CN103731614B - The TV signal output circuit and detection method of a kind of automatic detection terminal connection - Google Patents
The TV signal output circuit and detection method of a kind of automatic detection terminal connection Download PDFInfo
- Publication number
- CN103731614B CN103731614B CN201310747712.5A CN201310747712A CN103731614B CN 103731614 B CN103731614 B CN 103731614B CN 201310747712 A CN201310747712 A CN 201310747712A CN 103731614 B CN103731614 B CN 103731614B
- Authority
- CN
- China
- Prior art keywords
- signal
- output
- control module
- digital
- selecting switch
- 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.)
- Active
Links
Abstract
The TV signal output circuit and detection method of a kind of automatic detection terminal connection, it, which is comprised at least, a digital analog converter, an analog-digital converter, a control module, a low level signal and signal source selecting switch；The digital tv signal of described output is connected to the signal input part of signal source selector with low level signal, and the output of control module is connected to the selection control end of signal source selector；The output of described signal source selector is connected to the input of digital analog converter, and the output end of described digital analog converter is connected with the input of 75 ohmic load resistances and analog-digital converter；The output of described analog-digital converter is connected to the input of control module with the digital tv signal of output；The present invention can be decreased or turned off this useless signal automatically, it is possible to reduce the energy consumption of equipment, reduce the interference of device interior, improve the performance of equipment, increase the service life of equipment.
Description
Technical field
The present invention relates to a kind of TV signal output circuit of automatic detection terminal connection, belong to television equipment technology neck
Domain.
Background technology
The equipment exported with simulated television, such as set top box, DVD（Digital video disc）Player etc., hereinafter referred to as
Equipment, is typically implemented multi-channel analog TV output interface.Multi-channel analog TV output interface can allow an equipment to export simultaneously
Onto many television terminals.Because most of user only uses a kind of TV output interface.Thus the TV signal on other roads is defeated
It is a kind of useless signal output to go out.This useless signal output is to want consumed energy, and signal can be to the other of circuit
Part produces harmful interference.If this useless signal can be decreased or turned off automatically, the energy consumption of equipment can be just reduced,
The interference of device interior is reduced, the performance of equipment is improved, increases the service life of equipment.
The content of the invention
The purpose of the present invention is to overcome that of the prior art not enough there is provided a kind of TV signal of automatic detection terminal connection
Output circuit.
For above-mentioned the deficiencies in the prior art, the present invention intends proposing a kind of TV signal output of automatic detection terminal connection
Circuit, a kind of TV signal output circuit of automatic detection terminal connection, it, which is comprised at least, a digital analog converter, one
Individual analog-digital converter, a control module, a low level signal and signal source selecting switch；The numeral of described output
Change the signal input part that TV signal is connected to signal source selector with low level signal, the output of control module is connected to signal
The selection control end of source selector；The output of described signal source selector is connected to the input of digital analog converter, institute
The output end for the digital analog converter stated is connected with the input of 75 ohmic load resistances and analog-digital converter；It is described
The output of analog-digital converter be connected to the input of control module with the digital tv signal of output.
When the TV output socket of equipment be not inserted into cable or insert the other end of cable but cable without and TV
When terminal is connected, described digital analog converter exports constant low current；When the TV output socket of equipment passes through electricity
When cable is connected with television terminal, described digital analog converter exports normal anolog TV signals.
The circuit can be with the TV output interface of automatic checkout equipment either with or without terminals such as access television sets, it is possible in collection
Realized into circuit.The circuit realized in integrated circuits can not change output interface and subsequent conditioning circuit.The present invention includes 1
DAC（Digital analog converter）, 1 ADC（Analog-digital converter）, 1 75 ohm of load resistance, 1 low level signal,
1 control module and 1 signal source selecting switch.
According to the standard GB 3174-1995 of pal mode, there is horizontal synchronizing pulse in composite video signal, horizontal synchronizing pulse
Minimum level is row sync level, during horizontal synchronizing pulse, and row sync level is the minimum level of composite video signal, and different
The value of the row sync level of TV programme is all identical.TV output circuitry needs 75 ohm of load resistance.The terminals such as television set
Input resistance be 75 ohm.When the TV output socket of equipment is not inserted into cable or inserts the other end of cable but cable
When not being connected with the terminal such as TV, DAC outputs are only connected to 75 ohm of load resistance, DAC output equivalent load resistances
Equal to 75 ohm.When the terminals such as TV output socket and the TV of equipment are normally connected by cable, DAC output-parallels 75
The input resistance of the terminals such as ohmic load resistance and 75 ohm of TVs, DAC output equivalents load resistance is equal to 37.5 ohm.
DAC operation principle is to produce in check electric current according to the digital control word of input.Identical control word can be produced
The electric current of raw formed objects.DAC output voltage values are DAC product of the output current with DAC output equivalent load resistances.When
When the TV output socket of equipment is not connected with the terminal such as TV, DAC output equivalent load resistances are 75 ohm.Work as equipment
The terminal such as TV output socket and TV when being connected, DAC output equivalent load resistances are 37.5 ohm.Therefore the electricity of equipment
Magnitude of voltage when being connected depending on terminals such as output socket and TVs be equipment TV output socket not with the terminal phase such as TV
1/2 of magnitude of voltage during connection.
ADC samplings DAC output voltage values.Control module is carried out according to the ADC data signals sampled and DAC control word
Condition adjudgement, and according to judged result control signal source selecting switch.
When device power-up, the default setting of control module is to have the connection of the terminals such as television set.When the state of control module
It is that control module judges whether into sync level of the entering a profession defeated moment according to input signal when having the connection of the terminals such as television set.When
Enter to enter a profession sync level output time, and control module is judged ADC sampled values.With DAC under 75 ohm of equivalent loads
Output level is threshold value with the median of output levels of the DAC under 37.5 ohm of equivalent loads.If ADC sampled values are more than threshold
During value, the state of control module enters the terminal connection status such as no television set.Now signal source selecting switch selection d conducts
DAC input signal.The value of low level signal is equal with the minimum level of the line synchronising signal of TV signal.If ADC samples
When value is less than threshold value, the state of control module maintains the terminal connection status such as television set.Now signal source selecting switch is selected
Dout as DAC input signal.
When the state of control module is the connection of the terminals such as no television set, now signal source selecting switch selection d conducts
DAC input signal.Because d value is equal with the minimum level of the line synchronising signal of TV signal.The judgement threshold of control module
Value is constant.If ADC sampled values are more than threshold value, the state of control module keeps the terminal connection status such as no television set.This
When signal source selecting switch keep selection d as DAC input signal.If ADC sampled values are less than threshold value, control module
State, which enters, the terminal connection status such as television set.Now signal source selecting switch selects dout as DAC input signal.
Because when no terminal is connected with equipment, DAC input signal is d, and DAC output current value is more normal than exporting
Current value during TV signal is low, also just reduces the power consumption of circuit, and because DAC is output as constant current, will not be as output
The electric current of exporting change disturbs so as to be produced to circuit other parts during normal tv signal.
The all or part of circuit in the present invention can be realized by way of integrated circuit, can also pass through discrete member
Part is realized.
The present invention can be decreased or turned off this useless signal automatically, it is possible to reduce the energy consumption of equipment, reduce in equipment
The interference in portion, improves the performance of equipment, increases the service life of equipment.
Brief description of the drawings
Fig. 1 is circuit structure schematic diagram；
Fig. 2 is the waveform schematic diagram of TV signal.
Embodiment
Fig. 1 is circuit structure schematic diagram, and dout therein is the digital tv signal to be exported, and a is control module, b
It is low level signal, c is signal source selecting switch, and d is DAC, and e is ADC, and f is load resistance；Signal source selecting switch is according to control
Exporting for molding block selects input signal or low level signal to DAC；DAC output is sampled by ADC；The signal of ADC samplings is sent
Enter control module；The control of signal source selecting switch is produced after the signal operation that control module is sampled according to input signal and ADC
Signal.
Fig. 2 is that the OH in the waveform schematic diagram of TV signal, Fig. 2 is row lock in time basic point, and a is horizontal blanking impulse, and d is
Horizontal synchronizing pulse, h is chrominance carrier.
When there is television terminal to be connected with picture output device, the equivalent output loading of output equipment is 37.5 ohm；
When not having the television terminal to be connected with picture output device, the equivalent output loading of output equipment is 75 ohm.Due to different shapes
DAC output control word is identical under state, so DAC output level is proportional to equivalent load resistance.The output level passes through ADC
Sampling returns to control module.When DAC exports row sync level, with during 75 ohm of equivalent loads and 37.5 ohm of equivalent loads
When ADC sampled values median be control module decision threshold.During adjudicating, if ADC sampled value is more than judgement
Threshold value, then it is assumed that equivalent load is that 75 ohm, i.e. video frequency output are not connected with the terminal such as TV；If ADC sampled value is small
In decision threshold, then it is assumed that equivalent load is that the terminals such as 37.5 ohm, i.e. video frequency output and TV are connected.Because TV signal exists
Keep constant during row synchronization, thus when the state of control module be with terminal be connected when judgement be only expert at it is synchronous during carry out.
It is in office because the value of DAC control word is constantly equal to row sync level when the state of control module is not attached to terminal
The meaning moment all makes decisions.
Because row sync level is the minimum levels of TV signal, the size of control module comparator input signal be understand be
It is no be in row synchronization during.
In order to ensure that original state does not influence to watch TV, the upper electric default setting of control module is connected with terminal.
It should be understood that examples detailed above is the description of the invention, rather than limitation of the present invention, it is any not surpass
The innovation and creation gone out in the range of true spirit, each fall within protection scope of the present invention.
Claims (1)
1. a kind of TV signal output circuit of automatic detection terminal connection, it, which is comprised at least, a digital analog converter,
One analog-digital converter, a control module, a low level signal and signal source selecting switch；It is characterized in that described
Digital tv signal and the low level signal of output be connected to the signal input part of signal source selecting switch, control module
Output is connected to the selection control end of signal source selecting switch；The output of described signal source selecting switch is connected to digital simulation
The input of converter, the output end of described digital analog converter and 75 ohmic load resistances and analog-digital converter
Input is connected；The digital tv signal of the output and output of described analog-digital converter is connected to control module
Input；
When the TV output socket of equipment be not inserted into cable or insert the other end of cable but cable without and television terminal
When being connected, described digital analog converter exports constant low current；When equipment TV output socket by cable with
When television terminal is connected, described digital analog converter exports normal anolog TV signals；
When device power-up, the default setting of control module is has television terminal connection, when the state of control module is that have electricity
When being connected depending on machine terminal, control module judges whether into sync level of the entering a profession defeated moment according to input signal；It is same when entering to enter a profession
Level output time is walked, control module is judged ADC sampled values；It is defeated under 75 ohm of equivalent loads with DAC
It is threshold value to go out level with the median of output levels of the DAC under 37.5 ohm of equivalent loads；If ADC sampled values
During more than threshold value, the state of control module, which enters, does not have television terminal connection status；Now signal source selecting switch selection is low
Level signal b as DAC input signal；The minimum level phase of the value of low level signal and the line synchronising signal of TV signal
Deng；If ADC sampled values are less than threshold value, the state of control module maintains television terminal connection status, now signal source
Selecting switch selects the digital tv signal dout of output as DAC input signal；
When the state of control module is no television terminal connection, now signal source selecting switch selects low level signal b
It is used as DAC input signal, because d value is equal with the minimum level of the line synchronising signal of TV signal, control module
Decision threshold it is constant；If ADC sampled values are more than threshold value, the state of control module keeps no television terminal to connect
State is connect, now signal source selecting switch keeps selection low level signal b as DAC input signal, if ADC samples
When value is less than threshold value, the state of control module, which enters, television terminal connection status, and now signal source selecting switch selection is defeated
The digital tv signal dout gone out as DAC input signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310747712.5A CN103731614B (en) | 2013-12-31 | 2013-12-31 | The TV signal output circuit and detection method of a kind of automatic detection terminal connection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310747712.5A CN103731614B (en) | 2013-12-31 | 2013-12-31 | The TV signal output circuit and detection method of a kind of automatic detection terminal connection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103731614A CN103731614A (en) | 2014-04-16 |
| CN103731614B true CN103731614B (en) | 2017-07-14 |
Family
ID=50455524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201310747712.5A Active CN103731614B (en) | 2013-12-31 | 2013-12-31 | The TV signal output circuit and detection method of a kind of automatic detection terminal connection |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN103731614B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106303514B (en) * | 2016-09-08 | 2019-01-04 | 珠海全志科技股份有限公司 | Analog video interface detection circuit and its detection method, integrated chip |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1774080A (en) * | 2004-11-12 | 2006-05-17 | 上海乐金广电电子有限公司 | Input signal detecting equipment and method |
| CN201039354Y (en) * | 2007-04-29 | 2008-03-19 | 青岛海信电器股份有限公司 | A low-power consumption circuit |
| CN101990071A (en) * | 2009-07-29 | 2011-03-23 | 晨星软件研发(深圳)有限公司 | Demodulator and method capable of automatically calibrating output and television receiver thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8902365B2 (en) * | 2007-03-14 | 2014-12-02 | Lance Greggain | Interference avoidance in a television receiver |
-
2013
- 2013-12-31 CN CN201310747712.5A patent/CN103731614B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1774080A (en) * | 2004-11-12 | 2006-05-17 | 上海乐金广电电子有限公司 | Input signal detecting equipment and method |
| CN201039354Y (en) * | 2007-04-29 | 2008-03-19 | 青岛海信电器股份有限公司 | A low-power consumption circuit |
| CN101990071A (en) * | 2009-07-29 | 2011-03-23 | 晨星软件研发(深圳)有限公司 | Demodulator and method capable of automatically calibrating output and television receiver thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103731614A (en) | 2014-04-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106303514B (en) | Analog video interface detection circuit and its detection method, integrated chip | |
| CN104506859A (en) | Television core test circuit and system | |
| CN102945010B (en) | Method and device for realizing automatic switching of sound source | |
| CN102075720B (en) | Device and method for detecting plug wire at video output port and video play device | |
| EP2723059A2 (en) | Method and device for determining type of video signal to be output | |
| CN103731614B (en) | The TV signal output circuit and detection method of a kind of automatic detection terminal connection | |
| CN102932683A (en) | Mobile high-definition link (MHL) realizing method and video playing device | |
| US20110157372A1 (en) | Multimedia apparatus having function of detecting video signal connection | |
| CN111435147B (en) | Switching device capable of automatically detecting and adjusting zero phase | |
| CN102624957B (en) | Detection system for earphone drive-by-wire button of mobile phone | |
| CN104284112A (en) | Video output system with load detecting device and detecting method thereof | |
| CN201191895Y (en) | Automatic multi-group HDMI audio and video signal switch | |
| CN110187267B (en) | Single-phase three-wire intelligent ammeter relay state detection circuit and method | |
| US20130155258A1 (en) | Determination circuit | |
| CN202095048U (en) | Intelligent detection circuit | |
| CN101277403B (en) | Circuit and method for switching video signal of digital television receiver | |
| CN205249374U (en) | Television signal source automatic switching control equipment | |
| CN201797559U (en) | Set-top box capable of automatically switching audio interface and video interface | |
| CN202121700U (en) | Automatic signal source detection circuit for television set | |
| CN203480829U (en) | Analog audio signal self-check system | |
| CN103167219B (en) | CVBS TV signal clipping control unit structure | |
| CN103209346B (en) | Noise controller | |
| CN101778196B (en) | Multimedia device | |
| CN102602346A (en) | Method for automatically switching audio and video signals of bus | |
| CN100488241C (en) | Input voltage decision device and voltage value range decision method used for it |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |