JPH04229599A - X-ray generating device - Google Patents

Abstract

PURPOSE:To miniaturize and lighten a transformer and a rectification circuit by making an action frequency a high frequency wave in a X-ray generation device in which voltage supplied from a power supply is converted into an A.C. voltage having a desired high frequency and then is stepped up with a transformer, and high voltage is rectified to be applied to a X-ray tube. CONSTITUTION:High-voltage transformers 131-13n are divided into plural (e.g. n) transformers having small quantity (the number of winding of primary winding is same and the number of winding of secondary winding is made 1/n), primary sides are parallelly connected to the output of a frequency converter respectively, and rectification results of the output of respective transformers are added in series to be applied to a X-ray tube. This can lessen secondary inductance of respective transformers 131-13n to 1/n<2>, consequently the output frequency upper limit of the frequency converter 12 become (n) times, enabling sharp miniaturization and lightening of a device including the frequency converter 12.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention boosts an input voltage to a high-frequency, high-voltage AC voltage using an inverter, high-voltage transformer, etc., rectifies the boosted output, and applies it to an X-ray tube. The present invention relates to an X-ray generator that generates rays.

0002

[Prior Art] A conventional example of such an X-ray generator is shown in Figure 1.
7. Here, a frequency converter 2 that converts the frequency of the voltage supplied from the input power source (AC power source) 1 is connected to the primary side of the high-voltage transformer 3 in order to improve performance and reduce the size and weight of the device. Ru. A frequency converter consists of a rectifier circuit, a filter, a capacitor, and an inverter to convert the obtained direct current into alternating current at the required frequency. Frequency converter 2
The output voltage of the high voltage transformer 3 is stepped up, and the output voltage of the high voltage transformer 3 is rectified by the high voltage rectifier circuit 4. A rectified output from the high voltage rectifier circuit 4 is applied between the anode and cathode of an X-ray tube 5 serving as an X-ray source. The frequency converter 2 converts the frequency fo (commercial frequency, generally 50/60 Hz) of the input AC voltage to a higher frequency f1, and supplies the frequency f1 to the high voltage transformer 3.

As the output frequency f1 of the frequency converter 2 increases, the frequency converter 2 and the high voltage transformer 3 are made smaller and smaller.
It can be made lighter. This is because the impedance of a coil or capacitor generally changes depending on the frequency, so if the frequency is raised, the capacitance or inductance can be reduced by that much if the impedance remains constant. Since capacitance and inductance are proportional to the shapes of coils and capacitors, the frequency converter 2 and high voltage transformer 3 using coils and capacitors can be made smaller and lighter as the frequency increases.

However, in such an X-ray generator, the output frequency f1 of the frequency converter 2 cannot be made infinitely high, and its upper limit is determined by the characteristics of the high voltage transformer 3 for the following reasons. It will be done.

FIG. 18 is an equivalent circuit of the high voltage transformer 3 shown in FIG. 17, looking at the secondary side. L1, L2, and M are the primary inductance, secondary inductance, and mutual inductance of the high voltage transformer 3, respectively. N is the turns ratio (number of secondary windings/number of primary windings). Here, in the high voltage transformer 3, the number of turns of the secondary winding is extremely large compared to that of the primary winding so as to output a high voltage, and the secondary inductance L2 has a considerably large value compared to the primary inductance L1 and the mutual inductance M. It has become. Therefore, the inductance of the secondary side of the high voltage transformer 3 is exactly as shown in Figure 18.
As shown in , L2-M, but M can be ignored and considered as only the secondary inductance L2, and in the following explanation, the inductance of the secondary side portion is assumed to be only L2. Also, let the equivalent impedance of the X-ray tube 5 be Rx, and the X-ray tube 5
Let Ex be the terminal voltage of . Since the rectifier circuit 4 is not related to the magnitude of the terminal voltage Ex, if it is simply considered, the secondary inductance L2 is connected in series with the impedance Rx.

When the output frequency of the frequency converter 2 is f1, the impedance Z2 due to the secondary inductance L2 is
is expressed as follows, and it can be seen that it is proportional to the output frequency of the frequency converter 2.

[0007]Z2=2π・f1・L2...(
1) Furthermore, the voltage Ex applied to the X-ray tube 5 is expressed as follows.

Ex=E2・Rx/(Rx+Z2)...(2) Here, (L1-M)/N2 in FIG. 18 can be omitted since N is extremely large, and if the output of the frequency converter 2 is E1, then , E2 becomes as follows.

E2=E1・N
...(3) From equations (1) and (2), frequency converter 2
When the output frequency f1 becomes higher, the impedance Z2 becomes higher and the voltage Ex applied to the X-ray tube 5 lowers, which is a contradiction. Therefore, the output frequency f1 of the conventional frequency converter 2 is limited to about 10 KHz,
It was not possible to achieve a higher frequency. When the frequency is several tens of kilohertz, transformers and rectifier circuits can be made small and
Not only was it impossible to reduce the weight, but there was also the problem that noise was generated from the transformer.

In this way, the output frequency f of the frequency converter 2
1 can only be increased to about 10 KHz because the secondary inductance L2 of the high voltage transformer 3 is extremely large.

[0011] As an improvement measure, FIGS. 19 and 20
It has been considered to modify the primary side of the high voltage transformer 3 as shown in FIG. In the circuit shown in FIG. 19, a capacitor C1 is connected in series with the primary winding of the high voltage transformer 3 to cause series resonance on the primary side. In the circuit shown in FIG. 20, a capacitor C2 is connected in parallel to the primary winding of the high voltage transformer 3 to cause parallel resonance on the primary side. However, in any of these circuits, it is equivalent to increasing the voltage on the primary side of the high voltage transformer 3 through series resonance or parallel resonance. Since the inductance L1 on the primary side is originally small and the resonant voltage is also small, the same X as before connecting the resonant circuit
In order to obtain the voltage applied to the wire tube 5, the output frequency of the frequency converter 2 could only be made several times higher than before connecting the resonant circuit.

[0012] Also, US Pat. No. 4,545,005 (
In order to increase the resonant frequency of the high voltage transformer, the secondary winding of the high voltage transformer is divided into multiple windings, each secondary winding is connected to each rectifier circuit, and the output of these rectifier circuits is are connected in series and applied to the X-ray tube. However, this means that the primary winding of the transformer is not divided, so it can be considered as one high-voltage transformer, and the output of one frequency converter is simply connected to one high-voltage transformer. , similar to the conventional example in Fig. 17, the frequency increase is several KH.
z was the limit.

[0013] Also, US Pat. No. 4,317,039 (
Romandi) is equipped with multiple frequency converters and multiple high voltage transformers, but the purpose of this conventional example was to reduce ripple, and this was achieved by making the phases of the multiple frequency converters different. has achieved its purpose. Therefore, in this reference there is no interest in increasing the frequency of the inverter, and the frequency range is stated to be an intermediate frequency range, approximately 6-7 KHz.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned circumstances, and its purpose is to convert a power supply voltage into a desired high-frequency AC voltage using an inverter, and then convert the AC voltage into a desired high-frequency AC voltage. In an X-ray generator that boosts the voltage with a transformer, rectifies the boosted voltage, and applies it to the X-ray tube, the purpose is to make the transformer and rectifier circuit smaller and lighter by increasing the frequency of the AC voltage.

[0015]

[Means for Solving the Problems] An X-ray generator according to the present invention includes a plurality of high voltage generating units whose input sides are connected to a power source and whose output sides are connected to each other in series, and each high voltage generating unit has an input voltage. It includes means for converting into an alternating current voltage of a predetermined frequency, a plurality of transformers connected to the output of the converter means for boosting the alternating current voltage, and a means for rectifying the outputs of the plurality of transformers.

[0016]

[Operation] According to the X-ray generator according to the present invention, the transformer for boosting the alternating current voltage is divided into a plurality of small-capacity transformers with a small number of secondary windings, and the output of these transformers is By adding the rectification results and applying the addition result to the X-ray tube, the frequency of the AC voltage can be increased without reducing the applied voltage.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an X-ray generator according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the first embodiment. An AC power source 11 as an input power source is connected to an input end of a frequency converter 12. Frequency converter 1
2 is a frequency converter that increases the frequency of the input AC voltage. A plurality of high voltage transformers 1 are connected to the output end of the frequency converter 12.
3i (i=1 to n) are connected in parallel. That is,
One end of the primary winding of each high voltage transformer 13i is commonly connected to the negative output end of the frequency converter 12, and the other end of the primary winding of each high voltage transformer 13i is commonly connected to the other output end of the frequency converter 12. Ru. The secondary windings of the high voltage transformer 13i are each connected to a high voltage rectifier circuit 14i. High voltage rectifier circuit 1
The outputs of 4i are connected in series, and the addition result of the series connection is applied to the X-ray tube 15. That is, high voltage rectifier circuit 1
41 is connected to the anode of the X-ray tube 15, and the negative output ends of the high voltage rectifier circuits 141 to 14n-1 are connected to the positive output ends of the high voltage rectifier circuits 142 to 14n. The negative output end of 14n is connected to the cathode of X-ray tube 15.

Here, in order to simplify the explanation, the number of turns of the primary winding of each high voltage transformer 13i is the same as the number of turns of the primary winding of one high voltage transformer 3 of the conventional example shown in FIG. The number of turns of the secondary winding of the high voltage transformer 13i is 1/n of that of one high voltage transformer 3.

Next, the operation of the first embodiment will be explained. Figure 2
17 is an equivalent circuit diagram omitting the rectifier circuit of the secondary side portion (portion from the secondary winding to the X-ray tube) of the conventional transformer 3, and similarly, FIG. 3 shows the equivalent circuit diagram of the first implementation of FIG. 1. Example transformer 13
An equivalent circuit diagram of the secondary side part of i is shown. Generally, in the high voltage transformers 3 and 13i, the number of turns of the secondary winding is much larger than that of the primary winding, and the secondary inductance L2 has a large value. Therefore, the equivalent circuit on the secondary side of the high voltage transformer is represented only by the secondary inductance L2, as shown in FIGS. 2 and 3. Frequency converters generally operate with on/off switching, so the output is a square wave. Therefore, E2 is also represented by a square wave pulse.

In FIG. 2, if L2/Rx=τa, the voltage Ex applied to the X-ray tube 5 can be expressed as a general expression with a time constant τa as shown in curve A of FIG. rise to The reference t=0 of time t in FIG. 4 is the rising timing of E2.

Ex=E2(1-e-t/τa)...(4) Therefore, if the pulse width of E2 is τa, the applied voltage Ex will reach the maximum value (0.63・τa) when t=τa. E2).

On the other hand, in the embodiment shown in FIG. 1, the number of secondary windings of each high voltage transformer 13i is 1/n compared to the conventional example (FIG. 17), and the inductance of the coil is equal to the number of windings. Since it is proportional to the square, considering each high voltage transformer 13i, the secondary inductance is L2/n2,
The secondary voltage is E2/n. Furthermore, the load on each high-voltage transformer 13i is equivalent to dividing the conventional Rx into n, and therefore becomes Rx/n. Therefore, the equivalent circuit of FIG. 1 can be expressed as shown in FIG.

Regarding the secondary side of each high voltage transformer 13i,
Considering the case in the same way as in Figure 2, the time constant τ in this case is
b is expressed by the following formula.

τb=(L2/n2)/(Rx/n)=(L2/Rx)
/n=τa/n (5) The voltage E3 applied to the load at this time is as follows.

E3=E2(1-e-t/τb)/n...(6)
The voltage Ex applied to the X-ray tube is obtained as follows by connecting the terminal voltage E3 of the load in series.

[0026] Ex=n・E3=E2(1-e-t/τb)...
(7) That is, the applied voltage Ex reaches the value of 0.63·E2 when t=τb as shown in curve B shown in FIG. 4, which was reached when t=τa in the conventional device. Here, since τb=τa/n as shown in equation (5), the time constant of the embodiment device of FIG. 1 is 1/n compared to the conventional device, and the output pulse width of the frequency converter 12 is If τb, the same X-ray applied voltage can be obtained, so it is understood that the frequency of each high voltage transformer 13i can be made n times higher.

In the conventional high-voltage transformer 3 shown in FIG. 2, even if the switching pulse width of the frequency converter 2 is simply increased by 1/n times (τb) from τa, the frequency will be increased.
The peak voltage of the applied voltage Ex shown in equation (4) becomes small as shown by curve C shown in FIG. 4, and the applied power only becomes small as shown by the diagonal line.

As explained above, according to the first embodiment, a plurality of (for example, n) high voltage transformers with small capacities (
The number of turns in the primary winding is the same, and the number of turns in the secondary winding is 1/n.
The primary side of each transformer is connected in parallel to the output of the frequency converter, and the rectified results of the output of each transformer are added in series and applied to the X-ray tube. The second-order inductance can be reduced to 1/n2, and as a result, the upper limit of the output frequency of the frequency converter 12 is increased by n times. This allows the device including the frequency converter 12 to be significantly reduced in size and weight. Specifically, since the output frequency of the frequency converter can be increased to about 100 KHz, that is, a frequency exceeding the audible frequency, almost no noise is generated, which was a drawback of conventional devices.

Furthermore, as the output frequency of the frequency converter 12 increases, the output can be controlled at high speed, so that the high voltage applied to the X-ray tube 15 can be set with high precision by feedback. Furthermore, the ripple of the high voltage waveform becomes smaller as the frequency increases, so
A flat high voltage waveform can be obtained. Furthermore, since the rise characteristics of the applied voltage are improved as shown in curve B shown in FIG. 3, it becomes easy to apply high voltage to the X-ray tube 15 in a pulsed manner and generate X-rays only at the necessary timing. So,
The X-ray exposure dose to the subject can be reduced. In addition, as the frequency becomes higher, it is desirable that the core of the high voltage transformer 13i be formed of ferrite or the like having good frequency characteristics.

Note that the outputs of all the high voltage transformers may be connected in series without connecting each rectifier circuit 14i to each high voltage transformer 13i, and the voltage of the series connection may be rectified by one rectifier circuit. Furthermore, a resonance capacitor may be connected in series or in parallel to the primary side of each high voltage transformer. Furthermore, although frequency converters perform square wave switching, it goes without saying that not only the output frequency but also the voltage can be changed using pulse width modulation (PWM), which changes the pulse width of this square wave. .

Next, a modification of the first embodiment will be explained. In conventional X-ray generators, the high-voltage transformer and high-voltage rectifier circuit are housed in a container containing insulating oil. For this reason, the entire container will be filled with insulating oil, so
It was very large in both volume and weight. In addition, maintenance was not easy and oil leaked from the container, which contaminated the surrounding area. However, in this embodiment, the transformer is divided into a plurality of small-capacity transformers, so the high-voltage transformer and high-voltage rectifier circuit are housed in a small-capacity container, molded with a solid insulating material that also contains gel, and the unit is can be converted into Examples of insulating materials include insulating materials for casting such as epoxy, and materials that solidify, such as silicone gel, but whose physical properties are intermediate between fluids and solids. Since silicone gel has good high frequency characteristics, it is preferable as an insulating material for devices intended for such high frequencies. Note that the unit to be formed into a unit may be one transformer 131 and rectifier circuit 141 as shown in FIG. 5, or may be a plurality of transformers 131 to 13j and rectifier circuits 141 to 14j as shown in FIG. Alternatively, as shown in FIG. 7, only the secondary winding of the transformer 13 and the rectifier circuit 14 may be molded, and the primary winding of the transformer 13 may not be molded. Furthermore, although not shown, the high-voltage transformer and the rectifier circuit may be separately molded and connected only by a high-voltage cable or a connector, and various combinations of molds can be selected.

[0032] By combining these units, there is no need to fill extra space with insulating oil, unlike in the conventional case where a large high-voltage transformer and rectifier circuit are housed in one container. A small and lightweight X-ray generator that is easy to assemble and can be replaced in molded units can be realized, which is easy to maintain. In addition, solid insulating materials have a higher dielectric breakdown voltage than insulating oil, so they have good insulation efficiency and are easy to reduce in size and weight. Note that reducing the size and weight of the X-ray generator has the advantage that it requires less installation space in hospitals and the like, making it easier to transport and move. Furthermore, if you use a transparent polycarbonate container for molding and a transparent silicone gel molding material, the interior will be transparent, allowing you to check for air bubbles, cracks, soldering, etc. after molding. In addition to making quality control easier, it also makes it easier to check for cracks, discharge phenomena, material deterioration, and the presence or absence of coloring, making it easier to analyze when trouble occurs.

Next, a second embodiment will be explained. FIG. 8 is a block diagram thereof. The same parts as in the first embodiment are given the same reference numerals and detailed explanations will be omitted. In the first embodiment, only one frequency converter 12 was provided, but in the second embodiment, the frequency converter is also divided into n pieces like the transformer. A frequency converter 12i is connected in parallel to the AC power supply 11. The outputs of the frequency converters 12i are each supplied to a rectifier circuit 14i via a high voltage transformer 13i. Note that a capacitor C is connected to the secondary winding of each high voltage transformer 13i.
R are connected in series to form a series resonant circuit on the secondary side of the transformer.

[0034] This embodiment also provides the same effects as the first embodiment. Furthermore, if any frequency converter is inactive, the output of the rectifier circuit on the secondary side of the high voltage transformer connected to the remaining frequency converter is
It is applied to the X-ray tube bypassing the high voltage transformer connected to the idle frequency converter. Therefore, by controlling the number of frequency converters that are paused, the voltage applied to the X-ray tube can be roughly controlled. Furthermore, the high voltage output can be adjusted by PWM controlling the frequency converter.

Further, according to the second embodiment, since a large number of small-capacity frequency converters are used, if a frequency converter breaks down, that frequency converter is stopped and the corresponding frequency converter is
Since the frequency converter that is originally inactive can be replaced, the entire X-ray generator does not become unusable. Note that the maximum output will be lower by the amount of the failed frequency converter 2, but there are not many cases where the maximum output is required, and in practice the device can be used without any problems while the failed frequency converter is replaced. can.

Note that the reason why the resonance capacitor CR is connected to the secondary side of each high voltage transformer 13i is to further increase the operating frequency by causing LC series resonance. Further, the resonance capacitor may be connected to the primary side, and the resonance may be series resonance or parallel resonance.

Next, the characteristics of the second embodiment will be explained. An equivalent circuit of the secondary side portion of one high voltage transformer 13 is shown in FIG. Since the frequency converter 12 performs a rectangular wave switching operation, the secondary voltage E2 is a rectangular wave in the first embodiment shown in FIG. 3, but in the second embodiment in which the secondary side resonates, it is approximately It becomes a sine wave. The frequency of this sine wave is f,
If ω=2πf, then according to the general theory of series resonance,
If the value of capacitor CR is determined so that the condition ωL2=1/ωCR is satisfied at a specific frequency, the impedance on the secondary side will be only Rx, so even if the specific frequency is set to a high value, As shown in FIG. 4, the influence of the secondary inductance L2 on the applied voltage Ex can be ignored. However, although the voltages across L2 and CR in FIG. 9 have opposite phases and cancel each other out, EL=E2・ωL2/Rx, EC=E2/(ωCR
・Rx), which is generally a much larger value than E2. Therefore, secondary side resonance was not possible in the conventional example shown in FIG. 2 due to problems with the withstand voltage and insulation measures of the transformer and capacitor.

However, in this invention, since the high-voltage transformer is divided into n pieces, if a resonance capacitor CR is inserted on the secondary side of each high-voltage transformer as in the second embodiment, the resonant circuit of each As shown in FIG. 3, E2 and L2 become small as E2/n and L2/n2, respectively. In particular, since L2 is inversely proportional to the square of the number of divisions n, it becomes very small. Therefore, the voltage E across L2 and CR
Since L and EC can be suppressed to small values, the advantage of secondary side resonance can be utilized.

In this way, when the high voltage transformer is simply divided as in the first embodiment, the secondary inductance L2
High frequency operation has become possible by reducing High frequency operation is possible. Alternatively, in the case of operating at the same frequency as in the case of not causing secondary side resonance, the number of divisions can be reduced within a range that allows the withstand voltage of the transformer and capacitor. Also, due to secondary resonance, the current waveform on the primary side becomes a sine wave, so by turning the switching transistor of the frequency converter 12i on and off when the current is 0, loss is extremely small and heat generation can be suppressed. As a result, the efficiency of the device can be greatly increased. Note that the secondary side resonance is not limited to the series resonance as described above, but may also be a parallel resonance in which a capacitor is connected in parallel to the secondary side of the high voltage transformer.

FIG. 10 shows the characteristics of the voltage applied to the X-ray tube when the secondary side resonates. The solid line indicates Ex, of which curves A and B indicate the conventional device and the case where the high voltage transformer is divided into n pieces, respectively, similar to curves A and B in FIG.
Curve D is the characteristic when the high voltage transformer of the second embodiment is divided and the secondary side is made to resonate.

As described above, according to the second embodiment, the rise in the waveforms of curves A and B, which had been suppressed by the secondary inductance of the high-voltage transformer, becomes faster as in curve D due to resonance, so that higher frequency At the same time, it is possible to further increase the voltage applied to the X-ray tube. Note that fr is the resonance frequency on the secondary side. Also, the broken line is the secondary inductance L2
, represents the terminal voltages EL and EC of the capacitor CR multiplied by the number of divisions.

As described above, according to the second embodiment, the frequency can be made higher and the number of divisions can be reduced due to the secondary side resonance compared to the case where the high voltage transformer is simply divided. Note that the number of frequency converters in the second embodiment does not necessarily have to correspond one-to-one to the number of high-voltage transformers.

[0043] Furthermore, the modification described in the first embodiment is
All of the above are possible in the embodiment, and unitization by molding with a solid insulating material is possible as in the first embodiment. Furthermore, the secondary resonance capacitor of the second embodiment may be connected to the secondary side of the high voltage transformer of the first embodiment.

Next, a third embodiment will be explained. FIG. 11 is a block diagram thereof. After the AC voltage from the power supply 11 is converted into a DC voltage via the rectifier circuit 22 and the capacitor 24,
The voltage is applied to the plurality of generator units 26i. Each generator unit 26i is the rectifier circuit 1 of the above-mentioned embodiment.
The outputs of all generator units 26i are added in series and applied to the X-ray tube 15. Generator unit 26
i consists of an inverter card including an inverter section that converts an input DC voltage into a high-frequency AC voltage, and a mold section including at least the secondary side of a high-voltage transformer and a rectifier circuit. A fixed pulse generator 36 and a variable pulse generator 34 are provided to control the switching operation of the inverter section. Several variable pulse generators 34 are connected here, only to one generator unit 26n, and are connected to other generator units 261 to 26n.
-1 is supplied with the output of the fixed pulse generator 36 via AND gates 381 to 38n-1. The conduction/non-conduction of the AND gates 381 to 38n-1 is controlled by a gate control signal from the output voltage controller 32 according to the set value of the output voltage.

The voltage applied to the X-ray tube 15 is detected by a high-voltage divider 28 connected in parallel with the X-ray tube 15, and is supplied to one input terminal of an error amplifier 30. A set voltage from an output voltage controller 32 is supplied to the other input terminal of the error amplifier 30, and the difference between both input voltages is controlled by a variable pulse generator 34.
supplied to The variable pulse generator 34 generates a pulse signal with a pulse width depending on the output voltage of the error amplifier 30. That is, the generator unit 26n is subjected to pulse frequency modulation or pulse width modulation using a voltage feedback method. The switching frequencies of the remaining generator units are set to a constant frequency, which will be described later. Therefore, in order to vary the output voltage (X-ray tube applied voltage), the number of AND gates 38 corresponding to the output voltage value are made conductive, and the number of operating generator units 26 is controlled to roughly control the output voltage. do. Then, the output voltage is finely adjusted by feedback control including the variable pulse generator 34.

Next, details of the generator unit 26i will be explained. FIG. 12 is a detailed block diagram thereof, and FIG. 13 is a diagram showing the external appearance. As shown in FIG. 12, each generator unit 26 includes two switching elements 46.
, 48 and a drive circuit 44 for driving them, and has an inverter section that converts the DC voltage from the rectifier circuit 22 into an AC voltage, and the inverter section is provided on the printed circuit board 40 as shown in FIG. . switching element 46,
As 48, MOSFET is generally used, but
Other IGBTs, bipolar transistors, thyristors, etc. may also be used. The outputs of the inverter section are connected to the primary sides of a plurality of, here two, high voltage transformers 501 and 502. Rectifier circuits 521 and 522 are connected to the secondary sides of the high voltage transformers 501 and 502, respectively. Rectifier circuits 521 and 522 are connected in series and generate a DC voltage according to the result of addition of the output voltages of the high voltage transformer.

On the primary side of the high voltage transformer, a resonant capacitor CR1 is connected in parallel to the winding, and a parallel resonant circuit is formed on the primary side. A resonance capacitor CR2 is connected in series to the secondary winding of each high-voltage transformer, and a series resonance circuit is configured on the secondary side. With such a primary and secondary multi-resonant circuit configuration, the efficiency of the inverter section can be further improved. The multi-resonance configuration is not limited to the combination of the above-mentioned resonant circuits, but may also include series resonance on the primary side and parallel resonance on the secondary side, or may have the same resonant circuit on both the primary and secondary sides.

As shown in FIG. 13, a high voltage transformer 501
, 502 are arranged outside the molded part 42, and the secondary sides of the high voltage transformers 501, 502 and the rectifier circuits 521, 5
22 is placed inside the mold part 42. Mold part 4
As explained in the first embodiment, the second configuration uses transparent polycarbonate or the like as a container for molding,
Although it is preferable to use transparent silicone gel or the like as the molding material, other solid insulating materials such as epoxy may also be used. The mold part 42 includes rectifier circuits 521 and 522.
A radiator 54 made of ceramic or the like having high thermal conductivity is provided to efficiently radiate heat from the radiator. Note that the inverter card 40 is also provided with a heat radiator 56 that radiates heat from the switching elements.

As described above, according to the third embodiment, the inverter for converting input DC voltage into AC voltage is divided into a plurality of small capacity inverters, and a plurality of small capacity transformers are connected to each inverter. By unitizing the high voltage generating section, the frequency of the alternating current voltage can be increased, and the device can be made smaller and lighter. Additionally, molding the unit with solid insulating material facilitates assembly and maintenance. Furthermore, efficiency can be increased by connecting a resonance capacitor to the transformer and operating the inverter at the resonance frequency. At this time, by feedback-controlling only the frequency of one or several inverters in order to adjust the output voltage, it is possible to minimize the reduction in efficiency due to fine adjustment of the output voltage.

Next, a modification of the third embodiment will be explained. In FIG. 12, the rectification results of the output voltages of each high-voltage transformer are added, but the rectification method is not limited to this. Secondary voltage of high voltage transformer (including voltage of resonance capacitor CR2)
may be added and then rectified, or as shown in FIG. 14, may be added on the secondary side of several high voltage transformers and then rectified. Although FIG. 14 shows an example in which one resonance capacitor is connected to each high-voltage transformer, the configuration of the resonance circuit is not limited to this. Alternatively, as shown in FIG. 15, the secondary sides of each high-voltage transformer may be directly connected in series and after the output voltages are added, one resonance capacitor may be connected for rectification. Note that the rectifier circuit may be a full-wave rectifier circuit as shown in FIG. 14 or a voltage doubler rectifier circuit as shown in FIG. 15.

Further, the heat radiator may have a shape as shown in FIG. That is, the lower part of the heat sink 64 is buried in the mold part 42 and comes into contact with one side of the rectifier circuit part 62, so that
Heat dissipation effect is enhanced.

[0052]

As explained above, according to the X-ray generator according to the present invention, the transformer that boosts the output of the inverter that converts the input voltage into a high-frequency AC voltage can be The output frequency of the frequency converter can be increased without reducing the applied voltage by dividing into multiple transformers with a small capacity, adding the outputs of these transformers, and applying the addition result to the X-ray tube. . This makes it possible to reduce the size and weight of the apparatus, and the higher the frequency, the faster the control speed, and by feeding back the output, it is possible to control the X-ray output value with high precision.

Furthermore, by molding the divided transformer and rectifier circuit with a solid (including gel) insulating material to form a unit, assembly and maintenance become easier. Note that the inverter may also be divided into a plurality of small-capacity inverters, each inverter connected to a plurality of small-capacity transformers, and these may be made into a unit.

[0054] Further, by high-frequency operation, ripples in the output can be easily reduced and stabilized, and X-rays can be made into pulses. Furthermore, by increasing the frequency, the frequency of the switching pulse of the frequency converter can be set above the audible frequency, so noise can be significantly reduced. Additionally, by connecting multiple frequency converters to multiple transformers, each frequency converter can be easily controlled independently, making it easy to adjust the voltage applied to the X-ray tube, and also Even if a frequency converter fails, the device can continue to be used with other frequency converters.

Furthermore, a capacitor is connected to the transformer,
By configuring an LC resonant circuit and operating it resonantly, it is possible to further increase the frequency, reduce heat generation of the device, and increase efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of an X-ray generator according to the present invention.

FIG. 2 is an equivalent circuit diagram of a portion from the secondary winding of a high-voltage transformer to an X-ray tube in a conventional device for comparison with the first embodiment.

FIG. 3 is an equivalent circuit diagram of a portion from the secondary winding of the high-voltage transformer to the X-ray tube in the first embodiment.

FIG. 4 is a diagram showing characteristics of the first embodiment.

FIG. 5 is a diagram showing a first modification of the first embodiment.

FIG. 6 is a diagram showing a second modification of the first embodiment.

FIG. 7 is a diagram showing a third modification of the first embodiment.

FIG. 8 is a block diagram of a second embodiment of the X-ray generator according to the present invention.

FIG. 9 is an equivalent circuit diagram of a portion from the secondary winding of the high-voltage transformer to the X-ray tube in the second embodiment.

FIG. 10 is a diagram showing characteristics of the second embodiment.

FIG. 11 is a block diagram of a third embodiment of the X-ray generator according to the present invention.

FIG. 12 is a detailed block diagram of the generator unit of the third embodiment.

FIG. 13 is a diagram showing the appearance of a generator unit according to a third embodiment.

FIG. 14 is a block diagram showing a modification of the rectification method of the third embodiment.

FIG. 15 is a block diagram showing another modification of the rectification method of the third embodiment.

FIG. 16 is a diagram showing a modification of the radiator of the third embodiment.

FIG. 17 is a block diagram of a conventional example of an X-ray generator.

FIG. 18 is an equivalent circuit diagram of the conventional example shown in FIG. 17.

FIG. 19 is a diagram showing another conventional example of an X-ray generator.

FIG. 20 is a diagram showing still another conventional example of an X-ray generator.

[Explanation of symbols]

11... AC power supply, 15... X-ray tube, 22... Rectifier circuit, 26
...Generator unit, 28...High pressure divider, 32...
Output voltage controller, 34... Variable pulse generator, 36
...Fixed pulse generator, 38...And gate, 40
...Inverter card, 42...Mold part. 50... High voltage transformer, 52... Rectifier circuit.

Claims (1)

[Claims] 1. An X-ray generator that applies a DC high voltage to an X-ray tube, comprising a plurality of high-voltage generating units whose input sides are connected to a power source and whose output sides are connected in series with each other,
Each of the high voltage generation units includes means for converting an input voltage into an alternating current voltage of a predetermined frequency, a plurality of transformers connected to the output of the converter and boosting the alternating voltage, and an output of the plurality of transformers. An X-ray generator characterized in that it comprises means for rectifying.