JPH0665188B2 - Filament heating circuit for vacuum tube for high voltage control of X-ray equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filament heating circuit for a high voltage control vacuum tube for controlling the tube voltage of an X-ray tube in an X-ray apparatus.

BACKGROUND OF THE INVENTION An X-ray apparatus to which a conventional circuit of this type is applied is shown in FIG. In FIG. 3, the sliding transformer 1 is for adjusting the primary voltage applied to the high voltage transformer 2, and the high voltage generated on the secondary side of the high voltage transformer 2 is rectified by the rectifiers 3a, 3b.
After being rectified by, the high voltage capacitors 4a and 4b are used for smoothing, and there are bias circuits 6a and 6b for varying the grid voltage of the high voltage control vacuum tubes, here high voltage quadrupole vacuum tubes (hereinafter referred to as tetrode tubes) 5a and 5b. By controlling, an arbitrary voltage is applied to the X-ray tube 7. The X-ray tube voltage control circuit 8 is set by the X-ray condition setter 18, and sets the set X-ray tube voltage data output from the CPU 9 to the digital / analog converter 10.
The set X-ray tube voltage signal converted into an analog quantity by a and the actual X-ray tube voltage signal extracted by the voltage divider 11 are compared and controlled, and are activated when the X-ray radiation switch 17 is closed. The tetrode tubes 5a and 5b are operated so that the set X-ray tube voltage is applied to the X-ray tube 7 during the time set by the time delay circuit 12. Heating transformer 13a
Is for applying a voltage to the filament of the X-ray tube 7, and converts the set X-ray tube current data from the CPU 9 set by the X-ray condition setter 18 into an analog amount by the digital / analog converter 10b. The filament application voltage is varied by the heating circuit 14 with the set X-ray tube current signal. The switch 15 is turned on by a relay circuit (not shown) when the X-ray radiation preparation switch 16 is closed, and applies the output voltage of the sliding transformer 1 to the primary side of the high voltage transformer 2.

The filament heating transformers 13b, 13c that compose the filament heating circuit of the tetrode tubes 5a, 5b are directly connected to the input side of the sliding transformer 1, and the rated voltage is always applied to the tetrode tube filament after the power is turned on. It is applying.

Next, the operation of the above device will be described. In the state where the power source of the apparatus is just turned on (steady state), the switch 15 is opened and the high voltage transformer 2 is not supplied with power source. The tetrode tubes 5a, 5b are cut off by the grid bias circuits 6a, 6b, but the rated voltage is applied to the filaments by the heating transformers 13b, 13c. On the other hand, the filament of the X-ray tube 7 has a heating transformer 13
A small voltage is applied by a compared to the rated voltage. This is because it takes time if the filament temperature of the X-ray tube 7 reaches a temperature at which a prescribed tube current can flow in a completely cooled state.

Switch when the X-ray emission preparation switch 16 is closed
15, the high voltage DC is applied to the tetrode tubes 5a, 5b through the high voltage transformer 2, the rectifiers 3a, 3b, and the high voltage capacitors 4a, 4b. At this point, CPU9 sends X-ray condition setter 18
A signal corresponding to the X-ray tube voltage value set in advance is output to the X-ray tube voltage control circuit 8 through the D / A converter 10a, but since there is no X-ray emission signal from the time delay circuit 12, the Load tubes 5a and 5b are still in the cut-off state, X
No voltage is applied to the wire tube 7. At the same time, a signal corresponding to the X-ray tube current value set by the X-ray condition setter 18 from the CPU 9 is output to the heating circuit 14 via the D / A converter 10b, and the heating transformer 13a sets the set X-ray tube. Application of the filament voltage according to the current value, that is, filament heating of the X-ray tube 7 is started.

Then, when the X-ray radiation switch 17 is closed, the X-ray radiation signal is output from the time-limit circuit 12 to the X-ray tube voltage control circuit 8, and the tetrode tubes 5a and 5b become conductive.
A set voltage is applied to the X-ray tube 7, and X-rays are emitted according to the set tube voltage and tube current in combination with the filament heating of the X-ray tube 7. The emission of X-rays is stopped by the cut-off state of the tetrode tubes 5a, 5b again by the time delay circuit 12 according to the time preset by the X-ray condition setter 18. Applying voltage to the tetrode tubes 5a and 5b
The switch 15 is opened by opening the X-ray radiation preparation switch 16.
Is opened and shut off. At the same time, the filament voltage of the X-ray tube 7 also returns to a minute value.

As can be seen from the above description, the conventional filament heating circuit for the high-voltage control vacuum tube is such that the high-voltage control vacuum tube (the tetrode tubes 5a,
In b), the rated voltage of the filament was always applied. For this reason, there has been a problem that the life of the filament, and eventually the life of the high-voltage controlling vacuum tube itself is shortened, and in particular, it is remarkably shortened by forgetting to turn off the power supply after using the X-ray apparatus.

[Object of the Invention] The present invention has been made to solve the above problems, and provides a filament heating circuit for a high-voltage control vacuum tube, which can extend the life of the high-voltage control vacuum tube. With the goal.

[Summary of the Invention] The present invention focuses on the fact that the time of actually applying the tube voltage to the X-ray tube is only a very short time during the filament rated voltage application time of the high-voltage control vacuum tube in the conventional circuit. This is done so that a minute voltage is applied to the filament, except for the minimum time required when the tube voltage is actually applied, to achieve the above object.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings. First
The figure is a circuit diagram showing an example of an X-ray apparatus to which the circuit of the present invention is applied. In the figure, 10c is a digital / analog converter for converting a signal from the CPU 9 into an analog signal, and 19 is this converter 10c.
Is a heating circuit for applying a voltage to the filaments of the tetrode tubes 5a and 5b by a signal from the heating circuit to heat the filaments. In this case, the signal sent from the CPU 9 to the digital / analog converter 10c is applied to the filaments of the tetrode tubes 5a, 5b by applying a minute voltage compared to the rated voltage from the time the X-ray device power is turned on, and at least the X-ray The content of applying a voltage according to the X-ray condition preset by the X-ray condition setter 18 during a period from a predetermined time (idling time) before applying the tube voltage of the tube 7 to the end of the application. It is a signal.

The applied voltage required for the filaments of the tetrode tubes 5a, 5b depends on the tube current as does the filament applied voltage of the X-ray tube 7. Therefore, here, a signal from the CPU 9 for applying the filament voltage of the X-ray tube 7 is commonly used to control the filament application voltage of the tetrode tubes 5a and 5b. This allows the tetrode tube
An optimum voltage is applied to the filaments 5a and 5b in order to obtain the X-ray tube current set by the X-ray condition setter 18.

In addition, in FIG. 1, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions.

FIG. 2 is a time chart showing the operation of such an X-ray apparatus, and illustrates an example in which the X-ray condition setting is changed at point A in the figure (tube voltage is high, tube current is small, radiation time is short). is doing.

Next, the operation of the above-described circuit of the present invention will be described. First, when the X-ray device power is turned on but the X-ray tube voltage is not applied (steady state), the filaments of the tetrode tubes 5a and 5b are heated in the same manner as the filaments of the X-ray tube 7. A small voltage is applied by the transformers 13b and 13c as compared with the rated voltage. This is because it takes time for the tetrode tube filament to reach the temperature at which the set X-ray tube current can flow from the completely cooled state, and the inrush current that occurs when a voltage is rapidly applied from the cooled state. By tetrode tube
This is to prevent the life of 5a and 5b from being shortened.

When the X-ray emission preparation switch 16 is closed from such a state, a signal (setting X-ray tube current data) corresponding to the X-ray tube current value preset by the X-ray condition setter 18 at that time is output from the CPU 9. Is output. This signal is given to the heating circuit 19 through the digital / analog converter 10c, and the heating transformer 13b starts the application of the tetrode tube filament voltage according to the set X-ray tube current value, and the idling state is set.

The X-ray emission preparation switch 16 closes the X-ray emission switch 17 for a fixed time thereafter, that is, applies a tube voltage (X-ray emission).
After that, the filament application voltage of the tetrode tubes 5a and 5b returns to a minute voltage.

[Effects of the Invention] As described above, according to the present invention, the voltage applied to the filament of the high-voltage control vacuum tube is kept constant at a very small voltage in the steady state of the X-ray apparatus. Can be extended to. In particular, shortening the life of the vacuum tube by forgetting to turn off the power after using the X-ray apparatus is a very large loss, but the present invention has an effect that the loss can be minimized even in such a case. .

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of an X-ray device to which the circuit of the present invention is applied, FIG. 2 is a time chart showing the operation of the device,
FIG. 3 is a circuit diagram of an X-ray apparatus having a conventional circuit. 2 ... High-voltage transformer, 5a, 5b ... Tetrode tube,
7 ... X-ray tube, 9 ... CPU, 10b, 10c ... Digital / analog converter, 13a-13c ... Heating transformer, 14, 19 ...
Circuit for heating, 15 ... Switch, 16 ... X-ray radiation preparation switch, 17 ... X-ray radiation switch, 18 ... X-ray condition setter.

Claims (1)

[Claims] 1. An X-ray device for controlling the tube voltage of the X-ray tube with a high-voltage control vacuum tube provided between a high-voltage transformer and the X-ray tube, wherein X is applied to a filament of the high-voltage control vacuum tube. A minute voltage is applied compared to the rated voltage after the power supply of the X-ray device is turned on, and at least the time from a certain time before the tube voltage is applied to the X-ray tube to the end of the application depends on the preset X-ray condition. A filament heating circuit for a high-voltage control vacuum tube of an X-ray apparatus, comprising: an applied voltage control means for applying the applied voltage.