Electricity: electrical systems and devices – Safety and protection of systems and devices – Voltage regulator protective circuits
Reexamination Certificate
1999-07-06
2001-06-12
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Voltage regulator protective circuits
C315S370000, C348S607000
Reexamination Certificate
active
06246554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video display apparatus, and more particularly, to a surge protector for the video display apparatus capable of preventing the video display apparatus from malfunctioning due to a drastic change of high voltage from a discharge of a cathode-ray tube or external circumstances.
2. Description of the Prior Art
In general, in a video display apparatus which adopts the cathode-ray tube using a high voltage, such as a monitor of a computer system, a surge voltage is often generated due to a display mode change, a power source on/off or a display power management system mode change operation.
An earlier high voltage generating circuit of the video display apparatus has a microcomputer for receiving horizontal and vertical sync signals H-SYNC and V-SYNC (hereinafter, referred to as H/V sync signals) and a plurality of control signals, a horizontal/vertical processor (hereinafter, referred to as an H/V processor) for generating horizontal and vertical oscillation signals in response to H/V sync signals H-SYNC and V-SYNC from the microcomputer to output a switching signal, a switching circuit for outputting an external voltage Vcc in response to a switching signal, a high voltage generator for amplifying the voltage Vcc from the switching circuit to supply a high voltage to a cathode-ray tube CRT, and a constant-voltage circuit for comparing a voltage signal from the high voltage generator with a predetermined reference voltage and for outputting a constant-voltage control signal to control a duty cycle of the voltage Vcc supplied to the high voltage generator.
If the voltage signal is higher than the predetermined reference voltage, the output voltage Vcc which is supplied to the high voltage generator goes down because the duty cycle of the voltage Vcc decreases due to the constant-voltage control signal.
On the contrary, if the voltage signal is lower than the predetermined reference voltage, the output voltage Vcc which is supplied to high voltage generator goes up because the duty cycle of the voltage Vcc increases due to the constant-voltage control signal. Accordingly, the high voltage generated by high voltage generator usually maintains a uniform voltage level.
However, if the high voltage supplied to the cathode-ray tube is drastically reduced by impurities inside the cathode-ray tube or other factors, the voltage level of the high voltage from the high voltage generator lowers. As a result, since the voltage level of the voltage signal inputted to the constant-voltage circuit lowers, the duty cycle of the voltage Vcc increases due to the constant-voltage control signal from the constant-voltage circuit.
According, an overcurrent flows from the switching circuit to the high voltage generator and the high voltage generator malfunctions due to the overcurrent.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a surge protector for a video display apparatus capable of preventing the video display apparatus from malfunctioning due to a drastic change of high voltage from a discharge of a cathode-ray tube or external circumstances.
In order to achieve the above object, the present invention provides a surge protector for a video display apparatus, the surge protector comprising: a controller for outputting horizontal and vertical sync signals and a plurality of control signals and for outputting a switching control signal in response to an external control signal; a switching signal generator for outputting a switching signal in response to the horizontal and vertical sync signals and the switching control signal from the controller; a switching circuit for receiving first and second external voltages, and for outputting the second voltage in response to the switching signal and for selectively enabling a path of the second voltage from the switching circuit in response to the external control signal; a high voltage generator for generating a high voltage in response to the second voltage inputted from the switching circuit; a constant-voltage circuit for comparing the high voltage from the high voltage generator with a predetermined reference voltage and for generating a constant-voltage control signal for controlling a duty cycle of the second voltage of the switching circuit in response thereto; and a surge voltage protector for respectively supplying the control signal for controlling the path of the second voltage to the controller and the switching circuit in response to the constant-voltage control signal.
In the surge protector for the video display apparatus according to the present invention, the duty cycle of the path for supplying a voltage to a transformer of the high voltage generator is controlled by the voltage level of the constant-voltage control signal which is generated based on the compared value between the voltage level of the voltage signal inputted from the transformer of the high voltage generator and the voltage level of the reference voltage. Accordingly, the voltage being supplied to the transformer of the high voltage generator maintains an uniform voltage level even though the voltage level of the high voltage is drastically changed due to the discharge of the cathode-ray tube or external circumstances. Therefore, the video display apparatus is prevented from malfunctioning.
REFERENCES:
patent: 5079666 (1992-01-01), Najm
patent: 5491794 (1996-02-01), Wu
patent: 5627437 (1997-05-01), Kim
patent: 5917716 (1999-06-01), Cho
patent: 5944830 (1999-08-01), Hong et al.
patent: 6005789 (1999-12-01), Lee
patent: 6020694 (2000-02-01), Shim
patent: 6043814 (2000-03-01), Lim
patent: 6100935 (2000-08-01), Inoue
Bushnell , Esq. Robert E.
Huynh Kim
Samsung Electronics Co,. Ltd.
Sherry Michael J.
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