JP2521055B2 - Horizontal deflection circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a horizontal deflection circuit in an image reproducing apparatus configured to operate at a plurality of horizontal deflection frequencies (horizontal scanning periods).

(Prior Art) As an image reproducing apparatus adapted to reproduce an image by using a cathode ray tube (a picture tube), a display apparatus or the like which has been conventionally used in a television receiver or other various information equipments is used. An example can be given.

In order to reproduce an image on the picture tube in the image reproducing apparatus as described above, it is necessary to deflect the electron beam of the picture tube in the vertical and horizontal directions according to a predetermined scanning standard, as is well known.

By the way, the scanning standard to be applied upon reproduction of an image, for example, in the case of a television receiver, often differs depending on the standard system of the television system that is the object of image reception, and, Regarding the display devices used in various information devices, the scanning standards are often different to the extent that it can be said that the scanning standards are arbitrarily set for each manufacturer of each device.

When the scanning standards are different from each other as described above, the configuration of the deflection circuit is naturally different. However, as described above, the image reproducing devices having different configurations are configured for the different scanning standards. It is well known that many deflection circuits that can be used for multiple scanning standards have been proposed since various types of small-quantity production are disadvantageous in terms of production control and cost. Is.

FIG. 4 is a block diagram showing an example of the overall configuration of a horizontal deflection circuit that is capable of horizontally deflecting an electron beam of a picture tube at a horizontal scanning cycle according to a plurality of scanning standards. In FIG. 4, reference numeral 1 is a phase comparator for phase-comparing the pulse P of the horizontal scanning period supplied from the preceding stage (not shown) and the pulse Vo supplied from the output unit. By controlling the horizontal oscillation stage 2 of the next stage by the output voltage Vφ, the horizontal oscillation stage 2 outputs an output square wave Vosc having a horizontal scanning period th, for example, as shown in FIG. To be done.

The output square wave Vosc of the horizontal oscillation stage 2 is supplied to the horizontal drive transistor 3 of the excitation stage via the base input resistor 4.
Supplied to the base. The emitter of the horizontal drive transistor 3 is grounded, and the collector of the horizontal drive transistor 3 is connected to the power source + via the primary winding 5a of the drive transformer 5.
Connected to Eb.

One end of the secondary winding 5b of the drive transformer 5 is grounded, and the non-grounded end is connected to the base of the horizontal output transistor 6, and the horizontal output transistor 6 is connected to the horizontal drive transistor 5b. The excitation wave Vcd generated in the collector circuit of the transistor 3 is supplied through the drive transformer 5 to perform switching operation together with the damper diode 7 as is well known, and the horizontal deflection coil 9 is sawtooth-shaped with a horizontal scanning period th. The waves also carry an electric current to horizontally deflect the electron beam of the picture tube.

In addition, 8 is a retrace resonance capacitor, 10 is an S-shaped correction capacitor, 11 is a flyback transformer, 11a is a primary winding of the flyback transformer 11, 11b is a secondary winding of the flyback transformer 11, 11c is a flyback transformer 1
It is the third winding of 1.

The primary winding of the flyback transformer 11 described above
A DC power supply + Eb for operating the horizontal deflection circuit is connected to 11a via a voltage control circuit (regulator) 13, and the voltage control circuit (regulator) 13 is connected to one end of the primary winding 11a of the flyback transformer 11. Output voltage + Eb 'of the flyback transformer 11, the secondary winding 11b of the flyback transformer 11 boosts the flyback pulse Vc generated at the collector of the horizontal output transistor 6 to generate a high voltage pulse Vhv, which is received by the picture tube. The DC high voltage generating circuit (high voltage rectifying circuit for generating the anode voltage of the picture tube) 12 for generating the anode voltage is supplied to generate a DC high voltage EHT and supply it to the anode of the picture tube.

Also, the tertiary winding 11 of the flyback transformer 11 described above.
The output pulse Vo generated at c is supplied to the phase comparator 1 as a comparison signal as described above, and the horizontal deflection circuit shown in FIG. 4 has a phase comparator 1 → horizontal oscillation stage 2 → excitation stage → horizontal deflection. A well-known automatic frequency control system is constituted by a closed loop of the output stage → phase comparator 1 →.

Reference numeral 14 is a frequency / voltage conversion circuit. The frequency / voltage conversion circuit 14 supplies an output voltage Vf corresponding to the frequency of a signal input thereto to the horizontal oscillation stage 2 and
Then, the free-running frequency of the frequency-voltage conversion circuit 14 is changed based on the output voltage Vf of the frequency-voltage conversion circuit 14, and the repetition period of the pulse P of the horizontal scanning period th supplied to the phase comparator 1 is repeated. Allows the output square wave Vosc to oscillate.

Further, the voltage control circuit 13 is illustrated so that the horizontal deflection current Iy of a constant magnitude flows in the horizontal deflection coil 9 even if the horizontal deflection circuits operate at different horizontal scanning periods. It is configured to have a function of changing the voltage value of the output voltage + Eb ′ supplied as the operating voltage of the horizontal deflection circuit from the control voltage generated by the circuit arrangement which is not provided. . As the control voltage to be supplied to the voltage control circuit 13, for example, a voltage obtained by rectifying the output pulse Vo generated in the tertiary winding 11c of the flyback transformer 11 and a reference voltage are used as a comparator. By giving, the voltage output from the comparator can be used.

The operation of the horizontal deflection circuit shown in FIG. 4 will be described below with reference to the signal waveform charts of the respective portions shown in FIG. An output square wave Vosc output from the horizontal oscillation stage 2 as shown in FIG.
Causes the drive transistor 3 of the drive stage to conduct by its positive part, thereby
Since the collector potential of the drive transistor 3 is set to substantially zero potential while the drive transistor 3 is conducting, the collector voltage waveform Vcd (excitation wave Vcd) of the drive transistor 3 is
The output wave from the horizontal oscillating stage 2 is a square wave having a phase substantially opposite to that of the output square wave Vosc, but the conduction period ton of the excitation wave Vcd is as shown in FIG. 5 (b). It is longer by the amount corresponding to the storage time ts1 in the drive transistor 3.

A base current Ib as shown in FIG. 5 (c) flows through the horizontal output transistor 6 to which the excitation wave Vcd is supplied to the base via the drive transformer 5, but the excitation wave Vcd falls. Base current I from the part
b turns to the negative direction, and the negative base current flows until the excess carriers in the base layer of the horizontal output transistor 6 are swept away. Ts2 in FIG. 5 (c) indicates the accumulation time during which the negative base current Ib flows through the horizontal output transistor 6 described above.

At the end of the above-mentioned accumulation time ts2, the collector current Ic of the horizontal output transistor 6 becomes zero as shown in (e) of FIG. A half-wave pulse Vc having a sine wave as shown in FIG.

From the time T1 at the end of the pulse Vc, the damper current Id as shown by the dotted line in FIG. 5 (e) begins to flow out, and then at time To, the horizontal output transistor 6
The collector current Ic that started to flow in response to the start of the base current Ib of
The continuous flow to Id forms a current waveform that linearly increases over the entire horizontal scanning period.

Due to the collector current Ic and the damper current Id of the horizontal output transistor 6 and the charging / discharging flow of the retrace resonance resonator 8, a current Iy as shown in FIG. 5 (f) is applied to the horizontal deflection coil 9. As a result, the electron beam in the picture tube is horizontally deflected.

(Problems to be Solved by the Invention) Now, in the operation of the horizontal deflection circuit described with reference to the waveform diagram shown in FIG. 5, the base current Ib in the positive direction flows to the base of the horizontal output transistor 6. For the first time, the time T1 at which the collector current Ic thereof starts to flow is the time T1 at which the pulse Vc generated in the collector of the horizontal output transistor 6 ends.
And a time point T2 approximately at the center of the horizontal scanning period. However, as shown in FIG. 6, for example, as shown in FIG. If the time To when the current Ib starts to flow and the collector current Ic of the horizontal output transistor 6 starts to flow is before the time T1 at which the pulse Vc generated in the collector of the horizontal output transistor 6 ends, the above-mentioned pulse Since the collector current Ic flows when Vc is present, an extremely large loss occurs in the horizontal output transistor 6 at that portion, and the reliability of the horizontal output transistor is significantly impaired. For example, as shown in FIG. 7, the time point To when the collector current Ic of the horizontal output transistor 6 starts to flow is at the time point T2 approximately at the center of the horizontal scanning period.
If it is positioned after the current, the collector current Ic does not flow out even if the damper current becomes zero, so that the horizontal deflection current is interrupted at that portion and a small pulse is applied to the collector of the horizontal output transistor 6 at that portion. Occurs, which causes a large loss in the horizontal output transistor 6, which is a problem.

Therefore, in the normal design of the horizontal deflection circuit, the positive direction base current Ib starts to flow to the base of the horizontal output transistor 6 and the collector current Ic thereof starts to flow so that the above-mentioned problem does not occur. The time point To was located between the time point T1 at which the pulse Vc generated in the collector of the horizontal output transistor 6 ends and the time point T2 at the approximate center of the horizontal scanning period, but according to a plurality of scanning standards. In the case of a horizontal deflection circuit capable of horizontally deflecting the electron beam of the picture tube in the horizontal scanning cycle, it is possible to realize a horizontal deflection circuit having a simple configuration that satisfies the above-mentioned conditions. It was difficult.

The above problems will be described in detail below with reference to the waveform diagrams of FIGS. 8 to 11 in which specific numerical values are entered. Fig. 8 shows the horizontal scanning period of 63.5 microseconds (horizontal deflection frequency
The signal waveform of each part of the horizontal deflection circuit when the horizontal deflection of the electron beam of the picture tube is performed at 15.75 KHz) is shown in FIG. 8 (a). The output square wave Vosc has a horizontal scanning period of 63.5 microseconds, and its pulse width tosc is about 1/3 of the horizontal scanning period, which is 21 microseconds.

FIG. 8 (b) shows the voltage waveform Vcd (excitation wave Vcd) of the collector of the drive transistor in the drive stage, and this figure shows that the storage time ts1 in the drive transistor is 4 microseconds.

Figure 8 (c) shows the base current of the horizontal output transistor.
Ib, and in this figure, the base current Ib turns in the negative direction from the falling portion of the excitation wave Vcd, and the accumulation time ts2 at which the negative base current flows until the excess carriers in the base layer of the horizontal output transistor are swept away is Shown as being 4 microseconds.

FIG. 8 (d) shows a pulse Vc generated in the collector of the horizontal output transistor, and its pulse width tr, that is,
The blanking period tr is shown as being 10 microseconds.
Therefore, the horizontal scanning period ts is 53.5 microseconds as shown in the figure.

FIG. 8 (e) shows the collector current Ic of the horizontal output transistor, and the waveform shown by the dotted line from time T1 to time To in this figure shows the damper current. Time T1 in the figure
From the time T2 to the time T3 is the horizontal scanning period ts.
At the time point indicated by, that is, the time point when the combined current of the damper current Id and the collector current of the horizontal output transistor changes from the negative direction to the positive direction, if there is no circuit loss, it is in the central portion of the horizontal scanning period ts. However, due to the circuit loss (including the loss due to the electric power supplied from the horizontal deflection circuit to the high voltage circuit via the flyback transformer 10), the central portion of the horizontal scanning period ts described above. Since the position of T2 on the time axis can take various values depending on the design, the horizontal scanning time ts is 4 to 6 as a typical example.
It is shown that T2 exists at the position of the front part divided by the ratio.

In the case where the time relationship between the waveforms of each part in the horizontal deflection circuit is as shown in FIG. 8, the period during which the damper current Id flows, that is, the time length td from time T1 to time To is 11
The time length tc ⁺ from time T2 to time T3 when the collector current Ic of the horizontal output transistor is flowing in the positive direction is 32.5 microseconds, and the collector current Ic of the horizontal output transistor is flowing in the negative direction. Time To Time
Time length until T2 tc ^- Since the 10 microseconds, in this case in the base of the horizontal output transistor begins the positive direction of the base current Ib flows, time To begin to flow it in the collector current Ic, the horizontal output transistor It is located in the central portion between the time T1 at which the pulse Vc generated in the collector ends and the time T2 approximately at the center of the horizontal scanning period, and there is no problem in the operation of the horizontal deflection circuit in this case. Absent.

Now, in the case of a horizontal deflection circuit in which the horizontal deflection current supplied to the horizontal deflection coil is of only one type of horizontal scanning period, a positive direction base current Ib begins to flow to the base of the horizontal output transistor, Is designed so that the time point To at which the collector current Ic starts to flow is between the time point T1 at which the pulse Vc generated at the collector of the horizontal output transistor 6 ends and the time point T2 approximately at the center of the horizontal scanning period. Is not as difficult as on the left.

However, in recent years, the picture tube is often used for the display device of the computer, and further, the horizontal deflection frequency of the display device of the computer is set to a frequency value of 15 KHz to 35 KHz or more. As many horizontal display circuits adopt different horizontal deflection frequencies, the demand for a horizontal deflection circuit which can be used for a plurality of scanning standards is increased, for example, as shown in FIG. As already described with reference to the above, using the output voltage Vf of the frequency / voltage conversion circuit 14, the repetition period of the free-running oscillation wave of the horizontal oscillation stage 2 is supplied to the phase comparator 1 in the horizontal scanning period th. The operation state of the horizontal oscillating stage 2 is changed so as to be in a state substantially corresponding to the repetition cycle of the pulse P of the The voltage control circuit 13 controls the horizontal deflection coil 9 so that the horizontal deflection current Iy flows through the horizontal deflection coil 9 even when operating in different horizontal scanning cycles.
There has also been proposed a horizontal deflection circuit that can operate in accordance with a plurality of scanning standards by, for example, changing the operating voltage of the horizontal deflection circuit.

By the way, the horizontal oscillation stage 2 used in the horizontal deflection circuit
Is usually composed of a multivibrator circuit or the like, and the pulse width tosc of the output square wave is often constant even if the cycle of the output square wave output therefrom changes.

Therefore, even if the repetition period (horizontal scanning period th) of the output square wave of the horizontal oscillation stage 2 changes as described above,
Assuming that the horizontal oscillating stage 2 having a structure in which the pulse width of the output square wave does not change is used, the output square wave Vosc from the horizontal oscillating stage 2 is 63.5 microseconds in the case of the above-mentioned eighth illustration. From the state of the repetition period, 1/2 of that
The cycle width of the output square wave Vosc from the horizontal oscillating stage 2 is 21 microseconds when it is changed to the state of the repetition cycle of 32 microseconds, that is, 21 microseconds. Assuming that the output is a square wave Vo from the horizontal oscillation stage 2 in this case,
sc becomes that shown by Vosc in FIG.

The flyback time tr may or may not be changed according to the change of the horizontal scanning period th for the convenience of the circuit design, but here, the horizontal deflection period th is changed to 1/2. Accordingly, if the retrace time tr, which was 10 microseconds in the case of FIG. 8, is changed to 5 microseconds, which is 1/2 the time length, the scanning period ts in this case is 27 When the ratio of the period of T1 → T2 and the period of T2 → T3 is set to 4 to 6, as described above, the time length of T1 → T2 becomes 12 microseconds.

However, the output square wave Vo from the horizontal oscillation stage 2 described above
The low level period of the excitation wave Vcd that appears on the collector side of the drive transistor of the excitation stage to which sc is supplied is 21 microseconds of the pulse width tosc of the output square wave Vosc from the horizontal oscillation stage 2 described above, and Since it is the sum of the accumulation time ts of 1/4 microsecond,
When the excitation wave Vcd rises, that is, with reference to FIG. 9, that is, the collector current of the horizontal output transistor
As is apparent from FIG. 9, the time point To at which Ic starts to flow is a position behind the time point T2 on the time axis.

In this way, when the horizontal scanning period th is changed from 63.5 microseconds to 32 microseconds, which is 1/2 of that, without changing the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2, If it is left as it is for 21 microseconds, the collector current Ic does not flow out even if the damper current becomes zero, as already described with reference to FIG. In addition to the interruption of the current, a small pulse is generated in the collector of the horizontal output transistor at that portion, which causes a large loss in the horizontal output transistor, thus impairing the reliability of the horizontal output transistor.

Therefore, this time, when the horizontal scanning period th is changed from 63.5 microseconds to 32 microseconds, which is 1/2 of that, the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2 is also 21 microseconds. Considering the case where the second is changed to half of that, 10.5 microseconds (however, the flyback time tr is 5 microseconds as in the case of FIG. 9). The relationship of the signal waveform on the time axis is as shown in Fig. 10. In the case of Fig. 10, the period during which the damper current Id flows, that is, from time T1 to time
Time length td of up To become 5.5 microseconds, also the time length from the time To the collector current Ic of the horizontal output transistor is flowing in the negative direction until the time T2 tc ^- 5.5 microsecond, the collector current Ic of the horizontal output transistor , The time length tc ⁺ from time T2 to time T3 is 12 microseconds, and in this case, the base current Ib in the positive direction begins to flow to the base of the horizontal output transistor and its collector current. The point To when Ic starts to flow is the point T1 when the pulse Vc generated in the collector of the horizontal output transistor ends,
It is located in the central portion between the time T2 and the center of the horizontal scanning period, and there is no problem in the operation of the horizontal deflection circuit in this case. Is flowing, that is, the time length td from time T1 to time To and the collector current Ic of the horizontal output transistor
Is flowing in the negative direction. Time length tc from time To to time T2
^- short and so each 5.5 microseconds and, since there is no margin for variations, it is necessary to set the pulse width tosc output square wave to be generated in a horizontal oscillating stage 2 correctly.

Next, this time, the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2 remains 10.5 microseconds which is 1/2 of 21 microseconds (however, the retrace time tr is the same as in the case of FIG. 8). Considering the case where the horizontal scanning period th is changed to 63.5 microseconds in 10 microseconds), the relationship of the signal waveforms on the time axis in each part in the horizontal deflection circuit in this case is as shown in FIG. .

In the case of FIG. 11, although the time length tc ⁻ from time To to time T2 when the collector current Ic of the horizontal output transistor is flowing in the negative direction is 21 microseconds, the damper current Id
Is flowing, that is, the time length td from time T1 to time To is extremely short, such as 0.5 microseconds.

As can be seen from the description with reference to FIGS. 8 to 11, the time position of time point To when the base current Ib in the positive direction begins to flow to the base of the horizontal output transistor and the collector current Ic thereof starts to flow. Is greatly influenced by the variation of the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2 and the accumulation times ts1 and ts2 and the variation due to the temperature characteristic. Therefore, as shown in FIG. The period during which the current flows, that is, the time length td from the time T1 to the time To is only 0.5 microseconds, the positive direction base current Ib starts to flow to the base of the horizontal output transistor, and the collector of the horizontal output transistor It means that the time point To at which the current Ic starts to flow tends to be positioned before the time point T1 at which the pulse Vc generated in the collector of the horizontal output transistor ends, In that case, as described with reference to FIG. 6, the collector current Ic will flow during the blanking period Tr when the pulse Vc generated in the collector of the horizontal output transistor exists.
At that portion, an extremely large loss occurs in the horizontal output transistor, resulting in a significant loss of reliability of the horizontal output transistor.

Further, looking at the state of the excitation wave Vcd shown in FIG. 11, for the horizontal scanning period th of 63.5 microseconds, the period ton of the drive transistor of the excitation stage is 14.5 hours.
The proportion of microseconds has been reduced by about half compared to that in the case of FIGS. 8 and 10, and this
In the operation of the horizontal deflection circuit as shown in Fig. 11, the drive transformer cannot store sufficient energy, and the final value of the base current Ib of the horizontal output transistor is reached.
The value of Ib1 becomes small as shown in FIG. 11, and it becomes impossible to make the horizontal output transistor conductive, which also causes an abnormal loss.

By the way, in a multi-scanning television receiver that is operated at a plurality of horizontal deflection frequencies (horizontal scanning periods), when the horizontal deflection frequency becomes high, the point at which the base current of the horizontal output transistor begins to flow is Near the end of the line pulse, the base current of the horizontal output transistor may start to flow during the blanking period in some cases, and during the blanking period, the base current begins to flow to the base of the horizontal output transistor and the horizontal In order to solve the problem that the output transistor causes an abnormal loss and may damage it, it is necessary to change the duty cycle of the horizontal drive pulse of the horizontal deflection circuit according to the horizontal scanning period of the input signal. A multi-scanning television receiver provided with the above-mentioned means is disclosed in JP-A-61-94460. In the conventional technology, even if the phenomenon in which the horizontal output transistor starts conducting within the horizontal blanking period, that is, the so-called "bite phenomenon" can be avoided, the conduction start point of the horizontal output transistor described with reference to FIG. To
However, if it is located after about half of the horizontal scanning period, the horizontal deflection current becomes discontinuous on the way, and the loss of the horizontal output transistor rapidly increases, that is, it is impossible to prevent the so-called "middle-out phenomenon". Since there are various problems such as the possibility that the final base current may be insufficient as described above, a solution has been required.

(Means for Solving the Problems) The present invention includes a horizontal oscillation stage, an excitation stage, and a horizontal output stage, and receives an image at a horizontal scanning cycle according to a plurality of scanning standards by the output of the horizontal output stage. In a horizontal deflection circuit capable of performing horizontal deflection of an electron beam of a tube, the horizontal deflection circuit operates most among the predetermined horizontal scanning periods according to a plurality of predetermined scanning standards. A mode in which the conduction start timing of the horizontal output transistor when operating the horizontal deflection circuit in a short horizontal scanning cycle is located approximately in the center between the end of the blanking period and the midpoint of the horizontal scanning period. Therefore, the duty cycle value of the output square wave of the horizontal oscillation stage is set so that the horizontal deflection circuit operates at a horizontal scanning period longer than the shortest horizontal scanning period described above. And a horizontal oscillation stage configured to include a means for keeping the duty cycle value of the output square wave of the horizontal oscillation stage substantially constant at the duty cycle value set as described above. A deflection circuit is provided.

(Embodiment) Hereinafter, specific contents of the horizontal deflection circuit of the present invention will be described in detail with reference to the accompanying drawings. First, the configuration principle of the horizontal deflection circuit of the present invention will be described.

As is clear from the detailed description with reference to FIGS. 4 to 11, in the horizontal deflection circuit, the base current Ib in the positive direction starts flowing to the base of the horizontal output transistor,
The time position of the time point To when the collector current Ic of it starts to flow is the pulse generated in the collector of the horizontal output transistor.
Time T1 when Vc ends and time approximately at the center of the horizontal scanning period
It is most desirable to position it at a substantially central portion between T2 and when causing the horizontal deflection circuit to perform an operation capable of supplying a horizontal deflection current of a short horizontal scanning period to the horizontal deflection coil. Is greatly affected by the fluctuation of the storage time ts1 of the drive transistor used and the fluctuation of the storage time ts2 of the horizontal output transistor, and thus the pulse width tosc of the output square wave of the horizontal oscillation stage in this case is exactly In order for the horizontal deflection circuit to operate normally in a wide horizontal scanning period range, it is important that the setting be made, and the output rectangular shape of the horizontal oscillation stage 2 regardless of the length of the horizontal scanning period. It turns out that the duty cycle of the wave Vosc needs to be kept roughly constant.

Therefore, in the horizontal deflection circuit according to the present invention, which is capable of horizontally deflecting the electron beam of the picture tube in the horizontal scanning period according to a plurality of scanning standards, the horizontal deflection circuit operates in the shortest horizontal scanning period. When the conduction of the horizontal output transistor is started, the output rectangular shape of the horizontal oscillating stage is set so as to be located approximately in the center between the end point T1 of the blanking period tr and the midpoint T2 of the horizontal scanning period ts. Obtaining the duty cycle value of the wave Vosc, and also the duty cycle value of the output square wave of the horizontal oscillation stage when the horizontal deflection circuit is made to operate at a horizontal scanning period longer than the shortest horizontal scanning period described above, In the case where the horizontal deflection circuit is operated in a wide range of horizontal scanning cycle by providing means for keeping the duty cycle value substantially constant. But, it was as previously described the problem does not occur.

As described above, the conduction start time To of the horizontal output transistor when the horizontal deflection circuit operates in the shortest horizontal scanning period is the end time T1 of the blanking period tr and the horizontal scanning period ts.
When the duty cycle value of the output square wave Vosc of the horizontal oscillation stage, which is determined so as to be positioned approximately at the center between the midpoint T2 and the center point T2, is maintained over a wide horizontal scanning cycle range, For example, depending on the values of the storage times ts1 and ts2 of the transistors used, when the horizontal deflection circuit is made to operate in the state of a long horizontal scanning period, the time point To at which conduction of the horizontal output transistor starts is Although it is possible that there is a deviation from approximately the center between the end point T1 of the blanking period tr and the midpoint T2 of the horizontal scanning period ts,
When the horizontal scanning period is long, the end of the blanking period tr
Since the time between T1 and the midpoint T2 of the horizontal scanning period ts is large, even if the storage times ts1 and ts2 in the transistors used change slightly in this case, FIGS.
The serious problem as described above with reference to the figure does not occur.

FIG. 1 is a block diagram of an essential part of an embodiment of a horizontal deflection circuit of the present invention which is capable of horizontally deflecting an electron beam of a picture tube at a horizontal scanning cycle according to a plurality of scanning standards. The circuit arrangement subsequent to the drive transformer 5 shown in FIG. 1 may be the same as that of the horizontal deflection circuit shown in FIG.
Further, in each component shown in FIG. 1, a component corresponding to each component in the horizontal deflection circuit shown in FIG. 4 is used in FIG. The same reference numerals are used as the reference numerals.

In FIG. 1, reference numeral 1 is a phase comparator for phase-comparing a pulse P of a horizontal scanning period supplied from a preceding stage (not shown) and a pulse Vo supplied from an output unit. The output voltage Vφ is the horizontal oscillation stage 2 of the next stage.
Is supplied to the sawtooth voltage generator 21.

The sawtooth wave voltage generator 21 in the horizontal oscillation stage 2 converts the output voltage Vφ from the phase comparator 1 and the output voltage Vf from the frequency / voltage conversion circuit 14 into a pulse P having the horizontal scanning period described above. Synchronous sawtooth wave voltage S is generated, and it is sent to comparator 22 in horizontal oscillation stage 2 to generate comparison signal S.
Supply as.

The sawtooth wave voltage generator 21 in the horizontal oscillation stage 2 has a sawtooth wave voltage S output from it.
Even if the repetition cycle of changes, its peak voltage V1
And the bottom voltage V2 is configured so as not to move.

Further, in the comparator 22 described above, the sawtooth wave voltage S supplied as the comparison signal from the sawtooth wave voltage generator 21 is used.
And a constant reference voltage Es set in the reference voltage source 23 are compared, and an output square wave Vosc corresponding to the comparison result is output.

FIG. 2 is a diagram for explaining the operation of the horizontal oscillation stage 2 shown in FIG. 1, in which S is a sawtooth voltage S generated by the sawtooth voltage generator 21. And
This sawtooth wave voltage S has a long sawtooth frequency even when its repeating period is short as shown in FIG. 2 (a) or a long repeating period as shown in FIG. 2 (b). Even in the case of the wave voltage S, its peak voltage is always a predetermined constant voltage V1 and its bottom voltage is always a predetermined constant voltage V2.

Further, Es in FIG. 2 represents the reference voltage Es supplied to the comparator 22, and the duty cycle of the output square wave Vosc of the horizontal oscillation stage 2 output from the comparator 22 is the comparator.
Even if the repetition period of the comparison signal S supplied to 22 changes, it is always constant.

It goes without saying that the duty cycle of the output square wave Vosc of the horizontal oscillation stage 2 is changed according to the change of the reference voltage Es set in the comparator 22.

FIG. 3 (a) is a circuit diagram showing an example of the structure of the sawtooth wave voltage generator 21 provided in the horizontal oscillation stage 2 shown in FIG. The charging / discharging capacitor is connected to the power source + E and has the other end connected to the constant current circuit 31, and the constant current circuit 31 has a configuration in which its current value can be controlled from the outside. .

Then, when the charging / discharging capacitor 31 is charged by setting the current value of the constant current circuit 31 to a predetermined constant current value, the potential at the connection point c between the constant current circuit 31 and the charging / discharging capacitor 30 becomes As the charge of the discharge capacitor 30 progresses, it gradually decreases toward zero at a constant rate.

Then, the constant current circuit 31 and the charging / discharging capacitor 30 described above.
The connection point c with is connected to the non-inverting input terminal of the comparator 32, and the inverting input terminal of the comparator 32 is connected to the power source + E.
A DC voltage having a voltage value V2 is applied from the connection point d between the resistor 36 and the resistor 37 in the series connection circuit including the resistors 35 to 37 connected between the resistor and the ground.

Therefore, the potential at the non-inverting terminal of the comparator 32, to which the potential at the point c is supplied, which is in a state of decreasing with a constant slope on the time axis as the charge / discharge capacitor 30 is charged, is as described above. At the moment when the voltage drops below the voltage V2 at the inverting input terminal of the comparator 32 connected to the point d, the output of the comparator 32 inverts and becomes a low level state, whereby the switches 33 and 38 are turned on. Done.

When the switch 33 is turned on, the charge of the charge / discharge capacitor 30 is rapidly discharged by the resistor 34, so that the potential at the connection point c between the constant current circuit 31 and the charge / discharge capacitor 30 is rapidly increased. In addition, since the switch 38 is turned on, the resistor 35 in the series connection circuit composed of the resistors 35 to 37 connected between the power source + E and the ground is short-circuited by the switch 38, whereby the above-mentioned The potential at the connection point d between the resistor 36 and the resistor 37 in the resistor network changes to a high voltage V1 having a relationship of V1> V2 with respect to the voltage value V2.

When the potential at the point c exceeds the potential V1 at the point d, the output of the comparator 32 is inverted from the low level state to the high level state, and the switches 33, 3 are
8 is turned off, the charging / discharging capacitor 30 starts charging again, and the potential at the point c decreases linearly with a certain slope on the time axis. By repeating the above operation,
A sawtooth wave voltage S as shown in FIG. 2 is generated at the point c, and it is supplied to the comparator 22 as the comparison signal S.

It goes without saying that the slope of the sawtooth wave voltage S generated as described above is determined by the current value set in the constant current circuit 31, and when the current value set in the constant current circuit 31 is large. The sawtooth wave voltage S has a steep slope (short repetition cycle), and the constant current circuit
When the current value set to 31 is small, the sawtooth wave voltage S has a gentle slope (long cycle)
become.

Then, the current value of the constant current circuit 31 is a control voltage from the outside, for example, a voltage that is changed by manual adjustment,
Alternatively, for example, by controlling the voltage Vf supplied from the frequency / voltage conversion circuit 14, the sawtooth voltage S output from the sawtooth voltage generator 21 in the horizontal oscillation stage 2 is input to the phase comparator 1. It is possible to generate the sawtooth wave voltage S having the same repetition period as the pulse P having the horizontal scanning period.

3B shows an example of the configuration of the switches 33 and 38 in the sawtooth wave voltage generator 21 illustrated in FIG. 3A, where Q is a transistor, R1 and R2 is a resistor, and X, Y, Z are terminals, and the terminals X, Y, Z are switches 33, 33 in the sawtooth wave voltage generator 21 illustrated in FIG. It corresponds to the terminals X, Y, and Z at 38.

As described above, the sawtooth wave voltage S output from the sawtooth wave voltage generator 21 in the horizontal oscillation stage 2 is supplied to the comparator 22 as the comparison signal S, whereby the phase comparison from the horizontal oscillation stage 2 is performed. An output square wave Vosc in the state shown in FIG. 2 which has the same repetition period as the pulse P of the horizontal scanning period input to the container 1 and whose duty cycle does not change even if the repetition period changes is supplied to the subsequent circuit. Therefore, in the horizontal deflection circuit of the present invention, the horizontal deflection circuit is capable of performing horizontal deflection of the electron beam of the picture tube at a horizontal scanning cycle according to a plurality of scanning standards. The conduction start timing To of the horizontal output transistor when operating in the shortest horizontal scanning cycle is located substantially in the vicinity of the center between the end point T1 of the blanking period tr and the midpoint T2 of the horizontal scanning period ts. The output square wave of the horizontal oscillating stage determines the duty cycle value of the output square wave Vosc, and the output square wave of the horizontal oscillating stage when the horizontal deflection circuit is operated at a horizontal scanning period longer than the shortest horizontal scanning period described above. The duty cycle value of the wave is also kept substantially constant at the above-mentioned duty cycle value.

(Effect) As is apparent from the above description in detail, the horizontal deflection circuit of the present invention includes a horizontal oscillation stage, an excitation stage, and a horizontal output stage, and a plurality of scanning is performed by the output of the horizontal output stage. In a horizontal deflection circuit capable of horizontally deflecting an electron beam of a picture tube at a horizontal scanning cycle according to the standard, the horizontal deflection circuit operates according to a plurality of predetermined scanning standards. In the horizontal scanning cycle, when the horizontal deflection circuit is operated in the shortest horizontal scanning cycle, the conduction start timing of the horizontal output transistor is approximately between the end of the blanking period and the midpoint of the horizontal scanning period. The duty cycle value of the output square wave of the horizontal oscillating stage is set so as to be located in the vicinity of the center, and the horizontal deviation is set at a horizontal scanning cycle longer than the shortest horizontal scanning cycle described above. And a duty cycle value of the output square wave of the horizontal oscillating stage when the directional circuit is made to operate, including means for making the duty cycle value set substantially constant. Since it is a horizontal deflection circuit including a horizontal oscillation stage, the forward direction base current Ib begins to flow to the base of the horizontal output transistor over a wide range of the horizontal scanning period, and the time point To at which the collector current Ic thereof starts to flow. , T1 at the end of the pulse Vc generated at the collector of the horizontal output transistor
And the time T2 approximately at the center of the horizontal scanning period. Therefore, in the horizontal deflection circuit of the present invention, as described above with reference to FIG. When the base current Ib in the positive direction begins to flow and the collector current Ic of the horizontal output transistor begins to flow To
Pulse generated in the collector of the horizontal output transistor
Positioning before the time point T1 at which Vc ends causes an extremely large loss in the horizontal output transistor, significantly impairing the reliability of the horizontal output transistor, and referring to FIG. As described above, the time point To when the collector current Ic of the horizontal output transistor starts to flow is
Since it is located after time T2, which is approximately in the center of the horizontal scanning period, the collector current Ic does not flow out even when the damper current becomes zero, and the horizontal deflection current is interrupted at that part, or at that part. Since a small pulse generated in the collector of the output transistor does not cause a problem such as a large loss in the horizontal output transistor, the present invention can satisfactorily solve the above-mentioned conventional problems. is there.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an embodiment of a horizontal deflection circuit of the present invention, which is capable of horizontally deflecting an electron beam of a picture tube in a horizontal scanning cycle according to a plurality of scanning standards. 2 and 5 to 11 are waveform diagrams for explanation, and FIG. 3 is a circuit diagram showing an example configuration of a sawtooth generator,
FIG. 4 is a block diagram of the horizontal deflection circuit. 1 ... Phase comparator, 2 ... Horizontal oscillation stage, 3 ... Excitation stage horizontal drive transistor, 4 ... Base input resistance, 5
...... Drive transformer, 6 …… Horizontal output transistor,
7 ... Damper diode, 8 ... Return resonance capacitor,
9: Horizontal deflection coil, 10: S-shaped correction capacitor, 11
...... Flyback transformer, 11a …… Primary winding of flyback transformer 11, 11b …… Secondary winding of flyback transformer 11, 11c …… Third winding of flyback transformer 11, 12 …… DC high voltage Generation circuit, 13 ... Voltage control circuit (regulator), 14 ... Frequency / voltage conversion circuit, 21 ... Sawtooth wave voltage generator in horizontal oscillation stage 2, 22, 32 ... Comparator, 23 ... Reference voltage source,

Claims (1)

(57) [Claims] 1. A horizontal oscillation stage, an excitation stage, and a horizontal output stage, wherein the horizontal output stage performs horizontal deflection of an electron beam of a picture tube at a horizontal scanning period according to a plurality of scanning standards. In the horizontal deflection circuit configured to enable the horizontal deflection circuit to operate, the horizontal deflection circuit is operated in the shortest horizontal scanning cycle among the horizontal scanning cycles according to a plurality of predetermined scanning standards which the horizontal deflection circuit operates. When the horizontal output transistor is made to operate, the conduction start timing of the horizontal output transistor is set so that it is positioned approximately in the center between the end of the blanking period and the midpoint of the horizontal scanning period. The output square wave of the horizontal oscillation stage when the duty cycle value of the output square wave is set and the horizontal deflection circuit is operated at a horizontal scan cycle longer than the shortest horizontal scan cycle described above. -Menu tee cycle value also, the horizontal deflection circuit consisting comprise comprise configured horizontally oscillating stage means to be held in a substantially constant set duty cycle value as