JPH01268356A - Multiscanning crt display device - Google Patents

Abstract

PURPOSE:To obtain an oscillation output signal as a continuous signal by constituting a horizontal oscillating circuit of a differential oscillating circuit and applying a voltage corresponding to the horizontal synchronizing signal frequency to the base of one transistor TR. CONSTITUTION:A horizontal oscillating circuit 3 consists of the differential oscillating circuit consisting of first and second TRs 4 and 8, and a voltage corresponding to the horizontal synchronizing signal frequency from a frequency- voltage converting circuit 2 is applied to the base of the first TR 4. Thus, the free-run frequency of the horizontal oscillating circuit is continuously changed, and the circuit is locked to the horizontal synchronizing signal having a wide-range frequency because the output signal of a phase comparing circuit 13 is applied to the base of the second TR 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention is directed to receiving video signals from computers, etc. that generate horizontal synchronizing signals of a higher frequency than horizontal synchronizing signals of normal television broadcasting. This invention relates to a multi-scan CRT display device that can perform

(b) Conventional technology In TV broadcasting using the NTSC system, the horizontal frequency (horizontal synchronization signal frequency) is set at approximately 15.75 kHz, but the output video signal of a high-resolution computer has a horizontal frequency of 20 kHz or more. be. A multi-scan TV receiver capable of receiving such various video signals having different horizontal frequencies with a single receiver is described in Japanese Patent Laid-Open No. 61-242172. According to the multi-scan TV receiver described in the publication, the horizontal frequency is reduced to 20 kHz or less, 20 to 30 kHz, by a frequency-voltage conversion circuit.

It is determined that the frequency is 30 kHz or more, and the time constant of the time constant circuit of the horizontal oscillation circuit is switched according to the determined output. Since each time constant of the time constant circuit has a value corresponding to a free run frequency in each frequency range, the horizontal oscillation circuit can oscillate at a free run frequency that is the center of each frequency range. Therefore, the horizontal oscillation circuit can sufficiently lock even high-frequency horizontal synchronization signals and can receive various video signals.

(c) Problems to be solved by the invention However, if the method described in the above publication is used,
Since the time constant must be switched, there is a problem in that the oscillation output signal becomes discontinuous at the moment of switching. Furthermore, it is necessary to prepare capacitors with different capacities and switch between them, which increases the number of elements. In particular, since the capacitor constituting the time constant circuit is externally attached to an IC (integrated circuit), it is also a problem when integrated into an IC.

(d) Means for Solving the Problems The present invention has been achieved in view of the above points, and includes a phase comparison circuit that performs a phase comparison between a horizontal synchronization signal and a flyback pulse, and an output signal of the phase comparison circuit. a horizontal oscillation circuit whose oscillation frequency is controlled according to the output signal of the smoothing circuit; and a horizontal oscillation circuit for changing the free run frequency of the horizontal oscillation circuit according to a frequency change of the horizontal synchronization signal. In a multi-scan CRT display device comprising a frequency-voltage conversion circuit that generates a control signal, the horizontal oscillation circuit is configured with a differential oscillation circuit having first and second transistors whose emitters are commonly connected, The output signal of the frequency-voltage conversion circuit is applied to the base of the first transistor to adjust the free run frequency, and the output signal of the smoothing circuit is applied to the base of the second transistor to adjust the oscillation frequency. It is characterized by what it does.

(*) Effect According to the present invention, the horizontal oscillation circuit is constituted by a differential oscillation circuit consisting of first and second transistors, and the voltage according to the horizontal synchronizing signal frequency from the frequency and wave number-voltage conversion circuit is applied to the horizontal oscillation circuit. Since the voltage is applied to the base of the first transistor, the free run frequency of the horizontal oscillation circuit can be changed continuously.

Furthermore, since the output signal of the phase comparison circuit is applied to the base of the second transistor, the oscillation frequency can be adjusted.

(F) Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. (1) is an input terminal to which a wide range of horizontal synchronization signals from TV broadcasts and computers are applied; Input terminal (1)
(≦) is a frequency-voltage conversion circuit that generates a voltage according to the frequency of a horizontal synchronization signal from the frequency-voltage conversion circuit (2); a first transistor (4) to which the output voltage is applied to the base; A charging/discharging circuit (2) consisting of a resistor (5) and a capacitor (6) connected in series between (+Vcc) and the ground, the base being connected to the connection midpoint of the resistor (5) and the capacitor (6). , a second transistor (8) whose emitter is connected to the emitter of the first transistor (4), the first and second transistors (4) and (
The frequency-voltage conversion circuit (8) includes a third transistor (9) whose emitter is connected to the common emitter of the third transistor (9), a reference voltage generation circuit (S) for applying a bias to the base of the third transistor (9), etc. (2) is a horizontal oscillation circuit whose free run frequency is controlled according to the output voltage; (11) is a deflection coil (11) according to the output signal of the horizontal oscillation circuit (base);
(13) is a phase comparison circuit that performs a phase comparison between the horizontal synchronizing signal from the input terminal (1) and the flyback pulse from the deflection coil (12); and (14) is the phase comparator circuit (
This is a smoothing circuit that smoothes the error output from 13) and controls the oscillation frequency of the horizontal deflection circuit according to the smoothed DC voltage.

First, the oscillation operation of the horizontal oscillation circuit will be explained.

When the power is turned on, the capacitor (
6) is charged, and the base voltage of the second transistor (8) gradually increases. The base of the third transistor (9) (
The voltage VN at point A) is set so that it is sufficiently higher than the voltage V at the output terminal (point B) of the frequency-voltage conversion circuit (2).
The resistance values of the resistors to the third resistors (15) to (17) are set.

Therefore, immediately after the power is turned on, the first and second transistors (4
) and (8) are turned off, and the third transistor (9> is turned on. When the second transistor (8) is turned off, the transistor (18) is turned off, and the charging/discharging circuit (Z
) is turned off, and the transistor (20) is turned off, which operates as a second switching circuit to switch the output voltage of the reference voltage generation circuit (2).

Then, when the charging of the capacitor (6) progresses and the base voltage of the second transistor (8) exceeds the voltage v, i at point A, the second transistor (8) is turned on and the first and third Transistors (4) and (9) are turned off.

When the second transistor (8) is turned on, the transistor (18) is turned on, and the transistors (19) and (20) are turned on.
) turns on. When the transistor (19) is turned on, the capacitor (6) connects the resistor (21) and the transistor (
19), so that the base voltage of the second transistor (8) gradually decreases.

On the other hand, when the transistor OFF 20) is turned on, the first
And voltages v,' are generated according to the resistance values of the second resistors (15) and (16). The value of the voltage v□′ is the voltage v at point B
It is set to a value smaller than L (VH'< VH). Therefore, even if the base voltage of the second transistor (8) becomes lower than the voltage vH due to discharge, the third transistor (9) remains off. Then, the discharge progresses further and the second
When the base voltage of the transistor (8) reaches the voltage at point B 1 or less, the first transistor (4) turns on and the second transistor (4) turns on.
And the third transistors (8) and (9) are turned off. Then, transistor (18) turns off and transistor (1
9> and (20) are turned off. The transistor (20
) is turned off, the voltage at point A (7) returns to voltage 9, which is the same as the initial state. Furthermore, when the transistor (19) is turned off, the capacitor (6) stops discharging. As a result, the state is the same as the initial state, the capacitor (6) is charged again by the current from the resistor (5), and this operation can be repeated thereafter.

Therefore, at the terminal (22) of the horizontal oscillation circuit (good), it is possible to obtain an oscillating sawtooth waveform whose upper limit is defined as the voltage 8 and the lower limit is defined as the voltage vL, as shown by the solid line in FIG.
” The lower limit value of the oscillation output signal in Fig. 2 is the voltage at point B,
It is determined by Here, if the value of the above-mentioned 1 pressure V is made larger LVt' (V+, '>VL), the lower limit value of the oscillating sawtooth waveform will become higher, and the oscillation frequency will become higher as shown by the dotted line a in Figure 2. Become. If the value of the voltage VL is made small ( )/L□ (VL□<Vt), the lower limit value of the oscillating sawtooth waveform becomes low, and the oscillation frequency becomes low as shown by the dotted line. Therefore, the free run frequency of the horizontal oscillation circuit (good) can be arbitrarily determined by the output voltage of the frequency-voltage conversion circuit (2).

Next, find the oscillation frequency of the horizontal oscillation circuit (3).

First, the terminal voltage (■) of the capacitor (6) during the charging period Tc. If the current flowing through the resistor (5) is ■, then Vc”
Vcc Rot・I --------・・
・---(1) [However, Rot is the resistance value of resistor (5)], and from Q=C・V, 1=dQ/dt, the electrician is l-Ce+dVc/dt +++
**+m++at (2) [However, CHI is the capacitance of capacitor (6)]. Here, equation (2) is converted into equation (1)
) and rearranging, VCC=ROI(ColdVc/dt)+VC・−・−
...---(3).

Also, the current flowing through the resistance (5) during the discharge period T is i
l, the discharge current of the capacitor (6) is i2, the resistor (21)
If the current flowing through is i, then i3w i1+ i, ...
(4), and the equation (4) is expressed as the following equation.

[However, R11 is the resistance value of resistor (21)] Here, rearranging equation (5), vec-co+Rat(dvc/at)+(Ro+/R
*++1)vc・・・・・・・・・(6)゛. Then, when the upper limit value of the oscillation output signal is set to ■0 and the lower limit value is set to ■1, and the charging and discharging period is calculated, the charging period To becomes, and the discharging period TD becomes... (8 ) becomes. Therefore, the oscillation frequency fH becomes. Here, the lower limit value vL of equations (7) and (8)
is determined depending on the output voltage of the frequency-voltage conversion circuit (2), and the oscillation frequency fH is determined according to the values of equations (7) and (8).
The free run frequency f of the horizontal oscillation circuit can be controlled according to the output voltage of the horizontal oscillation circuit.

Now, the horizontal deflection circuit (11) is the waveform shaping circuit (24)
A deflection current is supplied to the deflection coil (12) according to the oscillation output signal from the oscillation output signal, thereby controlling the deflection operation of the electron beam in the cathode ray tube (not shown). The flyback pulse generated at the upper end of the deflection coil (12) is sent to the phase comparator circuit (12).
13). Further, since a horizontal synchronizing signal is applied to the other input terminal, a phase comparison between the two signals is performed, and the error output thereof is smoothed by a smoothing circuit (b).

Then, the output DC voltage of the smoothing circuit (14) is applied to the resistance (
23) to the top of the capacitor (6).

If the output DC voltage increases in accordance with the phase difference, the value of the charging current to the capacitor (6) increases, so the frequency of the oscillation output signal increases. Conversely, if the output DC voltage decreases, the value of the charging current decreases, so the frequency decreases. Therefore, the horizontal oscillation circuit (base) oscillates in synchronization with the phase of the horizontal synchronization signal.

In other words, in the circuit shown in Fig. 4, after adjusting the free run frequency of the horizontal oscillation circuit (good) according to the output voltage of the frequency-voltage conversion circuit (2), the oscillation frequency is adjusted according to the output voltage of the smoothing circuit (b). The frequency is determined. Therefore, the horizontal oscillation circuit (base) can lock onto horizontal synchronizing signals having a wide range of frequencies.

(G) Effects of the Invention As described above, according to the present invention, the horizontal oscillation circuit is configured with a differential type oscillation circuit, and the base of one transistor that determines the lower limit value of the oscillating sawtooth waveform is connected to the base of the horizontal synchronizing signal according to the frequency of the horizontal synchronizing signal. Since the same voltage is applied, the free run frequency of the horizontal oscillation circuit can be set to an optimal value according to the frequency of the incoming horizontal synchronizing signal. Further, since the setting of the free run frequency can be changed continuously without using a switch, the oscillation output signal can be obtained in a continuous form even when changing.

Furthermore, according to the present invention, there is no need to switch the time constant, so multiple time constant circuits are not required, and the number of elements can be reduced.
It is also ideal for IC implementation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining FIG. 1. (1)...Input terminal, (2)...Frequency-voltage conversion circuit, (base)...Horizontal oscillation circuit, 4)...
First transistor, (Z)...charging/discharging circuit, (8
)...Second transistor, (9)...Third transistor, (Work)...Reference voltage generation circuit, (13)
...phase comparison circuit, (14) ...smoothing circuit, (
19)...transistor, (20)...transistor.

Claims (4)

[Claims] (1) A phase comparison circuit that compares the phase of the horizontal synchronization signal and the flyback pulse, a smoothing circuit that smoothes the output signal of the phase comparison circuit, and an oscillation frequency that is controlled according to the output signal of the smoothing circuit. In a multi-scan CRT display device comprising a horizontal oscillation circuit and a frequency-voltage conversion circuit that generates a control signal for changing the free run frequency of the horizontal oscillation circuit in accordance with a frequency change of the horizontal synchronization signal, The horizontal oscillation circuit is constituted by a differential oscillation circuit having first and second transistors whose emitters are commonly connected, and the output signal of the frequency-voltage conversion circuit is applied to the base of the first transistor, and the free run frequency is A multi-scan CRT display device, characterized in that the output signal of the smoothing circuit is applied to the base of the second transistor to adjust the oscillation frequency. (2) The multi-scan CRT display according to claim 1, wherein the voltage applied to the base of the first transistor in the horizontal oscillation circuit determines the lower limit value of the oscillating sawtooth waveform. Device. (3) A third transistor is provided whose emitter is connected to the common emitter of the first and second transistors in the horizontal oscillation circuit, and the upper limit of the oscillation sawtooth waveform is determined according to the reference voltage applied to the base of the third transistor. 3. The multi-scan CRT display device according to claim 2, wherein a value is determined. (4) a first transistor to which a voltage according to the horizontal synchronization signal frequency is applied to the base; a charging/discharging circuit consisting of a resistor and a capacitor connected in series between a power supply and ground; and an emitter connected to the emitter of the first transistor; a second transistor that is commonly connected and whose base is connected to the connection midpoint of the resistor and the capacitor; a reference voltage generation circuit that generates two reference voltages; and an output voltage of the reference voltage generation circuit that is applied to the base. and a third transistor whose emitter is connected to the common emitter of the first and second transistors.
a first switching circuit that switches charging/discharging of the charging/discharging circuit according to an output signal of the second transistor; and a second switching circuit that switches the output voltage of the reference voltage generating circuit according to the output signal of the second transistor. A multi-scan CRT display device comprising a horizontal oscillation circuit comprising a switching circuit and a horizontal oscillation circuit whose free run frequency is adjusted according to the base voltage of the first transistor.