JPH0473670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a horizontal deflection device for a television receiver that displays various signals having different horizontal frequencies.

Conventional Structure and Problems There has been a significant increase in demand for television receivers as computer terminals in recent years. The horizontal frequency of the signal from this computer does not necessarily match the horizontal frequency of the NTSC and PAL systems currently used in Japan and overseas, and ranges from around 15KHz to over 30KHz.
It is widespread and diverse. Furthermore, the horizontal frequency of the high-definition television system, which is planned to be put into practical use soon, is 33.75KHz, approximately twice that of the NTSC system. When trying to realize a television receiver that can display various signals with such a wide variety of horizontal frequencies, it is necessary to use horizontal deflection coils in order to keep the amplitude of the screen almost constant even when the horizontal frequency changes. This can be achieved by increasing or decreasing the voltage supplied to the horizontal output transistor according to the horizontal frequency so that the flowing current remains constant. At this time, it is necessary to consider not only the amplitude of the screen but also raster distortion correction such as left and right pincushion distortion correction, and left and right trapezoidal distortion correction in the case of a projection television. That is, when performing raster distortion correction by modulating the voltage supplied to the horizontal output transistor with a vertical period signal, the ratio of the vertical period signal amplitude to this voltage is always kept constant when the voltage is increased or decreased. (In other words, the amplitude of the vertical period signal must be controlled so that the degree of modulation of the current flowing through the horizontal deflection coil by the vertical period signal is always constant.) That is, when the horizontal frequency changes, it is necessary to control not only the screen amplitude but also the signal amplitude of the vertical period so that the raster distortion correction does not need to be adjusted.

An example of technology to realize this is
-Disclosed in Publication No. 74833. In the same publication,
In order to detect the current flowing through the horizontal deflection coil, a resistor is connected in series with the horizontal deflection coil, and the voltage generated across this resistor is fed back to the pulse width control section of the switching power supply to control the voltage supplied to the horizontal output transistor. By controlling the horizontal deflection coil, the current flowing through the horizontal deflection coil is controlled to be constant. In addition, a secondary winding of the converter transformer of the switching power supply and a detection circuit that detects the voltage generated in this secondary winding are provided, and the voltage supplied to the horizontal output transistor is indirectly detected by the output of this detection circuit. It controls the amplitude of the vertical period parabolic wave that is detected and corrected for left and right pincushion distortion. However, this configuration requires a secondary winding of the converter transformer, a detection circuit that detects the voltage generated in this secondary winding, and a circuit that controls the magnitude of the vertical period parabolic wave in response to the output of the detection circuit. Therefore, the configuration becomes complicated. In addition, the magnitude of the vertical period parabolic wave is controlled by indirectly detecting the voltage supplied to the horizontal output transistor, and the vertical period parabolic wave component flowing to the horizontal deflection coil is controlled by feedback control. As a result, the accuracy of tracking the left and right pincushion distortion correction amount with respect to changes in horizontal frequency deteriorates, and the adjustment method for the circuit that controls the magnitude of the parabolic wave using the output of the detection circuit becomes very complicated. have. Furthermore, since a resistor is connected in series to the horizontal deflection coil, loss due to the resistor occurs, and the deflection current detection signal from this resistor is added to the raster distortion correction signal and applied to the pulse width control section of the switching power supply. Therefore, the deflection current has the disadvantage that it is not modulated by the raster distortion correction signal.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned drawbacks and provides a horizontal deflection device that can always achieve appropriate amplitude and appropriate raster distortion correction with a simple configuration even when displaying signals with different horizontal frequencies. With the goal.

Structure of the Invention The present invention provides a horizontal deflection device for a television receiver that displays various signals with different horizontal frequencies, including a current detection circuit that detects a current flowing through a horizontal deflection coil, and a current detection circuit that detects the output of the current detection circuit and raster distortion. Equipped with an error amplifier that inputs a signal with a vertical period to be corrected and a voltage control section that controls the voltage supplied to the horizontal output transistor with the output of this error amplifier, it is easy to use even when displaying signals with different horizontal frequencies. With this configuration, it is possible to always achieve appropriate amplitude and appropriate raster distortion correction.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The figure shows an embodiment in which the present invention is applied to a projection television, in which a damper diode 2, a resonant capacitor 3, horizontal deflection coils 4, 5, 6, and a horizontal transformer 7 are connected to a horizontal output transistor 1. Further, an S-shaped correction capacitor 8 and a coil 91 of a current detection circuit 9 are connected in series with the deflection coils 4, 5, and 6. The current detection circuit 9 includes a coil 91,
Diode 92, capacitor 93, variable resistor 94
It consists of The voltage control unit 10 includes transistors 101 and 105, a diode 102, a choke coil 103, a capacitor 104, and a comparator 106, and the output voltage is supplied to the horizontal transformer 7. Reference numeral 11 denotes an error amplifier, to which the output of the current detection circuit 9 and a vertically periodic signal are supplied via transistors 12 and 14 to its input terminal.

Next, the operation of this embodiment will be explained. A drive pulse is supplied to the base of the horizontal output transistor 1 from a drive transformer (not shown), and as is well known, a sawtooth wave current flows through the deflection coils 4, 5, and 6. The total current flowing through these deflection coils flows through the primary coil of the coil 91 connected in series with these deflection coils.
Therefore, a pulse having a magnitude proportional to the total current is generated in the secondary winding of the coil 91. This pulse is peak rectified by diode 92 and capacitor 93. Therefore, capacitor 93
A DC voltage proportional to the deflection current is obtained from both ends of the deflection current. The DC voltage thus obtained is supplied to the error amplifier 11 through the variable resistor 94.

The voltage control unit 10 constitutes a chopper type switching regulator using pulse width control.
It is well known that the output voltage can be controlled by controlling the duty cycle of transistor 101 that performs a switching operation. The output of the error amplifier 11 and a horizontally periodic sawtooth wave are supplied to the input terminal of the comparator 106, and the comparator 106 compares the DC levels of the signals applied to these two input terminals, and compares the DC level of the output of the error amplifier 11. During the period when the output voltage is high, the output level is high and the transistor 105 is turned on. Conversely, during a period when the DC level of the horizontally periodic sawtooth wave is high, the output level is low and the transistor 105 is cut off. transistor 1
01 is conductive when the transistor 105 is conductive;
It is cut off when it is cut off. Therefore, if the output level of the error amplifier 11 changes, the transistor 10
The duty cycle of the transistor 101 also changes and the output voltage also changes (as the output of the error amplifier 11 becomes higher, the conduction period of the transistor 101 becomes wider and the output voltage becomes higher). By the way, the output of the current detection circuit 9 is supplied to one of the input terminals of the error amplifier 11.
The emitter voltage of the transistor 14 is supplied to the other end. Now considering the case where no vertically periodic signal is applied to the base of the transistor 12, the emitter voltage of the transistor 14 is the Zener voltage of the Zener diode 15, the resistor 16,1
7. The DC voltage is determined by the base-emitter voltage of the transistor 14. Therefore, the error amplifier 11 generates a voltage corresponding to the difference between this DC voltage and the output voltage of the current detection circuit 9, and supplies it to the comparator 106. If the output voltage of the current detection circuit 9 becomes larger than the DC voltage (if the horizontal amplitude becomes larger than the specified value), the output voltage of the error amplifier 11 decreases, and the transistor 10
1 becomes narrower. Therefore, the voltage supplied to the horizontal transformer 7 becomes lower and the deflection current also decreases, and when the output voltage of the current detection circuit 9 decreases and becomes equal to the emitter voltage of the transistor 14, it is balanced and the horizontal amplitude returns to its original state. Conversely, when the output voltage of the current detection circuit 9 becomes smaller (when the horizontal amplitude becomes smaller than the specified value), contrary to the above case, the conduction period of the transistor 101 becomes wider, the deflection current increases, and the current is detected. When the output voltage of the circuit 9 becomes equal to the emitter voltage of the transistor 14, it is balanced and the horizontal amplitude returns to its original state. In this way, the loop of the error amplifier 11, the voltage control section 10, and the current detection circuit 9 is controlled so that the voltages at the two input terminals of the error amplifier 11 are equal. At this time, since the emitter voltage of the transistor 14 is constant, the output voltage of the current detection circuit 9, that is, the deflection current is controlled to be constant. Therefore, when the horizontal frequency changes and the deflection current is about to change, the output voltage of the voltage control section 10 is changed by the aforementioned control loop to keep the deflection current constant. That is, even when the horizontal frequencies differ, a constant deflection current always flows through the deflection coils 4, 5, and 6, and the amplitude can be kept constant.

Next, raster distortion correction will be explained. The embodiment illustrates the case of correcting trapezoidal distortion, in which a sawtooth wave with a vertical period is applied to the base of the transistor 12. Since a sawtooth wave having the same polarity as the base is obtained at the emitter of the transistor 12, and a sawtooth wave having the opposite polarity from the base at the collector, a correction waveform having the necessary polarity and magnitude is extracted by the variable resistor 13. The extracted vertical periodic sawtooth wave is applied to the base of the transistor 14 and superimposed on the reference voltage generated by the Zener diode 15 mentioned above. This voltage is then supplied to the input end of the error amplifier 11. When a vertically periodic signal is applied to the input terminal of the error amplifier 11, the output voltage of the error amplifier 11 changes in accordance with the waveform and magnitude, and the duty cycle of the transistor 101 is controlled, resulting in voltage control. The output voltage of section 10 is modulated in magnitude by a sawtooth waveform with a vertical period. Therefore, the current flowing through the deflection coils 4, 5, and 6 undergoes amplitude modulation with a vertically periodic sawtooth wave. That is, correction of trapezoidal distortion is performed.

By the way, as mentioned above, the loop composed of the error amplifier 11, the voltage control section 10, and the current detection section 9 is as follows.
Since control is performed to equalize the voltages at the two input terminals of the error amplifier 11, if a voltage obtained by superimposing a vertically periodic sawtooth wave on the reference voltage is applied to one of the input terminals, the output of the current detection section 9 becomes It depends entirely on this voltage. In other words, even if the horizontal frequency changes,
The deflection current is kept constant, and the amount of raster distortion correction is also kept constant. Therefore, even when displaying signals with different horizontal frequencies, there is no need to adjust the horizontal amplitude or raster distortion correction.

In the embodiment, the case where the raster distortion is trapezoidal distortion has been illustrated and described, but it is clear that in the case of pincushion distortion, it is better to supply a vertical parabolic wave to the base of the transistor 14. Further, although a horizontally periodic sawtooth wave is used as an input to the comparator 106, the same operational effect can be obtained with a triangular wave or a parabolic wave. Furthermore, the embodiments have been illustrated and described with reference to the case of synchronization with the horizontal period, and it is obvious that the initial objective can be achieved without synchronization with the horizontal period.

By the way, in the embodiment, a sawtooth wave with a vertical period for correcting trapezoidal distortion is supplied to the base of the transistor 12, but if a sawtooth wave with a magnitude proportional to the vertical deflection current is used, the vertical amplitude can be changed. Even in such a case, since the amount of correction for trapezoidal distortion can be changed in proportion to the change in vertical amplitude, it is possible to eliminate the need to adjust the amount of correction for trapezoidal distortion in response to changes in vertical amplitude.

Effects of the Invention As described above, the present invention provides a current detection circuit for detecting a current flowing through a horizontal deflection coil, and an output of the current detection circuit and a vertical period in a television receiver that displays various signals with different horizontal frequencies. and a voltage control section that controls the voltage supplied to the horizontal output transistor with the output of this error amplifier, so that even if the horizontal frequency changes, the deflection current flowing through the deflection coil and The vertical period raster distortion correction amount can always be controlled to be constant. Therefore, even if signals with different horizontal frequencies are selectively input, there is no need to readjust the horizontal amplitude, trapezoidal distortion, or pink distortion correction amount each time. In other words, there is no need to adjust the horizontal frequency for changes. The practical effect is great because it allows for

[Brief explanation of drawings]

The figure is a wiring diagram of a horizontal deflection device in one embodiment of the present invention. 4, 5, 6... Deflection coil, 9... Current detection circuit, 11... Error amplifier, 10... Voltage control section.

Claims (1)

[Claims] 1. A current detection circuit that detects the current flowing through the horizontal deflection coil, an error amplifier that receives the output of this current detection circuit and a vertical period signal as input, and outputs the difference between the two outputs, and this error amplifier. A horizontal deflection device comprising a voltage control unit that controls the voltage supplied to the horizontal output transistor by the output of the horizontal deflection device. 2. The horizontal deflection device according to claim 1, wherein the current detection circuit performs peak rectification of pulses generated in a coil connected in series with the horizontal deflection coil. 3. The horizontal deflection device according to claim 1, wherein the vertical period signal input to the error amplifier has a reference DC potential. 4. The horizontal deflection device according to claim 1, wherein the voltage control section is a pulse width controlled switching power supply.