Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1993-04-26
1994-05-31
Stephan, Steven L.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
315411, H02M 3335, H01J 2970
Patent
active
053174950
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a stabilized high voltage power supply circuit in a cathode-ray-tube (hereinafter referred to CRT), and more particularly to a stabilized high voltage power supply circuit which has high speed response and is operatable with low power consumption.
BACKGROUND OF THE ART
As a beam current in the color CRT is several times larger, as compared with the monotone CRT, a large variation of average beam current depends on screens. This large variation makes a voltage regulation be lower, thereby a variation of a horizontal amplitude and a deterioration of a focus and convergence are caused to affect an operation of the CRT. To combat these problems, various stabilized high voltage power supply circuits have been conventionally produced, in which stabilization of high voltage is achieved even when the average beam current has a variation.
FIG. 7 shows a stabilized high voltage power supply circuit using a transistor for controlling high voltage, in which a reference number 10 depicts a horizontal output transistor, 12 a damper diode, 14 a resonance capacitor, 16 a deflecting coil, 18 a capacitor preventing direct current. These elements define a normal horizontal output circuit so as to obtain a high voltage output through a diode 22 connected to a secondary coil 202 in a flyback transformer 20. A primary coil 201 is connected at its intermediate tap to a collector of a transistor for controlling high voltage in the secondary side through a diode 24 and a resistance 26. The transistor 28 for controlling high voltage is connected at its emitter with the primary coil 201 and a secondary coil 203 through a resistance 30 and further with a supply voltage Vcc. The secondary coil 203 is so connected at its opposite ends with a series circuit comprising a diode 32 and a capacitor 34 as to be parallel to the series circuit. The capacitor 34 is so connected with a variable resistance 36 as to be parallel to the variable resistance 36. The variable transistor 36 is connected with the transistor 28 for controlling high voltage at its base.
In such the stabilized high voltage power supply circuit shown in FIG. 7, a pulse voltage is so rectified through the diode 24 as to be a direct positive voltage. The direct positive voltage is applied to the transistor 28 for controlling high voltage at its collector through the resistance 26 and further a pulse voltage in the secondary coil 203 is so rectified through a diode 32 as to be a direct voltage. The direct voltage is applied to the transistor 28 for controlling high voltage at its base through the variable resistance 36, thereby the transistor 28 for controlling high voltage is so biased into a forward direction as to remain a collector voltage at a flowing state and is used. Accordingly, one part of a deflecting output is used at the resistance 26 and the transistor 28 for controlling a high voltage. At the same time, a voltage reduction at the resistance 30 by the collector voltage of the horizontal output transistor 10 is applied to the base of the transistor for controlling high voltage and further serves to cancel a rectified voltage in the diode 32. When the collector current in the horizontal output transistor 10 is increased due to an increase of a high voltage current, the voltage reduction in the resistance 30 is also increased. As a result of that, a base voltage in the transistor 28 for controlling high voltage is lowered, so that the collector voltage in the transistor 28 for controlling high voltage is decreased. Therefore, loss in a controlling circuit is so decreased as to increase a high voltage, so that a high voltage output level is maintained at constant.
Referring to FIG. 8 showing a stabilized high voltage power supply circuit in a controlling system for a power supply, the transistor 28 for controlling high voltage is so connected between a power supply Vcc and the primary coil 201 in the flyback transformer 20 as to be series thereto and a transistor 40 is connected with the transistor 28 for controlling high
REFERENCES:
patent: 4531181 (1985-07-01), Herz et al.
patent: 4561047 (1985-12-01), DePuy
patent: 4885509 (1989-12-01), Ikevchi
patent: 5019953 (1991-05-01), Kawaberi et al.
patent: 5049792 (1991-09-01), Oh
patent: 5189599 (1993-02-01), Messman
Nguyen Matthew
Stephan Steven L.
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