JPH089184A - High voltage generator and imaging device - Google Patents

Abstract

(57) [Abstract] [Purpose] Achieves constant high-voltage output of the flyback transformer and prevention of ringing in the output waveform. A flyback transformer having means for changing its characteristic value in response to a load current, and in a first state where the load current value is low, resonates with a plurality of odd harmonics of a horizontal frequency of the flyback transformer. In the second state in which the load current increases from the first state, the resonance is deviated, and the high-voltage value of the flyback transformer is made substantially constant in the first and second states. . [Effect] The above object can be reliably achieved with a low-cost and simple configuration.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage regulation technique, and more particularly to improvement of a high voltage generating portion of a flyback transformer. [0002] As a conventional example, Japanese Patent Laid-Open No. 52-69522.
There is a technology described in Japanese Patent Publication. This is shown in FIG. According to the present technology, a resonance circuit including a coil 7, a capacitor 8 and a resistor 9 is inserted in series with the primary winding of the flyback transformer 6, the harmonic components of the high voltage output waveform are attenuated by the resistor 9 and the flyback is performed. The head of the transformer output waveform is made substantially flat as shown by the dotted line in FIG. 3 to widen the conduction range of the high voltage diode 10 and improve the high voltage regulation. However, in this circuit as well, it is inevitable that the high-voltage output will decrease as much as the high-voltage load is applied. As another conventional example, a saturable transformer is inserted in parallel with the primary winding of a flyback transformer, the inductance is changed by a high voltage load, and the high voltage is stabilized by changing the pulse width of the flyback period. However, in this case, the inductance change reaches several hundreds μH to several mH, so that the transformer becomes large and expensive, and ringing due to the inductance is likely to occur to easily disturb the screen. There are drawbacks. The above-mentioned prior art has a problem that the high voltage output decreases as the high voltage load increases. In addition, in the method of varying the inductance of the saturable transformer, the configuration is large and expensive, and ringing due to the inductance is likely to appear in the output waveform of the flyback transformer and interfere with the screen. An object of the present invention is to improve the above-mentioned drawbacks of the prior art, reduce the ringing of the output waveform of the flyback transformer under the conditions of low cost, small size and simple structure, and suppress the influence of high voltage load fluctuation. It is to realize the technology that can easily make the high voltage output constant. [0006] In order to achieve the above object,
The present invention provides a high-voltage generator according to the first invention, which has means for changing a characteristic value corresponding to a load current of a flyback transformer, and the flyback transformer in a horizontal state in a first state in which the load current value is low. In a second state in which the load current increases from the first state by resonating with a harmonic of a plurality of odd multiples of the frequency, the resonance shifts and the high voltage value of the flyback transformer is substantially reduced in the first and second states. The configuration is such that the adjusting means is configured to be constant. Further, the image device of the second invention has means for changing the characteristic value by the current corresponding to the brightness signal of the image, and the horizontal position of the flyback transformer in the first state where the brightness of the image is dark. In the second state in which the resonance of the harmonics of a plurality of odd multiples of the frequency causes the brightness of the image to increase from the first state, the resonance shifts and the high voltage value of the flyback transformer is changed in the first and second states. The configuration is such that the adjusting means is configured to be substantially constant. The adjusting means in the first and second inventions resonates with the harmonics of the flyback transformer when the load current is small, removes the harmonic components contained in the flyback pulse, and removes the secondary side. On the contrary, when the load current increases, the resonance shifts to decrease the rate of removal of the harmonic components and increase the peak value of the pulse. In other words, while suppressing an increase in high voltage when the load is low, and preventing a drop in high voltage when the load increases, suppressing the effect of load fluctuations,
The high voltage value of the flyback transformer is always kept constant. That is, as the load current value increases, the flyback transformer's 1
The peak value of the pulse is adjusted by reducing the rate of removing the harmonics contained in the secondary pulse. Embodiments of the present invention will be described below with reference to FIG. 1 is a horizontal output transistor, 2 is a damper diode, 3 is a resonance capacitor, 4 is a horizontal deflection coil, 5 is an S-shaped correction capacitor, 6 is a flyback transformer, 8 is a capacitor, 9 is a resistor, 10 is high voltage rectification. Diode, 11 is a power supply capacitor, 12 is related to the present invention,
It is a saturable transformer. Capacitor 8, resistor 9, saturable transformer 1
The second secondary winding forms a resonant circuit that attenuates the harmonic components of the flyback transformer output. A characteristic diagram of the saturable transformer 12 is shown in FIG. When the primary winding current increases, the two inductances decrease. In the structure of this embodiment, when the high voltage load increases, the power supply current flowing from the point B increases. This reduces the secondary inductance of the transformer 12,
Capacitor 8 and resistor 9 connected in parallel with this winding
Resonance effects in series circuits are reduced. The harmonic components are not attenuated and the output waveform peak value extends as shown by the solid line in FIG. On the contrary, when the high-voltage load decreases, the power supply current flowing from the point B decreases, the secondary inductance of the transformer 12 increases, the resonance becomes active, and the resonance effect increases. The harmonic components are attenuated and the peak value is lowered and the characteristics become flat as shown by the dotted line in FIG. Since the high voltage is obtained by rectifying the waveform shown in FIG. 3 with the high voltage rectifying diode 10, the high voltage regulation characteristic is improved by the above-mentioned principle. This characteristic is shown in FIG. In the experiment, a capacitor 0.01 μF, a resistance 27 Ω, a saturable transformer, a secondary winding inductance 68
An improvement in high pressure regulation of 1.5 KV was obtained with a change of μH to 20 μH. Since the primary winding current of the saturable transformer 12 may be a current corresponding to a high voltage load, the A.V. B. You may drive using L (automatic brightness limitation) detection voltage. The object of the invention can be achieved even if the resistor 9 is composed of a semiconductor element and the internal impedance is changed according to a high voltage load. Further, in the circuit of FIG.
Alternatively, a self-saturation type coil depending on the current may be used. FIG. 4 shows a screen distortion prevention circuit. The drawing distortion is a phenomenon in which the high voltage is lowered in a bright portion of the screen, the deflection sensitivity is increased, and the screen size is expanded. From the above description, it is clear that the screen distortion can be corrected by flowing a current according to the screen brightness in the primary winding of the saturable transformer 12 to perform high voltage correction. When the present invention is applied to flyback transformers of different high-order tuning, since the harmonic frequency is high, it is necessary to increase the resonance circuit frequency of the present invention as well. Therefore, the capacitor capacitance must be small. I have to. In this case, since there is distributed capacitance in the saturable transformer winding, the capacitor may not be particularly connected. That is,
It can also be configured with a parallel circuit of a saturable transformer and a resistor. This is shown in FIG. In this circuit, the pulse applied to the primary winding of the flyback transformer is obtained by dividing the inductance of the primary winding of the flyback transformer and the inductance of the saturable transformer, and when the high voltage load is heavy,
The saturable transformer inductance is reduced, the pulse of the primary winding of the flyback transformer is increased, and the high voltage regulation is improved. In this embodiment, one of the flyback transformers is used.
Although the variable resonance circuit including the resistance is inserted in the next winding, the flyback transformer has a transformer structure, and therefore the circuit of the present invention may be inserted in the high voltage winding side. An example of this is shown in FIG. Further, as shown in FIG. 7, a variable resonance circuit including the above resistance may be inserted in both of the primary winding and the secondary winding. In this case, the high voltage regulation effect is further increased. To do. According to the present invention, constant high voltage output can be easily realized under a low cost, small size and simple circuit configuration.
At the same time, the occurrence of linking during the horizontal scanning period can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of the device of the present invention. FIG. 2 is a characteristic diagram of a saturable transformer used in an example of the present invention. FIG. 3 is a waveform diagram of high voltage output. FIG. 4 is a circuit diagram of a screen distortion correction circuit using the present invention. FIG. 5 is a circuit diagram of a harmonic attenuation circuit composed of a saturable transformer and a resistor. FIG. 6 is a diagram showing another embodiment of the present invention. FIG. 7 is a diagram showing another embodiment of the present invention. FIG. 8 is a diagram showing a voltage drop characteristic. FIG. 9 is a diagram of a conventional example. [Explanation of Codes] 1 ... Horizontal output transistor, 2 ... Damper diode, 3 ... Resonance capacitor, 4 ... Horizontal deflection coil, 5 ... S-shaped correction capacitor, 6 ... Flyback transformer, 7 ... Coil, 8 ... Capacitor, 9 ... Resistance, 10 ... High-voltage rectifier diode, 11 ... Power supply capacitor, 12 ... Saturable transformer.

Claims (1)

[Claims] 1. In a first state in which the load current value is low, there is a means for changing the characteristic value corresponding to the load current of the flyback transformer, and the load current resonates with a harmonic of a plurality of odd multiples of the horizontal frequency of the flyback transformer. In the second state in which the first state is increased, the resonance is deviated, and the high-voltage value of the flyback transformer is made substantially constant in the first and second states. High-voltage generator characterized by. 2. In the first state where the characteristic value is changed by the current corresponding to the brightness signal of the image, in the first state where the brightness of the image is dark, it resonates with the harmonics of a plurality of odd multiples of the horizontal frequency of the flyback transformer. In the second state in which the brightness is higher than the first state, the resonance is deviated, and the high-voltage value of the flyback transformer is made substantially constant in the first and second states. An imaging device characterized by the above.