JPS6351773A - Horizontal deflection circuit - Google Patents

Abstract

PURPOSE:To conduct a horizontal output transistor (TR) completely by keeping k duty cycle of an output square wave of a horizontal oscillation stage to be proset value when a horizontal deflection circuit is operated at a horizontal scanning period longer than the shortest horizontal scanning period. CONSTITUTION:The duty cycle of the output square wave of the horizontal oscillation stage 2 is set so that the time of start of conducting the horizontal output TR 6 for the horizontal deflection circuit operated at the shortest horizontal scanning period is located nearly the center between the end point of time of the blanking period and the midpoint of the horizontal scanning period. Thin the duty cycle of the output square wave of the horizontal oscillation stage 2 is kept to a preset duty cycle when the horizontal deflection circuit is operated at the horizontal scanning period longer than the shortest horizontal scanning period. Thus, a forward base current Ib of the TR 6 starts flowing over a wide range of the horizontal scanning period, the point of time To when its collector current Ic starts flowing is placed between the end point of time T1 of a pulse Vc generated at the collector of the TR 6 and a midpoint of time T2 of the horizontal scanning period to conduct the TR 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a horizontal deflection circuit in an image reproducing device configured to operate at a plurality of horizontal deflection frequencies (horizontal scanning periods).

(Prior Art) Image reproduction devices that reproduce images using cathode ray tubes (picture tubes) have traditionally been used in television receivers and display devices used in various information devices. For example:

As is well known, in order to reproduce an image on a picture tube in such an image reproduction device, it is necessary to deflect the electron beam of the picture tube in the vertical and horizontal directions according to a predetermined scanning standard.

By the way, the scanning standards that should be applied when reproducing images are 1. For example, in the case of television receivers, the scanning standards that should be applied are often different depending on the standard system of the television system that is being received. When it comes to display devices used in various information devices, the scanning standards are often so different that it can be said that each device manufacturer sets their own scanning standards.

As mentioned above, if the scanning standards are different, the configuration of the deflection circuit will naturally be different.

If an image reproducing device is constructed with a different configuration for each different scanning standard as described above, production will be performed in a high-mix, low-volume production format, which is difficult to manage.

It is also well known that many deflection circuits that can be used for multiple scanning standards have been proposed since they have various disadvantages in terms of cost.

FIG. 4 is a block diagram showing an example of the overall configuration of a horizontal deflection circuit capable of horizontally deflecting the electron beam of a picture tube at a horizontal scanning period according to a plurality of scanning standards; In FIG. 4, 1 is a phase comparator that compares the phase of a horizontal scanning period pulse P supplied from a previous stage (not shown) and a pulse Vo supplied from an output section. By controlling the next horizontal oscillation stage 2 by the output voltage Vφ, the horizontal oscillation stage 2 outputs an output square wave Vosc having a horizontal scanning period th, as shown in FIG. 5(a), for example. be done.

The output square wave V osc of the horizontal oscillation stage 2 described above is as follows.

It is supplied via a base input resistor 4 to the base of the horizontal drive transistor 3 of the excitation stage. The emitter of the horizontal drive transistor 3 is grounded, and its collector is connected to the power supply +Eb via the primary winding 5a of the drive transformer 5.

The secondary winding 15b of the drive transformer 5 described above is as follows.

One end of it is grounded, and the non-grounded end is connected to the base of the horizontal output quadrant transistor, and the horizontal output quadrant transistor is connected to the horizontal drive transistor 3.
The excitation wave V c d generated in the collector circuit of is supplied via the drive transformer 5 to perform a switching operation together with the damper diode 7 as is well known, causing the horizontal deflection coil 9 to have a sawtooth shape with a horizontal scanning period th. A wave current is applied to horizontally deflect the electron beam of the picture tube.

In addition, 8 is a retrace resonance capacitor, 10 is a figure-8 correction capacitor, 11 is a flyback transformer, and 11
a is the primary winding of the flyback transformer 11, 11b is the secondary winding of the flyback transformer 11, and llc is the tertiary winding of the flyback transformer 11.

A DC power supply +Eb for operating the horizontal deflection circuit is connected to the primary winding 11a of the flyback transformer 11 via a voltage control circuit (regulator) 13. The output voltage of the voltage control circuit (regulator) 13 +Eb is connected to one end of 11a.
' is given, and the secondary winding 11b of the flyback transformer 11 boosts the flyback pulse Vc generated at the collector of the horizontal output quadrant transistor to generate a high voltage pulse Vh.
DC high voltage generation circuit that generates V and uses it to generate the anode voltage of the picture tube (high voltage rectifier circuit for generating the anode voltage of the picture tube)
12, which generates DC high-pressure EHT and supplies it to the anode of the picture tube.

In addition, the tertiary winding l of the flyback transformer 11 described above
The output pulse Vo generated at ie is supplied to the phase comparator 1 as a comparison signal as described above, and the horizontal deflection circuit shown in FIG. A well-known automatic frequency control system is constructed by a closed loop of the output stage→phase comparator 1→.

14 is a frequency/voltage conversion circuit, and this frequency/voltage conversion circuit 14 supplies an output voltage Vf corresponding to the frequency of the signal input thereto to the horizontal oscillation stage 2.・Output voltage V of the voltage conversion circuit 14
change its free running frequency based on f, phase comparator 1
The output square wave Vosc is made to oscillate with a repetition period that matches the repetition period of the pulse P with a horizontal scanning period th supplied to the oscilloscope.

Further, the voltage control circuit 13 described above is illustrated in such a way that a horizontal deflection current Iy of a constant magnitude flows through the horizontal deflection coil 9 even if the horizontal deflection circuits operate at different horizontal scanning periods. The output voltage ÷ Eb, which is then supplied as the operating voltage of the horizontal deflection circuit, is
' is configured to have a function of changing the voltage value. The control voltage to be supplied to the voltage control circuit 13 is, for example, a voltage obtained by rectifying the output pulse vO generated at the tertiary winding 'A 11 c of the flyback transformer 11, and a reference voltage. By supplying the voltage to the comparator, 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 diagram of each part shown in FIG. The output square wave Vosc as shown in FIG. 5(a) output from the horizontal oscillation stage 2
makes the drive transistor 3 of the excitation stage conductive by its positive part, thereby making the drive transistor 3 conductive.
Since the potential of the collector of the drive transistor 3 is set to approximately zero potential during the conduction period of the drive transistor 3, the voltage waveform V c d (excitation wave Vcd) of the collector of the drive transistor 3 is generated from the horizontal oscillation stage 2 described above. output square wave V
The conduction period ton of the excitation wave Vcd is as shown in FIG. 5(b).
As shown in , it is longer by an amount corresponding to the storage time tsl in the drive transistor 3.

The base current Ib as shown in FIG. From the falling portion of , the base current Ib changes to the negative direction, and the negative base current flows until the excess carriers in the base layer of the horizontally suspended quadrant transistor are wiped out. ts2 in FIG. 5(c) indicates the accumulation time during which the negative base salt: &Ib flows through the horizontally suspended quadrant distal.

At the end of the accumulation time -ts2 described above, the collector current Ic of the horizontally suspended quadrangle distal becomes zero as shown in FIG. 5(e), and from that point on, the collector current of the horizontally suspended quadrangle In this case, a half-wave sine wave pulse Vc as shown in FIG. 5(d) is generated.

From the time T1 of the end of the pulse Vc described above, (
e) The damper current Id as shown by the dotted line in the middle starts flowing, and then at time 1 To, the collector current Ic starts flowing in response to the base current Ib of the horizontally suspended quadrant distalo starting to flow in the positive direction. By continuously flowing into the damper current Id described above, a current waveform is formed that increases linearly over the entire horizontal scanning period.

Due to the collector current Ic and damper current Id of the horizontally suspended quadrant transistor described above, and the charging and discharging current of the return line resonant capacitor 8, a current I as shown in FIG. 5(f) is generated.
y is passed through the horizontal deflection coil 9, and the electron beam of the picture tube is horizontally deflected.

(Problems to be Solved by the Invention) Now, the operation of the horizontal deflection circuit explained with reference to the waveform diagram shown in FIG. The time point TO at which the collector current IC starts to flow is located between the time point T1 at which the pulse Vc generated in the collector of the horizontally suspended quadrant distal ends and the time point T2 at approximately the center of the horizontal scanning period. For example, as shown in Fig. 6, the base current Ib in the positive direction begins to flow to the base of the horizontally suspended quadrangular distal, and the collector current Ic of the horizontally suspended quadrangular distal begins to flow. If the starting point TO is located before the ending point T1 of the pulse Vc generated in the collector of the horizontally suspended quadrant distal, the collector current Ic flows when the above-mentioned pulse Vc is present. As a result, an extremely large loss occurs in the horizontally suspended quadrant transistor at that portion, which significantly impairs the reliability of the horizontal output transistor.

For example, as shown in FIG. 7, the time point To when the collector current Ic of the horizontally suspended quadrant distal starts flowing is:
If the position is after time T2, which is approximately the center of the horizontal scanning period, even if the damper current becomes zero, the collector current Ic
Since the current does not flow out, the horizontal deflection current is interrupted at that part, and a small pulse is generated in the collector of the horizontal output quadrant distal at that part, causing a large loss in the horizontal output quadrant distal.

Therefore, in the normal design of a horizontal deflection circuit, in order to avoid the above-mentioned problem, a positive base current Ib starts flowing in the base of the horizontal output quadrant transistor, and its collector current IC flows. The starting time To is located between the time TI at which the pulse Vc generated at the collector of the horizontal output quadrangle terminal ends and the time T2 approximately in the center of the horizontal scanning period. In the case of a horizontal deflection circuit that can horizontally deflect the electron beam of a picture tube with a horizontal scanning period according to It was difficult.

Regarding the above-mentioned problems, Part 8 shows concrete numerical values.
A detailed explanation will be given below with reference to the waveform diagrams shown in FIGS. Figure 8 shows the horizontal deflection in the case where the electron beam of the picture tube is horizontally deflected at a horizontal scanning period of 63°5 microseconds (horizontal deflection frequency 15.75 KHz), which has been relatively commonly used in the past. This is an example of the signal waveform of each part of the circuit, and (a
), the horizontal scanning period output from the horizontal oscillation stage is 63.5.
The output square wave V osc is microsecond, and its pulse width tosc is 21 microseconds, which is about ⅓ of the horizontal scanning period.

FIG. 8(b) shows the voltage waveform Vcd (excitation wave Vcd) at the collector of the drive transistor in the excitation stage, and in this figure, the accumulation time tsl in the drive transistor is 4
Shown as being in microseconds.

(c) in Figure 8 is the base current I of the horizontal output transistor.
b, and in this figure, the base current Ib turns negative from the falling part of the excitation wave Vcd, and the accumulation time ts2 in which the negative base current flows until the excess carriers in the base layer of the horizontal output transistor are wiped out is It is shown as being 4 microseconds.

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

8(e) is 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. The period up to T3 is the horizontal scanning period ts, and the time indicated by 1 time T2, that is, the time when the composite current of the damper current Id and the collector current of the horizontal output transistor changes from the negative direction to the positive direction, is the circuit loss. If not, it would be at the center of the horizontal scanning period ts, but in reality, the loss in the circuit (the loss due to the power supplied from the horizontal deflection circuit to the high voltage circuit via the flyback transformer 10) (including), the position of T2 on the time axis takes various values depending on the design, but here As a representative example,
It is shown that T2 is present at the position of the front portion obtained by dividing the horizontal scanning period ts at a ratio of 4:6.

The period during which the damper current d flows in the case where the time relationship of the waveforms of each part in the horizontal deflection circuit is shown in FIG. 8, that is, the time length t from time T1 to time TO
d is 11 microseconds, and the time length tc+ from time T2 to time T3 during which the collector current IC of the horizontal output transistor flows in the positive direction is 32.5 microseconds.
The time length tc- from time To to time T2 during which the collector current Ic of the horizontal output transistor flows in the negative direction is 1.
Since it is 0 microseconds, in this case, the base current Ib in the positive direction begins to flow to the base of the horizontal output transistor,
The time To at which the collector current Ic starts flowing is the time Tl at which the pulse Vc generated at the collector of the horizontal output transistor ends, and the time T2 at approximately the center of the horizontal scanning period.
In this case, the operation of the horizontal deflection circuit does not pose any problem.

Now, in the case of a horizontal deflection circuit in which the horizontal deflection current supplied to the horizontal deflection coil is for only one type of horizontal scanning period, a base current Ib in the positive direction begins to flow to the base of the horizontal output transistor, and The design is such that the time TO at which the collector current Ic begins to flow is located between the time T1 at which the pulse Vc generated in the collector of the horizontally suspended quadrant distal ends and the time T2 approximately at the center of the horizontal scanning period. It's not that difficult.

However, in recent years, picture tubes have been increasingly used in computer display devices.

Moreover, the horizontal deflection frequency of computer display devices is 15KHz to 35KHz.

In many cases, the frequency value is higher than that, and since different horizontal deflection frequencies are adopted depending on the display device, it is necessary to consider a horizontal deflection circuit that can be used for multiple scanning standards. As the demand for this increases, for example, as already described with reference to FIG.

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 approximately matches the repetition period of the pulse P of the horizontal scanning period th supplied to the phase comparator 1. Even if the operating state of the horizontal oscillation stage 2 is changed so that the horizontal oscillation stage 2 is in a state where the A horizontal deflection circuit has also been proposed that can operate in accordance with multiple scanning standards by changing the operating voltage of the horizontal deflection circuit using the voltage control circuit 13 so that y flows. .

By the way, the horizontal oscillation stage 2 used in the horizontal deflection circuit is usually composed of a multivibrator circuit, etc., and even if the period of the output square wave changes, the output square wave will not change. During the pulse, jO20 is often constant.

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, the horizontal oscillation stage 2 has a configuration in which the pulse of the output square wave does not change. horizontal oscillation stage 2
From the state where the output square wave Vosc has a repetition period of 63.5 microseconds in the case shown in FIG. 8 described above,
When the state is changed to a state with a repetition period of 1/2 of that, that is, a state with a repetition period of 32 microseconds, the pulse of the output square wave V osc from the horizontal oscillation stage 2 is as shown in the eighth diagram above. Similarly, if we consider the case where the period remains at 21 microseconds, the output square wave Vosc from the horizontal oscillation stage 2 in this case will be as shown by Vosc in FIG.

Due to circuit design considerations, the retrace time tr may or may not change depending on the change in the horizontal scanning period th, but here, even though the horizontal deflection period th has been changed to 1/2. Accordingly, if we change the retrace time r, which was 10 microseconds in the case of Fig. 8, to 5 microseconds, which is half the time, the scanning period ts in this case is 27 microseconds, and as mentioned above, T1→T
If the ratio of the period 2 and the period T2→T3 is 4:6, the time length of T1→T2 will be 12 microseconds.

However, the output square wave from the horizontal oscillation stage 2 described above
The low level period in the excitation wave Vcd appearing on the collector side of the drive transistor of the excitation stage to which sc is supplied is the output square wave V os from the horizontal oscillation stage 2 described above.
Since it is the sum of 4 microseconds of the drive transistor's volume time ts to 21 microseconds of tosc during the pulse of c, the suspension of the excitation wave Vcd explained with reference to FIG. As is clear from FIG. 9, the time point To at which the collector current Ic of the horizontal output transistor starts flowing is a time υ from the time T2 described above.
This will be the position behind the top.

In this way, when the horizontal scanning period th is changed from 63.5 microseconds to 1/2, 32 microseconds, during the pulse of the output square wave Vosc of the horizontal oscillation stage 2, t os
If c is left at its original value of 21 microseconds without changing, collector current Ic will start flowing even if the damper current becomes zero, as described above with reference to Figure 7. Since there is no horizontal deflection current, the horizontal deflection current is interrupted at that part, and
A small pulse is generated at the collector of the horizontal output transistor in that part, causing a large loss in the horizontal output transistor, and impairing the reliability of the horizontal output transistor.

Therefore, when changing the horizontal scanning period th from 63.5 microseconds to 1/2 of that, 32 microseconds,
Pulse width tos of the output square wave Vosc of the horizontal oscillation stage 2
Regarding c, from the original 21 microseconds to 1/
Considering the case where the time is changed to 10.5 microseconds (however, the retrace time tr is 5 microseconds as in the case of Fig. 9), the time axis of the signal waveform of each part in the horizontal deflection circuit in this case is The above relationship is as shown in Figure 10, and in the case of Figure 10, the period during which the damper current Id flows, that is, the time length td from time T1 to time To, is 5.5 microseconds, and the horizontal output The time length tc- from time TO to time T2 when the collector current Ic of the transistor is flowing in the negative direction is 5.5 microseconds, and from time T2 to time T2 when the collector current Ic of the horizontal output transistor is flowing in the positive direction. Time length until T3 tc+
is 12 microseconds, so in this case, the time TO when the positive base current Ib starts to flow to the base of the horizontal output transistor and the collector current Ic starts to flow is the pulse V generated at the collector of the horizontal output transistor.
The horizontal deflection circuit is located at the center between the time point T1 at which time c ends and the time point T2, which is approximately in the center of the horizontal scanning period, and there is no problem with the operation of the horizontal deflection circuit in this case. , the period during which the damper current Id flows as described above,
In other words, the time length td from time T1 to time To and the time length tc- from time TO to time T2 during which the collector current Ic of the horizontal output transistor flows in the negative direction are each as short as 5°5 microseconds. Since there is no margin for variations, it is necessary to accurately set the pulse width tosc of the output square wave generated by the horizontal oscillation stage 2.

Next, this time, the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2 is set to 172 10.
Leave it at 5 microseconds (11!ltr at M line)
is 10 microseconds as in the case of Fig. 8), and the horizontal scanning period th is changed to 63.5 microseconds.The relationship on the time axis of the signal waveforms at each part in the horizontal deflection circuit in this case is becomes as shown in FIG.

In the case of FIG. 11, even though the time length tc- from time ゛o when the collector current Ic of the horizontal output transistor flows in the negative direction to time T2 is 21 microseconds,
The period during which the damper current Id flows, that is, the time length td from time TI to time To is extremely short, only 0.5 microseconds.

As can be seen from the explanations with reference to FIGS. 8 to 11, the base current Tb in the positive direction begins to flow to the base of the horizontal output transistor, and its collector fil
The time position of the time point TO when 'dtIc starts to flow is largely influenced by variations in the pulse width tosc of the output square wave Vosc of the horizontal oscillation stage 2, the accumulation times tsl and ts2, and fluctuations due to temperature characteristics. As shown in FIG. 11, during the period during which the damper current Id flows, that is, the time length td from time T1 to time TO is only 0.5 microseconds, the base of the horizontal output transistor The base current Ib in the positive direction begins to flow.

It is considered that the time point TO at which the collector current L flow Ic of the horizontal output transistor begins to flow is likely to be located before the time point TI at which the pulse Vc generated at the collector of the horizontal output transistor ends. In that case, as explained with reference to FIG. 6, the pulse Vc generated at the collector of the horizontal output transistor during the retrace period Tr.
Collector current IC flows when the current exists, resulting in an extremely large loss occurring in the horizontal output transistor in that area, resulting in a significant loss of reliability of the horizontal output transistor. become.

Looking at the state of the excitation wave Vcd shown in FIG. 11, we can see that for a horizontal scanning period h of 63.5 microseconds, the period during which the drive transistor in the excitation stage is conductive is ton.
At the time of en14. The ratio of s microseconds has been reduced to about half compared to that in Figures 8 and 10,
Therefore, in the operation of the horizontal deflection circuit as shown in FIG. 11, sufficient energy cannot be stored in the drive transformer, and the final value Ibl of the base f11 flow Ib of the horizontal output transistor is As shown in FIG. 11, it becomes small and the horizontal output transistor cannot be made completely conductive, which is also a cause of abnormal loss.

(Means for Solving the Problems) The present invention provides a horizontal deflection circuit capable of horizontally deflecting an electron beam of a picture tube in a horizontal scanning period according to a plurality of scanning standards. The horizontal oscillation stage is set so that the AMυg start time of the horizontal output transistor is located approximately at the center between the end of the line period and the midpoint of the horizontal scan period when the horizontal output transistor operates in the shortest horizontal scan period. Determine the duty cycle value of the output square wave of
and.

The duty cycle value of the output square wave of the horizontal oscillation stage when the horizontal deflection circuit is operated with a horizontal scanning period longer than the shortest horizontal scanning period described above is also approximately constant to the duty cycle value described above. The present invention provides a horizontal deflection circuit comprising means for holding the horizontal deflection circuit.

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

As is clear from the detailed explanation with reference to FIGS. 4 to 11, in the horizontal deflection circuit, a positive base current Ib begins to flow to the base of the horizontal output transistor, and its collector current Ic begins to flow. It is most desirable that the time position of the starting time TO be located approximately at the center between the time T1 at which the pulse Vc generated at the collector of the horizontal output transistor ends and the time T2 at approximately the center of the horizontal scanning period. In addition, when the horizontal deflection circuit performs an operation that can supply a horizontal deflection current with a short horizontal scanning period to the horizontal deflection coil, the influence of fluctuations in the storage time tsl of the drive transistor used should be considered. In this case, it is important that the pulse width tosc of the output square wave of the horizontal oscillation stage is set accurately, as well as the wide horizontal In order for the horizontal deflection circuit to operate normally within the scanning period.

It has been found that the duty cycle of the output square wave Vosc of the horizontal oscillation stage 2 needs to be kept approximately constant regardless of the length of the horizontal scanning period.

Therefore, in the present invention, in a horizontal deflection circuit that is capable of horizontally deflecting the electron beam of a picture tube at a horizontal scanning period according to a plurality of scanning standards, the horizontal deflection circuit operates at the shortest horizontal scanning period. The output of the horizontal oscillation stage is such that the conduction start timing To of the horizontal output transistor is located approximately at the center between the point T1 at the end of the retrace period tr and the midpoint T2 of the horizontal scanning period ts. square wave V
The duty cycle value of osc is determined, and the duty cycle value of the output square wave of the horizontal oscillation stage when the horizontal deflection circuit is made to operate with a horizontal scanning period longer than the shortest horizontal scanning period mentioned above is also determined. , even if the horizontal deflection circuit is designed to operate over a wide range of horizontal scan periods by providing means for maintaining the above duty cycle value approximately constant. This was done to prevent any problems from arising.

As described above, when the horizontal deflection circuit operates in the shortest horizontal scanning period, the conduction start timing TO of the horizontal output transistor is between the end point T1 of the retrace period tr and the midpoint T2 of the horizontal scanning period ts. The duty cycle value of the output square wave Vosc of the horizontal oscillation stage is determined to be located approximately at the center of .

If the horizontal scanning period is maintained over a wide range of horizontal scanning periods, the horizontal deflection circuit may be operated in a long horizontal scanning period depending on the storage time tsl and ts2 of the transistors used. When the horizontal output transistor starts conducting, the time TO becomes
It may happen that the line deviates from the center between the end point T1 of the retracing device 1'JJ tr and the midpoint T2 of the horizontal scanning period ts, but when the horizontal scanning period is long,
Since the time between the end point T1 of the retrace period tr and the midpoint T2 of the horizontal scanning period ts is large, in this case, the storage times tsl and ts2 in the transistors used are
Even if there is a slight variation in , the serious problem described above with reference to FIGS. 6 and 7 will not occur.

FIG. 1 is a block diagram of the main parts of an embodiment of the horizontal deflection circuit of the present invention, which is capable of horizontally deflecting the electron beam of a picture tube at a horizontal scanning period according to a plurality of scanning standards. The circuit arrangement following the drive transformer 5 shown in FIG. 1 may be the same as that of the horizontal deflection circuit shown in FIG. In each of the illustrated components, the components corresponding to those in the horizontal deflection circuit shown in FIG. sign is used.

In FIG. 1, 1 is a phase comparator that compares the phase of a horizontal scanning period pulse P supplied from a previous stage (not shown) and a pulse vO supplied from an output section. Output voltage ■φ is the next horizontal oscillation stage 2
A sawtooth wave voltage generator 21 is supplied to the sawtooth wave voltage generator 21 at .

The sawtooth voltage generator 21 in the horizontal oscillation stage 2 uses the output voltage Vφ from the phase comparator 1 and the output voltage Vf from the frequency/voltage conversion circuit 4 to generate the pulse P of the horizontal scanning period. A sawtooth wave voltage S synchronized with is generated and supplied as a comparison signal S to the comparator 22 in the horizontal oscillation stage 2.

The sawtooth wave voltage generator 21 in the horizontal oscillation stage 2 described above has a sawtooth wave voltage S output therefrom.
Even if the repetition period of
1 and the bottom voltage v2 do not change.

The comparator 22 also uses a sawtooth voltage S supplied as a comparison signal from the sawtooth voltage generator 21.
and a constant reference voltage E set in the reference voltage source 23.
s and outputs an output square wave Vosc that corresponds to the comparison result.

FIG. 2 is a diagram for explaining the operation of the horizontal oscillation stage 2 shown in FIG. and
This sawtooth wave voltage S has a repetition period of (a
) as shown in Figure 2(b), or the secondary tooth wave voltage S with a long repetition period as shown in Fig. 2(b), its breaking voltage is always at a predetermined level. constant voltage v1. The bottom voltage is always a predetermined constant voltage v2.

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

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

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

Therefore, when the current value of the constant current circuit 31 is set to a predetermined constant current value and the charge/discharge capacitor 31 described above is charged,
The potential at the connection point C between the constant current circuit 31 and the charging/discharging capacitor 30 gradually decreases toward zero at a constant rate as the charging of the charging/discharging capacitor 30 progresses. The connection point C between the circuit 31 and the charging/discharging capacitor 30 is connected to the non-inverting input terminal of the comparator 32, and the inverting input terminal of the comparator 32 is connected between the power source 1E and the ground. resistance 35~3
A DC voltage having a voltage value v2 is applied from a connection point d between a resistor 36 and a resistor 37 in a series-connected circuit consisting of the resistors 36 and 37.

Therefore, as the charging/discharging capacitor 30 is charged, the potential at the non-inverting terminal of the comparator 32 to which the potential at the zero point is supplied, which is in a state of decreasing at a constant slope on the time axis, is as described above. Comparator 3 connected to point d
At the moment when the voltage drops below the voltage v2 at the inverting input terminal of the comparator 32, the output of the comparator 32 is inverted and becomes a low level state, thereby turning on the switches 33 and 38.

When the switch 33 described above is turned on, the electric charge of the charge/discharge capacitor 30 described above is rapidly discharged by the resistor 34, so that the constant current circuit 31 and the charge/discharge capacitor 3
0, and the switch 38 is turned on, the series connection circuit consisting of the resistors 35 to 37 connected between the power supply +E and the ground increases. The resistor 35 is short-circuited by the switch 38, so that the potential at the connection point d between the resistor 36 and the resistor 37 in the resistor network described above becomes a high voltage having a relationship of Vl)V2 with respect to the voltage value ■2 described above. Changes to v1.

Then, when the potential at the 0 point exceeds the potential v1 at the d point, the output of the comparator 32 is reversed from the low level state to the high level state.

The switches 33 and 38 described above are turned off, the charging/discharging capacitor 30 starts charging again, and the potential at the 0 point linearly decreases with a constant slope on the time axis. By repeating the above operation, a sawtooth wave voltage S as shown in FIG. 2 is generated at the 0 point, which is applied to the comparator 22.
It is supplied as a comparison signal S to.

Needless to say, 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 (the green return cycle is short), and when the current value set in the constant current circuit 31 is small, the sawtooth wave voltage S has a gentle slope (has a long repetition period).

Then, the current value of the constant current circuit 31 described above is controlled by an external control voltage, for example, a voltage that can be varied by manual adjustment.
Alternatively, the horizontal oscillation stage 2 may be controlled by the voltage Vf supplied from the frequency/voltage conversion circuit 14, for example.
As the sawtooth wave voltage S output from the sawtooth wave voltage generator 21 in , it is possible to generate a sawtooth wave voltage S with the same repetition period as the pulse P of the horizontal scanning period inputted to the 1-phase comparator 1. .

FIG. 3(b) shows an example of the configuration of the switches 33 and 38 in the sawtooth voltage generator 21 illustrated in FIG. 3(a), where Q is a transistor, R1, R2 is a resistor, and X, Y, and Z are terminals, and the terminals X, Y, and Z are connected to the switch 33 in the sawtooth voltage generator 21 illustrated in FIG. 3(a). Terminal X at 38
, Y, and Z.

The sawtooth wave voltage S output from the sawtooth wave voltage generator 21 in the horizontal oscillation stage 2 as described above is applied to the comparator 22.
By being supplied as a comparison signal S to the horizontal oscillation stage 2, the horizontal oscillation stage 2 has the same repetition period as the horizontal scanning period pulse P input to the phase comparator 1, and even if the repetition period changes, the duty cycle remains constant. The second one where does not change
The output square wave V osc in the state shown is supplied to the subsequent circuit, and the horizontal deflection circuit of the present invention is capable of horizontally deflecting the electron beam of the picture tube with a horizontal scanning period according to a plurality of scanning standards. In a horizontal deflection circuit that is configured to allow
O is the time T1 at the end of the retrace period tr and the horizontal scanning period t
The duty cycle value of the output square wave Vase of the horizontal oscillation stage is determined so that the output square wave Vase of the horizontal oscillation stage is located approximately at the center between the center point T2 of

Furthermore, when the horizontal deflection circuit is operated with a horizontal scanning period longer than the shortest horizontal scanning period, the duty cycle value of the output square wave of the horizontal oscillation stage is approximately equal to the duty cycle value described above. It is held constant.

(Effects) As is clear from the above detailed explanation, the horizontal deflection circuit of the present invention is capable of horizontally deflecting the electron beam of the picture tube at a horizontal scanning period according to a plurality of scanning standards. In a horizontal deflection circuit, when the horizontal deflection circuit operates with the shortest horizontal scanning period, the time when the horizontal output transistor starts conducting is approximately between the end of the retrace period and the midpoint of the horizontal scanning period. When the duty cycle value of the output square wave of the horizontal oscillation stage is determined so as to be located near the center, and the horizontal deflection circuit is made to operate with a horizontal scanning period longer than the shortest horizontal scanning period, The duty cycle value of the output square wave of the horizontal oscillator stage is also maintained approximately constant at the duty cycle value described above, since the horizontal deflection circuit is provided with a means for maintaining it substantially constant over a wide range of horizontal scanning periods. A point in time T when the base current Ib in the positive direction begins to flow to the base of the horizontal output transistor and its collector current Ic begins to flow.
o can be located between the time point T1 at which the pulse Vc generated at the collector of the horizontal output transistor ends and the time point T2 approximately at the center of the horizontal scanning period. Therefore, in the horizontal deflection circuit of the present invention, the As already mentioned with reference to FIG. 6, the point To when the positive base current Ib starts to flow to the base of the horizontal output transistor and the collector current Ic of the horizontal output transistor starts to flow is when the collector current Ic of the horizontal output transistor starts flowing to the collector of the horizontal output transistor. By being located before the end time TI of the generated pulse Vc, an extremely large loss is caused in the horizontal output transistor, and the reliability of the horizontal output transistor is significantly impaired. As described above with reference to , since the time point To at which the collector current IC of the horizontal output transistor starts flowing is located after the time point T2, which is approximately in the center of the horizontal scanning period, even if the damper current becomes zero, collector? 4JIc does not flow out, and there are no problems such as the horizontal deflection current being interrupted at that part, or a large loss occurring in the horizontal output transistor due to a small pulse generated at the collector of the horizontal output transistor at that part. According to the present invention, the above-mentioned conventional problems can be satisfactorily solved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of an embodiment of the horizontal deflection circuit of the present invention, which is capable of horizontally deflecting the electron beam of a picture tube in a horizontal scanning period according to a plurality of scanning standards; 2 and 5 to 11 are explanatory waveform diagrams, FIG. 3 is a circuit diagram showing an example configuration of a sawtooth wave generator, and FIG. 4 is a block diagram of a horizontal deflection circuit. DESCRIPTION OF SYMBOLS 1... Phase comparator, 2... Horizontal oscillation stage, 3... Horizontal drive transistor of excitation stage, 4... Base input resistance, 5... Drive transformer, 6... Horizontal output transistor, 7... Damper diode, 8... Return line resonant capacitor, 9... Horizontal deflection coil, 10...8
character correction capacitor, 11... flyback transformer,
11a... Primary winding of flyback transformer 11, 1
1b...Secondary winding of flyback transformer 11, 11
c...Third winding of flyback transformer 11. 12... DC high voltage generation circuit, 13... Voltage control circuit (regulator), 14... Frequency/voltage conversion circuit. 21... sawtooth voltage generator in horizontal oscillation stage 2,
22.32... Comparator, 23... Reference voltage source. Id 8th Ward Ward Cn

Claims (1)

[Claims] In a horizontal deflection circuit that is capable of horizontally deflecting the electron beam of a picture tube with a horizontal scanning period according to several scanning standards, the horizontal output when the horizontal deflection circuit operates with the shortest horizontal scanning period. The duty cycle value of the output square wave of the horizontal oscillation stage is determined so that the time when the transistor starts conducting is located approximately at the center between the end of the retrace period and the midpoint of the horizontal scanning period, and The duty cycle value of the output square wave of the horizontal oscillation stage when the horizontal deflection circuit is operated with a horizontal scanning period longer than the shortest horizontal scanning period described above is also kept substantially constant at the duty cycle value described above. a horizontal deflection circuit comprising means for causing the horizontal deflection to occur.