JPS6056348B2 - Vertical deflection circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vertical deflection circuit used in television receivers, which prevents neck cracks in cathode ray tubes that occur during abnormal conditions, and which uses a circuit added to prevent this from occurring. The aim is to eliminate the inconveniences that arise.

In the vertical deflection circuit, the direct current and alternating current components of the vertical output signal are fed back to correct the midpoint level of the vertical deflection current waveform and the shape of the current waveform itself, and the former stabilizes the vertical center position of the screen. In the latter case, a circuit that automatically corrects vertical linearity has already been implemented.

The one shown in FIG. 1 is an example. In FIG. 1, the numbers attached to the sides of each electric element are in Ω for resistance and in farad for capacitors.

A synchronization pulse from a synchronization separation circuit (not shown) is supplied to the input terminal a of the vertical synchronization separation circuit 1, and the integrating capacitor 15
is used to separate the vertical synchronizing pulse and use it as a trigger signal for the vertical oscillation circuit 2. The vertical oscillation circuit 2 is configured, for example, of a multi-oscillation type, and its time constant is controlled by a capacitor 18 and resistors 16 and 17, and the variable resistor 16 functions as a vertical synchronization adjustment volume. The output pulse of the vertical oscillation circuit 2 synchronized with the vertical synchronization pulse is supplied to the sawtooth wave generation circuit 3, which generates a sawtooth wave with good linearity of the time constant controlled by the variable resistor 19, the resistor 20, and the capacitor 21. It is supplied to one side of the circuit 4 as a reference sawtooth wave. At the other terminal (b terminal) of the comparator circuit 4, a feedback circuit configured with resistors 8, 10, 12, and capacitors 9, 11, and 13 detects the direct current and alternating current flowing through the vertical deflection coil 7. , is provided as a comparison sawtooth waveform (feedback of the output waveform). The reference sawtooth wave and the comparison sawtooth wave (output waveform feedback) are compared in a comparator circuit 4, and the vertical sawtooth waveform with vertical linearity and midpoint voltage (DC bias) corrected is supplied to a vertical drive circuit 5. The signal is amplified and further supplied to the vertical output circuit 6 to cause a vertical deflection current (sawtooth wave) to flow through the vertical deflection coil 7. The diode 22, capacitor 23, and pulse amplification circuit 14 are
As the power supply for the vertical output circuit 6, a voltage of 48 volts peak (24 volts only during the vertical retrace period, otherwise) is provided, but the details are omitted since it is not relevant to the present invention. Since the vertical synchronization separation circuit 1, vertical oscillation circuit 2, sawtooth wave generation circuit 3, etc. are already known, detailed circuit configurations will be omitted.

FIG. 2 shows the circuit configuration of the comparison circuit, the vertical drive circuit 5, and the vertical output circuit 6.

Further, FIG. 3 shows waveform diagrams of various parts. In Fig. 2, the differential amplifier composed of transistors 24 and 25 is a comparator circuit, and the base of transistor 24 has a reference sawtooth wave (Fig. 3 A), and the base of transistor 25 has a current flowing through a vertical deflection coil. A comparison sawtooth wave (Figure 3) detected and fed back is added.

The output of the comparator circuit 4 is transmitted through transistors 26, 27, 28,
It is connected through 29 to the base of a transistor 30 forming a vertical drive circuit. The signal applied to the base of transistor 30 (FIG. 3C) is inverted and applied to the base of transistor 30.
A deflection current is supplied to the deflection coil 7 through 2 and 33.
The voltage waveform at the emitter of the transistor 33 is as shown in FIG. The above is an outline of the operation of the vertical deflection circuit. Now, in the above circuit, if the intersection of the capacitor 9 and the resistor 8 becomes ground potential for some reason (for example, if the capacitor 9 is short-circuited), the transistor 25 in the comparator circuit 4 will be cut off, and the transistor 30 will be cut off. Since ground potential is applied to the base of transistor 30 and transistor 30 is cut off, transistor 3
3 emitters. becomes a constant high voltage, and a direct current flows through the deflection coil 7. In this state, the vertical line becomes a horizontal line, and its position is upward on the cathode ray tube surface. In other words, the electron beam will be concentrated on the upper part of the neck and will break the neck glass! Ru. In order to prevent such neck cracking, a circuit shown in FIG. 4 was devised.

In FIG. 4, at the intersection of the deflection coil 7 and the capacitor 9, there is a cathode of a diode 42, a resistor 38, and a variable resistor 39.
The anode of a diode 42 is connected to the intersection of .

The variable resistors 37 and 39 and the resistors 38 and 40 provide a DC voltage for controlling brightness to the brightness control circuit 36, and the voltage at the intersection of the resistor 38 and the variable resistor 39 is supplied to the brightness DC control circuit 36. Ru.

Also, ABl. Control circuit is connected. In this embodiment, the brightness control voltage becomes brighter as the voltage increases, and the normal brightness setting voltage is 7 to 8 volts. In this case, for example, the variable resistor 37 is used for brightness adjustment, and the variable resistor 39 is used for sub-brightness adjustment.

In the normal case, the cathode voltage of the diode 42 is higher than the anode voltage, so the diode 42 is cut off, and the brightness is no different from normal brightness. For example, if the capacitor 9 is short-circuited and the voltage at the intersection of the deflection coil 7 and the capacitor 9 becomes close to the ground potential (
(because the impedance of resistor 10 is low), diode 4
2 conducts, lowering the voltage across the resistor 38 and variable resistor 39 (brightness control voltage) to around the diode forward voltage (approximately 0.7 volts). Since this voltage is used together with the brightness control voltage, in this case the brightness is reduced and the beam no longer flows, thus achieving the purpose of preventing the neck glass from breaking. However, in the above circuit, vertical oscillation is stopped when horizontal adjustment (low light adjustment) is performed, and at this time, the intersection voltage between deflection coil 7 and capacitor 9 is a DC voltage lower than normal (about 5 volts). In the case of 1), the diode 42 becomes conductive, the brightness control voltage decreases, the screen becomes completely dark, and the raster cannot be viewed and horizontal adjustments cannot be made.

The present invention has been made in view of the above-mentioned drawbacks, and the present invention has been made in view of the above-mentioned drawbacks.
When the intersection voltage of and capacitor 9 is close to the ground potential, the brightness control voltage is lowered, and when horizontal adjustment is made, the brightness control voltage is not lowered. An example is shown in Fig. 5. show.

As shown in FIG. 5, the cathode side of the diode 42 is connected to the intersection of the deflection coil 7 and the capacitor 9, one end of the resistor 43 is connected to the anode side of the diode 42, and the resistor 43 is connected to the anode side of the diode 42.
The other end of the resistor 3 is connected to the intersection of the resistor 38 and the variable resistor 39.
As the resistor 43, a resistor of 10 KΩ is used to produce a voltage drop of, for example, 5.1 volts. With the circuit configured in this way, when horizontal adjustment is performed, the voltage at one end of the variable resistor 39 side of the resistor 43 is approximately 7 volts, the voltage at the cathode side of the diode 42 is approximately 5 volts, and the voltage at the end of the variable resistor 39 side of the resistor 43 is approximately 5 volts, is not conductive. 5.1 volts+ for continuity
A potential difference of 0.7 volts to 5.8 volts or more is required. Since it is necessary to obtain a predetermined voltage drop as the resistor 43, it is generally more convenient to use a Zener diode.

However, using a Zener diode causes the following drawbacks. That is, when the capacitor 9 is short-circuited and the cathode voltage of the diode 42 decreases, the variable resistor 39,
The current flowing through the Zener diode, the diode 42, and the deflection coil 7 is 110n1A, and if the value of the variable resistor 39 is about 1KΩ, the power consumption is about 10W, and if it exceeds the rating, it will burn. Therefore, the present invention uses a resistor 43 instead of the Zener diode to limit the current to about 9n1A and prevent the variable resistor 39 from burning out. As described above, according to the present invention, even if the voltage of the feedback circuit of the vertical deflection circuit decreases, the screen of the cathode ray tube darkens, so that the neck of the cathode ray tube will not break.

Also, when adjusting low light by displaying a horizontal display on the cathode ray tube screen, a resistor is connected in series with the diode to prevent this circuit from working, so the cathode ray tube screen becomes completely dark. You will never become unable to adjust the low light. Furthermore, since the current is limited by the resistor, the variable resistor of the circuit that controls the brightness of the tube surface of the cathode ray tube will not burn out.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional vertical deflection circuit device, Fig. 2 is a specific circuit diagram of a part of the same device, Fig. 3 is a waveform diagram for explaining the same device, and Fig. 4 is a diagram of a conventional vertical deflection circuit device. FIG. 5 is a circuit diagram of a vertical deflection circuit device according to an embodiment of the present invention. 4... Comparison circuit, 5... Vertical drive circuit, 6... Vertical output circuit, 7... Vertical deflection coil, 8, 9, 10, 11, 12 , 13...Resistance and capacitor for feedback circuit, 42...
...Diode, 43...Resistor, 39...
...Variable resistance.

Claims (1)

[Claims] 1. A feedback circuit is provided to correct the vertical deflection current by feeding back the output of the vertical deflection circuit to the previous stage, and the feedback circuit of the feedback circuit is connected between the feedback circuit and the brightness control DC voltage input terminal of the brightness control circuit. It is characterized by connecting a series circuit of a diode and a resistor that becomes conductive when the voltage falls below a certain voltage and changes the potential of the control DC voltage input terminal in a direction that darkens the brightness of the screen of the cathode ray tube. vertical deflection circuit device.