JPH04326891A - Crt cut-off adjusting switching circuit - Google Patents

Abstract

PURPOSE:To turn a traditional mechanical switch into the switching circuit of electronic circuit configuration from the viewpoint of the improvement of operability and the improvement of reliability in respect of a CRT cut-off adjusting switching circuit to be used for the cut-off adjustment of a CRT in a color television receiver, etc., using a color cathode ray tube(CRT) consisting of three electron gunsd. CONSTITUTION:The title switching circuit is constituted of a first transistor TR1 to be turned on at the time of the adjustment and turned off normally, a second transistor TR2 to turn on/off the first transistor TR1 on the basis of a switching signal inputted to its base, a fourth transistor TR4 to be turned on normally and turned off at the time of the adjustment, a fifth transistor TR5 to be turned off normally and turned on at the time of the adjustment, and a third transistor TR3 to turn on/off the fourth transistor TR4 and the fifth transistor TR5 on the basis of the switching signal inputted to its base.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a color television receiver, etc. that uses a color cathode ray tube (CRT) consisting of three electron guns of red, blue, and green. This invention relates to a switching circuit for cutoff adjustment.

0002

2. Description of the Related Art An embodiment of a conventional CRT cutoff adjustment switching circuit is shown in FIG. The purpose and operation of the CRT cutoff adjustment switching circuit will be explained below with reference to FIG. In the figure, 11 is a CRT cutoff adjustment switch (hereinafter referred to as a switch), 12 is a vertical oscillation circuit, and 1
3 is a vertical output circuit, 14 is a video signal processing circuit (including an automatic white balance circuit), and 15 is transistors TR11 to T.
A green video output circuit consisting of R13, etc., 16 and 17 a red video output circuit and a blue video output circuit having the same configuration as the green video output circuit 15, and 18 a color cathode ray tube (CRT) consisting of three red, blue, and green electron guns. , R11 to R16 are resistors, DY is a vertical deflection yoke, C11 is a capacitor, D11
is a Zener diode, and V11 to V13 are different DC power supplies. Note that specific circuit diagrams of the red video output circuit 16 and the blue video output circuit 17 are omitted for the above reasons.

[0003] CRT cutoff adjustment (hereinafter referred to as adjustment) is an adjustment to align the cutoff points of each of the electron guns mentioned above to the same point, but during this adjustment, vertical deflection is stopped and the video signal is cut off. CRT cathode (KR,
It is necessary to apply a constant DC voltage to KG, KB). The switch 11 is provided for making such adjustments, and as shown in the figure, a switch (hereinafter referred to as a first switch) that switches b to a movable end and a or c to a fixed end;
It is composed of a switch (hereinafter referred to as a second switch) that switches between e as a movable end and d or f as a fixed end (hereinafter referred to as a second switch), and both are switched in conjunction with each other. The first switch is normally set to the c side,
When set to the a side (during adjustment), vertical deflection stops. Further, the second switch is normally set to the f side, and when set to the d side (during adjustment), the video signal to each cathode of the CRT is cut off and a constant DC voltage is applied to each cathode. The vertical deflection stop in FIG.
This is achieved by stopping the vertical oscillation by grounding the feedback circuit to the vertical oscillation circuit 12 via 11 and R12 etc. via the first switch b-a. Since the vertical deflection can be stopped by reducing the sawtooth deflection current flowing through the deflection yoke DY to zero, a method of stopping oscillation other than using the feedback circuit described above may be used. Next, the video circuit side will be explained. After the vertical pulse generated in the vertical output circuit 13 is DC-cut by C11, it is adjusted to an appropriate amplitude by R13 and D11 and is used as a blanking pulse. Normally, the blanking pulse is supplied to the video processing circuit 14 via the second switch fe, so the video processing circuit 14 sends a normal video signal to the green video output circuit (TR11 etc.) 15. supply Therefore, each cathode (KR, KG, KB) of CRT18
is being driven normally. The video processing circuit 14 in this example is a circuit including an automatic white balance circuit, and is a circuit in which inputting a blanking pulse is a prerequisite for normal operation. Therefore, when e of the second switch is switched to the d side, the blanking pulse is no longer input to the video processing circuit 14, and instead the DC voltage V
11 is input. As a result, the video signal is no longer output, and since the relationship of V14<V13 holds, TR11 is cut off and a constant DC voltage from V12 is applied to the cathode KG. A constant DC voltage is similarly applied to the other cathodes KR and KB. The above is the adjustment state, and the following is the adjustment work.

0004

[Problems to be Solved by the Invention] As mentioned above, the conventional C
RT cutoff adjustment was handled by providing a switch 11 (FIG. 3) on the chassis near the vertical deflection circuit or the video circuit. Considering that the switch is frequently used during factory manufacturing or repair work in the market, it is necessary to provide it at a position that is as easy to operate as possible. However, as a result of prioritizing ensuring basic performance, there are cases where the switch has to be located deep inside the chassis. In such a case, the operability as a switch that requires direct manual operation becomes extremely poor. Additionally, since the switch is a mechanical switch, there are reliability problems such as poor contact. In view of the above-mentioned drawbacks, the present invention provides a C switch that uses an electronic circuit configuration that allows indirect switching, rather than a mechanical switch that requires a direct manual switching operation.
An object of the present invention is to provide a switching circuit for adjusting RT cutoff.

[0005]

[Means for Solving the Problems] The present invention connects the collector to a corresponding point on the vertical circuit where vertical deflection is stopped by grounding, grounds the emitter, and connects the base to the first resistor through the first resistor. a first transistor connected to a power supply of the first transistor, a second transistor whose collector is connected to the base of the first transistor, whose emitter is grounded, and whose base is supplied with a switching signal; connected to the first power supply via a series circuit consisting of a resistor of 3,
A third transistor whose emitter is grounded and whose base is supplied with the switching signal, and the collector is connected to each corresponding part of the video circuit so that when the collector and emitter are conductive, the video signal is supplied to the CRT, and when the collector and emitter are not conductive, the video signal is not supplied. a fourth transistor having a base connected to the intersection of the second resistor and the third resistor; a collector connected to the collector of the fourth transistor; and a fourth transistor having a collector connected to the collector of the fourth transistor; The present invention provides a switching circuit for adjusting CRT cutoff, which is connected to a power source of the fifth transistor, and a fifth transistor whose base is supplied with the switching signal.

[0006]

[Operation] The switching part of the mechanical switch is replaced with a transistor switching circuit, and the switching of the transistor switching circuit is controlled by a switching signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A CRT cutoff adjustment switching circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an embodiment of a CRT cutoff adjustment switching circuit according to the present invention. In the figure, 1 is a switching signal line, 2 is a switching signal line,
is a switching circuit, TR1 to TR5 are first to fifth transistors, R1 to R6 are first to sixth resistors, V1 is a first power supply, V2 is a second power supply, and D1 is a Zener diode. Components that are the same as those in FIG. 3 are given the same reference numerals.

Next, the configuration of the present invention will be explained in comparison with FIG. 3. The part surrounded by the dotted line in Figure 1 (code 2) is Figure 3.
The switch 11 is equivalent to the switch 11 shown in FIG. The constituent parts of TR1 and TR2 are the first switch of the switch 11,
The part made up of TR3 to TR5 is the second part of switch 11.
corresponds to each switch. The symbols a to f and 31 to 34 in FIG. 1 and the same symbols in FIG. 3 indicate the same circuit parts. Next, the operation of the present invention will be explained. The switching signal is normally at a high level (DC voltage of approximately 5V, hereinafter referred to as "H").
It is a signal that becomes a low level (approximately 0V, hereinafter referred to as "L") during adjustment. On the vertical deflection side, under normal conditions, the base of TR2 is H, so it is in the on state, the collector voltage (=TR1 base voltage) is low, and TR1
is off. In other words, if represented by the switch 11, b is switched to side c. Now, when the switching signal is set to L for adjustment, TR2 is turned off, the collector voltage of TR2 becomes high, and TR1 is turned on. That is, b is grounded (a) and vertical deflection is stopped as explained in FIG. On the video side, under normal conditions, TR3 is on as described above, and since the collector voltage of TR3 is low, the base voltage of TR4 is also low and TR4 is in the on state. On the other hand, TR5
is in an off state because the base is H. In other words, if represented by the switch 11, e is switched to the f side. During adjustment, when the switching signal becomes L, T
Both R3 and TR4 are turned off. Since the base of TR5 goes down, it turns on. As a result, e has been switched from the f side to the d side. Since the above switching control uses a common switching signal, it is performed simultaneously on the vertical side and the video side.

As explained above, the function of this switching circuit is to operate normally under normal conditions, and to stop the vertical deflection (zero sawtooth current in the deflection yoke) and to send video signals to each cathode of the CRT during adjustment. This is to cut off the voltage and supply a constant DC voltage. Therefore, the present invention can be used in a manner that satisfies such conditions, and the connection method of this switching circuit to the vertical circuit and the video circuit is free as long as the conditions for basic operation of the transistor (for example, power supply) are satisfied. be. Incidentally, the purpose and overall operation of this switching circuit are as explained in FIG. 3, so a description thereof will be omitted. Next, an example of obtaining the above switching signal will be explained with reference to FIG. FIG. 2 shows an example of a method for obtaining the switching signal by remote control operation. The light receiving section 4 receives the optical signal corresponding to the above-mentioned H or L that is emitted every time the remote control 3 is switched, converts it into an electrical signal, and inputs the electrical signal to the microcomputer 5. The microcomputer 5 changes its output to the above-mentioned H or L in response to the electrical signal. A major feature of the present invention is that it can be switched by remote control operation in this way.

0010

As explained above, according to the present invention, the switching circuit provided for stopping the vertical deflection and cutting off the video signal when adjusting the cutoff of the color cathode ray tube is constructed with an electronic circuit, which eliminates the conventional manual operation. The direct switching type mechanical switch has been replaced with an indirect switching type operated by remote control, improving operability and reliability, and greatly contributing to improving the productivity and functionality of color television receivers that require cutoff adjustment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a main part of an embodiment of a CRT cutoff adjustment switching circuit according to the present invention.

FIG. 2 is a block diagram of main parts showing a process of generating a switching signal by remote control operation.

FIG. 3 is a circuit diagram of a main part of an embodiment of a conventional CRT cutoff adjustment switching circuit.

[Explanation of symbols]

1 Switching signal line 2 Switching circuit 3 Remote control 4 Light receiving unit 5 Microcomputer 11 CRT cutoff adjustment switch 12
Vertical oscillation circuit 13 Vertical output circuit 14 Video signal processing circuit 15 Green video output circuit 16 Red video output circuit 17 Blue video output circuit 18 Color cathode ray tube (CRT) TR1 First transistor TR2 Second transistor TR3 Third transistor TR4 4 transistor TR5 5th transistor R1 1st resistor R2 2nd resistor R3 3rd resistor R4 4th resistor R5 5th resistor R6 6th resistor V1 1st power supply V2 2nd power supply V11 DC Power supply V12 DC power supply V13 DC power supply DY Vertical deflection yoke

Claims (5)

[Claims] [Claim 1] A first circuit whose collector is connected to a corresponding point on a vertical circuit where vertical deflection is stopped by grounding, whose emitter is grounded, and whose base is connected to a first power supply via a first resistor. a transistor, a collector connected to the base of the first transistor and an emitter grounded;
A second transistor whose base is supplied with a switching signal, whose collector is connected to the first power supply via a series circuit consisting of a second resistor and a third resistor, whose emitter is grounded, and whose base is supplied with the switching signal. A third transistor that supplied the signal, and the collector and emitter are respectively connected to corresponding locations of the video circuit so that when the collector and emitter are conductive, the video signal is supplied to the CRT, and when the collector and emitter are not conductive, the video signal is not supplied; a fourth transistor having a base connected to the intersection of the second resistor and the third resistor, a collector connected to the collector of the fourth transistor, an emitter connected to the second power supply, and a base connected to the fourth transistor; 1. A switching circuit for adjusting CRT cutoff, comprising: a fifth transistor that supplies a switching signal. 2. The CRT cutoff adjustment switching circuit according to claim 1, wherein the collector of the first transistor is connected to a feedback circuit from the vertical output circuit to the vertical oscillation circuit. 3. The CRT cutoff adjustment switching circuit according to claim 1, wherein the collector of the first transistor is connected to an output terminal of a vertical oscillation circuit. 4. The CRT cutter according to claim 1, wherein a vertical blanking pulse is supplied to the emitter of the fourth transistor, and a collector is connected to the vertical blanking pulse input terminal of an automatic white balance circuit. Switching circuit for off adjustment. 5. The CRT cutoff adjustment switch according to claim 1, wherein the emitter of the fourth transistor is connected to an output end of a video drive circuit, and the collector is connected to an input end of a video output circuit. circuit.