JPH06101674B2 - Parabolic wave generation circuit - Google Patents

Description

The present invention relates to a parabola wave (quadratic curve) generating circuit used in a deflection circuit of a projection TV receiver or a TV receiver using a large-sized picture tube. Is.

(B) Prior Art A parabolic wave generating circuit capable of generating a parabolic wave is disclosed in Japanese Patent Laid-Open No. 61-125217. FIG. 2 is a circuit diagram showing the parabolic wave generation circuit described in FIG. 1 of the above publication, and includes a switch (1) which opens and closes in response to a vertical trigger pulse, a constant current source (2), and the constant current. Source (2)
A capacitor (3) that is charged according to a constant current from
It is composed of an integrating circuit (4) for integrating a signal generated at the upper end A of the capacitor (3) and an output terminal (5). When a vertical drive pulse as shown in FIG. 3 (a) is applied to the switch (1), the switch (1) is opened and closed accordingly, and a sawtooth wave as shown in FIG. can get.

Therefore, if the signal shown in FIG. 3B is integrated by the integrating circuit (4), a parabolic wave can be obtained at the output terminal (5).

By the way, as the integrating circuit of FIG. 2, an integrating circuit using a differential amplifier circuit is generally used, and the reference voltage thereof is the third
Average DC level of the signal in Figure (b) (a in Figure 3 (b))
Is set to. However, since the center time t ₁ of the sawtooth wave in FIG. 3B is later than the time t ₂ at which the average DC level and the sawtooth wave cross, the charge / discharge of the capacitor built in the integrating circuit is performed. There is a problem in that the time does not match, and the time at the center of the sawtooth wave does not match the time at the center of the parabolic wave. Then, what solved such a problem is described in FIG. 3 of the said publication.

FIG. 5 is a circuit diagram showing a parabolic wave generation circuit described in FIG. 3 of the above publication, which includes a first switch (1) which opens and closes in response to a vertical trigger pulse, a constant current source (2), A capacitor (3) charged according to the constant current from the constant current source (2), a coupling capacitor (4), and an integrating circuit ( 5 )
And an output terminal (6) and a second switch (7) to obtain a parabolic wave at the output terminal (6). When a vertical trigger pulse such as that shown in FIG. 6A is applied to the first and second switches (1) and (7), the first switch ( 1) is opened and the second switch (7) is closed. Then, the capacitor (3) is charged, and the voltage at the upper end A of the capacitor (3) rises as shown in FIG. 6 (b). Further, since the first switch (1) is closed and the second switch (7) is opened during the "H" level period of FIG. 6 (a), the consensus sensor (3) is discharged and its upper end is discharged. The voltage of A drops rapidly as shown in FIG. Since the voltage of the terminal (8) is at the ground level while the second switch (7) is open, a sawtooth wave as shown in FIG. 6 (c) is generated at the terminal (8). Then, the signal of FIG. 6 (c) is integrated by the integrator circuit ( 5 ). At that time, the signal waveform of FIG. 6 (c) has an upper area and a lower area with respect to the ground level. Since they are equal, a parabolic wave with good symmetry can be obtained at the output terminal (6) as shown in FIG.

(C) Problem to be Solved by the Invention However, the circuit of FIG. 5 requires the coupling capacitor (4) and cannot be constructed as a direct connection type, which is not suitable for use in an IC. Further, since the second switch (7) is directly inserted in the signal path, noise is generated during switching, which is a problem.

(D) Means for Solving the Problems The present invention has been made in view of the above points, and a sawtooth wave creating circuit that creates a sawtooth wave according to a vertical trigger pulse, and the sawtooth wave creating circuit. The output of the peak detection circuit is composed of a differential type integration circuit that integrates the output sawtooth wave to generate a parabolic wave, and a peak detection circuit that peak-detects the output sawtooth wave of the sawtooth wave generation circuit. The reference voltage of the integrating circuit is set according to the voltage.

(E) Action According to the present invention, the sawtooth wave is subjected to peak detection, and the voltage corresponding to the peak detection output is used as the reference voltage of the integrating circuit. Therefore, the center time of the sawtooth wave and the center of the parabolic wave are detected. It is possible to always match the time.

(F) Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. (6) shows a control transistor (8) to which a vertical trigger pulse from an input terminal (7) is applied to the base, and a constant transistor. A sawtooth wave generation circuit including a charge / discharge capacitor (10) supplied with a constant current from a current source (9), (11) a first level shift circuit for level shifting the sawtooth wave generated at a point B, ( 12) is a second level shift circuit for further level shifting the level-shifted sawtooth wave from the first level shift circuit (11), and (13) is a first level shift circuit (6) together with a transistor (23). A capacitor for peak-detecting the sawtooth wave from (14), a third level shift circuit (14) for level shifting the sawtooth wave, and (15) a third level shift circuit incorporated in the third level shift circuit (14). From 1st and 2nd resistors (16) and (17) That the voltage dividing circuit, and (18) is a differential amplifier circuit (19), an output terminal and the negative input terminal of the differential amplifier circuit (19) - and a capacitor connected between the (20), () An integrating circuit is composed of a resistor (20) having one end connected to the capacitor (20).

Next, the operation will be described. When a vertical trigger pulse as shown in FIG. 4 (a) is applied to the input terminal (7), the control transistor (8) is turned off during the "L" level period of the vertical trigger pulse, so that the constant current source ( The constant current from 9) flows into the charging / discharging capacitor (10), and the voltage at the upper end B of the charging / discharging capacitor (10) gradually rises. Further, since the control transistor (8) is turned on during the “H” level period of the vertical trigger pulse, the charge / discharge capacitor (1
0) discharges rapidly. Therefore, a sawtooth wave as shown in FIG. 4B is obtained at the point B, and the first level shift circuit (11) shifts the level by + 4V _BE (where V _BE is the forward voltage of the PN junction). The level-shifted sawtooth wave is
It is applied to the base of the transistor (22) in the level shift circuit (12) and to the base of the transistor (23). Since the peak detection capacitor (13) is connected to the emitter of the transistor (23),
The applied sawtooth wave is subjected to peak detection and converted into a DC voltage. Here, assuming that the maximum amplitude of the sawtooth wave at the point B is V _S , the voltage V _{(C) at the} point C becomes V _(C) = V _S + 3V _BE ………… (1), and Fig. 4 ( C) It is represented as the one-dot chain line C.

Also, at point D, which is the emitter of the transistor (22), -V
_{A BE-} level-shifted sawtooth wave is obtained, and the maximum value V _(D) max of the amplitude of the sawtooth wave is V _(D) max = V _S + 3V _BE ... (2), and the minimum value V _(D) min becomes V _(D) min = 3V _BE …………… (3) and becomes like the solid line D in Fig. 4 (c).

The above-mentioned voltage obtained at the point C is − in the transistor (24).
After the V _BE level shift, it is divided by the voltage dividing circuit (15). When the resistance values of the first and second resistors (16) and (17) constituting the voltage dividing circuit (15) are set equal, the voltage V _{(E) at the} point E becomes V _(E) = 1 / 2V _S + 2V _BE …………… (4), which is as shown by the solid line E in Fig. 4 (c). The voltage V
_{Since (E)} is further level-shifted by the transistor (25), the voltage V _{(F) at} point F becomes V _(F) = 1 / 2V _S + V _BE …………… (5) and Fig. 4 (C). It becomes like the solid line F.

On the other hand, the sawtooth wave obtained at the point D is shifted by -2V _BE level by the transistors (26) and (27), so that the voltage V at the point G is
Maximum value V _(G) max of _(G) is _{V (G) max = V S} + V BE ............... (6) , and the minimum value V _(G) min is _{V (G) min = V BE} ...... (7), which is shown as a solid line G in FIG.

Here, as is clear from the equations (5), (6) and (7), the solid line F in FIG. 4 (c) is exactly 1/2 of the amplitude of the dotted line G.

The sawtooth wave G of FIG. 4 (C) generated at the point G is applied to the negative input terminal (−) of the integrating circuit ( 18 ), and the voltage F of FIG. Applied to the positive input terminal (+). Therefore, in the period T ₁ of FIG. 4C, a current flows in the direction of the capacitor (20) forming the integrating circuit ( 18 ) to charge the capacitor (20), and in the period T ₂ , the above The capacitor (20) is discharged. Further, in the period T ₃ of FIG. 4C, the switch (28) is closed in response to the vertical trigger pulse of FIG. 4A, so that the integration operation is stopped. The slope of the sawtooth wave G in FIG. 4C is constant, and the voltage at the positive input terminal (+) of the differential amplifier circuit (19) is
Since it is half the amplitude of the sawtooth wave, the capacitor (2
The charge and discharge amount of 0) can be made the same.

Therefore, at the output terminal (29) of the integrating circuit ( 18 ), as shown in FIG. 4 (d), it is possible to obtain a parabolic wave whose peak coincides with time t when the capacitor (20) switches from charging to discharging. .

(G) Effect of the Invention As described above, according to the present invention, the central times of the sawtooth wave and the parabolic wave can be made coincident with each other, so that a parabolic wave with good symmetry can be created.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional parabolic wave generating circuit, and FIGS. 3 (a) and 3 (b) are for explaining FIG. Waveform diagrams of FIGS. 4A to 4D are waveform diagrams for use in the description of FIG.
FIG. 5 is a circuit diagram showing a conventional parabolic wave generating circuit, and FIGS. 6 (a) to 6 (d) are waveform diagrams for explanation of FIG. (6) ... Sawtooth wave generation circuit, (11) ... First level shift circuit, (12) ... Second level shift circuit, (13) ...
Capacitor for detection, (14) …… 3rd level shift circuit, ( 18 ) …… Integrator circuit.

Claims (3)

[Claims] 1. A sawtooth wave creating circuit for creating a sawtooth wave in response to a vertical trigger pulse, and a positive input terminal, a negative input terminal and an output terminal, the negative input terminal and the output terminal. A differential type integration which has a capacitor between and the negative input terminal is connected to the sawtooth wave forming circuit via a resistor, and integrates the output sawtooth wave of the sawtooth wave forming circuit to generate a parabolic wave. And a peak detection circuit for peak-detecting the output sawtooth wave of the sawtooth wave generation circuit, and applying the output voltage of the peak detection circuit to the positive input terminal of the differential type integration circuit. Parabolic wave generation circuit characterized by doing so. 2. The parabolic wave generator according to claim 1, further comprising a voltage dividing circuit for dividing the output voltage of the peak detection circuit into half and applying the divided voltage to the integrating circuit as a reference voltage. circuit. 3. A sawtooth wave creating circuit for creating a sawtooth wave in response to a vertical trigger pulse, a first level shift circuit for level shifting the output sawtooth wave of the sawtooth wave creating circuit, and the first level. A second level shift circuit for level-shifting the output sawtooth wave of the shift circuit, a positive input terminal, a negative input terminal and an output terminal, and a capacitor between the negative input terminal and the output terminal A differential type integrating circuit having a negative input terminal connected to the second level shift circuit via a resistor to integrate a sawtooth wave output from the second level shift circuit to generate a parabolic wave; A peak detection circuit for peak-detecting the output sawtooth wave of the level shift circuit; and a third level shift circuit for dividing and level-shifting the output voltage of the peak detection circuit. Parabolic wave generating circuit, characterized in that the output voltage of the road was to be applied to the positive input terminal of the integrating circuit of the differential.