JP2777892B2 - Resonant inverter type X-ray device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus, and more particularly to a resonant inverter suitable for realizing miniaturization and weight reduction and controlling a wide range of loads from fluoroscopy to imaging. The present invention relates to an X-ray apparatus using the same.

[Conventional technology]

By increasing the input voltage of the high-voltage transformer,
The size of the transformer can be reduced. As such a technique, for example, there is a so-called series resonance type inverter type disclosed in US Pat. No. 4,225,788.

[Problems to be solved by the invention]

This series resonance type inverter uses the leakage inductance of a high-voltage transformer and the resonance of a capacitor connected in series to this transformer, and rectifies and smoothes an AC voltage to obtain a DC voltage. Is input to a bridge inverter composed of thyristors.

The output of the inverter is applied to a resonance circuit in which a primary winding of a high-voltage transformer and a resonance capacitor are connected in series, and a voltage induced in a secondary winding of the high-voltage transformer is rectified and smoothed to form an X-ray tube. Getting the voltage. The control of the output voltage in such an X-ray apparatus has been performed by varying the firing cycle of the thyristor and controlling the frequency of the inverter.

That is, when the ratio F _i / F ₀ between the resonance frequency F ₀ of the leakage inductance of the high-voltage transformer and the capacitance of the resonance capacitor and the inverter frequency F _i is approximately 1, the maximum occurs. To control the output power.

However, this method cannot reduce the output voltage to zero. Also, if the frequency of the inverter is reduced, the output voltage can approach zero, but if the frequency is reduced, the time product of the applied voltage applied to the high-voltage transformer increases. Must be increased. Accordingly, the size of the high-voltage transformer has been increased, and thus the size of the X-ray apparatus has been increased.

However, since there is a limit to the size of the high voltage transformer, it can not be too small operating frequency F _i of the inverter Conversely, been made in which the control range of the output voltage is limited.

Even if the operating frequency of the inverter at the rated load is higher than the audible frequency to reduce noise, if the operating frequency is reduced to reduce the X-ray tube voltage at light loads, the frequency becomes audible and noise is reduced. Big, X
There was a problem that the pulsation of the tube voltage also increased.

It is a first object of the present invention to provide an X-ray apparatus capable of realizing miniaturization of an X-ray apparatus and controlling output of a wide range of loads from fluoroscopy to imaging, in addition to the first object, A second object is to provide an X-ray apparatus capable of controlling the output of a wide range of loads with high accuracy.

[Means and actions for solving the problem]

The above object has a first series connection body including a DC power supply, a first switch connected to a positive electrode of the DC power supply, and a second switch connected to the negative electrode, and the first and second series connected bodies. It has a second series connection composed of a third switch and a fourth switch respectively provided in parallel with the second switch, and the first to fourth switches respectively connected in anti-parallel to the first to fourth switches. An inverter having a fourth diode for receiving direct current from the direct current power supply and converting the direct current into alternating current, and wherein the first switch and the second switch of the inverter alternate with a phase difference of 180 ° at the operating frequency of the inverter; The third switch and the fourth switch are turned on alternately with the same phase difference of 180 °, and the fourth switch is turned on after the first switch is turned on. An inverter control circuit for controlling a phase difference and a phase difference at which the third switch is turned on after the second switch is turned on, a transformer connected to the output side of the inverter and boosting the output voltage of the inverter, A rectifier that converts a voltage generated on the secondary side of the transformer into a DC voltage by a resonance between a leakage inductance parasitic to the transformer and another resonance element and a transformation ratio of the transformer, and an output voltage of the rectifier is smoothed. A resonant-type inverter-type X-ray apparatus having an X-ray tube to be applied to the transformer, wherein a capacitor having a capacitance larger than a stray capacitance existing between primary windings or secondary windings of the transformer is used. This is achieved by connecting in series with the primary winding of the transformer and utilizing the resonance between this capacitor and the leakage inductance of the transformer.

[Action]

In the present invention, the resonance circuit includes a leakage inductance of the high-voltage transformer and a capacitor having a capacitance larger than the stray capacitance existing between the primary winding and the secondary winding of the high-voltage transformer. A capacitor having a capacitance that is negligible is desirable, and this capacitor is connected in series with the primary winding of the transformer,
Utilizing the resonance between the capacitor and the leakage inductance of the transformer, the first to fourth switches of the inverter are connected to the operating frequency of the inverter (the resonance between the leakage inductance of the high-voltage transformer and the capacitance of the capacitor). A switching operation is performed at a frequency or a frequency close to the frequency to cause resonance.

The inverter turns on the first switch and the second switch alternately with a phase difference of 180 °, and the third switch and the fourth switch alternately with a phase difference of 180 °. If the turn-on of the switch and the turn-on of the fourth switch are performed with a phase difference of α, the period in which the first switch and the fourth switch are simultaneously turned on, that is, the period of (180 ° −α), A period in which the second switch and the third switch are simultaneously turned on, that is, a period of (180 ° −α) is a voltage application period to the load. When the phase difference α is changed from 180 ° to 0, the voltage is supplied to the load. The power can vary from a minimum, that is, 0 to a maximum.

As described above, the capacitor used for the resonance of the leakage inductance of the high voltage transformer is connected in series with the primary winding of the high voltage transformer, and the capacitance of the capacitor is set between the primary windings of the high voltage transformer or between two primary windings. Since the value is set to be larger than the stray capacitance existing between the next windings, resonance mainly occurs between the leakage inductance of the high voltage transformer and the capacitor, and the stray capacitance of the high voltage transformer is reduced. The flowing reactive current becomes very small.

Therefore, the current flowing through the inverter and the high-voltage transformer is also reduced, which is effective in reducing the size and reducing the loss.

〔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 first invention. This X-ray apparatus includes a DC power source 1 such as a secondary battery, an inverter 2, a transformer 3, and a resonance capacitor 6.
And a rectifier 4 and an X-ray space 5.

The inverter 2 converts the alternating current by receiving DC from the DC power source 1, the second connected to the transistor T _r1 and the negative electrode of the first switch connected to the positive pole of the DC power source 1 a first series connection composed of the transistor T _r2 as switch of the transistors T
a second series connection composed of the transistor T _r4 as transistors T _r3 and the fourth switch as the third switch provided in parallel to _r1 and T _r2, respectively to the respective transistors T _r1 through T _r4 consisting antiparallel-connected first diode D ₁ ~ fourth diode D ₄ Prefecture. Each of the above transistors 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 Ls and a stray capacitance Cs. 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
Ls is used as a resonance element.

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

Rectifier 4, the output voltage from the transformer 3 and converts the direct current to full-wave rectification, made of four diodes D ₅ to D _8. An X-ray tube 5 is provided on the output side of the rectifier 4.
Is connected. In FIG. 1, reference symbol _Ch denotes the capacitance of a high-voltage cable for applying the output voltage of the rectifier 4 to the X-ray tube 5, and smoothes the output voltage from the rectifier 4. .

Here, in the first invention, the transistors of the X-ray tube 5 a voltage to be applied (hereinafter referred to as "tube voltage") and current (hereinafter "tube current" hereinafter) of the setting signal to the I connexion the inverter 2 T _r1 Phase determining circuit 9 for determining the operating phase of ~ _Tr4
X together with provided, for inputting a signal for controlling the phase of operation is the transistor T _r1 through T _r4 in accordance with the output signal from the phase decision circuit 9, the controller outside the illustrated
A phase control circuit 10 that outputs a signal based on a line exposure signal is provided. Reference numerals 11a to 11d denote transistors T according to the control signal output from the phase control circuit 10, respectively.
a driving circuit for driving the _r1 through T _r4. By these phase determination circuit 9 and the phase control circuit 10, the transistor T _r2 of the transistor T _r1 as the first switch of the inverter 2 as the second switch is 180 ° at the operating frequency of the inverter 2 of alternately turns on by the phase difference, causes alternately turned on by the transistor T _r4 is also 180 ° phase difference between the transistor T _r3 as third switch as the fourth switch, the first transistor T _r1 is turned And then the fourth transistor _Tr4
The power supplied to the X-ray tube 5 is controlled by appropriately changing the phase difference at which the third transistor _Tr3 turns on after the second transistor _Tr2 turns on after the second transistor _Tr2 turns on. It has become.

Next, the operation of the X-ray apparatus configured as described above will be described. First, the main circuit components shown in FIG.
1, an inverter 2, a transformer 3, a rectifier 4, an X-ray tube 5, and a resonance capacitor 6) form an equivalent circuit as shown in FIG. That is, the transistors T _r1 through T _r4 of the inverter 2, the first switch 12a, respectively, the second switch 12b, a third switch 12c, denoted as the fourth switch 12d, the transformer 3 and the leakage inductance Ls It is represented by However, since the stray capacitance Cs which exists between between the primary winding of the transformer 3 or the secondary winding is very small compared to the capacitance C _r of the resonance capacitor 6 is omitted here. Note that the first one and a fourth switch 12 a to 12 d and the diode D ₁ to D ₄ connected in antiparallel to each switch 12 a to 12 d, the first arm 13a, respectively, the second arm 13b, a third Arm 13c and the fourth arm 13d. The operation of the main circuit component will be described with reference to the timing charts of FIGS. 3 and 4 using the equivalent circuit shown in FIG.

First, the operation in the case where control is performed so that the output power is maximized will be described with reference to FIG. In this case, the second
The operating phase of each switch 12a to 12d of the inverter 2 shown in the figure is changed as shown in FIGS. 3 (a) to 3 (d) so that the first switch 12a and the second switch 12b alternate with a phase difference of 180 °. And the fourth switch 12d and the third switch 12c are alternately turned on with a phase difference of 180 °, and the first switch 12d is turned on.
The phase difference at which the fourth switch 12d is turned on after a is turned on is set to zero, and both are turned on at the same time, and the phase difference at which the third switch 12c is turned on after the second switch 12b is turned on is set to zero, and both are set Control to turn on at the same time.

First, at time Ta ₁ of FIG. 3, by the energy of the resonance current it is leakage inductance Ls in FIG. 2, Ls → 6
_{→ D 1 → 1 → D 4} → 4 → C h → 4 → circuit Ls, and Ls → 6 →
D ₁ → 1 → D ₄ → 4 → 5 → 4 → Ls respectively. Here, for easy notation state flows resonance current it is divided into two circuits in the fourth diode D ₄ since, below, expressed as D ₄ → _(4, C _h and 5) → Ls It shall be. Thus, the first arm 13a and the fourth arm 13d, respectively flows negative current i ₁ and i ₄ (FIG. 3 (e), reference (f)). At this time, the first switch 12a and the fourth switch 12d are turned on, but do not affect the circuit through which current flows. Then, as the energy of the leakage inductance Ls decreases, the resonance current it approaches zero, as shown in FIG. 3 (i).

Next, at time Ta _2, the third resonance current it as shown in Figure (i) is zero, the resonant current it is the second diagram 1 → 12a → 6 → Ls → 4 → C h → 4 → 12d → 1 and 1 → 12a
→ 6 → Ls → 4 → 5 → 4 → 12d → 1 flow in the circuit, was incubated with increasing (FIG. 3 an arc of a resonant frequency determined by the leakage inductance Ls and the capacitance C _r of the resonance capacitor 6 (See (i)).

Next, at time Ta _3, as shown in FIG. 3 (a) ~ (d), the first switch 12a and the fourth switch 12d is turned off, which the second switch 12b and the third time Switch 1
2c turns on. However, the resonance current it is the energy of the leakage inductance Ls in FIG. 2, through the circuit Ls → (4, C _h and _{5) → D 3 → 1 →} D 2 → 6 → Ls. Accordance connexion, the second arm 13b and the third arm 13c, respectively flows negative current i ₂ and i ₃ (FIG. 3 (g), (h) see). Then, as the energy of the leakage inductance Ls decreases, the resonance current it approaches zero, as shown in FIG. 3 (i).

Next, at time Ta _4, when the resonance current it as shown in FIG. 3 (i) is zero, the resonant current it is the second diagram 1 → 12c → (4, C h and 5) → Ls → 6 → 12b → the flow in the circuit 1, increases in an arc of a resonant frequency determined by the leakage inductance Ls and the capacitance C _r of the resonance capacitor 6 (FIG. 3 (i) refer).

Then, at time ta _5, as shown in FIG. 3 (a) ~ (d), the second switch 12b and the third switch 12c is turned off, which the first time switch 12a and the fourth Switch 1
2d turns on. Thus, exactly becomes the same state as the state of the time Ta _1, hereafter repeats the above operation.

In the case of controlling the operation phase of the inverter 2 as described above, the first switch 12a and the fourth switch 12d are simultaneously turned on and off with a phase difference of zero, and the second switch 12b
And the third switch 12c turns on and off at the same time as the phase difference is zero, so that the current i1 of the _first arm 13a and the current of the fourth arm 13d as shown in FIGS. 3 (e) and 3 (f). the i ₄ becomes the same waveform, FIG. 3 (g), as shown in (h), and current i ₂ of the second arm 13b and the current i ₃ of the third arm 13c the same waveform. A period (Ta _{1 to} Ta ₃ ) in which the first switch 12a and the fourth switch 12d are simultaneously turned on,
The second switch 12b and duration of the third switch 12c is turned on at the same time (Ta ₃ to Ta _5), is obtained as a continuous state, the waveform of the output voltage vt of the inverter 2, as shown in FIG. 3 (j) ,
The voltage of the DC power supply 1 becomes a continuous square wave having positive and negative peak values, and its output power becomes maximum.

Next, the operation in the case where the output power is controlled to be small will be described with reference to FIG. At this time, the operating phases of the switches 12a to 12d of the inverter 2 shown in FIG. 2 are changed by 180 degrees as shown in FIGS. 4 (a) to 4 (d). The fourth switch 12d and the third switch 12c are alternately turned on with a phase difference of 180 °, and the first switch 12a is turned on with a phase difference of 180 °.
Is turned on, the phase difference at which the fourth switch 12d is turned on is shifted on as α, and the phase difference at which the third switch 12c is turned on after the second switch 12b is turned on is shifted as α. Control.

First, at time Tb ₁ of FIG. 4, the first switch 12a and the third switch 12c in the second view is on and the energy of the resonance current it is leakage inductance Ls, Ls →
6 → D ₁ → 12c → is flowing (4, C _h and 5) → circuit Ls. Accordance connexion, the first arm 13a, Fig. 4 (e) negative current i ₁ flows as shown in, the third arm 13c, as shown in FIG. 4 (h) positive current i ₃ flows. And
As the energy of the leakage inductance Ls decreases, the resonance current it approaches zero as shown in FIG. 4 (i).

Next, at time Tb _2, the resonance current it as shown in FIG. 4 (i) is zero, the resonant current it is the Ls → (4, C _h and _{5) → D 3 → 12a →} 6 → Ls flow circuit, increases in an arc of a resonance frequency determined by the leakage inductance Ls and the capacitance C _r of the resonance capacitor 6 (see FIG. 4 (i)). At this time, the first arm 13a is connected to the first arm 13a as shown in FIG.
First positive current i ₁ flows as shown in, the third arm 13c
, A negative current i ₃ starts to flow as shown in FIG.

Next, at time Tb _3, together with the third switch 12c, as shown in FIG. 4 (d) is turned off, the fourth switch 12d, as shown in FIG. 4 (b) is turned on. Then, the fourth
As shown in FIGS. 7A and 7B, the first switch 12a and the fourth switch 12d are both turned on, and the third diode D ₃ is turned on by turning on the fourth switch 12d. Is reverse biased and turned off, so the resonance current it is
In Figure 2 1 → 12a → 6 → Ls → (4, C h and 5) → 1
It flows in the circuit of 2d → 1. This period is shown in FIG.
(F), the current i ₁ of the first arm 13a and the current i ₄ of the fourth arm 13d is the same waveform.

Then, at time Tb _4, with the first switch 12a is turned off as shown in FIG. 4 (a), the second switch 12b as shown in FIG. 4 (c) is turned on. At this time, resonant current it by the energy of the leakage inductance Ls, through a circuit Ls → (4, C _h and _{5) → 12d → D 2 →} 6 → Ls. Accordance connexion, second the arm 13b, Fig. 4 negative current i ₂ flows as shown in (g), the fourth arm 13
The d, positive current i ₄ to flow as shown in FIG. 4 (f). Then, as the energy of the leakage inductance Ls decreases, as shown in FIG.
it approaches zero.

Next, at time Tb _5, when the fourth resonance current it as shown in Figure (i) is zero, the resonant current it is the second view _{Ls → 6 → 12b → D 4} → (4, C h and Flow in the circuit of 5),
Leakage inductance Ls and capacitance C _r of resonance capacitor 6
And draw an arc of the resonance frequency determined by
FIG. (I)).

Next, at time Tb _6, together with the fourth switch 12d, as shown in FIG. 4 (b) is turned off, the third switch 12c, as shown in FIG. 4 (d) is turned on. Then, the fourth
As shown in FIGS. 3 (c) and 3 (d), the second switch 12b and the third switch 12c are both turned on, so that the resonance current it becomes 1 → 12c → (4, C _h and 5) → Ls → 6 → 12b → 1. During this period,
As shown in FIGS. 4 (g) and (h), the second arm 13b
The same waveform currents i ₂ and current i ₃ of the third arm 13c.

Next, at time Tb _7, with a second switch 12b as shown in FIG. 4 (c) is turned off, Fig. 4 (a)
When the first switch 12a is turned on as shown in, it produces the exact same state as the state of the time Tb _1, hereafter repeats the above operation.

In the case of controlling the operation phase of the inverter 2 as described above, the first switch 12a and the fourth switch 12d have a phase difference α.
And turns on and off, and the second switch 12b
And the third switch 12c is turned on and off with a phase difference α, so that the period (Tb _{3 to} Tb ₄ ) during which the first switch 12a and the fourth switch 12d are simultaneously turned on, The period during which the switch 12b and the third switch 12c are on at the same time (Tb _{6 to} Tb ₇ ) is shorter than the on-period of each switch by α. Then, power is supplied from the DC power supply 1 to the X-ray tube 5 only during this period. Accordingly, as shown in FIG. 4 (j), the waveform of the output voltage vt of the inverter 2 changes the voltage of the DC power supply 1 between the positive and negative peak values during the intermittent period, that is, the period of (180 ° −α). It becomes an intermittent square wave. From this, by appropriately changing the phase difference α at which the first switch 12a and the fourth switch 12d are turned on and the phase difference α at which the third switch 12c of the second switch 12b is turned on, the respective switches are changed. The period in which 12a to 12d are simultaneously turned on can be changed, and the power supplied to the X-ray tube 5 can be controlled. That is, the above-mentioned phase difference α
The output power can be reduced by increasing
When the phase difference α is 180 °, there is no period during which the switches 12a to 12d are simultaneously turned on, and the output power can be reduced to zero.

The main circuit components shown in FIG. 2 that operate as described above are controlled by the phase determination circuit 9 and the phase control circuit 10 shown in FIG. Therefore, these phase determination circuit 9 and the phase control circuit 10, the operation for controlling the operating phase of each transistor Tr ₁ to Tr ₄ of the inverter 2 shown in Figure 1. First, when the supply tube voltage and tube current to the X-ray tube 5 as a load is determined, the tube current setting corresponding to the tube voltage setting signal S ₁ and the tube current corresponding to the tube voltage signal S
₂ is input to the phase determination circuit 9 from a controller (not shown). Here, as shown in FIG. 5, the phase determination circuit 9 sets the horizontal axis to the phase difference α and the vertical axis to the tube voltage V of the X-ray tube 5.
And the relationship between the phase difference α and the tube voltage V is represented by a load resistance value
_{R 1, R 2, R 3} , ... (R 1> R 2> R 3) and the like a table of a graph representing a predetermined curve as a parameter memory or function generator or an operational amplifier. And
The phase determination circuit 9 obtains load resistance values R ₁ , R ₂ ,... From the tube voltage setting signal S ₁ and the tube current setting signal S ₂ , and uses the relationship of FIG. seeking the R ₃ and parameter intersection of the tube voltage V to be set this curve to determine the phase difference α of operation of the transistors Tr ₁ to Tr ₄ of the inverter 2. Then, the phase signal S ₃ corresponding to the phase difference α is output from the phase determining circuit 9, and inputs to the phase control circuit 10. In the phase control circuit 10, the transistor Tr ₄ along with making the control signal the transistors Tr ₁ to Tr ₄ from the phase signal S ₃ is turned on and off, as the transistor Tr ₁ as the first switch fourth switch There create a control signal for controlling a phase difference alpha transistor Tr ₃ is turned on the phase difference to turn on alpha, and the transistor Tr ₂ as a second switch as the third switch. And the phase control circuit
By X-ray exposure signal S ₄ is inputted from an unillustrated controller 10, the phase control circuit 10 sends a control signal described above created the respective drive circuits 11 a to 11 d. Thus, the drive circuits 11a~11d, each transistor Tr ₁ in accordance connexion inverter 2 to the control signal from the phase control circuit 10 through T
to drive the r _4.

In this manner, when each of the transistors Tr ₁ to Tr ₄ are begins operation, Figure 3 or the fourth 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 provided with the leakage inductance Ls 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.

FIG. 6 is a circuit diagram showing an embodiment of the X-ray apparatus according to the second invention. For the sake of simplicity, parts having the same configuration and the same function as the first invention shown in FIG.
The same reference numerals are given and the description is omitted. The second invention is a voltage divider 14 for detecting a tube voltage applied to the X-ray tube 5.
The detection signal from the voltage divider 14 and a preset target voltage signal (tube voltage setting signal S ₁ ) are input to amplify the difference, and the difference is used to amplify the transistors Tr _{1 to} Tr of the inverter 2. _4. An error amplification phase determination circuit 15 for determining the operation phase of ₄ is provided.
A signal for controlling the phase of the operation the transistors Tr ₁ to Tr ₄ in accordance with the output signal from 15, provided with a phase control circuit 10 which by connexion outputs the X-ray exposure signal S ₄ input from the controller outside the illustrated It is a thing. Reference numeral 16 denotes a signal conversion circuit that converts the signal detected by the voltage divider 14 into a signal suitable for use in the error amplification phase determination circuit 15. By these divider 14 and the error amplifier phase determination circuit 15 and the phase control circuit 10, the transistor Tr ₂ of the transistor Tr ₁ as a first switch of the inverter 2 as the second switch is of the inverter 2 1 at operating frequency
The transistor Tr ₃ as a third switch and the transistor Tr ₄ as a fourth switch are alternately turned on with a phase difference of 80 °, and the first transistor Tr ₁ is also turned on with a phase difference of 180 °. Yotsute to but the phase difference and the second transistor Tr ₂ the third transistor from turning on Tr ₃ of the fourth transistor Tr ₄ is turned from the turn-on appropriately changing the turn-on phase difference, the X-ray The power supplied to the tube 5 is feedback-controlled.

Next, the operation of the thus configured X-ray apparatus of the second invention will be described. First, when a tube voltage to be supplied to the X-ray tube 5 is determined, a tube voltage setting signal S ₁ corresponding to the tube voltage is set.
Is input to the error amplification phase determination circuit 15 from a controller (not shown) as a target voltage signal. On the other hand, this error amplification phase determination circuit 15, the tube voltage detection signal S ₅ corresponding to the current tube voltage converted by the signal conversion circuit 16 detected by the voltage divider 14 is inputted. Then, the error amplifier phase determination circuit 15 detects an error between the tube voltage setting signals S ₁ and the tube voltage detection signal S _5, the error proportional - treated with such integral control, the magnitude of the error Correspondingly each transistor of inverter 2
The phase difference α of the operation of Tr _{1 to} Tr ₄ is determined. Then, according to the phase difference α, the phase signal S ₃ is converted into the error amplification phase determination circuit.
It is output from 15 and input to the phase control circuit 10. At this time, before the start of the X-ray exposure, since the tube voltage detection signal S ₅ with respect to the tube voltage setting signals S ₁ is zero, the phase difference α so that it can supply the maximum power is set to zero.

Then, in the phase control circuit 10, along with making the control signal the transistors Tr ₁ to Tr ₄ from the phase signal S ₃ is turned on and off, the transistor Tr ₁ as a first switch as a fourth switch Transistor T
phase difference r ₄ is turned on alpha, and the transistor Tr ₂ as a second switch is a transistor Tr ₃ of the third switch to create a control signal for controlling a phase difference alpha to turn. By X-ray exposure signal S ₄ from the controller outside shown in the phase control circuit 10 is inputted, the phase control circuit 10 sends a control signal described above created the respective drive circuits 11 a to 11 d. Thus, the drive circuits 11a~11d drives each of the transistors Tr ₁ to Tr ₄ of the slave connexion inverter 2 to the control signal from the phase control circuit 10.

In this manner, when each of the transistors Tr ₁ to Tr ₄ are begins operation, FIG. 3 or the resonance current it as shown in FIG. 4 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 amplification phase determination circuit 15, a phase difference The operation is performed to increase α, and the supply of power from the DC power supply 1 is reduced. When the tube voltage of the X-ray tube becomes substantially equal to the set value, the inverter 2 operates at a phase in which power equal to the set tube voltage and tube current can be supplied from the DC power supply 1. At this time, the inverter 2 is connected to the leakage inductance of the transformer 3.
Ls to operate at a resonance frequency or a frequency close to that of the capacitance C _r of the resonance capacitor 6.

FIG. 7 is a circuit diagram showing another embodiment of the second invention. In this embodiment, a DC power supply 1 is obtained by receiving an AC from a commercial power supply, rectifying the DC power into a DC power, and smoothing the DC power. In the figure, reference numeral 17 denotes a rectifier for full-wave rectification of the received commercial power, and includes four diodes D _{9 to} D _9.
Consists of _twelve . Symbol L 'is an inductance,
Reference numeral C 'denotes a capacitance, and the output of the rectifier 17 is smoothed by the inductance L' and the capacitance C '. In the case of this embodiment, the output power can be further increased as compared with the embodiment shown in FIG. 6, and for example, power of several tens of kW to 100 K can be supplied.

The first view and Figure 6, in Figure 7, the transistor Tr ₁ to Tr ₄ as switching-element of the inverter 2
However, the present invention is not limited to this.
For example, GTO may be used.
OS FET, IGBT, SI transistor, SI thyristor, or the like may be used. Further, the load is not limited to the X-ray tube 5 but may be applied to any load requiring a DC output of a relatively high voltage. Further, the error amplification phase determination circuit 15 shown in FIGS. 6 and 7 is generally based on proportional-integral control, but is not limited to this, and is converted into a digital value once and controlled by software. May be applied.

〔The invention's effect〕

The present invention is configured as described above, and utilizes the resonance between the leakage inductance of the high-voltage transformer and a capacitor having a capacitance larger than the stray capacitance of the high-voltage transformer connected in series with the leakage inductance. As a result, the reactive current flowing through the floating capacitance of the high-voltage transformer is reduced, and the output power can be changed from zero to the maximum by the phase control of the inverter 2. Can be extended. Also, in order to control the output power, without changing the operating frequency Fi of the inverter 2 as in the related art, it is possible to prevent the cross-sectional area of the core of the transformer 3 from being increased by lowering the operating frequency Fi, The transformer 3 can be prevented from increasing in size. Therefore, the entire device can be downsized. Furthermore, when the operating frequency Fi of the inverter 2 at the rated load is higher than the audible frequency to reduce the noise, the operating frequency Fi is not changed in the subsequent control of the output voltage, and the low noise state is obtained. At the same time, the waveform of the pulsation of the tube voltage is small. In the second invention, in addition to the effect of the first invention, the current voltage applied to the load is detected, and the operation phase of each switch of the inverter 2 is determined from the error with the target voltage signal. By performing feedback control of the power supplied to the load, more accurate control of the output power can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the X-ray apparatus according to the first invention, FIG. 2 is an equivalent circuit showing a main circuit component of the X-ray apparatus shown in FIG. 1, and FIG. FIG. 4 is a timing chart showing the operation in the case of controlling the output power to be maximum, FIG. 4 is a timing chart showing the operation in the case of controlling the output power to be small, and FIG. FIG. 6 is a graph showing the relationship with voltage as a parameter of load resistance value, FIG. 6 is a circuit diagram showing one embodiment of the X-ray apparatus according to the second invention, and FIG. 7 shows another embodiment of the second invention. It is a circuit diagram. 1 DC power supply 2 Inverter 3 Transformer 4
Rectifier, 5 load (X-ray tube), 6 resonant capacitor, 9 phase determining circuit, 10 phase control circuit, 11a
~ 11d ... Drive circuit, 12a ... First switch, 12b ...
Second switch, 12c… Third switch, 12d… Fourth switch, 14… Voltage divider, 15… Error amplification phase determination circuit, 17… Rectifier, Tr _{1 to} Tr ₄ … Transistor D _{1 to} D
₁₂ ... Diode, C ... Capacitance, Ls ... Transformer leakage inductance, L '... Inductance, C' ...
Capacitance.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05G 1/32 H02M 7/48

Claims (1)

(57) [Claims] A first switch connected to a positive electrode of the DC power supply and a second switch connected to a negative electrode of the DC power supply; It has a second series connection composed of a third switch and a fourth switch respectively provided in parallel with the second switch, and the first to fourth switches respectively connected in anti-parallel to the first to fourth switches. Having a fourth diode,
An inverter that receives direct current from the direct current power source and converts it to alternating current, and the first switch and the second switch of the inverter are turned on alternately with a phase difference of 180 ° at the operating frequency of the inverter, and the third switch And the fourth switch are turned on alternately with a phase difference of 180 °, and the third switch is turned on after the first switch is turned on and the fourth switch is turned on. An inverter control circuit for controlling a phase difference at which a switch is turned on; a transformer connected to an output side of the inverter to boost an output voltage of the inverter; and a resonance between a leakage inductance parasitic to the transformer and another resonance element. A rectifier for converting a voltage generated on the secondary side of the transformer into a DC voltage by a transformation ratio of the transformer, and an output of the rectifier. X to which a voltage is applied is smoothed
In a resonance type inverter X-ray apparatus having a wire tube,
A capacitor having a capacitance larger than the stray capacitance existing between the primary windings or the secondary windings of the transformer is connected in series with the primary winding of the transformer, and this capacitor is connected to the primary winding of the transformer. A resonance type inverter X-ray apparatus characterized by utilizing resonance with a leakage inductance.