KR20100047383A - Transmitting circuit of power line communication modem for cctv - Google Patents

Abstract

PURPOSE: A transmitting circuit of power line communication modem for CCTV is provided to embody modulation unit and oscillation unit for a video modulation in the power line communication modem, thereby simplifying a circuit configuration. CONSTITUTION: A transistor(TR1) amplified a video signal from a monitoring camera. A variable resistor(VR2) adjusts DC(Direct Curren) bias voltage over a predetermined voltage. The DC bias voltage is applied to amplification end output of the transistor. An OSC modulates the video signal to oscillation frequency. A transformer(T1) transforms the modulated video signal output to AC(Alternating Current) video signal.

Description

Transmitting circuit of power line modem for surveillance cameras {Transmitting circuit of power line communication MODEM for CCTV}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surveillance camera device of a power line communication method, and more particularly, to a transmission circuit of a power line modem used for a surveillance camera (CCTV) of a power line communication (PLC) system.

In general, in security systems that are built for the purpose of crime prevention or disaster prevention, or automation systems that want to pursue convenience of life by automatically or remotely controlling indoor electronic devices, surveillance cameras are installed indoors and outdoors to monitor the surroundings in real time. It is used.

Such a surveillance camera has an image capturing function and a transmission function, and photographs and transmits an image of a surrounding, and transmits the image transmitted from the surveillance camera to a predetermined designated display device for monitoring.

1 is a schematic configuration diagram of a surveillance camera device according to the related art.

Referring to FIG. 1, a surveillance camera device according to the related art is a CCD (Charge Coupled Device) camera 10 as an image pickup device that converts an optical signal of an object into an electrical signal from a lens that enlarges and transmits a light source of an object. It is provided.

The CCTV camera 10 is a commercial AC power supplied from the outside, for example, AC 220V (30) by the rectification and processing functions such as AC / DC conversion, DC / DC conversion, the CCD camera 10 A power supply unit (not shown) that provides an operating power required for the operation, an imaging unit (not shown) that operates by receiving power from the power supply unit, and photographs an image, and operates by receiving power from the power supply unit. It may include a transmission unit (not shown) for transmitting the image signal photographed from the unit to the designated image display unit 20, wherein the power connector is connected to the input of the power supply and the signal connector connected to the output of the transmitter Each connector is provided.

In the case of the transmission unit of the surveillance camera according to the prior art, it can be divided into a wired transmission and a wireless transmission according to the transmission method, in general, CCTV cameras, because they are used for a limited purpose in a limited space, a lot of wired transmission method Used. In fact, the radio transmission scheme has many limitations due to radio frequency allocation problems and interference problems. And even in the wired transmission method, a baseband transmission method for transmitting a video signal as it is, a carrier transmission method for modulating and transmitting a video signal, a PCM transmission method for converting an image signal into a PCM, and an optical signal. Various methods such as optical communication transmission methods for converting signals are used, but all of these transmission methods must use coaxial cables or optical cables for signal transmission. Therefore, it is difficult to install and manage such a coaxial cable for transmitting a video signal, and the cost is increased.

As described above, the conventional surveillance cameras installed in indoor and outdoor remote areas require a separate data line 40, which is a signal transmission line, and a power line 50, which is a power supply line. In particular, in the case of video signal transmission, the cost is high because a coaxial cable that is expensive than a general data line must be used.

On the other hand, recently, a power line communication (PLC) technology has been developed that can transmit voice and text data, video, etc. using only an electrical outlet, that is, a power line, and this power line communication can be installed using an existing optical communication cable. In addition to the low cost, it also has the advantage that it costs little to no communication.

2 is a schematic configuration diagram of a surveillance camera device of a power line communication method according to the related art.

As shown in FIG. 2, the monitoring camera apparatus of the power line communication method according to the related art can supply power and transmit signals only by the power line 50 by using the power line communication method described above. At this time, to enable this, the CCD camera 10 and the image display unit 20 are each provided with a power line modem.

As a first prior art for solving the problem of a surveillance camera according to the prior art, Korean Patent Application No. 2000-32364 (filed date: June 13, 200) is named "camera with a power line communication modem" The invention of is disclosed. According to the first prior art, by embedding the power line communication modem in the CCD camera to transmit the video signal and the control signal of the CCD camera to another system using a power line, data transmission is possible without installing a data transmission cable separately Do.

In the case of the power line communication modem embedded in such a CCD camera, the transmission circuit is configured such that an image modulator is necessary. However, the transmission circuit of the power line communication modem according to the related art has a problem in that the circuit structure is complicated as the modulation unit and the oscillation unit are separately configured for image modulation.

The technical problem to be solved by the present invention is to provide a power line communication camera of the surveillance camera device, the power line for the surveillance camera that can simplify the circuit configuration by implementing a modulator and an oscillator for image modulation at the same time. To provide a modem transmission circuit.

As a means for achieving the above-described technical problem, the transmission circuit of the power line modem for surveillance camera according to the present invention, in the transmission circuit of the power line modem of the surveillance camera using the power line communication method, the first bandwidth provided from the surveillance camera. A transistor TR1 for amplifying and outputting a video signal; A variable resistor VR2 for adjusting a DC bias voltage applied to the amplification stage output of the transistor TR1 to a predetermined voltage or more; An oscillator (OSC) having an oscillation frequency having a second bandwidth and directly connected to a terminal voltage applied to an output of the amplifier stage of the transistor TR1 and modulating the image signal to the oscillation frequency and outputting the oscillation frequency; And a transformer T1 for converting the video signal output modulated in the oscillation frequency band by the oscillator into an AC (AC) video signal.

Here, the image signal converted into the alternating current output from the transformer T1 is transmitted to the image display unit through an AC power line.

Here, the oscillator OSC starts oscillation from the adjusted bias voltage, and simultaneously modulates and oscillates the image signal.

The variable resistor VR2 adjusts the DC bias voltage applied to the amplification stage output of the transistor TR1 to be 2.6V or more.

The oscillator OSC has an oscillation frequency having a second bandwidth of 20 MHz, and modulates and outputs an image signal having a first bandwidth in a range of 15.74 kHz to 4 MHz according to the oscillation frequency at 20 MHz. It features.

On the other hand, as another means for achieving the above technical problem, the transmission circuit of the power line modem for surveillance camera according to the present invention is 15.74 provided from the surveillance camera in the power circuit modem transmission circuit of the surveillance camera using the power line communication system. A transistor TR1 for amplifying and outputting an image signal having a bandwidth in the range of kHz to 4MHz; A variable resistor VR2 for adjusting a DC bias voltage applied to the amplification stage output of the transistor TR1 to 2.6 V or more; An oscillation frequency having a 20 MHz bandwidth, directly connected to the terminal voltage applied to the output of the amplifying stage of the transistor TR1, and starting the oscillation from the bias voltage adjusted to 2.6 V or more, An oscillator (OSC) for modulating and outputting at an oscillation frequency; And a transformer (T1) for converting the video signal output modulated to the 20 MHz oscillation frequency band by the oscillator to an AC (AC) video signal, wherein the oscillator is configured to oscillate from the bias voltage adjusted to 2.6 V or more. And perform image signal modulation and oscillation simultaneously.

According to the present invention, in a power line communication modem of a surveillance camera device, a circuit configuration can be simplified by simultaneously implementing a modulator and an oscillator for image modulation. Accordingly, by integrating various cables necessary for the installation of a CCTV camera or web camera for CCTV into a power line, by simply configuring an image modulation circuit, manufacturing and installation costs are reduced, and maintenance and repair are easy.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

First, referring to FIGS. 3 and 4, the principle of power line communication (PLC) and a method of combining a power line and an image signal will be briefly described.

3 is a view for explaining the principle of power line communication (PLC), Figure 4 is a view for explaining a method of combining the power line and the image signal.

Referring to FIG. 3, power line communication (PLC) uses a frequency-division multiplexing (FDM) principle in which a power line is used as a communication line to multiplex and transmit power and communication signals simultaneously. And multiplexing a communication signal which is a high frequency signal in the range of several tens of kilohertz to several tens of MHz.

For example, a communication signal transmitted from a PLC modem on the transmitting side is multiplexed with a 60 GHz AC power supply via a high pass filter, transmitted via a power line, and then 60 ㎐ AC power supply from the PLC modem on the receiving side. Can be output from the image display unit, that is, the monitor.

In addition, if the communication method of securing the communication reliability of the power line and does not affect the quality of the power source is applied, by using the power outlet as a communication terminal, it is possible to use the communication network anywhere and conveniently.

Referring to FIG. 4, the combination of the power line and the image signal mainly uses capacitive coupling and may be used together with an inductor. If the modem is directly connected to the power line to transmit and receive data through the current commercial power line 200 of 220V AC / 60㎐, the modem may be damaged, and thus the power line coupling capacitor may be used to prevent 220V AC / 60㎐. You can insert In addition, a power line coupling circuit may be implemented by inserting a large inductor so that a power line communication carrier can be transmitted well. For example, the circuit shown in FIG. 4 is a coupling circuit in which a capacitor having a capacity of 0.10 mA / 250 V AC and an inductor of 1 mH are connected in series, and the input impedance seen by 220 V AC / 60 Hz is about. It can be seen as large 25 kHz to protect the power line modem.

In addition, for the coupling of the power line and the video signal, it is desirable to have a high impedance at the time of reception with respect to the communication frequency or to have a low frequency at the time of transmission with respect to the transmission frequency.

On the other hand, according to an embodiment of the present invention, in the power line communication modem of a surveillance camera device, there is provided a transmission circuit of a power line modem for a surveillance camera that can implement a modulator and an oscillator for image modulation at the same time.

5 is a schematic configuration diagram of a surveillance camera device having a power line modem according to an embodiment of the present invention.

Referring to FIG. 5, a surveillance camera device having a power line modem according to an embodiment of the present invention includes a CCD camera 100, a power line modem 110, a power line 200, an image display unit 300, and a power line modem 310. ) And a commercial AC power source 400, wherein the transmission circuits of the power line modems 110 and 310 are simultaneously implemented with an oscillator and modulation for image modulation, which will be described below with reference to FIG. 6.

In the embodiment of the present invention, the power line modems 110 and 310 include both a transmitting circuit and a receiving circuit, respectively, but only the case of being transmitted from the CCD camera 100 to the image display unit 300 will be described. In other words, when the transmission from the image display unit 300 to the CCD camera 100, only the transmitting circuit and the receiving circuit need be changed, so a description thereof will be omitted. That is, the power line modem 110 of the CCD camera 100 represents a transmission circuit, and the power line modem 310 of the image display unit 300 will be described as considering the reception circuit.

6 is a diagram illustrating a transmission circuit of a power line modem for surveillance camera according to an embodiment of the present invention.

Referring to FIG. 6, the transmitting circuit 110 of the power line modem for surveillance camera according to the embodiment of the present invention includes a first variable variable resistor VR1, a second variable resistor VR2, a first transistor TR1, The first resistor R1, the oscillator 111, the first capacitor C1, the first transformer T1, the second capacitor C2, and the third capacitor C3 are included.

The transmission circuit 110 of the power line modem for surveillance camera according to the embodiment of the present invention, the output of the video signal (s1) of the CCD camera 100 for CCTV outputs the amplification stage of the transistor TR1, that is, the first resistor (R1) By directly connecting the terminal voltage applied to the oscillator (Oscillator (OSC) 111) to implement a conventional complex modulation and oscillation at the same time.

That is, when the output of the image signal s1 of the CCD camera 100 is input to the base terminal of the transistor TR1 via the first variable variable resistor VR1, the image signal s1 is connected between the collector and the base of the transistor TR1. 2 Adjust DC bias voltage with variable resistor VR2. Thereafter, the adjusted DC bias voltage is adjusted to apply a predetermined voltage, for example, 2.6V or more, to the first resistor R1.

Accordingly, the 20 MHz oscillator 111 oscillates from about 2.6 V, and outputs a CCTV video output, such that a video signal having a bandwidth of about 15.74 Hz to 4 MHz is modulated into the 20 MHz band of the oscillator 111. The video modulator can be configured simply. That is, the oscillator 111 starts oscillation from the adjusted bias voltage, and simultaneously performs image signal modulation and oscillation. Although the oscillator 111 has been described as having an oscillation frequency of 20 MHz according to an embodiment of the present invention, it is not limited thereto, and it will be apparent to those skilled in the art that they may vary.

Subsequently, an output is applied to the first transformer T1 through the first capacitor C1 so that an image signal of AC 86V to 264V ranges on the AC power line 200 via the high voltage capacitors C2 and C3.

Therefore, the image signal converted into alternating current output from the first transformer T1 is transmitted to the image display unit 300 through the AC power line 200.

As a result, the oscillation and modulation are simultaneously performed by the oscillator 111 in the transmission circuit of the power line modem for surveillance camera according to the embodiment of the present invention, so that the transmission circuit can be simply configured.

7 is a diagram illustrating a receiving circuit of a power line modem for surveillance camera according to an embodiment of the present invention.

Referring to FIG. 7, the reception circuit of the power line modem for surveillance camera according to the embodiment of the present invention may be configured in the same manner as a general receiver, and the image signal of the AC 86V to 264V range transmitted through the power line 200. Is a high frequency component induced in the second transformer T2 via the fourth and fifth high voltage capacitors C4 and C5, for example, in the video amplifier U1 311 configured as an integrated circuit. In the VC1 and the intermediate frequency transformer IFT1, only a specific frequency, that is, a frequency transmitted from the aforementioned transmission circuit of FIG. 5 is tuned.

At the same time, the low frequency signal rectified by the rectifying diode D1 and filtered by the sixth capacitor C6, that is, the image signal, is amplified by the video amplifier U2 312, and the second resistor R2 and the seventh capacitor After passing through C7, the image display 300 may be output to the monitor.

As a result, the transmission circuit of the power line modem for surveillance cameras according to the embodiment of the present invention can implement a conventional complex modulation and oscillation at the same time by directly connecting the terminal voltage applied to the output of the amplifying stage of the CCTV camera image signal output to the oscillator. .

In addition, although the transmission circuit of the power line modem according to the embodiment of the present invention has been described for a surveillance camera, it is obvious to those skilled in the art that the present invention can be applied to the power line modem for other purposes without being limited thereto.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

1 is a schematic configuration diagram of a surveillance camera device according to the related art.

2 is a schematic configuration diagram of a surveillance camera device of a power line communication method according to the related art.

3 is a diagram for explaining the principle of power line communication (PLC).

4 is a view for explaining a method of combining a power line and an image signal.

5 is a schematic configuration diagram of a surveillance camera device having a power line modem according to an embodiment of the present invention.

6 is a diagram illustrating a transmission circuit of a power line modem for surveillance camera according to an embodiment of the present invention.

7 is a diagram showing a receiving circuit of a power line modem for surveillance camera according to an embodiment of the present invention.

<Brief Description of Drawings>

100: surveillance camera (CCD) 110: power line modem

111: oscillator 200: power line

300: video display unit 310: power line modem

311, 312: video amplifier

VR1: first variable resistor VR2: second variable resistor

TR1: first transistor T1: first transformer

T2: second transformer VC1: variable capacitor

IFT1: Intermediate Frequency Transformer

C1 to C7: capacitors R1 and R2: resistors

D1: rectifier diode

Claims (6)

A transmission circuit of a power line modem of a surveillance camera using a power line communication system, A transistor TR1 for amplifying and outputting an image signal having a first bandwidth provided from a surveillance camera; A variable resistor VR2 for adjusting a DC bias voltage applied to the amplification stage output of the transistor TR1 to a predetermined voltage or more; An oscillator (OSC) having an oscillation frequency having a second bandwidth and directly connected to a terminal voltage applied to an output of the amplifier stage of the transistor TR1 and modulating the image signal to the oscillation frequency and outputting the oscillation frequency; And Transformer (T1) for converting the video signal output modulated in the oscillation frequency band by the oscillator to AC (AC) video signal Transmission circuit of the power line modem for surveillance cameras comprising a. The method of claim 1, And the video signal converted into alternating current output from the transformer (T1) is transmitted to an image display unit through an AC power line. The method of claim 1, And the oscillator (OSC) starts oscillation from the adjusted bias voltage, and simultaneously performs video signal modulation and oscillation. The method of claim 3, And said variable resistor (VR2) adjusts the DC bias voltage applied to the amplifying stage output of said transistor (TR1) to be 2.6V or more. The method of claim 3, The oscillator OSC has an oscillation frequency having a second bandwidth of 20 MHz, and modulates and outputs an image signal having a first bandwidth of 15.74 kHz to 4 MHz at 20 MHz according to the oscillation frequency. A transmission circuit for a power line modem for surveillance cameras. A transmission circuit of a power line modem of a surveillance camera using a power line communication system, A transistor TR1 for amplifying and outputting an image signal having a bandwidth in the range of 15.74 kHz to 4 MHz provided from the surveillance camera; A variable resistor VR2 for adjusting a DC bias voltage applied to the amplification stage output of the transistor TR1 to 2.6 V or more; An oscillation frequency having a 20 MHz bandwidth, directly connected to the terminal voltage applied to the output of the amplifying stage of the transistor TR1, and starting the oscillation from the bias voltage adjusted to 2.6 V or more, An oscillator (OSC) for modulating and outputting at an oscillation frequency; And A transformer (T1) for converting an image signal output modulated in the 20 MHz oscillation frequency band by the oscillator into an AC (AC) image signal Including; And the oscillator starts oscillation from the bias voltage adjusted to 2.6 V or higher, and simultaneously performs video signal modulation and oscillation.

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