JP2826566B2 - Inverter type X-ray equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power supply for an X-ray generator, and
The present invention relates to a resonance type inverter type X-ray generation power supply device suitable for weight reduction.

[Conventional technology]

In order to reduce the size and weight of the power supply device for generating X-rays, the biggest challenge is to make the high-voltage transformer that boosts the voltage of the commercial power supply to a high voltage for applying to the X-ray tube small and light. Was.

High-voltage transformers can be made smaller and lighter by increasing the frequency of the input voltage to them. Such a technique for increasing the frequency of the input voltage to the high-voltage transformer has been developed by using a semiconductor device for power control, which has been remarkably developed in recent years, as a switching element. A so-called inverter type X-ray apparatus is currently in practical use.

As such an inverter type X-ray apparatus, resonance is caused by the leakage inductance of the high-voltage transformer and a capacitor connected in series with the leakage inductance, and the output voltage of the high-voltage transformer is rectified and applied to the X-ray tube. There is a resonance type inverter X-ray apparatus.

In an apparatus of this type, control of a voltage applied to an X-ray tube as a load (hereinafter referred to as “tube voltage”) is performed by controlling a frequency of an inverter disclosed in, for example, US Pat. No. 4,225,788. Also, the method of controlling the operation phase of the inverter disclosed in Japanese Patent Application Laid-Open No. 63-190556 and feedback control of the tube voltage have been used to stabilize the tube voltage.

[Problems to be solved by the invention]

However, when the frequency and phase are subjected to feedback control, the error between the actual tube voltage and the set tube voltage changes, so that the frequency and phase, which are the control amounts of the tube voltage, change every moment.

For this reason, the frequency and phase are different for each half cycle of the inverter operation, and a difference occurs in the voltage-time product of the input of the high-voltage transformer,
The high voltage transformer is magnetized.

In order to prevent magnetic saturation due to the magnetic demagnetization, the operating magnetic flux density must be set to a small value, so that there is a limit to downsizing the high-voltage transformer.

In addition, when the magnetism is demagnetized, the magnetostrictive vibration of the iron core of the high-voltage transformer is increased, which causes a problem of an increase in noise. Therefore, despite the introduction of the resonance type inverter in the X-ray apparatus, there are still problems in achieving miniaturization and noise. With the spread of various types of diagnostic imaging equipment (X-ray CT equipment, MRI equipment, nuclear medicine equipment, ultrasonic diagnostic equipment, etc.) in recent years, the installation space is being limited, and the target is a patient. Therefore, it is not permissible to generate noise.

Therefore, the present invention provides a technique capable of preventing the core of the high-voltage transformer of the resonance type inverter type X-ray apparatus from being demagnetized, thereby realizing the downsizing of the transformer and, consequently, the downsizing of the X-ray apparatus. It is another object of the present invention to eliminate noise caused by magnetostrictive vibration caused by demagnetization of an iron core.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a DC power supply, a resonant inverter that converts an output voltage of the DC power supply into a high-frequency AC, a high-voltage transformer that boosts the output voltage of the inverter, and a high-voltage transformer. A rectifier circuit for rectifying the output voltage, an X-ray tube to which the output voltage of the rectifier circuit is applied,
An inverter-type X-ray apparatus comprising: a control unit that controls an operating point or an operating frequency of the inverter or both of the operating points of the inverter to control a voltage applied to the X-ray tube. Control signal holding means for holding a signal for controlling the operating point constant in the positive and negative half cycles of one cycle of the operation of the inverter;
Operating point determining means for comparing the output of the control signal holding means with a reference value to determine the operating point, wherein the operating point of the inverter determined by the operating point determining means is set to one cycle of the operation of the inverter. This is achieved by equalizing the voltage-time product output from the inverter to the high-voltage transformer by making the positive and negative half cycles constant.

Further, the above object is to provide a DC power supply, a resonant inverter that converts an output voltage of the DC power supply into a high-frequency AC, a high-voltage transformer that boosts an output voltage of the inverter, and rectifies an output voltage of the high-voltage transformer. A rectifier circuit, an X-ray tube to which an output voltage of the rectifier circuit is applied, a tube voltage detector for detecting a voltage applied to the X-ray tube, a tube voltage setting signal, and a detection signal of the tube voltage detector And amplifying the difference, and controlling the operating phase or operating frequency of the inverter or the operating point of both of the inverters with a control signal corresponding to the amplified signal to obtain a voltage applied to the X-ray tube. Means for controlling feedback, wherein the means for controlling feedback comprises: a control signal for holding the control signal constant in positive and negative half cycles of one cycle of the operation of the inverter. Holding means, and operating point determining means for determining an operating point of the inverter by comparing an output of the control signal holding means with a reference value, and determining the operating point of the inverter determined by the operating point determining means. This is achieved by making constant the positive and negative half cycles of one cycle of the operation of the inverter and making the voltage-time products output from the inverter to the high-voltage transformer equal.

[Principle of the invention]

In the present invention, the output voltage of the DC power supply may fluctuate in a macroscopic view, but may be regarded as a constant value in an extremely short time such as one operation cycle of an inverter operating at a high frequency. In view of the above, according to the present invention, in one cycle in which the positive and negative sides of the two switching means for converting the DC voltage into the AC by the inverter are alternately turned on / off, the ON period on the positive side and the ON period on the negative side are set. By making them equal, the voltage-time product of the output from the inverter to the high-voltage transformer is made the same.

More specifically, as described in the latter part of [Means for Solving the Problems], in the X-ray apparatus, in order to set the actual tube voltage to the set tube voltage, feedback control of the actual tube voltage to the voltage control means is performed. It is common to do. In the resonance type X-ray apparatus, the inverter also serves as the tube voltage control means.

Therefore, the present invention provides a control signal holding unit that holds a control signal corresponding to a differential amplification signal between a tube voltage setting signal and a detection signal of a tube voltage detector in one cycle of positive and negative half cycles of the operation of an inverter. And an operating point determining means for comparing the output of the control signal holding means with a reference value to determine the operating phase or operating frequency of the inverter or both of the operating points of the inverter. The operating point of the inverter determined by the determining means is made constant between the positive and negative half periods of one cycle of the operation of the inverter so that the voltage-time product output from the inverter to the high-voltage transformer is equalized.

 Hereinafter, the operation will be described together with the embodiment.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an embodiment of the X-ray apparatus according to the present invention. This X-ray apparatus is a DC power source 1 such as a secondary battery.
, Inverter 2, transformer 3, resonance capacitor 6
And a rectifier circuit 4 and an X-ray tube 5.

The inverter 2 converts the alternating current by receiving DC from the DC power source 1, a second connected to the transistor T _r1 and the negative electrode of the first switch connected to the positive electrode of the DC power source 1 Transistor as a switch
A first series connection consisting of T _r2 and the transistor T _r1
And a second series connection composed of the transistor T _r4 as transistors T _r3 and the fourth switch as the third switch which respectively provided in parallel T _r2, reverse respectively to each transistor T _r1 through T _r4 consisting parallel connected first diode D ₁ ~ fourth diode D ₄ Prefecture. In addition,
Each transistor T _r1 through T _r4 is summer to Yotsute turned on to flow a respective base currents.

The transformer 3 is connected to the output side of the inverter 2 and boosts the output voltage from the inverter 2, has a predetermined turns ratio, and has a leakage inductance L _S and a stray capacitance C _S. A resonance capacitor 6 is connected in series to the primary winding of the transformer 3.

The transformer primary winding and the capacitance C _r and the transformer leakage inductance of the resonance capacitor 6 connected in series
L _S is used as a resonance element.

In order to obtain series resonance, the stray capacitance of the transformer
C _S is set to a very small value than the capacitance C _r of the resonance capacitor 6.

The rectifier circuit 4 is a full-wave rectifier for converting the output voltage from the transformer 3 into a direct current, and includes four diodes D _{5 to} D _8.
Consists of An X-ray tube 5 is connected to an output side of the rectifier circuit 4. In the first diagram, reference numeral C _h
Is a capacitance of a high-voltage cable for applying the output voltage of the rectifier circuit 4 to the X-ray tube 5, and smoothes the output voltage from the rectifier circuit 4.

In the present invention, the phase control for controlling the operating phase of the transistor T _r1 through T _r4 of the voltage to be applied to the X-ray tube 5 (hereinafter "tube voltage" hereinafter.) By the setting signal connexion the inverter 2 together with a circuit 10 is provided to detect by connexion tube voltage divider 7, which was inputted to the error amplifier 9 through a signal conversion circuit 8 for converting the appropriate signal, the tube voltage setting signals S ₁ Amplify the difference and apply it to the phase control circuit 10
Is configured to be input. Note that reference numerals 11a to 11d
Is a drive circuit for driving the Supporting connexion respective transistors Tr ₁ to Tr ₄ on the control signal outputted from the phase control circuit 10. Then, the phase control circuit by 10, the transistor T _r1 as the first switch of the inverter 2 a transistor T _r2 of the second switch the inverter 2
At an operating frequency of 180 °, the transistor Tr _r3 as the third switch and the transistor Tr _r4 as the fourth switch are alternately turned on with a phase difference of 180 °, and the appropriately changing the phase difference a third transistor T _r3 is turned from the first transistor T _r1 is turned on by the phase difference and the second transistor T _r2 which fourth transistor T _r4 is turned is turned on Therefore, the power supplied to the X-ray tube 5 is controlled.

FIG. 2 is a timing chart of each part when the phase difference is 0, and the output becomes maximum under a constant load condition.
FIG. 3 is a timing diagram at an arbitrary phase difference α,
Any output can be obtained.

When the output is set to 0, the phase difference may be set to 180 °. Thus, by varying the phase difference α from 0 to 180 °, the output power can be continuously controlled as shown in FIG.

In FIG. 4, R ₁ , R ₂ , and R ₃ are load resistances, which are values determined by load conditions, that is, tube voltage and tube current.

Thus the above respective transistors T _r1 through T _r4 and to start the operation, FIG. 2 or the third resonance current it as shown in FIG flow in the transformer 3, the tube voltage the set to the X-ray tube 5 And power from the tube current. At this time, the inverter 2 is connected to the leakage inductance L _{S of the} transformer 3.
To operate at a resonance frequency or a frequency close to that of the capacitance C _r of the resonance capacitor 6. According to the present invention, a voltage divider 7 for detecting a tube voltage applied to the X-ray tube 5 is provided, and a detection signal from the voltage divider 7 and a preset target voltage signal (tube voltage setting signal S ₁ ) are amplified. amplifies the difference and enter into the circuit 9, a signal for controlling the operation phase of the transistor T _r1 through T _r4 of O connexion inverter 2 to the difference, X-rays exposure signal inputted from a controller outside the illustrated
The phase control circuit 10 which by connexion output to S ₄ are those which gave the characteristics described below. Then, these divider 7 and the error amplifier circuit 9 and the phase control circuit 10, the transistor T _r2 and the operating frequency of the inverter 2 as a transistor T _r1 and the second switch as a first switch of the inverter 2 At the same time, the transistor Tr _r3 as the third switch and the transistor Tr _r4 as the fourth switch are alternately turned on with a phase difference of 180 °, and the first switch is turned on alternately with a phase difference of 180 °. Transistor
Phase difference and the second transistor T _r2 is Yotsute that the third transistor T _r3 is appropriately changing the phase difference to turn after turn-on T _r1 is a fourth transistor T _r4 from the turn-on is turned on, The power supplied to the X-ray tube 5 is feedback-controlled.

In such feedback control, the output of the error amplifier circuit changes every moment, and the change is particularly large when the tube voltage rises.

If this is input to the phase control circuit 10 as it is, a difference occurs in the phase between the positive and negative half cycles of the operation of the inverter 2,
For this reason, a difference occurs in the voltage-time product input to the high-voltage transformer 3 and the iron core of the high-voltage transformer 3 is magnetized.

In order to suppress this, in the X-ray apparatus of the present embodiment, the phase control circuit 10 is configured as in the example shown in FIG. In FIG. 5, reference numeral 10a denotes a frequency signal generating circuit which outputs a signal A for determining the operating frequency of the inverter 2 using a clock signal of a known high-frequency oscillator or a microcomputer, and 10b denotes a one-cycle determining circuit for generating a frequency signal. Circuit 10a
, And generates and outputs a signal B for determining one cycle of the operation of the inverter 2. An error holding circuit 10c is a signal output from the error amplifier circuit 9 shown in FIG. inputs the said signals B and S _3, signal by signal B
Outputs a hold signal C and hold S _3, 10d in the phase decision circuit receives the signal A is generated sawtooth wave E,
The sawtooth wave E is compared with the hold signal C,
10g is a pulse distribution circuit (1) that outputs a phase signal F, receives the output A of the frequency signal generation circuit 10a,
For generating signals P ₁ and P ₂ , 10h is a pulse distribution circuit (2)
The phase signal F is input, and the signals are distributed and output as signals P ₃ and P ₄ . Pulse distribution circuit (1) 10
g, a driving pulse signal of the transistor T _r1 through T _r4 of the P ₁ to P ₄ is the inverter 2 from the pulse distribution circuit (2) 10h, FIG. 2, in correspondence with FIG. 3, the P ₁ ( a), P ₂ is (c), the P ₃ (b), P ₄ corresponds to (d). Then, as shown in F of FIG. 6, the two phase signals φ output in one cycle of the operation of the inverter become equal.

Next, the operation of the phase control circuit 10 of FIG. 5 will be described. The frequency signal generating circuit 10a outputs the signal A at every cycle set in accordance with the operating frequency of the inverter 2 (in this embodiment, every half cycle of the operation of the inverter 2). First
Tube voltage setting signals S ₁ and the X-ray曝信No. S ₄ are the input X-ray from the X-ray tube 5 in FIG is exposure, input the tube voltage is to tube voltage detection signal S ₅ detects the error amplifier circuit 9 And the signal S ₃
Is output. Now, when the frequency signal generation circuit 10a shown in the drawing outputs the pulse A, the one-period determination circuit 10b also outputs the pulse B in synchronism therewith. Then the error-hold circuit 10c holds a signal S ₃ at the timing of the pulse B, and outputs the hold signal C to phase decision circuit 10d.

The phase determining circuit 10d includes a frequency signal generating circuit 1 in addition to the signal C.
The signal A from 0a is input, and the sawtooth signal E having the waveform shown in FIG. 6 is repeatedly generated at the timing when the signal A is generated. Then, the phase determining circuit 10d outputs the signal C
And a signal E, and outputs a phase signal F that is turned on only when E> C. Thus, signal F includes pulse outputs φ ₁ and φ ₁ ′ within one cycle of operation of inverter 2 and outputs a pulse having a relation of φ ₁ = φ ₁ ′. The relationship between the signal F and the operation phase difference α of the inverter 2 is φ φ
₁ + α ₁ = 180 ° and φ ₁ ′ + α ₁ ′ = 180 °.

In a first pulse period of the frequency signal generating circuit 10a, the pulse distribution circuit (1) 10 g signal A, and outputs a signal P ₁ is turned on, P ₂ is turned off, whereas, the pulse distribution circuit 10h is E> C P ₃ is turned on, P ₄ outputs a signal for turning off using only oN signal F between. Frequency signal generation circuit
When 10a outputs a second wave first pulse A, the signal P ₁ is turned off, P ₂ is turned on. At the same time, the phase determination circuit 10d
Compares the signal C left as it is with the sawtooth wave E generated again, and generates a signal F that is turned on only during the period of E> C as described above. Then, F is the pulse distribution circuit at timing on (2) 10h is, P ₃ outputs a signal off, P ₄ is turned on. When the signal A shown in FIG. 6 outputs the third wave th pulse, P ₁ is turned on, P ₂ is turned off.

When this third pulse A is output, the one-cycle determination circuit
Pulse B is output from 10b. At the timing of the pulse B, the error hold circuit 10c holds the output signal of the error amplifier circuit 9 again. Then, the above operation is repeated.
The pulse output of P ₁ to P ₄ is supplied to the transistor T _r1 through T _r4 of the inverter 2 as described previously.

It should be noted that the phase control circuit 10 of the present embodiment includes a phase determination circuit 10d.
Is used to compare the sawtooth wave E and the hold signal C, but other methods may be used. For example, in FIG.
The signal A is generated input sawtooth wave to the error-hold circuit 10c, may be adopted a method of holding compares sawtooth waveform signal S _3, precise feedback control than the above embodiment in this case Can be.

Next, the operation of the X-ray apparatus configured as described above will be described. First, when the supply tube voltage to the X-ray tube 5 is determined to enter the tube voltage setting signals S ₁ corresponding to the tube voltage from an unillustrated controller as the target voltage signal to the error amplifier circuit 9. On the other hand, this error amplifying circuit 9, the tube voltage detection signal S ₅ corresponding to the detected transformed current tube voltage at the signal conversion circuit 8 in a voltage divider 7 is input. Then, the error amplifier circuit 9, the tube voltage setting signals S ₁ and the tube voltage detection signal
Detecting an error between S _5, proportional to the error - treated with such integral control, the inverter 2 in response to the magnitude of the error
To determine the phase difference α of operation of the transistor T _r1 through T _r4 of inputs to the phase control circuit 10. At this time, before the start of the X-ray exposure, the tube voltage detection signal to the tube voltage setting signals S ₁
Since S ₅ is zero, S ₃ is becomes maximum (in FIG. 6 0 position) the maximum power is set to the phase difference α is zero so that it can supply.

Then, in the phase control circuit 10, the transistor T _r1
To help establish control signal through T _r4 is turned on and off, the transistor T as a first phase difference alpha ₁ transistor T _r4 is turned on with the transistor T _r1 in the switch as the fourth _switch, and the second switch _r2 and transistor T _r3 as third switch creates a control signal for controlling a phase difference alpha _{1 'to} turn on. (According to the present invention, α ₁ = α ₁ ′.) Then, when the X-ray irradiation signal S ₄ is input to the phase control circuit 10 from a controller (not shown), the phase control circuit 10 Control signals P _{1 to} P ₄
Send to 1d. As a result, each of the drive circuits 11a to 11d causes the inverter 2 to respond to the control signal from the phase control circuit 10.
Driving each transistor T _r1 through T _r4 of.

Thus the above respective transistors T _r1 through T _r4 and to start the operation, the second view or resonance current it as shown in FIG. 3 flows in the transformer 3, the tube voltage is applied to the X-ray tube 5 At first, a tube current flows. When approaching the value tube voltage of the X-ray tube is set, the error between the tube voltage setting signals S ₁ and the tube voltage detection signal S ₅ is reduced, the error amplifier circuit 9, a phase difference α It operates so as to increase (in contrast, φ decreases), and reduces the supply of power from the DC power supply 1. When the tube voltage of the X-ray tube becomes almost equal to the set value,
The inverter 2 operates in a phase in which power equal to the power set by the set tube voltage and tube current can be supplied from the DC power supply 1. At this time, the inverter 2 is operated at a resonant frequency or a frequency close to that of the leakage inductance L _S of the transformer 3 and the capacitance C _r of the resonance capacitor 6.

As described above, according to the embodiment of FIGS. 1 and 5,
Since the voltage-time product of the input of the high-voltage transformer during the positive and negative half cycles in one cycle of the inverter operation becomes equal, DC bias is suppressed.

Therefore, since the magnetic flux density can be set large, a core having a small cross-sectional area can be used, and the transformer can be downsized.

Further, in suppressing the DC bias, the biased vibration of the iron core is reduced, so that the noise is also reduced.

FIG. 1 shows an example in which the tube voltage is controlled by controlling the phase difference. However, the tube voltage can also be controlled by controlling the operating frequency of the inverter.

That is, as shown in FIG. 2, the phase difference of T _r3 with respect to the phase and T _r2 of T _r4 for the transistor T _r1 is 0, is a method for varying the frequency.

 This embodiment is shown in FIG.

7 is the same as FIG. 1 except for the frequency control circuit 12. To control the output power supplied to the load 5,
The ratio F _i / F ₀ between the operating frequency F _i of the resonant frequency F ₀ and the inverter 2 of the leakage inductance Ls and the resonant capacitor 6 of the transformer 3, by connexion changes to the frequency control circuit 12 shown in FIG. 7 and the output The voltage is as shown in FIG. That is, in FIG. 8, the horizontal axis represents the F _i / F _0, the ratio V of the vertical axis and the input voltage V _i from the DC power source 1 and the output voltage V ₀ of the transformer 3 ₀
/ V _i , the relationship between F ₁ / F ₀ and the output voltage V ₀ / V _i is:
Using the load resistances R ₁ , R ₂ ,..., R _S (R ₁ > R ₂ >> R _S ) as parameters, the curve is as shown in FIG. Then, the resonance frequency F ₀ are the constant values and the leakage inductance L _S of the transformer 3 is determined by the resonant capacitor 6, it can be controlled by connexion output voltage V ₀ to changing the operating frequency F _i of the inverter 2.

FIG. 9 shows an example of the configuration of the frequency control circuit 12 of the frequency control type inverter shown in FIG. In FIG.
12i is an error hold circuit, which is a signal S from the error amplifier circuit 9.
₃ is a signal that outputs the signal I, and 12k is a frequency determination circuit that enables the output frequency to be changed according to the input voltage as shown in FIG.
And outputs two sawtooth waves having a gradient corresponding to the value of I in succession and compares them with a predetermined value.
Is configured to be output. 12j is a one-period determination circuit II that divides the pulse K and outputs a pulse J for setting one cycle of the inverter operation. 12l and 12m are pulse distribution circuits I and II, and the pulse of the demultiplexing number determination circuit 12k. The output K is input, and P ₁ ′ to P ₄ ′ are output.

The Kikan control of conventional frequency control method, as shown in the top row of FIG. 10 to be described below, the change in each half cycle of the positive and negative operation of the inverter according to the value of S ₃ generation of the pulse K (The gradient of the sawtooth wave changes as shown by the broken line), and the high-voltage transformer is magnetized. However, this embodiment can prevent that. Hereinafter, the operation of the frequency control circuit 12 of FIG. 9 will be described with reference to FIG. The In Figure 7, when the tube voltage setting signals S ₁ and the X-ray irradiation signal S ₄ is inputted, the error amplifying circuit by connexion frequency control circuit 12 to the output S ₃ of from 9, error-hold circuit holds the S ₃ Output to the frequency determination circuit 12k. The frequency determination circuit 12k generates a sawtooth wave E 'corresponding to the input I, and generates a pulse signal K when the sawtooth wave E' matches a predetermined value Q (or may be 0 at the time of starting). The first pulse signal K inputted to the pulse distribution circuit (I) 12l and pulse distribution circuit (II) 12m, then outputs a pulse signal P ₁ '~P _4' for driving the transistor T _r1 through T _r4 inverter 2 . Pulse signal P ₁ ′ ~
'Among the first P _1' P ₄ is the T _r1, and P ₄ 'is supplied via a drive circuit 11a, 11d to T _r4. On the other hand, P ₂ ′ and P ₃ ′
Keeps off state at first. The frequency determining circuit 12k generates a second pulse K when the sawtooth wave E 'having the gradient corresponding to the first input I matches the predetermined value Q. At this time, the drive pulses P ₁ ′ and P ₄ ′ are turned off, and conversely, P ₂ ′ and P ₃ ′ are turned on. Driving pulse P ₂ ', P _3' is the drive circuit 11b to the transistor T _r2 and T _r3, is supplied via 11c. Frequency determination circuit 1
2k continuously generates a sawtooth wave E 'having the same gradient as the first wave, and outputs a pulse K of the second wave when the predetermined values Q and E' become equal. The output K of the frequency determination circuit k is input to the one-period determination circuit 12j, and the one-period determination circuit 12j outputs a pulse J every two pulses of K. When the third pulse K is output, the outputs P ₂ ′ and P ₃ ′ of the pulse distribution circuits 12l and 12m are turned off,
Conversely, P ₁ ′ and P ₄ ′ are turned on again. On the other hand, the output J of 1 cycle determining circuit 12j is output to the error-hold circuit 12i, error hold circuit holds the output S ₃ of the error amplifier circuit at the time. The output I is output to the frequency determination circuit 12k, and the frequency determination circuit 12k newly sets the gradient of the saw-tooth wave and outputs it. Hereinafter, the above operation is repeated.

In the present embodiment described above, the control of the inverter of the frequency control method can be controlled in a uniform time by the positive and negative half cycles of one cycle of the operation of the inverter according to the error between the actual tube voltage and the set tube voltage. Therefore, the voltage-time product of the output from the inverter to the high-voltage transformer can be equalized.

In the embodiment of FIG. 1 and FIG. 7, an example has been described in which the tube voltage is controlled by independently controlling the phase difference or the frequency. However, the present invention is not limited to this. Needless to say, the present invention can be applied to the case where control is performed simultaneously.

In the above embodiment, the inverter is a full bridge type using a transistor, and the resonance circuit is a series resonance circuit. However, it is needless to say that the present invention is not limited thereto and can be modified. For example, in the case of frequency control, a switching element of the inverter may be replaced with a transistor and a self-turn-off element such as a thyristor may be used, or a push-pull inverter may be used instead of a full-bridge inverter. Further, the resonance circuit may use the leakage inductance of the high-voltage transformer and the stray capacitance of the secondary winding as the resonance element instead of the series resonance.

Further, the present invention can be applied to a system in which the DC power supply 1 is obtained by receiving AC from a commercial power supply, rectifying the DC power into DC, and smoothing the DC power.

〔The invention's effect〕

According to the present invention, DC bias of the high-voltage transformer is suppressed,
Since the magnetic flux density of the iron core can be set large, the size and weight of the high-voltage transformer can be reduced.

Further, there is an effect that magnetostrictive vibration of the iron core is reduced and noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the X-ray apparatus according to the present invention, FIG. 2 is a timing diagram showing an operation when controlling the output power to be maximum, and FIG. FIG. 4 is a diagram showing the relationship between the phase difference and the tube voltage using load resistance as a parameter, and FIG. 5 is a block diagram of the phase control circuit shown in FIG. , FIG. 6 is a timing diagram thereof, FIG. 7 is a circuit diagram of an X-ray apparatus according to another embodiment of the present invention, FIG. 8 is a diagram showing the relationship between frequency and tube voltage using load resistance as a parameter, FIG. 9 is a block diagram of the frequency control circuit of FIG. 7,
FIG. 10 is a timing diagram, and FIG. 11 is a diagram showing the relationship between the voltage and the frequency of the frequency determining circuit of FIG. 1 DC power supply 2 Inverter 3 Transformer 4
... Rectifier circuit, 5 ... Load (X-ray tube), 6 ... Resonant capacitor, 7 ... Voltage divider, 9 ... Error amplifier circuit, 10 ... Phase control circuit, 10c, 12i ... Error hold circuit, 11a-11d
...... drive circuit, 12 ...... frequency control circuit, T _r1 through T _r4 ...... transistor, D ₁ to D ₈ ...... diode.

Claims (2)

(57) [Claims] 1. A DC power supply, a resonant inverter for converting an output voltage of the DC power supply to a high-frequency AC, a high-voltage transformer for boosting an output voltage of the inverter, and a rectifier for rectifying an output voltage of the high-voltage transformer. A circuit, an X-ray tube to which an output voltage of the rectifier circuit is applied, and an operating phase or an operating frequency of the inverter or both of the operating points of the inverter to control a voltage applied to the X-ray tube. And an inverter type X-ray apparatus having
The control means includes: a positive signal for one cycle of the operation of the inverter;
Control signal holding means for holding a signal for controlling the operating point at a negative half cycle together, and operating point determining means for determining the operating point by comparing the output of the control signal holding means with a reference value; And the voltage-time product output from the inverter to the high-voltage transformer by making the operating point of the inverter determined by the operating point determining means constant between positive and negative half cycles of one cycle of the operation of the inverter. An inverter-type X-ray apparatus characterized by making them equal. 2. A DC power supply, a resonant inverter for converting an output voltage of the DC power supply into a high-frequency AC, a high-voltage transformer for boosting an output voltage of the inverter, and a rectifier for rectifying an output voltage of the high-voltage transformer. A circuit, an X-ray tube to which an output voltage of the rectifier circuit is applied, a tube voltage detector for detecting a voltage applied to the X-ray tube, a tube voltage setting signal, and a detection signal of the tube voltage detector. And the difference is amplified, and the control signal corresponding to the amplified signal controls the operating phase or operating frequency of the inverter or both of the operating points of the inverter and feeds back the voltage applied to the X-ray tube. And a control signal holding means for holding the control signal constant at positive and negative half periods of one cycle of the operation of the inverter. And an operating point determining means for determining an operating point of the inverter by comparing an output of the control signal holding means with a reference value, and determining an operating point of the inverter determined by the operating point determining means. An inverter-type X-ray apparatus wherein the positive and negative half periods of one cycle of the operation are constant to equalize a voltage-time product output from the inverter to the high-voltage transformer.