JPH0249059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synchronous oscillation device that performs synchronous oscillation not only at a free-running oscillation frequency lower than the synchronization signal frequency but also at a higher free-running oscillation frequency range.

A synchronous oscillation device that synchronizes the period of oscillation and the period of the synchronization signal by direct control using a synchronization signal is used in the vertical deflection circuit of a television receiver or the oscillation circuit of a power supply circuit. This principle will be briefly explained using the circuit diagram and waveform diagram shown in FIG. FIG. 1A shows a blocking oscillation device which applies a negative polarity synchronization signal to one input terminal as an example of a synchronous oscillation device. A shows the synchronization signal waveform, and C shows the base voltage waveform of transistor _Tr1 . As is clear from the waveform diagrams in Figure 1 A and C, when oscillation occurs, the base voltage momentarily becomes a negative potential, but due to the base current, the capacitor _C1 is suddenly charged, the base becomes a positive potential, and the oscillation stops. . This positive potential is discharged at a speed determined by the time constant of the circuit shown in FIG. 1A, but when it returns to the limit point of oscillation, oscillation occurs again. Shortly before the base voltage returns to the oscillation start potential, if the negative synchronization signal shown in Figure 1A is added, the oscillation start limit is exceeded at this point due to the superposition of the base voltage and the synchronization signal, so the synchronization signal is added. As shown by the dotted line in FIG. 1C, the oscillation period coincides with the synchronization signal period. For this reason, in the synchronous blocking oscillator, the free-running oscillation period of the blocking oscillation circuit is made slightly larger than the period of the synchronizing signal, so that the synchronizing signal always enters earlier.

As described above, in the case of a conventional synchronous oscillator, the free-running oscillation frequency must be set to a lower frequency than the synchronous signal frequency, so the pull-in frequency of the synchronous oscillator is limited. In addition, when attempting to widen the pull-in frequency, an automatic frequency control circuit is required, which has the disadvantage of complicating the circuit.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks and provides a synchronous oscillation device capable of synchronous oscillation even when the free-running oscillation frequency is higher than the frequency of the synchronous signal.

FIG. 2 shows a circuit diagram of an embodiment of the synchronous oscillation device of the present invention, and FIG. 3 shows a waveform diagram of main parts. In Figure 2, 1 is an input terminal, 2 is a monostable multivibrator circuit, and 3 is a silicon controlled switch element (SCS) with excellent voltage reduction, temperature, and synchronization characteristics.
An anode grounded oscillation circuit using Tr ₂ , 4 an output terminal, +B ₁ and +B ₂ power supplies. Add the synchronizing signal shown in Figure 3 (a) to the input terminal in Figure 2 (1), determine the time constant with capacitor C ₁ and resistor R ₁ in the monostable multivibrator circuit shown in Figure 2 (2), and generate a pulse as shown in Figure 3 (a). A wide horizontal synchronization signal a is created. This wide pulse width horizontal synchronizing signal is applied to the anode grounded oscillator circuit of FIG. 2 through a series resistor _R5 . The synchronizing signal b in Figure 3A is differentiated by the bias resistors R ₂ and R ₃ and the coupling capacitor C ₂ to become Figure 3C, which is applied to the base of Tr ₂ (SCS). 3
When a power supply voltage +B ₂ is applied to the anode grounded oscillator circuit of , the base current of the NPN transistor starts flowing through the resistor R ₁ , and its collector current also flows; . For this reason
Both currents increase rapidly as the base current of the NPN transistor increases which in turn increases the collector current which in turn increases the current of the PNP transistor. At this time capacitor C ₃
is charged through the resistor _R6 , so the emitter voltage _Ve2 reaches nearly + _B2 as shown in Figure 3D.

When the NPN transistor is operating, the base potential is almost the same as the emitter potential, so the base potential also rises and reaches + _B2 . Therefore, the collector-emitter voltage of both transistors becomes zero, and since no base current flows, both transistors are cut off at the same time. Therefore, the current charged in the capacitor _C3 is discharged through the resistor _R4 , and the emitter voltage _Ve2 begins to decrease. This circuit repeats the same operation in this way, so the resistance
A sawtooth voltage like Ve ₂ in Figure 3D is generated across R ₄ .

The oscillation frequency is determined by the resistor _R4 , capacitor _C3 time constant, and base potential + _V1 .

In this example, when the oscillation circuit is operated at a free-running oscillation frequency lower than the synchronization signal frequency, Tr ₂ (SCS)
By applying a positive synchronizing signal as shown in Figure 3A to the base of , the NPN transistor is operated before the emitter potential Ve ₂ becomes below the base potential.
The oscillation frequency is synchronized with the synchronization signal.

Next, it will be explained in detail with reference to FIG. 4 that in this embodiment, the oscillation circuit performs synchronous oscillation not only at a free-running oscillation frequency lower than the synchronizing signal frequency but also at a higher free-running oscillation frequency.

Figure 4A shows the base voltage waveform _Vb0 when the narrow synchronization signal with the pulse width shown in Figure 4A is differentiated and applied to the base of Tr ₂ (SCS). t _H1 is one period of the synchronization signal, and t _H2 is one period of free-running oscillation of the oscillation circuit. While adding the base voltage V _b0 ,
When the free-running oscillation frequency (1/t _H2 ) is set higher than the synchronizing signal frequency (1/t _H1 ) and the operation is performed, Tr ₂ (SCS) is initially activated at the rising edge of the positive differential signal of the base voltage Vb.
turns on and the emitter voltage Ve ₀ reaches the power supply voltage +B ₂ . After that, Tr ₂ (SCS) turns OFF, and C ₃ × R ₄
The emitter voltage Ve ₀ is discharged with a time constant of , and the emitter voltage Ve 0 gradually decreases, and when the emitter voltage Ve ₀ becomes 0.7 [V] lower than the base voltage Vb ₀ , the operation of turning on Tr ₂ is repeated. However, while the emitter voltage Ve ₀ is decreasing
If there is a differential signal of Vb, Tr ₂ will turn on at that point, so a sawtooth voltage oscillated in synchronization with synchronization signal A cannot be obtained. If synchronous oscillation is performed using a synchronizing signal with a narrow pulse width as shown in FIG.

FIG. 4C shows the waveform of a synchronizing signal with a wide pulse width, and FIG. 4D shows the base voltage waveform Vb when this is differentiated and applied to the base of Tr ₂ (SCS). Free-running oscillation frequency (1/t _H2 ) by adding the above base voltage Vb
When it is operated at higher than the synchronous oscillation frequency (1/t _H1 ), Tr ₂ (SCS) turns ON at the rising edge of the positive differential signal of the leading edge pulse of the base potential Vb, and the emitter voltage Ve ₀ becomes the power supply voltage. +B reaches up to ₂ . After that, Tr ₂ (SCS) turns OFF and begins to discharge with a time constant of C ₃ × R ₄ , which is an oscillation frequency higher than the synchronizing signal frequency, and the emitter voltage Ve ₀ gradually decreases until the emitter voltage Ve ₀ becomes the base. 0.7 from voltage Vb
When [V] becomes low, Tr ₂ (SCS) is turned on and the above operation is repeated. However, by repeating the above operation, the ON point of Tr ₂ moves away from the positive differential signal of the leading edge pulse and approaches the negative differential signal of the trailing edge pulse. Then the emitter voltage Ve ₀
If the point t 1, at which point t ₁ is expected to be 0.7 [V] lower than the base potential V ₁ [V], falls within the period T of the negative differential signal, the emitter voltage Ve ₀ will be lower than the base potential V ₁ [V].
At point t ₁ , which is expected to be 0.7 [V] lower than Tr ₂
(SCS) is supposed to turn ON and repeat the above operation, but the actual base potential is the waveform of Vb (Fig. 4E), which is a differential signal superimposed on _V1 , and during the period T, the base voltage Because the base voltage is pulled more negative than V ₁ due to the negative polarity differential signal when the trailing edge pulse of waveform Vb recovers, at the predicted t ₁ point,
Tr ₂ (SCS) does not turn on, and Tr ₂ (SCS) turns on at point t ₂ where the negative polarity differential signal rises by 0.7 [V] above the emitter voltage Ve.
When turned on, the emitter voltage Ve reaches the power supply voltage + _B2 . Here, since the change in emitter voltage is fixed to the period of the synchronization signal, the sign is Ve. As mentioned above, when the point at which the emitter voltage Ve ₀ should first become 0.7 [V] lower than the base potential V ₁ [V] is within the period T of the negative differential signal of the base voltage waveform Vb, the base Since the base voltage is pulled negative by the negative differential signal when the trailing edge pulse of the voltage waveform Vb recovers, the point t ₁ where the emitter voltage Ve ₀ should become 0.7 [V] lower than the base potential V ₁ [V]
Tr ₂ (SCS) does not turn ON at point t _{2 where} the negative polarity differential signal rises by 0.7 [V] above the emitter voltage Ve.
turns on and the emitter voltage Ve reaches the power supply voltage + _B2 . After that, Tr ₂ (SCS) is turned off and discharge begins with a time constant of C ₃ × R ₄ , and the emitter voltage gradually decreases, but the emitter voltage becomes lower than the base potential.
Since the point t ₁ that should be 0.7 [V] lower than V ₁ [V] is within the period T of the negative polarity differential signal, the above operation is repeated and one cycle of the emitter voltage (oscillation output) is The periods are t _H2 , t _H3 , t _H1 (t _H2 > t _H3 > t _H1 )
After that, the period changes to t _H1 .
Therefore, since the ON point of Tr ₂ (SCS) is always the t ₂ point,
An emitter voltage Ve (sawtooth voltage) oscillated in synchronization with the synchronization signal U is obtained.

In this example, a monostable multivibrator is used to differentiate the synchronization signal with a wider pulse width.
A grounded anode oscillation circuit using SCS is added to the base. In other words, by setting the voltage level at the time of recovery of the trailing edge pulse of the differential signal obtained by differentiating the synchronization signal with a wide pulse width to reach the potential of the oscillation start point of the oscillation circuit, an automatic signal frequency lower than the synchronization signal frequency can be set. Since synchronous oscillation is performed not only at a running oscillation frequency but also at a high free-running oscillation frequency, a wide frequency band can be obtained for synchronous oscillation.

Another method for obtaining the above effect is to use an AFC (free running oscillation frequency control) circuit, but the circuit configuration is simpler and lower cost than this method.

If the synchronous oscillation device of the above embodiment is used in the power supply section of a television receiver, noise will not be noticeable on the screen, and at the same time, the free-running oscillation frequency can be set not only to a value slightly lower than the synchronous signal frequency, but also to a value slightly higher. can also be set, so even if the synchronization signal is lost, there is little effect on the screen, which is an advantage. Furthermore, if the free-running oscillation frequency and the synchronization signal frequency are made almost equal and installed in the receiver, even if the free-running oscillation frequency fluctuates up and down due to temperature changes or aging, the oscillation output can always be accurately synchronized. It is possible to increase frequency accuracy.

As described above, according to the present invention, it is possible to set a wide frequency band for synchronous oscillation, and to provide a very practical synchronous oscillation device.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram and main part waveform diagram of a conventional synchronous oscillation device, Fig. 2 is a circuit diagram showing an embodiment of the synchronous oscillation device of the present invention, and Figs. 3 and 4 explain this embodiment. FIG. 1...Input terminal, 2...Monostable multivibrator, 3...Anode grounded oscillation circuit, 4...Output terminal, _R2 , _R3 ...Bias resistance, _C2 ...Coupling capacitor, _C3 ...Capacitor, R ₄
...Emitter resistor, Tr ₂ ...Silicon controlled switch element.

Claims (1)

[Claims] 1 means for inputting a synchronization signal; pulse width control means for controlling the pulse width of the input synchronization signal; differentiating means for differentiating the output of the pulse width control means; oscillation means constituted by a controlled oscillation circuit and whose free-running oscillation frequency is set to a value higher than the frequency of the synchronization signal; and means for inputting the differentiated signal from the differentiation means to the oscillation circuit. The pulse width of the pulse width control means is made smaller than the period of the free-running oscillation frequency, and the voltage level at the time of recovery of the trailing edge pulse of the differentiating means reaches the potential at the oscillation start point of the oscillation circuit. A synchronous oscillation device characterized in that it is set to