JPS599475Y2 - Horizontal deflection output switching device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a horizontal deflection output switching device, and in particular, when switching the magnitude of the horizontal deflection current in the horizontal deflection output circuit of a television receiver, for example, it is extremely easy and It is an object of the present invention to provide a horizontal deflection output switching device configured to perform reliable switching control.

Conventionally, in monitors using the picture tube of television receivers, underscan, which displays the image screen smaller than the picture tube surface, just scan, which displays the same size as the picture tube surface, and furthermore, the video screen There has been a demand for the use of various switching operations for the deflection state, such as in overscan where the deflection of the image plane is performed beyond the plane of the picture tube.

On the other hand, in a monitor that receives television signals of different standard formats, if the switching operation of the deflection output circuit as described above is not performed, depending on the signal format being received, the horizontal deflection frequency may be high. Since the amplitude of the horizontal deflection output wave of the image decreases as the image changes, if it is attempted to maintain it at a constant value, the horizontal deflection output must be switched.

FIG. 1 shows an example of a conventional horizontal deflection output switching circuit. In the figure, 1 is a horizontal deflection output transistor, which is turned on and off at the horizontal deflection period by a drive pulse P from a previous stage (not shown). Operate by repeating the state.

2 is a damper diode, 3 is a retrace resonant capacitor, 4
5 is a horizontal deflection coil, 5 is an S-shaped correction capacitor, 6 is a horizontal output transformer, and 7 is a changeover switch.

Now, when the movable terminal of the changeover switch 7 is connected to the terminal 7a and the DC power supply voltage +EB is applied to one terminal A of the horizontal output transformer 6, the horizontal deflection coil A sawtooth wave current 5 flows through 4.

The peak value of this current Is is expressed as follows, where the scanning time is T5 and the inductance of the deflection coil 4 is Ly.

Therefore, in order to change the amplitude of the horizontally deflected output wave,
It is sufficient to change the power supply voltage EB or the inductance Ly. For example, the smaller the inductance Ly, the larger the current 5 becomes, that is, the amplitude of the horizontally deflected output wave increases.

Here, in order to substantially change the value of the inductance Ly, it is sufficient to use the transformer 6 as an impedance converter. For example, if the total number of turns of the transformer 6 is n8, the transformer 6 from one terminal A to the terminal 7b If the number of turns of the transformer 6 up to the terminal 7C is nb, and the number of turns of the transformer 6 up to the terminal 7C is nc, then when the changeover switch 7 is connected to the terminal 7b, the inductance L of the deflection coil 4 seen from the other terminal B side of the transformer 6 is ′, it decreases to .

Furthermore, when the changeover switch 7 is switched to the terminal 7C, the inductance L''9 of the deflection coil 4 is further reduced to .

In this way, as one terminal of the deflection coil 4 is switched and connected to the tap terminal of the transformer 6 closer to the power supply side using the changeover switch 7, the apparent inductance of the deflection coil 4 decreases. Therefore, as is clear from equation (1) above, since the current Is is increased, the amplitude of the horizontally deflected output wave can be changed by switching and connecting the changeover switch 7.

In addition, when receiving signals of systems in which the scanning time of the horizontally deflected output wave is different, the inductance L
When the value of y is constant, as the scanning time T5 becomes smaller, the current 5 also becomes smaller and the amplitude of the horizontal deflection output wave is reduced. If we substantially change the value of Ly,
It is possible to maintain the amplitude of the horizontally deflected output wave substantially constant even if the scanning time T5 changes.

However, in the horizontal deflection output switching circuit shown in FIG. 1, the switching contacts of the movable terminals of the changeover switch 7 must handle considerably large currents and high voltages, which causes the disadvantage that the contacts are easily damaged and lack reliability. For this reason, it may be possible to use a semiconductor switch such as a transistor as a substitute for the changeover switch 7 to make it easier to control by remote control or microprocessor, but as mentioned above, large current and high voltage The use of semiconductor switches that are sufficiently resistant to high temperatures has the disadvantage that it is extremely difficult under the present circumstances.

The present invention is an improvement of the conventional horizontal deflection output switching circuit in order to eliminate the above-mentioned drawbacks from the above points of view, and an embodiment of the present invention shown in FIG. 2 will be described.

In FIG. 2, reference numerals 1 to 5 indicate the same operations as those having the same reference numerals as in FIG.

In the figure, the horizontal output transformer 6 has two windings, a first winding 6a and a second winding 6b, one terminal of the second winding 6b is connected to the emitter of the transistor 1, and the other terminal is connected to the first winding for boosting.
It is grounded through a series circuit of diode 8 and changeover switch 11.

Further, a connection point between the emitter of the transistor 1 and one terminal of the second winding 6b is grounded through a parallel circuit of a second diode 9 and a bypass capacitor 10.

Now, when the changeover switch 11 is in the cutoff state, the current of the transistor 1 flows through the second diode 9 and the bypass capacitor 10, and there is almost no difference from normal deflection operation, and a sawtooth wave current flows through the deflection coil 4. do.

Next, to explain the case where the changeover switch 11 becomes conductive, let us assume that the number of turns of the first winding 6a of the transformer 6 is n1, the number of turns of the second winding 6b is n2, and the first
The terminal voltage of the winding wire 6a is E.

Close the terminal voltage of capacitor 10 to E.

If we virtually ignore the voltage drops across the diodes 8 and 9 and the transistor 1 during closing and conduction, the second winding 6b
The terminal voltage of is determined by the turns ratio of the transformer 6, and this terminal voltage becomes the terminal voltage E when the first diode 8 is conductive.

On the other hand, assuming that the voltage drop of transistor 1 can be ignored, the power supply voltage EB is equal to the voltage E.

and E. The sum is the voltage E.

Since is a reverse voltage, the following equations (4) and (5)
If we transform each equation, we get (4') (5
') Voltage E from both equations.

When you delete Therefore, the voltage is E.

A negative voltage determined by the number of turns of the first and second windings 6 a and 6 b is generated, the second diode 9 is cut off, and a power supply voltage of voltage E B +E c is applied to the transistor 1. is equivalent to

Therefore, it is easy to understand that the value of the power supply voltage E8 is switched to the power supply voltage EB + EC according to the above equation (1), and that the amplitude of the current IS, that is, the horizontal deflection output wave, is switched by opening and closing the changeover switch 11. Ru.

The circuit described above is a modified circuit of the so-called series boost circuit, but in the present invention, the presence or absence of series boost operation is switched by a changeover switch 11, which is a single-pole, single-throw switch with one terminal grounded. Characteristics exist wherever you are.

That is, since the changeover contact of the changeover switch 11 is located at a low potential point and is not a transfer contact, there is an advantage that the changeover switch can be extremely easily replaced with a semiconductor switch using a transistor or the like.

FIG. 3 shows another embodiment of the present invention in which the circuit shown in FIG. 2 is further developed, in which a tap terminal T1 is newly provided in the second winding 6b of the transformer 6 shown in FIG.
1 is connected to a series circuit of a boost diode 12 and a transistor switch 13. Here, the changeover switch 11 shown in FIG. 2 is shown as a transistor switch.

Now, when each transistor switch 11, 13 is in a cut-off state, the second diode 9 is conductive as described above, and the actual power supply voltage is maintained at EB.

Next, when only the transistor switch 13 becomes conductive,
Similarly to the circuit shown in FIG. 2, the actual power supply voltage E'B is determined by assuming that the number of turns from the emitter side of the transistor 1 to the tap terminal T1 of the second winding 6b is n/2, and the capacitor at this time is n/2. If the terminal voltage of 10 is E'C, it will be higher than the power supply voltage EB based on the same principle as described above.

Next, when the transistor switch 11 is conductive and the transistor switch 13 is disconnected, if the terminal voltage of the capacitor 10 at this time is E''C, the actual power supply voltage E''8 is similarly, Depending on the combination of conducting and blocking states of each transistor switch 11 and 13, the actual power supply voltage is set to
E'8, E//. The amplitude of the horizontally deflected output wave can be adjusted by switching in three ways.

Furthermore, when both transistor switches 11 and 13 are conductive, the diode 12 becomes reverse biased and is cut off, so that current flows only through the first diode 8 and the transistor switch 11, reducing the actual power supply voltage. is also E'B as shown in equation (8) above.

In the circuit shown in FIG. 3, each transistor switch 11.
13 has been described using a transistor switch that converts the state into either a conductive state or a cut-off state by the base input, but of course, this can be used in place of a normal switch.

Furthermore, in the circuit shown in FIG. 3, by adding a tap terminal T2 indicated by a dotted line on the second winding 6b and connecting the series circuit of the diode and switch described above to this terminal, various kinds of substantial It is also possible to select the power supply voltage.

In this case, priority is given to the switch connected to the tap terminal on the winding of the second winding 6b that is farther away from the one terminal C when viewed from the one terminal C, and when a certain switch becomes conductive, the switch connected to the one terminal C is given priority. The state of the switch connected to the side tap terminal is irrelevant.

As explained above, according to the horizontal deflection output switching device of the present invention, it is possible to use a transistor switch such as a transistor as a changeover switch, and the simple circuit structure allows for extremely easy and reliable multi-purpose switching. Since it is possible to control the switching of different types of horizontal deflection outputs, it has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional circuit, FIG. 2 is a circuit diagram showing an embodiment of the circuit of the present invention, and FIG. 3 is a circuit diagram showing another embodiment. 1...Horizontal deflection output transistor, 4...
...Horizontal deflection coil, 6...Horizontal output transformer, 6 a, 6 b...First and second winding, 7
......Selector switch, 8...First diode, 9...Second diode, 10...
・Condenser, 11...Selector switch (transistor switch).

Claims (1)

[Scope of utility model registration request] One terminal of the power source is connected to one terminal of a horizontal deflection output element through the first winding of the transformer, the other terminal of the deflection output element is connected to one terminal of the second winding of the transformer, and the other terminal of the second winding is connected to one terminal of the horizontal deflection output element. Alternatively, the tap terminal on the second winding is connected to the other terminal of the power supply through a series circuit of the first diode and the voltage switching switch element, and the first diode connects to one terminal of the power supply when the voltage switching switch element is conductive. The polarity is such that a current flows through the first winding, the deflection output element, and the second winding to the other terminal of the power supply, and the other terminal of the deflection output element is connected to one terminal of the second winding of the transformer. The connection point is connected to the other terminal of the power supply through a parallel circuit of a second diode and a capacitor, and the second diode directs the deflection output element from the other terminal to the other terminal of the power supply when the voltage switching switch element is cut off. A horizontal deflection output switching device configured to have a polarity through which current flows.