JPH0516770Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Purpose of the invention] (Field of industrial application) The invention is applicable to monitor-type television receivers, CRT display devices, etc. that can receive two or more types of signals with different horizontal scanning frequencies. Concerning the horizontal deflection circuit used.

(Prior Art) Conventionally, a horizontal deflection circuit as shown in FIG. 3 has been used in a monitor type television receiver or a CRT display device configured to be able to switch the horizontal scanning frequency.

The horizontal deflection circuit shown in FIG. 3 includes a frequency switching switch 1, an oscillation frequency switching circuit 2, a horizontal oscillation circuit 3, a horizontal drive circuit 4, a horizontal output circuit 5, and a horizontal output circuit switching circuit. It is equipped with a lever 6 for use. Switch 1 is capable of switching between contact a at high level potential (voltage of voltage source V ₁ ) and contact b at low level potential (earth potential), and switching circuit 2 includes transistors Q ₁ and Q ₂ and resistor R ₁ ~ _R5 , and by switching switch 1 between high and low level potentials, the potential at the connection point of resistors _R4 and _R5 is switched high and low, and this potential is used as a switching signal for adjusting the oscillation frequency. It is applied to the horizontal oscillation circuit 3 through the volume VR and an integrating circuit consisting of a resistor R ₆ and a capacitor C ₁ connected to its sliding end. The horizontal oscillation circuit 3 is composed of, for example, a multivibrator type oscillation circuit in which two transistors are emitter-coupled, and its horizontal oscillation output is input to the base of the horizontal output transistor 7 of the horizontal output circuit 5 via the horizontal drive circuit 4. The horizontal output circuit 5 includes a horizontal output transistor 7, a damper diode 8, resonance capacitors 9 and 10, and horizontal amplitude coils 11 and 1.
2. It is composed of a horizontal deflection coil 13 and an S-shaped correction capacitor 14, and a flyback transformer FBT is connected to the collector of the horizontal output transistor 7.
Both ends of either the resonant capacitor 9 or the horizontal amplitude coil 11 are short-circuited by a switch piece of a relay 6 in response to switching of the switch 1. In the relay 6, when the switch 1 is switched to the high level potential side (contact a), the switch transistor _Q3 is turned on and a driving current is supplied from the voltage source _V3 to the relay winding.

In the circuit configured as described above, when the changeover switch 1 is set to contact a and the changeover signal becomes high level, the oscillation frequency of the horizontal oscillation circuit 3 increases, while in the horizontal output circuit 5, the capacitance of the resonant capacitor and the amplitude coil The inductance of the deflection current is reduced and the frequency of the deflection current is also increased.

However, in the above-mentioned circuit, if there is even a slight shift in the switching timing between the horizontal oscillation circuit 3 and the horizontal output circuit 5 when switching the frequency, the value of the flyback pulse increases.
For example, when switching from a low-frequency operating state to a high-frequency state, if the horizontal output circuit 5 switches first, the flyback pulse generated in the horizontal output circuit 5 will be different from the normal one, albeit for a moment. The value becomes abnormally higher than the value, and there is a risk that the horizontal output transistor 7 may be deteriorated or destroyed. On the other hand, if the horizontal oscillation circuit 3 were switched first when switching from a high frequency operating state to a low frequency operating state, there was a risk that the flyback pulse would instantaneously become abnormally high as described above.

(Problem to be solved by the invention) As mentioned above, in the conventional circuit, in order to switch the horizontal scanning frequency, the flyback pulse of the horizontal output circuit becomes abnormally high at the moment the circuit operation is switched, and the output There was a problem that it had a bad effect on the transistor.

Therefore, the present invention is intended to eliminate the above problem, and aims to provide a horizontal deflection circuit that can prevent the flyback pulse generated in the horizontal output circuit from becoming abnormally high when switching frequencies. It is something.

[Structure of the invention] (Means for solving the problem) The invention comprises a signal generating means for generating a switching signal of a high level or a low level in response to signal inputs of different horizontal scanning frequencies, and a predetermined time constant. an integrating circuit that integrates a switching signal from the signal generating means at a point where the signal integrated by the integrating circuit exceeds a first level; and a constant voltage element that becomes conductive when the integrated signal is at a second level higher than the first level, and generates a second switching signal in a region where the integrated signal exceeds the second level. a horizontal oscillation circuit whose oscillation frequency is switched by the first switching signal; and a horizontal output circuit whose circuit constant is switched by the second switching signal. It is a circuit.

(Operation) The present invention integrates the switching signal from the signal generating means in an integrating circuit, and in the regions where the integrated signal exceeds the first and second levels, the first
A second switching signal is generated, the horizontal oscillation frequency is switched by the first switching signal, and the circuit constant of the horizontal output circuit is switched by the second switching signal. By generating the switching signals using the output of a common integrating circuit, the mutual switching timings can be ideally shifted.

(Example) The present invention will be described below based on the example shown in the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the horizontal deflection circuit of the present invention. The embodiment shown in this figure is
This circuit has a configuration in which an integrating circuit of a resistor 15 and a capacitor 16 and a Zener diode 17 are added to the circuit shown in the figure, and the same parts as in FIG. 3 are given the same reference numerals and will be explained.

In FIG. 1, changeover switch 1 is connected to voltage source V ₁
This is a switch for generating a frequency switching signal A by selectively switching between contact a, which is set to a high level potential of the ground voltage, and contact b, which is set to a low level potential of the ground voltage. The integrated signal B is supplied to the integrating circuit of the capacitor 16 and obtained at both ends of the capacitor 16, and is applied to the oscillation frequency switching circuit 2, while being applied to the relay circuit of the horizontal output circuit 5 through the Zener diode 17. The oscillation frequency switching circuit 2 inputs the integrated signal B to the base of the transistor _Q1 via the resistor _R1 ,
The emitter of transistor _Q1 is connected to the ground point,
Resistors R ₂ and R 3 are connected in series between the collector of transistor Q ₁ and the DC voltage source V ₂ , and the connection point of resistors R ₂ and _{R 3 is} connected to the base of transistor Q _{2 .} Connect the emitter to the voltage source V ₂ ,
A resistor _R4 is connected between the emitter and collector of the transistor _Q2 , and the collector of the transistor _Q2 is connected to the ground point via a resistor _R5 .
The configuration is such that the oscillation frequency switching signal is taken out from the collector of _Q2 . Then, the oscillation frequency switching signal is guided to the oscillation frequency adjustment volume VR, which has a resistor _R5 connected in parallel, and from its sliding point, the resistor _R6
and is added to the horizontal oscillation circuit 3 through the integrating circuit of capacitor _C1 . The horizontal oscillation circuit 3 is composed of a well-known multivibrator type oscillation circuit using, for example, two emitter-coupled transistors, and its horizontal oscillation output is amplified by a horizontal drive circuit 4 and then amplified by a horizontal output transistor 7 of a horizontal output circuit 5.
input to the base of The horizontal output circuit 5 includes a horizontal output transistor 7, a damper diode 8, resonance capacitors 9 and 10, and horizontal amplitude coils 11 and 1.
2. Consists of a horizontal deflection coil 13 and an S-shaped correction capacitor 14, one end of the flyback transformer FBT is connected to the collector of the horizontal output transistor 7, and one end of the resonant capacitor 9 or both ends of the horizontal amplitude coil 11 is connected to the collector of the horizontal output transistor 7. One side is short-circuited according to the switching operation of the relay 6. relay 6
has one end of its drive winding connected to the voltage source V ₃ , the other end of the winding connected to the ground point via the collector-emitter path of transistor Q ₃ , and the base of transistor Q ₃ connected to the above integral Signal B is applied via Zener diode 17 and resistor _R6 .

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to the waveform diagram shown in FIG. Figure 2 shows the waveforms of switching signals in each part of the circuit, and A indicates switch 1.
B shows a signal obtained by integrating signal A with an integrating circuit consisting of a resistor 15 and a capacitor 16, and C shows an integral signal B integrated by a Zener diode 1.
7, D indicates a signal obtained at the collector of transistor Q ₁ of oscillation frequency switching circuit 2, which provides the switching timing of horizontal oscillation circuit 3, and E indicates the switching signal of relay 6. This provides the switching timing of the horizontal output circuit 5. That is, signal A rises to a high level potential V ₁ when switch 1 is switched to contact a, and falls to a low level potential when switch 1 is switched to contact b. The integrated signal B has a signal waveform with gentle rises and falls. Signal D is generated at the timing when signal B exceeds the forward voltage V _BE between the base and emitter of transistor Q ₁ , and signal C is generated at the timing when the Zener voltage V _Z of Zener diode 17 _is exceeded. It is set to exceed the base-emitter forward voltage V _BE of ₃ .
Therefore, the timing of signal E is similar to the timing of signal C. However, when the signal A changes from a low level potential to a high level potential and the operating state switches to the higher frequency side, the signal D
Since the signal E changes faster than the signal E, the horizontal oscillation circuit 3 switches before the horizontal output circuit 5, and the flyback pulse of the horizontal output circuit 5 once becomes small, then reaches a steady value and becomes abnormally high. There is no. On the other hand, when signal A changes from high-level potential to low-level potential and the operating state switches to a lower frequency, signal E changes faster than signal D, and horizontal output circuit 5 causes horizontal oscillation. circuit 3
Since the switching occurs earlier, the flyback pulse of the horizontal output circuit 5 becomes smaller and then reaches a steady value, thereby preventing it from becoming abnormally high. In this way, two switching signals with different timings are obtained by the circuit using the integrating circuit and the diode, and the order in which the circuits are switched between the horizontal oscillation circuit 3 and the horizontal output circuit 5 is different from that of the conventional circuit. It is possible to replace them and prevent an increase in flyback pulses.

Although the above embodiment shows a circuit configuration using a Zener diode, a diode may be used instead of the Zener diode. That is, the timing of horizontal oscillation switching and the timing of horizontal output switching can be set to arbitrary values by selecting the integration time constant of the integrating circuit and the conduction voltage of the diode.

[Effects of the invention] As described above, according to the invention, when switching the horizontal scanning frequency, it is possible to prevent the flyback pulse of the horizontal output circuit from becoming abnormally high. Moreover, since the first and second switching signals use the output of a common integrating circuit, the timing of generation of the two switching signals can be accurate, and the circuit configuration can be simplified.

Therefore, deterioration or destruction of the horizontal output transistor can be reliably avoided, and a highly reliable horizontal deflection circuit can be provided.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram showing one embodiment of the horizontal deflection circuit of the present invention, Figure 2 is a waveform diagram explaining the circuit operation of Figure 1, and Figure 3 is a circuit configuration diagram of a conventional horizontal deflection circuit. be. DESCRIPTION OF SYMBOLS 1...Switchover switch, 2...Oscillation frequency switching circuit, 3...Horizontal oscillation circuit, 4...Horizontal drive circuit, 5...Horizontal output circuit, 6...Relay, 15...
...Resistor, 16...Capacitor, 17...Zena diode.

Claims (1)

[Claims for Utility Model Registration] In response to signal inputs with different horizontal scanning frequencies,
a signal generating means for generating a switching signal of a high or low level; an integrating circuit for integrating the switching signal from the signal generating means with a predetermined time constant; and a signal integrated by the integrating circuit having a first level. means for generating a first switching signal in a region exceeding the integration circuit; and a constant voltage element that becomes conductive when the signal integrated by the integration circuit is at a second level higher than the first level, a horizontal oscillation circuit whose oscillation frequency is switched by the first switching signal; and a horizontal oscillation circuit whose oscillation frequency is switched by the first switching signal. A horizontal deflection circuit comprising a horizontal output circuit whose circuit constants are switched.