JPH02230871A - X-ray protector device - Google Patents

Abstract

PURPOSE:To normally display a sharp pattern with high brightness by detecting whether or not an output level of a boosting transformer exceeds a reference value with a comparator and stopping a pulse output of a high voltage drive circuit with a time monitor control circuit when the detected output exceeds the setting level and the state elapses for a prescribed time. CONSTITUTION:A drive output control circuit 6A uses a comparator 8 so as to detect whether or not an output level of a boosting transformer 2 exceeds a reference value in terms of a level of a DC low voltage. When the detected output exceeds the setting level and the state elapses for a prescribed time, a time monitor control circuit 9 outputs a control signal stopping a pulse output from a high voltage drive circuit 1 and supplies allowable high voltage to a cathode ray tube in the normal state when the level of the DC low voltage does not exceed a reference value. Thus, the erroneous stop of the pulse output of the high voltage drive circuit due to a transient high voltage rising is surely prevented and a sharp pattern with high brightness is able to be displayed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an X-ray protector device for controlling X-ray leakage from a cathode ray tube used as a display device.

[Conventional technology]

Figure 2 shows, for example, the Mitsubishi Electric catalog ``Model l1hFA3''.
415ATK J (published in 1987). In the figure, 1 is a high voltage drive circuit, and 2 is a step-up transformer (hereinafter referred to as ,F
(referred to as BT), 3 is a cathode ray tube that receives the boosted voltage, 4 is a rectifier consisting of a diode, etc., which rectifies the voltage obtained from the low voltage winding of Ilff2 through the cathode ray tube 3, 5
6 is a smoothing circuit consisting of a capacitor and a resistor, and 6 is a Zener diode as a drive output control circuit, which controls the operation of the high voltage drive circuit 1 in accordance with the output level of the smoothing circuit 5. Next, the operation will be explained. First, high voltage drive circuit 1
supplies a pulse of about 1000V to the primary winding of FBT2, and FBT2 supplies a high voltage of about 23kV from the secondary winding to the anode of the cathode ray tube. Furthermore, FIIT2 is 2
A low voltage winding that generates approximately 30V is wound on the next side.
The voltage of 30V obtained from this low voltage winding is rectified by a rectifier, and then smoothed by a smoothing circuit 5 consisting of a resistor and a capacitor. The voltage smoothed in this way is compared with the Zener voltage defined by the Zener diode 6, and if the smoothed voltage is higher than the Zener voltage,
High voltage drive circuit 1 to prevent line leakage from exceeding the standard value.
Stops pulse generation from .

[Problem to be solved by the invention]

Conventional X-ray protector devices are configured as described above, so if the Zener voltage set by the Zener diode varies, the detection accuracy will deteriorate, and the standard specifies the amount of X-ray leakage per hour. On the other hand, this conventional circuit has problems such as stopping the pulse output from the high voltage drive circuit 1 when the high voltage transiently increases, and the display screen on the cathode ray tube 3 immediately disappears. This invention was made to solve the above-mentioned problems by eliminating the Zener diode that deteriorates detection accuracy, and by eliminating the need for a Zener diode that degrades detection accuracy, it is possible to prevent the pulse output of the high voltage drive circuit from being incorrectly output due to a transient increase in high voltage. The purpose of this invention is to obtain an X-ray protector device that can reliably prevent the system from stopping due to

[Means to solve the problem]

The X-ray protector device according to the present invention compares the drive output control circuit that controls the operation of the high-voltage drive circuit with a voltage obtained by rectifying and smoothing the output voltage of the step-up transformer and a reference voltage according to the standard value of the amount of X-ray leakage. and a time monitoring control circuit that stops the output of the high voltage drive circuit when the rectified and smoothed voltage continuously exceeds the reference voltage.

[Effect]

The drive output control circuit in this invention detects whether the output level of a step-up transformer exceeds a reference value in a converter using a DC low voltage level, and a certain period of time has elapsed since the detected output exceeds a set level. When this occurs, the time monitoring control circuit outputs a control signal that stops the pulse output from the high voltage drive circuit, and on the other hand, under normal conditions where the level of the DC low voltage does not exceed the reference value, the high voltage that is permissible for the cathode ray tube is output. be able to supply

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a high voltage drive circuit, 2 is an FBT, 3 is a cathode ray tube, 4 is a rectifier, and 5 is a smoothing circuit, which are the same as those shown in FIG. On the other hand, 6A is a drive output control circuit, which connects a reference voltage generator 7 that outputs a reference voltage corresponding to the standard value of the amount of X-ray leakage of the cathode ray tube 3, a rectified and smoothed voltage obtained from the smoothing circuit 5, and the A comparator 8 compares the voltage with the reference voltage, and when it is determined based on the output of the comparator 8 that the rectified and smoothed voltage exceeds the reference voltage and that this state has continued for a set time, the high voltage drive circuit It consists of a time monitoring control circuit 9 that outputs a control signal to stop the pulse and pulse outputs. The time monitoring control circuit 9 may be a well-known computer that applies a software filter to the output data of the comparator 8 to generate the control signal, or a well-known hardware RC.
It consists of a combination of a delay circuit and a level detection circuit. Next, we will explain the operation. First, the operations up to the smoothing circuit 5 are exactly the same as those of the conventional circuit, so a redundant explanation will be omitted. Next, the reference voltage from the reference voltage generator 7 that is input to the comparator 8 is set to a voltage value specified by the standard. Therefore, normally the output of the comparator 8 is “L”
“This is the level. Some kind of abnormality occurs here, and the FB
When the high voltage output of T2 increases and the amount of X&I leakage increases, the output voltage of the smoothing circuit 5 simultaneously increases and becomes higher than the reference voltage. Therefore, the output of the comparator 8 becomes "H" level, and the time monitoring control circuit 9 detects an abnormality in the X-rays. By the way, due to the characteristics of the circuit, such a rise in high voltage output often occurs transiently, for example, at the moment when the screen changes from a dark state to a bright state.
It is not desirable to operate the protection circuit based on a 4% abnormality. Therefore, when the above-mentioned abnormality is detected, the time monitoring control circuit 9 monitors the output of the comparator 8 for a predefined period of time, for example, 1 second, and detects an X-ray abnormality only if the high voltage abnormality continues for 1 second or more. It is determined that this is the case, and a control signal is output to the high voltage drive circuit 1 to stop pulse generation. In the above embodiment, the reference voltage can be obtained by resistor division, and if this reference voltage is generated by digital/analog conversion by a microcomputer,
It is also possible to absorb variations in signals from each part of the circuit, making it possible to construct a more accurate X-ray protector device.

【Effect of the invention】

As described above, according to the present invention, the comparator detects whether the output level of the step-up transformer exceeds a reference value, and when the detected output exceeds the set level and a certain period of time has elapsed, time monitoring is performed. Since the control circuit is configured to stop the pulse output of the high-voltage drive circuit, the amount of leakage of X-rays from the cathode ray tube can be detected with high accuracy.
The anode of this cathode ray tube can be driven at an optimal high voltage, which has the effect of constantly displaying a high-brightness and sharp screen.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing an X-ray protector device according to an embodiment of the present invention, and FIG. 2 is a block connection diagram showing a conventional X-ray protector device. 1 is a high voltage drive circuit, 2 is a step-up transformer (FBT)
, 3 is a cathode ray tube, 6A is a drive output control circuit, 8 is a comparator, 9 is a time monitoring control circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A step-up transformer that boosts the output voltage of the high-voltage drive circuit and supplies it to the cathode ray tube, and a In an X-ray protector device equipped with a drive output control circuit that controls the output of the drive circuit, the drive output control circuit is configured to have a voltage obtained by rectifying and smoothing the output voltage of the step-up transformer, and a voltage corresponding to the preset standard value. A comparator that compares the voltage with a reference voltage, and a time monitoring control circuit that stops the output of the high voltage drive circuit when the rectified and smoothed voltage continuously exceeds the reference voltage. Characteristic X-ray protector device.