JPS60134666A - Display device - Google Patents

Abstract

PURPOSE:To make a size constant irrespective of brightness of a picture by changing the magnitude of vertical deflection current by voltage corresponding to the beam current of a cathode ray tube. CONSTITUTION:When the brightness of a picture increases and a beam current increases, voltage drop of a resistor 11 becomes larger. This voltage is led through the buffer of a Tr22 and utilized. The voltage obtained in the emitter of the Tr22 is regulated by resistors 20 and 19 and fed to an N-FET18 gate. Thus, when the brightness of picture changes, the gate voltage of the FET18 changes and the resistance between drain sources changes. At it is connected to the feedback path of an IC for vertical oscillation pre-amplification 16 through a condenser 17, saw tooth voltage for feedback AC changes with the brightness of the picture. For instance, when a picture becomes brighter, feedback saw tooth wave components becomes larger, and the vertical deflection current becomes smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a display device equipped with a cathode ray tube, and relates to a display device whose vertical size is kept constant even if the screen brightness changes.

[Background of the invention]

It has been said that the high voltage of the cathode ray tube fluctuates when the screen brightness changes. When the screen becomes brighter and the high voltage drops,
Deflection sensitivity increases and the screen size becomes larger. In order to prevent this, a resistor is inserted into the power supply line to the horizontal output circuit to correct the size in the horizontal direction.

Until now, no measures have been taken to deal with size changes in the vertical direction. Therefore, when a bright screen is sent, #i
The screen may stretch and cause an abnormal screen.

[Purpose of the invention]

An object of the present invention is to provide a constant size regardless of the brightness of the screen by changing the magnitude of the vertical deflection current using a voltage corresponding to the beam current of the cathode ray tube.

[Summary of the invention]

Since the vertical size changes depending on the screen brightness, a voltage corresponding to the brightness is used as a detection source, and this voltage changes the feedback AC sawtooth voltage amplitude from the vertical output stage, and the vertical i#
The above objective is achieved by varying the magnitude of the 1iI01 current.

[Embodiments of the invention]

The figure is a circuit diagram showing one embodiment of the present invention.

The parts other than those surrounded by dotted lines are conventional vertical deflection circuits and cathode ray tube peripheral circuits.

First, the operation of a conventional vertical deflection circuit will be explained using FIG. 16 is an IC for vertical excavation and preamplification; 1, for example (
Hitachi, Ltd. glcHA11423 was used.

1 is a vertical deflection coil, 2 is a capacitor, and 3 is a resistor for detecting the deflection current.

The DC voltage including the ripple generated by the capacitor 2Kj@- is applied to the resistor 4. It is smoothed by capacitor 5.

・　3　・ is negatively fed back to the vertical excitation stage in IC16.

Further, the alternating current harmonic wave voltage of the resistor 3 through which the vertical deflection current flows is divided into two parts and superimposed on the above-mentioned direct current voltage. I
In C16, the feedback voltage from the output stage, which is a mixture of DC and AC components, is compared with the sawtooth wave voltage of vertical oscillation,
The differential is routed to a preamplifier to drive the vertical output circuit.

The output circuit is generally configured with an NPN transistor and a PIVP transistor.

Here, the DC component of the feedback voltage has the role of determining the DC bias voltage of the output circuit.

Also, the sawtooth wave component of the alternating current has the role of determining the vertical amplitude. When the sawtooth wave component becomes small, the difference compared within the IC 16 becomes large.

The deflection sawtooth current becomes large and its amplitude becomes large. By varying the value of the resistor 10, only the vertical size can be varied without changing the DC bias according to the above equation.

The resistor 11 is connected to the high voltage winding m of the flyback transformer 15, and as one screen becomes brighter and the beam current increases, the voltage drop across the resistor 11 increases. Generally, this voltage is used as the detection voltage of the beam current limiting circuit. In this embodiment, this voltage is conducted through a transistor 220 buffer and used.The voltage obtained at the emitter of one transistor 22 is adjusted by a resistor 20 and a resistor 19, and is applied to the gate of an N-channel field effect transistor 18.

The field effect transistor 18 has a property that the resistance value between the drain and the north changes depending on the voltage applied between the gate and the source.

It is also said that bidirectional current can flow between the drain and source.

The N-channel field effect transistor 18 is a Ge.4 transistor.
- When the voltage between one tone and the source decreases, the resistance between the drain and source increases.

As described above, when the brightness of one screen changes, the gate voltage of the field effect transistor 18 changes, and the resistance between the drain and the north changes. Since it is connected to the return path through the capacitor 17, the sawtooth voltage of the feedback exchange changes according to the above equation according to the brightness of the screen. For example, when the screen becomes brighter, the gate voltage of the field effect transistor 18 decreases and the drain-source resistance increases. The feedback sawtooth wave component becomes large, and the vertical deflection current becomes small due to the watered raw salt.

From the above, even if the screen brightness changes, the vertical deflection current can be increased.
Since it can change small, it is possible to maintain a constant size regardless of the brightness.

In addition, in this embodiment, of the oscillation stage output and the feedback amount that are compared with each other, the feedback amount may be made to correspond to the beam current, or conversely, the oscillation stage output may be made to correspond to the beam current. In this case, for example, the oscillation stage may be configured such that the gain of the excavation stage corresponds to the am control pressure.

〔Effect of the invention〕

As described above, according to the present invention, the capacitor 17 cuts off the DC current, and the field effect transistor 1B, which is a bidirectional 1'' variable resistance element, is used, so the AC current can be transferred without changing the DC component of the feedback voltage. This can only be changed by changing the DC bias of the output circuit. Vertical vibration is 1
It is possible to make only the amplitude diamond-shaped without any harshness.

In addition, as shown in the examples, it can be realized with a simple circuit configuration, so it has high industrial value, and when incorporated into an IC,
It has the advantage of extremely low implementation costs.

[Brief explanation of the drawing]

The figure is a circuit diagram showing one embodiment of the present invention. 1... Vertical deflection coil 2... Capacitor 6...
Resistor 4... Resistor 5... Capacitor 6... Resistor 7... Resistor 8... Resistor? ... Capacitor 10 ... Vertical line 1t@M East resistor 11 ... Beam current detection resistor 12 ... Capacitor 13 ... Flyback transformer 14 ... High voltage rectifier diode 15 ... Braun tube 16 ...・Vertical oscillation/preamplification IC 17...DC cut capacitor 18...N-channel junction field effect transistor 1
9...Resistor 20...Resistor 21...Resistor 22...Transistor

Claims (1)

[Claims] t: a cathode ray tube, a vertical deflection coil coupled to the cathode ray tube, a current supply means for supplying a vertical deflection current to the vertical deflection coil, a detection means for detecting fluctuations in a beam current flowing through the cathode ray tube, and a beam 1. A display device comprising: control means for controlling current supply means using the output of the detection means so that vertical deflection current amplitude decreases or increases in accordance with increase or decrease in current. 2. The current supply means has a vertical excitation stage and a vertical output stage, and the amount of negative feedback fed back from the vertical output stage to the vertical excitation stage is controlled by a control means. The display device according to item m1. 3. Claim 1, characterized in that the current supply means has a vertical oscillation stage, and the gain of the vertical oscillation stage is controlled by the control means! Display device mounted on Ia.