JP4417537B2 - X-ray power supply power converter - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a power converter that uses a three-phase AC power supply as an input, and more particularly to a power converter that is convenient when an existing three-phase 200V AC power supply must be used when updating equipment such as an X-ray power supply.
[0002]
[Prior art]
An X-ray power source that uses a commercial AC power source as an input is an AC-DC-HFAC that converts a DC voltage obtained by primary rectification of the AC power source voltage into high frequency alternating current (HFAC) by an inverter circuit and performs secondary rectification through a transformer. -DC converter. In particular, in a large-capacity X-ray power supply, a three-phase 400 V system (400 to 440 V) alternating current is used to reduce loss due to a reduction in circuit current. When the three-phase 400V AC voltage is full-wave rectified, it is converted to a DC voltage of about 600V. The voltage is about twice that of the three-phase 200V AC voltage, but the current is only about ½. Therefore, in the case of a three-phase 400V system, a relatively inexpensive and small-sized 1200V withstand voltage IGBT that is widely available on the market can be used as a switching element. However, the three-phase 400V system is special, and the usual hospital equipment is generally a three-phase 200V AC power supply (200 to 220V).
[0003]
[Problems to be solved by the invention]
When a three-phase 200V system AC voltage is rectified, a DC voltage of about 300V is obtained, and a switching element such as an IGBT having a withstand voltage of 600V can be used. Therefore, a switching element having a withstand voltage of 600V and a current capacity that is twice that of the three-phase 400V system must be increased in size and cost as compared with a switching element with a withstand voltage of 1200V. Also, a three-phase 200V three-phase voltage doubler rectifier circuit has been devised, but it has a problem that a large number of large-capacity capacitors and rectifier diodes are required and the circuit becomes complicated.
[0004]
In order to solve such a problem, the present invention is a converter corresponding to a three-phase 200V AC input power supply, but the circuit current is as small as that in the three-phase 400V system and the withstand voltage is three-phase 200V. Provided is a power converter that combines a single-phase circuit configuration using a switching element having a withstand voltage twice that of a power supply voltage.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes a three-phase AC input terminal that receives a three-phase 200V AC voltage or a three-phase 400V AC voltage, and two adjacent two of the three-phase AC input terminals. Connected in parallel to two diodes connected in series and two capacitors connected in series, which are connected to the input terminal by an input connector and can double voltage rectify the interphase voltage of the three-phase AC voltage, respectively. The rectifier having the first to third voltage doubler configurations, the first opening / closing means inserted in each of the input connectors, and the positive polarity of the rectifier having the first to third voltage doubler configurations. Positive polarity common connection body for connecting outputs in common, each second switching means interposed in each of the positive polarity common connection bodies, and negative polarity of the rectifier having the first to third voltage doubler configurations A negative common connection for connecting outputs in common, and Each third switching means inserted in each negative common connection body, each inverter circuit for converting the DC output voltage of each of the first to third voltage doubler rectifiers into an AC voltage, A control circuit that controls the inverter circuit, each transformer that boosts the AC voltage of each of the inverter circuits, and each secondary-side rectifier that rectifies the secondary winding voltage of each of the transformers. When the output terminal of the secondary side rectifier is connected in parallel and the three-phase 200V AC voltage is received by the three-phase AC input terminal, the first opening / closing means is closed and the second and third opening / closing means are opened. Accordingly, the rectifier having the first to third voltage doubler configurations is operated as a voltage doubler rectifier that doubles the interphase voltage of the three-phase AC voltage, and a three-phase 400V AC voltage is obtained. When receiving power to the three-phase AC input terminal, the first opening / closing means is opened and the second and third opening / closing means are closed, so that the rectifiers having the first to third voltage doubler configurations can be provided. Provided is a power converter for an X-ray power supply device characterized in that it operates as a rectifier for full-wave rectification of a phase AC voltage, so as to correspond to both a three-phase 200V system and a three-phase 400V system AC input voltage .
[0006]
The invention of claim 2 is characterized in that, in order to solve the above-mentioned problem, the output ripple voltage is reduced by controlling the output voltage of the inverter circuit to have a predetermined phase difference. An X-ray power supply power converter is provided.
[0007]
In order to solve the above-mentioned problem, the invention of claim 3 is characterized in that, in claim 1 or claim 2, the inverter circuit is a half-bridge circuit comprising a pair of switching elements and a pair of capacitors. A power converter for a power supply is provided.
[0008]
According to a fourth aspect of the present invention , there is provided an X-ray power supply apparatus according to any one of the first to third aspects, wherein the inverter circuit is a resonance type inverter that performs a resonance operation. Provide a power converter.
[0009]
According to a fifth aspect of the present invention, in order to solve the above problem, in any one of the first to fourth aspects, the secondary side rectifier is a voltage doubler rectifier that doubles the secondary winding voltage of the transformer, or Provided is a power converter of an X-ray power supply device characterized by being a multiple voltage rectifier such as a Cockcroft-Walton circuit that rectifies the secondary winding voltage by multiple voltage .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First, an embodiment of the present invention will be described. In the first embodiment of the present invention, the interphase voltage of a three-phase 200V AC voltage is rectified by three voltage doubler rectifiers having a single phase configuration, and each of the DC voltages is doubled. Get voltage. Next, each DC voltage is converted into a high-frequency AC voltage by three single-phase high-frequency inverter circuits, and a high-frequency AC voltage boosted from the secondary winding of each transformer is obtained. These high-frequency AC voltages are rectified by a secondary-side rectifier having a single-phase configuration and synthesized to obtain a DC high-voltage output.
[0016]
In this way, by using a power converter that combines a three-phase 200V power supply and a single-phase converter, the circuit current can be reduced to the same small value as the three-phase 400V power supply with a simple structure, and the commercially available 1200V withstand voltage can be reduced. A switching element such as an IGBT can be used to reduce the size and cost.
[0017]
Next, the second embodiment uses a rectifier configured to double voltage rectify the interphase voltage so that both the three-phase 200V AC voltage and the three-phase 400V AC voltage can be used. When receiving power at the input terminal, the switching means is operated to switch the connection so that the rectifier operates as a voltage doubler rectifier. Next, when receiving power at the three-phase 400V AC voltage input terminal, The connection is switched so that the rectifier operates and operates as a normal rectifier.
[0018]
Further, as another embodiment, the output ripple can be reduced by using three inverter circuits and shifting the phase thereof. Further, the circuit configuration is further simplified by adopting a half-bridge configuration for each of the three inverter circuits. Furthermore, by switching the AC input circuit, both the three-phase 200V system and the three-phase 400V system can be supported. Further, by making each of the three inverter circuits resonant, the peak value of the voltage between the primary windings of the transformer 13 can be increased, and the turn ratio of the primary winding and the secondary winding can be increased. A small transformer 13 can be used.
[0019]
In yet another embodiment, the interphase voltage of the three-phase 400V AC voltage is rectified by a three-phase full-wave rectifier circuit having a normal circuit configuration to obtain a DC voltage. Next, each DC voltage is converted into a high-frequency AC voltage by a plurality of parallel-connected single-phase high-frequency inverter circuits, and the high-frequency AC voltage boosted from the secondary winding of each transformer connected to these outputs obtain. These high-frequency AC voltages are rectified by a secondary-side rectifier having a single-phase configuration and synthesized to obtain a DC high-voltage output.
[0020]
【Example】
Embodiment 1 A CT X-ray tube high voltage power supply apparatus to which the present invention is applied will be described as a first embodiment with reference to FIG. In general, X-ray CT is installed in a hospital, and in Japan, three-phase 200V is often distributed in the hospital because of power supply facilities. The CT high voltage power supply device is required to have a low ripple output voltage in order to improve the quantity and quality of X-rays.
[0021]
In FIG. 1, 1R, 1S, and 1T are three-phase AC input terminals connected to each phase of a three-phase 200V AC power source. In the following description, since the circuit configuration of each phase is the same, R, S, and T added after the member code indicate the corresponding members of each phase, and the description will be omitted in some cases. The three-phase AC input terminals 1R and 1S are connected to the first primary voltage doubler rectifier circuit 2R. Similarly, the three-phase AC input terminals 1S and 1T are connected to the second primary side voltage doubler rectifier circuit 2S, and the three-phase AC input terminals 1T and 1R are connected to the third primary side voltage doubler rectifier circuit 2T. The Each primary side voltage doubler rectifier circuit has a well-known circuit configuration, and the primary side voltage doubler rectifier circuit 2R includes two arms 3 and 4 connected in series and two voltage doublers connected in series. An arm composed of capacitors 5 and 6 is connected in parallel, and a three-phase AC input terminal 1S is connected to the midpoint thereof. The same applies to the other primary side voltage doubler rectifier circuits 2S and 2T.
[0022]
Next, the configuration after the voltage doubler rectifier circuit 2R will be described. The DC input terminal of the half-bridge inverter circuit 7R is connected to the DC output of the voltage doubler rectifier circuit 2R. The inverter circuit 7R includes two IGBTs 8 and 9 and voltage dividing capacitors 10 and 11 as switching elements. The high frequency output of the inverter circuit 7 is connected to the primary winding 14 of the high voltage transformer 13R through the corresponding resonance inductance 12R. The secondary winding 15 is connected in parallel with a high-voltage transformer 13R distributed capacitor or a resonant high-voltage capacitor 16 which is an electrical component. The secondary winding 15 is connected to secondary-side voltage doubler rectifier circuits 17R and 18R having two positive and negative circuits. The positive voltage doubler rectifier circuit 17R is a well-known circuit comprising a voltage multiplier capacitor 19 in series with the secondary winding 15, diodes 20 and 21 connected in series with each other, and a filter capacitor 22. A DC voltage twice as large as the positive polarity is generated in the filter capacitor 22 by the rectifying action. The negative voltage doubler rectifier circuit 18R is a well-known circuit comprising a voltage multiplier capacitor 23 in series with the secondary winding 15, diodes 24 and 25 connected in series with each other, and a filter capacitor 26. The filter capacitor 26 generates a DC voltage twice that of the negative polarity. The configurations of the S phase and the T phase are the same, and the description thereof is omitted, but the filter capacitors 22 and 26 are shared with the R phase. A positive double voltage and a negative double voltage are applied to the anode and cathode of the X-ray tube 27, respectively. The common sides of the positive voltage doubler rectifier circuit 17R and the negative voltage doubler rectifier circuit 18R are commonly connected and grounded.
[0023]
Reference numeral 28 denotes an X-ray tube voltage detection resistor. In this embodiment, only the voltage on the positive polarity side is detected because the secondary winding 15 of one transformer 13R drives a voltage doubler circuit having both positive and negative polarities. This is because the symmetry of is good. Of course, both positive and negative voltages may be detected. 29 is a so-called pulse width control (PWM) circuit that controls the on-time ratio of the IGBTs of the inverter circuits 7R to 7T so that the X-ray tube voltage is stabilized by the detection voltage. The PWM control circuit 29 sends three sets of drive signals to the three inverter circuits 7R to 7T. A drive signal XR and a drive signal XR ′ having a phase opposite thereto are respectively sent to the IGBTs 8 and 9 of the inverter circuit 7R. Similarly, a drive signal XS and a drive signal XS ′ having a phase opposite to that of the drive signal XS and a drive signal XT and a drive signal XT ′ having a phase opposite to that of the drive signal XS are transmitted to 7S and 7T, respectively. Further, in this embodiment, the drive signal XR, the drive signal XS, and the drive signal XT, and the drive signal XR ′, the drive signal XS ′, and the drive signal XT ′ have an appropriate phase difference, for example, a phase difference of 120 degrees.
[0024]
Next, the operation of the circuit configuration as described above will be described. When the three-phase 200V system AC voltage is received by the three-phase input terminals 1R, 1S, and 1T, the AC voltage of each phase is double-voltage rectified by each primary-side voltage doubler rectifier circuit 2 to obtain a DC voltage of about 480V. Become. DC 480V of each phase is supplied to inverter circuits 7R to 7T. Since this voltage is 600 V at maximum due to fluctuations in the AC input power supply voltage, the IGBTs 8 and 9 of the inverter circuits 7R to 7T need to have a withstand voltage of 1200 V class. In the R phase, the inverter circuit 7R converts this DC voltage into a high-frequency AC voltage of 100 kHz, and a voltage necessary for the resonance action of the resonance inductance 12R, the resonance capacitor 16 , and the boosting action of the transformer 13R, for example, secondary The voltage is boosted to 35 kV by the winding 15, and the voltages of the positive output 70 kV and the negative output 70 kV are output from the next voltage doubler rectifier circuits 17 R and 18 R, respectively, and a DC voltage of, for example, 140 kV is supplied to the X-ray tube 27. The same applies to the S phase and the T phase, and the three voltage doubler rectified outputs are synthesized by the filter capacitors 22 and 26. Note that the series resonance type inverter circuit is an example, and may be an inverter circuit having another configuration, and details thereof are not directly related to the present invention, and thus will be omitted.
[0025]
In this embodiment, since the inverter circuits 7R to 7T operate with a DC input voltage of about 480V, the withstand voltage is required to be almost twice as high as that in the case of the 200V AC input power supply. Therefore, not only a small and low-cost IGBT can be used, but also wiring loss and transformer winding loss are reduced, and high efficiency is achieved.
[0026]
Further, the PWM control circuit 29 supplies a drive signal XR, a drive signal XS, and a drive signal XT having a phase difference of 120 degrees to each IGBT 8 of the inverter circuits 7R to 7T, and each IGBT 9 of the inverter circuits 7R to 7T. Is supplied with the opposite phase driving signal XR ′ and driving signal XS ′ driving signal XT ′ having a phase difference of 120 degrees, the ripple frequency is 300 kHz, which is three times the conversion frequency 100 kHz, and the filter capacitor capacity is If they are the same, the ripple can be reduced to 1/3 or less than when there is no phase difference, and a flat output voltage with a smaller ripple can be obtained.
[0027]
Second Embodiment Next, an embodiment of a high power X-ray tube power converter that can be used by switching both voltages of a three-phase 200V system input and a three-phase 400V system input will be described with reference to FIG. The same reference numerals as those in FIG. All the components are well known, and detailed description thereof is omitted. Since each phase has the same configuration, the R phase will be described. The inverter circuit 31R is a bridge inverter circuit composed of four switching elements such as IGBTs. The transformer 32R has two secondary windings 33 and 34, and is connected to the double wave rectifier circuits 35R and 36R of both wave type for positive polarity and negative polarity, respectively. The voltage doubler rectifier circuits 35R and 36R include two diodes 37 and 38 and two filter capacitors 41 and 42, and the voltage doubler rectifier circuit 36R includes two diodes 39 and 40 and two filter capacitors 43 and 44. It consists of. Although the other phases are the same, the filter capacitors 41, 42, 43, and 44 are used in common for each phase. Although the control circuit is omitted, the IGBTs forming a pair of the inverter circuits 31R to 31T are controlled with a phase difference of 120 degrees, and this is the same as the embodiment of FIG.
[0028]
Next, a method for switching the input voltage will be described. The voltage switching of the input circuit is performed by connecting lines 51, 52 and 53 indicated by chain lines, positive common connection lines 54 and 55 indicated by alternate long and short dashed lines, and negative common connection lines 56 and 57 indicated by alternate long and short dashed lines, Although not shown, it is performed by an opening / closing means such as a switch inserted in each of the connection lines 51-57. When receiving an input voltage of a three-phase 200V system, the positive common connection lines 54 and 55 and the negative common connection lines 56 and 57 are disconnected by opening and closing means (not shown), and the connection indicated by the solid line In addition, the connection line 51 is connected to the input terminal 1S, the connection line 52 is connected to the input terminal 1T, and the connection line 53 is connected to the input terminal 1R with the respective opening / closing means (not shown) closed. As a result of this connection, a voltage doubler rectifier circuit is configured for each phase as in FIG. 1, and a rectified voltage 480 V is output, and the circuit after the inverter circuit 31 operates in the same manner as described in FIG.
[0029]
When receiving three-phase 400V input power to the input terminals 1R, 1S, and 1T, open the respective opening / closing means (not shown), disconnect the connection lines 51, 52, and 53, and close the respective opening / closing means (not shown). The positive common connection lines 54 and 55 and the negative common connection lines 56 and 57 are connected. Thus, the rectifier circuit 2 has a three-phase full-wave rectifier circuit configuration and outputs a rectified voltage 480V. As described above, the rectified voltage is substantially the same regardless of which of the three-phase 200V system or 400V system input voltage is received by the input terminals 1R, 1S, and 1T. Therefore, the inverter circuit 31 operates and outputs in any case. There is no difference in power.
[0030]
Although the embodiments have been described with reference to the inverter circuit, the secondary rectifier circuit, and the like, various types of inverters such as a series resonance type, a parallel resonance type, and a double forward type can be used for the inverter circuit. As the secondary rectifier circuit, a rectifier circuit such as Cockcroft-Walton suitable for each type of inverter circuit can be used.
[0031]
In the second embodiment shown in FIG. 2, a case has been described in which the same output power can be supplied to the load regardless of which of the three-phase 200V system or 400V system input voltage is received. If the primary rectifier 2 is not required to have a voltage doubler rectification configuration, it is a normal three-phase full-wave rectifier circuit, and the output is for a filter. A capacitor may be connected, and two or more inverter circuits may be connected in parallel to both ends of the filter capacitor so that the same phase difference is controlled. In the above embodiments, the IGBT is used as the switching element of the inverter circuit. However, other switching power semiconductor elements such as MOSFET, IEGT, or thyristor can be used. Of course, this power converter can be used in addition to the X-ray tube power source.
[0032]
【The invention's effect】
As described above, according to the present invention, even when a three-phase 200V system AC input voltage is supplied, the rectified DC voltage is raised to the same level as the three-phase 400V system rectified voltage, so that it becomes the input voltage of the inverter circuit. Compared to the case where the three-phase 200V system voltage is rectified as it is, a switching element such as a commercially available 1200V system withstand voltage IGBT having a current capacity of about ½ can be used. A small and inexpensive one can be used. Further, the transformer primary winding current is also ½ that of the 200 V system, and the efficiency is improved. In particular, there is an advantage that the ripple voltage can be lowered by shifting the phase of each of the three-phase inverter circuits. Furthermore, in the present invention, the primary-side rectifier circuit, the inverter circuit and the secondary-side rectifier circuit having a single-phase circuit configuration are combined with each of the three phases and finally synthesized, so that the three-phase 200V system or the three-phase 400V For any input voltage of the system, it is possible to standardize a power converter having a relatively large output power with an electronic component having a relatively small current capacity, and it is possible to reduce the cost.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a power converter that inputs a three-phase 200V AC voltage of the present invention.
FIG. 2 shows another embodiment of a power converter configured to be compatible with both a three-phase 200V system and a three-phase 400V system AC voltage.
[Explanation of symbols]
1 .. Three-phase AC input terminal 2. Primary voltage rectifier 7 with voltage doubler configuration. Inverter circuit 12. Resonance inductor 13. Transformer 16. Resonance capacitor 17. Secondary voltage doubler rectifier 18. · · Secondary side voltage rectifier 29 · · Control circuit 31 · · Inverter circuit 32 · · Transformer 35 · · Secondary side voltage rectifier 36 · · Secondary voltage rectifier

Claims (5)

A three-phase AC input terminal for receiving a three-phase 200V AC voltage or a three-phase 400V AC voltage;
It is connected in series with two diodes connected in series, which are connected to two adjacent input terminals of the three-phase AC input terminal by an input connector and can double-voltage rectify the interphase voltage of the three-phase AC voltage. A rectifier having first to third voltage doubler configurations configured by connecting two capacitors in parallel ;
Each first opening / closing means inserted in each of the input connectors;
A positive common connection for commonly connecting the positive outputs of the rectifiers of the first to third voltage doubler configurations;
Each second opening / closing means inserted in each of the positive polarity common connectors;
A negative common connection for commonly connecting the negative outputs of the rectifiers of the first to third voltage doubler configurations;
Each third opening / closing means inserted in each of the negative polarity common connection body,
Each inverter circuit for converting the DC output voltage of each of the rectifiers of the first to third voltage doubler configurations into an AC voltage;
A control circuit for controlling the inverter circuit;
Each transformer for boosting the AC voltage of each inverter circuit;
Each secondary side rectifier rectifying the secondary winding voltage of each of the transformers, and connecting the output terminals of the secondary side rectifier in parallel,
When receiving a three-phase 200V AC voltage to the three-phase AC input terminal, the first switching means is closed, and the second and third switching means are opened, thereby the first to third times. Operating the voltage configuration rectifier as a voltage doubler rectifier for voltage rectifying the interphase voltage of the three-phase AC voltage,
When receiving a three-phase 400V AC voltage to the three-phase AC input terminal, the first switching means is opened and the second and third opening / closing means are closed, thereby the first to third times. By operating a rectifier having a voltage configuration as a rectifier for full-wave rectification of the three-phase AC voltage, the power of the X-ray power supply apparatus is made compatible with both three-phase 200V system and three-phase 400V system AC input voltages. converter. In claim 1 ,
A power converter for an X-ray power supply device , wherein the output ripple voltage is reduced by controlling the output voltage of the inverter circuit to have a predetermined phase difference. In claim 1 or claim 2 ,
A power converter for an X-ray power supply device, wherein the inverter circuit is a half-bridge circuit including a pair of switching elements and a pair of capacitors. In any one of Claims 1 thru | or 3 ,
The power converter of an X-ray power supply device, wherein the inverter circuit is a resonance type inverter that performs a resonance operation. In any one of Claim 1 thru | or 4 ,
The secondary side rectifier is a voltage doubler rectifier that doubles the secondary winding voltage of the transformer, or a multiple voltage rectifier such as a Cockcroft-Walton circuit that multiple voltage rectifies the secondary winding voltage. A power converter for an X-ray power supply device .

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