JPH0453356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a deflection circuit that can continuously vary the horizontal scanning frequency.

[Conventional technology]

With the spread of personal computers,
Many television receivers that also function as RGB displays have become known. However, some RGB outputs of personal computers have a horizontal synchronization frequency of 15.75KHz, which is the standard frequency, and others of 24.83KHz, which is aimed at high resolution. It becomes necessary to switch the horizontal oscillation frequency within the television receiver.

The conventional deflection circuit 1 shown in FIG. 4 converts the frequency and voltage of a synchronizing signal supplied from an externally connected device such as a personal computer in a frequency/voltage conversion circuit 2, and then converts the high frequency component into a low frequency circuit 3. is removed and supplied to the horizontal oscillation circuit 4. The oscillation frequency of the horizontal oscillation circuit 4 is controlled to be constant by an automatic frequency control circuit 5, and its horizontal oscillation output is supplied to a horizontal output circuit 7 via a horizontal drive circuit 6. The horizontal output pulse obtained from the horizontal output circuit 7 is fed back to the automatic frequency control circuit 5 via an integrating circuit 8 whose time constant can be changed.

By the way, the horizontal output circuit 7 includes a damper diode D, resonant capacitors Ca and Cb, and deflection coils L and S in parallel to the collector of the horizontal output transistor Q.
It has a configuration in which a series connection circuit of a character correction capacitor CCs and a dummy coil Ld is connected, but in order to support horizontal synchronization signal input other than the standard frequency, the resonance capacitor Ca and the dummy coil Ld are connected to switches 9 and 10 that operate in conjunction with each other. They are constructed so that they can be opened or shorted, respectively. The mode discrimination circuit 3a connected to the low frequency circuit 3 is connected to the low frequency circuit 3.
The deflection mode is determined from the output level, and the switches 9 and 10 are controlled to open and close.

[Problem that the invention seeks to solve]

The above-mentioned conventional deflection circuit 1 changes the amplitude of the deflection current or the ratio of the horizontal scanning period to the horizontal retrace period to the horizontal synchronizing signal input of the standard frequency in response to the input of the horizontal synchronizing signal of a specific frequency other than the standard frequency. However, if you try to apply the same treatment to the horizontal synchronization signal input at a frequency other than the specified frequency, you will need to increase the number of resonant capacitors and tap the dummy coil. The number of circuits had to be increased, which caused problems such as the complexity of the circuit configuration.

[Means for solving problems]

The present invention solves the above problems, and is a deflection circuit that actively changes circuit constants of a horizontal output circuit according to the frequency of a horizontal synchronizing signal input, the invention comprising: a deflection coil in the horizontal output circuit; A saturable reactor is connected in series, and the inductance of the controlled winding is varied by the current flowing through the control winding.A parabolic wave synchronized with horizontal scanning is superimposed on the control winding current of this saturable reactor, and the inductance of the controlled winding is varied by the current flowing through the control winding. The gist of the present invention is to provide a suppressing means for suppressing changes in inductance of the saturable reactor.

[Effect]

This invention adjusts the deflection current waveform when switching the horizontal oscillation frequency by varying the current flowing through the control winding of the saturable reactor connected in series with the horizontal deflection coil, and also adjusts the control current of the saturable reactor. A parabolic wave with a horizontal scanning period is superimposed on the inductance of the saturable reactor to suppress changes in the inductance of the saturable reactor due to the deflection current.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. Figures 1 to 3
The figures are a circuit configuration diagram, a signal waveform diagram of each part of the circuit, and a saturation characteristic diagram of a saturable reactor, respectively, showing one embodiment of the deflection circuit of the present invention. In FIG. 1, the same components as those in FIG. 4 are given the same reference numerals.

In FIG. 1, the deflection circuit 11 connects a saturable reactor 12 to the deflection coil L in the horizontal output circuit 7 via an S-shaped correction capacitor Cs, and the inductance of the controlled winding 12a of the saturable reactor 12 In order to suppress fluctuations in , a parabolic wave having a horizontal scanning period is superimposed on the control current applied by the control winding 12b.

In the saturable reactor 12, the inductance of the controlled winding 12a changes depending on the current flowing through the control winding 12b, and as shown in FIG.
Deflection currents I ₁ , I ₂ , I ₃ , flowing through the controlled winding 12a,
The inductance of the controlled winding 12a also changes depending on...

The control current flowing through the control winding 12b is generated by a drive circuit 13. A parabolic wave superimposition circuit 14 is connected to this drive circuit 13, and converts the parabolic wave of the horizontal scanning period into a low-frequency wave. It is superimposed on the output of circuit 3. Reference numeral 15 denotes a parabolic wave generation circuit that generates a parabolic wave, which receives the horizontal output pulse of the horizontal output circuit 7 as an input and is controlled by a control circuit 16 that operates according to the output of the low frequency circuit 3.

Now, the frequency of the horizontal synchronization signal sent from the externally connected device is the standard frequency of 15.75KHz,
When the output of the low frequency circuit 3 indicates the standard mode, the switch 9 is in the open state.
When the horizontal output circuit 7 is driven by the output of the horizontal drive circuit 6, the parabola wave generation circuit 15 generates a parabola wave, and the parabola wave superimposition circuit 14 applies a parabola wave to the output of the low frequency circuit 3. superimpose wave voltage.

Therefore, the control winding 12b of the saturable reactor 12
A parabolic current shown by a solid line in FIG. 2c is supplied by the control circuit 16. As a result, the control current supplied to the control winding 12b at the center of the horizontal scan takes the maximum value, but the control current supplied to the controlled winding 12b
Controlled winding 12 due to changes in the deflection current flowing through a
The change in inductance a is suppressed by the parabolic control current flowing through the control winding 12b.
Therefore, the controlled winding 12a of the saturable reactor 12
The inductance of is kept approximately constant during the horizontal scanning period.

In addition, if the horizontal synchronization signal sent from the externally connected device has a non-standard frequency, the parabolic wave superimposition circuit 14 superimposes a DC signal to compensate for the change in the output of the low frequency circuit 3. changes, and the current flowing through the control winding 12b of the saturable reactor 12 becomes as shown by the dashed line in FIG. 2c. However, as in the standard mode, the inductance of the controlled winding 12a of the saturable reactor 12 can be kept almost constant during the horizontal scanning period.
A predetermined deflection current waveform can be obtained.

In this way, the deflection circuit 11 changes the circuit constant when the horizontal oscillation frequency is changed by varying the current flowing through the control winding 12b of the saturable reactor 12 connected in series with the deflection coil L in the horizontal output circuit 7. In addition, the circuit constant of the horizontal output circuit 7 is changed to The inductance can be continuously varied, and therefore has a high ability to respond to expected horizontal synchronization signal inputs of various frequencies, and the inductance changes depending on the current flowing through the controlled winding 12b, which is unique to the saturable reactor 12. This problem can also be improved by superimposing parabolic waves.

〔Effect of the invention〕

As explained above, according to the present invention, the current flowing through the control winding of the saturable reactor connected in series to the deflection coil in the horizontal output circuit is varied, and the circuit constants can be changed when the horizontal oscillation frequency is switched. At the same time, a parabolic wave with a horizontal scanning period is superimposed on the control current of the saturable reactor to suppress changes in the inductance of the saturable reactor due to the deflection current, so the circuit constant of the horizontal output circuit can be continuously varied. Therefore, it has a high ability to respond to expected horizontal synchronization signal inputs of various frequencies, and it also solves the problem of inductance changing due to the current flowing through the controlled winding, which is unique to saturable reactors. Superimposition produces excellent effects such as improvement.

[Brief explanation of the drawing]

1 to 3 are circuit configuration diagrams showing one embodiment of the deflection circuit of the present invention, signal waveform diagrams of various parts of the circuit, and saturation characteristic diagrams of a saturable reactor, and FIG. 4 is a diagram of a conventional deflection circuit. FIG. 2 is a circuit configuration diagram showing an example. 7... Horizontal output circuit, 11... Deflection circuit, 12... Saturable reactor, 12a... Controlled winding, 12b... Control winding, 13... Drive circuit, 14... Parabolic wave superimposition circuit, 15... Parabolic wave generation circuit, 16 ...Control circuit, L...Deflection coil.

Claims (1)

[Claims] 1 A deflection circuit that actively changes the circuit constant of a horizontal output circuit according to the frequency of horizontal synchronization signal input, which is connected in series to a deflection coil in the horizontal output circuit and controlled by a current flowing through a control winding. A saturable reactor in which the inductance of a winding is varied, and a suppressing means for superimposing a parabolic wave of a horizontal scanning period on a control winding current of the saturable reactor to suppress changes in the inductance of the saturable reactor due to a deflection current. Deflection circuit provided.