JPS58182960A - Horizontal deflecting circuit - Google Patents

Abstract

PURPOSE:To prevent a horizontal output transistor (TR) and a horizontal oscillating circuit from breaking down, by holding oscillation at a higher oscillation frequency when a higher operating voltage is detected. CONSTITUTION:The value of a limit voltage at which the TRQ of a voltage detecting circuit 11 starts turning on is determined by resistance values R1 and R2 of resistances 14 and 15 optionally. Once the TRQ turns on, the collector current of the TRQ is grounded through the resistance 16 of the base circuit of the TR17 and the base and emitter of the TR17 of an oscillation frequency switching circuit 13 to turn on the TR17, which makes a parallel connection between capacitors 19 and 20 for determining an oscillation frequency, setting the oscillation frequency of the horizontal oscillating circuit 1 to lower. When the TRQ is not turned on, the TR17 of the circuit 13 is off and the oscillation frequency of the circuit 1 depends upon only the capacitor 20, allowing the circuit 1 to oscillate at a lower frequency.

Description

[Detailed Description of the Invention] By deflecting the electron beam in both the horizontal and vertical directions and modulating the brightness (or intensity modulation) of the electron beam with a signal, the image display surface (fluorescent surface) of the cathode ray tube is An image playback device that allows images to be projected on top of
For example, it is well known that they have been widely used in television receivers and various character display devices.

By the way, in the above-mentioned image reproducing apparatus, the electronic beam A ? : Horizontal and vertical deflection is required, but the horizontal scanning standard and vertical scanning standard used to assemble the image and the corresponding signal are different from each other, for example, when looking at the television system, the standard system is different. Each method is often different, and
For example, character display devices often have different scanning standards as they have different specifications.

As mentioned above, when there are multiple types of signals with different horizontal scanning standards and vertical scanning standards, there is a dedicated Having to prepare an image reproducing device also imposes a large economic burden on the consumer, so if the image reproducing device is used in multiple VVs with different horizontal scanning standards and vertical scanning standards. In the past, television receivers have been designed to be configured so that they can be used commonly for different types of signals, thereby reducing the economic burden on consumers.
Television receivers that can be used in common with a plurality of standard turpentine systems with different scanning standards have been manufactured and are no longer in practical use.

As described above, in an image reproducing apparatus configured to be able to be used commonly for multiple signals having different scanning standards, the image reproducing apparatus is configured to project an image on the image display screen of a cathode ray tube. The first signal that is supplied is the scanning standard,
In other words, just as it is possible to deflect the electron beam of a cathode ray tube using the horizontal deflection frequency and vertical deflection frequency, which correspond to the horizontal scanning frequency and vertical scanning frequency, the horizontal deflection frequency and vertical deflection frequency are It is designed to be switched and changed inadvertently depending on the signal that is in question.

Now, in an image reproducing apparatus in which the electron beam is deflected using a so-called electromagnetic deflection method, the horizontal deflection circuit generally has a configuration as shown in the broken line frame Hdef in FIG. That is, it is composed of a horizontal output transistor 2, a tandem diode 3, a retrace sympathy capacitor 4, a horizontal 4-direction coil 5, a DC blocking capacitor 6, and a horizontal output coil 7. By connecting a DC power supply E)3 to the cold end of the horizontal output transistor 20, and supplying a driving pulse P having a horizontal scanning period T8 from the horizontal oscillation circuit 1 to the base of the horizontal output transistor 20, the horizontal deflection circuit Hdef performs a well-known operation, a sawtooth current of a horizontal scanning period (horizontal deflection period) flows in the horizontal deflection coil 5, and a noF pulse voltage Vcp is generated at the collector of the horizontal output transistor 2.

Then, the peak-to-peak value IyG of the sawtooth current passed through the horizontal deflection coil 5 as described above, the inductance of the horizontal deflection coil 5 as Ly, and the horizontal scanning period as Ts.
, power supply voltage 4. =, then the following equation (1) is obtained, so the horizontal scanning period Ts is changed while keeping the inductance Ly of the horizontal deflection coil 5 and the power supply-pressure equation constant. When scanning, the peak-to-peak value of the sawtooth wave current y changes in proportion to the horizontal scanning period, and therefore the width of the reproduced image changes in proportion to the horizontal scanning period Ts. .

Therefore, as a horizontal deflection circuit of an image reproducing apparatus commonly used for a plurality of signals having different scanning standards, a structure similar to that shown in FIG. 1 may be conveniently used. 7. In this case, the width of the scratches displayed on the image display surface of the cathode ray tube changes depending on the signal having a different scanning standard. ) 0 No inconveniences like the first one (
In order to do this, one or both of the power supply voltage Sho and the inductance Ly of the horizontal deflection coil 5 are changed according to the change in the horizontal scanning period Ts, and the horizontal deflection coil 5 is changed regardless of the horizontal scanning period Ts. Sawtooth current I flowing in
It is possible to make the peak-to-peak value of y constant, but since it is difficult to configure the intance LyO value of the horizontal deflection coil 5 to be variable according to changes in the horizontal scanning period Ts, it is usually In many cases, the power supply voltage axis is changed in accordance with changes in the horizontal scanning period Ts, so that slight fluctuations in the width of the reproduced image do not occur even with signals of different scanning standards. As a means for changing the power supply voltage axis in accordance with changes in the horizontal scanning period Ts, the horizontal output coil is provided with a tap, and a DC power supply is connected to the tap via a boost diode and a switch. A boost capacitor is connected between the cold end of the horizontal output coil and one end of the DC power supply, and the desired DC voltage value is supplied to the horizontal output coil depending on whether the switch connected to the boost diode is turned on or off. Adopt a configuration that can be varied.

FIG. 2 is a circuit diagram of a horizontal deflection circuit configured to change the power supply voltage axis due to changes in the horizontal scanning period Ts as described above, and is a circuit diagram of the horizontal deflection circuit shown in FIG. The same drawing numerals as those used in FIG. 1 are used for components corresponding to those in FIG.

In FIG. 2, a+b is the intermediate tag of the horizontal output coil 7, and C is the cold end of the horizontal output coil 7, and the cold end C of the horizontal output coil 7 and one end of the DC power supply (not shown) In the example, a boost capacitor 12 is connected between the intermediate tap a and the DC power supply, and a boost diode 8 and a switch 9 are connected between the intermediate tap a and the DC power supply. A boost diode 10 is connected between the and DC power supply type.

In the horizontal deflection circuit shown in FIG. 2, when the switch 9 is turned on and the boost diode 8 is made conductive, a boost voltage Ec as shown in the following equation (2) is generated in the boost capacitor 12.

Ec-(,x +-EL) EB--...(2)n
.

In equation (2), n, n2 are the number of turns n between the intermediate tap a of the horizontal output coil 7 and the hot edge/de of the horizontal output coil 7, and the cold edge C of the intermediate tap a and the horizontal output coil 7. The number of turns n2 between.

As mentioned above, when the switch 9 is in the on state, the voltage at the cathode of the boost diode 10 whose cathode is connected to the intermediate tag b is higher than the voltage at its 7N F. It is in a blocked state because it is.

That is, since the horizontal output coil 7 described above is in an unstable state, the current is applied to the tap a of the horizontal output coil 7 from the DC power supply type through the switch 9 and the boost quadrant 8 as described above. is supplied, the voltage at tap b of the horizontal output coil 7 to which the cathode of the boost diode lO is connected is necessarily higher than the voltage value 1EB of the DC power supply type, and therefore, When the switch 9 is turned on, the boost diode 10 is in a cut-off state.

Next, when the switch 9 is turned off, the DC power supply FEB is connected to the intermediate tap b of the horizontal output coil 7, which is closer to the cold edge C, and is connected to the horizontal output coil 7 through the boost tie 1-10Y. Since the connection σ is connected, the boost voltage Ec is lower than that in the case where the DC power supply type is not connected to the intermediate tap a of the horizontal output coil 7.

Therefore, the horizontal scanning period (horizontal deflection period) is short.

When the switch 9 is turned on or off depending on the situation, the tooth voltage Ec, which is the actual operating voltage of the horizontal deflection circuit, changes high or low as required in accordance with the horizontal deflection period. By determining the positions of intermediate knobs a and b of the horizontal output coil 7 to which the boost tie auto 8°10 is connected, a constant peak-to-peak value is always maintained regardless of the horizontal deflection period of 1"J. This is because the sawtooth current 1y has a deflection of -3 inc.

In the above explanation, the boost diode 1o was connected to the intermediate tap b of the horizontal output coil 7, but when the deflection period is not switched to the longer one, the DC power supply is connected to the horizontal output coil via the boost diode 10. A horizontal deflection circuit may be configured to be connected to the cold end C of the output coil 7.

In the image reproducing device equipped with the horizontal deflection circuit having the configuration shown in the second diagram, images based on two types of signals having different horizontal scanning frequencies are selectively projected on the image display surface of the cathode ray tube. In this case, the oscillation frequency of the horizontal oscillation circuit 1 is set so that the drive pulse P of the horizontal scanning period Ts corresponding to the horizontal scanning frequency of the signal targeted for image reproduction is given from the horizontal oscillation circuit 1 to the horizontal deflection circuit. At the same time, the switch 9 in the horizontal deflection circuit is turned on and off depending on the shortness and length of the horizontal scanning period, thereby changing the reproduced image projected on the image display screen of the cathode ray tube in the image reproduction apparatus. The width of the signal can be kept constant regardless of the horizontal scanning frequency of the signal.
According to the horizontal deflection circuit configured as shown in FIG. 2, the above-mentioned problems can be solved.

However, in the horizontal deflection circuit having the configuration shown in FIG. The problem was that the output truck 7 and 2 could be damaged.

The above problem will be specifically explained with reference to FIG. 4 as follows. That is, FIG. 4 shows a horizontal deflection circuit having the configuration shown in FIG. Next, it shows how the boost voltage Ec changes when the switch 9 is turned off at time t2, and as can be seen from this figure, the switch 9 is turned off from the off state. The voltage Ec of the boost capacitor 12 at time 1. and time t2 when the switch 9 is turned off from the on state does not change instantaneously to a predetermined value due to the time constant of the circuit. After the time t2 when the switch 9 changes from the on state to the off state, the boost diode 8 is immediately cut off according to the off state of the switch 9 at the time t2, and the boost capacitor 12 is cut off from the time t2. Since the boost diode 10 is also cut off for a while until the time t3 when the voltage Ec reaches the voltage peak of the DC power supply, the horizontal output transistor 2 is cut off from the time t2 to the time t3. This means that the lake voltage Ec of the boost capacitor 12 is reduced only by the consumed current.

On the other hand, since the drive pulse P supplied from the horizontal oscillation circuit 1 to the horizontal output transistor 2 of the horizontal deflection circuit is changed to a longer horizontal scanning period corresponding to the lower horizontal deflection frequency after time t2, During the period from to time t, a horizontal deflection current Iy with an abnormally larger peak-to-peak value than the original peak-to-peak value will flow.
Therefore, the horizontal output transistor 2 may be damaged, or the horizontal oscillation circuit 1 may be damaged due to damage to the horizontal output transistor 2.

The present invention has been made with the object of providing a horizontal deflection circuit capable of solving the above-mentioned problems, and the specific contents of the horizontal deflection circuit of the present invention will be explained below with reference to the accompanying drawings. will be explained in detail.

FIG. 5 is a circuit diagram of one embodiment of the horizontal deflection circuit of the present invention, and in FIG. 5, the components corresponding to the components of the horizontal deflection circuit shown in FIG. The same drawing numerals as those used in FIG. 2 are given.

In FIG. 5, 11 is a voltage detection circuit, and
13 is an oscillation frequency switching circuit. In FIG. 5, the voltage detection circuit 11 is shown as being constituted by a transistor Q and resistors 14 and 15.
The oscillation frequency switching circuit 13 is composed of a switch circuit composed of a transistor 17, a base resistor 16, a collector resistor 18, etc., and a cone capacitor 19, 20 for determining the oscillation frequency in the horizontal oscillation circuit l. However, the voltage detection circuit 11 and oscillation frequency switching circuit 13 to be used in carrying out the present invention may have a configuration other than that shown in FIG. Of course, may also be used.

In FIG. 5, the emitter of the transistor Q of the voltage detection circuit 11 is connected to the DC power supply EBK, and the base of the transistor Q is grounded through the resistor 14 and connected horizontally to the boost capacitor 12 through the resistor 15. It is connected to the ground point of the cold end C of the output filter 7.

Let VBE be the voltage between the base and emitter of the transistor Q of the voltage detection circuit 11, and let the resistance value of the resistor 14 be R1,
Assuming that the resistance value of the resistor 15 is R2, the transistor Q becomes conductive when the voltage across the resistor 14 is (EB-VB
E), which is shown by the following equation (3).

El in equation (3), ie, the voltage value E1 of the limit voltage at which the transistor Q starts conduction, can be arbitrarily set by the resistance values R, , R2 of the resistors 14.15.

When the transistor Q becomes conductive, the collector current of the transistor Q flows to the ground through the resistor 16 of the base circuit of the transistor 17 of the oscillation frequency switching circuit 13 and the base-emitter of the transistor 17, making the transistor 17 conductive, and changing the oscillation frequency. Capacitor for determination 19.20t
'As a parallel connection, the oscillation frequency of the horizontal firing circuit l1181 is set to the lower value.

Further, when the transistor Q in the voltage detection circuit 11 is non-conductive, the transistor 17 of the oscillation frequency switching circuit 13 becomes non-conductive, and the oscillation frequency of the horizontal oscillation circuit l is not determined by the capacitor 20. Therefore, the oscillation frequency of the horizontal oscillation circuit 1 is the higher value.

Therefore, by selecting the resistance values R1 and R2 of the resistor 14.15 in the voltage detection circuit 11, the horizontal scanning period (horizontal deflection period) is shortened to set the limit voltage E at which the transistor Q should not become conductive. sometimes boost capacitor 12
That is, the value of the boost voltage generated in the boost capacitor 12 when the switch 9 is in the on state.
is lower than the value of the boost voltage generated in the boost capacitor 12 when the horizontal scanning period (horizontal deflection period) is lengthened, that is,
If the voltage value E is set to be higher than the value of the boost voltage generated in the boost capacitor 12 when the switch 9 is turned off, the voltage will be increased after the switch 9 is changed from the on state to the off state. , when the boost voltage drops below the limit voltage E, set as above,
The transistor Q becomes conductive, the transistor 17 of the oscillation frequency switching circuit 13 becomes conductive, the capacitors 19 and 20 for determining the oscillation frequency are connected in parallel, and the oscillation frequency of the horizontal oscillation circuit I is set to the higher value. It should be changed to

FIG. 6 is a time chart for explaining the above-mentioned operation. is the time when the switch 9 changes from the off state to the on state, t2 is the time when the switch 9 changes from the on state to the off state, and t& is the time when the transistor Q of the voltage detection circuit 11 conducts and the oscillation frequency is switched. This is the time when the oscillation frequency of the horizontal oscillation circuit 1 is switched to a lower oscillation frequency by the operation of the circuit 13, and as is clear from the time chart of FIG.
In the horizontal deflection circuit of the present invention, at time t2 when the switch 9 is switched from the on state to the off state, the oscillation frequency of the horizontal oscillation circuit 1 is not immediately switched to the lower oscillation frequency V; During the time from time t2 when the boost capacitor 12 is switched from the OFF state to the OFF state until the time ta when the terminal voltage Ec of the boost capacitor 12 reaches the limit voltage E preset in the voltage detection circuit 11, The repetition period of the drive pulse P supplied from the horizontal oscillation circuit 1 to the horizontal output transistor 2 of the horizontal deflection circuit is maintained at the shorter horizontal scanning period, and the voltage detection circuit 11 outputs the boost capacitor 12. At time ta when the terminal voltage Ec becomes lower than a predetermined limit voltage "E1," the transistor Q becomes conductive, causing the transistor 17 of the oscillation frequency switching circuit 13 to conduct, thereby causing the oscillation frequency determining capacitor 19. 20 are connected in parallel to change the oscillation frequency of the horizontal oscillation circuit 1 to a lower oscillation frequency (longer horizontal scanning period), the horizontal deflection circuit of the present invention has the above-mentioned problems. In other words, if the oscillation frequency of the horizontal oscillation circuit 1 is low while the boost voltage Ec is sufficiently high, the peak-to-peak value of the horizontal deflection current will be abnormally increased, and the horizontal output transistor 2 will be damaged. There are no problems such as

As mentioned above, in a normal design, the time from time t2 when the switch 9 is switched from the on state to the off state to the time t1 when the horizontal scanning frequency is switched to the lower oscillation frequency is at most 10 points 200#')
Since the time is within seconds, no abnormality in the image that occurs when the switch 9 is switched is felt.

As is clear from the detailed explanation above, when an image is displayed on the display screen of the cathode ray tube, which of the two types of signals mentioned above causes the image to be displayed on the display screen of the cathode ray tube. In a device configured such that the operating voltage of the horizontal deflection circuit can be varied in accordance with the horizontal scanning period so that there is no fluctuation in the width of the reproduced image even when it is displayed, When the voltage detection circuit detects that the operating voltage of the horizontal deflection circuit is the higher voltage, the oscillation frequency in the horizontal oscillation circuit is set to the higher oscillation frequency corresponding to the higher horizontal scanning frequency. Since the horizontal output transistor and the horizontal oscillation circuit are left as they are, damage to the horizontal output transistor and horizontal oscillation circuit, which were problems in the past, does not occur, and the present invention successfully solves the problems in the past and provides image reproduction with excellent performance. The device can be easily provided.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a horizontal deflection circuit with a general configuration, and Figure 2 is a block diagram of an example configuration of a horizontal deflection circuit that prevents the width of a reproduced image from changing even when the horizontal scanning period range is changed. FIG. 4 and FIG. 6 are time charts for explaining the operation, and FIG. 5 is a block circuit diagram of an embodiment of the horizontal deflection circuit of the present invention.

Claims (1)

[Claims] In an image reproducing apparatus configured so that no width fluctuation occurs in the reproduced image even when the image is projected on the image display surface of the cathode ray tube by either of the two types of signals. Connect the hot end of the horizontal output fill provided with the knob in the horizontal deflection circuit, and also connect the hot end of the horizontal output fill provided with the knob in the horizontal deflection circuit, and also connect the first
A DC power source is connected to the tap of the horizontal output coil through a switch and a first diode showing a forward connection polarity with respect to the operating current, and a first diode near the cold end of the horizontal output coil. The above DC power supply is connected to the tap or cold end of No. 2 through the second tie-o + One end of the DC power supply described above is connected to the end via a capacitor, and a voltage detection device is connected to the connection point of the cold-ended capacitor of the horizontal output coil to detect the voltage at the connection point. When the circuit is connected and the voltage detected by the voltage detection circuit described above becomes less than a predetermined voltage value, the oscillation frequency of the horizontal output circuit that excites the horizontal output circuit is changed. A predetermined high frequency is set, and on the other hand, when the voltage value detected by the voltage detection circuit described above becomes lower than the predetermined voltage value, the horizontal generator circuit that excites the horizontal output circuit. A horizontal deflection circuit in which the oscillation frequency of the horizontal output circuit is switched and controlled according to the detection result of the voltage detection circuit described above so that the silkworm frequency is a predetermined low frequency value.