JP6200842B2 - X-ray high voltage apparatus and X-ray diagnostic imaging apparatus including the same - Google Patents

Description

  The present invention relates to an X-ray high voltage apparatus and an X-ray image diagnostic apparatus for supplying a high voltage to an X-ray tube mounted on an X-ray apparatus such as an X-ray CT apparatus or an X-ray imaging apparatus.

  In an X-ray apparatus such as an X-ray CT apparatus or an X-ray imaging apparatus, a high voltage of about several tens of kV to 100 kV needs to be supplied to the X-ray tube. Therefore, for example, a configuration disclosed in Patent Document 1 or Patent Document 2 is used as the X-ray high voltage apparatus. In the X-ray high voltage apparatus described in Patent Document 1 and Patent Document 2, a converter that inputs a commercial power supply and outputs a DC voltage, an inverter that inputs a DC voltage and generates a high-frequency AC voltage, and boosts the AC voltage The transformer is supplied to the rectifier circuit, and a multi-stage voltage doubler rectifier circuit and a Cockcroft-Walton circuit for generating a DC voltage by inputting an AC voltage, and supplying a high DC voltage to the X-ray tube. Yes. The voltage of an X-ray tube (hereinafter referred to as tube voltage) required for a general X-ray apparatus is a high voltage of about several tens of kV to 100 kV. A configuration in which a plurality of units are connected in series, or a configuration in which a voltage doubler rectifier circuit or a Cockcroft-Walton circuit is multistaged is used.

  For this reason, the volume of the smoothing capacitor occupying the rectifier circuit is large, and the miniaturization of the capacitor is required. To reduce the size of the capacitor, it is effective to reduce the capacitance of the capacitor. However, if the capacitance of the smoothing capacitor is simply reduced, there arises a problem that the pulsation of the tube voltage increases. Since the pulsation of the tube voltage affects the image quality, the X-ray high voltage apparatus is required to suppress the pulsation of the tube voltage below a specified value.

  As means for solving this problem, increasing the drive frequency of the inverter is known. By increasing the drive frequency of the inverter, the AC voltage supplied to the rectifier circuit can be increased, so that the capacitor capacity can be reduced while suppressing the pulsation of the tube voltage. However, when the drive frequency of the inverter is increased, there is a problem that switching loss increases and cooling of the switching element becomes difficult.

  Patent Document 3 is disclosed as means for reducing switching loss of an inverter. In the induction heating device described in Patent Document 3, for the purpose of induction heating of a load having a low specific resistance of the pan itself, such as an aluminum pan or a multi-layer pan in which the aluminum material shows many components in the thickness of the bottom of the pan. The heating coil and the resonance capacitor connected in series are connected in parallel with the switching element, and the heating coil so that the frequency of the resonance current generated by the heating coil and the resonance capacitor is at least twice the drive frequency of the inverter. By defining the inductance of the capacitor and the capacitance of the resonant capacitor, the frequency of the resonant current supplied to the load is increased without increasing the switching loss, and heating of the load with a low specific resistance of the pan such as an aluminum pan is attempted. .

Japanese Patent Laid-Open No. 10-41093 JP 2009-43571 A JP 2001-68260 A

  However, in the technique described in Patent Document 3, since the heating coil and the resonant capacitor are connected in series, the load resistance, the inductor, and the capacitor are equivalently connected in series. Therefore, in order to make the frequency of the resonance current more than twice the drive frequency of the inverter, that is, to maintain a plurality of resonance operations during one cycle of the drive frequency of the inverter, the load resistance is required to be sufficiently small. Generally, since an X-ray tube is a high voltage / small current load, it is known that the equivalent load resistance is as large as several tens kΩ to several MΩ. Therefore, when the technique of the above document is applied to an X-ray high voltage apparatus, there is a problem that it is difficult to maintain a plurality of resonance operations during one cycle of the drive frequency of the inverter because the load resistance is large. . Patent Document 3 does not disclose any technique related to a circuit configuration that includes a rectifier circuit on the secondary side of a transformer and supplies a DC voltage to a load.

  In order to solve the above problems, an X-ray high-voltage apparatus according to the present invention includes a transformer, an inverter that is electrically connected in parallel between a DC power source and the transformer, and converts a DC voltage into an AC voltage. A rectifier circuit that is electrically connected in parallel between the transformer and the X-ray tube, smooths the AC voltage and supplies the DC voltage to the X-ray tube, a control unit that controls the inverter, and the inverter A resonance circuit that is electrically provided between the inverter and the rectifier circuit and includes the transformer, and a frequency of a resonance current supplied from the inverter to the resonance circuit is By setting the resonance circuit to be (natural number + 1) times the frequency for driving the inverter, the frequency of the AC voltage applied to the rectifier circuit is driven by the inverter. Of frequency (natural number +1) and double.

  According to the present invention, even in an X-ray high voltage device having a large load resistance, it becomes possible to supply an AC voltage having a frequency higher than the drive frequency of the inverter to the rectifier circuit while suppressing an increase in switching loss of the inverter. It is possible to provide an X-ray high-voltage device that can be miniaturized.

1 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 1. FIG. FIG. 3 is a waveform diagram for explaining the operation of the X-ray high voltage apparatus according to the first embodiment. FIG. 3 is a waveform diagram for explaining the operation of the X-ray high voltage apparatus according to the first embodiment. FIG. 3 is a circuit configuration diagram of an X-ray high voltage apparatus according to a second embodiment. The wave form diagram explaining the operation | movement of the X-ray high voltage apparatus of Example 2. FIG. FIG. 3 is a circuit configuration diagram of an X-ray high voltage apparatus according to a second embodiment. FIG. 3 is a circuit configuration diagram of an X-ray high voltage apparatus according to a second embodiment. FIG. 6 is a circuit configuration diagram of an X-ray high voltage apparatus according to a third embodiment. FIG. 6 is a circuit configuration diagram of an X-ray high voltage apparatus according to a fourth embodiment. The wave form diagram explaining the operation | movement of the X-ray high voltage apparatus of Example 4. FIG. FIG. 6 is a circuit configuration diagram of an X-ray high voltage apparatus according to a fifth embodiment. FIG. 9 is a waveform diagram for explaining the operation of the X-ray high voltage apparatus according to the fifth embodiment. The wave form diagram explaining the operation | movement of the X-ray high voltage apparatus of Example 6. FIG.

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

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 1 of the present invention. This X-ray high voltage apparatus uses a DC power source 1 as a power source, and includes an inverter 2, a resonant inductor 3, a transformer 4, a resonant capacitor 5, a rectifier circuit 6, and control means 8, and is an X-ray as a load. A high DC voltage is supplied to the tube 7.

  The inverter 2 receives the DC power source 1 and outputs an AC voltage having an arbitrary frequency. The inverter 2 includes switching elements Q1 to Q4 that are bridge-connected, and antiparallel diodes D1 to D4 are connected to the switching elements Q1 to Q4, respectively. The transformer 4 magnetically couples the primary winding N1 and the secondary winding N2 with the core Tr1.

  The resonant inductor 3 is connected in series with the primary winding N1 of the transformer 4, and the resonant capacitor 5 is connected in parallel between the terminals of the secondary winding N2 of the transformer 4. The resonant inductor 3, the transformer 4, and the resonant capacitor 5 constitutes the resonant circuit 100.

  The rectifier circuit 6 is composed of bridge-connected rectifier diodes Dr1 to Dr4 and a smoothing capacitor Cm. The rectifier 6 rectifies and smoothes the AC voltage output between the terminals of the resonance capacitor 5 and supplies the DC voltage to the X-ray tube 7. To do. In FIG. 1, the rectifying capacitors Dr1 to Dr4 are shown as one element, but a plurality of elements may be connected in series. Further, when a plurality of elements are connected in series, a balance resistor that equalizes the voltage applied to the elements may be connected in parallel to the elements.

  The control means 8 outputs the gate signals G1 to G4 to the switching elements Q1 to Q4 so that the output voltage of the rectifier circuit 6 becomes a target value. The drive frequency fsw of the inverter is controlled by the control means 8. By configuring as described above, the inverter 2 is a resonant inverter in which a current (hereinafter referred to as a resonance current) supplied to the resonance circuit 100 including the resonance inductor 3 and the resonance capacitor 5 is sinusoidal. Operate.

It is known that the X-ray tube 7 viewed from the primary side of the transformer 4 is equivalently expressed as a resistance. Here, the combined impedance of the rectifier circuit 6 and the X-ray tube 7 viewed from the transformer primary side is Z0, the inductance of the resonant inductor 3 is L1, and the capacitance of the resonant capacitor 5 is C2. The impedance Z1 including the resonance circuit 100 and the load is approximately:
Z1 = jωL1 + 1 / (Z0 + 1 / jωC2) Equation (1)
It becomes. From Equation (1), the resonance frequency f1 is Equation (2).

f1 = 1 / (2 × √ (1 / (L1 × C2) −1 / (4 × C2 ^ 2 × Z0 ^ 2))) Equation (2)
From the equation (2), it can be seen that the resonance frequency f1 is affected by the combined impedance Z0 of the resonance inductor 3, the resonance capacitor 5, the X-ray tube 7 and the rectifier circuit 6.

  Further, in order to suppress the pulsation ΔVx of the tube voltage Vx, it is necessary to supply the current Id1 to the smoothing capacitor Cm every period of the resonance current I1, and therefore, the relationship between the AC voltage Vc2 and the tube voltage Vx is Vc2> Vx. It is necessary to set the constant of the resonance circuit 100 so that This means that the resonance circuit 100 is set so that attenuation of the resonance current I1 is suppressed, that is, the time constant τ1 of the resonance circuit 100 is sufficiently large. Here, the time constant τ1 of the resonance circuit 100 in the X-ray high-voltage apparatus of FIG. 1 is approximately expressed by equation (3).

τ1 = 2 × C2 × Z0 (3)
From the above equation (3), it can be seen that the time constant τ1 is determined by the impedance Z0 of the load and the capacitance C2 of the resonant capacitor 5. Since the impedance Z0 of the load is determined by the load condition, it is necessary to set the capacitance C2 of the resonant capacitor 5 so that the desired time constant τ1 is obtained.

  FIG. 2 shows operation waveforms of the X-ray high voltage apparatus of FIG. Here, in all the operation waveform diagrams including FIG. 2, the current flowing from the top to the bottom of each element in the circuit diagram of FIG. 1 is positive, and the current flowing from the left to the right is positive. Hereinafter, the operation of the X-ray high voltage apparatus according to Embodiment 1 of the present invention will be described with reference to FIG. In the operation of FIG. 2, the resonant inductor 3 and the resonant capacitor are set such that the frequency fr of the resonant current I1 supplied from the inverter using the formulas (2) and (3) is three times the drive frequency fsw of the inverter. An example in which 5 is set is shown.

The control means 8 outputs gate signals G1 to G4 so that the inverter 2 in FIG. 1 performs a basic operation as a full bridge inverter. Switching elements Q1 and Q4 Further, the upper and lower arms composed of switching elements Q1 and Q2 and the upper and lower arms composed of switching elements Q3 and Q4 are switched so that the switching elements Q2 and Q3 are simultaneously turned on or off. Let In FIG. 2, the on-time duties of the four switching elements Q1 to Q4 are each 50%.
(Mode 1) t0 to t1
First, an operation during a period (Mode 1) in which the switching elements Q1 and Q4 are on will be described. When the switching elements Q1 and Q4 are turned on, if the voltage of the DC power supply 1 is expressed as Vin, the output voltage V1 of the inverter is approximately + Vin. At this time, a resonance current flows through the path of the diode D4, the resonance capacitor 5, the resonance inductor 3, and the diode D1, the energy of the resonance inductor 3 is released, and the energy is stored in the resonance capacitor C5. When all the energy of the resonant inductor 3 is released, the polarity of the resonant current I1 is reversed, and the resonant current flows through the path of the DC power source 1, the switching element Q1, the resonant inductor 3, the resonant capacitor 5, and the switching element Q4. 5 energy is released, and again stores energy in the resonant inductor. Here, by setting the resonant circuit 100 so that the frequency fr1 of the resonant current I1 is three times the drive frequency fsw of the inverter, the resonant inductor 3 and the resonant capacitor are turned on while the switching elements Q1 and Q4 are on. 5, the exchange of energy is repeated, and the polarity of the resonance current I1 is also inverted repeatedly. At this time, an AC voltage Vc21 having a phase delayed by π / 2 with respect to the resonance current I1 is generated at both ends of the resonance capacitor 5. As a result, an AC voltage having a frequency higher than the drive frequency fsw of the inverter can be applied to the rectifier circuit 6, and the current Id1 can be supplied to the smoothing capacitor Cm.
(Mode 2) t1 to t2
When switching elements Q1 and Q4 are turned off at timing t1 and switching elements Q2 and Q3 are turned on, resonance current I1 flows through the path of diode D2, resonance inductor 3, resonance capacitor 5, and diode D3. To store energy in the resonant inductor 3. At this time, if the voltage of the DC power supply 1 is Vin, the output voltage V1 of the inverter is approximately −Vin. When all the energy of the resonance capacitor is released, the DC power source 1, the switching element Q 3, the resonance capacitor 5, the resonance inductor 3. The energy of the resonant inductor 3 is released through the path of the switching element Q2, and the energy is stored in the resonant capacitor 5. While the switching elements Q2 and Q3 are on, the polarity of the resonance current I1 is repeatedly inverted similarly to Mode1. At this time, an AC voltage Vc21 having a phase advanced by π / 2 with respect to the resonance current I1 is generated at both ends of the resonance capacitor 5. As a result, an AC voltage having a frequency higher than the drive frequency fsw of the inverter can be applied to the rectifier circuit 6, and the current Id1 can be supplied to the smoothing capacitor Cm. Hereinafter, in a steady state, Mode 1 and Mode 2 are repeated.

  As described above, in the X-ray high voltage apparatus according to the present embodiment, the resonance frequency f1 of the resonance circuit 100 including the resonance inductor 3 and the resonance capacitor 5 is approximately three times the drive frequency fsw of the inverter. By setting the inductance L1 of the inductor 3 and the capacitance C2 of the resonance capacitor 5, the frequency of the resonance current I1 is set to three times the drive frequency fsw of the inverter, and the frequency of the AC voltage applied to the rectifier circuit 6 is changed to the inverter. The driving frequency fsw can be set to three times. Hereinafter, this operation is referred to as a triple resonance operation.

  As a result, the pulsation ΔVx of the tube voltage Vx can be reduced without increasing the drive frequency fsw of the inverter, and therefore, rectification is performed while suppressing an increase in switching loss as compared with the method of increasing the drive frequency fsw of the inverter. It is possible to reduce the smoothing capacitor capacitance Cm of the circuit 6.

In the example shown in FIG. 1, the switching elements Q1 to Q4 are IGBTs, but may be MOSFETs. When the switching elements Q1 to Q4 are MOSFETs, parasitic diodes can be used as antiparallel diodes. Further, although the resonant inductor 3 is connected in series with the winding N1, the leakage inductance of the transformer 4 may be used as the resonant inductor 3. Further, the resonance inductor 3 may be connected in series with the secondary winding of the transformer. Further, although the resonant capacitor 5 is connected in parallel with the secondary winding N2 of the transformer 4, the same effect can be obtained when the resonant capacitor 3 is connected in parallel with the winding N1 between the resonant inductor 3 and the winding N1. It goes without saying that can be obtained. Further, although the resonant capacitor 5 is connected in parallel between the terminals of the winding N2, the parasitic capacitance of the winding N2 may be used. In some cases, a desired capacitance cannot be obtained only by the parasitic capacitance of the winding N2. In that case, an external capacitor may be connected between the terminals of the winding N1 or between the terminals of the winding N2, and the combined capacitance of the parasitic capacitance of the winding N2 and the external capacitor may be used as the resonance capacitor 5. In this embodiment, the rectifier circuit has a bridge configuration, but the present invention is not limited to this. For example, a voltage doubling circuit or a half-wave rectifying circuit may be used as the rectifying circuit.
<Modification of Example 1>
A modification of the first embodiment will be described with reference to FIG.

  FIG. 3 shows an example in which the resonant inductor 3 and the resonant capacitor 5 are set so that the resonant frequency f1 is twice the drive frequency fsw using the formula (2) and the formula (3). The difference from the operation waveform of FIG. 2 is that the on-time duty of the switching elements Q1 and Q4 is made smaller than 50%, and the on-time duty of the switching elements Q2 and Q3 is made larger than 50%. Detailed operation will be described below.

(Mode 1)
First, when the switching elements Q1 and Q4 are on, the resonance current flows through the path of the diode D4, the resonance capacitor 5, the resonance inductor 3, and the diode D1 by the energy stored in the resonance inductor 3, and the energy of the resonance inductor 3 is released. Is done. When the energy of the resonant inductor is completely discharged, the polarity of the resonant current I1 is reversed, and the resonant current flows through the path of the DC power source 1, the switching element Q1, the resonant inductor 3, the resonant capacitor 5, and the switching element Q4, and the resonant inductor 3 stores energy again. At this time, an AC voltage Vc2 having a phase delayed by π / 2 from the resonance current I1 is generated at both ends of the resonance capacitor 5, and the AC voltage is applied to the rectifier circuit 6. When the voltage of the DC power supply is Vin, the inverter output voltage V1 in Mode 1 is approximately + Vin.
(Mode2)
When the switching elements Q1 and Q4 are turned off and the switching elements Q2 and Q3 are turned on at time t1, the mode shifts to Mode2. In Mode 2, first, a resonance current flows through the path of the diode D 2, the resonance inductor 3, the resonance capacitor 5, and the diode D 3, releases the energy of the resonance capacitor 5, and accumulates energy in the resonance inductor 3. When the energy of the resonance capacitor 5 is completely discharged, the polarity of the resonance current I1 is reversed, and the resonance current flows through the path of the switching element Q3, the resonance capacitor 5, the resonance inductor 3, and the switching element Q2, and again flows into the resonance capacitor 5. Accumulate energy. At this time, a voltage whose phase is delayed by π / 2 from the resonance current I 1 is generated at both ends of the resonance capacitor 5, and the AC voltage Vc 2 is applied to the rectifier circuit 6. When the voltage of the DC power supply is Vin, the inverter output voltage V1 in Mode 2 is approximately −Vin. Hereinafter, in the steady state, Mode 1 and Mode 2 are repeated as in FIG.

  As described above, in the operation shown in FIG. 3, the frequency of the resonant current I1 and the frequency of the voltage Vc2 across the resonant capacitor 5 are twice the inverter drive frequency fsw, and the rectifier circuit 6 is doubled as the switching element. It is possible to apply a voltage having a frequency of. Hereinafter, this phenomenon is called double resonance. Further, by changing the settings of the resonant inductor 3 and the resonant capacitor 5, the frequency of the resonant current I1 can be set to an arbitrary multiple such as four times or five times the drive frequency fsw of the inverter.

  As described above, in this embodiment, the resonance inductor 3 is provided in series with the primary winding N1 of the transformer 4, and the resonance capacitor 5 is provided between the resonance inductor 3 and the rectifier circuit 6 in parallel with the rectifier circuit 6. By setting the inductor 3 and the resonance capacitor 5, the frequency of the resonance current I1 can be (natural number + 1) times the drive frequency fsw of the inverter, and the frequency of the AC voltage applied to the rectifier circuit 6 is the drive frequency fsw of the inverter. It can be seen that it can be (natural number + 1) times.

(Series resonant capacitor 210, rectifier circuit is voltage doubler rectifier circuit)
Next, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 4 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 2 of the present invention. Similar to the X-ray high voltage apparatus of the first embodiment, this X-ray high voltage apparatus uses a DC power source 1 as a power source, an inverter 2, a resonant inductor 203, a transformer 204, a resonant capacitor 205, a rectifier circuit 206, and the like. The control means 208 is configured to supply a high DC voltage to the X-ray tube 7 as a load. Hereinafter, differences from the first embodiment will be described.

  The present embodiment is different in that the resonant capacitor 210 is connected in series with the primary winding N11 of the transformer 204 and the rectifier circuit 206 is configured by connecting multiple voltage rectifier circuits in multiple stages. The resonant capacitor 210 constitutes the resonant circuit 101 from the resonant inductor 203, the resonant capacitor 205, and the transformer 204.

  The rectifier circuit 206 includes rectifier capacitors Cd1 and Cd2, rectifier diodes Dr11 to Dr14, and a smoothing capacitor Cm1, a double voltage rectifier circuit 206a, rectifier capacitors Cd3 and Cd4, rectifier diodes Dr15 to Dr18, and a smoothing capacitor Cm2. The voltage doubler rectifier circuit 206b is connected in a multistage configuration. In the rectifier circuits 206a and 206b, one end of the smoothing capacitor Cm1 and one end of the smoothing capacitor Cm2 are connected, and the X-ray tube 7 is connected to the other end of the smoothing capacitor Cm1 and the other end of the smoothing capacitor Cm2. In the transformer 204, the primary winding N11 and the secondary windings N21 and N22 are magnetically coupled by the core Tr2. One end of winding N21 and one end of winding N22 are connected, the other end of winding N21 is connected to one end of rectification capacitor Cd1, and the other end of winding N22 is connected to one end of rectification capacitor Cd2. A connection point of the windings N21 and N22 is connected to one end of the smoothing capacitor Cm. A resonant capacitor 205a and a resonant capacitor 205b are connected in parallel between the terminals of the windings N21 and N22, respectively. A voltage sensor 9 for detecting the voltage of the X-ray tube 7 is provided, and the voltage sensor 9 is connected to the control means 208. The control means 208 controls the drive frequency fsw and on-time duty of the switching elements Q1 to Q4 so that the tube voltage Vx becomes the target voltage.

  In the present embodiment, the resonance circuit 101 includes a resonance inductor 203, a resonance capacitor 210, and resonance capacitors 205a and 205b. Resonance capacitors 205a and 205b can be regarded as one resonance capacitor 205 connected in parallel when converted to the primary side of the transformer. The inductance of the resonance inductor 203 is L201, the capacitance of the resonance capacitor 210 is C201, the combined capacitance of the resonance capacitor 205a and the resonance capacitor 205b is C205, as viewed from the primary side of the transformer 4, and the X-ray tube 7 and the rectifier circuit are combined. Assuming that the combined impedance is Z200, the impedance Z2 on the load side including the resonance circuit 101, the rectifier circuit 206, and the X-ray tube 7 as viewed from the output of the inverter 2 is expressed by equation (4).

Z2 = jωL201 + 1 / jωC210 + 1 / (Z200 + 1 / jωC205) Expression (4)
Here, by setting the capacitances C210 and C205 so that the impedance of the resonance capacitor 210 is sufficiently larger than the impedance of the resonance capacitor 205, the resonance circuit 101 of the X-ray high-voltage device of FIG. Since it can be regarded as a series circuit of the capacitor 210, the resonant inductor 203, and the resonant capacitor 205, the resonant frequency f2 is expressed by the equation (5).

f2 = √ (C210 × C205) / (2π√ ((C210 + C205) × L201)) (5)
As described above, in this embodiment, the influence of the load impedance Z0 can be reduced as compared with the first embodiment by connecting the resonance capacitor 210 in series with the resonance inductor 203 on the primary side of the transformer. Therefore, the resonant circuit 101 can be easily set as compared with the first embodiment.

  FIG. 5 shows operation waveforms of the X-ray high voltage apparatus of FIG. Hereinafter, the operation of the X-ray high voltage apparatus according to the second embodiment of the present invention will be described with reference to FIG. In the operation of FIG. 5, the inductance L203 of the resonance inductor 203 and the resonance capacitor 205 are set so that the frequency fr of the resonance current I1 supplied from the inverter is five times the drive frequency fsw of the inverter with reference to the equation (5). An example in which the capacitance C205 and the capacitance C210 of the resonance capacitor 210 are set is shown.

The control means 208 outputs the gate signals G1 to G4 so that the inverter 2 of FIG. 4 performs a basic operation as a full bridge inverter. Switching elements Q1 and Q4 Further, the upper and lower arms composed of switching elements Q1 and Q2 and the upper and lower arms composed of switching elements Q3 and Q4 are switched so that the switching elements Q2 and Q3 are simultaneously turned on or off. Let In FIG. 2, the on-time duties of the four switching elements Q1 to Q4 are each 50%.
(Mode 1) t0 to t1
First, an operation during a period (Mode 1) in which the switching elements Q1 and Q4 are on will be described. When the switching elements Q1 and Q4 are turned on, if the voltage of the DC power supply 1 is expressed as Vin, the output voltage V1 of the inverter is approximately + Vin. At this time, a resonance current flows through the path of the diode D4, the resonance capacitor 205, the resonance inductor 203, the resonance capacitor 210, and the diode D1, the energy of the resonance inductor 203 is released, and the energy is stored in the resonance capacitor C205 and the resonance capacitor 210. When all the energy of the resonant inductor 203 is released, the polarity of the resonant current I1 is reversed, and the resonant current is passed through the path of the DC power source 1, the switching element Q1, the resonant capacitor 210, the resonant inductor 203, the resonant capacitor 205, and the switching element Q4. The energy of the resonance capacitor 205 is discharged, and energy is stored in the resonance inductor 203 again. Here, since the resonant circuit 101 is set so that the frequency fr2 of the resonant current I1 is five times the drive frequency fsw of the inverter, the resonant circuit 203 and the resonant inductor 203 resonate during the ON period of the switching elements Q1 and Q4. Energy exchange with the capacitor 205 is repeated, and the polarity of the resonance current I1 is also inverted repeatedly. At this time, an AC voltage Vc21 having a phase delayed by π / 2 with respect to the resonance current I1 is generated at both ends of the resonance capacitor 205. As a result, an AC voltage having a frequency higher than the drive frequency fsw of the inverter can be applied to the rectifier circuit 206, and the currents Id1 and Id2 can be supplied to the smoothing capacitors Cm1 and Cm2.
(Mode 2) t1 to t2
When switching elements Q1 and Q4 are turned off at timing t1 and switching elements Q2 and Q3 are turned on, resonance current I1 flows through the path of diode D2, resonance inductor 203, resonance capacitor 205, and diode D3. To store energy in the resonant inductor 203. At this time, if the voltage of the DC power supply 1 is Vin, the output voltage V1 of the inverter is approximately −Vin. When all the energy of the resonant capacitor 205 is released, the DC power source 1, the switching element Q3, the resonant capacitor 205, the resonant inductor 203. The energy of the resonant inductor 203 is released through the path of the switching element Q2, and the energy is stored in the resonant capacitor 205. While the switching elements Q2 and Q3 are on, the polarity of the resonance current I1 is repeatedly inverted similarly to Mode1. At this time, an AC voltage Vc21 having a phase advanced by π / 2 with respect to the resonance current I1 is generated at both ends of the resonance capacitor 5. As a result, an AC voltage having a frequency higher than the drive frequency fsw of the inverter can be applied to the rectifier circuit 206, and the currents Id1 and Id2 can be supplied to the smoothing capacitors Cm1 and Cm2. Hereinafter, in a steady state, Mode 1 and Mode 2 are repeated.

  As described above, in the X-ray high voltage apparatus according to the present embodiment, the resonance frequency f2 is approximately (natural number + 1) times the drive frequency fsw of the inverter using the equations (5) and (6). By setting the inductance L201 of the resonance inductor 203, the combined capacitance C205 of the resonance capacitor 205a and the resonance capacitor 205b, and the capacitance C210 of the resonance capacitor 210 so as to be slightly lower, an inverter similar to the first embodiment The frequency of the resonance current I1 supplied from can be (natural number + 1) times. As a result, the pulsation ΔVx of the tube voltage Vx can be reduced without increasing the drive frequency fsw of the inverter, and therefore, rectification is performed while suppressing an increase in switching loss as compared with the method of increasing the drive frequency fsw of the inverter. The smoothing capacitor capacitances Cm1 and Cm2 of the circuit 206 can be reduced.

  In the present embodiment, a configuration in which the voltage doubler rectifier circuit is multi-staged is used for the rectifier circuit, and the turns ratio of the transformer can be reduced as compared with the first embodiment. Thereby, since the number of turns of the secondary winding can be reduced, a reduction in size of the transformer can be expected. Moreover, since the number of turns can be reduced, an effect of reducing the parasitic capacitance between the windings can be expected. In the present embodiment, the voltage doubler rectifier circuit is used, but a configuration using a Cockcroft-Walton circuit as shown in FIG. 6 may be used. In addition, although the number of stages of the voltage doubler rectifier circuit is two, it may be a multistage connection of three or more stages.

  Further, the inductance L203 of the resonance inductor 203, the capacitance C205 of the resonance capacitor 205, and the capacitance C210 of the resonance capacitor 210 are set to the same constant according to the load conditions (for example, heavy load condition and light load condition). The frequency of the resonance current I1 with respect to the inverter drive frequency fsw may be changed to an arbitrary multiple by changing the inverter drive frequency fsw.

  In the present embodiment, the inverter 2 has a full-bridge configuration, but a half-bridge configuration in which either one of the arm configured by the switching elements Q1 and Q2 or the arm configured by the switching elements Q3 and Q4 is replaced with a capacitor. Also good. Further, as shown in the circuit configuration diagram of FIG. 7, a configuration in which a Cockcroft-Walton circuit is connected in parallel to the secondary side of the transformer and one end of the output of the cockcroft-Walton circuit connected in parallel is connected to both ends of the X-ray tube 7. Also good. By using the Cockcroft-Walton circuit for the rectifier circuit, the pulsation of the tube voltage is increased as compared with the case of using the voltage doubler rectifier circuit, but the circuit configuration can be simplified.

(Connecting the series resonant capacitor 210 to the secondary side + paralleling the transformer and beyond)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 3 of the present invention. Similar to the X-ray high voltage apparatus of the first embodiment, this X-ray high voltage apparatus uses a DC power source 1 as a power source, an inverter 2, resonant inductors 303a and 303b, transformers 304a and 304b, and resonant capacitors 310a and 310b. And resonant capacitors 305a and 305b, rectifier circuits 306a and 306b, and control means 308, which supply a high DC voltage to the X-ray tube 7 as a load. The resonance circuit 103a includes a resonance inductor 303a, a transformer 304a, a resonance capacitor 310a, and resonance capacitors 305a and 305b. The resonance circuit 103b includes a resonance inductor 303b, a transformer 304b, a resonance capacitor 310b, and a resonance capacitor 305c. , 305d.

  The difference from the second embodiment is that the series resonance capacitors 310a and 310b of the resonance circuit 103a are connected in series with the secondary winding of the transformer, the transformer 304a, the resonance capacitor 310a, and the resonance inductor. The configuration includes a plurality of high voltage generators, each of which includes 303a, resonant capacitors 305a and 305b, and a rectifier circuit 306a. In this embodiment, the primary sides of the transformers 304a and 304b are connected in parallel, and the output portions of the rectifier circuits 306a and 306b are connected in series. Since the operation of the circuit configuration diagram of FIG. 8 is the same as that of the second embodiment, description thereof is omitted.

  As described above, in this embodiment, since the transformer is divided into a plurality of parts, the current supplied from the inverter to the transformer can be divided as compared with the second embodiment, and the heat generated in the transformer is dispersed. Can do. In addition, by connecting the series resonant capacitors 310a and 310b to the secondary side of the transformer, a capacitor having a smaller current capacity can be used as the series resonant capacitor than in the second embodiment. In this embodiment, the voltage doubler rectifier circuit is used for the rectifier circuits 306a and 306b. However, a cockcroft-Walton circuit may be used.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 9 and 10. FIG.

  FIG. 9 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 4 of the present invention. Similar to the X-ray high voltage apparatus of the second embodiment, this X-ray high voltage apparatus uses a DC power source 1 as a power source, and includes an inverter 402a, a resonant inductor 403a, a resonant capacitor 410a, a transformer 404a, a resonant capacitor 405a, A high DC voltage is supplied to the X-ray tube 7 serving as a load via a high voltage circuit 420 constituted by 405b and a rectifier circuit 406a. The difference from the second embodiment is that an inverter 402b, a resonant inductor 403b, a resonant capacitor 410b, a transformer 404b, a second high voltage circuit 421 composed of resonant capacitors 405c and 405d, and a rectifier circuit 406 are provided. , 421 are connected in parallel to the inverters 402a, 402b, and the outputs of the rectifier circuits 406a, 406b, which are the output parts of the high voltage circuits 420, 421, are connected in series. Further, current sensors 411 and 412 for detecting resonance currents I1 and I21 output from the inverter are connected to the high voltage circuits 420 and 421, respectively, on the transformer primary side. The resonance circuit 104a includes a resonance inductor 403a, a resonance capacitor 410a, a transformer 404a, and resonance capacitors 405a and 405b. The resonance circuit 104b includes a resonance inductor 403b, a resonance capacitor 410b, a transformer 404b, and a resonance capacitor 405c. , 405d. The voltage sensor 9 and the current sensors 411 and 412 are connected to the control unit 408. The control means 408 generates the gate signals G1 to G4 and G21 to G24 to the switching elements Q1 to Q4 and Q21 to Q24, and drives the inverters 402a and 402b with the drive frequency fsw, the on time duty, and the inverters 402a and 402b. The phase difference φ is controlled.

  Next, the operation of the X-ray high voltage apparatus shown in FIG. 9 will be described with reference to FIG. FIG. 10 shows operation waveforms of the circuit configuration diagram of FIG. In the operation of FIG. 10, the resonant inductors 403a and 403b and the resonant capacitors 410a and 410b are set so that the frequencies fr1 and fr2 of the resonant currents I1 and I21 supplied from the inverters 402a and 402b are three times the drive frequency fsw of the inverter. An example in which the resonance capacitor 405a is set to ˜405d is shown. Since the operation waveforms in FIG. 10 are the same as those in the second embodiment, only different points will be described. In this embodiment, the inverter 402a and the inverter 402b are operated so as to have a phase difference φ1. Thereby, the phase difference between the resonance current I1 and the resonance current I21 can be set to φ1, and the phase difference between the AC voltages Vc21 and Vc23 applied to the rectifier circuit 406a and the rectifier circuit 406b can be set to φ1. Since the AC voltage Vc21, Vc23 applied to the rectifier circuits 406a, 406b has a phase difference φ1, the voltage ripple of the smoothing capacitors Cm1, Cm2 and the voltage ripple of the smoothing capacitors Cm3, Cm4 can be canceled. The pulsation ΔVx of the voltage Vx can be reduced. A method for determining the phase difference φ1 will be described below.

  In general inverters, the frequency f1 of the resonance current is made to be the same as the drive frequency fsw of the inverter. Therefore, assuming that the switching cycle of the inverter is Tsw and the number of inverters is N, the ripple of the tube voltage Vx is almost minimum. The condition of the phase difference φ1 of the inverter becomes as shown in equation (6).

φ1 = Tsw / (2 × N) ··· Equation (6)
However, in the X-ray high voltage apparatus of the present invention, since the operation is performed so that the frequency f1 of the resonance current is (natural number + 1) times the drive frequency fsw of the inverter, the condition of the above equation (6) is not necessarily the ripple of the output voltage. This is not a condition that minimizes. In the present embodiment, the current sensors 420 and 421 detect the period T2 of the resonance currents I1 and I21, and the inverter phase difference φ1 is set so that the phase difference φ2 of the resonance currents I1 and I21 has the relationship of the equation (7). By controlling, the inverter can be controlled so that the pulsation ΔVx of the tube voltage Vx is minimized. Here, N in Equation (7) indicates the number of inverters.

φ1 = T2 / (2 × N) (7)
As described above, in this embodiment, a plurality of high voltage circuits are provided, the inputs of the high voltage circuit are connected in parallel, and the outputs of the high voltage circuit are connected in series, and the period T2 of the resonance currents I1 and I21 is detected and detected. By controlling the phase difference φ1 of the inverter based on the cycle T2, the pulsation ΔVx of the tube voltage Vx can be reduced as compared with the second embodiment. In the present embodiment, the period T2 of the resonance currents I1 and I2 is detected and the inverter is controlled. However, the present invention is not limited to this. Based on the tube voltage Vx detected by the voltage sensor 9, the inverter phase difference φ1 may be controlled so that the pulsation ΔVx of the tube voltage Vx is minimized.

  Next, a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a circuit configuration diagram of an X-ray high voltage apparatus according to Embodiment 5 of the present invention. Similar to the X-ray high-voltage apparatus of the first embodiment, this X-ray high-voltage apparatus includes a DC power source 1 as a power source, an inverter 2, a resonance circuit 105 including a transformer 4, and a rectifier circuit 6. A high DC voltage is supplied to an X-ray tube 7. The difference from the first embodiment is that a resonance circuit 105 is configured by connecting a resonance inductor 603 and a resonance capacitor 610 connected in series to a resonance inductor 503 and a resonance capacitor 510 connected in series. The resonance inductor 503, the resonance capacitor 510, and the resonance capacitor 5 constitute a resonance circuit 500, and the resonance inductor 603, the resonance capacitor 610, and the resonance capacitor 5 constitute a resonance circuit 600. In the present embodiment, the inductances of the resonant inductors 503 and 603, the resonant capacitors 510 and 610, and the resonant capacitor 5 so that the frequency of the resonant current I4 flowing through the resonant circuit 600 and the frequency of the resonant current I3 flowing through the resonant circuit 500 are different. Set the capacitance.

  FIG. 12 is a diagram showing operation waveforms of the X-ray high voltage apparatus of FIG. The operation of FIG. 11 will be described below with reference to FIG. In FIG. 12, the resonance circuit 500 is set so that the frequency of the resonance current I3 flowing through the resonance circuit 500 is three times the drive frequency fsw of the inverter, and the frequency of the resonance current I4 flowing through the resonance circuit 600 is An example in which the resonance circuit 600 is set to be three times the frequency of the resonance current I3 flowing through the circuit 500 is shown. Hereinafter, differences from the first embodiment will be described.

  The resonance current I1 supplied from the inverter 2 to the resonance circuit 105 is the sum of the resonance current I3 supplied to the resonance circuit 500 and the resonance current I4 supplied to the resonance circuit 600. In the operation of FIG. 12, the resonance current I4 is a current having a frequency three times higher than the resonance current I3, and thus the resonance current I1 has a square wave current waveform. By making the resonance current I1 into a square wave shape, the peak of the current flowing through the inverter can be suppressed.

  As described above, in this embodiment, the resonance capacitor 610 and the resonance inductor 603 connected in series are connected in parallel with the resonance capacitor 510 and the resonance inductor 503 connected in series, so that the inverter supplies the resonance circuit. The resonance current can be a square waveform. As a result, the peak value of the current can be suppressed as compared with the case where the resonance current has a sinusoidal waveform as in the first embodiment, so that the conduction loss of the X-ray high-voltage device can be reduced. . In the present embodiment, the resonance circuit is set so that the frequency of the resonance current I4 flowing through the resonance circuit 600 is three times the frequency of the resonance current I3 flowing through the resonance circuit 500. However, the present invention is not limited to this. Further, a configuration in which three or more series-connected bodies of resonant capacitors and resonant inductors are connected in parallel may be adopted. By increasing the number of parallel connections, the resonance current supplied from the inverter can be made a current waveform closer to a square wave.

  Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a waveform diagram showing the operation of the present embodiment. Since the circuit configuration of this embodiment is the same as that of the first embodiment, a description thereof will be omitted. Hereinafter, differences from the first embodiment will be described.

  In the present embodiment, the switching element Q3 of one switching leg of the inverter 2 having a full bridge configuration is always off, the switching element Q4 is always on, and the switching element Q1 and switching element Q2 of the other switching leg are alternately switched. The inverter 2 is caused to perform a half-bridge operation by performing a switching operation. In this method, if the voltage of the DC power supply 1 is the same, the output voltage Vinv of the inverter 2 can be halved compared to the case where the DC power supply 1 is operated as the full bridge inverter shown in FIG. Thereby, excellent power control can be realized over a wide range of load conditions.

  As described above, according to the present embodiment, it is possible to realize excellent power controllability at light loads by causing a half-bridge operation of an inverter circuit having a full bridge configuration.

  In this embodiment, the switching legs composed of the switching elements Q1 and Q2 are switched. However, the switching element Q1 is always turned off, the switching element Q2 is always turned off, and the switching elements Q3 and Q4 are alternately switched. Even if it is operated, the same effect can be obtained.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these. For example, in the fourth embodiment, the X-ray high voltage apparatus including two high voltage circuits has been described. However, the present invention can be applied to an X-ray high voltage apparatus including three or more high voltage circuits. It is possible to do. In all the embodiments, the present invention can be applied even when the DC power supply is used as the output of the AC-DC converter or the DC-DC converter.

  The X-ray high voltage apparatus of the present invention can be applied to a power supply apparatus that supplies a high voltage to an X-ray tube used in an X-ray CT apparatus, an X-ray imaging apparatus or the like.

1 ... DC power source 2,202, 402a, 402b ... Inverters 3, 203, 303a, 303b, 403a, 403b, 503, 603 ... Resonant inductors 4, 204, 304a, 304b, 404a, 404b,. Transformer 5, 205, 205a, 205b, 305a, 305b, 305c, 305d, 405a, 405b, 405c, 405d, 210, 310a, 310b, 310c, 310d, 410a, 410b, 510, 610 ... resonance capacitor 420, 421: High voltage circuit 6, 206, 206a, 206b, 306a, 306b, 406a, 406b ... Rectifier circuit 7 ... X-ray tube 8, 208, 308, 408 ... Control circuit 9 ... Voltage sensors 411, 412 ... current sensors 100, 101, 102, 03a, 103b, 104a, 104b, 105, 500, 600... Resonant circuit Q1, Q2, Q3, Q4, Q21, Q22, Q23, Q24... Switching elements D1, D2, D3, D4, D21, D22, D23, D24 ... Diodes Dr1, Dr2, Dr3, Dr4, Dr11, Dr12, Dr13, Dr14, Dr15, Dr16, Dr17, Dr18, Dr21, Dr22, Dr23, Dr24, Dr25, Dr27, Dr28 ... Rectifier diode Cd1 , Cd2, Cd3, Cd4, C21, Cd22, Cd23, Cd24 ... Rectifier capacitors Cm, Cm1, Cm2, Cm3, Cm4 ... Smoothing capacitors C200, C201 ... Capacitors T1, T2, T31, T32, T41, T42 ... Cores N1, N11, 12 ... Primary windings N2, N21, N22, N23, N24 ... Secondary windings N1, N11, N12, N13 ... Primary windings N2, N21, N22, N23, N24 ... Secondary Winding

Claims (15)

With a transformer,
An inverter that is electrically connected in parallel between the DC power source and the transformer and converts a DC voltage into an AC voltage;
A rectifier circuit connected in parallel between the transformer and the X-ray tube and smoothing the AC voltage to supply a DC voltage to the X-ray tube;
A control unit for controlling the inverter;
An X-ray high voltage apparatus comprising: a resonance circuit that is electrically provided between the inverter and the rectifier circuit and includes the transformer;
The frequency of the AC voltage applied to the rectifier circuit is set by setting the resonant circuit so that the frequency of the resonant current supplied from the inverter to the resonant circuit is (natural number + 1) times the frequency of driving the inverter. The X-ray high voltage apparatus is characterized in that is set to (natural number + 1) times the frequency for driving the inverter. The X-ray high voltage apparatus according to claim 1,
The resonant circuit is:
A resonant inductor connected in series with the primary or secondary winding of the transformer;
A resonant capacitor connected in parallel between the primary winding or secondary winding of the transformer between the resonant inductor and the rectifier circuit;
An X-ray high voltage apparatus comprising: An X-ray high voltage apparatus according to claim 2,
The resonant circuit is:
An X-ray high voltage apparatus comprising a second resonant capacitor connected in series with the resonant inductor. An X-ray high voltage apparatus according to any one of claims 1 to 3,
A plurality of high-voltage circuit units including the inverter, the resonance circuit, the transformer, and the rectifier circuit;
The plurality of high voltage circuit units are configured such that input terminals of the inverter as an input unit are connected in series or in parallel, and output terminals of the rectifier circuit as an output unit are connected in series or in parallel. X-ray high voltage device. An X-ray high voltage apparatus according to claim 4,
The X-ray high voltage apparatus, wherein the control unit controls the resonance current supplied from the inverter to the resonance circuit to have a phase difference between the plurality of high voltage circuit units. The X-ray high voltage apparatus according to claim 5,
A current detection unit for detecting a resonance current supplied from the inverter to the resonance circuit;
When the number of the high voltage circuit units is defined as N, the control unit determines that the phase difference of the resonance current is π / (2 × N) based on the period of the resonance current detected by the current detection unit. The X-ray high voltage apparatus is characterized by controlling the inverter. The X-ray high voltage apparatus according to claim 3,
The resonant circuit is configured by connecting a series resonant circuit composed of the resonant inductor and the second resonant capacitor in parallel with both ends of the series resonant circuit, and connecting a second resonant inductor and a third resonant capacitor in series. And a second series resonant circuit. The X-ray high voltage device according to claim 7,
X-rays for setting the second resonant inductor and the third resonant capacitor so that the frequency of the resonant current flowing in the second resonant inductor is (natural number + 1) times the frequency of the resonant current flowing in the resonant inductor. High voltage device. The X-ray high voltage apparatus according to any one of claims 1 to 8,
2. The X-ray high voltage apparatus according to claim 1, wherein the inverter is a full bridge circuit including two sets of upper and lower arms that are series bodies of two switching elements. The X-ray high voltage apparatus according to claim 9, wherein the inverter causes one of the two sets of upper and lower arms to perform switching operation, and in the other upper and lower arms, one switching element is always turned on, An X-ray high voltage apparatus, wherein the two sets of upper and lower arms are operated so that the other switching element is always turned off. The X-ray high voltage apparatus according to any one of claims 1 to 8,
2. The X-ray high voltage apparatus according to claim 1, wherein the inverter is a half-bridge circuit including a pair of upper and lower arms that are series bodies of two switching elements. The X-ray high voltage apparatus according to any one of claims 1 to 11,
2. The X-ray high voltage apparatus according to claim 1, wherein the rectifier circuit is configured by connecting n voltage doubler rectifier circuits, which are natural numbers, in series or in parallel in multiple stages. The X-ray high voltage apparatus according to any one of claims 1 to 11,
2. The X-ray high-voltage apparatus according to claim 1, wherein the rectifier circuit is configured by connecting n natural number of Cockcroft-Walton circuits in series or in parallel. The X-ray high voltage apparatus according to any one of claims 1 to 13,
An X-ray high voltage apparatus, wherein a voltage supplied to the X-ray tube is controlled by changing a frequency for driving the inverter.   An X-ray diagnostic imaging apparatus comprising the X-ray high voltage apparatus according to claim 1.