JPS6229099A - X-ray plant - Google Patents

Abstract

PURPOSE:To obtain an X-ray plant in which a tube voltage can be altered in a range sufficient and necessary for X-ray irradiation and the heating and noise at the time of seeing-through are reduced. CONSTITUTION:The primary winding 6a of a transformer 6, a capacitor 5 for resonance and an auxiliary resistor 30 are connected in series with each other to constitute a resonance circuit. Opening and closing control signals are applied to switches 31, 32 by a control means 19. A voltage induced across a secondary winding 6b by a series-resonance-type bridge inverter 21 is applied to an X-ray tube 9 through a rectification/smoothing means 23. In a mode, no driver pulse is sent to the switch 32, the switch is kept open, the voltage of the X-ray tube 9 goes high, and high-output and high-X-ray-quantity energy with a low pulsation ratio is obtained. in a seeing-through mode, the switch 31 is kept open, the operating frequency falls, the magnetic flux density of the core of the transformer 6 is lowered to reduce a noise due to magnetostriction, and a resonance current is decreased to suppress heating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a series resonant bridge inverter type X-ray apparatus.

[Technical background of the invention and its problems] Generally, in a series resonant bridge inverter type X-ray apparatus, an AC input voltage from an AC power source (generally a commercial power source) is rectified and smoothed to obtain a DC voltage. is converted into a predetermined AC voltage via a series resonant bridge inverter including a capacitor, and based on this, the DC voltage required for the exposure of the X-ray tube is generated.

By the way, in such X-ray equipment, two modes are generally used: @Shadow mode, which has a relatively heavy load for short time exposure, and fluoroscopy, which has a light load and long time exposure mode, but in both of these modes, There is a desire to vary the X-ray tube voltage over a wide range.

Conventionally, this request was met by using one series resonant bridge inverter and changing the ignition period of the driver pulses, but with this conventional method, the The basic drawback was that a wide tube voltage variable range could not be obtained. Moreover, with conventional devices, a large resonant current flows during fluoroscopy as well as during imaging, which adds to the problem of heat generation and noise caused by long-term use, and improvements to this are desired. Ta.

[Object of the Invention] The present invention has been made in view of the above circumstances, and is a novel method that can obtain a sufficient tube voltage variable range in any mode and can suppress heat generation and noise during fluoroscopy. The purpose is to provide X-ray equipment.

[Summary of the Invention] A summary of the present invention for achieving the above object is that, in a series resonant bridge inverter type X-ray apparatus, an auxiliary resistance circuit consisting of an auxiliary resistance and a first switch connected in parallel to each other is connected to a transformer. A second switch is connected in series with the primary winding and the resonant capacitor, and a second switch is connected in parallel with the primary winding to control driver pulses to the bridge portion and opening/closing of the first and second switches. This is done so that the current waveform and current value induced in the secondary winding of the transformer can be controlled by combination with the signal.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the apparatus shown in FIG. 1, 1 is a main power source that supplies alternating current voltage to the apparatus. 2 is four rectifiers 2a, 2b
, 2c and 2d are bridge-connected rectifying means, and 3 is a smoothing means for smoothing the voltage rectified by the rectifying means 2, in which two capacitors 3a and 3b are connected in series. 1 constitutes a rectifying/smoothing means 22.

6 is a transformer having a primary winding 6a and a secondary winding 6b,
The primary winding 6a of this transformer 6 and the capacitors 3a, 3
A resonance capacitor 5 and a rear auxiliary resistor 30 are connected in series between the connection point b and a resonance circuit. 16 is a first detection means (for example, current 1 to lance) that detects the current (primary current) flowing through the primary winding 6a of this transformer 6, and 17 is a means for converting the detected current of this first detection means 16 into a voltage signal. An I/V (current-voltage) conversion means is required.

20 is a bridge section for supplying the output from the first rectifying/smoothing means to the resonant circuit at a predetermined period;
Two diodes 13.1 each connected in a bridge
5 and two thyristors 12.14. Reference numeral 19 denotes a control means for sending driver pulses to both the thyristors 12 and 14 at a predetermined period to control the timing of applying DC voltage to the resonant circuit. A timer circuit (not shown) with a variable delay time is provided, which can apply an opening/closing control signal to the quick switches 31 and 32 after an arbitrary variable time has elapsed from the timing of the driver pulse applied. 3
Reference numerals 0 and 31 denote an auxiliary resistor and a first switch that are connected in parallel to each other to form an auxiliary resistor circuit, and are connected in series to the primary winding 6a and the resonant capacitor 5.

32 is a second winding provided in parallel with the primary winding 6a.
A switch (eg a bidirectional thyristor).

A series resonant bridge inverter 21 is configured by each of the above-mentioned elements.

7 is a bridge rectifier circuit that rectifies the voltage induced in the secondary winding 6b using four rectifiers; 8 is connected in parallel to the rectifier circuit 7 and smoothes the output from the circuit; The second rectifying/smoothing means 23 is composed of capacitors 7 and 8. 10a, 10b
is the DC output voltage (X
ray tube voltage) to the anode 9a and filament 9b of the X-ray tube 9.
11 is a second detection means for detecting the X-ray tube voltage;
Consisting of resistors 11a and 11b connected in series between the output terminal of the rectifying/smoothing means 23 and the ground, this resistor 1'la
, 11b detects the X-ray tube voltage, and the control means 19 (including a timer circuit) can be controlled based on the detection result. Each of these elements constitutes a high voltage side circuit.

Next, the operation of the device configured as described above will be explained.

First, a case will be described in which the closing phase of the first switch 31 when the second switch 32 is in the open state is varied.

When the first switch 31 is open, the primary winding 6a
The waveform of the primary current flowing through the auxiliary current shown in FIG.
) and (b), but the first
In the illustrated state, the value of the primary current is reduced by the amount that the auxiliary resistor 30 is inserted and connected to the resonant circuit. Therefore,
This primary current has a waveform as shown by the broken line in FIGS. 2 and 3.

By the way, to explain the waveforms shown in FIGS. 4(a) and 4(b), FIGS. 4(a) and 4(b) show that the waveforms shown in FIGS. It is a waveform diagram showing the relationship between current and gate pulses to these thyristors 12 and 14, in which (a)
(b) shows the current flowing when one thyristor 12 is turned on, and (b) shows the current waveform that flows when the other thyristor 14 is turned on. Note that the shaded area is a current that can flow in the opposite direction due to damped vibration of the resonant circuit.

On the other hand, when the first switch 31 is closed, the primary current flowing through the primary winding 6a bypasses the auxiliary resistor 30, so the waveform is as shown by the dashed line in FIGS. 2 and 3. Become. Therefore, when the first switch 31 is closed at an arbitrary time in the current waveform of one impulse (one peak), the current value of the primary current at that point is as shown by the solid line in FIGS. It suddenly changes and rises or falls (both are shaded areas).

That is, when the first switch 31 is not open, the primary current has the waveform shown by the broken line, but at any time the primary current changes to the waveform shown by the broken line.
When the switch 31 is opened, the subsequent waveform changes to the waveform shown by the dashed line.

A full bridge is formed by 15A. Therefore, the first
By making the closing position (timing T) of the switch 31 variable, the current value of the primary current (effective 1st cycle) can be changed to any value.
It can be set.

Next, we will discuss the function of the second switch 32 when the first switch 31 is in the open state.

When the second switch 32 is closed, the primary current flows bypassing the primary winding 6a, so the secondary winding 6 of the transformer 6
No current is induced in b. Therefore, when combined with the above-mentioned phenomenon of the primary current flowing through the primary winding 6a when the second switch 32 is open, that is, the first impulse (one peak) of the current waveform in the primary current occurs at any time. By closing the second switch 32, the output voltage (i.e., finally
This makes it possible to control the line tube voltage. In this case, since the auxiliary resistor 30 is connected in series with the second switch 32, this serves to reduce the current to a certain extent when the primary winding 6a is short-circuited, thereby preventing damage to the element.

As shown in FIG. 2, this is the driver pulse GP'1. sent from one of the control means. This can be achieved by delaying the OR gate signal of GP2 by a timer circuit for T seconds and using this as the control signal @ (opening/closing signal) GP3 of the second switch 32.

In addition, as in the previous) change of the X-ray tube voltage, the 1st and 2nd
This can be achieved by making the firing period of Zyristor '12.14 variable and by variably controlling the closing phases of both switches 31 and 32.

As described above, when using the present invention, it is necessary to appropriately set the value of the auxiliary resistor inserted in the resonant circuit, as well as the first. By controlling each phase of the second switches 31 and 32,
! This makes it possible to control the X-ray tube voltage in M-shadow and fluoroscopic modes.

That is, in the case of a short-time exposure mode called "bi-eki", the control means 19 outputs the driver pulse GP1. shown in FIG.
GP2 is sent to the first switch 31, but at this time, no driver pulse is sent to the second switch 32 and the switch 32 maintains the open state.
1 phase is the aforementioned driver pulse GP1. It will be controlled by the timing of GP2. The firing timing of thyristors 12 and 14 at this time is shown in Fig. 4 (a>
Since the X-ray tube voltage is set as short as , the X-ray tube voltage is high, and therefore, high output and high dose energy with low pulsation rate can be obtained.

On the other hand, in the case of a long-time exposure mode called fluoroscopy, the control means 19 outputs driver pulses GP1.
GP2 is sent to the second switch 32, but at this time, the first
Since no driver pulse is sent to the switch 31 and the switch 31 remains open, the resonant circuit is in a state in which only the auxiliary resistor 30 is inserted (which works to suppress the resonant current). Furthermore, the firing timing of the thyristors 12 and 14 at this time is set to be sufficiently long as shown in Fig. 4(b) compared to Fig. 4(a), so the operating frequency can be suppressed to a low level. become. Therefore,
In the perspective mode, the power supply voltage and operating frequency are lowered, which lowers the core magnetic flux density of the transformer 6 to suppress noise due to magnetostriction, and suppresses resonance current to prevent heat generation.

Next, another embodiment using a secondary power source will be briefly described with reference to FIG. 5.

Reference numeral 1' denotes a secondary power source that supplies AC voltage with lower power and lower voltage than the main power source 1 described above, and 22' denotes a secondary rectifying/smoothing means having the same configuration as the main rectifying/smoothing means 22 described above.
smoothing means, which consists of four rectifiers 2a', 2b'
, 2c', 2d' are bridge-connected auxiliary rectifying means 2', and two capacitors 3a'.
, 3b' are connected in series. Reference numeral 4 denotes a changeover switch for switching between the main rectification/smoothing means 22 and the secondary rectification/smoothing means 22'.
This is the same as in the first embodiment except for the difference in voltage.

The present invention is not limited to the embodiments described above,
Various modifications can be made within the scope of the gist. For example, in the illustrated embodiment, the bridge portion is a half bridge, but it may be a full bridge, and the first and second switches 31 and 32 may be configured as one switch, and the opposite side of the common connection side may be configured as a full bridge. The sides may be used as a changeover switch to switch between them.

In addition, the auxiliary resistor 30 may be configured to be variable, or
In the case of the second embodiment, which is configured to switch between and use AC power supplies with different performances, a large variable range for the X-ray tube voltage is obtained. Moreover, in this case, it goes without saying that better results can be obtained by linking the switching of the power source with the switching control of both the switches 31 and 32 described above.

[Effects of the Invention] According to the present invention described in detail above, an X-ray apparatus is provided which can obtain a sufficient tube voltage variable range even in the imaging mode and the fluoroscopy mode, and can suppress heat generation and noise in the fluoroscopy mode. can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the X-ray apparatus of the present invention, FIGS. 2 and 3 are waveform diagrams showing the relationship between the primary current and the timing of driver pulses, and FIGS. b) is a waveform diagram showing the primary current of the thyristors 12 and 14 and the timing of the gate pulse, respectively, and FIG. 5 is a circuit diagram of the second embodiment of the present invention. 1... AC power supply, 5... Resonance capacitor, 6...
...Transformer, 6a...Primary winding, 6b...Secondary winding, 9...XIW tube, 11...Second detection means, 12.14...Thyristor, 16... -First detection means 19...control means, 20
...Bridge portion, 22...Second rectification/smoothing means, 30...Auxiliary resistor, 31...First switch, 32
...Second switch. Agent Patent Attorney Norihiro Chika Kenshu Daigo Norifu Figure 3 Figure 4 (G) (b); P2i Figure 5 /21

Claims (2)

[Claims] (1) The DC voltage is applied at a predetermined period to a resonant circuit including a rectifying and smoothing means for rectifying and smoothing an input AC voltage to obtain a DC voltage, a primary winding of a transformer, and a resonant capacitor. A series circuit that has a bridge section and a control means that sends a driver pulse to the bridge section to control the current supply timing, and obtains an X-ray tube voltage based on the voltage of the transformer induced by the current flowing in the primary winding. In the resonant bridge inverter type X-ray apparatus, an auxiliary resistance circuit consisting of an auxiliary resistor and a first switch connected in parallel with each other is connected in series with the primary winding of the transformer and the resonance capacitor, and , a second switch is connected in parallel with the primary winding, and a timer circuit with a variable delay time is configured to apply an opening/closing signal to the first and second switches after an arbitrary period of time has elapsed from the timing of the driver pulse. A current waveform and a current value generated on the secondary winding side of the transformer by a combination of a driver pulse to the bridge section and an opening/closing control signal to the first and second switches, the current waveform and current value being attached to the control means. An X-ray apparatus characterized in that it is configured to control. (2) The X-ray apparatus according to claim 1, wherein the rectifying and smoothing means is constituted by two or more types of rectifying and smoothing means having different performances, and is connected to the resonant circuit via a power supply switching means.