JP7054835B2 - Power converter - Google Patents

Description

The present invention relates to a power conversion device in general, and more particularly to a power conversion device that converts power from a DC power source.

In recent years, with the widespread use of photovoltaic power generation devices, fuel cells, power storage devices, etc. for residential use, various circuits have been proposed and provided as power conversion devices that convert the output of these DC power sources into alternating current. For example, Patent Documents 1 and 2 describe a power conversion device that generates an AC output converted from a DC voltage source into a plurality of voltage levels (“multi-level power conversion device” in Patent Document 1, “converter circuit” in Patent Document 2). Is disclosed.

According to the description of Patent Document 1, the power conversion device is a 5-level inverter that outputs a voltage of 5 levels, and includes two DC capacitors, two flying capacitors, and ten switching elements. ing. In this power conversion device, when the DC voltage E is applied to the series circuit of the two DC capacitors, the voltage of each DC capacitor becomes E / 2, and the voltage of each flying capacitor becomes E / 4. By controlling the switching element, a voltage of 5 levels is output.

Japanese Unexamined Patent Publication No. 2014-64431 Japanese Patent No. 4369425

By the way, in the power conversion device described in Patent Documents 1 and 2, in order to perform a steady operation of outputting a voltage of 5 levels as described above, a flying capacitor is first used after the DC power supply (DC voltage source) is turned on. It is necessary to charge up to the specified voltage (E / 4). However, the power conversion device described in Patent Documents 1 and 2 is configured to charge the flying capacitor in steady operation, and no load is connected between the output terminals of the AC output (none). Under load conditions), the flying capacitor cannot be charged.

The present invention has been made in view of the above reasons, and an object of the present invention is to provide a power conversion device capable of charging a capacitor required for steady operation even in a no-load state.

In order to solve the above problems, the power conversion device according to an embodiment of the present invention is electrically connected between a first input point and a reference potential point on the high potential side of a DC power supply, and has a first capacitor and a plurality of power converters. The first conversion circuit that switches the potential of the first output point and the second output point by the switching element of the above, and the second input point and the reference potential point on the low potential side of the DC power supply are electrically connected to each other. The second conversion circuit that switches the potential of the third output point and the fourth output point by two capacitors and a plurality of switching elements is electrically connected between the first output point and the third output point, and is the first output terminal. Is electrically connected between the first output switching circuit that switches the potential of the first output point and the potential of the third output point, and the second output point and the fourth output point. A second output switching circuit that switches the potential of the two output terminals between the potential of the second output point and the potential of the fourth output point, and the first capacitor and the second capacitor after the power supply from the DC power supply is started. A voltage adjustment circuit that slows up the DC voltage output from the DC power supply, a voltage detector that detects the voltage of the first capacitor or the second capacitor, and voltage detection during the start-up period until the capacitor is charged to the specified voltage. It includes a determination unit for determining whether or not the voltage of the first capacitor or the second capacitor detected by the unit has reached a specified voltage, and a control unit for controlling the on / off of a plurality of switching elements. In the first conversion circuit, between the first input point and the reference potential point, the first switching element, the second switching element, the third switching element, and the fourth switching element are in this order from the first input point side. Then, the first to fourth switching elements electrically connected in series and the series circuit of the second switching element and the third switching element are electrically connected in parallel, and the fifth switching from the high potential side. The fifth to sixth switching elements electrically connected in series, the series circuit of the second switching element and the third switching element, and the fifth switching element and the fifth switching element in the order of the element and the sixth switching element. It has a series circuit of 6 switching elements and a first capacitor electrically connected in parallel, and the connection point between the second switching element and the third switching element is set as the first output point, and the fifth switching. The connection point between the element and the sixth switching element is set as the second output point, and the second conversion circuit is the seventh switching element, the seventh switching element from the reference potential point side between the reference potential point and the second input point. The 8th switching element, the 9th switching element, and the 10th switching element are connected in this order, and the 7th to 10th switching elements electrically connected in series, and the 8th switching element and the 9th switching element are connected in series. The eleventh to twelfth switching elements electrically connected in parallel with the circuit and electrically connected in series in the order of the eleventh switching element and the twelfth switching element from the high potential side, and the eighth switching. It has a series circuit of the element and the ninth switching element and a second capacitor electrically connected in parallel with the series circuit of the eleventh switching element and the twelfth switching element, and has an eighth switching element and a ninth switching element. The connection point with the switching element is the third output point, the connection point between the eleventh switching element and the twelfth switching element is the fourth output point, and the first output switching circuit is the first output point. It has a thirteenth switching element connected between the first output terminal and a fourteenth switching element connected between the third output point and the first output terminal. The second output switching circuit includes a fifteenth switching element connected between the second output point and the second output terminal, and a sixteenth switching element connected between the fourth output point and the second output terminal. It has a switching element. During the start-up period, the control unit operates the voltage adjustment circuit, turns on the first switching element, the fourth switching element, the seventh switching element, and the tenth switching element, and turns on the other switching elements. Is turned off, and when the determination unit determines that the voltage of the first capacitor or the second capacitor has reached the specified voltage, the first switching element, the fourth switching element, the seventh switching element, and the tenth Switch the switching element of to the off state.

The present invention has an advantage that the capacitor required for steady operation can be charged even in a no-load state.

It is a figure which shows the structure of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a figure which shows four switching patterns for switching the potential of the 1st output point of a 1st conversion circuit. It is a figure which shows four switching patterns for switching the potential of the 2nd output point of a 1st conversion circuit. It is a figure which shows four switching patterns for switching the potential of the 3rd output point of a 2nd conversion circuit. It is a figure which shows four switching patterns for switching the potential of the 4th output point of a 2nd conversion circuit. It is a figure which shows the structure of the voltage adjustment circuit provided in the power conversion apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the voltage adjustment circuit provided in the power conversion apparatus which concerns on Embodiment 2. FIG.

(Embodiment 1)
FIG. 1 shows the configuration of the power conversion device 10 according to the first embodiment. As shown in FIG. 1, the power conversion device 10 according to the present embodiment includes a first conversion circuit 1, a second conversion circuit 2, a first output switching circuit 5a, and a second output switching circuit 5b. There is.

The first conversion circuit 1 is electrically connected between the first input point 101 on the high potential side of the DC power supply 4 and the reference potential point 100. The first conversion circuit 1 has the magnitude of the voltage generated between the first output point 103 and the reference potential point 100 and the magnitude of the voltage generated between the second output point 104 and the reference potential point 100. Is switched in three stages of zero, first level, and second level.

The second conversion circuit 2 is electrically connected between the second input point 102 on the low potential side of the DC power supply 4 and the reference potential point 100. The second conversion circuit 2 has the magnitude of the voltage generated between the reference potential point 100 and the third output point 105 and the magnitude of the voltage generated between the reference potential point 100 and the fourth output point 106. Is switched in three stages of zero, third level, and fourth level.

The first output switching circuit 5a is electrically connected between the first output point 103 and the third output point 105, and has a thirteenth switching element Q13 and a thirteenth switching element Q14. The first output switching circuit 5a switches the potential of the first output terminal OUT1 between the first output point 103 of the first conversion circuit 1 and the third output point 105 of the second conversion circuit 2.

The second output switching circuit 5b is electrically connected between the second output point 104 and the fourth output point 106, and has a fifteenth switching element Q15 and a sixth switching element Q16. The second output switching circuit 5b switches the potential of the second output terminal OUT2 between the second output point 104 of the first conversion circuit 1 and the fourth output point 106 of the second conversion circuit 2.

The first conversion circuit 1 has switching elements Q1 to Q6 of the first to sixth and a first capacitor C1. The first to fourth switching elements Q1 to Q4 are electrically connected in series between the first input point 101 and the reference potential point 100. The first to fourth switching elements Q1 to Q4 are in the order of the first switching element Q1, the second switching element Q2, the third switching element Q3, and the fourth switching element Q4 from the first input point 101 side. They are connected in series.

The fifth to sixth switching elements Q5 to Q6 are electrically connected in parallel with the series circuit of the second switching element Q2 and the third switching element Q3. The fifth to sixth switching elements Q5 to Q6 are connected in series in the order of the fifth switching element Q5 and the sixth switching element Q6 from the high potential side.

The first capacitor C1 is electrically connected in parallel with the series circuit of the second switching element Q2 and the third switching element Q3 and the series circuit of the fifth switching element Q5 and the sixth switching element Q6. ing. In the first conversion circuit 1, the connection point between the second switching element Q2 and the third switching element Q3 is set as the first output point 103, and the connection point between the fifth switching element Q5 and the sixth switching element Q6 is set as the first output point 103. The second output point 104 is used.

The second conversion circuit 2 has the switching elements Q7 to Q12 of the seventh to twelfth and the second capacitor C2. The seventh to tenth switching elements Q7 to Q10 are electrically connected in series between the reference potential point 100 and the second input point 102. The seventh to tenth switching elements Q7 to Q10 are in series from the reference potential point 100 side in the order of the seventh switching element Q7, the eighth switching element Q8, the ninth switching element Q9, and the tenth switching element Q10. It is connected to the.

The eleventh to twelfth switching elements Q11 to Q12 are electrically connected in parallel with the series circuit of the eighth switching element Q8 and the ninth switching element Q9. The eleventh to twelfth switching elements Q11 to Q12 are connected in series in the order of the eleventh switching element Q11 and the twelfth switching element Q12 from the high potential side.

The second capacitor C2 is electrically connected in parallel with the series circuit of the eighth switching element Q8 and the ninth switching element Q9 and the direct circuit of the eleventh switching element Q11 and the twelfth switching element Q12. ing. In the second conversion circuit 2, the connection point between the eighth switching element Q8 and the ninth switching element Q9 is set as the third output point 105, and the connection point between the eleventh switching element Q11 and the twelfth switching element Q12 is set as the third output point 105. The fourth output point 106 is used.

During the start-up period from the start of power supply from the DC power supply 4 to the charging of the first capacitor C1 and the second capacitor C2 to the specified voltage, the first switching element Q1, the fourth switching element Q4, and the seventh The switching element Q7 and the tenth switching element Q10 of the above are turned on. At this time, the first capacitor C1 and the second capacitor C2 are connected in series with the DC power supply 4.

That is, until the first capacitor C1 and the second capacitor C2 are charged to the specified voltage, the charging path of the first capacitor C1 and the second capacitor C2 is between the first input point 101 and the second input point 102. Is formed. Therefore, the power conversion device 10 has an advantage that the capacitors (first capacitor C1 and second capacitor C2) required for steady operation can be charged even in a no-load state.

Further, although not shown, the power conversion device 10 according to the present embodiment includes an inductor in addition to the above configuration. The inductor is electrically connected between the first output terminal OUT1 and the second output terminal OUT2 and the system power supply.

Hereinafter, the power conversion device 10 according to the present embodiment will be described in detail. However, the configuration described below is merely an example of the present invention, and the present invention is not limited to the following embodiments, and even other than this embodiment deviates from the technical idea of the present invention. As long as it does not, various changes can be made depending on the design and the like.

In the present embodiment, the case where the power conversion device 10 is provided in a residential power conditioner used by electrically connecting to a photovoltaic power generation device as a DC power source 4 is illustrated, but the power conversion device 10 is illustrated. It is not intended to limit the use of. The power conversion device 10 may be used by being electrically connected to a DC power source 4 other than a photovoltaic power generation device such as a household fuel cell or a power storage device, or may be used in a non-residential state such as a store, a factory, or an office. May be used for. Further, the power conversion device 10 may be used in addition to the power conditioner.

<Structure of power converter>
As shown in FIG. 1, the power conversion device 10 of the present embodiment is electrically connected to a DC power source 4 composed of a photovoltaic power generation device via a junction box (not shown). In the present embodiment, the power conversion device 10 includes a voltage adjustment circuit 3 and a third capacitor C3 in addition to the first conversion circuit 1, the second conversion circuit 2, the first output switching circuit 5a, and the second output switching circuit 5b. A fourth capacitor C4, a first voltage detection unit 7a, a second voltage detection unit 7b, a determination unit 8, and a control unit 9 are provided.

The first output point 103 and the second output point 104 of the first conversion circuit 1 and the third output point 105 and the fourth output point 106 of the second conversion circuit 2 are the first output switching circuit 5a and the second output switching circuit 5b. It is electrically connected to the system power supply (commercial power system) via the inductor. Specifically, the output of the power conversion device 10 (the output of the first output switching circuit 5a and the second output switching circuit 5b) is an interconnection breaker provided on a distribution board (not shown) via an inductor. By being electrically connected (not shown), it is connected to the grid power supply.

Next, the configuration of each part of the power conversion device 10 will be described in detail.

The voltage adjusting circuit 3 is configured to adjust the magnitude of the voltage applied to the first conversion circuit 1 and the second conversion circuit 2. In the example of FIG. 1, the voltage adjusting circuit 3 is electrically connected between the DC power supply 4 and the first conversion circuit 1 and the second conversion circuit 2. As a result, the DC voltage output from the DC power supply 4 is applied to the first conversion circuit 1 and the second conversion circuit 2 as the applied voltage via the voltage adjustment circuit 3. Each of the pair of output ends of the voltage adjusting circuit 3 becomes a first input point 101 and a second input point 102.

The voltage adjusting circuit 3 elapses the magnitude of the applied voltage between the first input point 101 and the second input point 102 in the starting period until the first capacitor C1 and the second capacitor C2 are charged to the specified voltage. It is a slow-up circuit that gradually increases with the increase. The specific configuration of the voltage adjustment circuit 3 will be described later.

The third capacitor C3 and the fourth capacitor C4 are electrically connected in series between the first input point 101 and the second input point 102. That is, a series circuit of the third capacitor C3 and the fourth capacitor C4 is connected between the pair of output ends of the voltage adjusting circuit 3. The circuit constant (capacitance) of the third capacitor C3 and the circuit constant (capacitance) of the fourth capacitor C4 are the same value.

The output voltage of the voltage adjusting circuit 3 is divided by the third capacitor C3 and the fourth capacitor C4. Therefore, when the voltage adjustment circuit 3 outputs the input voltage from the DC power supply 4 as it is, the voltage across each of the third capacitor C3 and the fourth capacitor C4 is the output voltage E of the DC power supply 4, respectively. It will be represented by E / 2 [V] using V].

Here, the connection point between the third capacitor C3 and the fourth capacitor C4 is the reference potential point 100. It is assumed that the reference potential point 100 is the circuit ground and the potential of the reference potential point 100 is 0 [V]. Then, when the voltage across each of the third capacitor C3 and the fourth capacitor C4 is E / 2 [V], the potential of the first input point 101 becomes E / 2 [V], and the potential of the second input point 102 becomes E / 2 [V]. The potential is −E / 2 [V].

As described above, the first conversion circuit 1 includes the first to fourth switching elements Q1 to Q4 connected in series between the first input point 101 and the reference potential point 100, and the second switching elements Q2 and the second. 5th to 6th switching elements Q5 to Q6 connected in parallel with the series circuit of the switching element Q3 of 3 and connected in series in the order of the 5th switching element Q5 and the 6th switching element Q6 from the high potential side. , The series circuit of the second switching element Q2 and the third switching element Q3, and the first capacitor C1 connected in parallel with the series circuit of the fifth switching element Q5 and the sixth switching element Q6. .. As examples of the switching elements Q1 to Q6 of the first to sixth, a depletion type n-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is used.

The drain of the first switching element Q1 is electrically connected to the first input point 101. The drain of the second switching element Q2 is electrically connected to the source of the first switching element Q1. The drain of the third switching element Q3 is electrically connected to the source of the second switching element Q2. The drain of the fourth switching element Q4 is electrically connected to the source of the third switching element Q3. Further, the source of the fourth switching element Q4 is electrically connected to the reference potential point 100. The source of the second switching element Q2 (drain of the third switching element Q3) is the first output point 103.

The drain of the fifth switching element Q5 is electrically connected to the source of the first switching element Q1. The drain of the sixth switching element Q6 is electrically connected to the source of the fifth switching element Q5. Further, the source of the sixth switching element Q6 is electrically connected to the drain of the fourth switching element Q4. The source of the fifth switching element Q5 (drain of the sixth switching element Q6) is the second output point 104.

One end of the first capacitor C1 is electrically connected to the drain of the second switching element Q2 and the drain of the fifth switching element Q5, and the other end is the source of the third switching element Q3 and the sixth switching element Q6. It is electrically connected to the source of. In other words, one end of the first capacitor C1 is electrically connected to the first input point 101 via the first switching element Q1, and the other end is electrically connected to the reference potential point 100 via the fourth switching element Q4. Is connected.

As described above, the second conversion circuit 2 includes the seventh to tenth switching elements Q7 to Q10 connected in series between the reference potential point 100 and the second input point 102, and the eighth switching elements Q8 and the second conversion circuit 2. The 11th to 12th switching elements Q11 to Q12 connected in parallel with the series circuit of the switching element Q9 of 9 and connected in series in the order of the 11th switching element Q11 and the 12th switching element Q12 from the high potential side. It has a series circuit of the eighth switching element Q8 and the ninth switching element Q9, and a second capacitor C2 connected in parallel with the series circuit of the eleventh switching element Q11 and the twelfth switching element Q12. Here, the second conversion circuit 2 has basically the same configuration as the first conversion circuit 1, and the switching elements Q7 to Q10 of the seventh to tenth correspond to the switching elements Q1 to Q4 of the first to fourth. The 11th to 12th switching elements Q11 to Q12 correspond to the 5th to 6th switching elements Q5 to Q6, and the second capacitor C2 corresponds to the first capacitor C1. As the 7th to 12th switching elements Q7 to Q12, a depletion type n-channel MOSFET is used as in the 1st to 6th switching elements Q1 to Q6.

The drain of the seventh switching element Q7 is electrically connected to the reference potential point 100. The drain of the eighth switching element Q8 is electrically connected to the source of the seventh switching element Q7. The drain of the ninth switching element Q9 is electrically connected to the source of the eighth switching element Q8. The drain of the tenth switching element Q10 is electrically connected to the source of the ninth switching element Q9. Further, the source of the tenth switching element Q10 is electrically connected to the second input point 102. The source of the eighth switching element Q8 (drain of the ninth switching element Q9) is the third output point 105.

The drain of the eleventh switching element Q11 is electrically connected to the source of the seventh switching element Q7. The drain of the twelfth switching element Q12 is electrically connected to the source of the eleventh switching element Q11. Further, the source of the twelfth switching element Q12 is electrically connected to the drain of the tenth switching element Q10. The source of the eleventh switching element Q11 (drain of the twelfth switching element Q12) is the fourth output point 106.

One end of the second capacitor C2 is electrically connected to the drain of the eighth switching element Q8 and the drain of the eleventh switching element Q11, and the other end is the source of the ninth switching element Q9 and the twelfth switching element Q12. It is electrically connected to the source of. In other words, one end of the second capacitor C2 is electrically connected to the reference potential point 100 via the seventh switching element Q7, and the other end is electrically connected to the second input point 102 via the tenth switching element Q10. Is connected. The circuit constant (capacitance) of the second capacitor C2 and the circuit constant (capacitance) of the first capacitor C1 are the same value.

The first output switching circuit 5a is a thirteenth switching element Q13 directly connected between the first output point 103 of the first conversion circuit 1 and the third output point 105 of the second conversion circuit 2 as described above. It also has a 14th switching element Q14.

The drain of the thirteenth switching element Q13 is electrically connected to the first output point 103. The drain of the 14th switching element Q14 is electrically connected to the source of the 13th switching element Q13. The source of the 14th switching element Q14 is electrically connected to the 3rd output point 105. The source of the thirteenth switching element Q13 (drain of the fourteenth switching element Q14) becomes the first output terminal OUT1.

The second output switching circuit 5b is a fifteenth switching element Q15 directly connected between the second output point 104 of the first conversion circuit 1 and the fourth output point 106 of the second conversion circuit 2 as described above. It also has a 16th switching element Q16.

The drain of the fifteenth switching element Q15 is electrically connected to the second output point 104. The drain of the 16th switching element Q16 is electrically connected to the source of the 15th switching element Q15. The source of the 16th switching element Q16 is electrically connected to the 4th output point 106. The source of the fifteenth switching element Q15 (drain of the sixteenth switching element Q16) is the second output terminal OUT2.

The 13th to 16th switching elements Q13 to Q16 may be composed of a plurality of switching elements connected in series. As a result, low withstand voltage switching elements such as inexpensive and high-performance MOSFETs can be used as the 13th to 16th switching elements Q13 to Q16, so that an inexpensive and high-performance power conversion device can be provided. In particular, in the example shown in FIG. 1, since the switching elements Q13 to Q16 of the 13th to 16th are composed of three switching elements connected in series, all the switching elements constituting the power conversion device 10 are formed. The withstand voltage of Q1 to Q16 can all be E / 4 [V].

In FIG. 1, diodes 1 to 16 are connected in antiparallel to each of the switching elements Q1 to Q16 of the first to 16th. These first to 16 diodes are parasitic diodes of the switching elements Q1 to Q16 of the first to 16th, respectively. That is, the parasitic diode of the first switching element Q1 constitutes the first diode, and similarly, the parasitic diode of each of the switching elements Q2, Q3 ... Of the second, third ... constitutes the diode of the second, third ... do. For example, the first diode is connected so that the drain side of the first switching element Q1 is the cathode and the source side is the anode.

The gates of the switching elements Q1 to Q16 of the first to 16th are electrically connected to the control unit 9. The control unit 9 can individually switch on / off of the switching elements Q1 to Q6 of the first to sixth, thereby controlling the first conversion circuit 1. Further, the control unit 9 can individually switch on / off of the switching elements Q7 to Q12 of the seventh to twelfth, thereby controlling the second conversion circuit 2. Further, the control unit 9 can individually switch on / off of the switching elements Q13 to Q16 of the 13th to 16th, thereby controlling the first output switching circuit 5a and the second output switching circuit 5b.

The control unit 9 may be individually provided for each of the first conversion circuit 1, the second conversion circuit 2, the first output switching circuit 5a, and the second output switching circuit 5b. Further, although FIG. 1 shows the configuration of the power conversion device 10 for a single phase, a similar circuit may be provided for a plurality of phases, for example, three phases.

<Basic operation of power converter>
The basic operation of the power conversion device 10 having the above-described configuration will be briefly described with reference to FIGS. 2 to 5. The thick line in the figure represents the current path.

The basic operation of the power conversion device 10 referred to here is the operation of the power conversion device 10 after the start period has elapsed, that is, after the first capacitor C1 and the second capacitor C2 have been charged to a specified voltage. The specified voltage for the first capacitor C1 is half (1/2) the voltage across the third capacitor C3, and the specified voltage for the second capacitor C2 is half (1/2) the voltage across the fourth capacitor C4. be.

In the following, it is assumed that the voltage adjustment circuit 3 outputs the output voltage E [V] of the DC power supply 4 as it is during the basic operation of the power conversion device 10. Therefore, the voltage across each of the third capacitor C3 and the fourth capacitor C4 is E / 2 [V], the potential of the first input point 101 is E / 2 [V], and the potential of the second input point 102 is E / 2 [V]. The potential is −E / 2 [V]. Further, the voltage across each of the first capacitor C1 and the second capacitor C2 charged to the specified voltage is E / 4 [V], respectively.

The power conversion device 10 sets the switching patterns of the switching elements Q1 to Q16 of the first to 16 constituting the first conversion circuit 1, the second conversion circuit 2, the first output switching circuit 5a, and the second output switching circuit 5b. By switching, the DC voltage (E [V]) applied between the first input point 101 and the second input point 102 is converted into an AC voltage and output from the first output terminal OUT1 and the second output terminal OUT2. do.

FIG. 2 shows four switching patterns for switching the potential of the first output point 103 of the first conversion circuit 1. The potential of the first output point 103 is E / 2 [V] by switching the switching pattern of the first switching element Q1, the second switching element Q2, the third switching element Q3, and the fourth switching element Q4. ], E / 4 [V], 0 [V] can be switched to three levels.

In the switching pattern of FIG. 2A, the first switching element Q1 and the second switching element Q2 are in the on state, and the third switching element Q3 and the fourth switching element Q4 are in the off state. In this state, the first output point 103 is electrically connected to the first input point 101 via the second switching element Q2 and the first switching element Q1. Therefore, the first output point 103 has the same potential (E / 2 [V]) as the first input point 101.

In the switching pattern of FIG. 2B, the first switching element Q1 and the third switching element Q3 are in the on state, and the second switching element Q2 and the fourth switching element Q4 are in the off state. In this state, the first output point 103 is electrically connected to the first input point 101 via the third switching element Q3, the first capacitor C1, and the first switching element Q1. Therefore, the first output point 103 has a potential lower than the potential (E / 2 [V]) of the first input point 101 by the voltage across the first capacitor C1 (E / 4 [V]), that is, E / 4 (=). E / 2-E / 4) [V].

In the switching pattern of FIG. 2C, the second switching element Q2 and the fourth switching element Q4 are in the on state, and the first switching element Q1 and the third switching element Q3 are in the off state. In this state, the first output point 103 is electrically connected to the reference potential point 100 via the second switching element Q2, the first capacitor C1, and the fourth switching element Q4. Therefore, the first output point 103 has a potential higher than the potential (0 [V]) of the reference potential point 100 by the voltage across the first capacitor C1 (E / 4 [V]), that is, E / 4 (= 0 + E / 4). ) [V].

In the switching pattern of FIG. 2D, the third switching element Q3 and the fourth switching element Q4 are in the on state, and the first switching element Q1 and the second switching element Q2 are in the off state. In this state, the first output point 103 is electrically connected to the reference potential point 100 via the third switching element Q3 and the fourth switching element Q4. Therefore, the first output point 103 has the same potential (0 [V]) as the reference potential point 100.

The switching pattern of FIG. 2B and the switching pattern of FIG. 2C are both switching patterns in which the potential of the first output point 103 is E / 4 [V], but the current from the DC power supply to the system power supply. In the switching pattern of FIG. 2 (b), the first capacitor C1 is charged, and in the switching pattern of FIG. 2 (c), the first capacitor C1 is discharged. Therefore, the voltage across the first capacitor C1 can be maintained at the specified voltage by selecting one of the switching patterns according to the voltage across the first capacitor C1 detected by the first voltage detection unit 7a. .. When a current flows from the grid power supply to the DC power supply, that is, when the AC voltage is converted to the DC voltage, such as when the storage battery is charged by the grid power supply, conversely, in the switching pattern of FIG. 2 (b), the first The capacitor C1 is discharged, and the first capacitor C1 is charged in the switching pattern of FIG. 2C. Also in this case, the voltage across the first capacitor C1 can be maintained at the specified voltage by selecting one of the switching patterns according to the voltage across the first capacitor C1 detected by the first voltage detection unit 7a. can.

FIG. 3 shows four switching patterns for switching the potential of the second output point 104 of the first conversion circuit 1. The potential of the second output point 104 is E / 2 [V] by switching the switching pattern of the first switching element Q1, the fifth switching element Q5, the sixth switching element Q6, and the fourth switching element Q4. ], E / 4 [V], 0 [V] can be switched to three levels.

In the switching pattern of FIG. 3A, the first switching element Q1 and the fifth switching element Q5 are in the on state, and the sixth switching element Q6 and the fourth switching element Q4 are in the off state. In this state, the second output point 104 is electrically connected to the first input point 101 via the fifth switching element Q5 and the first switching element Q1. Therefore, the second output point 104 has the same potential (E / 2 [V]) as the first input point 101.

In the switching pattern of FIG. 3B, the first switching element Q1 and the sixth switching element Q6 are in the on state, and the fifth switching element Q5 and the fourth switching element Q4 are in the off state. In this state, the second output point 104 is electrically connected to the first input point 101 via the sixth switching element Q6, the first capacitor C1, and the first switching element Q1. Therefore, the second output point 104 has a potential lower than the potential (E / 2 [V]) of the first input point 101 by the voltage across the first capacitor C1 (E / 4 [V]), that is, E / 4 (=). E / 2-E / 4) [V].

In the switching pattern of FIG. 3C, the fifth switching element Q5 and the fourth switching element Q4 are in the on state, and the first switching element Q1 and the sixth switching element Q6 are in the off state. In this state, the second output point 104 is electrically connected to the reference potential point 100 via the fifth switching element Q5, the first capacitor C1, and the fourth switching element Q4. Therefore, the second output point 104 has a potential higher than the potential (0 [V]) of the reference potential point 100 by the voltage across the first capacitor C1 (E / 4 [V]), that is, E / 4 (= 0 + E / 4). ) [V].

In the switching pattern of FIG. 3D, the sixth switching element Q6 and the fourth switching element Q4 are in the on state, and the first switching element Q1 and the fifth switching element Q5 are in the off state. In this state, the second output point 104 is electrically connected to the reference potential point 100 via the sixth switching element Q6 and the fourth switching element Q4. Therefore, the second output point 104 has the same potential (0 [V]) as the reference potential point 100.

The switching pattern of FIG. 3B and the switching pattern of FIG. 3C are both switching patterns in which the potential of the second output point 104 is E / 4 [V], but depending on the direction in which the current flows. In the switching pattern of FIG. 3 (b), the first capacitor C1 is charged or discharged, and in the switching pattern of FIG. 3 (c), the first capacitor C1 is discharged or charged, so that it is detected by the first voltage detection unit 7a. By selecting one of the switching patterns according to the voltage across the first capacitor C1, the voltage across the first capacitor C1 can be maintained at a specified voltage.

FIG. 4 shows four switching patterns for switching the potential of the third output point 105 of the second conversion circuit 2. The potential of the third output point 105 is −E / 2 [ It can be switched to three levels of V], -E / 4 [V], and 0 [V].

In the switching pattern of FIG. 4A, the tenth switching element Q10 and the ninth switching element Q9 are in the on state, and the eighth switching element Q8 and the seventh switching element Q7 are in the off state. In this state, the third output point 105 is electrically connected to the second input point 102 via the ninth switching element Q9 and the tenth switching element Q10. Therefore, the third output point 105 has the same potential (−E / 2 [V]) as the second input point 102.

In the switching pattern of FIG. 4B, the tenth switching element Q10 and the eighth switching element Q8 are in the on state, and the ninth switching element Q9 and the seventh switching element Q7 are in the off state. In this state, the third output point 105 is electrically connected to the second input point 102 via the eighth switching element Q8, the second capacitor C2, and the tenth switching element Q10. Therefore, the third output point 105 has a potential higher than the potential of the second input point 102 (-E / 2 [V]) by the voltage across the second capacitor C2 (E / 4 [V]), that is, -E / 4. (= −E / 2 + E / 4) [V].

In the switching pattern of FIG. 4C, the ninth switching element Q9 and the seventh switching element Q7 are in the on state, and the tenth switching element Q10 and the eighth switching element Q8 are in the off state. In this state, the third output point 105 is electrically connected to the reference potential point 100 via the ninth switching element Q9, the second capacitor C2, and the seventh switching element Q7. Therefore, the third output point 105 has a potential lower than the potential (0 [V]) of the reference potential point 100 by the voltage across the second capacitor C2 (E / 4 [V]), that is, −E / 4 (= 0−). E / 4) [V].

In the switching pattern of FIG. 4D, the eighth switching element Q8 and the seventh switching element Q7 are in the on state, and the tenth switching element Q10 and the ninth switching element Q9 are in the off state. In this state, the third output point 105 is electrically connected to the reference potential point 100 via the eighth switching element Q8 and the seventh switching element Q7. Therefore, the third output point 105 has the same potential (0 [V]) as the reference potential point 100.

The switching pattern of FIG. 4B and the switching pattern of FIG. 4C are both switching patterns in which the potential of the third output point 105 is −E / 4 [V], but depending on the direction in which the current flows. Since the second capacitor C2 is discharged or charged in the switching pattern of FIG. 4 (b) and the second capacitor C2 is charged or discharged in the switching pattern of FIG. 4 (c), it is detected by the second voltage detection unit 7b. By selecting one of the switching patterns according to the voltage across the second capacitor C2, the voltage across the second capacitor C2 can be maintained at a specified voltage.

FIG. 5 shows four switching patterns for switching the potential of the fourth output point 106 of the second conversion circuit 2. The potential of the fourth output point 106 is −E / 2 [ It can be switched to three levels of V], -E / 4 [V], and 0 [V].

In the switching pattern of FIG. 5A, the tenth switching element Q10 and the twelfth switching element Q12 are in the on state, and the eleventh switching element Q11 and the seventh switching element Q7 are in the off state. In this state, the fourth output point 106 is electrically connected to the second input point 102 via the twelfth switching element Q12 and the tenth switching element Q10. Therefore, the fourth output point 106 has the same potential (−E / 2 [V]) as the second input point 102.

In the switching pattern of FIG. 5B, the tenth switching element Q10 and the eleventh switching element Q11 are in the on state, and the twelfth switching element Q12 and the seventh switching element Q7 are in the off state. In this state, the fourth output point 106 is electrically connected to the second input point 102 via the eleventh switching element Q11, the second capacitor C2, and the tenth switching element Q10. Therefore, the fourth output point 106 has a potential higher than the potential of the second input point 102 (−E / 2 [V]) by the voltage across the second capacitor C2 (E / 4 [V]), that is, −E / 4. (= −E / 2 + E / 4) [V].

In the switching pattern of FIG. 5C, the twelfth switching element Q12 and the seventh switching element Q7 are in the on state, and the tenth switching element Q10 and the eleventh switching element Q11 are in the off state. In this state, the fourth output point 106 is electrically connected to the reference potential point 100 via the twelfth switching element Q12, the second capacitor C2, and the seventh switching element Q7. Therefore, the fourth output point 106 has a potential lower than the potential (0 [V]) of the reference potential point 100 by the voltage across the second capacitor C2 (E / 4 [V]), that is, −E / 4 (= 0−). E / 4) [V].

In the switching pattern of FIG. 5D, the eleventh switching element Q11 and the seventh switching element Q7 are in the on state, and the tenth switching element Q10 and the twelfth switching element Q12 are in the off state. In this state, the fourth output point 106 is electrically connected to the reference potential point 100 via the eleventh switching element Q11 and the seventh switching element Q7. Therefore, the fourth output point 106 has the same potential (0 [V]) as the reference potential point 100.

The switching pattern of FIG. 5B and the switching pattern of FIG. 5C are both switching patterns in which the potential of the fourth output point 106 is −E / 4 [V], but depending on the direction in which the current flows. Since the second capacitor C2 is discharged or charged in the switching pattern of FIG. 5 (b) and the second capacitor C2 is charged or discharged in the switching pattern of FIG. 5 (c), it is detected by the second voltage detection unit 7b. By selecting one of the switching patterns according to the voltage across the second capacitor C2, the voltage across the second capacitor C2 can be maintained at a specified voltage.

The first output switching circuit 5a switches the potential of the first output terminal OUT1 between the potential of the first output point 103 of the first conversion circuit 1 and the potential of the third output point 105 of the second conversion circuit 2. That is, if the thirteenth switching element Q13 is turned on and the fourteenth switching element Q14 is turned off, the first output point 103 and the first output terminal OUT1 are electrically connected, and the first output terminal OUT1 is the first output. It becomes the same potential as the point 103. If the thirteenth switching element Q13 is turned off and the fourteenth switching element Q14 is turned on, the third output point 105 and the first output terminal OUT1 are electrically connected, and the first output terminal OUT1 is the third output point 105. It becomes the same potential as. Therefore, the power conversion device 10 sets the potential of the first output terminal OUT1 to 5 of E / 2 [V], E / 4 [V], 0, -E / 4 [V], and -E / 2 [V]. It is possible to switch between stages.

The second output switching circuit 5b switches the potential of the second output terminal OUT2 between the potential of the second output point 104 of the first conversion circuit 1 and the potential of the fourth output point 106 of the second conversion circuit 2. That is, if the fifteenth switching element Q15 is turned on and the sixteenth switching element Q16 is turned off, the second output point 104 and the second output terminal OUT2 are electrically connected, and the second output terminal OUT2 is the second output. It becomes the same potential as the point 104. If the fifteenth switching element Q15 is turned off and the sixteenth switching element Q16 is turned on, the fourth output point 106 and the second output terminal OUT2 are electrically connected, and the second output terminal OUT2 is the fourth output point 106. It becomes the same potential as. Therefore, the power conversion device 10 sets the potential of the second output terminal OUT2 to 5 of E / 2 [V], E / 4 [V], 0, -E / 4 [V], and -E / 2 [V]. It is possible to switch between stages.

The power conversion device 10 outputs a voltage corresponding to the potential difference between the first output terminal OUT1 and the second output terminal OUT2. The control unit 9 controls the switching patterns shown in FIGS. 2 to 5 and the switching patterns of the first output switching circuit 5a and the second output switching circuit 5b to obtain a desired voltage at the first output terminals OUT1 and the second. Output from the output terminal OUT2. For example, the control unit 9 outputs an output voltage similar to a sine wave by switching the switching pattern while changing the on-duty of the PWM (Pulse Width Modulation) signal.

Since the four switching patterns of FIG. 2 and the four switching patterns of FIG. 3 share the first switching element Q1 and the fourth switching element Q4, the switching of FIGS. 2 (a) or 2 (b). The pattern and the switching pattern of FIG. 3 (c) or FIG. 3 (d) cannot be realized at the same time, and the switching pattern of FIG. 2 (c) or FIG. 2 (d) and the switching pattern of FIG. 2 (a) or FIG. 3 (b) cannot be realized at the same time. ) Switching patterns cannot be realized at the same time. However, since there are a plurality of switching patterns capable of outputting the same voltage from the first output terminal OUT1 and the second output terminal OUT2, an appropriate switching pattern may be selected according to the voltage across the first capacitor C1 and the like.

Further, since the four switching patterns of FIG. 5 and the four switching patterns of FIG. 6 share the seventh switching element Q7 and the tenth switching element Q10, the switching of FIGS. 4 (a) or 4 (b). The pattern and the switching pattern of FIG. 5 (c) or FIG. 5 (d) cannot be realized at the same time, and the switching pattern of FIG. 4 (c) or FIG. 4 (d) and the switching pattern of FIG. 5 (a) or FIG. 5 (b) cannot be realized at the same time. ) Switching patterns cannot be realized at the same time. However, since there are a plurality of switching patterns capable of outputting the same voltage from the first output terminal OUT1 and the second output terminal OUT2, an appropriate switching pattern may be selected according to the voltage across the second capacitor C2 and the like.

In the basic operation of the power conversion device 10 according to the present embodiment, the switching elements Q13 to Q16 of the first output switching circuit 5a and the second output switching circuit 5b are controlled so as to operate only when the polarity of the output voltage is switched. It is possible. Therefore, the frequency of the duty control of the switching elements Q13 to Q16 is considerably lower than the frequency of the duty control of the switching elements Q1 to Q12 constituting the first conversion circuit 1 and the second conversion circuit 2. Therefore, instead of the respective switching elements Q13 to Q16, a plurality of switching elements having a lower withstand voltage can be connected in series. In the power conversion device 10 according to the present embodiment, in the switching elements Q13 to Q16 of the first output switching circuit 5a and the second output switching circuit 5b, the rising edge of the control signal input to the plurality of switching elements connected in series or Even if there is a slight shift in the on / off timing of multiple switching elements due to a shift in the fall timing or a difference in the characteristics of the switching elements, a snubber circuit or the like suppresses the sudden rise in voltage and appropriately protects it. Because it can be done.

As described above, in the power conversion device 10 of the present embodiment, the voltage applied to each of the switching elements Q1 to Q16 of the first to 16 during the basic operation is suppressed to E / 4 [V] or less.

<Voltage adjustment circuit configuration>
FIG. 6 shows the configuration of the voltage adjusting circuit 3 provided in the power conversion device 10 according to the first embodiment. In this embodiment, the voltage adjusting circuit 3 includes a resistor 31, a first switch element 32, and a second switch element 33, as shown in FIG.

The resistance 31 and the first switch element 32 are electrically connected in series between the output end on the high potential side of the DC power supply 4 and the first input point 101. The second switch element 33 is electrically connected in parallel with the series circuit of the resistor 31 and the first switch element 32 between the output end on the high potential side of the DC power supply 4 and the first input point 101. ing. The first switch element 32 and the second switch element 33 are controlled by the control unit 9, and are individually switched on / off.

When the voltage adjusting circuit 3 is operated, the first switch element 32 is turned on, the second switch element 33 is turned off, and the third capacitor C3 and the fourth capacitor C4 are placed via the resistor 31. It is electrically connected to the DC power supply 4. At this time, due to the time constant determined by the resistance value of the resistor 31 and the capacitance values of the third capacitor C3 and the fourth capacitor C4, the voltage across each of the third capacitor C3 and the fourth capacitor C4 is set from the time when the DC power supply 4 is turned on. It gradually increases with the passage of time. In other words, the voltage adjusting circuit 3 adjusts the magnitude of the voltage applied to the first conversion circuit 1 and the second conversion circuit 2 so as to slow down with the passage of time.

On the other hand, when the voltage adjusting circuit 3 is not operated, the first switch element 32 is turned off, the second switch element 33 is turned on, and the third capacitor C3 and the fourth capacitor C4 are directly connected to the DC power supply 4. Be connected.

The control unit 9 operates the voltage adjustment circuit 3 with the first switch element 32 turned on and the second switch element 33 turned off during the start period, and turns off the first switch element 32 and the second switch element 32 during the normal period. The switch element 33 of the above is turned on and the voltage adjustment circuit 3 is not operated. Here, the starting period may be a period from the turning on of the DC power supply 4 to the completion of charging of the third capacitor C3 and the fourth capacitor C4. The first switch element 32 may be omitted.

<Starting operation of power converter>
The start operation of the power conversion device 10 referred to here is the operation of the power conversion device 10 from the time when the power supply from the DC power supply 4 starts until the start period elapses and the basic operation starts and the normal period starts. Is. If the DC power supply 4 is a photovoltaic power generation device, the power conversion device 10 is stopped when the output of the photovoltaic power generation device is equal to or less than the specified value, and when the output of the photovoltaic power generation device exceeds the specified value, DC is applied. The power supply from the power source 4 starts, and the power conversion device 10 starts the starting operation.

The power conversion device 10 according to the present embodiment includes a voltage adjustment circuit 3, and has a first conversion circuit 1, a second conversion circuit 2, a first output switching circuit 5a, and a second output switching circuit 5a during a start period immediately after the DC power supply 4 is turned on. The voltage applied to the output switching circuit 5b is gradually increased to keep the voltage applied to each of the first to 16 switching elements Q1 to Q16 low. That is, until the first capacitor C1 and the second capacitor C2 are charged to the specified voltage, the application is applied to the first conversion circuit 1, the second conversion circuit 2, the first output switching circuit 5a, and the second output switching circuit 5b. Since the voltage is suppressed to a low level, the voltage applied to each of the switching elements Q1 to Q16 of the first to 16th is suppressed to a low level. Therefore, according to the power conversion device 10, there is an advantage that the withstand voltage of the switching element (Q1 to Q16) can be lowered.

In the power conversion device 10, since the first capacitor C1 and the second capacitor C2 are not charged at the time of starting, the first switching element Q1, the fourth switching element Q4, the seventh switching element Q7, and the tenth switching element Q1 The switching element Q10 is turned on, all other switching elements are turned off, the first capacitor C1 and the second capacitor C2 are connected in series with the DC power supply 4, and the first capacitor C1 and the second capacitor C2 are connected. Charge.

However, when the first switching element Q1, the fourth switching element Q4, the seventh switching element Q7, and the tenth switching element Q10 are turned on while the first capacitor C1 is not charged at all, these are Higher voltage than during basic operation can be applied to each end of each switching element of. As described above, in the basic operation of the power conversion device 10, the voltage applied to each of the switching elements Q1 to Q16 of the first to 16 can be suppressed to E / 4 [V] or less, so that these switching elements can be suppressed. The withstand voltage may be E / 4 [V], but if a voltage of E / 4 [V] or higher is applied in the starting operation, the withstand voltage is higher than that of E / 4 [V] only for the starting operation. Switching elements will have to be used.

In order to solve such a problem, in the power conversion device 10 of the present embodiment, the control unit 9 operates the voltage adjustment circuit 3 in the starting operation, and at the same time, the first switching element Q1 and the fourth switching. While turning on the element Q4, the seventh switching element Q7, and the tenth switching element Q10 and turning off the other switching elements, the voltage applied to the first capacitor C1 and the second capacitor C2 is slowed up. The first capacitor C1 and the second capacitor C2 are charged. In the determination unit 8, the voltage of the first capacitor C1 detected by the first voltage detection unit 7a and the voltage of the second capacitor C2 detected by the second voltage detection unit 7b are the specified voltage (E / 4 [V]. ) Is reached. When the control unit 9 determines by the determination unit 8 that the voltages of the first capacitor C1 and the second capacitor C2 have reached the specified voltage, the control unit 9 switches the first switching element Q1, the fourth switching element Q4, and the seventh switching. The element Q7 and the tenth switching element Q10 are switched to the off state. As a result, even in the starting operation, the voltage applied across all the switching elements is suppressed to E / 4 [V] or less, so that the switching element having a withstand voltage of E / 4 [V] can be used.

Therefore, the power conversion device 10 can charge the first capacitor C1 and the second capacitor C2 even if the first output terminal OUT1 and the second output terminal OUT2 are not connected to the system power supply. In other words, the power conversion device 10 operates constantly even when no load is connected between the output terminals of the AC output (first output terminal OUT1 and second output terminal OUT2) (no load state). The necessary capacitors (first capacitor C1 and second capacitor C2) can be charged. The steady operation referred to here is the operation of the power conversion device 10 after the lapse of the starting period, that is, after the first capacitor C1 and the second capacitor C2 are charged to the specified voltage, and is the same as the above-mentioned basic operation. It is synonymous.

During the start-up period, the first output terminal OUT1 and the second output terminal OUT2 are separated from the system power supply by turning off all the switching elements Q13 to Q16 of the first output switching circuit 5a and the second output switching circuit 5b. There is. Therefore, during the start-up period of the power conversion device 10, the voltage from the system power supply is not applied to the first conversion circuit 1 and the second conversion circuit 2.

The first capacitor C1 and the second capacitor C2 can be charged in the same manner during the basic operation of the power conversion device 10. As a result, even when the first capacitor C1 or the second capacitor C2 becomes a voltage lower than the specified voltage due to discharge, it can be charged at an appropriate timing and returned to the specified voltage. When the first capacitor C1 or the second capacitor C2 is charged during the basic operation, the first capacitor C1 and the second capacitor C2 are charged to a voltage close to the specified voltage, so that the voltage adjustment circuit 3 does not need to be operated. good.

<Effect>
According to the power conversion device 10 of the present embodiment described above, the first capacitor C1 and the second capacitor C2 are charged even if the first output terminal OUT1 and the second output terminal OUT2 are not connected to the system power supply. Is possible.

Further, the power conversion device 10 of the present embodiment includes a third capacitor C3 and a fourth capacitor C4 electrically connected in series between the first input point 101 and the second input point 102 of the DC power supply 4. Since the connection point between the third capacitor C3 and the fourth capacitor C4 is set as the reference potential point 100, if a single DC power supply 4 is connected between the first input point 101 and the second input point 102, the first DC power supply 4 is connected. A voltage divided by the third capacitor C3 and the fourth capacitor C4 can be applied to each of the first conversion circuit 1 and the second conversion circuit 2, respectively.

Further, the power conversion device 10 of the present embodiment is provided with the voltage adjustment circuit 3 as in the present embodiment, so that the first conversion circuit 1 and the second conversion circuit 2 can be connected to the first conversion circuit 1 and the second conversion circuit 2 in the start period immediately after the DC power supply 4 is turned on. Since it is configured to slow up the applied voltage of, the voltage applied to the first conversion circuit 1 and the second conversion circuit 2 is lowered before the first capacitor C1 and the second capacitor C2 are charged to the specified voltage. It can be suppressed. Therefore, the power conversion device 10 transfers to the switching elements Q1 to Q16 of the first to 16 not only in the normal period in which the basic operation is performed but also in the starting period in which the first capacitor C1 and the second capacitor C2 are not charged. Since the applied voltage can be suppressed to E / 4 [V] or less, the withstand voltage of the switching element (Q1 to Q16) can be lowered, and an inexpensive and high-performance power conversion device can be realized.

Further, in the power conversion device 10 according to the present embodiment, the first conversion circuit 1 and the second conversion circuit are turned off by turning off all the switching elements constituting the first output switching circuit 5a and the second output switching circuit 5b. 2 and the system power supply can be electrically separated. Therefore, the power conversion device 10 turns off all the switching elements constituting the first output switching circuit 5a and the second output switching circuit 5b during the start period, so that the switching elements 1 to 16 from the system power supply are turned off. No voltage is applied to Q1 to Q16, and the voltage applied to each of the switching elements Q1 to Q16 of the first to 16 can be suppressed to a low level.

(Embodiment 2)
FIG. 7 shows the configuration of the voltage adjusting circuit 3A provided in the power conversion device 10 according to the second embodiment. As shown in FIG. 7, the power conversion device 10 according to the present embodiment has a different voltage adjustment circuit configuration from the power conversion device 10 of the first embodiment. Hereinafter, the same configurations as those in the first embodiment will be designated by a common reference numeral and description thereof will be omitted as appropriate.

In the present embodiment, the voltage adjusting circuit 3A is composed of a step-down chopper circuit, and has a switch element 34, a diode 35, an inductor 36, and a diode 37, as shown in FIG. 7. Here, the switch element 34 is a depletion type n-channel MOSFET, and the diode 37 is a parasitic diode of the switch element 34.

The switch element 34 and the diode 35 are electrically connected in series between both ends of the DC power supply 4 so that the switch element 34 is on the high potential side. In the diode 35, the anode is connected to the low potential side of the DC power supply 4, and the cathode is connected to the source of the switch element 34. The inductor 36 is electrically connected between the source of the switch element 34 and the first input point 101.

The voltage adjusting circuit 3A having the above configuration gradually increases the voltage applied to the first conversion circuit 1 and the second conversion circuit 2 with the passage of time by gradually changing the duty ratio of the switch element 34 during the starting period. do. Here, as the control of the voltage adjusting circuit 3A, it is preferable to adopt the control so that the voltage across the switching elements Q1 to Q16 of the first to 16 does not exceed E / 4 [V] during the starting period.

According to the configuration of the present embodiment, the step-down chopper circuit for changing the magnitude of the DC voltage from the DC power supply 4 can be used as the voltage adjusting circuit 3A.

Other configurations and functions are the same as those in the first embodiment.

The present invention has been described above based on the examples. This embodiment is an example, and it is understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. ..

In each of the above embodiments, the switching elements Q1 to Q16 and the switch element 34 of the first to 16th embodiments are not limited to the depletion type n-channel MOSFET, and other semiconductor switches may be used. For example, a power semiconductor device using a wide bandgap semiconductor material such as an IGBT (Insulated Gate Bipolar Transistor) or GaN (gallium nitride) is used.

The power conversion device of one embodiment of the present invention is electrically connected between a first input point on the high potential side of a DC power supply and a reference potential point, and is a first output point by a first capacitor and a plurality of switching elements. The first conversion circuit that switches the potential of the second output point and the second input point on the low potential side of the DC power supply and the reference potential point are electrically connected by a second capacitor and a plurality of switching elements. The second conversion circuit that switches the potential of the third output point and the fourth output point is electrically connected between the first output point and the third output point, and the potential of the first output terminal is set to the first output point. The first output switching circuit that switches between the potential of the third output point and the potential of the third output point is electrically connected between the second output point and the fourth output point, and the potential of the second output terminal is set to the second. The second output switching circuit that switches between the potential of the second output point and the potential of the fourth output point, and the first capacitor and the second capacitor are charged to the specified voltage after the power supply from the DC power supply is started. A voltage adjustment circuit that slows up the DC voltage output from the DC power supply, a voltage detector that detects the voltage of the first capacitor or the second capacitor, and a first capacitor that is detected by the voltage detector during the start-up period up to. Alternatively, it includes a determination unit for determining whether or not the voltage of the second capacitor has reached a specified voltage, and a control unit for controlling the on / off of a plurality of switching elements. In the first conversion circuit, between the first input point and the reference potential point, the first switching element, the second switching element, the third switching element, and the fourth switching element are in this order from the first input point side. Then, the first to fourth switching elements electrically connected in series and the series circuit of the second switching element and the third switching element are electrically connected in parallel, and the fifth switching from the high potential side. The fifth to sixth switching elements electrically connected in series, the series circuit of the second switching element and the third switching element, and the fifth switching element and the fifth switching element in the order of the element and the sixth switching element. It has a series circuit of 6 switching elements and a first capacitor electrically connected in parallel, and the connection point between the second switching element and the third switching element is set as the first output point, and the fifth switching. The connection point between the element and the sixth switching element is set as the second output point, and the second conversion circuit is the seventh switching element, the seventh switching element from the reference potential point side between the reference potential point and the second input point. The 8th switching element, the 9th switching element, and the 10th switching element are connected in this order, and the 7th to 10th switching elements electrically connected in series, and the 8th switching element and the 9th switching element are connected in series. The eleventh to twelfth switching elements electrically connected in parallel with the circuit and electrically connected in series in the order of the eleventh switching element and the twelfth switching element from the high potential side, and the eighth switching. It has a series circuit of the element and the ninth switching element and a second capacitor electrically connected in parallel with the series circuit of the eleventh switching element and the twelfth switching element, and has an eighth switching element and a ninth switching element. The connection point with the switching element is the third output point, the connection point between the eleventh switching element and the twelfth switching element is the fourth output point, and the first output switching circuit is the first output point. It has a thirteenth switching element connected between the first output terminal and a fourteenth switching element connected between the third output point and the first output terminal. The second output switching circuit includes a fifteenth switching element connected between the second output point and the second output terminal, and a sixteenth switching element connected between the fourth output point and the second output terminal. It has a switching element. During the start-up period, the control unit operates the voltage adjustment circuit, turns on the first switching element, the fourth switching element, the seventh switching element, and the tenth switching element, and turns on the other switching elements. Is turned off, and when the determination unit determines that the voltage of the first capacitor or the second capacitor has reached the specified voltage, the first switching element, the fourth switching element, the seventh switching element, and the tenth Switch the switching element of to the off state.

According to this aspect, the first capacitor C1 and the second capacitor C2 can be charged even if the first output terminal and the second output terminal are not connected to the system power supply. Further, even when the uncharged first capacitor C1 and the second capacitor C2 are charged, the voltage applied to each of the switching elements Q1 to Q16 of the first to 16 can be suppressed to a low value, so that the withstand voltage of the switching element can be reduced. It can be lowered, and an inexpensive and high-performance power conversion device can be realized.

Each of the 13th to 16th switching elements may be composed of a plurality of switching elements connected in series.

According to this aspect, the withstand voltage of the 13th to 16th switching elements can be further reduced, and an inexpensive and high-performance power conversion device can be realized.

The voltage regulation circuit has a resistor and a switch element connected in parallel, and when the voltage regulator circuit is activated, the switch element is turned off, and the first conversion circuit and the second conversion circuit are via the resistor. When it is connected to a DC power supply and the voltage adjustment circuit is not activated, the switch element may be turned on and the first conversion circuit and the second conversion circuit may be connected to the DC power supply by bypassing the resistor.

According to this aspect, a voltage adjusting circuit can be realized with an inexpensive configuration.

1 1st conversion circuit, 2nd conversion circuit, 3 voltage adjustment circuit, 3A voltage adjustment circuit, 4 DC power supply, 5a 1st output switching circuit, 5b 2nd output switching circuit, 7a 1st voltage detector, 7b 2nd Voltage detection unit, 8 judgment unit, 9 control unit, 10 power converter, 31 resistance, 32 first switch element, 33 second switch element, 34 switch element, 35 capacitor, 36 inductor, 37 capacitor, 100 reference potential Point, 101 1st input point, 102 2nd input point, 103 1st output point, 104 2nd output point, 105 3rd output point, 106 4th output point, C1 1st capacitor, C2 2nd capacitor, C3 1st 3 capacitors, C4 4th capacitor, OUT1 1st output terminal, OUT2 2nd output terminal.

Claims (3)

A first that is electrically connected between a first input point on the high potential side of a DC power supply and a reference potential point, and switches the potentials of the first output point and the second output point by a first capacitor and a plurality of switching elements. With the conversion circuit,
It is electrically connected between the second input point on the low potential side of the DC power supply and the reference potential point, and the potentials of the third output point and the fourth output point are switched by the second capacitor and a plurality of switching elements. The second conversion circuit and
A second that is electrically connected between the first output point and the third output point and switches the potential of the first output terminal between the potential of the first output point and the potential of the third output point. 1 output switching circuit and
A second output point is electrically connected between the second output point and the fourth output point, and the potential of the second output terminal is switched between the potential of the second output point and the potential of the fourth output point. 2 output switching circuit and
A voltage adjustment circuit that slows up the DC voltage output from the DC power supply during the start-up period from the start of power supply from the DC power supply to the charging of the first capacitor and the second capacitor to the specified voltage. When,
A voltage detection unit that detects the voltage of the first capacitor or the second capacitor,
A determination unit for determining whether or not the voltage of the first capacitor or the second capacitor detected by the voltage detection unit has reached the specified voltage, and a determination unit.
A control unit that controls the on / off of the plurality of switching elements,
Equipped with
In the first conversion circuit, between the first input point and the reference potential point, the first switching element, the second switching element, the third switching element, and the fourth switching element from the first input point side. In the order of the switching elements, the first to fourth switching elements electrically connected in series and the series circuit of the second switching element and the third switching element are electrically connected in parallel and have a high potential. A series circuit of the fifth to sixth switching elements electrically connected in series, the second switching element, and the third switching element in the order of the fifth switching element and the sixth switching element from the side. Further, it has the first capacitor electrically connected in parallel with the series circuit of the fifth switching element and the sixth switching element, and the second switching element and the third switching element. The connection point is the first output point, and the connection point between the fifth switching element and the sixth switching element is the second output point.
The second conversion circuit has a seventh switching element, an eighth switching element, a ninth switching element, and a tenth switching from the reference potential point side between the reference potential point and the second input point. In the order of the elements, the 7th to 10th switching elements electrically connected in series and the series circuit of the 8th switching element and the 9th switching element are electrically connected in parallel, and the high potential side. From the eleventh switching element to the twelfth switching element, the series circuit of the eleventh to twelfth switching elements electrically connected in series, the eighth switching element, and the ninth switching element. It has the eleventh switching element and the second capacitor electrically connected in parallel with the series circuit of the twelfth switching element, and the connection between the eighth switching element and the ninth switching element. The point is the third output point, and the connection point between the eleventh switching element and the twelfth switching element is the fourth output point.
The first output switching circuit is connected between a thirteenth switching element connected between the first output point and the first output terminal, and between the third output point and the first output terminal. It has a 14th switching element and
The second output switching circuit is connected between the fifteenth switching element connected between the second output point and the second output terminal, and between the fourth output point and the second output terminal. It has a 16th switching element and
During the start-up period, the control unit operates the voltage adjustment circuit and turns on the first switching element, the fourth switching element, the seventh switching element, and the tenth switching element. When the other switching elements are turned off and the determination unit determines that the voltage of the first capacitor or the second capacitor has reached the specified voltage, the first switching element and the fourth The power conversion device, characterized in that the switching element of the above, the seventh switching element, and the tenth switching element are switched to the off state. The power conversion device according to claim 1, wherein each of the 13th to 16th switching elements is composed of a plurality of switching elements connected in series. The voltage regulator circuit has resistors and switch elements connected in parallel.
When the voltage adjustment circuit is activated, the switch element is turned off, and the first conversion circuit and the second conversion circuit are connected to the DC power supply via the resistance.
When the voltage adjusting circuit is not operated, the switch element is turned on, and the first conversion circuit and the second conversion circuit are connected to the DC power supply by bypassing the resistance. The power conversion device according to claim 1 or 2.

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