JP3346954B2 - Television signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance television signal processing IC, and more particularly to a television signal processing circuit for protecting a television receiver when power is turned on.

[0002]

2. Description of the Related Art Generally, a television receiver (TV)
The power-on system is as follows. TV
When the main switch is turned on, first, the primary power supply of the deflection processing system is turned on. The deflection processing system starts operating by this power supply, and outputs a horizontal pulse from the horizontal synchronization circuit.
This horizontal output activates the high voltage circuit and turns on the secondary power supply. This secondary power supply is a power supply for the video signal processing system. That is, unless a horizontal output is supplied to the high voltage circuit, circuits other than the deflection system such as chroma signal processing and video signal processing do not operate. Conversely, when the power is off, the secondary power is turned off and then the primary power is turned off to protect the high voltage circuit.

[0003] As described above, the system is such that even if any abnormality occurs, fatal destruction of the TV can be avoided. However, in the related art, the above-mentioned system is not provided. Hereinafter, the conventional problem will be described with reference to FIG.

In FIG. 5, a synchronizing separation circuit 12 of a horizontal synchronizing circuit 11 is converted from a composite video signal input to an input terminal 10.
Is used to separate the synchronization signal. The separated synchronization signal is
The signal is input to one input of the phase comparison circuit 13. The output of the frequency divider 14 is input to the other input of the phase comparator 13.
The output of the phase comparison circuit 13 is smoothed via the LPF 15 and input to the H-VCO (horizontal oscillator) 16. HV
CO16 has a configuration of a voltage controlled oscillator.
The oscillation frequency is controlled by the output voltage of No. 5, and the synchronizing signal in the video signal and the frequency of the horizontal output obtained from the first output fa of the H-VCO 16 via the frequency divider 14 are synchronized. As described above, the horizontal adjustment circuit 11 has the first adjustment loop L1 for adjusting the phases of the input video signal and the H-VCO 16.
Exists.

[0005] Separately, the second output fb of the H-VCO 16 and the output of the chroma crystal oscillation circuit 18 of the chroma signal processing circuit 17 are input to an automatic frequency adjustment circuit 19, and the automatic frequency adjustment circuit 19 Output of H-VCO1
There is a second adjustment loop L2 returning to 6. The chroma crystal oscillating circuit 18 constituting the second adjustment loop L2 includes a frequency divider, and the output of the chroma crystal oscillating circuit 18 connected to the input of the automatic frequency adjustment circuit 19 is a constant multiple of the horizontal frequency. The frequency is divided into Further, the second output fb of the H-VCO 16 input to the automatic frequency adjustment circuit 19 also divides the oscillation frequency of the H-VCO 16 and becomes a constant multiple of the horizontal frequency.

Here, the first and second adjustment loops L1, L1
Since L2 adjusts the oscillation frequency of the H-VCO 16 to be controlled, the respective loops are switched and used so that they do not operate at the same time.

[0007] From the operation of the first and second adjustment loops L1 and L2, first, the H-VCO1 is controlled by the second adjustment loop L2.
6 and the first adjustment loop L
1, the frequency of the output fa of the H-VCO 16 is set to a frequency synchronized with the synchronization signal included in the video signal,
The third output fc more stable than 16 is input to the horizontal output circuit 20.

The chroma crystal oscillation circuit 18 is provided for demodulating a TV chroma signal. Therefore, it is generally located in a chroma signal processing system. Also, since the oscillator uses a crystal, the output signal frequency of this circuit is very stable and accurate. On the other hand, the H-VCO 16 in the horizontal synchronization circuit 11 existing in the TV deflection processing system has a very unstable free-running frequency due to the influence of the circuit configuration and its constituent elements. Therefore, the frequency of the H-VCO 16 is adjusted based on the stable output of the chroma crystal oscillation circuit 18 by the automatic frequency adjustment circuit 19 which receives the output of the chroma crystal oscillation circuit 18 and the output of the H-VCO 16 as inputs.

However, in this conventional method, as described above, since the output frequency of the H-VCO 16 is adjusted based on the output of the chroma crystal oscillation circuit 18, the chroma signal processing circuit 17 including the chroma crystal oscillation circuit 18 is controlled. The power must also be taken from the primary power supply 21. Therefore, the burden on the primary power supply 21 increases, and the above-described power on / off processing cannot be performed. As a result, there is a disadvantage that the processing at the time of abnormality becomes complicated.

Also, since the convergence time of the automatic frequency adjustment circuit 19 is determined by the free-running frequency of the H-VCO 16, the horizontal pulse output from the horizontal output circuit 20 may not be the desired frequency in some cases. , High voltage circuit 2
2 and the TV set could be destroyed.

[0011]

The above-mentioned conventional television set
In the case of the television signal processing circuit , the burden on the primary power supply is increased, the power supply cannot be controlled on / off, and the high voltage circuit is driven in a state where the horizontal pulse does not reach a desired frequency. Could be destroyed.

[0012] This invention is to reduce the burden of the primary power source, capable of obtaining a stable horizontal output Terebiji
Provide an application signal processing circuit .

[0013]

Means for Solving the Problems] The present invention, (a) Black
A frequency equal to a constant multiple of the horizontal frequency for demodulating the
Has a chroma crystal oscillation circuit that generates a wave number reference signal
A chroma signal processing circuit and (b) a synchronizing signal of a composite video signal
A voltage-controlled oscillator for generating a signal synchronized with the reference;
Automatically adjusts the output frequency of the voltage controlled oscillator by a signal
Automatic adjustment circuit, based on the output of the automatic adjustment circuit
Synchronous state between the reference signal and the output of the voltage controlled oscillator
A synchronous detection circuit for detecting the
A circuit for generating horizontal pulses for horizontal scanning from
The horizontal pulse is generated based on the output of the synchronization detection circuit.
Circuit input to ground or the output of the voltage controlled oscillator
A horizontal synchronizing circuit having switching means connected to either
Wherein the chroma crystal oscillation circuit includes a chroma signal processing circuit.
Power supply of the horizontal synchronization circuit independent of the power supply system of the
It is characterized by being driven more . In addition, the present invention
(A) Constant multiple of horizontal frequency for demodulating chroma signal
Chroma crystal oscillation circuit that generates a reference signal with a frequency equal to
Signal processing circuit having a path, and (b) a composite video signal
Voltage Controlled Oscillator Generates Signal Synchronized with Synchronous Signal
And the output frequency of the voltage controlled oscillator according to the reference signal.
An automatic adjustment circuit for automatically adjusting the number,
The reference signal and the output of the voltage controlled oscillator based on the output;
A synchronization detection circuit for detecting a synchronization state with the voltage control;
Generate horizontal pulses for horizontal scanning from oscillator output
And the horizontal pulse based on the output of the synchronization detection circuit.
Input to the chroma crystal oscillator circuit.
Or a switch connected to any output of the voltage controlled oscillator.
And a horizontal synchronization circuit having a conversion means.
The crystal oscillation circuit is independent of the power supply system of the chroma signal processing circuit.
Driven by the power supply of the horizontal synchronizing circuit.
Features.

[0014]

According to the above means, the output of the horizontal deflection pulse is held in a stopped state until the output of the chroma crystal oscillation circuit and the output of the voltage controlled oscillator are synchronized and the automatic adjustment operation is completed.
After the automatic adjustment operation is completed, a horizontal deflection pulse is output. Thus, a stable horizontal pulse can always be supplied to the high voltage circuit.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention. The same components as in FIG. 5 will be described with the same reference numerals. In this embodiment, the chroma crystal oscillation circuit 181 is separated from the chroma signal processing circuit 171 and the chroma signal processing circuit 17
The power supply 1 is supplied from the high voltage circuit 221, and the chroma crystal oscillation circuit 181 is supplied from the primary power supply 21 to reduce the load on the primary power supply 21.

Further, the synchronization detection circuit 23 receives the output of the automatic frequency adjustment circuit 19 as an input, and
It determines whether the output of the chroma crystal oscillation circuit 181 and the output of the H-VCO 16 are synchronized, and outputs the result. Further, the output of the H-VCO 16 whose frequency has been automatically adjusted by the second adjustment loop L2 is not directly input to the horizontal output circuit 20 but is input to the switch circuit 24 once.
This switch circuit 24 is controlled by the output of the synchronization detection circuit 23.

The output of the chroma crystal oscillation circuit 181 and HV
When the outputs of the CO 16 are synchronized, the synchronization detection circuit 23
Controls the switch circuit 24 so that the output of the H-VCO 16 is input to the horizontal output circuit 20. When the output of the chroma crystal oscillation circuit 181 and the output of the H-VCO 16 are not synchronized, the synchronization detection circuit 23
The switch circuit 24 is controlled so that the input of the switch circuit is grounded.

As a result, until the output of the chroma crystal oscillation circuit 181 and the output of the H-VCO 16 are synchronized and the automatic adjustment operation is completed, the output of the horizontal output circuit 20 is kept stopped, and the automatic adjustment operation is completed. After that, the horizontal output circuit 20
Outputs more horizontal pulses. Thereby, the high voltage circuit 2
21 can always be supplied with a stable horizontal pulse.

In this embodiment, the burden on the primary power source 21 is
The output of the horizontal output circuit 20 is output to the high voltage circuit 21 after the automatic adjustment operation is completed, so that the TV set can be prevented from being destroyed. Becomes

FIG. 2 is a circuit diagram for explaining a modification of the embodiment of FIG. In this embodiment, the H-VCO 1
6 is directly input to the horizontal output circuit 20, and the output of the horizontal output circuit 20 is switched using the switch circuit 24. In this embodiment, exactly the same effects as described in the embodiment of FIG. 1 can be obtained.

Next, another embodiment of the present invention will be described with reference to the circuit diagram of FIG. In the horizontal synchronization circuit 111 of this embodiment, the output fb of the H-VCO 16 and the output of the chroma crystal oscillation circuit 181 are switched by the switch circuit 241 and input to the horizontal output circuit 20.

In this system, when the outputs of the H-VCO 16 and the chroma crystal oscillation circuit 181 are not synchronized, the synchronization detection circuit 19 causes the second output of the chroma crystal oscillation circuit 181 to be input to the horizontal output circuit 20. Control the switch circuit 241. At this time, the output of the chroma crystal oscillation circuit 181 input to the horizontal output circuit 20 has the same frequency as the output of the H-VCO 16 after the automatic adjustment output. When the automatic adjustment is completed, the synchronization detection circuit 19 sets the horizontal output circuit 2
The switch circuit 241 is switched so that the input of 0 becomes the output of the H-VCO 16.

As described above, the signal input to the horizontal output circuit 20 before the end of the automatic adjustment is output from the chroma crystal oscillation circuit 181 so that the high voltage circuit 221 can be quickly and stably.
Can be operated.

In this embodiment, the secondary power supply for the chroma signal processing circuit 171 generated based on the high voltage circuit 221 is quickly turned on, and the effect of stabilizing the TV set can be obtained quickly. , Can prevent equipment destruction.

FIG. 4 is a diagram for explaining a specific example of the chroma crystal oscillation circuit used in the present invention. This chroma crystal oscillation circuit has a chroma demodulation frequency of 3.58 MHz.
It can support all TV signal broadcasting systems represented by z and 4.43 MHz.

In FIG. 4, a switch circuit 41 for selecting one of crystal oscillators C1, C2 to Cn corresponding to a certain broadcasting system and an oscillator 42 which oscillates based on the frequency of the crystal oscillator are provided. It is composed of frequency dividers 431, 432 to 43n for dividing the output of the oscillator 42 and a switch circuit 44 for selecting the output of these frequency dividers.

[0027] Even if the crystal oscillators C1, C2 to Cn are switched by the switch circuit 41, the system discriminating circuit 45 ensures that the output of the switch circuit 44 always has a constant frequency.
Controls the switch circuit 44. The output of the switch circuit 44 is input to the automatic frequency adjustment circuit 19 described in each embodiment of FIGS. 1, 2 and 3.

[0028]

As described above, the television of the present invention
According to the John signal processing circuit , the burden on the primary power supply can be reduced and the TV set can be protected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a modification of the embodiment of FIG. 1;

FIG. 3 is a circuit configuration diagram for explaining another embodiment of the present invention.

FIG. 4 is a circuit configuration diagram for explaining a specific example of a chroma crystal oscillation circuit used in an embodiment of the present invention.

FIG. 5 is a circuit configuration diagram for explaining a conventional horizontal synchronization circuit.

[Explanation of symbols]

111: horizontal synchronization circuit, 12: synchronization separation circuit, 13: phase comparison circuit, 14: frequency divider, 15: LPF, 16: H-
VCO, 171: Chroma signal processing circuit, 181: Chroma crystal oscillation circuit, 19: Automatic frequency adjustment circuit, 20: Horizontal output circuit, 21: Primary power supply, 221: High voltage circuit, 24,
241, a switch circuit, and 23, a synchronization detection circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-30379 (JP, A) JP-A 3-79564 (JP, U) JP-A 53-59323 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) H04N 3/18 H04N 5/04

Claims (4)

(57) [Claims] (A) a horizontal signal for demodulating a chroma signal;
Generates a reference signal with a frequency equal to a constant multiple of the frequency.
It generates a chroma signal processing circuit having a Roma crystal oscillation circuit, a signal synchronized with the synchronizing signal (b) composite video signal
A voltage controlled oscillator, and the voltage control by the reference signal.
An automatic adjustment circuit that automatically adjusts the output frequency of the oscillator;
The reference signal and the voltage based on the output of the automatic adjustment circuit.
Synchronous detection circuit that detects the state of synchronization with the output of the controlled oscillator
And water for horizontal scanning from the output of the voltage controlled oscillator.
A circuit for generating a flat pulse, and an output of the synchronization detection circuit.
The input of the circuit for generating the horizontal pulse is grounded or
Is a switch connected to one of the outputs of the voltage controlled oscillator
And a horizontal synchronizing circuit having means, wherein the chroma crystal oscillation circuit is provided with the chroma signal processing circuit.
Driven by the power supply of the horizontal synchronization circuit independent of the power supply system
A television signal processing circuit. 2. The switching means according to claim 1 , wherein said switching means controls an output frequency of said voltage controlled oscillator based on said reference signal.
Before the end of automatic adjustment, input of the circuit for generating the horizontal pulse is performed.
Ground the power and the output frequency of the voltage controlled oscillator by the reference signal.
After the automatic adjustment, the circuit for generating the horizontal pulse is turned on.
Connecting a force to the output of the voltage controlled oscillator.
The television signal processing circuit according to claim 1. 3. A horizontal signal for demodulating a chroma signal.
Generates a reference signal with a frequency equal to a constant multiple of the frequency.
It generates a chroma signal processing circuit having a Roma crystal oscillation circuit, a signal synchronized with the synchronizing signal (b) composite video signal
A voltage controlled oscillator, and the voltage control by the reference signal.
An automatic adjustment circuit that automatically adjusts the output frequency of the oscillator;
The reference signal and the voltage based on the output of the automatic adjustment circuit.
Synchronous detection circuit that detects the state of synchronization with the output of the controlled oscillator
And water for horizontal scanning from the output of the voltage controlled oscillator.
A circuit for generating a flat pulse, and an output of the synchronization detection circuit.
Input of the circuit for generating the horizontal pulse based on the
Ma crystal oscillation circuit or of any of the voltage control oscillator
A horizontal synchronizing circuit having switching means connected to the output.
In addition, the chroma crystal oscillation circuit includes the chroma signal processing circuit.
Driven by the power supply of the horizontal synchronization circuit independent of the power supply system
A television signal processing circuit. 4. The switching means according to claim 1 , wherein said switching means controls an output frequency of said voltage controlled oscillator based on said reference signal.
Before the end of automatic adjustment, input of the circuit for generating the horizontal pulse is performed.
The force is connected to the output of the chroma crystal oscillation circuit, the reference
Automatic adjustment of the output frequency of the voltage controlled oscillator by a signal
After completion, the input of the circuit for generating the horizontal pulse is
Claims: Connected to the output of a voltage controlled oscillator
Item 3. The television signal processing circuit according to Item 3 .