Power supply device

Abstract

To easily reduce a voltage to ground generated between elements, without deteriorating filter characteristics.SOLUTION: A class D amplifier 10 includes: a full bridge switching circuit 13 that has a pair of output terminals and that converts DC power to AC power by PWM control; a filter circuit 14A that has inductors L1 to Lm as a first element connected in series and capacitors C1 to Cn as a second element and that has one end connected to one of the output terminals of the full bridge switching circuits 13; and a transformer 15 with one end connected to the other end of the filter circuit 14A and the other end connected to the other output terminal of the full bridge switching circuit 13. In the filter circuit 14A, the first element and the second element are alternately arranged.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a power supply device. [Background technology]

[0002] Conventionally, high-frequency power supplies (also simply called power supplies) that supply high-frequency power to loads such as plasma loads are known. Such high-frequency power supplies, for example, use a Class D amplifier to supply AC power (high-frequency power) to the load by converting a DC voltage to an AC voltage. A Class D amplifier has a voltage conversion circuit that converts a DC voltage into a square wave differential voltage by the switching operation of a switching element. Furthermore, a filter circuit that functions as a resonant circuit, a transformer, etc. are provided after the voltage conversion circuit, and the differential voltage is converted into a sinusoidal voltage and output. The filter circuit generally uses an LC filter that includes an inductor L (coil L) and a capacitor C (capacitor C). The output frequency of the high-frequency power supply is, for example, an industrial RF band (Radio Frequency) frequency such as 13.56 MHz, 27.12 MHz, or 40.68 MHz. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-143861 [Patent Document 2] Japanese Patent Publication No. 2017-054646 [Patent Document 3] Japanese Patent Publication No. 2018-057223 [Overview of the project] [Problems that the invention aims to solve]

[0004] Generally, the characteristics of this LC filter are expressed by the following equation. Q = 2πfL / R pri (R pri (Apparent load resistance value on the primary side)

[0005] In other words, the larger the Q value, the better the filter characteristics, but as shown in the following equation, the voltage applied to the inductor L and capacitor C increases in proportion to the Q value. |V C |=|V L |=Q|V Rpri |

[0006] In this case, the voltage V applied to capacitor C C and the voltage V applied to the inductor L L These two phases cancel each other out and are in a state of mutual cancellation.

[0007] However, the voltage before cancellation is applied to the wiring between the inductor L and the capacitor C. Voltage Q|V Rpri | This voltage is applied directly. Therefore, the voltage between LC and ground increases. Consequently, there was a risk of having to increase the size of the components or imposing structural constraints in order to ensure insulation.

[0008] The present invention has been made in view of the above, and its objective is to easily reduce the voltage between elements and ground without degrading the filter characteristics. [Means for solving the problem]

[0009] The power supply device according to this embodiment comprises a voltage conversion circuit having a pair of output terminals and converting a DC voltage to an AC voltage; a filter circuit having an inductor as a first element and a capacitor as a second element connected in series, with one end connected to one of the output terminals of the voltage conversion circuit; and a transformer with one end connected to the other end of the filter circuit and the other end connected to the other output terminal of the voltage conversion circuit. When the number of first elements is m (m: a natural number of 1 or more) and the number of second elements is n (n: a natural number of 1 or more), m × n ≥ 2. Furthermore, when the inductance set in the filter circuit is LL0 and the capacitance is CC0, the inductances of the m first elements are LL1, LL2, LL3, ..., LLm, respectively, and the capacitances of the n second elements are CC1, CC2, CC3, ..., CCn, respectively. LL1 + LL2 + LL3 + ... + LLm = LL0 1 / CC1+1 / CC2+1 / CC3+…+1 / CCn=1 / CC0 The filter circuit is said to consist of the first element and the second element one by one alternately Connected in series Placed 、 Among the m first elements, the inductor having the largest inductance The wiring between the capacitor and the ground is directly connected. Voltage Peak value , or the capacitor having the smallest capacitance among the n preceding second elements. The wiring between the inductor and the ground is directly connected. Voltage Peak value but The voltage is lower than the peak voltage to ground in the wiring between the inductor and the capacitor when an inductor with inductance = LL0 and a capacitor with capacitance = CC0 are connected in series. To become a voltage composition It is being done.

[0010] With the above configuration, the voltage to ground generated between the first element and the second element (inter-element wiring) is reduced compared to the case where the filter circuit is composed of one first element and one second element, without degrading the filter characteristics. To the desired voltage to ground It can be reduced.

[0011] Also, in the filter circuit, when the number of the first elements is 2 or more, all the first elements have the same inductance, and when the number of the second elements is 2 or more, all the second elements have the same capacitance.

[0012] According to the above configuration, the voltage applied to the first element can be evenly reduced, and the voltage applied to the second element can also be evenly reduced. Therefore, in the entire filter circuit, the voltage between the first element and the second element can be evenly reduced.

Effect of the Invention

[0013] According to the embodiment, there is an effect that the voltage to ground generated between elements (inter-element wiring) can be reduced without degrading the filter characteristics.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a schematic configuration block diagram of a class-D amplifier. [Figure 2] FIG. 2 is an explanatory diagram of the main part configuration of a conventional class-D amplifier. [Figure 3] FIG. 3 is an explanatory diagram of the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram of the first specific example of the first embodiment. [Figure 5] FIG. 5 is an explanatory diagram of the second specific example of the first embodiment. [Figure 6] FIG. 6 is an explanatory diagram of the second embodiment. [Figure 7] FIG. 7 is an explanatory diagram of the first specific example of the second embodiment. [Figure 8] FIG. 8 is an explanatory diagram of the second specific example of the second embodiment. [Figure 9] FIG. 9 is an explanatory diagram of the third embodiment. [Figure 10] FIG. 10 is an explanatory diagram of a specific example of the third embodiment.

Modes for Carrying Out the Invention

[0015] Next, embodiments will be described with reference to the drawings. Figure 1 is a schematic block diagram of a Class D amplifier. The Class D amplifier 10 includes a PWM circuit 11, a gate driver section 12, a full-bridge switching circuit 13, an LC filter (low-pass filter) 14, a transformer 15, and a DC power supply section 16.

[0016] The PWM circuit 11 generates a PWM control signal SPWM and outputs it to the gauge driver unit 12. The gate driver unit 12 outputs gate drive signals GD1 to GD4 that are supplied to the gate terminals of the transistors constituting the full-bridge switching circuit 13 based on the PWM control signal.

[0017] The full-bridge switching circuit 13 is driven based on gate drive signals GD1 to GD4. The LC filter 14 is composed of m inductors and n capacitors, with the inductors and capacitors connected alternately in series. Here, m is a natural number greater than or equal to 1, n is a natural number greater than or equal to 1, and m × n ≥ 2.

[0018] Furthermore, "one inductor" does not refer to a single physical inductor; for example, if two inductors are directly connected, they are considered as one inductor. Similarly, "one capacitor" does not refer to a single physical capacitor; for example, if two capacitors are directly connected, they are considered as one capacitor.

[0019] Therefore, when the connections are in the order of inductor → inductor → capacitor → inductor, it is considered that one inductor, one capacitor, and one inductor are connected in series. Similarly, when the connections are in the order of capacitor → capacitor → inductor → inductor → inductor → capacitor, it is considered that one capacitor, one inductor, and one capacitor are connected in series. The same applies to the following embodiments.

[0020] Furthermore, when connecting an inductor and a capacitor in series, if the inductor is considered the first element and the capacitor the second element, there is a point where one element of either the first or second element is sandwiched between the other pair of elements. In this case, the arrangement of one element of either the first or second element between the other elements means that the three elements are connected in series in the order of one element - the other element - the first element. For example, if one element is an inductor and the other element is a capacitor, the connection is in the order of inductor - capacitor - inductor, and if one element is a capacitor and the other element is an inductor, the connection is in the order of capacitor - inductor - capacitor. Furthermore, the inductor (first element) and the capacitor (second element) are arranged alternately so that the fluctuations in the applied voltage can be canceled out, since their applied voltage fluctuations are in opposite directions. The same applies to the following embodiments.

[0021] The transformer 15 transforms the voltage applied to the primary coil according to the turns ratio of the primary and secondary coils and supplies it to the load LD.

[0022] The DC power supply unit 16 supplies power to the load LD via the full-bridge switching circuit 13. In the following description, it is assumed that power is supplied to operate each component of the Class D amplifier 10 by a power supply circuit not shown.

[0023] First, before describing the operation of the embodiment, we will explain the problems of conventional Class D amplifiers. Figure 2 is an explanatory diagram of the main components of a conventional Class D amplifier. In Figure 2, the same reference numerals are used for parts that are the same as those in Figure 1.

[0024] As shown in Figure 2(A), the full-bridge switching circuit 13 includes a first upper transistor TU1 which constitutes a first upper arm and to which a gate drive signal GD1 is input at its gate terminal, a second upper transistor TU2 which constitutes a second upper arm and to which a gate drive signal GD2 is input at its gate terminal, a first lower transistor TU3 which constitutes a first lower arm and to which a gate drive signal GD3 is input at its gate terminal, and a second lower transistor TU4 which constitutes a second lower arm and to which a gate drive signal GD4 is input at its gate terminal.

[0025] In this case, a parasitic diode is formed between the drain terminal and source terminal of each transistor TU1 to TU4.

[0026] The LC filter 14P comprises an inductor L0 and a capacitor C0 connected in series with the inductor L0. This LC filter 14P functions as a resonant circuit.

[0027] In the above configuration, the full-bridge switching circuit 13 generates a square wave differential voltage by switching the DC power supplied from the DC power supply unit 16, removes harmonic components (especially the 3rd and 5th harmonics) using an LC filter, and supplies a sinusoidal voltage (AC voltage) to the transformer 15.

[0028] The transformer 15 then transforms the sinusoidal voltage applied to the primary coil according to the ratio of the number of turns in the primary coil to the number of turns in the secondary coil, and supplies it to the load LD, which is configured as a plasma device or the like.

[0029] Here, we will explain the general characteristics of LC filters. Generally, it is considered that the characteristics of an LC filter are better as the value of Q (Quality Factor) shown below is larger.

[0030]

Number

[0031] However, the voltage V applied to the inductor L0 L and the voltage V applied to the capacitor C0 C increase in proportion to the value of Q as shown by the following equation.

[0032]

Number

[0033] In this case, the phase of the voltage V L and the phase of the voltage V C are phases that cancel each other out, but in the wiring between the inductor L0 and the capacitor C0, the voltage before cancellation

[0034]

Number

[0035] is applied as it is. Therefore, the voltage to ground generated between the inductor L0 and the capacitor C0 increases.

[0036] More specifically, when the voltage V_HV0 in the wiring between the inductor L0 and the capacitor C0 that constitutes the LC filter 14P is obtained by a circuit simulator, as shown in Fig. 2(B), it can be seen that the voltage V_HV0 in the wiring between the inductor L0 and the capacitor C becomes a high voltage at the times t1 and t2 when the switching of the transistors TU1 to TU4 is performed.

[0037] Since the DC power supply unit 16 and the LC filter 14P are not grounded, the potential at the position of the LC filter 14P is uncertain. Therefore, the amplitude center of the output waveform of the full-bridge switching circuit 13 may not be 0 volts. To address this, the circuit simulator conditions were set so that the amplitude center of the output waveform of the full-bridge switching circuit 13 becomes an AC waveform with a 0 volt amplitude. In the following, keeping the above in mind, each condition was compared using the voltage peak value (hereinafter referred to as the peak value) in the simulation results. The voltage peak-peak value (hereinafter referred to as the peak-peak value) will be used in explanations as needed.

[0038] In the example shown in Figure 2(B), when the output voltage of the DC power supply unit 16 is 400 volts and the turns ratio of the transformer 15 is 1:2, the voltage V_HV0 reaches a peak value of approximately 2,440 volts. At this time, the voltage on the secondary side of the transformer 15 is approximately 1,010 volts at its peak, indicating that the voltage V_HV0 is high. As a result, from the standpoint of ensuring insulation, there was a risk of having to increase the size of the components or being subject to structural constraints.

[0039] Therefore, the objective of the following embodiment is to suppress the voltage to ground generated between the inductor and capacitor without causing a decrease in filter characteristics.

[0040] [1] First Embodiment Figure 3 is an explanatory diagram of the first embodiment. In Figure 3, the same reference numerals are used for parts that are the same as those in Figures 1 and 2.

[0041] In the following explanation, let m be the number of series-connected inductors and n be the number of series-connected capacitors that make up the LC filter. Here, m and n are natural numbers greater than or equal to 1, and m × n ≥ 2.

[0042] In the LC filter 14A shown in Figure 3, m = n-1. Furthermore, the LC filter 14A shown in Figure 3 will be described as having the same characteristics as the LC filter 14P shown in Figure 2.

[0043] In other words, if the inductances of inductors L1 to Ln-1 are denoted as inductances LL1 to LL(n-1), the relationship between inductor L0 and inductance LL0 is as follows: LL0=LL1+LL2+…+LL(n-2)+LL(n-1)

[0044] Furthermore, if the capacitances of capacitors C1 to Cn are denoted as capacitances CC1 to CCn, the relationship with capacitance CC0 of capacitor C0 is as follows: 1 / CC0=1 / CC1+1 / CC2+…+1 / CC(n-1)+1 / CCn

[0045] First, a first specific example of the first embodiment will be described. Figure 4 is an explanatory diagram of a first specific example of the first embodiment. For ease of understanding, we will explain this using the case where m=n-1=1 (where there is one inductor and two capacitors) as an example.

[0046] In Figure 4, the same reference numerals are used for parts that are the same as those in Figure 2. In Figure 4, the difference from Figure 2 is that capacitor C1 is connected before inductor L0 and capacitor C2 is connected after inductor L0, instead of capacitor C0. Furthermore, in Figure 4, the sections of capacitor C1, inductor L0, and capacitor C2 represent locations where one of the elements (in this case, the first element, the inductor) is placed between one of the elements of a pair (in this case, the second element, the capacitor).

[0047] In this case, as described above, if the capacitances of capacitors C1 and C2 are denoted as capacitances CC1 and CC2, the relationship with the capacitance CC0 of capacitor C0 is as follows: 1 / CC0 = 1 / CC1 + 1 / CC2

[0048] For example, if 2·CC0 = CC1 = CC2, then the above equation is satisfied.

[0049] In the example above, capacitors C1 and C2 have the same capacitance, and capacitors C1 and C2 are connected in series via inductor L0. If we let V be the voltage applied to the entire capacitors C1 and C2, V1 be the voltage applied to capacitor C1, and V2 be the voltage applied to capacitor C2, then the following applies.

[0050] V1 = V2 = V·CC2 / (CC1 + CC2) =V·CC1 / (CC1+CC2)

[0051] On the other hand, since the voltage applied to capacitor C0 shown in Figure 2 is Vc = V, it can be seen that the voltages V1 applied to capacitor C1 and V2 applied to capacitor C2 will be lower than in the conventional example.

[0052] When the voltage V_HV1 in the wiring between inductor L0 and capacitor C1, which constitute the LC filter 14B, is determined by a circuit simulator, as shown in Figure 4(B), at times t1 and t2 when transistors TU1 to TU4 are switched, the voltage V_HV1 in the wiring between inductor L0 and capacitor C1 rises, but it is very low compared to the case in Figure 2(B) (peak value of approximately 2,440 volts) (peak value of approximately 1,425 volts in the example of Figure 4(B)).

[0053] Similarly, when the voltage V_HV2 in the wiring between the inductor L0 and capacitor C2 constituting the LC filter 14B is determined by a circuit simulator, as shown in Figure 4(B), at times t1 and t2 when the transistors TU1 to TU4 are switched, the voltage V_HV2 in the wiring between the inductor L0 and capacitor C2 rises, but it is very low compared to the case in Figure 2(B) (peak value of approximately 2,440 volts) (peak value of approximately 1,425 volts in the example of Figure 4(B)).

[0054] Next, a second specific example of the first embodiment will be described. Figure 5 is an explanatory diagram of a second specific example of the first embodiment. For ease of understanding, we will use the case where m = n-1 = 2 as an example to provide a concrete explanation. In Figure 5, the same reference numerals are used for parts that are the same as those in Figure 2.

[0055] In Figure 5, the difference from Figure 2 is that, as the LC filter 14C, capacitors C1, C2, and C3 are provided instead of capacitor C0, and inductors L1 and L2 are provided instead of inductor L0, and they are connected in series in the order of capacitor C1 → inductor L2 → capacitor C2 → inductor L2 →, capacitor C3.

[0056] Furthermore, in Figure 5, the sections of capacitor C1, inductor L1 and capacitor C2, and the sections of capacitor C2, inductor L2 and capacitor C3, respectively, are locations where one of a pair of elements (in this case, the second element, the capacitor) is placed between the other element (in this case, the first element, the inductor).

[0057] Similarly, the sections of inductor L1, capacitor C2, and inductor L2 are locations where one of a pair of elements (in this case, the first element, the inductor) is placed between the other element (in this case, the second element, the capacitor). These also apply to the following other embodiments.

[0058] In this case, as described above, if the capacitances of capacitors C1, C2, and C3 are denoted as capacitances CC1, CC2, and CC3, the relationship with the capacitance CC0 of capacitor C0 is as follows: 1 / CC0 = 1 / CC1 + 1 / CC2 + 1 / CC3 For example, if 3·CC0=CC1=CC2=CC3, then the above equation is satisfied.

[0059] In the example above, capacitors C1, C2, and C3 have the same capacitance, and capacitors C1, C2, and C3 are connected in series via inductors L1 and L2. If we denote the voltage applied to the entire set of capacitors C1 and C2 as V, the voltage applied to capacitor C1 as V1, the voltage applied to capacitor C2 as V2, and the voltage applied to capacitor C3 as V3, then the following applies.

[0060] V1=V2=V3=V·CC1 / (CC1+CC2+CC3) =V·CC2 / (CC1+CC2+CC3) =V·CC3 / (CC1+CC2+CC3)

[0061] In this case, since the voltage Vc applied to capacitor C0 shown in Figure 2 is V, it can be seen that the voltages V1 applied to capacitor C1, V2 applied to capacitor C2, and V3 applied to capacitor C3 are lower than in the conventional example.

[0062] On the other hand, as mentioned above, if the inductances of inductors L1 and L2 are denoted as inductances LL1 and LL2, the relationship with the inductance LL0 of inductor L0 is as follows: LL0 = LL1 + LL2 For example, if LL0 / 2 = LL1 = LL2, then the above equation is satisfied.

[0063] In the example above, the inductances of inductors L1 and L2 are the same, and inductors L1 and L2 are connected in series via capacitor C2. If we denote the voltage applied to the entire inductor L1 and L2 as V10, the voltage applied to inductor L1 as V11, and the voltage applied to inductor L2 as V12, then the following applies. V11=V12=V10 / 2

[0064] On the other hand, the voltage V applied to the inductor L0 shown in Figure 2 L Since = V10, it can be seen that the voltage V11 applied to inductor L1 and the voltage V12 applied to inductor L2 will be lower than in the conventional example.

[0065] The voltages V_HV1 in the wiring between capacitor C1 and inductor L1, V_HV2 in the wiring between inductor L1 and capacitor C2, V_HV3 in the wiring between capacitor C2 and inductor L2, and V_HV4 in the wiring between inductor L2 and capacitor C3, which constitute the LC filter 14C, are determined using a circuit simulator.

[0066] As a result, as shown in Figure 5(B), at time t1 or t2 when transistors TU1 to TU4 are switched, although the voltage V_HV1 in the wiring between capacitor C1 and inductor L1 and the voltage V_HV4 in the wiring between inductor L2 and capacitor C3 rise, the voltage V_HV2 in the wiring between inductor L1 and capacitor C2 and the voltage V_HV4 in the wiring between capacitor C2 and inductor L2 cancel each other out, and the fluctuations are greatly suppressed. Compared to the case in Figure 2(B) (peak value of approximately 2,440 volts), the voltage is less than half, at a very low voltage (peak value of approximately 1,084 volts in the example of Figure 5(B)).

[0067] As described above, according to this first embodiment, compared to the conventional example, the voltage between the inductor and capacitor and ground can be suppressed while maintaining the same filter characteristics, that is, without causing a decrease in filter characteristics.

[0068] The above explanation assumes that capacitor C0 is divided into two capacitors C1 and C2, with the capacitance of capacitors C1 and C2 being twice the capacitance of capacitor C0. However, if capacitor C0 is divided into X capacitors (where X is a natural number of 3 or more) with the same capacitance, within the limits of the installation area, and the capacitance of the multiple capacitors is X times the capacitance of capacitor C0, it becomes possible to further suppress the voltage to ground.

[0069] The above explanation concerns the case where LC filters 14A, 14B, and 14C are composed of capacitors with the same capacitance. However, it is also possible to combine capacitors with different capacitances to create a capacitor with the desired capacitance.

[0070] In this case, the voltage applied to the capacitor with the smallest capacitance will determine the voltage to ground between the inductor and capacitor, but the voltage to ground between the inductor and capacitor can be suppressed without causing a decrease in filter characteristics.

[0071] Furthermore, if the number of first elements (inductors) is two or more, the inductance of all first elements should be the same. Similarly, if the number of second elements (capacitors) is two or more, the voltage can be most effectively suppressed by making the capacitance of all second elements the same. Of course, it is difficult to make the inductance and capacitance exactly the same, so it is sufficient to make them the same within the tolerance range. This is also true for the second embodiment and others described later.

[0072] Furthermore, although the above explanation used the full-bridge switching circuit 13 as an example of a voltage conversion circuit, it is not limited to this. For example, other voltage conversion circuits such as a half-bridge switching circuit can be used. This is also true for the second embodiment described later.

[0073] [2] Second embodiment Figure 6 is an explanatory diagram of the second embodiment. In Figure 6, the same reference numerals are used for parts that are the same as those in Figures 1 and 2 of the first embodiment.

[0074] In this second embodiment, the number of inductors m constituting the LC filter C is expressed using the number of capacitors n, where m = n + 1. Furthermore, the LC filter 14D shown in Figure 6 will also be described as having the same characteristics as the LC filter 14P shown in Figure 2.

[0075] In other words, if the inductances of inductors L1 to Ln+1 are denoted as inductances LL1 to LL(n+1), the relationship between inductor L0 and inductance LL0 is as follows: LL0 = LL1 + LL2 + ... + LLn + LL(n+1)

[0076] Furthermore, if the capacitances of capacitors C1 to Cn are denoted as capacitances CC1 to CCn, the relationship with capacitance CC0 of capacitor C0 is as follows: 1 / CC0=1 / CC1+1 / CC2+…+1 / CC(n-1)+1 / CCn

[0077] Next, a first specific example of the second embodiment will be described. Figure 7 is an explanatory diagram of the first specific example of the second embodiment. For ease of understanding, we will use the case m = n + 1 = 2 as an example to provide a concrete explanation.

[0078] In Figure 7, the same reference numerals are used for parts that are the same as those in Figure 2. In Figure 7, the difference from Figure 2 is that, instead of inductor L0, inductor L1 connected before capacitor C0 and inductor L2 connected after capacitor C0 are provided.

[0079] In this case, as described above, if the inductances of inductors L1 and L2 are denoted as inductances LL1 and LL2, the relationship with the inductance LL0 of inductor L0 is as follows: LL0 = LL1 + LL2 For example, if LL0 / 2 = LL1 = LL2, then the above equation is satisfied.

[0080] In the example above, the inductances of inductors L1 and L2 are the same, and inductors L1 and L2 are connected in series via capacitor C0. If we let V10 be the voltage applied to the entire set of inductors L1 and L2, V11 be the voltage applied to inductor L1, and V12 be the voltage applied to inductor L2, then the following applies. V11=V12=V10 / 2

[0081] On the other hand, the voltage V applied to the inductor L0 shown in Figure 2 L Since = V, it can be seen that the voltage V11 applied to inductor L1 and the voltage V12 applied to inductor L2 will be lower than in the conventional example.

[0082] When the voltage V_HV1 in the wiring between the capacitor C0 and inductor L1 that constitute the LC filter 14E is determined by a circuit simulator, it can be seen that the voltage V_HV1 in the wiring between the inductor L0 and capacitor C1 is very low (approximately 1,240 volts at the peak in the example of Figure 7(B)) compared to the case in Figure 2(B) (approximately 2,440 volts at the peak).

[0083] Similarly, when the voltage V_HV2 in the wiring between capacitor C0 and inductor L2, which constitute the LC filter 14C, is determined by a circuit simulator, as shown in Figure 7(B), the voltage V_HV2 in the wiring between capacitor C0 and inductor L2 increases, but it is still very low compared to the case in Figure 2(B) (peak value of approximately 2,440 volts) (peak value of approximately 1,240 volts in the example of Figure 7(B)).

[0084] Next, a second specific example of the second embodiment will be described. Figure 8 is an explanatory diagram of a second specific example of the second embodiment. For ease of understanding, we will use the case where m = n + 1 = 3 as an example to provide a concrete explanation. In Figure 8, the same reference numerals are used for parts that are the same as those in Figure 2.

[0085] In Figure 8, the difference from Figure 2 is that, as the LC filter 14D, inductors L1, L2, and L3 are provided instead of inductor L0, and capacitors C1 and C2 are provided instead of capacitor C0, and they are connected in series in the order of inductor L1 → capacitor C1 → inductor L2 → capacitor C2 → inductor L3.

[0086] In this case, as described above, if the inductances of inductors L1, L2, and L3 are denoted as inductances LL1, LL2, and LL3, the relationship with the inductance LL0 of inductor L0 is as follows: LL0 = LL1 + LL2 + LL3 In other words, the inductances LL1 = LL0 / 3, LL2 = LL0 / 3, and LL3 = LL0 / 3. For example, if LL0 / 3 = LL1 = LL2 = LL3, then the above equation is satisfied.

[0087] In the example above, the inductances of inductors L1, L2, and L3 are the same, and inductors L1, L2, and L3 are connected in series via capacitors C1 and C2. If we let V10 be the voltage applied to the entire group of inductors L1, L2, and L3, V11 be the voltage applied to inductor L1, and V12 be the voltage applied to inductor L2, then the following applies. V11=V12=V13=V10 / 3

[0088] In this case, the voltage V applied to the inductor L0 shown in Figure 2 L Since = V, it can be seen that the voltages V11 applied to inductor L1, V12 applied to inductor L2, and V13 applied to inductor L3 are lower than in the conventional example.

[0089] On the other hand, as mentioned above, if the inductances of capacitors C1 and C2 are denoted as capacitances CC1 and CC2, the relationship with the capacitance CC0 of capacitor C0 is as follows: 1 / CC0 = 1 / CC1 + 1 / CC2 In other words, capacitance CC1 = 2·CC0 and capacitance CC2 = 2·CC0. For example, if 2·CC0 = CC1 = CC2, then the above equation is satisfied.

[0090] In the example above, capacitors C1 and C2 have the same capacitance, and capacitors C1 and C2 are connected in series via inductor L2. If we let V be the voltage applied to the entire capacitors C1 and C2, V1 be the voltage applied to capacitor C1, and V2 be the voltage applied to capacitor C2, then the following applies. V1 = V2 = V·CC1 / (CC1 + CC2) =V·CC2 / (CC1+CC2)

[0091] In this case, since the voltage Vc applied to capacitor C0 shown in Figure 2 is V, it can be seen that the voltage V1 applied to capacitor C1 and the voltage V2 applied to capacitor C2, and the voltage V3 applied to them, will be lower than in the conventional example.

[0092] The voltages V_HV1 in the wiring between inductor L1 and capacitor C1, V_HV2 in the wiring between capacitor C1 and inductor L2, V_HV3 in the wiring between inductor L2 and capacitor C2, and V_HV4 in the wiring between capacitor C2 and inductor L3, which constitute the LC filter 14F, are determined using a circuit simulator.

[0093] As a result, as shown in Figure 8(B), at time t1 or t2 when transistors TU1 to TU4 are switched, the voltages V_HV1 in the wiring between inductor L1 and capacitor C1, V_HV2 in the wiring between capacitor C1 and inductor L2, V_HV3 in the wiring between inductor L2 and capacitor C2, and V_HV4 in the wiring between capacitor C2 and inductor L3 fluctuate, but cancel each other out, and the fluctuations are greatly suppressed. Compared to the case in Figure 2(B) (peak value of approximately 2,440 volts), the voltages are less than half, at a very low voltage (in the example of Figure 8(B), the peak value is approximately 1,011 volts).

[0094] As described above, according to this second embodiment, similar to the first embodiment, it is possible to suppress the voltage to ground generated between the inductor and capacitor while maintaining the same filter characteristics as the conventional example, that is, without causing a decrease in filter characteristics.

[0095] The above description of the second embodiment involved cases where inductor L0 was divided into two and cases where inductor L0 was divided into three inductors, and capacitor C0 was divided into two capacitors C1 and C2. However, if the installation area is acceptable, it is possible to further suppress the voltage to ground by similarly increasing the number of divisions of the inductor and capacitor.

[0096] The above explanation concerns the case where LC filters 14D, 14E, and 14F are composed of inductors with the same inductance and capacitors with the same capacitance. However, it is also possible to combine inductors with different inductances to function as an inductor with a desired inductance, or to combine capacitors with different capacitances to function as a capacitor with a desired capacitance.

[0097] In this case, the voltage across the inductor with the largest inductance or the applied voltage across the capacitor with the smallest capacitance will determine the voltage between the inductor and capacitor to ground. However, this method can suppress the voltage between the inductor and capacitor to ground without degrading the filter characteristics.

[0098] [3] Third embodiment Figure 9 is an explanatory diagram of the third embodiment. In Figure 9, the same reference numerals are used for parts that are the same as those in Figures 1 and 2 of the first embodiment.

[0099] In this third embodiment, the number of inductors m constituting the LC filter is expressed using the number of capacitors n, where m = n. Furthermore, the LC filter 14G shown in Figure 9 will also be described as having the same characteristics as the LC filter 14P shown in Figure 2.

[0100] In other words, if the inductances of inductors L1 to Ln are denoted as inductances LL1 to LLn, the relationship between inductor L0 and inductance LL0 is as follows: LL0 = LL1 + LL2 + ... + LL(n-1) + LLn

[0101] Furthermore, if the capacitances of capacitors C1 to Cn are denoted as capacitances CC1 to CCn, the relationship with capacitance CC0 of capacitor C0 is as follows: 1 / CC0=1 / CC1+1 / CC2+…+1 / CC(n-1)+1 / CCn

[0102] Next, a first specific example of the third embodiment will be described. Figure 10 is an explanatory diagram of a specific example of the third embodiment. For ease of understanding, we will use the case where m=n=2 as an example to provide a concrete explanation. In Figure 10, the same reference numerals are used for parts that are the same as those in Figure 2.

[0103] In Figure 10, the difference from Figure 2 is that capacitor C1 and capacitor C2 are provided instead of capacitor C0, and inductors L1 and L2 are provided instead of inductor L0, and they are connected in series in the order of capacitor C1 → inductor L1 → capacitor C2 → inductor L2.

[0104] In this case, as described above, if the inductances of inductors L1 and L2 are denoted as inductances LL1 and LL2, the relationship with the inductance LL0 of inductor L0 is as follows: L0 = LL1 + LL2

[0105] In other words, the inductance LL1 = LL0 / 2 and the inductance LL2 = LL0 / 2. For example, if LL0 / 2 = LL1 = LL2, then the above equation is satisfied.

[0106] In the example above, the inductances of inductors L1 and L2 are the same, and inductors L1 and L2 are connected in series via capacitor C2. If we denote the voltage applied to the entire inductor L1 and L2 as V10, the voltage applied to inductor L1 as V11, and the voltage applied to inductor L2 as V12, then the following applies. V11=V12=V10 / 2

[0107] On the other hand, the voltage V applied to the inductor L0 shown in Figure 2 LSince = V, it can be seen that the voltage V11 applied to inductor L1 and the voltage V12 applied to inductor L2 will be lower than in the conventional example.

[0108] On the other hand, as mentioned above, if the inductances of capacitors C1 and C2 are denoted as capacitances CC1 and CC2, the relationship with the capacitance CC0 of capacitor C0 is as follows: 1 / CC0 = 1 / CC1 + 1 / CC2 For example, if 2·CC0 = CC1 = CC2, then the above equation is satisfied.

[0109] In the example above, capacitors C1 and C2 have the same capacitance, and capacitors C1 and C2 are connected in series via inductor L1. If we let V be the voltage applied to the entire capacitors C1 and C2, V1 be the voltage applied to capacitor C1, and V2 be the voltage applied to capacitor C2, then the following applies. V1 = V2 = V·CC1 / (CC1 + CC2) =V·CC2 / (CC1+CC2)

[0110] In this case, since the voltage Vc applied to capacitor C0 shown in Figure 2 is V, it can be seen that the voltage V1 applied to capacitor C1 and the voltage V2 applied to capacitor C2, and the voltage V3 applied to them, will be lower than in the conventional example.

[0111] When the voltage V_HV1 in the wiring between capacitor C0 and inductor L1, which constitute the LC filter 14H, is determined by a circuit simulator, as shown in Figure 10(B), potential fluctuations are suppressed at times t1 and t2 when transistors TU1 to TU4 are switched, and the voltage V_HV1 in the wiring between inductor L0 and capacitor C1 is lower (approximately 1,425 volts at the peak in the example of Figure 10(B)) compared to the case in Figure 2(B) (approximately 2,440 volts at the peak).

[0112] Similarly, when the voltage V_HV2 in the wiring between the inductor L1 and capacitor C2 that constitute the LC filter 14F is determined by a circuit simulator, as shown in Figure 10(B), the voltage V_HV2 in the wiring between capacitor C0 and inductor L2 rises, but it is very low compared to the case in Figure 2(B) (peak value of approximately 2,440 volts) (peak value of approximately 500 volts in the example of Figure 10(B)).

[0113] Furthermore, when the voltage V_HV3 in the wiring between capacitor C2 and inductor L2, which constitute the LC filter 14F, is determined using a circuit simulator, it can be seen that, as shown in Figure 10(B), the voltage V_HV3 in the wiring between capacitor C2 and inductor L0 is lower (approximately 1,200 volts at the peak in the example of Figure 10(B)) compared to the case in Figure 2(B) (approximately 2,440 volts at the peak).

[0114] As described above, according to this third embodiment, similar to the first embodiment, it is possible to suppress the voltage to ground generated between the inductor and capacitor while maintaining the same filter characteristics as the conventional example, that is, without causing a decrease in filter characteristics.

[0115] The above explanation described a case where the inductor L0 is divided into two and the capacitor C0 is divided into two capacitors C1 and C2. However, if the installation area is acceptable, it is possible to further suppress the voltage to ground by similarly increasing the number of divisions of the inductor and capacitor.

[0116] The above explanation concerns the case where LC filters 14G and 14H are composed of an inductor with the same inductance and a capacitor with the same capacitance. However, it is also possible to combine inductors with different inductances to function as an inductor with a desired inductance, or to combine capacitors with different capacitances to function as a capacitor with a desired capacitance.

[0117] In this case, the voltage across the inductor with the largest inductance or the applied voltage across the capacitor with the smallest capacitance will determine the voltage between the inductor and capacitor to ground. However, this method can suppress the voltage between the inductor and capacitor to ground without degrading the filter characteristics.

[0118] The embodiments and modifications described above can be combined as appropriate and are illustrative examples only, not limiting the scope of the invention. Furthermore, the embodiments and modifications described above are included in the scope and gist of the invention and are included in the scope of the invention and its equivalents as described in the claims. [Explanation of Symbols]

[0119] 10...Class D amplifier, 11...PWM circuit, 12...Gate driver section, 13...Full bridge switching circuit (voltage conversion circuit), 14, 14A~14F...LC filter, 15...Transformer, 16...DC power supply section, LD...Load, L1, L2, L3, ..., Lm...Inductor (first element), C1, C2, C3, ..., Cn...Capacitor (second element).

Claims

1. A voltage conversion circuit having a pair of output terminals that converts DC voltage to AC voltage, A filter circuit having an inductor as a first element and a capacitor as a second element connected in series, with one end connected to one of the output terminals of the voltage conversion circuit, A transformer, one end of which is connected to the other end of the filter circuit and the other end of which is connected to the output terminal of the other end of the voltage conversion circuit, is provided. Let m be the number of the first element (m: a natural number greater than or equal to 1), and let n be the number of the second element (n: a natural number greater than or equal to 1). Then m × n ≥ 2. Furthermore, if the inductance set in the filter circuit is LL0 and the capacitance is CC0, The inductances of the m first elements are LL1, LL2, LL3, ..., LLm, respectively. The capacitances of the n second elements are CC1, CC2, CC3, ..., CCn, respectively. LL1+LL2+LL3+…+LLm=LL0 1 / CC1+1 / CC2+1 / CC3+...+1 / CCn=1 / CC0 It is said that The filter circuit is arranged such that the first element and the second element are connected alternately in series, The configuration is such that the peak voltage to ground in the wiring between the inductor having the largest inductance among the m first elements and the capacitor directly connected to it, or the peak voltage to ground in the wiring between the capacitor having the smallest capacitance among the n second elements and the inductor directly connected to it, is lower than the peak voltage to ground in the wiring between an inductor and a capacitor when an inductor having inductance = LL0 and a capacitor having capacitance = CC0 are connected in series. power supply.

2. In the aforementioned filter circuit, If the number of the first elements is two or more, all of the first elements have the same inductance. If the number of the second elements is two or more, all of the second elements have the same capacitance. The power supply device according to claim 1.

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