JPS6360593B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a horizontal output circuit for a television receiver. This invention relates to a horizontal output circuit equipped with a correction circuit.

[Prior art]

FIG. 1 is an explanatory diagram of a television screen on which screen distortion has not been corrected. In the figure, P is the screen,
D indicates the dark part of the pattern, and B indicates the bright part.

Generally, the brightness of the picture on a television screen changes depending on the broadcast content. When the picture is bright, a large beam current is required, which means that the high voltage load on the cathode ray tube increases, and the high voltage decreases.
Conversely, if the pattern is dark, this means that the high voltage load has decreased, and the high voltage increases.

As shown in Figure 1, a bright pattern B appears in the center of the screen.
When the bright area B is displayed, as the raster moves vertically, the horizontal size expands due to the high voltage drop in the CRT, and the originally square area B is distorted into a trapezoidal shape. It is known that

FIG. 2 is a circuit diagram showing a conventional horizontal output circuit equipped with a correction circuit for correcting screen distortion as described above. In the figure, M is a horizontal oscillation circuit, 1 is a resistor, 2 is a capacitor, 3 is a horizontal excitation transformer, 4 is a horizontal excitation transistor, 5 is a horizontal output transistor, 6 is a damper diode, 7 is a resonant capacitor, and 8 is a horizontal deflection yoke, 9 is an S-shaped correction capacitor, 10 is a flyback transformer,
11 is a power supply, 12 is a diode, 13 is a capacitor, 14 is a high voltage load, 15 is a capacitor, and 16 is a diode. A circuit portion Y indicated by a broken line corresponds to a distortion correction circuit.

Figure 3 shows the bright pattern B in the center of Figure 1.
FIG. 3 is a signal waveform diagram at each part of the circuit in FIG. 2 when there is a raster in the portion shown in FIG.

The circuit operation will be explained with reference to FIGS. 2 and 3. Ordinary horizontal drive in television receivers,
Due to the output operation, the collector voltage of the horizontal drive transistor 4 has a waveform as shown in FIG. 3A. Further, the base current of the horizontal output transistor 5 has a waveform such as B, and the collector voltage has a waveform such as C.
Further, the current waveform at point F shows the primary current waveform of the flyback transformer 10 under heavy load (that is, when the pattern is bright).

Next, consider the current waveform flowing through the capacitor 15 in the distortion correction circuit Y, that is, the current waveform at point D.

During the ON period of the transistor 5, the current from the S-shaped correction capacitor 9 flows through the horizontal deflection coil 8,
The signal flows through the output transistor 5, ground, and the diode 16 to the capacitor 9. Further, the current from the power source 11 flows to the power source 11 through the primary side of the flyback transformer 10, the output transistor 5, and the ground. When the transistor 5 enters the OFF period, the continuous current of the deflection coil 8 charges the resonant capacitor 7. The continuous current from the primary coil of the flyback transformer 10 flows to the ground through the capacitor 7 and the capacitor 15.
to charge. This charging current waveform is shown by a of the D point waveform.

After this, the discharge current from the resonant capacitor 7 is
It flows through the deflection yoke 8 and the S-shaped correction capacitor 9. Part of that is of course the flyback transformer 1.
0, the power supply 11, and the capacitor 15 to the resonant capacitor 7. This current waveform is
The current at point D is indicated by b in the figure.

This current makes the voltage of the distortion correction capacitor 15 zero. This is shown by the voltage e at point F in Figure 3.

The resonance pulse generated during this resonance period is boosted on the secondary side of the flyback transformer 10 and charges the capacitor 13. Naturally, the heavier the secondary load 14 (that is, the brighter the picture), the greater the current that charges the capacitor 13 during this period. The primary inflow current of the flyback transformer 10 under heavy load is shown in FIG. 3 as a point F current.

When the load is heavy, this primary inflow current has a large DC component and injects current into the flyback transformer 10 over almost the entire horizontal period. After the resonance period between the resonant capacitor 7, the horizontal deflection coil 8, and the primary coil of the flyback transformer 10, the damper diode 6 turns on and the damper period begins, as shown in f of the current waveform at point F in Figure 3. The current component is damper diode 6 which is ON,
The current flows through the capacitor 15 and returns to the power supply 11. This current generates a voltage in the capacitor 15, which serves as a distortion correction voltage.

After this, when the horizontal output transistor 5 is turned on, the charge in the capacitor 15 flows through the S-shaped correction capacitor 9, the horizontal deflection coil 8, the output transistor 5, and the ground, and the charge in the capacitor 15 is instantly discharged. Becomes zero. After this, diode 1
6 is turned on, and the current from the deflection coil 8 returns to the S-shaped correction capacitor 9 through the transistor 5, ground, and the diode 16.

As explained above, the horizontal deflection circuit operates.

Now, in case of heavy load, horizontal output transistor 5
During the OFF period, the primary inflow current of the flyback transformer 10 flows into the distortion correction capacitor 15, causing the capacitor 15 to generate a voltage corresponding to the inflow current. Here the screen brightness (high voltage load)
The current flowing into the capacitor 15 changes according to
The voltage across it will change. When the screen is bright, the voltage across the capacitor 15 increases, and accordingly the voltage across the S-shaped correction capacitor 9 decreases, reducing the sensitivity of the horizontal deflection circuit and reducing the horizontal picture size.

Distortion correction is performed through the operations described above.

However, the conventional circuit system described above requires two high-voltage, large-current diodes, such as 6 and 16, and a recently developed horizontal output transistor with a built-in damper diode, which is inexpensive, is needed. Conventional horizontal output circuits with distortion correction circuits were disadvantageous in terms of cost.

Furthermore, when using the conventional horizontal output circuit with a distortion correction circuit as described above, when a bright picture B is displayed in the center of the TV screen as shown in Fig. 4, the distortion correction There is a phenomenon in which a portion becomes an ineffective corner and distortion remains (see the raster position indicated by point b-b' in Fig. 4).

This will be explained below with reference to FIG.
In addition, in Figure 5, the raster is the dark part of the pattern (the fourth
a-a′ in the figure) and bright areas (b-b′ in the same figure)
FIG. 3 is a waveform chart showing a comparison of signal waveforms at various parts of the circuit in FIG.

Figure 5 a-a' shows the distortion correction operation waveforms of each part of the circuit in Figure 2 at point a-a' on the screen in Figure 4, and the distortion correction operation waveform at point b-b' in the same way. Shown in b-b'.

Now, at point a-a' in FIG. 4, the screen is dark, so the high voltage load is light. Therefore, the direct current component to the flyback transformer 10 is small. Therefore, as shown in g of point F in Figure 5 a-a', the power supply 1
There is a return current to 1. When the return current starts to flow during the ON period of the damper diode 6, the voltage across the capacitor 15 is almost zero V as mentioned in the operation explanation above, and most of the return current flows through the diode 16. flows. This is shown at h of point G in FIG. 5 a-a'. This causes the current to return to the power supply 11 through the diode 16, the diode 6, and the primary coil of the flyback transformer 10. That is, when the load is light, the diode 16 is turned on and the voltage across the capacitor 15 becomes approximately 0V during this period.

This condition continues during load conditions where there is a return current from the flyback transformer 10 to the power supply 11. That is, after the diode 16 enters a load state in which it does not turn on, a voltage proportional to the load state is stored in the capacitor 15 to perform distortion correction.

At point b-b' in FIG. 4, there is no sudden increase in load and the diode 16 is turned on. For this reason, distortion correction cannot be applied.

As described above, the conventional circuit system has the disadvantage that distortion correction cannot be effected when the load increases slightly, and distortion remains in the upper part of bright patterns.

[Purpose of the invention]

The present invention has been made to overcome the drawbacks of the prior art as described above, and an object of the present invention is to enable the use of an economical horizontal output transistor with a built-in damper diode, and to It is an object of the present invention to provide a horizontal output circuit with a distortion correction circuit capable of effective distortion correction operation even when a high voltage load increases slightly.

[Summary of the invention]

In order to achieve the above object, the present invention includes a parallel connection circuit of three components: a horizontal output transistor with a damper diode connected in parallel, a series circuit of a horizontal deflection yoke and an S-shaped correction capacitor, and a resonant capacitor. In a horizontal output circuit for a television receiver, a power source is connected at its positive side to the high voltage side of the parallel connection circuit via a flyback transformer primary coil, and the negative side of this power source is connected to the low voltage side of the parallel connection circuit. In between, a third capacitor and a switching element are connected in parallel so that this switching element and the horizontal output transistor are driven with voltages of the same polarity, and when driving, the switching element is connected to the horizontal output transistor. The transistor is turned off before the transistor, and the feedback current from the primary coil of the flyback transformer to the power source does not flow through the switching element, but flows through the third capacitor. There is.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 6 is a circuit diagram showing one embodiment of the present invention.
In the same figure, components given the same reference numerals as in FIG. 2 have the same functions. In addition, 17 is a horizontal output transistor with a damper diode, 18 is a transistor as a switching element, 19 is a horizontal drive transformer, and Y' is a distortion correction circuit added according to the present invention.

FIG. 7 is an operational waveform diagram of each part in the circuit of FIG. 6 when the picture is bright.

The circuit operation will be explained with reference to FIGS. 6 and 7.

Reference numeral 19 is a horizontal drive transformer for driving the circuit according to the present invention. Its secondary winding is 2
One drives the horizontal output transistor 17, and the other drives the distortion correction control transistor 18. The polarity of both secondary windings shall be the same. Figure 8A shows the voltage and current waveforms at each point of the drive transformer.
B and F are shown as having currents of the same polarity flowing through them.

In the above circuit configuration, during the period when the horizontal output transistor 17 is ON, the S-shaped correction capacitor 9
The horizontal deflection current from the horizontal deflection coil 8 returns to the S-shaped correction capacitor 9 through the transistor side of the horizontal output transistor 17 with a built-in damper diode. The signal from the power supply 11 returns to the power supply 11 through the primary side of the flyback transformer 10, through the transistor side of the horizontal output transistor 17, through the distortion correction control transistor 18, and through the ground. During the first period when the transistor 18 is ON, the charge stored in the distortion correction capacitor 15 is also discharged through the transistor 18. This is shown at d in the waveform at point D and d at the waveform at point G in FIG.

Next, when an OFF signal of the same polarity is output to the second winding on the secondary side of the horizontal drive winding, the horizontal output transistor 17,
The transistor 18 turns off, but if the Ts (transistor storage time) of the transistor 18 is shorter than that of the horizontal output transistor 17, the transistor 18 turns off first. Therefore, at this time, the primary current of the flyback transformer 10 flows while charging the capacitor 15. This is shown at i in the waveform at point D in FIG. This current generates a voltage in the capacitor 15, and this voltage acts as a reverse bias voltage for the distortion correction transistor 18.

Then both transistors are turned off. The continuous current in the horizontal deflection coil 8 then charges the resonant capacitor 7. Further, the continuous current of the primary coil of the flyback transformer 10 flows through the resonance capacitor 7 and the distortion correction capacitor 15. This is the seventh
The waveform at point D is shown in a of the figure.

Thereafter, the discharge current of the capacitor 7 will flow through the horizontal deflection coil 8 and the S-shaped correction capacitor 9. Some of them are of course the primary side of the flyback transformer 10, the power supply 11, the ground, and the capacitor 1.
It will flow through 5. This current is shown by d in the current waveform at point D in FIG.

The resonance pulse generated during this resonance period is boosted on the secondary side of the flyback transformer 10 and charges the capacitor 13. It goes without saying that the heavier the secondary load 14, the greater the current that charges the capacitor 13 during this period.

Naturally, during the OFF period of the horizontal output transistor 17, the distortion correction control transistor 18 is also OFF, and the flyback transformer 10 is turned OFF during this period.
All of the primary current flows through the distortion correction capacitor 15.

In this way, distortion can be corrected by generating a voltage in the capacitor 15 in accordance with the load, similar to the conventional circuit system.

Next, when the horizontal output transistor 17 turns on, the distortion correction control transistor 18 also turns on, discharging the charge in the capacitor 15 and resetting it. In this way, the horizontal deflection operation in the television receiver continues.

With the above configuration, the voltage across the capacitor 15 changes with the high voltage load, and the voltage of the S-shaped correction capacitor 9 can be modulated accordingly, and the distortion correction effect can be effected, as in the conventional circuit system. can.

In the case of light load (when the DC component to the flyback transformer 10 is small), the primary current of the flyback transformer 10 is fed back to the power supply 11 during the damper period as in the conventional case, but at this time, the capacitor 15 The horizontal output transistor 17 is
When the distortion correction control transistor 18 is turned on and turned off, almost the voltage charged by the power supply 11 remains, and this is shown as e in the waveform at point E in FIG. That is, a reverse bias is applied to the distortion correction control transistor 18. In other words, the voltage is rising between the collector and base of the transistor 18, and therefore,
All of the feedback current to the power source 11 flows through the capacitor 15 while discharging the charge stored in the capacitor 15 in advance.

At medium load, flyback transformer 1
The feedback current from 0 to the power supply 11 decreases (because the DC component to the flyback transformer increases), but at this time too, all the current flows through the capacitor 15, reducing the capacitor charge.

However, when the load is medium, the feedback current to the power supply 11 is smaller than when the load is light, and the amount of discharge from the capacitor 15 is also smaller. This corresponds to an increase in the voltage across the capacitor 15 due to the medium load.

When the load is heavy, there is no feedback current to the power source 11, and current flows from the power source 11 into the flyback transformer 10 over the entire horizontal cycle. At this time, the control transistor 18 is naturally turned off and the capacitor 15 is charged.

With the circuit configuration shown above, the horizontal output transistor 17 can be used from light loads to heavy loads.
All the primary current of the flyback transformer flowing when it is OFF can be passed to the distortion correction capacitor 15, and the capacitor voltage can be changed according to the load to faithfully correct distortion.

FIG. 8 is a circuit diagram showing a modified embodiment of the present invention. In the circuit shown in the figure, the horizontal excitation transformer 3 has one secondary coil, but the transistors 17,
This embodiment is the same as the embodiment shown in FIG. 6 in that voltages of the same polarity are applied to each base of transistor 18, and that transistor 18 is turned off before transistor 17. In other words, the circuit operation is no different from that shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, an economical transistor with a built-in damper diode can be used, and the distortion correction control transistor can be supplied with only the primary inflow current of the flyback transformer and the discharge current of the distortion correction capacitor. It can be easily made compact, and therefore the entire circuit can be constructed at low cost. In addition, by using a transistor with a shorter Ts (storage time) than the horizontal output transistor for the distortion correction control transistor and turning it off first, the screen can be faithfully maintained from light to heavy loads without configuring a complicated circuit. distortion correction can be performed.

Furthermore, by connecting a current limiting resistor in series with the distortion correction capacitor, the capacity of the distortion correction control transistor can be further reduced, and costs can be reduced accordingly.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a TV screen when distortion correction is not performed, Figure 2 is a circuit diagram showing a conventional horizontal output circuit equipped with a distortion correction circuit, and Figure 3 is a signal waveform at each part of the circuit in Figure 2. Figure 4 is an explanatory diagram of a TV screen when using a conventional horizontal output circuit with distortion correction circuit, and Figure 5 shows when the raster is in the dark part of the picture and in the bright part. A waveform diagram showing a comparison of signal waveforms in each part of the circuit shown in the figure,
FIG. 6 is a circuit diagram showing one embodiment of the present invention, FIG. 7 is a waveform diagram of each part of the circuit in FIG. 6 when the pattern is bright, and FIG. 8 is a circuit diagram showing a modified embodiment of the present invention. be. Explanation of symbols 15... Distortion correction capacitor, 18...
Transistor for distortion correction control.

Claims (1)

[Claims] 1. A horizontal output circuit for a television receiver that includes a parallel connection circuit of three components: a horizontal output transistor with a damper diode connected in parallel, a series circuit of a horizontal deflection yoke and an S-shaped correction capacitor, and a resonant capacitor. A power source is connected on the positive side to the high voltage side of the parallel connection circuit via a flyback transformer primary coil, and a third capacitor and a switching circuit are connected between the negative side of the power source and the low voltage side of the parallel connection circuit. The elements are connected in parallel, and the switching element and the horizontal output transistor are driven with voltages of the same polarity,
During driving, the switching element is turned off before the horizontal output transistor, so that the feedback current from the primary coil of the flyback transformer to the power supply does not flow through the switching element, and the third capacitor is turned off. A horizontal output circuit characterized in that the current flows on the side of the horizontal output circuit.