JPS62145971A - Vertical deflection width controlling circuit - Google Patents

Abstract

PURPOSE:To obtain a stable image without variation in vertical deflection width even when a high-voltage fluctuation occurrs because of a variation in brightness of a cathode-ray tube by deriving a DC voltage to determine the vertical deflection width from the windings of a flyback transformer. CONSTITUTION:The pulse voltage from the secondary winding of the flyback transformer 7 is rectified by a diode 18 and smoothened by a capacitor 19, then voltage-divided by resistors 22 and 23, and inputted to the base of a transistor 20 together with a DC voltage from a DC power source terminal 12. The DC voltage to determine the vertical deflection width is thus amplified by the transistor 20, added with a sawtooth voltage from a deflection output circuit 11, and impressed to the capacitor 17. The capacitor 17 is charge/discharged by a lamp generator in a vertical deflection voltage generating circuit 10 to generate the saw tooth voltage of a magnitude and linearity corresponding the DC voltage supplied from the transistor 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention applies to cathode ray tubes (hereinafter referred to as CR) of television receivers, etc.
The present invention relates to a vertical deflection width control circuit (referred to as T) for controlling the vertical deflection width of a display device, and particularly relates to suppressing vertical deflection width fluctuations in response to changes in screen brightness.

[Prior Art] Fig. 3 is a circuit diagram showing a conventional vertical deflection width control circuit in partial blocks.
) is its acceleration electrode, (3) is the vertical deflection coil, (
4) is a horizontal deflection coil, (5) is a horizontal deflection circuit, (6)
is the flyback transformer, (7) (7') is its −
Next.

Secondary winding, (8) is a rectifier diode, (9) is a high voltage circuit, (lO) is a vertical deflection voltage generation circuit, (11) is a vertical deflection output circuit, (lla) is its input terminal, (Ilb)
is its output terminal, (11c) is its feed bank terminal, (12) is the stabilized DC power supply terminal, (13)
(14) (1, 5) are fixed resistors, (16) are variable resistors for adjustment, and (17) are capacitors. Next, its operation will be explained. Accelerating electrode (2) of CRT (1) (2
The high voltage to
includes a vertical deflection output circuit (11) and a horizontal deflection circuit (5).
The output voltage causes a sawtooth current to flow, which deflects the accelerated electron beam.

A voltage proportional to the output sawtooth current from the vertical deflection output circuit (11) is output from the feedback terminal (llc), and this voltage is shifted by the voltage from the DC power supply terminal (12) by an amount corresponding to its magnitude. The voltage is applied to the capacitor (17) through the adjustment variable resistor (16) and the resistor (15). The capacitor (17) is connected to a sawtooth voltage generating ramp generator in the vertical deflection voltage generating circuit (10), and this ramp generator is connected to the capacitor (
17) to generate a sawtooth wave voltage with good linearity according to the magnitude and waveform of the voltage applied to the capacitor (17) via the resistors (13) to (16). The vertical deflection voltage generating circuit (10) compares this sawtooth wave voltage with the voltage of the feedback circuit, and outputs a waveform voltage that causes a current proportional to this voltage to flow through the vertical deflection coil (3). The voltage is applied to a vertical deflection output circuit (11), and the vertical deflection coil (3) is driven by this circuit (11).

The vertical deflection width of C RT (1) vertically deflected in this way is proportional to the amplitude of the sawtooth wave current flowing through the vertical deflection coil (3), which is proportional to the voltage applied to the capacitor (17), That is, it is determined by the magnitude of the voltage at the power supply terminal (12), which is adjusted by the variable resistor (16).

[Problems to be Solved by the Invention] The conventional vertical deflection width control circuit is configured as described above, and the flyback transformer (8) and High voltage circuit (
9) The load changes, which causes the generated high voltage to fluctuate. The vertical deflection width also fluctuates due to fluctuations in the electron beam acceleration voltage of this high-voltage CRT (1), causing problems such as the vertical width of the screen widening when the screen is bright, and conversely shrinking when the screen is dark. Ta.

This invention was made to solve the above-mentioned problems, and provides a vertical deflection width control circuit that can maintain a stable vertical deflection width even when high voltage fluctuations occur due to changes in CRT brightness. The purpose is to

[Means for Solving the Problems] In the vertical deflection width control circuit according to the present invention, the DC voltage that determines the vertical deflection is taken out even from the winding of the flyback transformer.

[Function] In this invention, since the DC voltage that determines the vertical deflection width is taken out from the winding of the flyback transformer, the voltage from the winding of the flybank transformer is reduced due to high voltage fluctuations caused by changes in the brightness of the CRT, etc. It is possible to compensate for changes in the vertical deflection width due to fluctuations in the CRT acceleration voltage and maintain a stable vertical deflection width at all times.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention in partial blocks.
) is similar to the conventional circuit. (7") is the secondary winding of the flyback transformer (7), (18) is the diode that rectifies the voltage from this winding (7"), (19)
) is a smoothing capacitor, (20) is a transistor,
(21) (22) (23) (24) (25) is the resistance,
(26) is a DC power supply terminal for the transistor (20).

Next, its operation will be explained. The pulse voltage from the secondary winding (7") of the flyback transformer (7) is rectified by a diode (18) and smoothed by a capacitor (19). It is then divided by resistors (22) and (23).
The stabilized DC voltage from the DC power supply terminal (12) is input to the base of the transistor (20) together with the voltage adjusted by the variable resistor (16). The DC voltage that thus determines the vertical deflection width is amplified by the transistor (20), appears at its collector terminal, and is added to the sawtooth voltage from the feedback terminal (lie) of the vertical deflection output circuit (11). Applied to the capacitor (17). This capacitor (17) is charged and discharged by a lamp generator in the vertical deflection voltage generation circuit (10).
A sawtooth wave voltage is generated whose magnitude and waveform linearity correspond to the DC voltage supplied from the terminal (llc) and the transistor (20). This voltage is compared in the vertical deflection voltage generation circuit (10) with the waveform from the feedback circuit that is input separately, and outputs a waveform that operates the vertical deflection output circuit (11). Drive the deflection coil (3). This vertical deflection coil (
The vertical width deflected by the capacitor (17)
), and this voltage varies depending on the magnitude of the pulse voltage from the flyback transformer winding (7"). Therefore, if the brightness of the CRT (1) becomes brighter, for example, the flyback transformer The load on (6) increases and the output voltage of high voltage circuit (9) decreases, causing the CRT to
(1) The acceleration voltage decreases and the vertical deflection width of the electron beam tends to widen. On the other hand, flyback transformer winding (7”)
The magnitude of the pulse voltage from the capacitor (17) also decreases, which is rectified and amplified by the transistor (20), and the magnitude of the DC voltage applied to the capacitor (17) also decreases. As a result, the vertical deflection voltage that drives the vertical deflection coil (3) through the circuits (10) and (11) also decreases, and the vertical deflection width of the CRT (1)' Ili beam tends to narrow. In this way, changes in the vertical deflection width caused by high voltage changes due to changes in the brightness of the CRT (1) can be completely suppressed.

FIG. 2 is a circuit diagram showing another embodiment of the present invention, in which the DC power terminal (12') (12") is
This embodiment differs in that a variable resistor (16') (16") for adjustment is added. This embodiment uses a DC power terminal (12) for a CRT display such as a personal computer.
When applying different voltages to (12') and (12'') to change the vertical width, or when connecting signal sources with multiple different timing charts to the display,
Since the vertical width may change depending on the timing chart, the DC power is applied to the terminals (12) (12') (12") each time the timing chart is changed, and the width can be varied according to each timing chart. If you adjust the resistors (16) (16') (16'''),
The vertical width can be the same.

In each of the above embodiments, the DC power supply terminals (12) (12'
) (12"), but this terminal can also be used as a ground terminal. Also, if you do not need to manually adjust the vertical width of the screen, use a variable resistor. (16) may be a fixed resistor, or the power supply terminal (12) and variable resistor (16) may be omitted if the voltage division of the voltage dividing resistors (22) and (23) can be set appropriately.

[Effects of the Invention] As described above, according to the present invention, the DC voltage that determines the vertical deflection width is taken out from the winding of the flyback transformer, so even if there is a high voltage fluctuation due to a change in the brightness of a CRT, the vertical deflection can be maintained. This has the effect of providing a stable image with no change in width.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention in partial blocks, FIG. 2 is a circuit diagram showing another embodiment of the invention in partial blocks, and FIG. 3 is a conventional vertical deflection width control circuit. FIG. 2 is a circuit diagram showing some blocks. In the figure, (1) is a cathode ray tube (CRT), (2) (2
) is an accelerating electrode, (3) is a vertical deflection coil, (4) is a horizontal deflection coil, (6) is a flyback transformer, (7
) (7') (7") is its winding, (9) is the high voltage circuit, (10) is the vertical deflection voltage generation circuit, (11) is the vertical deflection output circuit, (12) is the DC power supply terminal, ( 16) is a variable resistor for adjustment, (17) is a capacitor, (18) is a rectifier diode, (19) is a smoothing capacitor, (20)
are transistors, and (21) to (25) are resistors. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] (1) The vertical deflection width is determined in a vertical deflection width control circuit that controls the vertical deflection width of the cathode ray tube display device according to the DC voltage by rectifying the flyback transformer secondary winding voltage and using it as the accelerating voltage of the cathode ray tube. A vertical deflection width control circuit characterized in that a DC voltage is extracted from the winding of the flyback transformer. (2) The DC voltage that determines the vertical deflection width is extracted from the flyback transformer winding via a diode, adjusted by a variable resistor for vertical deflection width adjustment, and extracted via a transistor. A vertical deflection width control circuit according to claim 1. (3) A plurality of variable resistors for vertical deflection width adjustment are provided and are appropriately switched and connected.
Vertical deflection width control circuit described in .