JPS5929429Y2 - Image removal circuit in television receiver using electronic tuning tuner - Google Patents

Description

[Detailed description of the invention] The present invention relates to an image removal circuit in a television receiver using an electronically tuned tuner, and is used when only audio is received by a television receiver (hereinafter referred to as TV) using an electronically tuned tuner. It is an object of the present invention to provide a circuit that can remove an image on a screen with low power consumption by stopping at least a horizontal deflection operation and a high voltage generation operation.

In conventional TVs using electronically tuned tuners, the electronically tuned tuner's tuning voltage vT and switching voltage ■8 were obtained from the output of a flyback transformer, so even if you only wanted to receive audio, the TV's horizontal It was not possible to stop the deflection operation or high pressure generation operation, and it was not possible to remove the image (erase the raster).

For this reason, TVs using conventional electronic tuners have had the disadvantage that when only audio is received, they consume a significant amount of unnecessary power, which shortens the consumption time of TVs that use batteries.

The present invention eliminates the above-mentioned drawbacks, and the embodiments thereof will be described below with reference to the drawings.

FIG. 1 shows a circuit system diagram of a first embodiment of the circuit of the present invention.

In the figure, Ql is a horizontal output transistor, and its collector output is applied to the changeover switch S1.

This changeover switch S1 has contacts a and b, and
During normal operation, the contact a is closed.

A contact point a of the changeover switch S1 is connected to one end of a resonance capacitor C1, one end of a horizontal deflection coil L1, and a cathode of a damper diode D1, which constitute a horizontal output circuit.

The other end of the horizontal deflection coil L1 is grounded via a capacitor C2 for improving the horizontal linearity of the screen.

In addition, the contacts of the changeover switch S1 are connected to the power supply voltage input terminal of the flyback transformer 1 through a reactance load that can be considered as a parallel circuit of a coil L2 and a capacitor (stray capacitance) co, while being connected to the rectifier 2. has been done.

As is well known, during normal operation of a TV, a square wave with a horizontal scanning period is applied to the base of the horizontal output transistor Q1, so that the horizontal output transistor Q1 is repeatedly turned on and off, and the changeover switch S1 is connected to contact a. Therefore, a sawtooth wave current having a horizontal scanning period flows through the horizontal deflection coil L1, and a high-voltage flyback pulse is output from the flyback transformer 1.

That is, normal horizontal deflection operations and high pressure generation operations are performed.

This flyback pulse is rectified by the rectifier 3,
It is output as a tuning voltage (1)T of the electronic tuning tuner and a switching voltage Vs for switching the variable capacitance diode of the electronic tuning tuner when receiving a high channel and a low channel of a television signal.

Next, when the raster is erased and only audio is received, the changeover switch S is switched to the contact side.

As a result, the horizontal deflection coil L1 is disconnected from the horizontal output transistor Q1, so that the horizontal output circuit and the high voltage generation circuit stop operating.

On the other hand, even in this case, the horizontal oscillation circuit (not shown) is operating, so a square wave continues to be applied to the bases of horizontal output 1 to transistor Q1, and when horizontal output transistor Q1 is on, the power supply terminal B (voltage value is VCC)
Collector voltage flows through the coil L2, and while the horizontal output transistor Q1 is off, the energy stored in the coil L2 is transferred to the coil L2 and its stray capacitance C6.
It causes 2πJL2C6 vibration at a resonance frequency of □.

At this time, the collector of horizontal output transistor Q1 is connected to L2.
A pulse voltage is generated by the back electromotive force, and this pulse voltage is supplied to the rectifier 2 and converted into a tuning voltage T' and a switching voltage S'.

Here, this tuning voltage ■T' and switching voltage ■s'
must have the same peak value as the voltage VT t V s during normal operation of the TV so that the reception channel of the TV does not change.

Also, the inductance value of 5 coil L2 is also the horizontal deflection coil L.
Unless it is sufficiently larger than that of No. 1, the current flowing through Ql will not be reduced, and the internal loss of Ql will not be reduced.

Therefore, in consideration of the above points, the inductance value of the coil is set to N times that of the horizontal deflection coil L1, and the vibration period tR determined by the reactance load and the resonance capacitance is made equal to that of the horizontal output circuit.

That is, since the peak values (2) and -2 of the collector voltage of the horizontal output transistor Q1 are, if tB is made the same, (2)P-P will be the same value.

However, in formula (1), tH is the horizontal scanning period. The following formula holds true.

Therefore, by selecting a coil L2 that has an inductance value N times that of the horizontal deflection coil L1 that satisfies equation (2), the collector voltage vp-p with the same peak value as the collector voltage during normal operation of the TV can be obtained. Therefore, the tuning voltage ``T'' can be made equal to vT, and the switching voltage ``8'' can be made equal to ``8''.

Co is sufficiently small compared to the capacitance of capacitor C1, so N becomes considerably large, and the internal loss of horizontal output transistor Q1 is reduced.

Note that the rectifiers 2 and 3 may be shared.

FIG. 2 shows a circuit system diagram of a second embodiment of the circuit of the present invention.

In the figure, the same parts as in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

s2. s3. SJ and S5 are changeover switches that change in conjunction with changeover switch S1, and during normal operation of the TV, contact a is
connected to the side.

As a result, the vertical deflection circuit 4 is connected to the power source B via the changeover switch S5, and the changeover switch S2. Since it is connected to the vertical deflection coil L3 via S3, a sawtooth wave current flows through the vertical deflection coil L3 to perform a normal vertical deflection operation.

Next, when the raster is erased and only audio is received, the changeover switches 81 to S5 are switched to the contact side, respectively.

As a result, the operation of the horizontal output circuit, high voltage generation circuit, and vertical deflection circuit 4 is stopped, and the voltage supply to the CRT heater is cut off.

At the same time, the collector of the horizontal output transistor Q1 is connected to the selector switch S1. The vertical deflection coil L3 is connected to one end of the vertical deflection coil L3 via the switch S2, and the other end of the vertical deflection coil L3 is connected to the power source B via the changeover switch S3.

Further, the input end of the rectifier 3 is switched and connected from the output side of the flyback transformer 1 to the collector of the horizontal output transistor Q1 by a changeover switch S4.

Here, a capacitor C3 is connected in parallel to the vertical deflection coil L3.

Therefore, when the contact side -\ of the changeover switches 81 to S5 is closed, the voltage applied to the collector of the horizontal output transistor Q1 is determined by the inductance value of the vertical deflection coil L3 and the capacitance value of the capacitor C3, as in the first embodiment. A pulse voltage that oscillates at an oscillation period is generated.

This pulse voltage is rectified by a rectifier 3 and converted into a tuning voltage 7 and a switching voltage VS, and then output to an electronic tuning tuner (not shown).

The peak value of the pulse voltage at this time is the horizontal output transistor Q1 during normal operation of the TV, as in the first embodiment.
The capacitance value of the capacitor C3 is adjusted so as to be equal to the peak value of the collector output pulse voltage.

This makes it possible to receive only the audio without removing the image.

According to this embodiment, the power consumption is 1/1 of that during normal use.
It decreases to about 10 to 1/7.

Furthermore, since the vertical deflection coil L3 is used, there is no need to provide a new coil, and the structure can therefore be made at low cost.

In addition, in each of the above embodiments, a TV with an electronic tuning tuner using a horizontal output circuit that combines horizontal deflection and high voltage generation functions was explained, but the horizontal output circuit and the high voltage generation circuit having a dummy coil are separately provided. Of course, the present invention can also be applied to a TV equipped with an electronic tuner installed in the same manner.

As mentioned above, the image removal circuit in the television receiver using the electronically tuned tuner according to the present invention is provided separately from at least the horizontal deflection coil, and the image removal circuit is provided separately from the horizontal deflection coil.
A switch for selectively connecting the reactance and the horizontal deflection coil to the horizontal output transistor, and a means for obtaining a voltage for electronic tuning from the horizontal output transistor when the reactance is connected to the horizontal output transistor. , because it was configured to stop at least the horizontal deflection operation and the high voltage generation operation when the reactance by the above switch was connected to the horizontal output transistor, it was possible to remove the image and receive only the sound, and therefore the image could not be removed. Compared to television receivers that use conventional electronic tuning tuners, power consumption can be reduced when only audio is received, and since a vertical deflection coil is used as the reactance, there is no need to provide a new reactance, resulting in an inexpensive configuration. Moreover, since the vertical deflection operation can also be stopped, power consumption can be further reduced.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of first and second embodiments of the circuit of the present invention, respectively. 1...Flyback transformer, Ql...
...Horizontal output transistor, Ll...Horizontal deflection coil, L3...Vertical deflection coil.

Claims (1)

[Scope of utility model registration request] 1. In a television receiver that performs electronic tuning using a voltage obtained from the output of a flyback transformer, at least a horizontal deflection coil is provided separately or an actance is provided, and the reactance and horizontal deflection coil are selectively connected to a horizontal output transistor. and a means for obtaining a voltage for electronic tuning from the horizontal output transistor when the reactance is connected to the horizontal output transistor by the switch, and a connection between the reactance and the horizontal output transistor by the switch. An image removal circuit in a television receiver using an electronically tuned tuner configured to stop at least a horizontal deflection operation and a high voltage generation operation. 2. An image removal circuit in a television receiver using an electronic tuning tuner as claimed in claim 1, wherein the reactance is a reactance other than the reactance inside the television receiver. 3. An image removal circuit in a television receiver using an electronically tuned tuner according to claim 1, wherein at least a vertical deflection coil is shared as the reactance.