Current source power conversion circuit

An example of the current source power conversion circuit is provided with a plurality of half-bridge rectifier circuits which are connected in parallel, each including a serial connection of a first switch circuit having a first self-turn-off element and a first diode which are connected in series to each other, and a second switch circuit having a second self-turn-off element and a second diode which are connected in series to each other. A first current electrode of said first self-turn-off element in one of said half-bridge rectifier circuits and a first current electrode of said first self-turn-off element in other one of said half-bridge rectifier circuits are short-circuited and connected.

TECHNICAL FIELD

The present invention is an invention relating to a current source power conversion circuit.

BACKGROUND ART

Generally, in a current source power conversion circuit, an element with a structure to block reverse conduction needs to be used for a switch circuit. For example, the switch circuit is considered to have a configuration where an IGBT (Insulated Gate Bipolar Transistor) and a diode are connected in series. Such a configuration is disclosed in Japanese Patent Application Laid-Open No. 2003-164140, for example. Further, as a current source power conversion circuit having adopted such a switch circuit made up of an IGBT and a diode, there is known one formed by multiphase combination of circuits ensuring reverse voltage resistance of the IGBT.

Moreover, the current source power conversion circuit is also used as a rectifier circuit of a current source PWM (Pulse Width Modulation). Specifically, this is disclosed in Japanese Patent Application Laid-Open No. 2007-295686.

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In a conventional current source power conversion circuit, a potential (e.g. an emitter potential in the case of an IGBT with a current source power conversion circuit used as a rectifier circuit) applied to a switch circuit is different in each phase. Therefore, in the conventional current source power conversion circuit, it has been necessary to use an independent power supply for the switch circuit in each phase in order to drive the switch circuit in each phase. In provision of a drive power supply in each switch circuit, six drive power supplies are required in the case of a three-phase current source power conversion circuit, which has caused a problem of the current source power conversion circuit having an expensive and complicated configuration.

Accordingly, it is an object of the present invention to provide a current source power conversion circuit reducing the number of drive power supplies used and having an inexpensive and simple configuration.

Means for Solving the Problem

In order to solve the above problem, a current source power conversion circuit of the present invention is provided with a plurality of half-bridge rectifier circuits which are connected in parallel, each including a serial connection of a first switch circuit having a first self-turn-off element and a first diode which are connected in series to each other and a second switch circuit having a second self-turn-off element and a second diode which are connected in series to each other. Forward directions of the first self-turn-off element, the first diode, the second self-turn-off element, and the second diode are made uniform in the same direction in any of the half-bridge rectifier circuits, each first self-turn-off element has a first current electrode, a second current electrode, and a control electrode, and is turned on and off based upon a control signal given to the control electrode, a reference of the control signal is a potential of said first current electrode, the second current electrode of the first self-turn-off element is connected to the first diode in any of the half-bridge rectifier circuits, and a first current electrode of the first self-turn-off element in one of the half-bridge rectifier circuits and a first current electrode of the first self-turn-off element in other one of the half-bridge rectifier circuits are short-circuited and connected.

There are further provided a first drive circuit that gives the control signal to the first self-turn-off element, a capacitor charged by a power supply that drives the first drive circuit, and a second drive circuit that is driven by an electric charge having charged the capacitor and controls the second switch circuit, and a discharge blocking diode for blocking discharge of the capacitor to the power supply may exist between the power supply and the capacitor.

Further, a circuit that stores an electric charge in the capacitor may be a bootstrap circuit.

Further, a circuit that stores an electric charge in the capacitor may be a charge pump circuit.

Further, the first diode may be made to function as the discharge blocking diode.

Further, the second diode may be made to function as the discharge blocking diode.

Further, the second diode may be arranged farther away from the first switch circuit than the second self-turn-off element.

Further, at least one switch circuit out of the first switch circuit and the second switch circuit in the plurality of half-bridge rectifier circuits may be a self-turn-off element having reverse voltage resistant characteristics.

Further, the self-turn-off element having reverse voltage resistant characteristics may be made to function as the discharge blocking diode.

Effects of the Invention

According to this current source power conversion circuit, the first current electrodes of the first self-turn-off elements in the respective phases are made a common potential, whereby it is possible to reduce the number of drive power supplies used and form an inexpensive and simple configuration.

Further, the second switch circuit is controlled based upon the capacitor in which an electric charge is stored by a power supply, whereby it is possible to further reduce the number of drive power supplies used and form an inexpensive and simple configuration.

Further, the circuit that stores an electric charge in the capacitor is the bootstrap circuit, whereby it is possible to reduce the number of drive power supplies used and form an inexpensive and simple configuration.

Further, the circuit that stores an electric charge in the capacitor is the charge pump circuit, whereby it is possible to reduce the number of drive power supplies and form an inexpensive and simple configuration.

Further, the discharge blocking diode is substituted by the first diode or the second diode in the first switch circuit, whereby it is possible to further simplify a circuit configuration.

Further, the second diode is arranged farther away from the first switch circuit than the second self-turn-off element, whereby it is possible to eliminate a voltage drop of the second diode at the time of charging the capacitor and ensure a further high charged voltage of the capacitor, so as to improve the reliability of operation of the second switch circuit.

Further, at least one switch circuit out of the first switch circuit and the second switch circuit in the plurality of half-bridge rectifier circuits is the self-turn-off element having reverse voltage resistant characteristics, whereby it is possible to reduce the number of elements constituting the switch circuit, so as to simplify the circuit configuration. Moreover, a loss that occurs in the switch circuit decreases, whereby it is possible to make a heat sink for heat dissipation smaller, so as to further save space.

Further, the discharge blocking diode is substituted by the self-turn-off element having reverse voltage resistant characteristics, whereby it is possible to further simplify a circuit configuration.

Objectives, features, aspects, and advantages of the present invention are made more obvious by means of the following specific descriptions and accompanying drawings.

EMBODIMENT FOR CARRYING OUT THE INVENTION

FIG. 1shows part of a circuit diagram of a current source power conversion circuit according to the present embodiment. Further,FIG. 2shows a circuit diagram of a conventional current source power conversion circuit.

First, the circuit shown inFIG. 2is a three-phase current source rectifier circuit.FIG. 2shows a three-phase current source rectifier circuit101, a three-phase alternating-current power supply120, and an LC filter circuit130. The three-phase current source rectifier circuit shown inFIG. 2includes three half-bridge rectifier circuits connected in parallel to one another. Specifically, the half-bridge rectifier circuit corresponding to an r-phase has IGBTs103r,105rand diodes104r,106r. Further, the half-bridge rectifier circuit corresponding to an s-phase has IGBTs103s,105sand diodes104s,106s. Moreover, the half-bridge rectifier circuit corresponding to a t-phase has IGBTs103t,105tand diodes104t,106t. The IGBTs103r,103s,103t,105r,105s,105tare switching elements, as well as self-turn-off elements. The diodes104r,104s,104tare diodes for reverse blocking. The diodes104r,104s,104tare connected in series to the IGBTs103r,103s,103t, with a polarity such that the forward currents flow through the diodes104r,104s,104tin the case of forward currents respectively flowing through the IGBTs103r,103s,103t. Specifically, anodes of the diodes104r,104s,104tand emitters of the IGBTs103r,103s,103tare connected to each other. Further, the diodes106r,106s,106tare diodes for reverse blocking. The diodes106r,106s,106tare connected in series to the IGBTs105r,105s,105t, with a polarity such that the forward currents flow through the diodes106r,106s,106tin the case of forward currents respectively flowing through the IGBTs105r,105s,105t. Specifically, cathodes of the diodes106r,106s,106tand collectors of the IGBTs105r,105s,105tare connected to each other. Collectors of IGBTs103r,103s,103tand emitters of the IGBTs105r,105s,105tare connected to each other via connecting points107r,107s,107t. The reverse blocking diode blocks flowing of the current in a reverse direction in the self-turn-off element, while preventing application of a reverse voltage to the self-turn-off element and destruction of the element.

Further, an r-phase voltage Vr from the three-phase alternating-current power supply120is inputted into the connecting point107rvia a coil L11in the LC filter circuit130. Similarly, an s-phase voltage Vs from the three-phase alternating-current power supply120is inputted into the connecting point107svia a coil L12in the LC filter circuit130. A t-phase voltage Vt from the three-phase alternating-current power supply120is inputted into the connecting point107tvia a coil L13in the LC filter circuit130. It is to be noted that in the LC filter circuit130, the coils L11, L12, L13and capacitors C11, C12, C13are configured as a low-pass filter.

As thus described, in the three-phase current source rectifier circuit shown inFIG. 2, the emitters of the IGBTs103r,103s,103tare connected to one another respectively via the diodes104r,104s,104t. This prevents commonality of the emitters of the IGBTs103r,103s,103tas a GND terminal of a control circuit. Further, in the three-phase current source rectifier circuit shown inFIG. 2, since different phase voltages are applied to the respective collectors of the IGBTs103r,103s,103t, respective collector potentials are different. Accordingly, in the case of driving the IGBTs103r,103s,103t,105r,105s,105tin the three-phase current source rectifier circuit shown inFIG. 2, independent drive power supplies have been required respectively for the IGBTs103r,103s,103t,105r,105s,105t. In the three-phase current source rectifier circuit shown inFIG. 2, independent six drive power supplies are required.

Meanwhile,FIG. 1shows a current source power conversion circuit according to the present embodiment, and the current source power conversion circuit is similar toFIG. 2in being also a three-phase current source rectifier circuit. The circuit shown inFIG. 1is a three-phase current source rectifier circuit. The three-phase current source rectifier circuit shown inFIG. 1includes three half-bridge rectifier circuits connected in parallel to one another. Specifically, a half-bridge rectifier circuit2rcorresponding to an r-phase has IGBTs3r,5rand diodes4r,6r. Further, a half-bridge rectifier circuit2scorresponding to an s-phase has IGBTs3s,5sand diodes4s,6s. Moreover, a half-bridge rectifier circuit2tcorresponding to a t-phase has IGBTs3t,5tand diodes4t,6t. The IGBTs3r,3s,3t,5r,5s,5tare switching elements, as well as self-turn-off elements. The diodes4r,4s,4tare diodes for reverse blocking. The diodes4r,4s,4tare connected in series to the IGBTs3r,3s,3t, with a polarity such that the forward currents flow through the diodes4r,4s,4tin the case of forward currents respectively flowing through the IGBTs3r,3s,3t, to constitute a switch circuit in an upper arm. Specifically, cathodes of the diodes4r,4s,4tand collectors of the IGBTs3r,3s,3tare connected to each other. Further, the diodes6r,6s,6tare diodes for reverse blocking. The diodes6r,6s,6tare connected in series to the IGBTs5r,5s,5t, with a polarity such that the forward currents flow through the diodes6r,6s,6tin the case of forward currents respectively flowing through the IGBTs5r,5s,5t, to constitute a switch circuit in a lower arm. Specifically, anodes of the diodes6r,6s,6tand emitters of the IGBTs5r,5s,5tare connected to each other. Anodes of the diodes4r,4s,4tand cathodes of the IGBTs6r,6s,6tare connected to each other via connecting points7r,7s,7t. Further, the connecting points7r,7s,7tare connected with a three-phase alternating-current power supply8via an LC filter circuit30. It is to be noted that in the LC filter circuit30, coils L1, L2, L3and capacitors C1, C2, C3are configured as a low-pass filter.

In the three-phase current source rectifier circuit shown inFIG. 1, serial connection of the IGBTs3r,5rand the diode4r,6rconfigured as thus described is grasped as a one-phase half-bridge rectifier circuit2r. Similarly, serial connection of the IGBTs3s,5sand the diodes4s,6sis grasped as a one-phase half-bridge rectifier circuit2s, and serial connection of the IGBTs3t,5tand the diodes4s,6sis grasped as a half-bridge rectifier circuit2t. In the three-phase current source rectifier circuit shown inFIG. 1, these three half-bridge rectifier circuits2r,2s,2tare connected in parallel. Further, forward directions of the IGBTs3r,3s,3t, the diodes4r,4s,4t, the IGBTs5r,5s,5tand the diodes6r,6s,6tare made uniform in the same direction in any of the half-bridge rectifier circuits2r,2s,2t. Further, in the three-phase current source rectifier circuit shown inFIG. 1, emitters of the IGBTs3r,3s,3tin the respective phases are connected respectively to a connection line9and short-circuited, thereby to make the emitters of the IGBTs3r,3s,3ta common potential. That is, in the multiphase current source rectifier circuit according to the present embodiment, emitter terminals of the self-turn-off elements (3r,3s,3t) in the respective phases in the one-side arm are short-circuited and connected to one another, so that these emitter terminals function as a common potential.

As the three-phase current source rectifier circuit shown inFIG. 1, by connecting the emitters of the IGBTs3r,3s,3tin the respective phases respectively to the connection line9and making these emitters function as the common potential, reference potentials of drive power supplies in drive circuits that drive the IGBTs3r,3s,3tin the respective phases can be made the same potential as one another. This allows commonality of the drive power supplies for the drive circuits that drive the IGBTs3r,3s,3tin the respective phases. Specifically, as shown inFIG. 3, the circuit is configured such that one drive power supply11is connected in parallel to drive circuits10r,10sthat drive the IGBTs3r,3sin the respective phases. It should be noted that, although only two phases (r, s) in the one-side arm (upper arm) are described in the circuit diagram shown inFIG. 3, similarly, the upper arm of the half-bridge rectifier circuit2tcan also be provided with a drive circuit and the drive power supply11can also be shared by the drive circuit.

As thus described, in the three-phase current source rectifier circuit according to the present embodiment, the circuit configuration as inFIG. 3can be adopted, and thereby, one drive power supply11can drive the respective drive circuits that drive the IGBTs on the upper arm side. Therefore, in the three-phase current source rectifier circuit according to the present embodiment, the number of drive power supplies can be made four in total, together with the respective (three) drive power supplies for the drive circuits that drive the three IGBTs5r,5s,5tin the lower arm. Further, in the three-phase current source rectifier circuit according to the present embodiment, the number of wires can be reduced by reduction in number of drive power supplies, thereby to form an inexpensive and simple circuit configuration. Moreover, in the three-phase current source rectifier circuit according to the present embodiment, it is possible to seek to save space by a space corresponding to the reduced drive power supplies.

It should be noted that, although the example of using the IGBT as the self-turn-off element has been described in the present embodiment, the present invention is not restricted to this, and another element having a similar function may also be applied. Further, although the present embodiment has been described as the three-phase current source rectifier circuit, the present invention is not restricted to the three phases.

FIG. 4shows a circuit diagram of a current source power conversion circuit according to the present embodiment. Although the current source power conversion circuit shown inFIG. 4is a three-phase current source rectifier circuit, only IGBTs3r,3scorresponding to the two phases (r, s) in the upper arm and the IGBT5rcorresponding to the one phase (r) in the lower arm are described inFIG. 4. Also in the current source rectifier circuit shown inFIG. 4, the emitters of the IGBTs3r,3sin the respective phases are connected respectively to the connection line9, to make the emitters of the IGBTs3r,3sfunction as a common potential, thereby allowing commonality of the drive power supply11for the drive circuits10r,10sthat drive the IGBTs3r,3sin the respective phases. As described above, the commonality of the drive power supply11is allowed also with respect to the drive circuit that drives the IGBT3t.

In the lower arm of the current source rectifier circuit shown inFIG. 4, by means of a bootstrap circuit, the drive power supply11that drives drive circuits10r,10sis used, to drive a drive circuit13of the IGBT5s. Specifically, the bootstrap circuit shown inFIG. 4includes a diode12connected in series to the positive electrode of a drive power supply11, and a capacitor14connected to the drive circuit13that drives IGBT5r. In the bootstrap circuit shown inFIG. 4, a cathode of the diode12is connected to one terminal of the capacitor14, and the other terminal of the capacitor14is connected to an anode of the diode6r. In the bootstrap circuit shown inFIG. 4, by turning on the IGBT3rin the upper arm, the capacitor14is charged by the drive power supply11. In addition, it can also be grasped that the diode12is a discharge blocking diode for blocking discharge of the capacitor14to the power supply11, and fulfills the function of holding a potential difference between a potential of the power supply11and a potential (this varies depending upon an r-phase voltage Vr) of the charged capacitor14, to block a reverse flow to the power supply11. Further, the diode12may be another element so long as having voltage resistant characteristics not less than a potential of the drive power supply11.

In the current source rectifier circuit according to the present embodiment, the charged capacitor14is used for the drive power supply to drive the drive circuit13. A reference potential of the voltage across the charged capacitor14is the emitter potential of the IGBT5r. It should be noted that, according to the present embodiment, it is assumed that a reference potentials of the gate signals are the emitter potentials of the IGBTs3r,3s,3tin the upper arm, respectively. Therefore a level shift circuit15is connected to the drive circuit13, and suitably shifts a potential of the gate signal and inputs the gate signal into the drive circuit13.

As thus described, in the current source rectifier circuit according to the present embodiment, through use of the bootstrap circuit, a power supply that drives the drive circuit13of the IGBT5rin the lower arm is produced, to allow the commonality of the actually provided power supply11. In addition, although the circuit configuration has been disclosed in the current source rectifier circuit shown inFIG. 4which allows the commonality of the drive power supply with respect to the IGBT5rcorresponding to one phase (r), similarly, commonality of drive power supplies with respect to the IGBTs5s,5tin the other phases (s, t) can also be sought through use of the bootstrap circuit. That is, the number of drive power supplies that drive the three-phase current source rectifier circuit can be made one. Further, in the case of driving the current source rectifier circuit according to the present embodiment, the IGBTs3r,3s,3tin the upper arm are brought into conduction to charge the capacitor14connected to the drive circuit in the lower arm, out of the need for ensuring a drive power supply voltage, before the IGBTs5r,5s,5tin the lower arm start switching operations.

It should be noted that the level shift circuit shown in the present embodiment is replaceable by an insulating circuit using a photo coupler, or the like. Further, in the case of the reference potential of the gate signal being different from the emitter potentials of the IGBTs3r,3s,3tin the upper arm, the level shift circuit or the insulating circuit is also required in the upper arm.

Modified Example

Although the configuration using the bootstrap circuit has been described in the current source rectifier circuit shown inFIG. 4, another circuit configuration may also be adopted so long as being a configuration which further includes the capacitor14to be charged by the drive power supply11and the diode12for blocking discharge of the capacitor14to the drive power supply11, and drives the drive circuit in the lower arm by the electric charge having charged the capacitor14.

Specifically, in the current source rectifier circuit according to the present modified example, a circuit configuration using a charge pump circuit in place of the bootstrap circuit is described.FIG. 5shows a circuit diagram of a current source power conversion circuit according to the present modified example. Although the current source power conversion circuit shown inFIG. 5is a three-phase current source rectifier circuit, only IGBTs3r,3scorresponding to the two phases (r, s) in the upper arm and the IGBT5rcorresponding to the one phase (r) in the lower arm are described inFIG. 5It should be noted that, since the current source power conversion circuit shown inFIG. 5is the same as the current source power conversion circuit shown inFIG. 4except for the charge pump circuit, the same reference numerals are given to the same constitutional elements, and a detailed description is omitted.

Specifically, the charge pump circuit shown inFIG. 5includes diodes12,16connected in series to the positive electrode of the drive power supply11, and a capacitor14connected to the drive circuit13that drives IGBT5r. Further, the charge pump circuit shown inFIG. 5includes switch elements (e.g., MOSFETs)17,18connected in series to a negative electrode of the drive power supply11and one terminal of the capacitor14, an oscillation circuit19that controls the switch elements, and a capacitor20connected to a point between the diodes12,16and to a point between the switch elements17,18.

In the charge pump circuit shown inFIG. 5, one terminal of the capacitor14is connected to an anode of the diode6rand the switch element18, and the other terminal of the capacitor14is connected to a cathode of the diode12. Further, the oscillation circuit19makes the switch elements17,18perform an exclusive operation. Hence in the charge pump circuit shown inFIG. 5, the capacitor20is charged by the drive power supply11when the switch element17is turned on and the switch element18is turned off. Next, an electric charge staying in the capacitor20is moved to the capacitor14when the switch element17is turned off and the switch element18is turned on.

Also in the three-phase current source rectifier circuit according to the present modified example, the charged capacitor14is used for the drive power supply to drive the drive circuit13. A reference potential of the voltage across the charged capacitor14is the emitter potential of the IGBT5r. It should be noted that the level shift circuit15is connected to the drive circuit13, and suitably shifts a potential of the gate signal and inputs the gate signal into the drive circuit13.

As thus described, in the three-phase current source rectifier circuit according to the present modified example, through use of the charge pump circuit, a power supply that drives the drive circuit13of the IGBT5rin the lower arm is produced, to allow the commonality of the actually provided power supply11. In addition, although the circuit configuration has also been disclosed in the three-phase current source rectifier circuit shown inFIG. 5which allows the commonality of the drive power supply with respect to the IGBT5rcorresponding to one phase (r), similarly, commonality of drive power supplies of the IGBTs5s,5tin the other phases (s, t) can also be sought through use of the charge pump circuit. That is, the number of drive power supplies that drive the three-phase current source rectifier circuit can be made one.

FIG. 6shows a circuit diagram of a current source power conversion circuit according to the present embodiment. The current source power conversion circuit shown inFIG. 6is a three-phase current source rectifier circuit. A configuration of the three-phase current source rectifier circuit shown inFIG. 6is almost the same as the configuration of the three-phase current source rectifier circuit shown inFIG. 4, but is different in no inclusion of the diode12. The diode12is a discharge blocking diode for blocking discharge of the capacitor14to the power supply11. In the three-phase current source rectifier circuit according to the present embodiment, the function of the diode12is substituted by the diode4rconnected in series to the IGBT3r. However, the diode4rneeds to have voltage resistant characteristics which are required of the diode12. In a voltage source inverter and rectifier circuit, and a current source inverter, normally, a drive power supply is provided taking a low potential of a direct current bus (or high-frequency link, etc.) as a reference potential. Hence the potential of the capacitor charged by the bootstrap circuit may be higher than that of the drive power supply, and the diode12is required to have voltage resistance not less than the potential of direct current bus (or high-frequency rink, etc.). In the present example, the diode12can be substituted by the diode4rsince the drive power supply is provided taking a high potential of the direct current bus (or high-frequency link, etc.) as a reference potential, and voltage resistance has been imparted to the diode4rin the current source power conversion circuit.

It should be noted that in the same configuration as the three-phase current source rectifier circuit shown inFIG. 4, the same reference numerals are given to the same constitutional elements, and a detailed description of the three-phase current source rectifier circuit shown inFIG. 6is omitted.

As thus described, in the three-phase current source rectifier circuit according to the present embodiment, the diode12is substituted by the diode4r, and thereby, the discharge blocking diode can be eliminated, to seek simplification of the circuit. It should be noted that in the three-phase current source rectifier circuit shown inFIG. 6, although discharge prevention of the capacitor14corresponding to one phase (r) has been described, similarly, the diodes4s,4tcan also be made to function as the discharge blocking diodes in the other phases (s, t). Further, also in the case of driving the three-phase current source rectifier circuit according to the present embodiment, the IGBTs3r,3s,3tin the upper arm are brought into conduction out of the need for ensuring a drive power supply voltage before the IGBTs5r,5s,5tin the lower arm start switching operations.

Further, although the three-phase current source rectifier circuit shown inFIG. 6has a circuit configuration using the bootstrap circuit, similarly, the configuration according to the present embodiment is also applicable to the three-phase current source rectifier circuit using the charge pump circuit. However, in the three-phase current source rectifier circuit (corresponding toFIG. 5) using the charge pump circuit, the function of the diode12is substituted by the diode6rconnected in series to the IGBT5r.

FIG. 7shows a circuit diagram of a current source power conversion circuit according to the present embodiment. The current source power conversion circuit shown inFIG. 7is a three-phase current source rectifier circuit. A configuration of the three-phase current source rectifier circuit shown inFIG. 7is almost the same as the configuration of the three-phase current source rectifier circuit shown inFIG. 4, but is different in a connected position of the diode6r. Although the diode6rhas been connected on the emitter side of the IGBT5rinFIG. 4, it is connected on the collector side of the IGBT5rin the present embodiment. That is, inFIG. 7, the diode6ris arranged farther away from the switch circuit (IGBT3r, diode4r) in the upper arm than the IGBT5r.

It is to be noted that in the same configuration as the three-phase current source rectifier circuit shown inFIG. 4, the same reference numerals are given to the same constitutional elements, and a detailed description of the three-phase current source rectifier circuit shown inFIG. 7is omitted.

As thus described, in the three-phase current source rectifier circuit according to the present embodiment, the diode6rfor reverse blocking is connected on the collector side of the IGBT5raway from the switch circuit in the upper arm, and thereby, a voltage drop of the diode6rcan be eliminated at the time of charging the capacitor14. For this reason, in the three-phase current source rectifier circuit according to the present embodiment, it is possible to ensure a further high drive power supply voltage (charged voltage of the capacitor14) for driving the drive circuit13of the IGBT5r, so as to improve the reliability of the operation. It should be noted that in the three-phase current source rectifier circuit shown inFIG. 7, elimination of the voltage drop of the capacitor14corresponding to one phase (r) has been described, similarly, the diodes6s,6tcan also be arranged away from the switch circuit in the upper arm, to eliminate voltage drops of the capacitor in the other phases (s, t). Moreover, with the potential of the drive power supply11being higher than the high potential of the direct current bus (or high-frequency rink), the potential of the capacitor14may be high, and a potential difference between the emitter potential of the IGBT5rin the lower arm and the low potential of the direct current bus may be large. However, also in that case, the diode6rcan be imparted with voltage resistant characteristics, thereby preventing the IGBT5rin the lower arm from being destroyed due to shortage of reverse voltage resistance.

Further, although the three-phase current source rectifier circuit shown inFIG. 7has a circuit configuration using the bootstrap circuit, similarly, the configuration according to the present embodiment is also applicable to the current source rectifier circuit using the charge pump circuit. Moreover, although the description has been given with the configuration provided with the diode12in the three-phase current source rectifier circuit shown inFIG. 7, the present invention is not restricted to this, and as in the three-phase current source rectifier circuit shown inFIG. 6, the diode12may be substituted by the diode4r.

FIG. 8shows a circuit diagram of a current source power conversion circuit according to the present embodiment. The current source power conversion circuit shown inFIG. 8is a three-phase current source rectifier circuit. In the current source power conversion circuits according to Embodiments 1 to 4, the switch circuits of the half-bridge rectifier circuits2r,2s,2thave been made up of the IGBTs3r,3s,3t,5r,5s,5tbeing the self-turn-off elements and the diodes4r,4s,4t,6r,6s,6t. However, in the current source power conversion circuit shown inFIG. 8, the switch circuits of the half-bridge rectifier circuit2r,2sare made up of self-turn-off elements22r,22s,23rhaving reverse voltage resistance in place of the IGBTs3r,3s,5rand the diodes4r,4s,6r. It is to be noted that an RB-I GBT (Reverse Blocking Insulated Gate Bipolar Transistor) is cited as the self-turn-off elements22r,22s,23rhaving reverse voltage resistance, for example. Further, since the current source power conversion circuit shown inFIG. 8is the same as the current source power conversion circuit shown inFIG. 4except for the self-turn-off elements22r,22s,23r, the same constitutional numerals are given to the same constitutional elements, and a detailed description is omitted. Further, although the current source power conversion circuit shown inFIG. 8is a three-phase current source rectifier circuit, as inFIG. 4, only the self-turn-off elements22r,22scorresponding to the two phases (r, s) in the upper arm and the self-turn-off element23rcorresponding to the one phase (r) in the lower arm are described inFIG. 8.

In the current source power conversion circuit shown inFIG. 8, the number of elements constituting the switch circuit is reduced as compared with the switch circuit (IGBTs3r,3s,3t,5r,5s,5tand diodes4r,4s,4t,6r,6s,6t) of the current source power conversion circuit shown inFIG. 4. Therefore, in the current source power conversion circuit shown inFIG. 8, the circuit configuration can be further simplified and an inexpensive configuration is formed. Further, in the current source power conversion circuit shown inFIG. 8, since a loss that occurs in the switch circuit decreases, a heat sink for heat dissipation can be made smaller, so as to further seek to save space.

Modified Example

FIG. 9is a circuit diagram of a current source power conversion circuit according to Modified Example 1 of the present embodiment. The current source power conversion circuit shown inFIG. 9is a three-phase current source rectifier circuit. The current source power conversion circuit shown inFIG. 9is one obtained by applying the configuration of Embodiment 3 to the current source power conversion circuit shown inFIG. 8. That is, the current source power conversion circuit shown inFIG. 9has a circuit configuration in which the self-turn-off elements22r,22s,23rhaving reverse voltage resistant characteristics are also imparted with a function as the discharge blocking diode, thereby to eliminate the diode12. It should be noted that, since the current source power conversion circuit shown inFIG. 9is the same as the current source power conversion circuit shown inFIG. 8except for elimination of the diode12, the same constitutional numerals are given to the same constitutional elements, and a detailed description is omitted. Further, although the current source power conversion circuit shown inFIG. 9is a three-phase current source rectifier circuit, as inFIG. 4, only the self-turn-off elements22r,22scorresponding to the two phases (r, s) in the upper arm and the self-turn-off element23rcorresponding to the one phase (r) in the lower arm are described inFIG. 9. It is to be noted that inFIGS. 8 and 9, as the self-turn-off elements22r,22s,23rhaving reverse voltage resistant characteristics, the RB-IGBT is represented by use of a symbol as shown in the drawing.

As thus described, in the current source power conversion circuit according to the present modified example, as in Embodiment 3, since the number of elements constituting the switch circuit decreases and a voltage drop in the switch circuit decreases, a further high charged voltage of the capacitor14can be ensured. Therefore, in the current source power conversion circuit according to the present modified example, the reliability in the operation of the switch circuit in the lower arm can further be improved.

By use of the current source power conversion circuits according to Embodiments 1 to 5 and the modified examples thereof, it is possible to configure the current source power conversion circuit, including the drive circuit, with simple circuit. This allows configuration of the current source power conversion circuit in a space saving manner. Thereat, in the present embodiment, the current source power conversion circuits according to Embodiments 1 to 5 and the modified examples thereof can be placed inside one module, to realize a current source power conversion circuit module.

While the present invention has been described in detail, the foregoing description is in all aspects illustrative, and not restrictive for the present invention. It is understood that numerous non-illustrated modified examples can be devised without departing from the scope of the present invention.

EXPLANATION OF REFERENCE NUMERALS