JP2773323B2 - Dynamic focus voltage generation circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus voltage generation circuit suitable for a television receiver having a large screen size.

[Summary of the Invention]

The present invention provides a dynamic focus voltage generation circuit for an electron beam of a cathode ray tube suitable for application to a television receiver having a large screen size, a switching element,
A diode, a first capacitor, and a circuit in which a second capacitor is connected in series to a first terminal of a primary coil of a transformer are connected in parallel, and a second terminal of the primary coil is connected to a power supply. By connecting the connected coil and supplying a horizontal synchronization pulse to the switching element and obtaining the dynamic focus voltage from the secondary coil of the transformer, it is possible to obtain a good dynamic focus voltage suitable for a cathode ray tube having a large screen with a small loss. It was made.

[Conventional technology]

In general, a cathode ray tube used in a television receiver or the like has a different electron beam reaching distance between a central portion and a peripheral portion of a screen. Focus becomes sweet at the periphery. For this reason, a horizontal focus signal is integrated by a dynamic focus voltage generation circuit, then amplified by a transistor, and further boosted by a transformer to generate a parabolic wave (quadratic curve) of a horizontal scanning cycle. The dynamic focus correction is performed by adding a focus electrode.

[Problems to be solved by the invention]

However, a parabolic wave having a quadratic curve obtained by such a conventional dynamic focus voltage generation circuit may not be able to perform sufficient correction. That is, in a television receiver having a large screen size, if dynamic focus correction is performed using a parabolic wave of a quadratic curve, even if the focus is appropriate at the center and both ends of the screen, the center of the screen is not In some cases, the focus became weak at the portion between the ends.

Further, in the case of a television receiver having a large screen size, a very high voltage is required as a dynamic focus voltage, and ringing occurs at the time of step-up by a transformer, and power consumption is large.

An object of the present invention is to obtain a good dynamic focus voltage with a simple configuration.

[Means for solving the problem]

In the present invention, for example, as shown in FIG. 1, a switching element (3), a diode (5), a first capacitor (6), and a second capacitor (7) are connected to a primary coil of a transformer (4). The first terminal of the transformer is connected in parallel with a circuit connected in series, the second terminal of the primary coil of the transformer (4) is connected to a coil (8) connected to a power supply, and the switching element (3) Supplies a horizontal sync pulse to the transformer (4)
The dynamic focus voltage is obtained from the secondary coil.

[Action]

By doing so, a dynamic focus voltage that rapidly rises at both ends of each horizontal cycle based on the horizontal synchronization pulse is obtained, and a dynamic focus voltage suitable for a large cathode ray tube is obtained.

〔Example〕

Hereinafter, an embodiment of a dynamic focus voltage generating circuit according to the present invention will be described with reference to the accompanying drawings.

In FIG. 1, (1) indicates a horizontal synchronizing pulse input terminal. A horizontal synchronizing pulse of a horizontal scanning cycle supplied to this input terminal (1) is supplied to a horizontal deflection circuit (2), and a cathode ray tube (shown in FIG. A deflection current to be supplied to the horizontal deflection coil is generated by the horizontal deflection circuit (2).

Then, the horizontal synchronizing pulse supplied to the input terminal (1) is supplied to the control electrode of the field effect transistor (3) constituting the switching element of the dynamic focus voltage generating circuit of the present example. This field effect transistor (3)
Has a damper diode (5), a first capacitor (6), and a series circuit of a primary winding (4a) of a transformer (4) and a second capacitor (7) connected in parallel. It is. Then, a terminal (9) from which a DC power supply + B is obtained is connected to one end of this parallel circuit via a choke coil (8), and the other end of this parallel circuit is grounded.

Then, one end of the secondary winding (4b) of the transformer (4) is
It is connected to a dynamic focus voltage output terminal (11) via a third capacitor (10), and a voltage signal obtained at this output terminal (11) is supplied to a focus electrode of a cathode ray tube. An input terminal (12) to which a vertical synchronization signal is supplied
Is grounded through a series circuit of a coil (13) and a fourth capacitor (14), and a connection point between the coil (13) and the fourth capacitor (14) is connected to an NPN transistor (15). )
And the emitter of the transistor (15) is grounded via a resistor (16) and connected to the other end of the secondary winding (4b) of the transformer (4). Further, the terminal (17) from which the power supply voltage Vcc is obtained is connected to the transistor (1
5) Connect to the collector. By doing so, the vertical synchronizing signal supplied to the terminal (12) is integrated by the coil (13) and the capacitor (14) to be a parabolic wave having a vertical period, and this parabolic wave is converted into the parabolic wave of the transformer (4). By being supplied to the other end of the next winding (4b), the dynamic focus voltage obtained at the output terminal (11) becomes a signal modulated by a parabolic wave having a vertical period.

Here, an example of the constants of this circuit when used for a cathode ray tube for a high-definition television having a horizontal frequency of 33.75 kHz is shown as follows.
DC voltage + B = 100V, 10mH for choke coil (8), 1st
The capacitor (6) of 14000PF, the second capacitor (7)
0.1F, and the ratio between the primary and secondary windings of the transformer (4)
Set to 1: 7.

Next, the operation of the dynamic focus voltage generating circuit of this example will be described with reference to FIGS. 2 to 4. By supplying a horizontal pulse signal obtained at the terminal (1) to the field effect transistor (3), This field effect transistor (3)
Are turned on / off in a horizontal cycle, and an output waveform F of a voltage as shown in FIG. 2 is obtained at an output terminal (11) via a transformer (4). That is, the start and end portions of each horizontal scanning period (1H) rise sharply, and a signal having a peak-to-peak value of, for example, 3.2 kV is obtained at the output terminal (11). In this case, as shown in FIG. 3, by changing the capacity of the first capacitor (6), the height and width of the rapidly rising portion change along the arrows a and b, and the second By changing the capacity of the capacitor (7), the curvature at the center changes along the arrow c. For this reason, the dynamic focus voltage waveform output from the terminal (11) can be adjusted according to the required characteristics of the cathode ray tube, and the dynamic focus voltage waveform which sharply rises at both ends of each horizontal cycle suitable for a large cathode ray tube can be adjusted. The focus voltage is obtained. In this case, since the primary side of the transformer (4) is incorporated in a part of the resonance circuit, the dynamic focus voltage generation circuit operates with low loss.

Further, in this example, a parabolic wave having a vertical period is supplied to the other end of the secondary winding (4b) of the transformer (4), so that the dynamic voltage changes as shown in FIG. 2 in each horizontal scanning period. The overall level of the focus voltage waveform F is
It changes along the parabolic wave as shown in FIG. 4 every one vertical period (1 V). Therefore, the dynamic focus correction in the vertical direction is simultaneously performed by the dynamic focus voltage waveform F supplied to the terminal (12).

The adjustment of the waveform of the dynamic focus voltage supplied to the terminal (12) is performed in addition to the adjustment of the capacitances of the capacitors (6) and (7), in addition to the DC power supply + B and the power supply voltage.
It is possible by adjusting Vcc.

In addition, the present invention is not limited to the above-described embodiment, but may take various other configurations.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the dynamic focus voltage which rises sharply at both ends of each horizontal period is efficiently created with a simple structure, and there is an advantage that a dynamic focus voltage suitable for a large cathode ray tube can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a dynamic focus voltage generating circuit according to the present invention, and FIGS. 2, 3 and 4 are waveform diagrams for explaining the embodiment. (1) is a horizontal sync pulse input terminal, (3) is a field effect transistor, (4) is a transformer, (5) is a damper diode, (6) is a first capacitor, (7) is a second capacitor, 8) is a choke coil, and (11) is a dynamic focus voltage output terminal.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-168168 (JP, A) JP-A-2-306771 (JP, A) JP-A-63-74372 (JP, A) 152556 (JP, U) Japanese Utility Model 63-52351 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 3/26

Claims (1)

(57) [Claims] 1. A switching element, a diode, and a first
And a circuit in which a second capacitor is connected in series to a first terminal of a primary coil of a transformer, and a coil connected to a power supply at a second terminal of the primary coil of the transformer. A dynamic focus voltage generating circuit, which supplies a horizontal synchronization pulse to the switching element and obtains a dynamic focus voltage from a secondary coil of the transformer.