controlling section in FIG. 3. In FIG. 5, a collector side of a transistor
Q51 switching in accordance with control signal cltl of microprocessor 10 is grounded, and an emitter side of transistor Q51 is serially connected with resistors
R51 and R52 through which horizontal sync signal Hs is bypassed. One side of resistor R51 is connected to an output side of video signal processing section 1, and the other side of resistor R51 is connected to the input side of horizontal deflecting circuit 40. In this embodiment, transistor Q51 is of a PNP-type.
In describing an operation and effect of another embodiment of the present invention formed as above, microprocessor 10 generates control signal clt of low level when horizontal sync signal Hs is abnormal.
Here, control signal clt of low level is supplied to signal controlling section 20.
Control signal clt of low level is supplied to transistor Q51 of signal controlling section 20, and transistor Q51 is switched to the on state. Therefore, externally-received horizontal sync signal Hs is supplied to the collector side of transistor Q51 via resistors R51 and R52 and the emitter side of transistor Q51.
Consequently, since horizontal sync signal Ho provided from signal controlling section 20 satisfies equation 1, the magnitude of horizontal sync signal Hs is decreased.
However, when horizontal sync signal Hs is normal, control signal clt of high level is generated.
Thereafter, control signal clt of high level is supplied to signal controlling section 20.
Control signal clt of high level is supplied to transistor Q51 of signal controlling section 20, and transistor Q51 is switched to the off state.
Accordingly, externally-received horizontal sync signal Hs is supplied to horizontal deflecting circuit 40 via resistor R51. Horizontal deflecting circuit 40 pulsewidth-modulates horizontal sync signal Hs to generate horizontal driving signal Hd, generates the horizontal deflection signal of sawtooth waveform in accordance with generated horizontal driving signal
Hd, and supplies the generated horizontal deflection signal to the horizontal deflection coil.
In other words, if horizontal sync signal Hs is abnormal, dummy horizontal sync signal DHs is supplied to horizontal deflecting circuit 40 to stably operate horizontal deflecting circuit 40.
By employing the horizontal sync signal diagnosing circuit for the monitor according to the present invention, the dummy horizontal sync signal is supplied to the horizontal deflecting circuit when the externally-received horizontal sync signal is abnormal. Hence, the horizontal deflection coil can be protected from the abnormal horizontal sync signal.
While the present invention has been particularly shown and described with reference to particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the scope of the invention as defined by the appended claims. For instance, since the monitor constitutes the preferred embodiments of the present invention herein, the present invention may be applied to every video signal processing system such as general VCRs.
Claims (9)
1. A horizontal sync signal diagnosing circuit for a monitor comprising:
a microprocessor for detecting whether an externally-received horizontal sync signal is abnormal or not, and generating a control signal to weaken the abnormal horizontal sync signal when said horizontal sync signal is abnormal;
signal controlling means for receiving said horizontal sync signal and switching in accordance with said control signal of said microprocessor to weaken said abnormal horizontal signal and to allow the normal horizontal sync signal to pass therethrough;
signal generating means for generating a dummy horizontal sync signal used as said normal horizontal sync signal when said abnormal horizontal sync signal is weakened; and
horizontal deflecting means for generating a horizontal driving signal by pulsewidth-modulating an output signal of said signal controlling means and signal generating means, generating a horizontal deflection signal of sawtooth waveform in accordance with said generated horizontal deflection signal and, supplying the generated horizontal deflection signal to a horizontal deflection coil.
2. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 1, wherein said signal controlling means is formed for weakening said abnormal horizontal sync signal when said control signal of said microprocessor is of high level and allowing passage of passing said normal horizontal sync signal when said control signal of said microprocessor is of low level.
3. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 1 or 2, wherein said signal controlling means comprises:
a transistor for switching in accordance with said control signal of said microprocessor; and
a plurality of resistors for weakening said abnormal horizontal sync signal in accordance with the switching state of said transistor.
4. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 3, wherein said transistor is of an NPN-type which switches to the on state when said control signal of said microprocessor has the high level.
5. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 3, wherein said transistor is of a PNP-type which switches to the on state when said control signal of said microprocessor has the low level.
6. A horizontal sync signal diagnosing circuit for a monitor comprising:
a microprocessor for detecting whether an externally-received horizontal sync signal is abnormal or not, and generating a control signal to weaken the abnormal horizontal sync signal when said horizontal sync signal is abnormal;
signal controlling means formed by a transistor for switching in accordance with said control signal of said microprocessor and a plurality of resistors for weakening said abnormal horizontal sync signal in accordance with the switching state of said transistor, said signal controlling means for muting said abnormal horizontal sync signal when said horizontal sync signal is received and allowing passage of said normal horizontal sync signal therethrough;
signal generating means for generating a dummy horizontal sync signal used as said normal horizontal sync signal when said abnormal horizontal sync signal is weakened; and
horizontal deflecting means for generating a horizontal driving signal by pulsewidth-modulating an output signal of said signal controlling means and signal generating means, generating a horizontal deflection signal of sawtooth waveform in accordance with said generated horizontal deflection signal and supplying the generated horizontal deflection signal to a horizontal deflection coil.
7. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 6, wherein said transistor is of an NPN-type which switches to the on state when said control signal of said microprocessor has the high level.
8. A horizontal sync signal diagnosing circuit for a monitor as claimed in claim 6, wherein said transistor is of a PNP-type which switches to the on state when said control signal of said microprocessor has the low level.
9. A circuit substantially as hereinbefore described with reference to and illustrated by any one of Figures 3 to 5.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019960030112A KR980010729A (en) | 1996-07-24 | 1996-07-24 | Monitors self-diagnosis |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9715696D0 GB9715696D0 (en) | 1997-10-01 |
| GB2315632A true GB2315632A (en) | 1998-02-04 |
| GB2315632B GB2315632B (en) | 2000-04-05 |
Family
ID=19467376
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9715696A Expired - Fee Related GB2315632B (en) | 1996-07-24 | 1997-07-24 | Horizontal sync signal diagnosing circuit for a monitor |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH10126637A (en) |
| KR (1) | KR980010729A (en) |
| GB (1) | GB2315632B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0193125A1 (en) * | 1985-02-21 | 1986-09-03 | Fuji Photo Film Co., Ltd. | Synchronization control system in video signal reproducing device |
| GB2291305A (en) * | 1994-06-30 | 1996-01-17 | Mitsubishi Elec Semiconductor | Horizontal sync generating circuit |
-
1996
- 1996-07-24 KR KR1019960030112A patent/KR980010729A/en active IP Right Grant
-
1997
- 1997-07-24 JP JP9198110A patent/JPH10126637A/en not_active Withdrawn
- 1997-07-24 GB GB9715696A patent/GB2315632B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0193125A1 (en) * | 1985-02-21 | 1986-09-03 | Fuji Photo Film Co., Ltd. | Synchronization control system in video signal reproducing device |
| GB2291305A (en) * | 1994-06-30 | 1996-01-17 | Mitsubishi Elec Semiconductor | Horizontal sync generating circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2315632B (en) | 2000-04-05 |
| GB9715696D0 (en) | 1997-10-01 |
| KR980010729A (en) | 1998-04-30 |
| JPH10126637A (en) | 1998-05-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20010724 |