KR960014323B1 - Focus voltage control apparatus of tv - Google Patents

Abstract

The device includes a voltage detecting means(3) for detecting a level of voltage generated from flyback transformer(2), a switching operation means(4) for generating switching operation signal according to detecting result, a switching means(5) for transferring focus controlling voltage to CRT(7) or voltage controlling unit(6), a voltage controlling unit(6) for controlling focus controlling voltage, a display means(8) for display operating state, and a voltage control selecting means(7) for operating selectively a focus voltage controlling device selectively.

Description

Focus voltage regulator of television receiver

1 is a waveform diagram showing a focus voltage output from a flyback transformer of a television receiver.

2 is a block diagram showing a focus voltage adjusting device of a television receiver according to an embodiment of the present invention.

3 is a circuit diagram showing an actual circuit configuration of the apparatus shown in FIG.

* Explanation of symbols for main parts of the drawings

1: power drive unit 2: flyback transformer (FBT)

3: potential detector 4: switching driver

5: switching part 6: voltage adjusting part

7: CRT 8: Display

9: voltage adjustment selector.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for adjusting the focus of an image reproduced on a CRT (Cathode Ray Tube) of a television receiver, and more particularly to an apparatus for adjusting the focus voltage of a television receiver for adjusting an abnormal focus voltage caused by overload. .

In general, in a television receiver, a high voltage of 5 to 7 KV is applied to a focusing grid provided inside the CRT so that electrons emitted from the cathode of the CRT are connected to the fluorescent film of the CRT.

The high voltage to be applied to the focusing grid is generated by a flyback transformer (hereinafter referred to as FBT) according to a pulse signal applied from a power driver.

However, if the FBT becomes overloaded due to a long time of turning on the television receiver, the distribution capacity and leakage inductance of the high voltage winding in the FBT are changed, and as shown in FIG. 1, the high voltage sometimes reaches 10 KV. The pulse voltage is generated. When such a pulse voltage is applied to the connection chart of the CRT, the electron focusing action by the focusing grid is caused, resulting in poor focus on the CRT screen.

Accordingly, the present invention has been made in view of the above circumstances, and in the case where an abnormal high-pressure focus adjustment voltage is generated from the FBT due to an overload condition, a television receiver capable of applying a focus voltage of a constant potential to the focusing and CRT of the CRT is provided. It is an object to provide a focus voltage adjusting device.

A focus voltage adjusting device of a television receiver according to the present invention for realizing the above object comprises a potential detecting means for detecting a level of a focus adjusting voltage output from an FBT, and a switching drive signal in accordance with a detection result by the potential detecting means. A switching driving means for applying a focus adjusting voltage output from the FBT to the CRT or a voltage adjusting means in accordance with a driving signal from the switching driving means, and a focus adjusting voltage applied by the switching means at a constant potential. It is comprised including the voltage regulation means to adjust.

According to the present invention having the above-described configuration, the switching driving means determines whether the focus adjustment voltage is excessive based on the level signal detected by the potential detecting means, outputs the switching driving signal in the case of being excessive, The switching is performed in accordance with the drive signal from the switching driving means to apply the focus adjusting voltage output from the FBT to the voltage adjusting means. Then, the voltage adjusting means adjusts the focus adjusting voltage applied from the switching means to a potential of a constant level to apply the focusing grid of the CRT. Therefore, according to the above configuration, even when the level of the focus adjustment voltage output from the FBT becomes excessive, the focusing voltage of the focusing voltage and the constant potential of the CRT can be applied.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

2 is a block diagram showing a focus voltage adjusting device of a television receiver according to an embodiment of the present invention. In FIG. 2, reference numeral 2 denotes a high voltage for focus adjustment of 5 to 7 KV according to a pulse signal applied from a power supply drive 10. 3 is a potential detector for detecting the level of the focus adjustment voltage output from the FBT, 4 is a switching driver for generating a switching drive signal in accordance with the detection result by the potential detector 30; 5 is a switching unit for switching the focus adjustment voltage output from the FBT 2 according to the drive signal from the switching driver 40 and applying it directly to the CRT 7 or to the voltage adjusting unit 6. It is a voltage adjusting section for adjusting the focus adjusting voltage applied through the switching section 5 to a predetermined level.

In the drawing, reference numeral 8 is a display unit for indicating that the present focus voltage adjusting device is in an operating state, and 9 is for the viewer to operate the focus voltage adjusting device of the present invention according to the state of the heat on the screen of the CRT 7. As the voltage adjustment selection section, these display sections 8 and the voltage adjustment selection section 9 can be employed as necessary.

Next, the operation of the focus voltage adjusting device having the above configuration will be described using the actual circuit configuration shown in FIG.

In FIG. 3, the potential detector 3 is composed of a voltage divider circuit of the resistors R1 and R2, wherein the resistance values of the resistors R1 and R2 are output from the FBT 2 in the waveform diagram shown in FIG. The transistor Q1 of the switching driver 4 is set to be on when the focus adjustment voltage exceeds, for example, about 7.5KV. In the potential detecting section 3, the voltage dividing circuit formed by the resistors R1 and R2 is simple for simplicity of explanation and has a configuration in which a plurality of resistors are actually connected in parallel.

The switching driver 4 further includes a transistor Q1 whose ON and OFF are controlled in accordance with the base voltage set by the potential detector 3, and the emitter side potential and the resistors R8 and R7 of the transistor Q1. The comparator CP1 outputs a high level voltage when the emitter side potential of the transistor Q1 is greater than the reference voltage by comparing the reference voltage set by the comparator, where the comparator CP1 is an emitter side of the transistor Q1. It functions as a voltage regulator for reliably driving the transistor Q2 of the switching section 5 connected to the rear end by the potential.

In addition, the switching unit 5 is for switching the operation of the voltage adjusting unit 6 composed of the resistors R12 and R11 and the zener diode ZD1, that is, the high level from the comparator CP1 of the switching unit 5. When the voltage of is outputted, the transistor Q2 is turned on to form a current path from the FBT 2 to the ground through the resistor R12, the zener diode ZD1 and the resistor R10 to the CRT (7). Is maintained at a constant voltage set by the voltage adjusting section 6, and when the low level voltage is output from the comparator CP1, the transistor Q2 is turned off and the zener diode ZD1 is not operated so that the FBT 2 The focus adjustment voltage from is applied directly to the CRT 7.

The voltage adjustment selector 9 is composed of a switch SW1 for opening and closing the power supply Vcc supplied to the collector side of the transistor Q1 in the switching driver 4, and the display unit 8 is a switching driver. It consists of a light emitting diode LED1 whose on and off are controlled according to the signal output from the comparator CP1 of (4).

Next, the operation of the focus front bar adjusting device having the above-described configuration will be described in more detail.

First, when an excessive focus adjustment voltage is output from the FBT 2 while the switch SW1 is turned on, as described above, the split resistors R1 and R2 of the voltage detector 3 cause the trapping of the switching driver 4 to occur. The generator Q1 is turned on and a high level driving signal is output from the comparator CP1. Accordingly, the light emitting diode LED1 constituting the display unit 8 is turned on and the transistor Q2 of the switching unit 5 is turned on. Accordingly, a current path from the FBT 2 to the ground through the resistor R12, the zener diode ZD1, and the resistor R10 is formed, so that the focus adjustment voltage supplied to the focus grid of the CRT 7 is transferred to the resistor R12. ) And the appropriate level set by the zener diode ZD1 and the resistor R10.

On the other hand, when the switch SW1 constituting the voltage adjustment selector 9 is turned off or an appropriate focus adjustment voltage is output from the FBT 2, the transistor Q1 of the switching driver 4 is turned off and the light emitting diode LED1 is turned off. ) And transistor Q2 are also turned off. In this case, therefore, the zener diode ZD1 of the voltage adjusting section 6 is in an inoperative state, and the focus adjusting voltage from the FBT 2 is applied directly to the focusing grid of the CRT 7.

Therefore, according to the above embodiment, the focus adjustment voltage applied to the CRT 7 can be kept constant at all times.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

As described above, according to the present invention, even when an abnormal high-pressure focus adjustment voltage is generated from the flyback transformer of a television receiver due to an overload condition, a television receiver capable of applying a focus voltage of a constant potential to the focusing grid of the CRT The focus voltage adjusting device can be realized.

Claims (3)

A potential detecting means 3 for detecting the level of the focus adjustment yaw voltage output from the flyback transformer 2, and a switching driving means 4 for generating a switching drive signal in accordance with the detection result by the previous detection means 3; Switching means (5) for applying a focus adjustment voltage output from the flyback transistor (2) to the CRT (7) or the voltage adjuster (6) in accordance with the drive signal from the switch-operation means (4); And a voltage adjusting means (6) for adjusting the focus adjusting voltage applied through the switching means (5) to a predetermined level. 2. The focus voltage adjusting device of a television receiver according to claim 1, further comprising display means (8) for indicating that the focus voltage adjusting device is in an operating state. The focus voltage adjusting device of a television receiver according to claim 1 or 2, further comprising voltage adjusting selecting means (9) for the viewer to selectively operate the focus voltage adjusting device.