JPS5940346B2 - horizontal deflection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horizontal deflection device for a television receiver that is capable of receiving television broadcasts with a plurality of different numbers of scanning lines.

The number of horizontal scanning lines and the number of frames per second in a television signal can be determined arbitrarily to some extent, so they may differ depending on the region or country where the broadcasting station is located. Various types of television signals are used, especially in Europe.

Therefore, television receivers used in such areas are designed to be able to receive television signals of various formats even at different deflection frequencies by appropriately switching the circuit. I need.

FIG. 1 shows an example of a horizontal deflection circuit of a television receiver whose circuit configuration is changed according to the television signal format (namely, the number of scanning lines).

This circuit is configured to operate by switching between two types of horizontal deflection frequencies, high and low. 1 constitutes a horizontal deflection oscillator together with an oscillating coil 2, a resonant capacitor 4, and a coupling capacitor 5. A transistor 6 is an excitation circuit. 7 is a horizontal output transistor that forms a horizontal output circuit together with a damper diode 8 and a resonant capacitor 9 and supplies a horizontal deflection current to a horizontal deflection coil 10; 16 is a horizontal output transistor that is composed of switching transistors 17 and 18; the additional coil 3 is an oscillating coil; 2
21 is a flyback transformer, 12 is a boost diode, 1 is an electronic switch circuit for connecting in parallel with
3 is a boost capacitor, 19 and 20 are bias resistors for applying the signal from the switching signal input terminal 30 to the base of the transistor 19, 22 is a contact of a relay 23 for switching the output circuit, and 11 is an S-shaped Correction capacitor, 14 is boost voltage adjustment resistor, 15
This is a resistance to prevent bending.

When the receiver receives a television signal in the form of a signal with a low deflection frequency (hereinafter referred to as the L-power type), a circuit linked to a tuning device such as a tuner connects the terminal 30 to the television signal. A zero or negative signal is applied to similarly prevent current from flowing through relay 23, causing contact 22
is switched toward point A.

Also, when the receiver is switched to receive a television signal of a system with a high deflection frequency (hereinafter referred to as E system), the channel selection device connects the terminal 30.
When a positive DC signal is applied to the relay 23, a current simultaneously flows through the relay 23, and the contact 22 is switched to the B point.

In the L method, since the signal at the terminal 30 is zero or negative, both the transistors 17 and 18 are kept in the cut-off state.The horizontal deflection frequency is a low frequency determined by the horizontal oscillation coil 2 and the capacitors 4 and 5. The output transistor 7 is driven through the drive circuit 6 to pass a horizontal deflection current to the horizontal deflection coil 10, and the flyback transformer 21 generates a high output voltage.

Next, when switching to the E method, a positive DC voltage is applied to the terminal 30, transistors 17 and 18 become conductive, and the additional coil 3 is connected in parallel with the horizontal oscillation coil 2 to increase the horizontal oscillation frequency. do. Therefore, the output transistor 7 causes a high frequency horizontal deflection current to flow through the horizontal deflection coil 10, and the flyback transformer 2
A high-frequency horizontal deflection current is passed through 1 to generate a high voltage. By the way, in both the L method and the E method,
The deflection current 1Y flowing through the horizontal deflection coil 10 must be kept constant.

This deflection current 1Y is expressed by the following equation, where the voltage at point A of the flyback transformer 21 is E1, the inductance of the deflection coil 10 is L, and the horizontal scanning period is Ts.

Therefore, if the design is made so that the deflection current IY is an appropriate value when operating in the L-force type, switching to the E-type will increase the horizontal deflection frequency, shorten the scanning period Ts, and reduce the TSE. When it becomes, as is clear from equation (1), A
The voltage E at the point must be increased.

Therefore, we switched to the E method to increase the horizontal deflection frequency, and at the same time activated the relay 23 to switch its contact 22 to point B, operating the boost circuit consisting of the diode 12, capacitor 13, and resistor 14, and increasing the charging voltage of the capacitor 13. By boosting the voltage at point A, the required horizontal deflection current 1
I'm trying to get Y.

Therefore, with a circuit having such a configuration, it is possible to receive television signals having two types of horizontal deflection frequencies, high and low. If television signals of different signal formats (number of scanning lines) are switched as described above while the machine is in use, the horizontal output transistor 7 may sometimes be destroyed.

Therefore, in the past, it was necessary to ensure reliability by using a transistor with a sufficiently high rating for the output transistor 7, and by using other circuit elements commensurate with the rating, which resulted in a large cost increase. Not only did this become a factor, but it also made it impossible to obtain sufficient stability of operation. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and
To provide a horizontal deflection circuit for a television receiver which is highly reliable and does not increase costs and is capable of receiving television signals of different signal strength types.

To achieve this object, the present invention is characterized in that a specific time relationship is established between the frequency switching operation of the horizontal oscillator and the switching operation of the horizontal deflection output circuit.

The present invention will be explained below with reference to FIGS. 3 and 4.

FIG. 3 shows one embodiment of the present invention, in which the same parts as in the circuit of FIG. 1 are given the same reference numerals.

That is, a horizontal oscillation circuit including a transistor 1 as an active element, a horizontal output transistor 7 driven by its output via a drive circuit 6, a horizontal deflection coil 10, a F-back transformer 21, and an additional coil 3 are combined into a horizontal oscillation coil. An electronic switch circuit 16 is connected in parallel to 2 to switch from the L system to the E system, and a contact 22 of a horizontal output switching relay 23 is used to apply a boost voltage to the transistor 7 by charging the capacitor 13 when switching to the E system. A horizontal deflection circuit is constructed by the following, and an electronic switch circuit 16
A capacitor 28 is provided at the base of the transistor 17.

Capacitor 28 is connected to transistor 1 along with resistors 19 and 20.
A time constant circuit for the base voltage of 7 is constructed, and the terminal 30
Different time constants are given to changes in the base voltage of the transistor 17 when the switching signal is applied and when it is removed.

Now, in order to switch from the L method to the E method, when a positive signal is applied to the terminal 30, the transistors 17 and 18 become conductive after a delay time determined by the parallel resistance of the resistors 19 and 20 and the time constant determined by the capacitor 28, and the additional coil 3 is connected in parallel to the oscillation coil 2 to switch the oscillation frequency to the E method.

Also, when the positive signal is removed from terminal 30 and terminal 30 is opened to switch from the E-force type to the L-force type, the charge in the capacitor 28 is discharged by the resistor 20, and the charge in the capacitor 28 is discharged by the resistor 20. After a delay time determined by the time constant of the capacitor 28 has elapsed, the transistors 17 and 18 are cut off, disconnecting the additional coil 3 from the oscillation coil 2, and switching the frequency to the L mode. That is, the resistors 19, 20 and the capacitor 28 cause the electronic switch circuit 16 to switch from the L system to the E system.
The time TA (L, E) for switching from the power type to the L type can be set to be shorter than the time TA (E, L) for switching from the E type to the L type. By selecting constants to appropriate values, it is possible to make TA (L, E) shorter and TA (E, L) longer than the switching operation time of the relay 23 that switches the output circuit. .

By the way, in the horizontal deflection circuit shown in FIG. 1, the electronic switch circuit 16 is used to switch the horizontal oscillation circuit, and its operation speed is extremely fast, and the frequency of the oscillation circuit changes almost instantly when the additional coil 3 is connected. Since the switching is possible, the time required for the switching is negligibly small.

However, in the horizontal deflection output circuit, since the voltage and current values of the circuit to be switched are large, a large capacity switching device such as a relay must be used, and the switching time is inevitably limited to the electronic switch circuit 16. The switching time of the horizontal deflection frequency of the oscillator circuit including the oscillation circuit is longer than the switching time of the horizontal deflection frequency, and the difference between them is usually as much as 2.5 to 3 milliseconds.

To explain what kind of phenomenon occurs due to the difference in switching time, consider that when the horizontal deflection frequency is switched from high force to low force, that is, when switching from E system to L system, horizontal oscillation occurs. The frequency of the circuit switches almost instantly to the lower deflection frequency.

By the way, as mentioned above, switching the output circuit requires about 2.5 to 3 milliseconds, which is the operating time of the relay.
Let this time be TB(B,L). Therefore, this 2.5
For ~3 milliseconds, the voltage at point A of the flyback transformer is a voltage in which the boost voltage in E method is superimposed on +B, that is, voltage EE, and on the other hand, the horizontal deflection period Ts is a low horizontal deflection frequency. TSL corresponds to , and TSL〉 for the horizontal deflection period TSE in the E-force formula.
From the relationship of TSE, the horizontal deflection current TY becomes EE>
E, therefore, a current larger than the deflection current determined by equation (1) is generated.In the switching period 31 shown in FIGS. is horizontal output transistor 7
This will cause the output transistor 7 to be destroyed.

Furthermore, when the horizontal deflection frequency is switched from low to high, that is, when switched from the L method to the E method, the horizontal oscillation circuit is switched in an extremely short time TA (L, E),
The output circuit is switched once the switching time TB (L, E) of the relay 23 has passed. And the time difference, TB(L,E)−
During the period corresponding to TA (L, E), the voltage at point A in the EL:L method, that is, the unboosted +B
Voltage TsE: This is one horizontal scanning period in the E method, and since TSE<TSL and EL<EE, only the same collector voltage as in the steady state or a voltage lower than that is applied to the transistor 7, and no problem occurs.

However, when switching from the L-force type to the E-force type, if the switching time TA (L, E) of the horizontal oscillation circuit becomes longer than the switching time TB (L, E) of the horizontal output circuit, the switching time Difference time, TA(L,E)-TB(L
, E), the output circuit has already been switched to the E-power type and a boost voltage is applied to the point A, but the horizontal oscillation circuit is still in the L-power type.

Therefore, the deflection current 1Y is the same as equation (2), and if the abnormal current and voltage shown in periods 31 in FIG. 2 A and B are applied to the output transistor 7, there is a risk of damage. become.

As can be understood from these results, in order to operate the output transistor 7 with a larger collector current and voltage than in the steady state during switching operation between the E method and the L method, and to prevent it from being destroyed due to this, it is necessary to It can be seen that the switching operation must be performed so as to satisfy the following conditions.
(1) When switching from the E method to the L method, the switching time TA (E, L) of the horizontal oscillation circuit is made longer than the switching time TB (E, L) of the output circuit.

(2) When switching from the L power type to the E type, the switching time TA (L, E) of the horizontal oscillation circuit is made shorter than the switching time TB (L, E) of the output circuit. That is, TA(E,
L)>TB(E,L) TA(L,E) x TB(L,E) The switching operation must be performed while maintaining the following conditions.

As mentioned above, in the embodiment of the present invention shown in FIG. 3, by providing a time constant circuit consisting of resistors 19, 20 and capacitor 28 in the base circuit of transistor 17 of electronic switch circuit 16, the above two conditions can be achieved. The switching operation is performed to satisfy the conditions.

Therefore, according to the embodiment of the present invention shown in FIG.
Even if the horizontal deflection device is configured to perform television reception by switching the horizontal deflection frequency according to television signals of different signal formats, no abnormality will occur in the horizontal output transistor 7, so the horizontal output circuit It is no longer necessary to use a transistor with a rating higher than the collector loss required for operation, making it possible to reduce costs and maintain high circuit reliability, thereby eliminating the drawbacks of the prior art.

FIG. 4 shows another embodiment of the present invention, which differs from the embodiment of FIG. 3 in that the signal input terminal 3 of the electronic switch circuit 16
0 is provided with a time constant circuit consisting of a resistor 24 and a capacitor 25, and the relay 23 is also provided with a time constant circuit consisting of a resistor 26 and a capacitor 27, and the capacitor 28 in FIG. 3 is not used. It is.

Next, to explain the operation, when a positive signal is applied to the terminal 30 to switch from the L method to the E method, the resistor 24
The operation of the electronic switch circuit 16 is delayed by a time determined by the time constant of the capacitor 25.

Also, in order to switch from the E-force type to the L-type, when the terminal 30 is set to zero voltage, the charge of the capacitor 25 is reduced by the resistors 19 and 2.
0 through the series circuit, and the disconnection operation of the additional coil 3 by the electronic switch circuit 16 is delayed by that time constant. Furthermore, the relay 23 includes a resistor 26 and a capacitor 27.
is connected, so when voltage is applied to the relay 23 to switch from the L method to the E method, the time required for the voltage to be charged to the capacitor 27 through the resistor 26, the relay 2
The operation of step 3 is delayed.

However, in order to switch from E method to L method, relay 2
When the voltage at 3 is turned off, the charge in capacitor 27 is discharged through relay 23, providing only a small delay time. Therefore, if the sizes of resistors 19, 20, 24 and capacitor 25 are selected to appropriate values, TA(E,L
)+TA(L,E), and if the sizes of the resistor 26 and capacitor 27 are set to appropriate values according to the resistance value of the relay 23, TB(L,E)>TB(E, L), and furthermore, TB(L,E)>TA(L,E) +TA(E,L)>TB(E,L).

Therefore, in the embodiment of FIG. 4, the resistors 19, 20, 24 constituting the time constant circuit of the electronic switch circuit 16 are
, a capacitor 25, and a relay 2 for switching the output circuit.
By appropriately selecting the resistor 26 and capacitor 27 that constitute the time constant circuit provided in No. 3, the above conditions can be satisfied. ) and TB(L,E), and the horizontal output transistor can be prevented from being destroyed as in the embodiment shown in FIG. 3. It is possible to obtain a device with high performance.

[Brief explanation of drawings]

Fig. 1 is an electrical circuit diagram showing an example of a horizontal deflection device that operates by switching between two different horizontal deflection frequencies; Fig. 2 is a diagram for explaining the abnormal phenomenon that occurs when switching the horizontal deflection frequency; 3 and 4 are electrical circuit diagrams showing respective embodiments of the present invention. 1... Transistor for horizontal oscillation, 2...
・Horizontal oscillation coil, 3...Additional coil, 6...
...Excitation circuit section, 7...Horizontal output transistor, 10...Horizontal deflection coil, 16...
...Electronic switch circuit, 21...Flyback transformer, 22...Relay 23 contact.

Claims (1)

[Claims] 1. A horizontal oscillator having a first switching device for switching the horizontal oscillation frequency, and a horizontal deflection current that is driven by the horizontal oscillator and operates at a plurality of different horizontal deflection frequencies;
a horizontal output circuit having a second switching device for maintaining any of the high output voltages at a substantially constant value, and when the horizontal deflection frequency is switched from a high frequency to a low frequency, the first The switching by the switching device is delayed from the switching by the second switching device, and when switching from a low frequency to a high frequency, the switching by the first switching device is made earlier than the switching time of the second switching device. Therefore, a horizontal deflection device characterized in that a time constant circuit having a time constant different depending on the switching direction is provided for at least the first switching device.