JPH0818881A - Television receiver - Google Patents

Abstract

PURPOSE:To receive even an FM radio broadcast without connection of a large circuit to a circuit for television broadcast reception. CONSTITUTION:The receiver is provided with an intermediate frequency circuit 15 having a tuner receiving a broadcast of an FM ratio band and a video circuit of a PLL detection system employing a PLL detection circuit 33, an audio detection circuit 32 to FM demodulation circuit 38 detecting and FM- demodulating the audio intermediate frequency signal to provide an output of an audio signal in an audible frequency range based on the detection signal of the PLL detection circuit 33 and a filter amplifier 41 as a correction means correcting a frequency of the detection signal of the PLL detection circuit 33 in a free run state because no video intermediate frequency signal is received from the tuner in the reception of the broadcast at the FM radio band with an audio signal outputted from the FM demodulation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver having an FM radio receiving function, which is applied to, for example, a portable liquid crystal television.

[0002]

2. Description of the Related Art Conventionally, liquid crystal television devices, etc., which are supposed to be used outdoors in consideration of portability, can receive FM radio broadcasts having frequencies close to each other instead of receiving television broadcasts. There is something I did. In such a TV receiver capable of receiving FM radio, a tuner for FM radio reception is provided separately from a tuner circuit for receiving TV broadcast, and only an audio amplifier circuit is used in common, or a TV carrier is received by a separate carrier system. Even when the video signal and the audio signal are processed by different receiving circuits, the receiving circuit configuration is taken.

[0003]

As described above, in a television receiver capable of receiving FM radio, a tuner circuit for receiving television broadcast and a tuner for receiving FM radio are provided separately, or when receiving television broadcast by a separate carrier system. A separate circuit for the video signal and the audio signal is provided in advance as a circuit for use, and in either case, the circuit configuration becomes complicated and the scale becomes large.

The present invention has been made in view of the above circumstances, and an object thereof is to be able to receive FM radio broadcasts without additionally connecting a large circuit to a circuit for receiving television broadcasts. Providing a simple television receiver.

[0005]

That is, the present invention provides an FM
A tuner circuit capable of receiving radio band broadcasts and a PLL
In a television receiver having a PLL detection type video circuit using a circuit, an audio intermediate frequency signal input from the tuner is detected and FM demodulated based on a detection signal of the PLL circuit to output audio in an audible frequency range. A voice detection means for outputting as a signal is provided.

[0006]

With the above-mentioned structure, the FM radio broadcast can be received only by adding a simple circuit to the television receiver.

[0007]

【Example】

[First Embodiment] A first embodiment in which the present invention is applied to a liquid crystal television device will be described below with reference to the drawings.

FIG. 1 shows the overall circuit configuration. Television or FM radio waves received by an antenna 11 are supplied to a tuner 12. The tuner 12 selects a designated channel (frequency) according to the tuning signal from the tuning control circuit 13 and converts it into an intermediate frequency signal. Then, the intermediate frequency signal output from the tuner 12 is sent to the filter circuit 14.

The filter circuit 14 separates the obtained intermediate frequency signal into a video intermediate frequency signal and an audio intermediate frequency signal and sends them to an intermediate frequency circuit (shown as "IF circuit" in the figure) 15.

As will be described later in detail, the intermediate frequency circuit 15 amplifies the video intermediate frequency signal sent from the tuner 12 through the filter circuit 14 and then detects the video signal by the PLL detection method to obtain a video signal, While being sent to the circuit 16 and the sync separation circuit 17, the audio intermediate frequency signal sent from the tuner 12 via the filter circuit 14 is subjected to audio detection and FM demodulation to produce an audio signal in the audible frequency range, which is sent to the audio amplifier circuit 18. Send out.

The audio amplifier circuit 18 amplifies the audio signal from the intermediate frequency circuit 15 with a specific amplification factor, and drives the speaker 19 by the obtained signal to emit sound. Further, the sync separation circuit 17 separates the horizontal and vertical sync signals contained in the video signal, and sends the composite sync signal C-SYNC to the tuning control circuit 13 and the horizontal sync signal H-SYNC.
And the vertical synchronizing signal V-SYNC is supplied to the timing control circuit 20
Output to each.

The tuning control circuit 13 includes a key input section.
Data for tuning setting from 21, FM radio, VH
Key input such as selection of received broadcast of F or UHF and tuning up / down instruction is given. The tuning control circuit 13 creates a tuning signal having a voltage value corresponding to a designated channel (frequency) based on the operation of the tuning up / down key in the key input unit 21 and outputs it to the tuner 12.

The timing control circuit 20 outputs a timing pulse φ based on the horizontal sync signal H-SYNC and the vertical sync signal V-SYNC sent from the sync separation circuit 19.
s is created and output to the A / D conversion circuit 22.

The chroma circuit 16 performs chroma processing on the video signal supplied from the intermediate frequency circuit 15 to obtain R, G, B.
A chroma signal composed of the three primary colors is obtained, and the obtained chroma signal is output to the A / D conversion circuit 22.

The A / D conversion circuit 22 converts the chroma signal output from the chroma circuit 18 into the sampling pulse φs.
Sampling is performed in synchronism with the above, converted into digital video data of 3 to 4 bits per pixel, and the segment drive circuit 23
Output to.

Further, the timing control circuit 20 creates a timing signal for display control based on the horizontal sync signal H-SYNC and the vertical sync signal V-SYNC provided from the sync separation circuit 19, and the segment drive circuit 23 and It controls the operation of the common drive circuit 24.

The common drive circuit 24 generates a scanning signal in accordance with the timing signal from the timing control circuit 20, and sequentially scans and drives the common electrodes of the color LCD panel 25. The segment drive circuit 23 sequentially reads the 3- to 4-bit video data supplied from the A / D conversion circuit 22 according to the timing signal from the timing control circuit 20, and reads the video data for one line, and then reads the video data. In response, a gradation signal is created and the segment electrodes of the color LCD panel 25 are driven to display.

However, when the FM radio broadcast is received by the key input instruction of the key input unit 21, the video intermediate frequency signal is not input from the filter circuit 14 to the intermediate frequency circuit 15, and the intermediate frequency circuit 15 causes the chroma circuit 16 to perform the sync separation. Since the video signal is not sent to the circuit 17, the tuning control circuit 13 sends a control signal to the chroma circuit 16 and the timing control circuit 20 to stop the operation, and temporarily stops the operation of displaying an image on the color LCD panel 25. Avoid wasted power consumption.

Next, the structure of the intermediate frequency circuit 15 will be described with reference to FIG. In the figure, the video intermediate frequency signal sent from the filter circuit 14 is sent to a video intermediate frequency amplifier circuit (shown as "video IF amplifier circuit" in the figure) 31, and the audio intermediate frequency signal from the filter circuit 14 is also an audio detection circuit. Input to 32.

The video intermediate frequency amplifier circuit 31 has an AGC inside.
An (automatic gain control) circuit or the like is provided, and the video intermediate frequency signal from the filter circuit 14 is appropriately amplified so as to have a constant signal level and then sent to the PLL detection circuit 33.

This PLL detection circuit 33 is composed of a coil L1 and a capacitor C1 which are connected in parallel to each other, and a PLL tuning circuit 34 which is tuned to an oscillation frequency, and a resistor C1 whose one end is grounded and a capacitor C2 which is connected in series.
35 is connected, and performs video detection on the video intermediate frequency signal from the video intermediate frequency amplifier circuit 31 amplified to a certain level, reproduces the video signal, and synchronizes with the chroma circuit 16 in the next stage and the synchronization. While outputting to the separation circuit 17, the detection signal is sent to the audio detection circuit 32.

The voice detection circuit 32 performs voice detection of the voice intermediate frequency signal input from the filter circuit 14 according to the detection signal from the PLL detection circuit 33, and converts it into a specific frequency. The specific frequency signal obtained by the voice detection circuit 32 is band-limited by the filter 36, amplified by the limiter amplifier 37, and further sent to the FM demodulation circuit 38.

This FM demodulation circuit 38 is a demodulation tuning circuit comprising a coil L2 and a capacitor C4 connected in parallel with one end grounded and a capacitor C3 connected in series with these.
39 is connected, and FM is output to the output of the limiter amplifier 37.
Obtain audio signals in the audible frequency range by performing demodulation,
This is output to the audio amplification circuit 18 of the next stage, and is also supplied to the filter amplifier 41 via the switch 40 which is a normally open contact.

The filter amplifier 41 amplifies the low frequency band of the audio signal and extracts the DC voltage component from the PLL detection circuit 33.
Is applied to the connection point of the PLL filter 35. Further, the video intermediate frequency amplifier circuit 31 is connected to a switch 42 which is a normally open contact whose one end is grounded and which minimizes the gain of the built-in AGC circuit.

Therefore, the switches 40 and 42 are both F
Tuning control circuit for receiving M radio broadcasting
It is turned on by the control of 13. In the circuit configuration as described above, the frequency band (VHF-L, VHF-H or UH is output from the tuning control circuit 13 when receiving a television broadcast.
F) and a tuning signal corresponding to the designated channel are sent to the tuner 12, and the tuner 12 selects the television broadcast radio wave of the designated channel, converts it into an intermediate frequency signal, and sends it to the filter circuit 14. The filter circuit 14 separates the intermediate frequency signal into a video intermediate frequency signal having a carrier frequency of 58.75 MHz and an audio intermediate frequency signal having a carrier frequency of 54.25 MHz with proper frequency characteristics and sends them to the intermediate frequency circuit 15. To do.

The switch 42 of the video intermediate frequency amplifying circuit 31 is off, and the internal AGC circuit is operated to control and amplify the video intermediate frequency signal to a constant level, and P
It is supplied to the LL detection circuit 33. In the PLL detection circuit 33, the PL
The frequency set by the L tuning circuit 34 and the PLL filter 35,
The video intermediate frequency signal is detected in accordance with the phase, the video signal is reproduced and output to the chroma circuit 16 and the sync separation circuit 17 in the next stage, while the detection signal is sent to the audio detection circuit 32.

The voice detection circuit 32 is a PLL detection circuit 33.
Audio detection is performed on the audio intermediate frequency signal input from the filter circuit 14 according to the detection signal from, and the detection output is band-limited and amplified via the filter 36 and the limiter amplifier 37 after being converted to a specific frequency. , FM demodulation circuit 38. Then, the FM demodulation circuit 38 performs FM modulation according to the tuning frequency of the demodulation tuning circuit 39 to obtain an audio signal in the audible frequency range, and outputs this to the audio amplification circuit 18 in the next stage. Since the switch 40 is off at this time,
The input to the filter amplifier 41 is not made, and the audio signal is PL
The L filter 35 does not affect the PLL detection circuit 33.

Next, when FM radio broadcasting is received instead of television broadcasting, the tuning control circuit 13 sends a tuning signal corresponding to the frequency band (VHF-L) and the specified frequency to the tuner 12, and the tuning signal of the specified frequency is received. FM
Radio waves are selected, converted into intermediate frequency signals, and sent to the filter circuit 14. An audio intermediate frequency of 4.5 MHz, which is the difference between 58.75 MHz and 54.25 MHz, can be obtained through the filter circuit 14, and the audio intermediate frequency signal is an audio detection circuit of the intermediate frequency circuit 15. 32 to the video intermediate frequency amplifying circuit 31, while naturally no input is made to the video intermediate frequency amplifying circuit 31.

At this time, since the switch 42 is turned on under the control of the tuning control circuit 13, the AGC circuit in the video intermediate frequency amplification circuit 31 performs the amplification operation with the minimum gain. Therefore, it is possible to prevent the video intermediate frequency signal having a substantially zero level from being unintentionally amplified and supplying the video intermediate frequency signal having a high noise level to the PLL detection circuit 33.

On the other hand, the audio intermediate frequency signal input to the audio detection circuit 32 is audio-detected here at a frequency according to the detection signal of the PLL detection circuit 33, and after being converted to a specific frequency, its detection output is filtered. The signal is band-limited and amplified through the limiter amplifier 37 and supplied to the FM demodulation circuit 38. Then, the FM demodulation circuit 38 performs FM modulation according to the tuning frequency of the demodulation tuning circuit 39 to produce an audio signal in the audible frequency range, which is output to the audio amplification circuit 18 at the next stage.

At this time, since the video intermediate frequency signal is not input to the PLL detection circuit 33 as described above, it is possible that the predetermined frequency of the detection signal to the audio detection circuit 32 deviates to some extent in the free run state. To be

Therefore, the change of the detection signal is corrected by utilizing the direct current component of the audio signal output from the FM demodulation circuit 38, which change is interlocked with the detection signal of the PLL detection circuit 32. That is, the switch 40 is turned on under the control of the tuning control circuit 13 at the start of reception of the FM radio broadcast, the audio signal output from the FM demodulation circuit 38 is amplified by the filter amplifier 41 only in the low frequency band, and its DC voltage component is generated. By supplying it to the connection terminal of the PLL filter 35 of the PLL detection circuit 33, the operating frequency of the PLL detection circuit 33 is corrected and the above deviation is avoided.

In the first embodiment, the filter amplifier
PLL detection circuit for the DC voltage component of the audio signal obtained in 41
Although the deviation of the oscillation frequency of the PLL detection circuit 33 is corrected by applying it to the connection terminal of the PLL filter 35 of No. 33, instead of this, A (not shown) of the tuner 12 is used.
The same effect can be obtained by applying it to the terminal of FT (automatic frequency tuning circuit).

[Second Embodiment] A second embodiment in which the present invention is applied to a liquid crystal television device will be described below with reference to the drawings.

FIG. 3 shows the entire circuit configuration, and since it is basically the same as that shown in FIG. 1, the same parts are designated by the same reference numerals and the description thereof will be omitted. Then, the intermediate frequency signal of the designated channel (frequency) obtained by the tuner 12 is subjected to an intermediate frequency circuit (shown as "IF circuit" in the figure) after being selectively given a frequency band limitation described later by the filter circuit 51. Sent to 52.

The intermediate frequency circuit 52 is constructed by a pseudo-coherent detection method by connecting a coil 53 for signal extraction, and it is one of the intermediate frequency signals sent via the filter circuit 51. And the audio intermediate frequency signal are separated, respectively detected to reproduce the video signal and the audio signal, the video signal to the chroma circuit 16 and the sync separation circuit 17,
An AF that outputs audio signals to the audio amplifier circuit 18 and that changes depending on the degree of tuning obtained during video detection
The T signal is sent to the tuning control circuit 13.

The tuning control circuit 13 creates a tuning signal having a voltage value according to a frequency band (VHF-L, VHF-H or UHF) and a designated channel (frequency), and outputs it to the tuner 12 while outputting FM.
When receiving a radio broadcast, an FM reception switching signal is output to the filter circuit 14 and the oscillation circuit 54.

This oscillation circuit 54 is a tuning control circuit.
Corresponding to the FM reception switching signal from 13, the carrier frequency of the video intermediate frequency signal of TV broadcasting is equal to 58.75 MH
A detection signal of z is oscillated, and this is supplied to the coil 55 which is arranged opposite to the coil 53.

Next, the detailed circuit configuration in the filter circuit 51 will be described with reference to FIG. In the figure, the intermediate frequency signal sent from the tuner 12 is input to the switching filter 61. The switching filter 61 switches and selects the pass band characteristic according to the FM reception switching signal from the tuning control circuit 13, and the intermediate frequency signal passing through the switching filter 61 is amplified by the amplifier 62 with a specific amplification factor. Is
Further, the delay time characteristic is improved by the SAW filter 63 and then supplied to the intermediate frequency circuit 52 of the next stage.

In the circuit configuration as described above, the tuning control circuit 13 sends a tuning signal corresponding to the frequency band (VHF-L, VHF-H or UHF) and the designated channel to the tuner 12 when receiving a television broadcast. The tuner 12 selects the television broadcast radio wave of the designated channel, converts it into an intermediate frequency signal, and sends it to the filter circuit 51.

In this filter circuit 51, since the FM reception switching signal from the tuning control circuit 13 is at the "L" level, the intermediate frequency signal input to the switching filter 61 is shown by the solid line a in FIG. So that it passes with a flat and proper frequency characteristic. The output of the switching filter 61 is amplified by the amplifier 62, the delay time characteristic thereof is improved by the SAW filter 63, and then sent to the intermediate frequency circuit 52 of the next stage.

In the intermediate frequency circuit 52, the input intermediate frequency signal is separated into a video intermediate frequency signal and an audio intermediate frequency signal, and pseudo synchronous detection is performed using the video intermediate frequency signal to convert the video signal and the audio signal. It reproduces and outputs the video signal to the chroma circuit 16 and the sync separation circuit 17 in the next stage, the audio signal to the audio amplifier circuit 18 in the next stage, and the AFT signal to the tuning control circuit 13.

Next, when FM radio broadcasting is received instead of television broadcasting, the tuning control circuit 13 sends a tuning signal according to the frequency band (VHF-L) and the designated frequency to the tuner 12, and the tuning frequency of the designated frequency is changed. FM
Radio waves are selected, converted into intermediate frequency signals, and sent to the filter circuit 51.

At this time, the switching filter 61 of the filter circuit 51
Since the "H" level FM reception switching signal is input to the tuning control circuit 13, the switching filter
The characteristic of 61 is switched and selected so as to pass only around the carrier frequency (54.25 MHz) of the audio intermediate frequency signal as shown by the broken line b in FIG. Therefore, the intermediate frequency signal of the FM radio wave whose frequency band is limited after passing through the switching filter 61 is amplified by the amplifier 62, and the SAW
After the delay time characteristic is improved by the filter 63, it is sent to the intermediate frequency circuit 52 of the next stage.

At the same time, F of the tuning control circuit 13
58.75M which is equal to the carrier frequency of the video intermediate frequency signal oscillated from the oscillation circuit 54 in response to the M reception switching signal.
The Hz detection signal is supplied to the coil 55, and this is supplied to the intermediate frequency circuit 52 via the coil 53. In the intermediate frequency circuit 52, the intermediate frequency signal from the filter circuit 51 is quasi-coherently detected on the basis of the detected signal to obtain only a 4.5 MHz audio intermediate frequency signal, which is output to the audio amplifier circuit 18 to output the speaker. Along with driving the loudspeaker 19, an audio intermediate frequency signal that changes in an S-shape in accordance with the tuning state similarly to the AFT signal is sent to the tuning control circuit 13 instead of the ATF signal.

At this time, the intermediate frequency circuit 52 to the chroma circuit 1
6. Since the video intermediate frequency signal is not output to the sync separation circuit 17, the tuning control circuit 13 sends a control signal for stopping the operation to the chroma circuit 16 and the timing control circuit 20 to display the video on the color LCD panel 25. Temporarily stop operation to avoid unnecessary power consumption.

As described above, the switching filter 61 of the filter circuit 51 passes the whole range of the intermediate frequency signal as a flat characteristic over a wide band when receiving television, while the FM filter receives the intermediate frequency as a narrow band pass characteristic by switching selection. By limiting the band of the signal, malfunctions at the time of FM radio reception are prevented.

In addition, the intermediate frequency circuit 52 when receiving FM radio
The oscillating circuit 54 oscillates and gives a detection signal of the same frequency instead of the video intermediate frequency signal which is not input to the FM intermediate frequency circuit 52, thereby compensating for the pseudo-synchronous detection operation of the intermediate frequency circuit 52 and the audio intermediate frequency signal of the FM radio. Can be generated to demodulate the audio signal.

In the second embodiment described above, the detection signal of 58.75 KHz oscillated and output from the oscillation circuit 54 is described as being supplied to the intermediate frequency circuit 52 by the coil 55 through the coil 53. However, instead of this, For example, as shown in FIG. 6, even if the detection signal is superimposed on the band-limited intermediate frequency signal output from the switching filter 61 at the input section or the output section of the amplifier 62 in the filter circuit 51, the intermediate signal is similarly obtained. The detection operation of the frequency circuit 52 can be realized.

Further, since FM radio broadcasting can also be carried out by adding a simple circuit in the television receiver using the intermediate frequency circuit of the pseudo-synchronous detection system as described above, the pseudo-synchronous detection is currently performed in a very large number of product models. The present invention can be applied to a liquid crystal television device adopting the system as it is, and it is possible to provide a liquid crystal television device capable of receiving FM radio broadcasting at a low cost with a reduced cost.

[0051]

As described above in detail, according to the present invention, it is possible to provide a television receiving apparatus capable of receiving FM radio broadcasting without adding a large circuit to the circuit for receiving television broadcasting. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall circuit configuration according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed circuit configuration in the intermediate frequency circuit of FIG.

FIG. 3 is a block diagram showing an overall circuit configuration according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a detailed circuit configuration in the filter circuit of FIG.

5 is a diagram showing bandpass characteristics of the switching filter of FIG.

6 is a block diagram illustrating another circuit configuration of the filter circuit of FIG.

[Explanation of symbols]

11 ... Antenna, 12 ... Tuner, 13 ... Tuning control circuit, 14, 51 ... Filter circuit, 15, 52 ... Intermediate frequency circuit, 16
… Chroma circuit, 17… Sync separation circuit, 18… Audio amplification circuit,
19 ... Speaker, 20 ... Timing control circuit, 21 ... Key input part, 22 ... A / D conversion circuit, 23 ... Segment drive circuit, 24
... common drive circuit, 25 ... color LCD panel, 31 ... video intermediate frequency amplification circuit, 32 ... audio detection circuit, 33 ... PLL detection circuit, 34 ... PLL tuning circuit, 35 ... PLL filter, 36 ...
Filter, 37 ... Limiter amplifier, 38 ... FM demodulation circuit, 39
... Demodulation tuning circuit, 40, 42 ... Switch, 41 ... Filter amplifier, 53, 55 ... Coil, 54 ... Oscillation circuit, 61 ... Switching filter, 62 ... Amplifier, 63 ... SAW filter.

Claims (5)

[Claims] 1. A television receiver having a tuner circuit capable of receiving FM radio band broadcasts and a video circuit of a PLL detection system using a PLL circuit, wherein the tuner is based on a detection signal of the PLL circuit. A television receiver comprising a sound detecting means for detecting and FM demodulating an inputted sound intermediate frequency signal and outputting as a sound signal in an audible frequency range. 2. The frequency of the detection signal of the PLL circuit, which is in a free-run state when a video intermediate frequency signal is not input from the tuner when the FM radio band broadcast is received,
The television receiver according to claim 1, further comprising a correction unit that corrects the audio signal output from the audio detection unit. 3. The television receiver according to claim 1, wherein the video circuit further comprises switching means for minimizing the amplification gain of the video intermediate frequency signal when receiving the broadcast of the FM radio band. 4. A television receiver having a tuner circuit capable of receiving FM radio band broadcasting and a pseudo-detection intermediate frequency circuit, wherein detection of a frequency equal to the video intermediate frequency signal is received when the FM radio band broadcasting is received. An oscillating means for oscillating a signal and an intermediate frequency circuit of the pseudo detection system is operated based on the detected signal obtained by the oscillating means to reproduce an audio signal in an audible frequency range from the intermediate frequency signal input from the tuner. A television receiver comprising a control means. 5. A filter switching means is further provided for performing band limitation by switching selection so that only the audio intermediate frequency signal component of the intermediate frequency signal inputted from the tuner is passed when receiving the broadcast of the FM radio band. The television receiver according to claim 4.