JP2589486Y2 - Dynamic focus circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

This invention relates to a cathode ray tube (CRT).
The present invention relates to a dynamic focus circuit capable of satisfactorily focusing a beam over the entire surface of a fluorescent screen.

[0002]

2. Description of the Related Art In a CRT, since the curvature radius of a screen (fluorescent screen) and the deflection radius of a deflection yoke are different, if the focus is adjusted optimally at the center of the screen, the optimal focus can be obtained at the periphery of the screen. Absent.
Therefore, a dynamic focus technique that dynamically changes the focusing voltage in synchronization with the deflection so that the beam is focused around the CRT is adopted.

FIG. 4 is a graph showing the optimum focus voltage of each part of the screen. This graph shows a 17-inch CRT
2 shows the focus voltage Ho in the horizontal direction and the focus voltage Ve in the vertical direction when are arranged in a vertical type (portrait mode). The horizontal axis represents the distance (unit: mm) when the center of the screen is set to 0, and the vertical axis represents the focus voltage (unit: V). In order to obtain an optimum focus with this CRT, it is necessary to change the focus voltage in a parabolic manner over a voltage range of about 250 V for horizontal deflection and about 350 V for vertical deflection.

[0004] The center of deflection of the CRT often deviates from the center of the screen. If there is any deviation,
It is necessary to correct the phase of the parabolic focus voltage according to the vertical shift. FIG. 5 is a waveform diagram of the focus voltage when the center of deflection coincides with the center of the screen, and FIG. 6 is a waveform diagram of the focus voltage when a deviation occurs. When the center A of the screen (the screen of the CRT) coincides with the center B of the deflection, as shown in FIG. 5A, the horizontal parabola voltage and the vertical parabola voltage have symmetrical waveforms, and the applied dynamic focus voltage 5B is a waveform of FIG. 5B in which each parabola voltage is mixed. As shown in FIG. 6A, when the center B of deflection is shifted from the center A of the screen, the waveform of the applied dynamic focus voltage is as shown in FIG. 6B.

FIG. 7 is a circuit diagram of a conventional dynamic focus circuit. The conventional dynamic focus circuit 100 converts a horizontal pulse (horizontal synchronization signal) into a phase shift circuit 1.
01 generates a sawtooth wave 102a in a horizontal sawtooth wave generating circuit 102 based on the horizontal pulse signal 101a obtained by phase adjustment, and a parabolic wave generating circuit 1 based on the sawtooth wave 102a.
While the horizontal parabolic voltage 103a whose phase has been adjusted is generated from the vertical parabolic voltage 103, the vertical pulse (vertical synchronizing signal) is also adjusted through the phase shift circuit 104, the sawtooth wave generating circuit 105, and the parabolic wave generating circuit 106. 1
06a is generated in the same manner, and the combined parabolic voltages 103a and 106a are added by the mixer 107 to generate a combined parabolic voltage 107a, which is then output to the focus voltage output circuit 1
08 and the dynamic focus voltage output 108
a.

[0006]

[Problems to be solved by the invention] Phase shift circuits 101 and 10
Normally, a one-shot multi-circuit is used for 4; however, in order to advance the phase, the output pulse width of the one-shot multi-circuit needs to be close to one cycle of the vertical pulse (about 14 ms). However, in a one-shot multi-circuit using a time constant determined by the product of the resistance and the capacitor, the output pulse width changes depending on the temperature, so that it is difficult to obtain a stable dynamic focus voltage output 108a. If a digital frequency dividing one-shot multi-circuit or the like is used, the circuit configuration becomes complicated.

The mixer 107 is generally constructed using an operational amplifier IC or the like.
Due to the limitation of the maximum operating power supply voltage such as the above or the supply power supply voltage (for example, 12 V) to parts other than the high-voltage circuit section, the combined parabolic voltage 107a output from the mixer 107 is several volts.
pp (about 8 Vp-p). To obtain a necessary focus voltage of about 600 Vp-p, the focus voltage output circuit 1
08 needs to be increased. Generally, the performance of the amplifier circuit is determined by the product of the gain and the frequency band. Therefore, if the gain of the focus voltage output circuit 108 is set to be large, the frequency characteristics will be deteriorated. For this reason, a phase delay or the like occurs in the output signal, and an accurate dynamic focus correction parabolic waveform cannot be generated.

The present invention has been made to solve such a problem, and an object thereof is to provide a dynamic focus circuit in which the temperature characteristics of a phase shift circuit are stable and the frequency characteristics of a focus voltage output circuit are good. is there.

[0009]

In order to solve the above-mentioned problems, a dynamic focus circuit according to the present invention comprises a sawtooth wave generating circuit for generating a sawtooth signal based on a synchronization signal, and a parabolic waveform synchronized with the sawtooth signal. A parabolic wave generating circuit for generating a signal; a variable amplifying circuit for generating a phase correcting sawtooth signal for waveform processing of the sawtooth signal to adjust the phase of the parabolic waveform signal; and a phase correcting sawtooth signal. Parabolic waveform signal phase-adjusted by mixing with parabolic waveform signal
And a focus voltage output circuit for generating a focus voltage output based on the mixed output of the mixer.

Further , the focus voltage output circuit includes a first transistor for amplifying a mixed output output from the mixer, and a second transistor connected in parallel to the first transistor.
A third transistor, a second transistor amplifies a phase adjustment sawtooth signal for adjusting the phase of another system parabolic wave signal, and a third transistor converts another system parabolic wave signal. amplified, and configured to retrieve the been focusing voltage output synthesized via a fourth transistor of the cascode connected to each of these transistors.

[0011]

The sawtooth signal generation circuit generates a sawtooth signal based on the synchronizing signal, and the parabola signal generation circuit generates a parabola signal synchronizing with the sawtooth signal. The variable amplifier circuit receives the sawtooth signal and generates a phase-correcting sawtooth signal, which is a signal component for adjusting the phase of the parabolic wave signal. Since the mixer mixes the parabolic wave signal and the sawtooth wave signal for phase correction, a parabolic signal whose phase has been corrected is output. Therefore, by generating a focus voltage based on this mixed output, dynamic focus adjustment with stable temperature characteristics and good frequency characteristics can be performed. Further, by adjusting the amplification gain of the variable amplifier circuit, the phase amount of the parabolic waveform signal can be continuously varied.

A first transistor in the focus voltage output circuit amplifies the mixed output, a second transistor amplifies a signal for adjusting the phase of a parabola waveform signal of another system, and a third transistor amplifies a signal for adjusting the phase of the parabolic waveform signal of another system. Amplify the parabola waveform signal of the system. Since the fourth transistor outputs a focus signal obtained by combining the amplified signals, it is possible to extract a signal that has been subjected to phase correction in two directions.

[0013]

1 is an overall block diagram of a dynamic focus circuit according to the present invention, and FIG. 2 is a circuit diagram showing a specific circuit configuration of a variable amplifier circuit. A dynamic focus circuit 1 generates a vertical sawtooth wave signal 2a based on a vertical pulse (vertical synchronization signal).
And a parabolic wave generating circuit 3 for generating a preset parabolic waveform voltage signal 3a in synchronization with the sawtooth wave signal 2a.
A variable amplifying circuit 4 that performs predetermined waveform processing on the sawtooth signal 2a to generate a vertical sawtooth signal 4a, and a mixer 5 that mixes the parabola waveform voltage signal 3a with the vertical sawtooth signal 4a. A horizontal sawtooth wave generating circuit 6 for generating a horizontal sawtooth signal 6a based on a horizontal pulse (horizontal synchronization signal), and performing a predetermined waveform processing on the sawtooth signal 6a to generate a horizontal sawtooth signal 7a. And a focus voltage output circuit 9 that receives the mixed output 5a, the horizontal sawtooth wave signal 7a, and the horizontal parabolic wave signal 8a output from the horizontal parabolic wave generating circuit 8 to generate a focus voltage output FV. .

The horizontal parabolic wave generation circuit 8 includes a horizontal coil L of a deflection yoke, a horizontal S-shaped correction capacitor C7,
It comprises a coupling capacitor C8 and a variable resistor VR2 for adjusting the horizontal parabola amplitude.
Is configured to obtain a parabolic wave-shaped voltage output of about 60 Vp-p at both ends of the S-correction capacitor C7 based on the horizontal deflection current flowing through the capacitor.

The focus voltage output circuit 9 comprises three NPN transistors Q1 and Q
2, Q3, and a common-base NPN transistor Q4 cascode-connected to these transistors Q1 to Q3.
And their peripheral circuits. The focus voltage output circuit 9 includes a mixed output 5a applied to a terminal 9a, a horizontal sawtooth signal 7a applied to a terminal 9b, and a terminal 9a.
The focus voltage output FV is configured to be generated based on the horizontal parabolic wave signal 8a applied to c.

A bias power supply VB is applied to the terminal 9d. The bias power supply VB is supplied to the base of the transistor Q4 and supplies a base bias to each of the transistors Q1 to Q3 via three systems of base bias resistors R1, R2, R3, R4, R5, and R6. The emitters of the transistors Q1 to Q3 are grounded via emitter resistors R7 to R9, respectively.
Emitter peaking capacitors C1 and C2 are connected in parallel with the emitter resistors R8 and R9 of the transistors Q2 and Q3 to correct the frequency characteristics.

The mixed output 5a is supplied to the base of the transistor Q1 via the coupling capacitor C3 and to the horizontal sawtooth signal 7a.
Is connected to the base of the transistor Q2 via the coupling capacitor C4, and the horizontal parabolic wave signal 8a is supplied to the coupling capacitor C4.
5 to the base of the transistor Q3. Then, an output generated at an end of an output resistor R10 connected between the high voltage power supply + Bh and the collector of the transistor Q4 is taken out through a series circuit of a resistor R11 and a capacitor C6. The variable resistor VR1 is for adjusting the static focus.

As shown in FIG. 2, each of the variable amplifier circuits 4, 7
Is composed of voltage dividing resistors 11 and 12 for dividing the sawtooth signals 2a and 6a at a preset fixed voltage dividing ratio, a variable resistor 13 for amplitude adjustment, an operational amplifier 14 and its peripheral circuits. The signals divided by the voltage dividing resistors 11 and 12 are applied to the non-inverting input terminal (+) of the operational amplifier 14 via the coupling capacitor 15. The resistors 16 and 17 are for applying a bias voltage. The signal divided by the variable resistor 13 is applied to the inverting input terminal (−) of the operational amplifier 14 via the coupling capacitor 18 and the input resistor 19. The resistor 20 is for feedback.

FIG. 3 is a waveform diagram showing the relationship between the input and output of the variable amplifier circuit. By adjusting the variable resistor 13 for amplitude adjustment, as shown in FIGS.
A signal amplified at any magnification, positive or negative, and a signal multiplied by 0 are obtained.

Next, the operation principle of the present invention will be described. The parabolic waveform can be represented by a square function shown in Equation 1, and the parabolic waveform advanced by a certain time t1 becomes Equation 2. Since Equation 2 can be expanded as shown in Equation 3, the parabolic waveform advanced by time t1 is obtained by adding the linear function shown in Equation 4 to Equation 1.

[0021]

(Equation 1)

[0022]

(Equation 2)

[0023]

(Equation 3)

[0024]

(Equation 4)

The waveform of the linear function expressed by the equation 4 is a sawtooth wave, and the sawtooth signal can be generated by a simple circuit. However, the slope of the linear function shown in Equation 4 takes a negative or positive value depending on whether the phase is advanced or delayed. That is, it is possible to artificially adjust the phase of the parabolic waveform by adding a sawtooth signal amplified positively or negatively to the parabolic waveform signal.

Next, the operation of the dynamic focus circuit shown in FIGS. 1 and 2 will be described. The vertical sawtooth generation circuit 2 generates a vertical sawtooth signal 2a based on a vertical pulse (synchronization signal) output from a vertical circuit (not shown).
Based on the sawtooth wave signal 2a, the parabola wave generation circuit 3
A vertical parabolic wave signal 3a having an amplitude corresponding to the setting of the amplitude adjusting variable resistor 3b is output.

The amplitude of the sawtooth signal 2a input to the variable amplifier circuit 4 shown in FIG. 2 is adjusted by the variable resistor 13 for adjusting the amplitude, and the inverted input of the operational amplifier 14 is connected via the coupling capacitor 18 and the input resistor 19. Applied to terminal (-). The sawtooth signal 2a is divided by the voltage dividing resistors 11 and 12, and further superimposed on the bias voltage given by the bias resistors 16 and 17 and applied to the non-inverting input terminal (+) of the operational amplifier 14. The sawtooth signal 4 output from the operational amplifier 14 is adjusted by adjusting the amplitude-adjusting variable resistor 13.
a is a number Vp-p (about 8 V
A vertical sawtooth signal (pp) is obtained. This sawtooth signal 4a
Is for adjusting the phase of the parabolic wave signal 3a.

The vertical adjusted sawtooth wave signal 4a and the parabolic wave signal 3a whose amplitude has been adjusted are mixed by the mixer 5, and the mixed output 5a has a pseudo-phase adjusted parabola waveform signal of several Vp-p. Is output.

The horizontal sawtooth generating circuit 6 generates a horizontal sawtooth signal 6a based on a horizontal pulse (synchronous signal) output from a horizontal circuit (not shown). The variable amplifier circuit 7 shown in FIG. 2 outputs a horizontal sawtooth signal 7a for adjusting the phase of the horizontal parabolic wave signal 8a.

The first transistor Q1 in the focus voltage output circuit 9 amplifies the phase-adjusted vertical parabolic wave signal 5a output from the mixer 5, and the second transistor Q2 is output from the variable amplifier circuit 7. The third transistor Q3 amplifies the phase correction signal 7a of the horizontal parabolic wave signal, and the third transistor Q3 amplifies the horizontal parabolic wave signal 8a output from the horizontal parabolic wave generation circuit 8. Since the fourth transistor Q4 takes out the combined output of the transistors Q1 to Q3, the focus voltage output FV whose phase has been adjusted in both the horizontal and vertical directions is taken out.

Note that the focus voltage output circuit 9
Since the transistors Q1 to Q3 amplify the corresponding signals and then combine them, the degree of amplification of each signal can be set individually. Each cascode-connected transistor Q
4, Q2 and Q3 constitute a mixing circuit of the phase adjustment signal of the horizontal parabolic wave signal and the horizontal parabolic wave signal 8a, so that the amplitude generated in the S-shaped correction capacitor 12 is large (about 60 Vp-p). Since the parabola voltage can be used directly, the amplification of this signal can be reduced. Therefore, even when the horizontal scanning period is as high as about 90 KHz, an accurate parabolic wave voltage without a phase delay can be obtained.

[0032]

[Effect of the Invention] As described above, the dynamics of the present invention
The focus circuit generates a sawtooth signal based on the synchronization signal.
The generated sawtooth wave generation circuit and the parameters synchronized with this sawtooth signal
Parabolic wave generation circuit that generates a bora waveform signal
Signal to adjust the phase of the parabolic waveform signal.
A variable amplifier circuit for generating a sawtooth signal for phase correction for
The phase correction sawtooth signal and parabolic waveform signal
A mixer for producing a phase-adjusted parabolic waveform signal;
The focus voltage output is calculated based on the mixing output of this mixer.
With a focus voltage output circuit that generates
By changing the gain of the variable amplifier circuit , the phase of the parabolic wave signal can be continuously adjusted, and the phase adjustment of the parabolic wave signal is only to adjust the gain of the variable amplifier.
The phase of the parabolic wave signal does not fluctuate due to the temperature characteristics of the time constant circuit as in the case of using the conventional phase shift circuit.

Further , the dynamic focus circuit comprises:
Since a transistor for amplifying each signal and a transistor for synthesizing the amplified output are provided, the degree of amplification of each signal can be set individually.

[Brief description of the drawings]

FIG. 1 is an overall block configuration diagram of a dynamic focus circuit according to the present invention.

FIG. 2 is a circuit diagram showing a specific circuit configuration of the variable amplifier circuit according to the present invention.

FIG. 3 is a waveform chart showing a relationship between an input and an output of a variable amplifier circuit.

FIG. 4 is a graph showing an optimum focus voltage of a vertically arranged CRT.

FIG. 5 is a waveform diagram of a focus voltage when the center of deflection coincides with the center of the screen.

FIG. 6 is a waveform diagram of a focus voltage when a deviation occurs between the center of deflection and the center of the screen.

FIG. 7 is a circuit configuration diagram of a conventional dynamic focus circuit.

[Description of Signs] 1 ... Dynamic focus circuit, 2 ... Vertical sawtooth wave generation circuit, 2a ... Vertical sawtooth wave signal, 3 ... (horizontal) parabolic wave generation circuit, 4,7 ... Variable amplifier, 5 ... Mixer, 6 horizontal sawtooth wave generating circuit, 6a horizontal sawtooth wave signal, 8 horizontal parabolic wave generating circuit, 9 focus voltage generating output circuit, Q
1 to Q4: first to fourth NPN transistors, FV:
Focus voltage.

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A 4-114262 (JP, U) JP-A 2-48994 (JP, U) JP-A 62-186561 (JP, U) 49034 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) H04N 3/26

Claims (1)

(57) [Scope of request for utility model registration] 1. A sawtooth wave generating circuit for generating a sawtooth signal based on a synchronization signal, a parabola wave generating circuit for generating a parabola waveform signal synchronized with the sawtooth signal,
A variable amplifier circuit for generating a phase-correcting sawtooth signal for adjusting the phase of the parabolic waveform signal by performing waveform processing ; and mixing the phase-correcting sawtooth signal with the parabolic waveform signal.
And a focus voltage output circuit that generates a focus voltage output based on the mixed output of the mixer , wherein the focus voltage output circuit outputs an output from the mixer. Sa
A first transistor for amplifying the mixed output to be
The second and third transformers connected in parallel to one transistor
A second transistor and a parabolic circuit of another system.
A sawtooth wave signal for phase adjustment to adjust the phase of the
Amplify and use the third transistor for the other system.
Amplifies the parabolic wave signal of
Via a cascode-connected fourth transistor
To extract the combined focus voltage output
A dynamic focus circuit.