JP2616531B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus, in particular, a high frequency circuit (inverter circuit) connected to the primary side of a heating transformer and controlling the input voltage of the high frequency circuit to heat the filament at a predetermined heating set value. The present invention relates to an X-ray tube filament heating circuit for heating and switching a filament connected to the secondary side of the heating transformer.

[0002]

2. Description of the Related Art A heating circuit for an X-ray tube filament of this type compares a heating transformer, an inverter circuit connected to the primary side thereof, an actual measured filament current value and a heating set value signal, and sets an actual measured value. Control means for controlling the input voltage of the inverter circuit so as to obtain a value, and means for switching a filament connected to the secondary side of the heating transformer. The filament is switched to an X-ray high voltage device. X-ray tube selection means for switching X-ray tubes, or
This is performed by focus switching means for switching between the large focus filament and the small focus filament.

An X-ray apparatus provided with an X-ray tube filament heating circuit having the above configuration will be described with reference to FIG. 1 showing an embodiment of the present invention. In FIG. 1, X-ray tubes (11) and (12) are provided with small focal filaments (69) and (71) and large focal filaments (70) and (72), respectively.

A filament heating circuit (50) rectifies an AC output from an AC power supply (51) by a rectifier (52),
The signal is input to the smoothing capacitor (54) through R (53). SC
R (53) controls the phase so that the voltage between (a) and (b) in FIG. 1 is a constant voltage. This output is a smoothing capacitor (54)
The voltage at points (a) and (b) is smoothed by (57) and the resistance (5
5a), (55b) and (55c), (55d)
Is input to The voltage at point (d) is added to the voltage at point (b), and by adding this voltage, the voltage at point (a) is
The differential amplifier circuit (56) and the SCR gate circuit (58) control the SCR (53) so that the voltage becomes higher than the voltage at the point (b) by about 30 V.

The output of the filament current setting circuit (61) is
The signal is input to the non-inverting input terminal of the operational amplifier (62). The output of the filament current measurement circuit (63) is input to the inverting input terminal of the operational amplifier (62), and the operational amplifier (62) functions as a comparator. If the input voltage from the filament current setting circuit (61) is at least slightly higher than the input voltage of the filament current measurement circuit (63), the operational amplifier (62) outputs High, and the transistor ( Turn on 59). Then, the DC output voltage of the transistor (59) increases. Thus, the filament current becomes a value corresponding to the output of the filament current setting circuit (61).

[0006] The DC output of the transistor (59) is switched by the switch elements (4a) to (4d) constituting the inverter circuit (the switch elements (4a) and (4d) and the switch element (4b),
(4c) turns on and off alternately) is converted to AC output,
It is input to the focus switching relay circuit (65). The signal from the focus switching control circuit (66) is used to
At 5), the focal point is switched to the large focal point or the small focal point side, passes through the filament transformer (heating transformer) (3) or (2), passes through the high-pressure switch (67) (68), and the X-ray tubes (11), ( 12) is added to the filaments (69) (70) (71) (72).

When a signal from the X-ray tube selector (74) is given to the X-ray tube switching control circuit (73), the high-voltage switchers (67) (6)
8) The relays (75) and (76) for ON / OFF control are selectively operated, and one of the X-ray tubes (11) and (12) is selected, and the filament of the selected X-ray tube is changed to the filament. Transformer (2)
Connected to (3).

[0008]

In the X-ray apparatus having the above-mentioned conventional X-ray tube filament heating circuit, when the filament is switched by the X-ray tube selector (74) or the focus switching control circuit (66), a high pressure is applied. Due to the operation delay of the switching device or the focus switching relay, the secondary side of the heating transformer is opened, and when the switched filament is connected to the secondary side of the heating transformer, a large current temporarily flows through the filament and flashes. There's a problem.

That is, when the large focus of the X-ray tube (11) is selected, the set value of the filament current is output from the filament current setting circuit (61), and the X-ray tube is selected while the filament (70) is being heated. X-ray tube selection in the vessel (74)
When the X-ray tube (12) is changed from (11), the relay (75) is turned off by the X-ray tube switching control circuit (73), and the contact of the high voltage switch (67) is separated. That is, the secondary side of the filament transformer (3) is opened, and there is no load. Then, no current flows on the secondary side of the filament transformer (3), and the output signal (feedback signal) from the filament current measurement circuit (63) becomes zero.

Therefore, the input voltage of the inverting input of the operational amplifier (62) becomes zero, and the filament current setting circuit (61)
The operational amplifier (62)
Outputs High, turns on the transistor (59) through the transistor base control circuit (64), and sets the smoothing capacitor (5
7) The voltage rises. Since it takes a relatively long time (about 1 second) from the separation of the contact of the high-voltage switch (67) to the contact of the high-voltage switch (68), the charging voltage of the smoothing capacitor (57) is controlled by the filament control circuit. It easily rises to the maximum of (50).

Thereafter, when the contact point of the high voltage switch (68) comes into contact, the charging voltage of the smoothing capacitor (57), which has risen to the maximum value, is switched by the switch elements (4a) to (4d), and the focus switching relay circuit ( 65), filament transformer (3) or
(2) The filament (71) passes through the contacts of the high pressure switch (68).
Or added to (72). At this time, a large current temporarily flows through the filament. The output signal from the filament current measurement circuit (63) also has a large value, and the input voltage of the inverting input terminal of the operational amplifier (62) becomes higher than the non-inverting input terminal voltage of the filament current setting circuit (61). Then, the output of the operational amplifier (62) becomes Low, the transistor (59) is turned off through the transistor base control circuit (64), and the voltage of the smoothing capacitor (57) falls.

Finally, a filament current measuring circuit (63)
The output signal falls to a value corresponding to the output of the filament current setting circuit (61) and converges to a constant value. As a result, every time the X-ray tube is switched, a large current is temporarily supplied to the filament to flash the filament, and the sublimation of the filament is accelerated, and the life of the X-ray tube is shortened.

FIG. 3 is a waveform diagram of each part in the above, and T
₁ X-ray tube is selected, closing time, [Delta] T of the contacts of the open time, T ₂ is a high-pressure switching device (68) of the contacts of the high-pressure switching unit (67) is contact opening of the high-pressure switching unit (67) a time lag between the contacts of the high-pressure switching unit (68) is closed after the setting of the filament current for the filaments is switched, T ₁
It takes place between the the T _2.

In the above, the case where the filament connected to the secondary side of the filament transformer is switched by selecting the X-ray tube has been described. However, by switching the focus, the filament is changed from the large focal filament to the small focal filament or vice versa. A similar phenomenon occurs when switching. In FIG. 1, (13) is an X-ray high-voltage device, which comprises a high-voltage transformer (7), a rectifier (8), and a smoothing capacitor (10).

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an X-ray apparatus having an X-ray tube filament heating circuit which does not cause a large current to flow temporarily to the X-ray tube filament when the filament is switched and does not flash. And

[0016]

In order to achieve the above object, the present invention provides a heating set value signal for a high frequency circuit of a filament heating circuit prior to switching of a filament.
A control circuit is provided for switching to a low level and then switching the filament and switching a heating set value signal to a predetermined set value at a predetermined timing thereafter.

[0017]

The control circuit lowers the heating set value signal for the high frequency circuit to a lower level (for example, zero level) lower than a predetermined heating set value signal before switching the filament. As a result, the charging voltage of the high-frequency circuit decreases, and after a predetermined time has elapsed, the charging voltage becomes zero. In this state,
The control circuit operates the X-ray tube switch or the focus switch. At this time, due to the operation delay of the switching device, the secondary side of the heating transformer is separated and no load is applied, and the heating set value signal is zero even if the feedback signal disappears, so that the charging voltage does not increase.

After that, even if the secondary side of the heating transformer is connected to another filament, the filament starts oscillating heating at a high frequency from a low charging voltage, and is finally heated by a given predetermined heating set value signal. Become. As a result, even if the filament is switched by switching the X-ray tube or the focus, the filament is not flashed each time, and sublimation of the filament can be prevented, and the life can be prevented from being shortened.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the figure, (1) is a control circuit which is constituted by a microcomputer, and supplies a predetermined heating set value signal and a low level set value signal such as a zero level at the time of filament switching to a filament current setting circuit (61). At the same time, the focus switching control circuit (66) and the X-ray tube selector (74) are controlled to switch the filaments connected to the filament transformers (2) and (3). In the figure, the control circuit (1)
Other than that has been described in the section of the prior art, the description is omitted.

Next, the large focus of the X-ray tube (11) is selected,
The filament current setting value is
In the case where the X-ray tube selector (74) is used to switch from the X-ray tube (11) to the X-ray tube (12) while the filament (70) is being output from the (1) and is being heated, the control circuit Fig. 2 shows the operation of (1)
This will be described in relation to the waveform diagram of FIG.

Prior to sending a control signal (X-ray tube selection signal) to the X-ray tube selector (74), the control circuit (1) performs the operation shown in FIG.
_At the time of ₁ , the X-ray tube (1) of the filament current setting circuit (61)
The predetermined heating setting signal for 1) is set to zero. As a result, the output of the filament current setting circuit (61) becomes zero, so the non-inverting input terminal of the operational amplifier (62) becomes zero, the operational amplifier (62) outputs Low, and through the transistor base control circuit (64), The transistor (59) is turned off. The voltage of the smoothing capacitor (57) falls, and after a predetermined time, the voltage of the smoothing capacitor (57) falls to a low level of zero level.

In this state, the selection of the X-ray tube is changed from the X-ray tube (11) to the X-ray tube (12) by the X-ray tube selector (74) by the control signal from the control circuit (1). The relay (75) is turned off by the X-ray tube switching control circuit (73), and the contact of the high voltage switch (67) is
Away at the time of the T _1, no current flows to the secondary side of the filament transformer (3). Filament current measurement circuit (6
Even if the input voltage from (3) becomes zero, the non-inverting input terminal of the operational amplifier (62) is zero.
The output of 2) does not become High. The transistor (59) remains off, and the voltage of the smoothing capacitor (57) remains low.

The closed contacts of the high-pressure switching device (68) from T ₁ at time ΔT elapsed T _2, the control circuit (1) at time t ₂ it than Δt elapsed, the filament current setting circuit (61 )
Is set to a predetermined heating set value signal I for the X-ray tube (12).
Set to s. Therefore, even if the contacts of the high-voltage switch (68) come into contact, the charging of the smoothing capacitor (57) starts from a low level, rises to a value corresponding to the output of the filament current setting circuit (61), and becomes a constant value. It converges and no longer flashes the filament each time the filament is switched, preventing filament sublimation.

In the embodiment, the high-frequency circuit (inverter circuit) is constituted by an FET, but may be constituted by another switching element such as a transistor or a thyristor.
Further, time t ₂ to switch the filament current setting value to a predetermined heating setting value may be changed depending on the voltage of the smoothing capacitor (57).

[0025]

According to the present invention, since the filament is not flushed when the filament connected to the X-ray tube filament heating circuit is switched, the sublimation of the filament is prevented and the life of the X-ray tube can be extended. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a waveform diagram of each part of the block diagram of FIG.

FIG. 3 is a waveform diagram for explaining the operation of a conventional X-ray tube filament heating circuit.

[Explanation of symbols]

(1): Control circuit (11), (12): X-ray tube (69), (70), (71), (72): Filament (13): X-ray high-voltage device (7): High-voltage transformer (8) Rectifier (10) Smoothing capacitor (50): Filament heating circuit (2), (3) Filament (heating) transformer (4a), (4b), (4c), (4d): Inverter circuit Constituting switching elements (59): Transistor (61): Filament current setting circuit (62): Operational amplifier (comparator) (63): Filament current measurement circuit (64): Transistor base control circuit (65): Focus switching relay circuit (66): Focus switching control circuit (67), (68): High voltage switch (73): X-ray tube switching control circuit (74): X-ray tube selector (75), (76): Relay

Claims (1)

(57) [Claims] A high-frequency circuit is connected to a primary side of a heating transformer in which a filament is connected to a secondary side. The high-frequency circuit compares a filament current measured value with a predetermined heating set value signal. An X-ray apparatus having a filament heating circuit configured to control an input voltage of the high-frequency circuit so as to switch a filament connected to a secondary side of the heating transformer, prior to switching the filament, An X-ray apparatus comprising: a control circuit that switches a heating set value signal to a low level, and then switches a filament and a heating set value signal to a predetermined heating set value signal at a predetermined timing thereafter.