JP7611746B2 - Power Supplies - Google Patents

Description

The present invention relates to a power supply device.

Conventionally, bidirectional DC/DC converters that control the output voltage of a DC power source and exchange power with a DC power storage device of a different voltage have been widely used. In such DC/DC converters, the DC power source and the DC power storage device each normally require separate reactors, but a flying capacitor type DC/DC converter that achieves a similar function using a single reactor has been reported (see, for example, Non-Patent Document 1).

Miyashita et al., "Verification of Battery Management System Operation Using Flying Capacitor Type DC-DC Converter with Discontinuous Current Mode," Institute of Electrical Engineers Study Group Materials. SPC, Semiconductor Power Conversion Study Group, 2019

Here, in the case of a power source such as a solar cell whose output voltage and load capacity change depending on certain conditions, a DC/DC converter may be connected to an energy storage device such as a battery or a capacitor. In addition, many load devices such as home appliances run on single-phase AC, and an inverter is used to convert the DC power source to AC. Therefore, when using a DC power source whose output voltage fluctuates to make an AC power source, a DC/DC converter may be connected to an inverter device.
When a flying capacitor type DC/DC converter as described above is connected to an inverter device and used, the device is composed of a large number of power conversion switching elements and reactors, and as an emergency power source, there are challenges in terms of miniaturizing the entire device, increasing efficiency, and reducing cost.

The present invention was made in consideration of these circumstances, and aims to provide a power supply device that can convert DC power to AC power at low cost.

A power supply device according to one aspect of the present invention includes a single-phase inverter circuit having an H-bridge circuit, an input capacitor connected between a first power line connected to a high potential side of the H-bridge circuit and a second power line connected to a low potential side of the H-bridge circuit, a first DC power source connected in series between the first power line or the second power line and a first connection point, and a reactor, a first switch that controls a current flowing between the first connection point and a second connection point to a conductive state or a non-conductive state, a second switch that controls a current flowing between the first connection point and a third connection point to a conductive state or a non-conductive state, and a second DC power source having one end connected to the second connection point and the other end connected to the third connection point, and a second power supply unit that controls a current flowing between the third connection point and the second power line to a conductive state or a non-conductive state, a third switch that controls a current flowing between the first power supply line and the second connection point to a conductive state or a non-conductive state, a fourth switch that controls a current flowing between the third connection point and the second power supply line to a conductive state or a non-conductive state, a control unit that pulsates a voltage input to the single-phase inverter circuit at a frequency that is twice the frequency output by the single-phase inverter circuit , a first voltage detection unit that detects a voltage across the input capacitor, and a second voltage detection unit that detects an output voltage of the second DC power supply, and the control unit controls the conductive state of at least any of the first switch, the second switch, and the third switch based on the acquired voltage across the input capacitor and the output voltage of the second DC power supply so that the voltage across the input capacitor is greater than both of the output voltages of the first DC power supply and the second DC power supply .

In one aspect of the power supply device of the present invention, the voltage across the input capacitor is greater than the output voltage of both the first DC power supply and the second DC power supply.

In a power supply device according to one aspect of the present invention, the fourth switch may be a diode having an anode connected to the second connection point and a cathode connected to the first power line, or a diode having an anode connected to the second power line and a cathode connected to the third connection point.

In a power supply device according to one aspect of the present invention, the control unit controls the conductive state of at least one of the first switch, the second switch, and the third switch so that the voltage across the input capacitor is greater than the output voltage of either the first DC power source or the second DC power source.

The present invention provides a power supply device that can convert DC power to AC power at low cost.

1 is a circuit diagram showing an example of a circuit configuration of a power supply device according to a first embodiment; 4 is a diagram showing an example of a voltage fluctuation range across an input capacitor included in the power supply device according to the first embodiment; FIG. FIG. 11 is a diagram showing an example of a change over time in the value of a current flowing through a reactor when the power supply device according to the first embodiment is used in a discontinuous current mode to exchange power between a first DC power supply and a second DC power supply. FIG. 11 is a diagram showing an example of a change over time in the value of a current flowing through a reactor when the power supply device according to the first embodiment is used in a current continuous mode to exchange power between a first DC power supply and a second DC power supply. FIG. 11 is a diagram showing an example of a change over time in a current value flowing through a reactor when power is exchanged between a first DC power source and a single-phase inverter using the power supply device according to the first embodiment. FIG. 11 is a diagram showing an example of a change over time in a current value flowing through a reactor when power is exchanged between a second DC power source and a single-phase inverter using the power supply device according to the first embodiment. FIG. 11 is a circuit diagram showing an example of a circuit configuration of a power supply device according to a second embodiment. FIG. 1 is a diagram showing an example of a circuit diagram in which a flying capacitor type converter circuit and a single-phase inverter circuit according to a conventional technique are combined;

[Prior Art]
8 is a diagram showing an example of a circuit diagram in which a conventional flying capacitor type converter circuit and a single-phase inverter circuit are combined. Problems in the conventional technology will be described with reference to the diagram.
The circuit 90 is a combination of a conventional flying capacitor type converter circuit 91 and a conventional single-phase inverter circuit 92 .

The flying capacitor type converter circuit 91 includes a battery 911, a reactor 912, a solar cell 913, a switch 914, a switch 915, a switch 916, and a switch 917. The flying capacitor type converter circuit 91 transmits and receives power between the battery 911 and the solar cell 913 by switching the switches 914, 915, 916, and 917 at a predetermined timing. Note that the battery 911 and the solar cell 913 may be any device capable of transmitting and receiving power.

The single-phase inverter circuit 92 includes an H-bridge formed of switches 923, 924, 925, and 926, a reactor 921, and a load 922. The single-phase inverter circuit 92 controls the H-bridge to convert the DC power supplied from the flying capacitor type converter circuit 91 into single-phase AC power.

The single-phase inverter circuit 92 includes a capacitor 927 as an input capacitor. Typically, a large-capacity electrolytic capacitor is used as the input capacitor of a single-phase inverter circuit. The electrolytic capacitor has the disadvantage that the device itself is large and has a short lifespan. To compensate for this disadvantage, a small-capacity film capacitor is used as the capacitor 927 provided in the single-phase inverter circuit 92. Therefore, it is necessary to increase the voltage applied to the capacitor 927 and give the input voltage of the single-phase inverter circuit 92 a pulsation that is twice the power supply frequency (i.e., the frequency of the power output by the single-phase inverter circuit 30).

The circuit 90 includes a reactor 93, a switch 94, and a switch 95 in the connection between the flying capacitor type converter circuit 91 and the single-phase inverter circuit 92. The circuit 90 controls the current flowing through the reactor 93 by switching the switches 94 and 95 at a predetermined timing, thereby controlling the voltage provided as the input voltage to the single-phase inverter circuit 92.

As described above, according to the conventional technology, the reactor 93, the switch 94, and the switch 95 are required to connect the flying capacitor type converter circuit 91 and the single-phase inverter circuit 92. Therefore, there is a problem that the device becomes larger and more expensive as the reactor 93, the switch 94, and the switch 95 are increased.

[First embodiment]
1 is a circuit diagram showing an example of a circuit configuration of a power supply device according to a first embodiment. With reference to the diagram, an example of the circuit configuration of a power supply device 1 according to the first embodiment will be described.

[Circuit configuration of power supply device]
The power supply device 1 includes a first DC power supply 11, a reactor 12, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a second DC power supply 21, a single-phase inverter circuit 30, an input capacitor 40, and a control unit 50. The first DC power supply 11 and the reactor 12 are also referred to as a first power supply unit 10, and the first switch S1, the second switch S2, and the second DC power supply 21 are also referred to as a second power supply unit 20.

The single-phase inverter circuit 30 includes a reactor 31 and a load 32. The single-phase inverter circuit 30 also includes an H-bridge circuit including a switch 33, a switch 34, a switch 35, and a switch 36.
The input capacitor 40 is connected between a first power supply line PL1 connected to the high potential side of the H-bridge circuit and a second power supply line PL2 connected to the low potential side of the H-bridge circuit. The input capacitor 40 is a small-capacity film capacitor. Here, the small capacity may be, for example, about 88 μF (microfarads).
The voltage across the input capacitor 40 is greater than the output voltage of the first DC power supply 11 and greater than the output voltage of the second DC power supply 21. Specifically, the capacitance of the input capacitor 40 is set so that the voltage across the input capacitor 40 is greater than the output voltage of both the first DC power supply 11 and the second DC power supply 21.

For example, when the output voltage of the first DC power supply 11 becomes larger than the voltage across the input capacitor 40, the power stored in the first DC power supply 11 flows to the input capacitor 40 via the parasitic diode component of the first switch S1 and the parasitic diode component of the fourth switch S4. Therefore, the output voltage of the first DC power supply 11 and the voltage across the input capacitor 40 become approximately the same. Here, the "approximately the same" range is a range that takes into account the voltage drop due to the reactor 12, the parasitic diode component of the first switch S1, and the parasitic diode component of the fourth switch S4.

Similarly, when the output voltage of the second DC power supply 21 becomes larger than the voltage across the input capacitor 40, the power stored in the second DC power supply 21 flows to the input capacitor 40 via the parasitic diode component of the fourth switch S4 and the parasitic diode component of the third switch S3. Therefore, the output voltage of the second DC power supply 21 and the voltage across the input capacitor 40 become substantially the same. Here, the "substantially the same" range is a range that takes into account the voltage drop due to the parasitic diode component of the fourth switch S4 and the parasitic diode component of the third switch S3.

The first DC power supply 11 is a power supply capable of outputting DC power. The first DC power supply 11 may be a power supply with a unidirectional power flow such as a solar cell, or may be a power supply with a bidirectional power flow such as a battery. In this embodiment, the first DC power supply 11 may be replaced with a DC load.
The reactor 12 is connected in series to the first DC power supply 11. Fig. 1 shows an example of a case where the reactor 12 is connected in series to the positive terminal side of the first DC power supply 11. The reactor 12 may be connected in series to the negative terminal side of the first DC power supply 11.
The first DC power supply 11 and the reactor 12 connected in series have one end connected to the first connection point P1 and the other end connected to the second power supply line PL2. That is, the first DC power supply 11 and the reactor 12 are connected in series between the second power supply line PL2 and the first connection point P1.

The first switch S1 controls the current flowing between the first connection point P1 and the second connection point P2 to be in a conductive state or a non-conductive state.
The second switch S2 controls the current flowing between the first connection point P1 and the third connection point P3 to a conductive state or a non-conductive state.
The first switch S1 and the second switch S2 may be, for example, a field effect transistor (FET). When the first switch S1 and the second switch S2 are FETs, the control unit 50 controls the gate voltage of the first switch S1 and the second switch S2, thereby controlling the value of a current flowing between the collector and the emitter.

The second DC power supply 21 has one end connected to the second connection point P2 and the other end connected to the third connection point P3. The second DC power supply 21 may be a power supply with a unidirectional power flow such as a solar cell, or a power supply with a bidirectional power flow such as a battery. In this embodiment, the second DC power supply 21 can also be replaced with a DC load.

The third switch S3 controls the current flowing between the third connection point P3 and the second power line PL2 to a conductive state or a non-conductive state.
The fourth switch S4 controls the current flowing between the second connection point P2 and the first power line PL1 to a conductive state or a non-conductive state.
The third switch S3 and the fourth switch S4 may be, for example, FETs. When the third switch S3 and the fourth switch S4 are FETs, the control unit 50 controls the gate voltage of the third switch S3 and the fourth switch S4, thereby controlling the value of a current flowing between the collector and the emitter.

The fourth switch S4 may be, for example, a diode. When the fourth switch S4 is a diode, the anode is connected to the second connection point P2 and the cathode is connected to the first power line PL1. In the example shown in FIG. 1, the current may be controlled by using a parasitic diode component of the fourth switch S4, which is an FET.

The control unit 50 controls the conductive states of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the switch 33, the switch 34, the switch 35, and the switch 36 (hereinafter simply referred to as switches). Specifically, the control unit 50 controls the conductive states of the switches so as to exchange power between the first DC power source 11 and the second DC power source 21. The control unit 50 also controls the conductive states of the switches to convert the power stored in at least one of the first DC power source 11 or the second DC power source 21 into single-phase AC power.
Furthermore, when power is exchanged between at least one of the first DC power source 11 and the second DC power source 21 and the input capacitor 40, the control unit 50 controls the conductive state of the switch so that the average voltage Vave of the input capacitor 40 becomes a predetermined value. Here, the predetermined value is a value such that the lower limit voltage of the voltage V3 pulsating at a frequency twice the output voltage of the single-phase inverter circuit 30 is higher than either the voltage V1 of the first DC power source 11 or the voltage V2 of the second DC power source 21.
Furthermore, the control unit 50 converts the DC voltage of the input capacitor 40 into a single-phase system voltage by PWM control. Therefore, a voltage ripple (ΔV) having twice the frequency of the system is generated in the input capacitor 40 by the control of the control unit 50. The voltage ripple is uniquely determined by the capacity of the input capacitor 40 and the load power.

Figure 2 is a diagram showing an example of the voltage fluctuation range across the input capacitor provided in the power supply device according to the first embodiment. The voltage fluctuation range across the input capacitor 40 will be described with reference to the diagram. In the following description, the voltage across the input capacitor 40 will also be referred to as v3. In the diagram, the time change of the voltage V3 is shown with the vertical axis representing voltage and the horizontal axis representing time.

The control unit 50 controls the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 to pulsate the voltage V3 at a frequency twice the power frequency output by the single-phase inverter circuit 30. At this time, the voltage V3 is expressed by the following equation (1).

The voltage fluctuation range ΔV of voltage V3 is expressed using constants in the single-phase inverter circuit 30, so voltage V3 is expressed by the following equation (2).

At this time, even when the voltage value of voltage V3 is the minimum value expressed by the following equation (3), it is set to be greater than the output voltage of the second DC power source 21.

In other words, when the voltage across the input capacitor is V3, the maximum power of the single-phase inverter circuit is P, the frequency of the single-phase inverter circuit is f, and the capacitance of the input capacitor is C, the capacitance C of the input capacitor is set so that the voltage V3 across the input capacitor 40 is greater than the output voltage of the second DC power source 21 even when the voltage V3 across the input capacitor 40 satisfies the above formula (3).

In the above example, an example was described in which the capacitance of the input capacitor 40 controls the voltage V3 across the input capacitor 40 to be greater than the output voltage of the second DC power source 21, but in this embodiment, the voltage V3 may be controlled to be greater than the output voltage of the second DC power source 21 by other methods.

For example, a first voltage detection unit (not shown) detects the voltage V3 across the input capacitor 40, and a second voltage detection unit (not shown) detects the output voltage of the second DC power supply 21. Based on the detected voltage V3 across the input capacitor 40 and the output voltage of the second DC power supply 21, the conductive state of at least one of the first switch S1, the second switch S2, and the third switch S3 may be controlled so that the voltage V3 across the input capacitor 40 is greater than the output voltage of the second DC power supply 21.

[Power transfer between first DC power supply and second DC power supply]
3 is a diagram showing an example of a change in a current value flowing through a reactor over time when the power supply device according to the first embodiment exchanges power between the first DC power supply and the second DC power supply in a discontinuous current mode. With reference to the figure, an example of the exchange of power between the first DC power supply 11 and the second DC power supply 21 in the discontinuous current mode will be described. In the figure, the vertical axis represents the current value flowing through the reactor 12, and the horizontal axis represents the time change.

During _{the D1TSW} period, the control unit 50 controls the first switch S1 to a non-conducting state and the second switch S2 and the third switch S3 to a conducting state. A current flows from the positive terminal of the first DC power supply 11 through the reactor 12 to the negative terminal of the first _DC power supply 11. That is, during the _D1TSW period, the current flowing through the reactor 12 increases.
During the _{D2T SW} period, the control unit 50 controls the second switch S2 to be in a non-conductive state and the first switch S1 and the third switch S3 to be in a conductive state. In addition to the power of the first DC power supply 11, the power stored in the reactor 12 is supplied to the second DC power supply 21. That is, during the _{D2T SW} period, the current flowing through the reactor 12 decreases.

In the discontinuous current mode, there is a period in which the current flowing through the reactor 12 is zero (i.e., _D3TSW ). Specifically, the change over time in the value of the current flowing through the reactor 12 depends on the reactance of _the reactor 12, and therefore an error may occur depending on the reactor 12. Therefore, in the discontinuous current mode, a period in which the current flowing through the reactor 12 is zero is provided to prevent the currents flowing through the _reactor 12 from colliding. Theoretically, the period of _D3TSW may be zero.

By interchanging the period of D ₁ T _SW and the period of D ₂ T _SW , it is possible to supply power from the second DC power supply 21 to the first DC power supply 11 .

The period T _SW may be fixed, or may be changed every period (that is, PFM: frequency modulation).

Figure 4 is a diagram showing an example of the change over time in the value of the current flowing through the reactor when the power supply device according to the first embodiment is used in the current continuous mode to exchange power between the first DC power supply and the second DC power supply. With reference to the figure, an example of the exchange of power between the first DC power supply 11 and the second DC power supply 21 when the current continuous mode is used will be described. In the figure, the vertical axis represents the value of the current flowing through the reactor 12, and the horizontal axis represents the time change.

The continuous current mode differs from the discontinuous current mode described above in that there is no period (i.e., _{D3TSW )} during which the current flowing through the reactor 12 is zero. In the explanation of the discontinuous current mode, the contents already explained may be omitted.

In the continuous current mode, the period _D3TSW is not _provided , so the current flowing through the reactor 12 does not become zero and the current change is small. Therefore, the continuous current mode has the advantage of reducing noise because the current change is small. On the other hand, the discontinuous current mode has the disadvantage of increasing noise because the current change through the reactor 12 is large.

In addition, the continuous current mode requires the detection of the current flowing through the reactor 12, which has the disadvantage of making the control more complex. On the other hand, the discontinuous current mode does not require the detection of the current flowing through the reactor 12, which has the advantage of making the control easier.

In addition, in the continuous current mode, the change in the current flowing through the reactor 12 is small, so there is a disadvantage in that a reactor 12 with a larger reactance must be used to boost the voltage of the first DC power source 11. On the other hand, in the discontinuous current mode, the change in the current flowing through the reactor 12 is large, so there is an advantage in that a reactor 12 with a smaller reactance can be used to boost the voltage of the first DC power source 11.

[Power transfer between the first DC power supply or the second DC power supply and the single-phase inverter]
5 is a diagram showing an example of a change in a current value flowing through a reactor over time when power is exchanged between a first DC power source and a single-phase inverter using the power supply device according to the first embodiment. With reference to the figure, an example of power exchange between the first DC power source 11 and a single-phase inverter circuit 30 will be described. In the figure, the vertical axis represents the current value flowing through the reactor 12, and the horizontal axis represents the time change.

During _{the D1TSW} period, the control unit 50 controls the first switch S1 to a non-conducting state and the second switch S2 and the third switch S3 to a conducting state. A current flows from the positive terminal of the first DC power supply 11 through the reactor 12 to the negative terminal of the first _DC power supply 11. That is, during the _D1TSW period, the current flowing through the reactor 12 increases.
During the _{D2T SW} period, the control unit 50 controls the second switch S2 and the third switch S3 to a non-conducting state and the first switch S1 and the fourth switch S4 to a conducting state. In addition to the power of the first DC power source 11, the power stored in the reactor 12 is supplied to the single-phase inverter circuit 30. That is, during the _{D2T SW} period, the current flowing through the reactor 12 decreases.

During the _{D3T SW} period, the current flowing through the reactor 12 becomes zero. By providing a period during which the current flowing through the reactor 12 becomes zero, it is possible to prevent the currents flowing through the reactor 12 from colliding with each other. Theoretically, the _{D3T SW} period may be zero.

By interchanging the period of D ₂ T _SW and the period of D ₁ T _SW , the current flowing through the reactor 12 becomes negative, and power is supplied from the single-phase inverter circuit 30 to the first DC power source 11 .

During the _{D4T SW} period, the control unit 50 controls the first switch S1 to a non-conducting state and the second switch S2 and the third switch S3 to a conducting state. A current flows from the positive terminal of the first DC power supply 11 through the reactor 12 to the negative terminal of the first DC power supply 11. That is, during the _{D4T SW} period, the current flowing through the reactor 12 increases.
During the _{D5T SW} period, the control unit 50 controls the first switch S1 and the third switch S3 to a non-conducting state and the second switch S2 and the fourth switch S4 to a conducting state. Power from the first DC power source 11, the second DC power source 21, and the power stored in the reactor 12 are supplied to the single-phase inverter circuit 30. That is, during the _{D5T SW} period, the current flowing through the reactor 12 decreases.

During the _{D6T SW} period, the current flowing through the reactor 12 becomes zero. By providing a period during which the current flowing through the reactor 12 becomes zero, it is possible to prevent the currents flowing through the reactor 12 from colliding with each other. Theoretically, the _{D6T SW} period may be zero.

By interchanging the period of D ₄ T _SW and the period of D ₅ T _SW , the current flowing through the reactor 12 becomes negative, and power is supplied from the single-phase inverter circuit 30 and the second DC power supply 21 to the first DC power supply 11 .

The period T _SW may be fixed, or may be changed every period (that is, PFM: frequency modulation).

Figure 6 is a diagram showing an example of the change over time in the value of the current flowing through the reactor when power is exchanged between the second DC power source and the single-phase inverter using the power supply device according to the first embodiment. With reference to the figure, an example of the exchange of power between the second DC power source 21 and the single-phase inverter circuit 30 will be described. In the figure, the vertical axis represents the value of the current flowing through the reactor 12, and the horizontal axis represents the time change.

During _{the D1TSW} period, the control unit 50 controls the first switch S1 to a non-conducting state and the second switch S2 and the third switch S3 to a conducting state. A current flows from the positive terminal of the first DC power supply 11 through the reactor 12 to the negative terminal of the first _DC power supply 11. That is, during the _D1TSW period, the current flowing through the reactor 12 increases.
During the _{D2T SW} period, the control unit 50 controls the second switch S2 and the third switch S3 to a non-conducting state and the first switch S1 and the fourth switch S4 to a conducting state. In addition to the power of the first DC power source 11, the power stored in the reactor 12 is supplied to the single-phase inverter circuit 30. That is, during the _{D2T SW} period, the current flowing through the reactor 12 decreases.
At this time, the first DC power supply 11 discharges the power received from the second DC power supply 21 in the immediately preceding period T _SW .

During the _{D3T SW} period, the current flowing through the reactor 12 becomes zero. By providing a period during which the current flowing through the reactor 12 becomes zero, it is possible to prevent the currents flowing through the reactor 12 from colliding with each other. Theoretically, the _{D3T SW} period may be zero.

During the _{D5T SW} period, the control unit 50 controls the second switch S2 and the fourth switch S4 to a non-conducting state and the first switch S1 and the third switch S3 to a conducting state. While the power of the second DC power source 21 is supplied to the first DC power source 11, power is stored in the reactor 12. That is, during the _{D5T SW} period, a negative current flows in the reactor 12.
During the _{D4T SW} period, the control unit 50 controls the first switch S1 to be in a non-conductive state and the second switch S2 and the third switch S3 to be in a conductive state. The power stored in the reactor 12 is transferred to the first DC power source 11. That is, during the _{D4T SW} period, a positive current flows in the reactor 12.

The _power transfer of the first DC power supply 11 _is determined by the balance between the power transferred during the periods of _D1TSW and _D2TSW and the power transferred during the periods of _D4TSW and _D5TSW . Specifically, when _the power transferred during the periods _{of D1TSW} and _D2TSW is greater than the power transferred during the periods of _D4TSW and _{D5TSW ,} the powering _operation is performed, and when the power transferred during the periods _{of D1TSW} and _D2TSW is less than _the power transferred during the periods of _D4TSW and _{D5TSW , the regenerative operation} is performed. Furthermore, when the power transferred during the periods of D ₁ T _SW and D ₂ T _SW is equal to the power transferred during the periods of D ₄ T _SW and D ₅ T _SW , the first DC power supply 11 does not supply or receive power.

The period T _SW may be fixed, or may be changed every period (that is, PFM: frequency modulation).

Second Embodiment
7 is a circuit diagram showing an example of the circuit configuration of a power supply device according to the second embodiment. With reference to the same figure, an example of the circuit configuration of the power supply device 1A according to the first embodiment will be described. The power supply device 1A is a circuit equivalent to the power supply device 1. In the description of the power supply device 1A, the same components as those of the power supply device 1 are denoted by the same reference numerals, and the description may be omitted.

The power supply device 1A includes a first DC power supply 11A, a reactor 12A, a first switch S1A, a second switch S2A, a third switch S3A, a fourth switch S4A, a second DC power supply 21A, a single-phase inverter circuit 30, an input capacitor 40, and a control unit 50A. The first DC power supply 11A and the reactor 12A are also referred to as the first power supply unit 10A, and the first switch S1A, the second switch S2A, and the second DC power supply 21A are also referred to as the second power supply unit 20A.

The power supply unit 1A includes a first DC power supply 11A instead of the first DC power supply 11, and a reactor 12A instead of the reactor 12. The power supply unit 1A differs from the power supply unit 1 in that the reactor 12A is connected to the negative terminal side of the first DC power supply 11A. The first DC power supply 11A and the reactor 12A are connected in series, with one end connected to the first connection point P1A and the other end connected to the first power supply line PL1. That is, the first DC power supply 11 and the reactor 12 are connected in series between the first power supply line PL1 and the first connection point.

The first switch S1A controls the current flowing between the first connection point P1A and the third connection point P3A to a conductive state or a non-conductive state. The second switch S2A controls the current flowing between the first connection point P1A and the second connection point P2A to a conductive state or a non-conductive state.
The second DC power supply 21A has one end connected to the second connection point P2A and the other end connected to the third connection point P3A.

The third switch S3A controls the current flowing between the first power line PL1A and the second connection point P2A to a conductive or non-conductive state. The fourth switch S4A controls the current flowing between the second power line PL2A and the third connection point P3A. The fourth switch S4A may be, for example, a diode. When the fourth switch S4A is a diode, the anode is connected to the second power line PL2A and the cathode is connected to the third connection point P3A.

The control unit 50A controls the conductive states of the first switch S1A, the second switch S2A, the third switch S3A, the fourth switch S4A, the switch 33, the switch 34, the switch 35, and the switch 36 (hereinafter simply referred to as switches). Specifically, the control unit 50 controls the conductive states of the switches to exchange power between the first DC power source 11A and the second DC power source 21A. In addition, the control unit 50A converts the power stored in at least one of the first DC power source 11A or the second DC power source 21A into single-phase AC power by controlling the conductive states of the switches.

[Summary of the embodiment]
As described above, the power supply device 1 includes the first power supply unit 10, the second power supply unit 20, the single-phase inverter circuit 30, the input capacitor 40, and the control unit 50, and thereby causes the voltage input to the single-phase inverter circuit 30 to pulsate at a frequency twice the frequency output by the single-phase inverter circuit 30. Therefore, according to this embodiment, a small-capacity film capacitor can be used as the input capacitor 40, and therefore the device can be made low-cost and compact.
Furthermore, according to this embodiment, by performing the above-described control, it is possible to reduce elements such as reactance and switching elements that were necessary in the prior art, and therefore it is possible to provide a power supply device 1 that can convert DC power to AC power at low cost. Also, according to this embodiment, it is possible to reduce the size of the device.

In addition, according to this embodiment, the voltage across the input capacitor 40 is greater than the output voltage of the second DC power source 21. In other words, even when the voltage input to the single-phase inverter circuit 30 is at its lowest, it does not fall below the voltage value of the second DC power source 21. Therefore, according to this embodiment, a small-capacity film capacitor can be used as the input capacitor 40, making it possible to reduce the cost and size of the device.

In addition, according to this embodiment, the capacitance of the input capacitor 40 is set so that the voltage across the input capacitor 40 is greater than the output voltage of the second DC power source 21. In other words, according to this embodiment, by setting the capacitor capacitance to an appropriate value, the voltage across the input capacitor 40 does not fall below the output voltage of the second DC power source 21 without the control unit 50 performing complex control. Therefore, according to this embodiment, DC power can be easily converted into AC power.

Furthermore, according to this embodiment, the power supply device 1 includes a first voltage detection unit to detect the voltage across the input capacitor 40, and a second voltage detection unit to detect the output voltage of the second DC power supply 21. The control unit 50 controls each switch so that the voltage across the input capacitor 40 is greater than the output voltage of the second DC power supply 21. Therefore, according to this embodiment, the voltage across the input capacitor 40 will never be less than the output voltage of the second DC power supply 21.

The above describes an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to the above-described embodiment, and includes design modifications and the like that do not deviate from the gist of the present invention.

1...power supply device, 10...first power supply unit, 11...first DC power supply, 12...reactor, 20...second power supply unit, 21...second DC power supply, 30...single-phase inverter circuit, 31...reactor, 32...load, 33, 34, 35, 36...switch, 40...input capacitor, 50...control unit, S1...first switch, S2...second switch, S3...third switch, S4...fourth switch, PL1...first power supply line, PL2...second power supply line, P1...first connection point, P2...second connection point, P3...third connection point, 91...flying capacitor type converter circuit, 92...single-phase inverter circuit

Claims (4)

A single-phase inverter circuit including an H-bridge circuit;
an input capacitor connected between a first power supply line connected to a high potential side of the H-bridge circuit and a second power supply line connected to a low potential side of the H-bridge circuit;
a first power supply unit including a first DC power supply connected in series between the first power supply line or the second power supply line and a first connection point, and a reactor;
a second power supply unit including a first switch that controls a current flowing between the first connection point and the second connection point to a conductive state or a non-conductive state, a second switch that controls a current flowing between the first connection point and a third connection point to a conductive state or a non-conductive state, and a second DC power supply having one end connected to the second connection point and the other end connected to the third connection point;
a third switch that controls a current flowing between the third connection point and the second power line to a conductive state or a non-conductive state, or controls a current flowing between the first power line and the second connection point to a conductive state or a non-conductive state;
a fourth switch that controls a current flowing between the first power supply line and the second connection point to a conductive state or a non-conductive state, or controls a current flowing between the third connection point and the second power supply line to a conductive state or a non-conductive state;
a control unit that pulsates a voltage input to the single-phase inverter circuit at a frequency that is twice the frequency of an output from the single-phase inverter circuit ;
a first voltage detection unit that detects a voltage across the input capacitor;
a second voltage detection unit that detects an output voltage of the second DC power supply;
Equipped with
the control unit controls a conductive state of at least one of the first switch, the second switch, and the third switch based on the acquired voltage across the input capacitor and the output voltage of the second DC power source so that the voltage across the input capacitor is greater than the output voltages of the first DC power source and the second DC power source.
Power supply. 2. The power supply device according to claim 1, wherein the voltage across the input capacitor is greater than the output voltage of both the first DC power supply and the second DC power supply. 3. The power supply device according to claim 1, wherein the fourth switch is a diode having an anode connected to the second connection point and a cathode connected to the first power supply line, or a diode having an anode connected to the second power supply line and a cathode connected to the third connection point. 4. The power supply device according to claim 1, wherein the control unit controls a conductive state of at least one of the first switch, the second switch, and the third switch so that a voltage across the input capacitor becomes larger than an output voltage of either the first DC power supply or the second DC power supply.

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