GB2307607A

GB2307607A - Switching between aerial and VCR rf sources by selectively energizing an amplifier or a modulator

Info

Publication number: GB2307607A
Application number: GB9616733A
Authority: GB
Inventors: Jong Jin Lee
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 1995-11-23
Filing date: 1996-08-09
Publication date: 1997-05-28
Anticipated expiration: 2016-08-09
Also published as: KR100206371B1; KR970032019A; GB2307607B; DE19635228A1; DE19635228C2; GB9616733D0

Description

2307607 POWER SWITCHING CIRCUIT OF RADIO FREQUENCY MODULATOR FOR PAL

SYSTEM

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a power switching circuit of RF modulator for PAL system, and more particularly to a power switching circuit of RF modulator for PAL system for cutting off the RF signal of air broadcasting upon viewing VCR which unnecessarily flows into TV set by cutting off the supply of bias power of second amplifying section is among booster voltages upon viewing VCR.

2. Prior Art

In general, RF modulator used for VCR, CATV, or game machine and the like requiring a RF modulator consists of RF booster section, RF modulating section and a mixer, and the RF booster section amplifies RF signal of air channel inputted from antenna and then a part of which is distributed to VCR interior tuner, while other part of which is distributed to TV set 1 through a mixer. The RF modulator section modulates audio/video carrier signal whereby outputs to TV set through the mixer.

A structure for prior art technique in relation to general technique is shown in FIG.1 and FIG.2, and firstly reviewing FIG.1, the RF signal of air broadcasting channel received by antenna ANT is amplified for first stage at first RF amplifying section 1 and then f ed to a distributor 2. The distributor 2 distributes a part of RF signal of the air broadcasting channel to interior tuner of VCR for f eeding to recorder or other set, another part is distributed to second RF amplifying section 3. The RF signal amplified in two stages at the second RF is amplifying section 3 is outputted to TV set through the mixer 4. On the other hand, audio/video carrier signal (Ain, Vin) of VCR interior is modulated to RF signal at RF modulating section 5 and then outputted to TV set through the mixer 4 whereby reproduced.

Wherein, the first and second RF amplifier sections 1, 3 are operated by always applied booster voltage Bl+, and a modulating voltage B2+ is applied to a RF modulating section 5, and this modulating voltage B2+ appears only at a time upon modulating of audio/video carrier signal. An object of always applying the booster voltage Bl+ is either for providing a recordable state in case of viewing the VCR, or for providing the air broadcasting signal to other set, and accordingly the first RF amplifying 5 section 1 always requires power.

However, the prior art RF booster section shown in FIG.1 as above, regardless of whether or not executing the modulation of audio/video carrier signals Ain, Vin at RF modulating section 5 according to generation of modulating voltage B2+, always amplifies the RF signal of the air broadcasting channel and outputs through the mixer 4. Accordingly, in case of viewing the VCR, the RF signal modulated at the RF modulating section 5 is outputted to the mixer

4, and at this moment, since the RF signal of the air broadcasting channel inputted from the antenna influences severe interference to the RF signal modulated upon viewing the VCR, a good quality picture could not be obtained upon viewing the VCR, and there has been a problem that consuming power becomes increased due to always supplied booster voltage.

And, a structure disclsed in Japanese utility model publication Hei-631816 is shown in FIG.2, and reviewing FIG.2, prior art another RF signal selection outputting circuit, in a RF signal selection - 3 outputting circuit comprising a first input terminal for inputting a first RF signal, a first transmitting path for transmitting the first RF signal to output terminal, a second transmitting path for transmitting second RF signal outputted from RF modulator to the output terminal, a switching means provided at the first and second transmitting paths for selectively outputting the first and second RF signals to the output terminal, and a filter means for eliminating RF component of the second RF signal provided at second transmitting path, includes the switching means by the switching diode provided at the second transmitting path between the filter means and the output terminal, and at the same time, applies a bias to the diode by applying a signal inputted from the video output terminal and the audio output terminal of the RF modulation IC to the second transmitting path than the prior stage of the filter means.

Above described prior art technique is a 20 technique for directly switching the signal transmitting line, and in the prior art technique shown in FIG.2 as these, an improvement point and problem against prior art technique for which the present invention intends to solve, were the problems that since a separate control power was required other 4 - than the bias power for switching the signal transmitting line, the modulator circuit related to a separate control voltage supply becomes complicated, and the consuming power becomes bigger.

OBJECT AND SUMMARY OF THE INVENTION

Therefore, the present invention is invented to solve above describe problems and to attain improving points. Accordingly, it is an object of the present invention to provide a power switching circuit of RF modulator f or PAL system f or making the VCR viewing picture to be improved better by cutting off that RF signal of air broadcasting is fed to the TV set upon viewing VCR by cutting of f the bias power supply of second amplifying section among the booster voltages upon viewing VCR.

Another object of the present invention is to provide a power switching circuit of RF modulator for PAL system for making to prevent extravagance of excessive consuming power by making to selectively supply the modulating voltage being a bias power of RF modulating section, and the booster voltage being a bias power of the first and second amplifying sections 31, 33.

A technical subject intended by the present invention is to solve the prior art problems and to accomplish improving points, and as a technical means for achieving such technical subject, the power switching circuit of RF modulator for PAL system of the present invention comprises: in a RF modulator comprising a first RF amplifying section for firstly amplifying the RF signal inputted to antenna ANT by applying the booster voltage, a distributing section for distributing the RF signal amplified at the first RF amplifying section 31 respectively to VCR interior tuner and to the second RF amplifying section, a second RF amplifying section for secondly amplifying the RF signal from the distributing section by applying the booster voltage, a RF modulating section for modulating audio/video carrier signal by applying the modulation voltage, and a mixer for outputting an output signal of the second RF amplifying section or an output signal of RF modulating section to TV set; a power supply section of VCR set made to selectively supply the modulating voltage being a bias power of the RF modulating section and the booster voltage being a bias power of the first and second amplifying sections; and a power switching circuit made to 6 - execute a dividing function between the modulating voltage and the booster voltage and at the same time to supply the modulating voltage to the first amplifying section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a block diagram showing a structure of prior art RF modulator,

FIG.2 is a block diagram showing a structure of another prior art RF modulator,

FIG.3 is a block diagram showing a structure of RF modulator in accordance with the present invention, and FIG.4 is a realistic diagram showing a preferred embodiment of a power switching circuit shown in FIG.3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the power switching circuit of RF modulator for PAL system in accordance with the present invention will be described more in detail with reference to the accompanying drawings.

- 7 FIG.3 is a block diagram showing a structure of the RF modulator in accordance with the present invention, and reviewing FIG. 3, the power switching circuit of RF modulator for PAL system of the present invention comprises: a f irst RF amplifying section 31 for firstly amplifying the RF signal inputted to antenna ANT by applying the booster voltage, a distributing section 32 for distributing the RF signal amplified at the first RF amplifying section 31 respectively to VCR interior tuner and to the second RF amplifying section 33, a second RF amplifying section 33 for secondly amplifying the RF signal from the distributing section 32 by applying the booster voltage Bl+, a RF modulating section 35 for modulating audio/video carrier signal Ain, Vin by applying the modulation voltage B2+ , and a mixer 34 for outputting an output signal of the second RF amplifying section 33 or an output signal of RF modulating section 35 to TV set.

And, it comprises: a power supply section (not shown) of VCR set SET made to selectively supply the modulating voltage B2+ being a bias power of the RF modulating section 35 and the booster voltage Bl+ being a bias power of the first and second amplifying sections 31, 32; and a power switching circuit 40 made to execute a dividing function between the modulating voltage B2+ and the booster voltage Bl+ and at the same time to supply the modulating voltage B2+ to the first amplifying section 31. That is, it comprises a power supply section (not shown) made by SMPS contained within the VCR set SET so as not to be supplied with booster voltage Bl+ during the modulation voltage B2+ is supplied only at a time ofexecuting the modulation of the audio/video carrier signal Ain, Vin at the RF modulating section 35, on the contrary, so as not to be supplied with the modulation voltage B2+ during the booster voltage BI+ is supplied.

FIG.4 is a realistic diagram showing a preferred embodiment of the power switching circuit 40 shown in FIG.3, and reviewing FIGA, the power switching circuit 40 includes: a first diode D1 which connects the booster voltage Bl+ terminal to anode terminal and connects its cathode terminal to first RF amplifying section 31, and a second diode D2 which connects anode terminal to a line in which the modulation voltage B2+ is supplied to the RF modulating section 35 and connects its cathode terminal to a cathode terminal of the first diode D1.

Operation according to the circuit of the present 9 - invention constructed as these will be described more in detail with reference to the accompanying drawings.

Reviewing FIG.3 and FIGA, firstly in case of viewing the air broadcasting (television broadcasting), only a booster voltage Bl+ is supplied from the VCR set SET according to the air broadcasting selection, and the modulation voltage B2+ is not supplied. In case where only a booster voltage Bl+ is supplied from the power supply section of the VCR set, the booster voltage Bl+ is supplied to the first RF amplifying section 31 through the f irst diode D1 of the power switching circuit 40 shown in FIG.4 and at the same time it is directly supplied also to the second RF amplifying section 33. Wherein, the first is diode D1 is made to a conductive state by the booster voltage Bl+, whereby the booster voltage Bl+ is supplied to the first amplifying section 31.

Thus, since the booster voltage Bl+ is supplied to the first and second RF amplifying sections, the first and second amplifying sections become to normally execute the amplifying operation, according to this, the RF signal of the air broadcasting channel received to the antenna ANT is fed to the distributing section 32 after being amplified in first stage at the first RF amplifying section 31, and at the - Ar- is distributing section 32. a part of the RF signal of the air broadcasting channel is distributed to an interior tuner of VCR while another part is distributed to the second RF amplifying section 33.

And, the RF signal amplified at the second RF amplifying section 33 is outputted to the TV set through the mixer 40. Thus, when the air broadcasting is selected, since the booster voltage is supplied from the power supply section of the VCR set, the air broadcasting can normally be viewed through above process.

On the other hand, in case of viewing the playback of VCR, only the modulation voltage B2+ is supplied from the power supply section of the VCR set according to VCR playback selection, and the booster voltage Bl+ is not supplied. In case where only the modulation voltage B2+ is supplied from the power supply section of the VCR set. the modulation voltage B2+ is supplied to the RF modulating section 35 through the power switching circuit 40 shown in FIG.4.

Accordingly, the RF modulating section 35 becomes to execute a normal operation by the modulation voltage B2+ whereby modulates the playback video/audio signals vin, Ain to RF signal at the RF modulating section 35 and then it is supplied to the TV set 11 - through the mixer 34. Thus, when the VCR playback is selected, since the modulation voltage is supplied from the power supply section of the VCR set, the VCR playback can be normally viewed through above described process. And, different from prior art method in which the booster voltage is always supplied, since the booster voltage is not supplied at a time of supplying the modulation voltage in the present invention, the consuming power becomes greatly decreased.

At the same time with these, the modulation voltage B2+ is also supplied to the first RF amplifying section 31 through the second diode D2 of the power switching circuit 40 shown in FIG.4, and according to this, the first RF amplifying section 31 amplifies and outputs also the RF signal of the air broadcasting similarly with prior art. On the contrary, while the modulation voltage B2+ is supplied to the first RF amplifying section 31, since a supply of the power is none at the second RF amplifying section 33, a signal outputted from the second RF amplifying section 33 is none. and according to this. the signal modulated at the RF modulating section 35 is outputted to the TV set through the mixer 34 without interference by the RF signal of the air broadcasting.

In accordance with the present invention as described above, the VCR viewing picture screen is improved better by completely cutting off the flowing in of RF signal of the air broadcasting channel by VCR playback RF signal which has caused problems heretofore upon viewing the VCR with satisfying a condition always supplying the power to the first RF amplifying section.

And, in other effects according to the present invention, extravagance of excessive consuming power is prevented by selectively supplying the booster voltage being a bias power of the first and second amplifying section 31, 33, and the first and second diodes D1, D2 of the power switching circuit 40 executes also a function for dividing the power voltage between the modulation voltage B2+ terminal and the booster voltage Bl+ terminal.

Above explanation is nothing but the explanation for an embodiment of the present invention, and the invention is possible to variously changed or remade within extent of its construction. And, it can be easily known by those who has ordinary knowledge in this field of art that a detailed circuit of the power switching circuit is not limited to the embodiment

13 - described above and it can be substituted by a switching element or a switch.

is - 14

Claims

What is claimed is:

1. In a RF modulator for PAL system comprising a first RF amplifying section for firstly amplifying the RF signal inputted to antenna ANT by applying the booster voltage, a distributing section for distributing the RF signal amplified at the first RF amplifying section respectively to VCR interior tuner and to the second RF amplifying section, a second RF amplifying section for secondly amplifying the RF signal from the distributing section by applying the booster voltage Bl+, a RF modulating section for modulating audio/video carrier signal Ain, Vin by applying the modulation voltage B2+, and a mixer for outputting an output signal of the second RF amplifying section or an output signal of RF modulating section to TV set, the RF modulator further comprises a power supply section of VCR set SET made to selectively supply the modulating voltage B2+ being a bias power of the RF modulating section and the booster voltage Bl+ being a bias power of the first and second amplifying sections; and a power switching circuit made to execute a 25 dividing function between the modulating voltage B2+ and the booster voltage Bl+ and at the same time to supply the modulating voltage B2+ to the first amplifying section.

2. A power switching circuit of RF modulator for PAL system as defined in claim 1, wherein said power switching circuit includes:

a first diode D1 which connects the booster voltage Bl+ terminal to anode terminal, and connects the cathode terminal to the first RF amplifying section; and a second diode D2 which connects the anode terminal to a line in which the modulation voltage B2+ is supplied to the RF modulating section f and connects the cathode terminal to a cathode terminal of the first diode D1.

3. A power switching circuit substantially as herein particularly described with reference to Figures 3 or Figure 4 of the accompanying drawings.

16 - Amendments to the claims have been filed as follows 1. In an RF modulator for PAL system comprising a first RF amplifying section for firstly amplifying the RF signal inputted to antenna ANT by applying. the booster voltage, a distributing section for distributing the RF signal amplified at the first RF amplifying section respectively to VCR interior tuner and to the second RF amplifying section, a second RF amplifying section for secondly amplifying the RF signal from the distributing section by applying the booster voltage B l +, io an RF modulating section for modulating audio/video carrier signal Ain, Vin by applying the modulation voltage B2 +, and a mixer for outputti g an output signal of the second RF amplifying section or an output signal of RF modulating section to TV set, the RF modulator further comprises is a power supply section of VCR set SET made to selectively supply the modulating voltage B2 + being a bias power of the RF modulating section and the booster voltage B l + being a bias power of the first and second amplifying sections; and a power switching circuit made to supply the modulating voltage B2 + to the RF modulating section and the first amplifying section, and to supply the booster voltage B l + to the first and second amplifying sections, and at the same time to execute an isolating function between the modulating voltage B2 + and the booster voltage B 1 +.

2s 2. A power switching circuit of RF modulator for PAL system as defined in claim 1, wherein said power switching circuit includes: a first diode D 1 which connects the booster voltage B 1 + terminal to anode terminal, and connects the cathode terminal to the first RF amplifying section; and a second diode D2 which connects the anode terminal to a line in 17 1 which the modulation voltage B2 + is supplied to the RF modulating section, and connects the cathode terminal to a cathode terminal of the first diode D1.

s 3. A power switching circuit substantially as herein particularly described with reference to Figures 3 or Figure 4 of the accompanying drawings.

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