Power converter

Abstract

A high-efficiency and easily implemented low-noise power converter is provided by soft switching, and the output pulse voltage is generated with a constant rise and fall rate regardless of load or component deviations. A first switching element (S1) is connected between the DC power supply (DC) and the load (2). A second switching element (S2) is connected in parallel with the load (2). One end of an inductor (L1) is connected to the junction of the first and second switching elements (S1, S2). A capacitor and the third and fourth switching elements (S3, S4) are connected such that the voltage at the other end of the inductor (L1) is at the midpoint (Vin / 2) of the DC power supply voltage (Vin). Current is then pre-flowed through the inductor (L1) before the first and second switching elements (S1, S2) are turned on.

Description

Technical Field

[0001] The present invention relates to a low-loss and low-noise power converter capable of providing pulse voltage in a high-voltage and high-frequency manner. Background Technology

[0002] Figure 1 and Figure 2 The circuit structure and operating example of Patent Document 1 are shown. In Patent Document 1, by providing energy to the load 2 via inductor 1, a rectangular wave pulse voltage can be provided to the load 2. At this time, a soft-switching operation is performed when the switching element is turned on, thereby reducing switching losses and relieving stress on the switching element.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-7165 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] exist Figure 1 and Figure 2 In this circuit, because hard switching is implemented when switching elements 3 and 4 are turned off, noise caused by surge voltage and other factors increases. Furthermore, when a pulse voltage is supplied to load 2 at a high frequency, increased switching losses occur.

[0008] In addition, the rise and fall rates of the voltage of load 2 depend on the load constant and the inductance constant of inductor 1, which causes the rise and fall rates to change due to the deviation of the constants.

[0009] In view of the above, the technical challenge is to provide a high-efficiency and easily implemented low-noise power converter by performing soft switching, and to generate output pulse voltage with constant rise and fall rates regardless of load or component deviations.

[0010] Technical solutions for solving technical problems

[0011] The present invention addresses the aforementioned problems by providing a power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source. The converter comprises: a first switching element connected between the DC power source and the load; a second switching element connected in parallel with the load; an inductor, one end of which is connected to the junction of the first and second switching elements; and a capacitor, a third switching element, and a fourth switching element, connected such that the voltage at the other end of the inductor is at the midpoint of the DC power source voltage, wherein current is pre-flowed through the inductor before the first and second switching elements are turned on.

[0012] In another embodiment, the capacitor is characterized by a first capacitor and a second capacitor connected in series between the positive and negative terminals of the DC power supply. This embodiment includes: a second diode whose anode is connected to the junction of the first and second capacitors; a third switching element connected between the cathode of the second diode and the other end of the inductor; a third diode whose cathode is connected to the junction of the first and second capacitors; a fourth switching element connected between the anode of the third diode and the other end of the inductor; a first diode whose anode is connected to the junction of the second and third switching elements and whose cathode is connected to the positive terminal of the DC power supply; and a fourth diode whose cathode is connected to the junction of the third diode and the fourth switching element and whose anode is connected to the negative terminal of the DC power supply.

[0013] Additionally, as an alternative, the capacitor is characterized by being a first capacitor and a second capacitor connected in series between the positive and negative terminals of the DC power supply. This alternative includes: a second diode whose anode is connected to the junction of the first and second capacitors; a third switching element connected between the cathode of the second diode and the other end of the inductor; a third diode whose cathode is connected to the junction of the first and second capacitors; a fourth switching element connected between the anode of the third diode and the other end of the inductor; a first diode whose anode is connected to the junction of the second and third switching elements and whose cathode is connected to the positive terminal of the DC power supply; and a fourth diode whose cathode is connected to the junction of the third diode and the fourth switching element and whose anode is connected to the negative terminal of the DC power supply.

[0014] Additionally, as one embodiment, the capacitors are a first capacitor and a second capacitor connected in series between the positive and negative terminals of the DC power supply. This embodiment includes: a sixth switching element and a third switching element connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; a seventh switching element and a fourth switching element connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; a fifth switching element connected between the connection point of the sixth switching element and the third switching element and the positive terminal of the DC power supply; and an eighth switching element connected between the connection point of the seventh switching element and the fourth switching element and the negative terminal of the DC power supply.

[0015] Additionally, as an alternative, the capacitor is characterized by being a first capacitor and a second capacitor connected in series between the positive and negative terminals of the DC power supply. This alternative includes: a third switching element and a fourth switching element connected in anti-series between the connection point of the first capacitor and the second capacitor and the other end of the inductor; a first diode, the anode of which is connected to the other end of the inductor and the cathode of which is connected to the positive terminal of the DC power supply; and a second diode, the cathode of which is connected to the other end of the inductor and the anode of which is connected to the negative terminal of the DC power supply.

[0016] Additionally, as an alternative, the capacitor is characterized by being a first capacitor and a second capacitor connected in series between the positive and negative terminals of the DC power supply. This alternative includes: a third switching element and a fourth switching element connected in anti-series between the connection point of the first capacitor and the second capacitor and the other end of the inductor; a fifth switching element connected between the other end of the inductor and the positive terminal of the DC power supply; and a sixth switching element connected between the other end of the inductor and the negative terminal of the DC power supply.

[0017] Additionally, as an embodiment, it is characterized by comprising: a third switching element, one end of which is connected to the other end of the inductor; a first diode, the anode of which is connected to the other end of the third switching element, and the cathode of which is connected to the positive terminal of the DC power supply; a second diode, the cathode of which is connected to the other end of the inductor; a fourth switching element, one end of which is connected to the anode of the second diode, and the other end of which is connected to the negative terminal of the DC power supply; and a second capacitor connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element.

[0018] Additionally, as an embodiment, it is characterized by comprising: a first diode, the anode of which is connected to the other end of the inductor; a third switching element, one end of which is connected to the cathode of the first diode and the other end of which is connected to the positive terminal of the DC power supply; a fourth switching element, one end of which is connected to the other end of the inductor; a second diode, the cathode of which is connected to the other end of the fourth switching element and the anode of which is connected to the negative terminal of the DC power supply; and a second capacitor connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element.

[0019] Additionally, as an embodiment, it is characterized by comprising: a third switching element, one end of which is connected to the other end of the inductor; a fifth switching element, one end of which is connected to the other end of the third switching element, and the other end of which is connected to the positive terminal of the DC power supply; a sixth switching element, one end of which is connected to the other end of the inductor; a fourth switching element, one end of which is connected to the other end of the sixth switching element, and the other end of which is connected to the negative terminal of the DC power supply; and a second capacitor connected between the connection point of the fifth and third switching elements and the connection point of the sixth and fourth switching elements.

[0020] In addition, as a method, the inductance of the inductor is characterized by satisfying the condition of the following equation (9).

[0021] [Mathematical Expression 9]

[0022] ...(9)

[0023] L: Inductance value of the inductor

[0024] t c＋ : Set as the target maximum value for the rise and fall times of the load voltage.

[0025] C min : The minimum value of the electrostatic capacitance of the load.

[0026] In addition, as a method, it is characterized in that, before the first switching element and the second switching element are turned on, the current is allowed to flow through the inductor during a pre-current flow period that satisfies the following condition (5).

[0027] [Mathematical Expression 5]

[0028] ...(5)

[0029] T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current period.

[0030] L: Inductance value of the inductor

[0031] C: Static capacitance of the load

[0032] R L The equivalent series resistance component of an inductor.

[0033] In addition, as a method, it is characterized in that the rise time and fall time of the load voltage are set to satisfy the following formula (6).

[0034] [Mathematical Expression 6]

[0035] ... (6)

[0036] t c : Set as the rise and fall time of the load voltage

[0037] L: Inductance value of the inductor

[0038] C: Static capacitance of the load

[0039] T SU The inductor is pre-circulated before the first and second switching elements are turned on.

[0040] In addition, as a method, it is characterized in that the current is allowed to flow through the inductor for a pre-current flow period before the first switching element and the second switching element are turned on, and the rise and fall times of the load voltage are set to satisfy the following equation (7).

[0041] [Mathematical Expression 7]

[0042] ... (7)

[0043] T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current period.

[0044] t c : Set as the rise and fall times of the load voltage.

[0045] Invention Effects

[0046] According to the present invention, a high-efficiency and easily implemented low-noise power converter can be provided by performing soft switching, and an output pulse voltage can be generated with a constant rise and fall rate regardless of load or component deviation. Attached Figure Description

[0047] Figure 1This is a diagram showing the circuit structure and working example of Patent Document 1 (Example 2).

[0048] Figure 2 This is a diagram showing the circuit structure and working example of Patent Document 1 (Example 1).

[0049] Figure 3 This is a basic structural diagram of the output pulse generation circuit (power converter) in Implementation Method 1.

[0050] Figure 4 This is a basic working diagram of the output pulse generation circuit (power converter) in Implementation Method 1.

[0051] Figure 5 This is a diagram illustrating an example of soft switching operation.

[0052] Figure 6 This is a basic structural diagram of the output pulse generation circuit (power converter) in Implementation Method 2.

[0053] Figure 7 This is the basic working diagram of the output pulse generation circuit (power converter) in Implementation Method 2.

[0054] Figure 8 This is a basic structural diagram of the output pulse generation circuit (power converter) in Implementation Method 3.

[0055] Figure 9 This is the basic working diagram of the output pulse generation circuit (power converter) in Implementation Method 3.

[0056] Figure Labels

[0057] DC: Direct current power supply

[0058] C1, C2: Capacitor 1 and Capacitor 2

[0059] S1~S4: Switching elements numbered 1 to 4

[0060] D1~D4: Diodes 1 to 4

[0061] L1: Inductor

[0062] 2: Load. Detailed Implementation

[0063] The following is based on Figures 3-9 The embodiments 1 to 3 of the power converter of the present invention will be described in detail below.

[0064] [Implementation Method 1]

[0065] Figure 3 The basic circuit of the power converter (output pulse generation circuit) of Embodiment 1 is shown. Figure 4 The basic operating waveforms of the power converter (output pulse generation circuit) are shown. It is assumed here that load 2 is capacitive. Figure 3 The diagram schematically illustrates load 2, for example, a CR series circuit or a CR parallel circuit including resistive and capacitive components. Figure 3 In the circuit, power is supplied from DC power supply DC to load 2, so that the power of load 2 is returned to DC power supply DC.

[0066] like Figure 3 As shown, a first capacitor C1 and a second capacitor C2 are connected in series between the positive and negative terminals of the DC power supply DC. Additionally, a first switching element S1 and a second switching element S2 are connected in series between the positive and negative terminals of the DC power supply DC. A load 2 is connected between the connection point of the first and second switching elements S1 and S2 and the negative terminal of the DC power supply DC. That is, the first switching element S1 is connected between the DC power supply DC and the load 2, and the second switching element S2 is connected in parallel with the load 2.

[0067] One end of inductor L1 is connected to the connection point of the first and second switching elements S1 and S2. The anode of the second diode D2 is connected to the connection point of the first capacitor and the second capacitors C1 and C2. A third switching element is connected between the cathode of the second diode D2 and the other end of inductor L1.

[0068] Additionally, the cathode of the third diode D3 is connected at the connection point of the first capacitor and the second capacitors C1 and C2. A fourth switching element S4 is connected between the anode of the third diode D3 and the other end of the inductor L1.

[0069] The anode of the first diode D1 is connected at the junction of the second diode D2 and the third switching element S3. The cathode of the first diode D1 is connected to the positive terminal of the DC power supply DC. The cathode of the fourth diode D4 is connected at the junction of the third diode D3 and the fourth switching element S4. The anode of the fourth diode D4 is connected to the negative terminal of the DC power supply DC. In this way, the first capacitor, the second capacitors C1 and C2, and the third and fourth switching elements S3 and S4 are connected such that the voltage across the other end of the inductor L1 is at the midpoint of the DC power supply voltage Vin, Vin / 2.

[0070] The voltage of the DC power supply is Vin, the voltage of the first capacitor and the second capacitors C1 and C2 is Vin / 2, and the current flowing through the inductor L1 is IL1.

[0071] exist Figure 3 In the circuit, the energy stored in the inductor L1 is used to charge and discharge the voltage of the load 2, and the first and second switching elements S1 and S2 are used to maintain the voltage to achieve a rectangular wave output voltage.

[0072] The amount of energy stored in inductor L1 (peak current) can be controlled by the ON time of the third and fourth switching elements S3 and S4. This energy level is used to control the dv / dt of the output pulse voltage. Adjusting the ON time of the third and fourth switching elements S3 and S4 according to the deviation of the load 2 and the inductor controls the energy level (peak current), thereby controlling the deviation of the output pulse voltage's dv / dt.

[0073] Next, the conditions for a soft switch to be activated will be explained. Figure 3 The circuit can achieve soft switching when the following conditions are met. Assuming load 2 is a pure capacitor with electrostatic capacitance C, then the energy of the load, 1 / 2Cv, can be used as a basis for calculation. o 2 The energy 1 / 2Li of the inductor L1 with inductance value L is... pk 2 The relationship is derived from equation (1). According to equation (1), the current flowing through inductor L1 is i. pk The above steps will enable soft switching.

[0074] [Mathematical Expression 1]

[0075] ...(1)

[0076] Furthermore, if the energy consumption of the equivalent series resistance component of inductor L1 and the resistance component of load 2 in the circuit is also taken into account, then the inequality in equation (1) should preferably have a larger range than the equality.

[0077] Here, when the charging time of load 2 is short enough, the current when the load voltage rises is the peak current value, which roughly has the relationship of equation (2) and equation (3).

[0078] [Mathematical Expression 2]

[0079] ...(2)

[0080] [Mathematical Expression 3]

[0081] ...(3)

[0082] t SU During the inductor's pre-current period, the period during which the third and fourth switching elements S3 and S4 are driven before the first and second switching elements S1 and S2.

[0083] R L : The equivalent series resistance component of inductor L1.

[0084] Therefore, while assuming the current value of load 2, we also need to consider the time t required for load 2 to rise / fall.C The relationship between them is roughly the same as that in equation (4). Furthermore, equation (4) assumes that the inductance value L is sufficiently large and that it is a constant current source.

[0085] [Mathematical Expression 4]

[0086] ... (4)

[0087] Therefore, when implementing the invention described in Embodiment 1 more preferably, the required relationship is shown in equations (5) to (7). That is, before the first switching element S1 or the second switching element S2 is turned on, the third switching element S3 or the fourth switching element S4 needs to be kept on for a duration of more than twice the rise time / fall time tc.

[0088] [Mathematical Expression 5]

[0089] ...(5)

[0090] [Mathematical Expression 6]

[0091] ... (6)

[0092] [Mathematical Expression 7]

[0093] ... (7)

[0094] Furthermore, in contrast to the above relationship, in the case of Patent Document 1, the inductance value L of inductor L1 is determined by the envisioned electrostatic capacitance C over time t. C The target value is determined by this. However, time t C Unadjustable; when the electrostatic capacitance C increases or decreases relative to the intended value, time t... C It will change accordingly.

[0095] On the other hand, in the invention described in Embodiment 1, the lower limit of the inductance value L is based on the minimum value C of the envisioned electrostatic capacitance C. min and time t C Target maximum value t C＋ The upper limit of the inductance value L is determined based on the set inductance pre-current period t. SU The minimum value t SU— And the maximum value of the electrostatic capacitance C max It is determined by, as shown in equation (8).

[0096] [Mathematical Expression 8]

[0097] ... (8)

[0098] Here, during the inductor pre-circulation period tSU The minimum value t SU— It needs to be greater than 2√(C) max / C min )t c＋ In this case, √(C) max / C min ) > 1, therefore t SU >2t C＋ >2t C This also holds true, conforming to equation (7). Subsequently, even if the electrostatic capacitance C changes, time t C It is also possible to prepare the inductor for the current flow period t SU To adjust.

[0099] Furthermore, although the upper and lower limits of the inductance value L of inductor L1 are shown in equation (8), an inductor L1 that satisfies the condition of equation (9) which only shows the lower limit of the inductance value L can also be selected.

[0100] [Mathematical Expression 9]

[0101] ...(9)

[0102] like Figure 4 As shown, the work sequence can be divided into the following 8 steps (1) to (8).

[0103] (1) During the preparation period for the rise of the load voltage: while keeping the second switching element S2 on, the third switching element S3 is turned on to store energy in the inductor L1. At this time, iL > 0.

[0104] (2) During the rise of the load voltage: While keeping the third switching element S3 on, the second switching element S2 is turned off. The energy of the inductor L1 is used to make the current flow through the third switching element S3, causing the load voltage to rise. When the second switching element S2 is turned off, the load voltage is zero. Therefore, the second switching element S2 achieves zero-voltage switching.

[0105] (3) During the voltage holding period: While keeping the third switching element S3 on, the first switching element S1 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes voltage Vin, and the connection point of the third and fourth switching elements S3 and S4 of inductor L1 becomes voltage Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0106] (4) During the voltage holding period: While keeping the first switching element S1 on, the third switching element S3 is turned off. At this time, the current of the inductor L1 is 0, so the third switching element S3 achieves zero current switching.

[0107] (5) During the preparation period for the load voltage drop: While keeping the first switching element S1 on, the fourth switching element S4 is turned on to store reverse energy in the inductor L1. At this time, iL < 0.

[0108] (6) During the load voltage drop: While keeping the fourth switching element S4 on, the first switching element S1 is turned off, and the current flows through the fourth switching element S4 using the energy of the inductor L1, causing the load voltage to drop.

[0109] (7) During voltage holding period: While keeping the fourth switching element S4 on, the second switching element S2 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes voltage 0, and the connection point of the third and fourth switching elements S3 and S4 of inductor L1 becomes voltage Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0110] (8) During voltage holding period: While keeping the second switching element S2 on, the fourth switching element S4 is turned off. At this time, the current of inductor L1 is 0, so the fourth switching element S4 performs zero-current switching.

[0111] In addition, Figure 4 In the process, at the points where iL1 is at its maximum and minimum, the slope changes discontinuously (the maximum and minimum points form an angle), but when the capacitance of load 2 is taken into account, the slope changes continuously (the maximum and minimum points become smooth). Furthermore, when the third and fourth switching elements S3 and S4 are conducting and the potential difference between the first and second switching elements S1 and S2 is zero, the first and second switching elements S1 and S2 switch. Therefore, the potential difference of inductor L1 does not change abruptly due to the presence of the first capacitor and the second capacitors C1 and C2, etc. Therefore, the slope of IL1 does not become discontinuous at the boundary.

[0112] Regarding the rising / falling waveform of the load voltage Vout, it is more like... Figure 4 Such a straight line is not strictly speaking an S-shaped waveform, but if ipk is set large enough, it will be roughly a straight line.

[0113] During the period when the load voltage Vout decreases (6), the charging energy in the capacitive component of load 2 is essentially released, so the energy reduction due to losses is faster; if there were no losses, it would remain the same. Therefore, regardless of the resistive component of load 2, such as Figure 4 As shown, the periods (2) and (6) of the load voltage Vout are approximately equal.

[0114] Next, Figure 5 An example of soft switching operation is shown. Figure 5Solid lines represent the voltages Vds_s1 to Vds_s4 of the first to fourth switching elements S1 to S4, and dashed lines represent the currents ids_s1 to ids_s4. Vout is the load voltage.

[0115] Figure 5 (a) shows an example of the operation of the first switching element S1. Since the first switching element S1 is connected in series with the load 2, the applied voltage is the voltage Vin of the DC power supply minus the load voltage Vout. The timing of the first switching element S1 turning on is the instant during the alternation of steps (2) and (3) above, until the load voltage Vout rises to Vin. Therefore, at the timing of the first switching element S1 turning on, the applied voltage of the first switching element S1 is 0, and the voltage change rate of the load 2 is slower than the current cut-off rate of the switching element, thus achieving zero-voltage switching.

[0116] On the other hand, the timing of the first switching element S1 being turned off is the instant at which steps (5) and (6) above alternate, and the load voltage Vout is Vin. Therefore, at the timing of the first switching element S1 being turned off, the applied voltage of the first switching element S1 is 0, and the voltage change rate of the load 2 is slower than the current cut-off rate of the switching element, thus achieving zero-voltage switching.

[0117] Figure 5 (b) shows an example of the operation of the second switching element S2. Since the second switching element S2 is connected in parallel with the load 2, it is applied with the same value as the load voltage Vout. The timing of the second switching element S2 opening is the instant at which steps (1) and (2) above alternate, at which point the load voltage is 0. Therefore, at the timing of the second switching element S2 opening, the applied voltage of the second switching element S2 is 0, achieving zero-voltage switching.

[0118] On the other hand, the timing of the second switching element S2 turning on is the instant at which steps (6) and (7) alternate, and the load voltage Vout is 0. Therefore, at the timing of the second switching element S2 turning on, the applied voltage of the second switching element S2 is 0, realizing zero-voltage switching.

[0119] Figure 5 (c) shows an example of the operation of the third switching element S3. The third switching element S3 is a component connected to the neutral point (the intermediate potential of the DC power supply), and therefore Vin / 2 is applied, causing a portion of the current IL1 flowing through the inductor L1 (IL1 > 0). The timing of the third switching element S3 turning on is the instant at which steps (8) and (1) above alternate, at which point the current IL1 through the inductor L1 is 0. Therefore, since the current at the timing of the third switching element S3 turning on is 0, the voltage change rate of the inductor L1 is slower than the voltage change rate of the switching element, thus achieving zero-current switching.

[0120] The timing of the third switching element S3 being turned off is the instant at which steps (3) and (4) above alternate, and the current IL1 through inductor L1 is 0. Therefore, the current at the timing of the third switching element S3 being turned off is 0, and the voltage change rate of inductor L1 is slower than the voltage change rate of the switching element, thus achieving zero-current switching.

[0121] Figure 5 (d) illustrates an example of the operation of the fourth switching element S4. The fourth switching element S4 is connected to the neutral point (the intermediate potential of the DC power supply), and therefore Vin / 2 is applied, causing a portion of the current IL1 flowing through the inductor L1 (IL1 < 0). The timing of the fourth switching element S4 turning on is the instant at which steps (4) and (5) above alternate, at which point the current IL1 through the inductor L1 is 0. Therefore, since the current at the timing of the fourth switching element S4 turning on is 0, and the voltage change rate of the inductor L1 is slower than the voltage change rate of the switching element, zero-current switching is achieved.

[0122] The timing of the fourth switching element S4 being turned off is the instant at which steps (7) and (8) above alternate, and the current IL1 through inductor L1 is 0. Therefore, the current at the timing of the fourth switching element S4 being turned off is 0, and the voltage change rate of inductor L1 is slower than the voltage change rate of the switching element, thus achieving zero-current switching.

[0123] The voltage of capacitor C1 and capacitor C2 can be controlled by the average value of the current flowing into and out of the connection point (neutral point) of capacitors C1 and C2. Under soft-switching conditions, all current flowing at the neutral point passes through inductor L1; therefore, the neutral point voltage can also be controlled by controlling the average value of the current in inductor L1. The average value of the current in inductor L1 can be controlled by changing the ratio of period (1) to period (5). Theoretically, by controlling the average value to 0, the change in neutral point potential can be reduced to 0.

[0124] If IL1 is positive and negative symmetrical, the neutral point potential will not change. However, when load 2 contains a resistive component, the charging current and discharging current are not necessarily positive and negative symmetrical. In this case, IL1 must be adjusted. When IL1 is positive, the neutral point potential decreases; when IL1 is negative, the neutral point potential increases. This is used to adjust the voltage, i.e., the neutral point potential, of the first capacitor C1 and the second capacitor C2.

[0125] Furthermore, the average current when the first switching element S1 is turned on is positive in accordance with the amount supplied to the load 2. Consequently, it shifts positive in accordance with the amount that raises the neutral point potential. Since no current is supplied to the load 2, the average current when the second switching element S2 is turned on is 0, except for the amount that shifts positive in accordance with the amount that lowers the neutral point potential.

[0126] By operating in the manner described above, the first to fourth switching elements S1 to S4 can perform soft switching while maintaining a constant dv / dt output pulse voltage, unaffected by deviations in components or load.

[0127] Furthermore, although the detailed description of Embodiment 1 is omitted, the same structure can also be achieved. Figure 3 The same operation. Furthermore, the orientation of the switching elements and diodes is set to be the same as... Figure 3 Same.

[0128] • Replace the 3rd and 4th switching elements S3 and S4 with the 2nd and 3rd diodes D2 and D3, and replace the 2nd and 3rd diodes D2 and D3 with the 3rd and 4th switching elements S3 and S4.

[0129] • A structure in which diodes D1 to D4 (numbers 1 to 4) are replaced with switching elements D5 to D8.

[0130] As described above, according to Embodiment 1, hard switching is not performed. Furthermore, by adjusting the on / off periods of each switching element, the rise and fall rates of the load voltage can be controlled. Therefore, output pulses can be generated efficiently and with low noise, unaffected by load or component deviations, at a constant rise and fall rate. Maintaining a constant rise and fall rate helps improve the output voltage accuracy of the power converter.

[0131] [Implementation Method 2]

[0132] Figure 6 The basic circuit of the power converter (output pulse generation circuit) of Embodiment 2 is shown. Figure 7 The basic operating waveforms of the power converter (output pulse generation circuit) are shown. It is assumed here that load 2 is capacitive. Figure 6 The diagram schematically illustrates load 2, for example, a CR series circuit or a CR parallel circuit including resistive and capacitive components. Figure 6 In the circuit, power is supplied from DC power supply DC to load 2, so that the power of load 2 is returned to DC power supply DC.

[0133] like Figure 6 As shown, a first capacitor C1 and a second capacitor C2 are connected in series between the positive and negative terminals of the DC power supply DC. Additionally, a first switching element S1 and a second switching element S2 are connected in series between the positive and negative terminals of the DC power supply DC. A load 2 is connected between the connection point of the first and second switching elements S1 and S2 and the negative terminal of the DC power supply DC. That is, the first switching element S1 is connected between the DC power supply DC and the load 2, and the second switching element S2 is connected in parallel with the load 2.

[0134] One end of inductor L1 is connected to the connection point of the first and second switching elements. The third and fourth switching elements S3 and S4 are connected in anti-series between the connection point of the first and second capacitors C1 and C2 and the other end of inductor L1. The anode of the first diode D1 is connected to the other end of inductor L1. The cathode of the first diode D1 is connected to the positive terminal of the DC power supply DC. The cathode of the second diode D2 is connected to the other end of inductor L1. The anode of the second diode D2 is connected to the negative terminal of the DC power supply DC. In this way, the first and second capacitors C1 and C2 and the third and fourth switching elements S3 and S4 are connected such that the voltage at the other end of inductor L1 is at the midpoint of the DC power supply voltage Vin, Vin / 2.

[0135] Let the voltage of the DC power supply be Vin, the voltage of the first capacitor and the second capacitors C1 and C2 be Vin / 2, and the current flowing through the inductor L1 be IL1.

[0136] exist Figure 6 In the circuit, the energy stored in the inductor L1 is used to charge and discharge the voltage of the load 2, and the voltage is maintained by the first and second switching elements S1 and S2, thereby achieving a rectangular wave output voltage.

[0137] The amount of energy stored in inductor L1 can be controlled by the conduction time of the third and fourth switching elements S3 and S4, and the amount of this energy can be used to control the dv / dt of the output pulse voltage.

[0138] The conduction times of the third and fourth switching elements S3 and S4 are adjusted according to the load and inductance deviations, thereby controlling the dv / dt deviation. Furthermore, all switching elements are soft-switched during turn-off, thus achieving lower losses and reduced noise compared to Patent Document 1.

[0139] like Figure 7 As shown, the work sequence can be divided into the following 8 steps (1) to (8).

[0140] (1) During the preparation period for the rise of the load voltage: while keeping the second switching element S2 on, the third switching element S3 is turned on to store energy in the inductor L1. At this time, iL > 0.

[0141] (2) During the rise of the load voltage: When the third switching element S3 is kept on, the second switching element S2 is turned off. Using the energy of the inductor L1, the current flows through the third switching element S3, causing the load voltage Vout to rise. When the second switching element S2 is turned off, the load voltage Vout is zero, thus achieving zero-voltage switching.

[0142] (3) During the voltage holding period: While keeping the third switching element S3 on, the first switching element S1 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes the voltage Vin, and the fourth switching element S4 side of inductor L1 becomes the voltage Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0143] (4) During voltage holding period: While keeping the first switching element S1 on, the third switching element S3 is turned off. The current in the inductor L1 becomes 0, so the third switching element S3 performs zero-current switching.

[0144] (5) During the preparation period for the load voltage drop: While keeping the first switching element S1 on, the fourth switching element S4 is turned on to store reverse energy in the inductor L1. At this time, iL < 0.

[0145] (6) During the load voltage drop: While keeping the fourth switching element S4 on, the first switching element S1 is turned off, and the load voltage Vout is dropped by using the energy of the inductor L1.

[0146] (7) During voltage holding period: While keeping the fourth switching element S4 on, the second switching element S2 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes voltage 0, and the fourth switching element S4 of inductor L1 becomes voltage Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0147] (8) During voltage holding period: While keeping the second switching element S2 on, the fourth switching element S4 is turned off. The current in the inductor L1 becomes 0, so the fourth switching element S4 performs zero-current switching.

[0148] Due to the operation during soft switching and Figure 5 The same applies, so the explanation is omitted. The voltages of the first capacitor C1 and the second capacitor C2 are also the same as in Embodiment 1.

[0149] By operating in the manner described above, it is possible to output a constant dv / dt pulse voltage while enabling each switching element to perform soft switching, unaffected by deviations in components or load. That is, the same effect as in Embodiment 1 is achieved.

[0150] Furthermore, although a detailed description of Embodiment 2 is omitted, it is possible to achieve the same result even with the following structure. Figure 6 The same operation. The orientation of the switching element is the same as... Figure 6 Same.

[0151] • Replace the first and second diodes D1 and D2 with the fifth and sixth switching elements.

[0152] [Implementation Method 3]

[0153] Figure 8 The basic circuit of the power converter (output pulse generation circuit) of Embodiment 3 is shown. Figure 9 The basic operating waveforms of the power converter (output pulse generation circuit) are shown. It is assumed here that load 2 is capacitive. Figure 8 The diagram schematically illustrates load 2, for example, a CR series circuit or a CR parallel circuit including resistive and capacitive components. Figure 8 In the circuit, power is supplied from DC power supply DC to load 2, so that the power of load 2 is returned to DC power supply DC.

[0154] like Figure 8 As shown, a first capacitor C1 is connected between the positive and negative terminals of the DC power supply DC. Additionally, a first switching element S1 and a second switching element S2 are connected in series between the positive and negative terminals of the DC power supply DC. A load 2 is connected between the connection point of the first and second switching elements S1 and S2 and the negative terminal of the DC power supply DC. That is, the first switching element S1 is connected between the DC power supply DC and the load 2, and the second switching element S2 is connected in parallel with the load 2.

[0155] One end of inductor L1 is connected to the connection point of the first and second switching elements. One end of the third switching element S3 is connected to the other end of inductor L1. The anode of the first diode D1 is connected to the other end of the third switching element S3. The cathode of the first diode D1 is connected to the positive terminal of the DC power supply.

[0156] The cathode of the second diode D2 is connected to the other end of the inductor L1. One end of the fourth switching element S4 is connected to the anode of the second diode D2. The other end of the fourth switching element S4 is connected to the negative terminal of the DC power supply.

[0157] A second capacitor (flying capacitor) C2 is connected between the connection point of the first diode D1 and the third switching element S3 and the connection point of the second diode D2 and the fourth switching element S4. In this way, the first and second capacitors C1 and C2, and the third and fourth switching elements S3 and S4, are connected such that the voltage at the other end of the inductor L1 is at the midpoint Vin / 2 of the DC power supply voltage Vin.

[0158] Let the voltage of the DC power supply DC be Vin, the voltage of the first capacitor C1 be Vin, the voltage of the second capacitor (flying capacitor) C2 be Vin / 2, and the current flowing through the inductor L1 be IL1.

[0159] exist Figure 8In the circuit, the energy stored in the inductor L1 is used to charge and discharge the voltage of the load 2, and the voltage is maintained by the first and second switching elements S1 and S2, thereby realizing a rectangular wave output voltage.

[0160] The amount of energy stored in inductor L1 can be controlled by adjusting the conduction time of the third and fourth switching elements S3 and S4, and the output pulse voltage dv / dt can be controlled based on the amount of energy. By adjusting the conduction time of the third and fourth switching elements S3 and S4 according to the deviation of the load 2 and the inductance, the deviation of dv / dt can be controlled.

[0161] Furthermore, all switching elements are soft-switched during shutdown, thus achieving lower losses and reduced noise compared to Patent Document 1.

[0162] like Figure 9 As shown, the work sequence can be divided into the following 8 steps (1) to (8).

[0163] (1) During the preparation period for the rise of the load voltage: while keeping the second switching element S2 on, the third switching element S3 is turned on to store energy in the inductor L1. At this time, iL > 0.

[0164] (2) During the rise of the load voltage: While keeping the third switching element S3 on, the second switching element S2 is turned off, and the energy of the inductor L1 is used to make the current flow through the third switching element S3, causing the load voltage Vout to rise. When the second switching element S2 is turned off, the load voltage Vout is zero, thus achieving zero-voltage switching.

[0165] (3) During the voltage holding period: When the third switching element S3 is kept on, the first switching element S1 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes the voltage Vin, and the third switching element S3 of inductor L1 becomes Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0166] (4) During voltage holding period: While keeping the first switching element S1 on, the third switching element S3 is turned off. The current in the inductor L1 becomes 0, so the third switching element S3 performs zero-current switching.

[0167] (5) During the preparation period for the load voltage drop: While keeping the first switching element S1 on, the fourth switching element S4 is turned on to store reverse energy in the inductor L1. At this time, iL < 0.

[0168] (6) During the load voltage drop: While the fourth switching element S4 is on, the first switching element S1 is turned off, and the load voltage Vout is dropped by the energy of the inductor L1.

[0169] (7) During voltage holding period: While keeping the fourth switching element S4 on, the second switching element S2 is turned on. The connection point of the first and second switching elements S1 and S2 of inductor L1 becomes voltage 0, and the third switching element S3 of inductor L1 becomes voltage Vin / 2. Therefore, Vin / 2 is applied to inductor L1, and the current decreases.

[0170] (8) During voltage holding period: When the second switching element S2 is kept on, the fourth switching element S4 is turned off. When the fourth switching element S4 is turned off, the current of the inductor L1 becomes 0, so the fourth switching element S4 performs zero current switching.

[0171] Due to the operation during soft switching and Figure 5 They are the same, so they are omitted.

[0172] The voltage of the second capacitor (flying capacitor) C2 can be controlled by the average current of the inductor L1. The average current of the inductor L1 is the same as in embodiments 1 and 2.

[0173] By operating in the manner described above, it is possible to output a constant dv / dt pulse voltage while enabling each switching element to perform soft switching, unaffected by deviations in components or load. That is, the same effect as in embodiments 1 and 2 is achieved.

[0174] Furthermore, although the detailed description of Embodiment 3 is omitted, the same structure can be achieved even with the following description. Figure 8 The same operation. The orientation of the diode and switching element is set to be the same as... Figure 8 Same.

[0175] • Replace the 3rd and 4th switching elements S3 and S4 with the 1st and 2nd diodes D1 and D2, and replace the 1st and 2nd diodes D1 and D2 with the 3rd and 4th switching elements S3 and S4.

[0176] • Replace the first and second diodes D1 and D2 with the fifth and sixth switching elements.

[0177] The above description only details specific examples. However, it is obvious to those skilled in the art that various modifications and variations can be made within the scope of the technical concept of the present invention, and such modifications and variations naturally fall within the scope of the claims. Claims (as amended under Article 19 of the Treaty) 1. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; The first capacitor is connected between the positive and negative terminals of the DC power supply; The third switching element has one end connected to the other end of the inductor; The first diode has its anode connected to the other end of the third switching element and its cathode connected to the positive terminal of the DC power supply. The cathode of the second diode is connected to the other end of the inductor; A fourth switching element, one end of which is connected to the anode of the second diode, and the other end of which is connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element. The first capacitor, the second capacitor, the third switch element, and the fourth switch element are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Before the first and second switching elements are turned on, current is allowed to flow through the inductor in advance. 2. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; The first capacitor is connected between the positive and negative terminals of the DC power supply; The first diode has its anode connected to the other end of the inductor; The third switching element has one end connected to the cathode of the first diode and the other end connected to the positive terminal of the DC power supply. The fourth switching element has one end connected to the other end of the inductor; The second diode has its cathode connected to the other end of the fourth switching element, and its anode connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element. The first capacitor, the second capacitor, the third switch element, and the fourth switch element are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Before the first and second switching elements are turned on, current is allowed to flow through the inductor in advance. 3. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; The first capacitor is connected between the positive and negative terminals of the DC power supply; The third switching element has one end connected to the other end of the inductor; The fifth switching element has one end connected to the other end of the third switching element and the other end connected to the positive terminal of the DC power supply. The sixth switching element has one end connected to the other end of the inductor; A fourth switching element, one end of which is connected to the other end of the sixth switching element, and the other end of which is connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the fifth and third switching elements and the connection point of the sixth and fourth switching elements. The first capacitor, the second capacitor, the third switch element, and the fourth switch element are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Before the first and second switching elements are turned on, current is allowed to flow through the inductor in advance. 4. The power converter according to any one of claims 1 to 3, characterized in that, The inductance of the inductor satisfies the following condition (9): [Mathematical Expression 9] ...(9) L: Inductance value of the inductor t c＋ : Set as the target maximum value for the rise and fall times of the load voltage. C min : The minimum value of the electrostatic capacitance of the load. 5. The power converter according to any one of claims 1 to 3, characterized in that, Before the first and second switching elements are turned on, the current is allowed to flow through the inductor during a pre-current flow period that satisfies the following condition (5): [Mathematical Expression 5] ...(5) T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. L: Inductance value of the inductor C: Static capacitance of the load. R L The equivalent series resistance component of an inductor. 6. The power converter according to any one of claims 1 to 3, characterized in that, The rise and fall times of the load voltage are set to satisfy the following equation (6): [Mathematical Expression 6] ... (6) t c : Set as the rise and fall times of the load voltage. L: Inductance value of the inductor C: Static capacitance of the load. T SU The inductor is pre-circulated before the first and second switching elements are turned on. 7. The power converter according to any one of claims 1 to 3, characterized in that, Before the first and second switching elements are turned on, the pre-current flow period through the inductor and the rise and fall times set as the load voltage satisfy the following condition (7): [Mathematical Expression 7] ... (7) T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. t c : Set as the rise and fall times of the load voltage. 8. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; and The capacitor, along with the third and fourth switching elements, are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Specifically, before the first and second switching elements are turned on, current is allowed to flow through the inductor beforehand. The inductance of the inductor satisfies the following condition (9): [Mathematical Expression 9] ...(9) L: Inductance value of the inductor t c＋ : Set as the target maximum value for the rise and fall times of the load voltage. C min : The minimum value of the electrostatic capacitance of the load. 9. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; and The capacitor, along with the third and fourth switching elements, are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Specifically, before the first and second switching elements are turned on, current is allowed to flow through the inductor beforehand. Before the first and second switching elements are turned on, the current is allowed to flow through the inductor during a pre-current flow period that satisfies the following condition (5): [Mathematical Expression 5] ...(5) T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. L: Inductance value of the inductor C: Static capacitance of the load. R L The equivalent series resistance component of an inductor. 10. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; and The capacitor, along with the third and fourth switching elements, are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. Specifically, before the first and second switching elements are turned on, current is allowed to flow through the inductor beforehand. Before the first and second switching elements are turned on, the pre-current flow period through the inductor and the rise and fall times set as the load voltage satisfy the following condition (7): [Mathematical Expression 7] ... (7) T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. t c : Set as the rise and fall times of the load voltage. 11. The power converter according to any one of claims 8 to 10, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The anode of the second diode is connected to the junction of the first capacitor and the second capacitor; The third switching element is connected between the cathode of the second diode and the other end of the inductor; The cathode of the third diode is connected to the junction of the first capacitor and the second capacitor; The fourth switching element is connected between the anode of the third diode and the other end of the inductor; The first diode has its anode connected to the junction of the second diode and the third switching element, and its cathode connected to the positive terminal of the DC power supply; and The fourth diode has its cathode connected to the junction of the third diode and the fourth switching element, and its anode connected to the negative terminal of the DC power supply. 12. The power converter according to any one of claims 8 to 10, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third switching element has one end connected to the connection point of the first capacitor and the second capacitor; The second diode has its anode connected to the other end of the third switching element and its cathode connected to the other end of the inductor. The fourth switching element has one end connected to the connection point of the first capacitor and the second capacitor; The third diode has its cathode connected to the other end of the fourth switching element and its anode connected to the other end of the inductor. The first diode has its anode connected to the junction of the second diode and the third switching element, and its cathode connected to the positive terminal of the DC power supply; and The fourth diode has its cathode connected to the junction of the third diode and the fourth switching element, and its anode connected to the negative terminal of the DC power supply. 13. The power converter according to any one of claims 8 to 10, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The sixth switching element and the third switching element are connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; The seventh switching element and the fourth switching element are connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; The fifth switching element is connected between the connection point of the sixth and third switching elements and the positive terminal of the DC power supply; and The 8th switching element is connected between the connection point of the 7th and 4th switching elements and the negative terminal of the DC power supply. 14. The power converter according to any one of claims 8 to 10, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third and fourth switching elements are connected in anti-series between the connection point of the first and second capacitors and the other end of the inductor. The first diode has its anode connected to the other end of the inductor and its cathode connected to the positive terminal of the DC power supply; and The second diode has its cathode connected to the other end of the inductor and its anode connected to the negative terminal of the DC power supply. 15. The power converter according to any one of claims 8 to 10, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third and fourth switching elements are connected in anti-series between the connection point of the first and second capacitors and the other end of the inductor. A fifth switching element is connected between the other end of the inductor and the positive terminal of the DC power supply; and The sixth switching element is connected between the other end of the inductor and the negative terminal of the DC power supply. 16. The power converter according to any one of claims 8 to 10, characterized in that, The rise and fall times of the load voltage are set to satisfy the following equation (6): [Mathematical Expression 6] ... (6) t c : Set as the rise and fall times of the load voltage. L: Inductance value of the inductor C: Static capacitance of the load. T SU The inductor is pre-circulated before the first and second switching elements are turned on.

Claims

1. A power converter capable of supplying power from a DC power source to a load and returning power from the load to the DC power source, characterized in that it comprises: The first switching element is connected between the DC power supply and the load; The second switching element is connected in parallel with the load; An inductor, one end of which is connected to the connection point of the first switching element and the second switching element; and The capacitor, along with the third and fourth switching elements, are connected such that the voltage at the other end of the inductor is at the midpoint of the DC power supply voltage. in, Before the first and second switching elements are turned on, current is allowed to flow through the inductor in advance.

2. The power converter according to claim 1, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The anode of the second diode is connected to the junction of the first capacitor and the second capacitor; The third switching element is connected between the cathode of the second diode and the other end of the inductor; The cathode of the third diode is connected to the junction of the first capacitor and the second capacitor; The fourth switching element is connected between the anode of the third diode and the other end of the inductor; The first diode has its anode connected to the junction of the second diode and the third switching element, and its cathode connected to the positive terminal of the DC power supply; and The fourth diode has its cathode connected to the junction of the third diode and the fourth switching element, and its anode connected to the negative terminal of the DC power supply.

3. The power converter according to claim 1, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third switching element has one end connected to the connection point of the first capacitor and the second capacitor; The second diode has its anode connected to the other end of the third switching element and its cathode connected to the other end of the inductor. The fourth switching element has one end connected to the connection point of the first capacitor and the second capacitor; The third diode has its cathode connected to the other end of the fourth switching element and its anode connected to the other end of the inductor. The first diode has its anode connected to the junction of the second diode and the third switching element, and its cathode connected to the positive terminal of the DC power supply; and The fourth diode has its cathode connected to the junction of the third diode and the fourth switching element, and its anode connected to the negative terminal of the DC power supply.

4. The power converter according to claim 1, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The sixth switching element and the third switching element are connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; The seventh switching element and the fourth switching element are connected between the connection point of the first capacitor and the second capacitor and the other end of the inductor; The fifth switching element is connected between the connection point of the sixth and third switching elements and the positive terminal of the DC power supply; and The 8th switching element is connected between the connection point of the 7th and 4th switching elements and the negative terminal of the DC power supply.

5. The power converter according to claim 1, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third and fourth switching elements are connected in anti-series between the connection point of the first and second capacitors and the other end of the inductor. The first diode has its anode connected to the other end of the inductor and its cathode connected to the positive terminal of the DC power supply; and The second diode has its cathode connected to the other end of the inductor and its anode connected to the negative terminal of the DC power supply.

6. The power converter according to claim 1, characterized in that, The capacitors are the first capacitor and the second capacitor connected in series between the positive and negative terminals of the DC power supply. The power converter includes: The third and fourth switching elements are connected in anti-series between the connection point of the first and second capacitors and the other end of the inductor. The fifth switching element is connected between the other end of the inductor and the positive terminal of the DC power supply; as well as The sixth switching element is connected between the other end of the inductor and the negative terminal of the DC power supply.

7. The power converter according to claim 1, characterized in that, have: The third switching element has one end connected to the other end of the inductor; The first diode has its anode connected to the other end of the third switching element and its cathode connected to the positive terminal of the DC power supply. The cathode of the second diode is connected to the other end of the inductor; The fourth switching element has one end connected to the anode of the second diode and the other end connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element.

8. The power converter according to claim 1, characterized in that, have: The first diode has its anode connected to the other end of the inductor; The third switching element has one end connected to the cathode of the first diode and the other end connected to the positive terminal of the DC power supply. The fourth switching element has one end connected to the other end of the inductor; The second diode has its cathode connected to the other end of the fourth switching element, and its anode connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the first diode and the third switching element and the connection point of the second diode and the fourth switching element.

9. The power converter according to claim 1, characterized in that, have: The third switching element has one end connected to the other end of the inductor; The fifth switching element has one end connected to the other end of the third switching element and the other end connected to the positive terminal of the DC power supply. The sixth switching element has one end connected to the other end of the inductor; The fourth switching element has one end connected to the other end of the sixth switching element, and the other end connected to the negative terminal of the DC power supply; and The second capacitor is connected between the connection point of the fifth and third switching elements and the connection point of the sixth and fourth switching elements.

10. The power converter according to claim 1, characterized in that, The inductance of the inductor satisfies the following condition (9): [Mathematical Expression 9] ……（9） L: Inductance value of the inductor t c＋ : Set as the target maximum value for the rise and fall times of the load voltage. C min : The minimum value of the electrostatic capacitance of the load.

11. The power converter according to claim 1, characterized in that, Before the first and second switching elements are turned on, the current is allowed to flow through the inductor during a pre-current flow period that satisfies the following condition (5): [Mathematical Expression 5] ……（5） T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. L: Inductance value of the inductor C: Static capacitance of the load. R L The equivalent series resistance component of an inductor.

12. The power converter according to claim 1, characterized in that, The rise and fall times of the load voltage are set to satisfy the following equation (6): [Mathematical Expression 6] ……（6） t c : Set as the rise and fall times of the load voltage. L: Inductance value of the inductor C: Static capacitance of the load. T SU The inductor is pre-circulated before the first and second switching elements are turned on.

13. The power converter according to claim 1, characterized in that, Before the first and second switching elements are turned on, the pre-current flow period through the inductor and the rise and fall times set as the load voltage satisfy the following condition (7): [Mathematical Expression 7] ……（7） T SU Before the first and second switching elements are turned on, current is allowed to flow through the inductor during the pre-current flow period. t c : Set as the rise and fall times of the load voltage.

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