Circuit

Abstract

The power supply unit (10) is provided with bypass paths (40, 40a-40c) through which a part of a current including a lightning surge current superimposed on a current from the power supply (2) flows, and is provided with an impedance increasing circuit (11) which increases the equivalent impedance between the power supply (2) and the main circuit unit (50) in accordance with the current flowing through the bypass paths (40, 40a-40c).

Description

Technical Field

[0001] The present disclosure relates to a circuit including a power supply unit and a main circuit unit to which electric power is supplied from a power supply via the power supply unit. Background Art

[0002] Patent Document 1 discloses a circuit including a power supply unit and a main circuit unit, the main circuit unit being supplied with power from an AC power supply via the power supply unit. In the circuit, the power supply unit has a reactor and an AC / DC conversion circuit, and the main circuit unit has a capacitor and a DC / AC conversion circuit.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Publication No. 2020-124104 Summary of the invention

[0006] -Technical problem to be solved by the invention-

[0007] In a circuit like that disclosed in Patent Document 1, when a lightning strike occurs, the main circuit portion may be destroyed by a lightning surge.

[0008] The present disclosure is made to solve the above-mentioned technical problems, and its purpose is to make a main circuit unit less likely to be destroyed by a lightning surge, wherein power is supplied from a power supply to the main circuit unit.

[0009] -Technical solutions to solve technical problems-

[0010] The first aspect is a circuit, which includes a power supply unit 10 and a main circuit unit 50, and power is supplied from the power supply 2 to the main circuit unit 50 via the power supply unit 10, characterized in that: the power supply unit 10 includes a bypass path 40, 40a~40c, and the bypass path 40, 40a~40c allows a part of the current including the lightning surge current to flow through, and the lightning surge current is a current superimposed on the current from the power supply 2, and the power supply unit 10 includes an impedance increase circuit 11, and the impedance increase circuit 11 increases the equivalent impedance between the power supply 2 and the main circuit unit 50 according to the current flowing through the bypass path 40, 40a~40c.

[0011] Here, the lightning surge current is a current superimposed on the current flowing due to the voltage normally supplied from the power supply 2. In addition, the lightning surge current flows when the voltage of the power supply 2 rises due to the occurrence of the lightning surge. In the first aspect, when the lightning surge current is superimposed on the current from the power supply 2, a part of the current including the lightning surge current is made to flow through the bypass paths 40, 40a to 40c, and the equivalent impedance between the power supply 2 and the main circuit unit 50 is increased, thereby reducing the current flowing from the power supply 2 to the main circuit unit 50. Therefore, the main circuit unit 50 is not easily destroyed by the lightning surge.

[0012] The second aspect is based on the first aspect and is characterized in that when a part of the current including the lightning surge current flows through the bypass path 40, 40a~40c, the impedance increasing circuit 11 uses the electric energy sent to the bypass path 40, 40a~40c to increase the impedance.

[0013] In the second aspect, since the electric energy of the lightning surge current can be used to suppress the lightning surge current from intruding into the main circuit unit 50 , energy can be used effectively.

[0014] The third aspect is, based on the first or second aspect, characterized in that: the impedance increase circuit 11 generates a voltage between the power supply 2 and the main circuit unit 50 to suppress the current from flowing in the direction of the main circuit unit 50 according to the current flowing through the bypass path 40, 40a~40c, and the current includes the lightning surge current.

[0015] The fourth aspect is, based on any one of the first to third aspects, characterized in that: the impedance increase circuit 11 has a main winding 30 and an auxiliary winding 41, the main winding 30 is arranged on the path for supplying power from the power supply 2 to the main circuit unit 50, the auxiliary winding 41 is arranged on the bypass path 40 and is magnetically coupled with the main winding 30, and the impedance increase circuit 11 generates the voltage by allowing a part of the current including the lightning surge current to flow through the auxiliary winding 41, thereby changing the magnetic flux passing through the main winding 30.

[0016] In the fourth aspect, when a lightning surge current is applied between any two lines connected to the power supply 2 , the equivalent impedance between the power supply 2 and the main circuit unit 50 can be increased, and the voltage increase of the main circuit unit 50 can be suppressed.

[0017] A fifth aspect is characterized in that, based on the fourth aspect, a surge absorber 42 connected in series with the auxiliary winding 41 is provided on the bypass path 40, 40a to 40c.

[0018] In the fifth aspect, the surge absorber 42 restricts the current from flowing through the bypass paths 40, 40a to 40c when no lightning surge occurs. On the other hand, when a lightning surge occurs, the surge absorber 42 is short-circuited, so the current flows through the bypass paths 40, 40a to 40c. Therefore, since it is not necessary to control whether the current flows through the bypass paths 40, 40a to 40c by a computer, the delay time from the occurrence of the lightning surge to the current flowing to the bypass paths 40, 40a to 40c can be shortened.

[0019] A sixth aspect is, based on any one of the fourth to fifth aspects, characterized in that: the polarity directions of the main winding 30 and the auxiliary winding 41 are the same as each other.

[0020] In the sixth aspect, when a current including a lightning surge current flows through the bypass paths 40 and 40 a to 40 c , a voltage that suppresses the current from flowing toward the main circuit unit 50 can be generated in the main winding 30 .

[0021] The seventh aspect is, based on any one of the first to sixth aspects, characterized in that: the power supply 2 is an AC power supply, the power supply unit 10 includes a rectifier circuit 20 for rectifying the AC output from the power supply 2, the main circuit unit 50 has a DC-AC conversion circuit 60 and a capacitor 70, the DC-AC conversion circuit 60 converts the DC output from the rectifier circuit 20 into AC through a switching action, and the capacitor 70 is connected between the input nodes 60a and 60b of the DC-AC conversion circuit 60 to allow pulsation of the output voltage of the rectifier circuit 20.

[0022] In the seventh aspect, when the lightning surge current is superimposed on the current from the power source 2, the current flowing from the power source 2 to the capacitor 70 can be reduced, thereby suppressing the voltage rise of the capacitor 70. Therefore, the capacitor 70 can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a circuit diagram showing a configuration of a power conversion device as a circuit according to a first embodiment of the present disclosure;

[0024] Figure 2 is the equivalent of the comparative example Figure 1 's picture;

[0025] Figure 3 The voltage across the bypass path, the input voltage of the main circuit unit, the voltage of the main winding, and the input current of the main circuit unit in the comparative example are shown;

[0026] Figure 4A timing diagram showing the voltage at both ends of the bypass path, the input voltage of the main circuit unit, the voltage of the main winding, the input current of the main circuit unit, and the voltage of the auxiliary winding in the first embodiment with solid lines, and showing the voltage at both ends of the bypass path, the input voltage of the main circuit unit, the voltage of the main winding, and the input current of the main circuit unit in the comparative example with dotted lines;

[0027] Figure 5 This is a modification of the first embodiment. Figure 1 's picture;

[0028] Figure 6 The second embodiment is equivalent to Figure 1 's picture;

[0029] Figure 7 The third embodiment is equivalent to Figure 1 's picture;

[0030] Figure 8 This is a modification of the third embodiment. Figure 1 's picture;

[0031] Fig. 9 The fourth embodiment is equivalent to Figure 1 . DETAILED DESCRIPTION

[0032] The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be noted that the following embodiments are essentially only preferred examples and are not intended to limit the present invention, its application objects or its uses.

[0033] (First Embodiment)

[0034] Figure 1 A power conversion device 1 is shown as a circuit according to a first embodiment of the present disclosure. The power conversion device 1 converts input AC supplied from a power source 2 into AC having a desired frequency and a desired voltage, and supplies the AC to a load 3. The power source 2 is a three-phase AC power source. The load 3 is a motor.

[0035] The power conversion device 1 includes a power supply unit 10 , a main circuit unit 50 , and a control device (not shown). Electric power is supplied from a power supply 2 to the main circuit unit 50 via the power supply unit 10 .

[0036] The power supply unit 10 includes a rectifier circuit 20 , a main winding 30 , and a bypass path 40 .

[0037] The rectifier circuit 20 rectifies the three-phase AC output from the power supply 2 to the first power line L1 to the third power line L3 into a DC. The rectifier circuit 20 has a first input terminal 20a to a third input terminal 20c connected to the first power line L1 to the third power line L3, and a first output terminal 20d and a second output terminal 20e that output a DC. In detail, the rectifier circuit 20 is a full-wave rectifier circuit. The rectifier circuit 20 has six diodes 21 to 26 connected in a bridge shape as rectifier elements. The cathodes of these diodes 21 to 26 face the first output terminal 20d side, and the anodes of these diodes 21 to 26 face the second output terminal 20e side.

[0038] The main winding 30 is provided on a path for supplying power from the power source 2 to the main circuit unit 50. Specifically, one end of the main winding 30 is connected to the first output terminal 20d of the rectifier circuit 20, and the other end of the main winding 30 is connected to the main circuit unit 50 described in detail later. That is, the main winding 30 is connected in series with the rectifier circuit 20 and the main circuit unit 50.

[0039] The two ends of the bypass path 40 are respectively connected to the first output end 20d and the second output end 20e of the rectifier circuit 20. On the bypass path 40, an auxiliary winding 41 magnetically coupled to the main winding 30 and a varistor 42 as a surge absorber connected in series with the auxiliary winding 41 are provided in order from the first output end 20d side. The polarity directions of the main winding 30 and the auxiliary winding 41 are the same.

[0040] The main winding 30 and the auxiliary winding 41 constitute an impedance increasing circuit 11, which increases the equivalent impedance between the power supply 2 and the main circuit unit 50 according to the current flowing through the bypass path 40. Here, the equivalent impedance refers to |Vb| / |Im| when the voltage across the bypass path 40 is Vb and the current flowing from the power supply unit 10 to the main circuit unit 50 is Im.

[0041] The main circuit unit (50) includes a DC-to-AC conversion circuit (60) and a capacitor (70).

[0042] The direct-to-alternating-current conversion circuit 60 converts the direct current output by the rectifier circuit 20 into a three-phase alternating current through a switching action, and supplies the three-phase alternating current to the load 3. The direct-to-alternating-current conversion circuit 60 is controlled by a control device not shown in the figure in a PWM (Pulse Width Modulation) control mode. In detail, the direct-to-alternating-current conversion circuit 60 has six switching elements 61a to 66a and six freewheeling diodes 61b to 66b. The six switching elements 61a to 66a are connected in a bridge shape. In detail, the direct-to-alternating-current conversion circuit 60 includes three switching legs connected between its first input node 60a and the second input node 60b. The switching arm is formed by two switching elements 61a to 66a connected in series with each other. The first input node 60a is connected to the other end of the main winding 30, and the second input node 60b is connected to the second output end 20e of the rectifier circuit 20.

[0043] In each of the three switching arms, the midpoint between the switching elements 61a to 63a of the upper arm and the switching elements 64a to 66a of the lower arm is connected to each phase coil (coil of u phase, v phase, and w phase) of the load 3. Each switching element 61a to 66a is connected in reverse parallel to a freewheeling diode 61b to 66b. Each switching element 61a to 66a is composed of an IGBT (Insulated Gate Bipolar Transistor). However, each switching element 61a to 66a can also be composed of a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) containing a wide bandgap semiconductor such as silicon carbide (SiC) or gallium nitride (GaN).

[0044] The capacitor 70 is connected between the first input node 60a and the second input node 60b of the direct-to-alternating-current conversion circuit 60. The capacitor 70 is a film capacitor or a ceramic capacitor. The electrostatic capacitance of the film capacitor and the ceramic capacitor is generally smaller than the electrostatic capacitance of the electrolytic capacitor, so the capacitor 70 cannot sufficiently smooth the output voltage of the rectifier circuit 20. In other words, the capacitor 70 allows the pulsation of the output voltage of the rectifier circuit 20. Therefore, the voltage between the first input node 60a and the second input node 60b of the direct-to-alternating-current conversion circuit 60 has a pulsating component. The rectifier circuit 20 performs full-wave rectification, so the frequency of the pulsating component becomes 2N times the frequency of the AC voltage output by the power supply 2 (N is the number of phases of the power supply 2).

[0045] Here, when the inductance of the main winding 30 is set to L (H), the carrier frequency of the PWM control of the DC-AC conversion circuit 60 is set to fc (Hz), the electrostatic capacitance of the capacitor 70 is set to C (F), and the value of the constant K is set to 1 / 4, the inductance of the main winding 30 and the electrostatic capacitance of the capacitor 70 are set so that the following equation 1 holds.

[0046] [Mathematical formula 1]

[0047]

[0048] Thus, the switching noise generated in the DC-AC conversion circuit 60 can be absorbed by the main winding 30 and the capacitor 70. Here, by using a power MOSFET that can switch at high speed and includes silicon carbide or gallium nitride in each switching element 61a to 66a, the carrier frequency fc can be increased, and the inductance of the main winding 30 and the electrostatic capacitance of the capacitor 70 can be reduced.

[0049] When the power supply voltage of the power supply 2 is Vac (V) and the maximum power consumption of the load 3 is Pmax (W), the electrostatic capacitance of the capacitor 70 is set so that the following Expression 2 holds true.

[0050] [Mathematical formula 2]

[0051]

[0052] By setting the capacitance of the capacitor 70 in this manner, the fifth and seventh harmonics from the rectifier circuit 20 can be reduced.

[0053] Figure 2 A power conversion device 1 according to a comparative example is shown. In this comparative example, the auxiliary winding 41 is not provided on the bypass path 40 of the power conversion device 1. The other configurations are the same as those of the first embodiment.

[0054] exist Figure 3 , the voltage Vb at both ends of the bypass path 40, the input voltage V DC , the voltage V of the main winding 30 L , and the current Im of the main winding 30. Figure 4 In the figure, the voltage Vb at both ends of the bypass path 40 and the input voltage Vb of the main circuit unit 50 in the first embodiment are shown in order from the top by solid lines. DC , the voltage V of the main winding 30 L , the current Im of the main winding 30, and the current Is of the auxiliary winding 41. Figure 4 In the figure, the voltage Vb at both ends of the bypass path 40 and the input voltage V DC , the voltage V of the main winding 30 L, and the current Im of the main winding 30. Figure 3 and Figure 4 The voltages and currents shown are the voltages and currents during a period in which the switching operation of the switching elements 61a to 66a of the inverter circuit 60 is stopped by the control of a control device (not shown). Figure 3 and Figure 4 In FIG. 1 , Vmax shows the peak value of the power supply voltage supplied by the power supply 2 when no lightning surge occurs.

[0055] In the first embodiment, when a lightning surge occurs, Figure 4 As shown by the arrows in , the voltage Vb at both ends of the bypass path 40 rises. In response, the current Im including the lightning surge current flows through the main winding 30, and the charge is gradually accumulated in the capacitor 70, thereby increasing the input voltage V DC Rise. Here, the lightning surge current is a current superimposed on the current flowing due to the voltage normally supplied from the power supply 2. The lightning surge current flows when the voltage of the power supply 2 rises due to the occurrence of a lightning surge. In addition, a portion of the current including the lightning surge current flows as a current Is through the bypass path 40 including the auxiliary winding 41, thereby reducing the current flowing from the power supply 2 and the power supply unit 10 to the main circuit unit 50, wherein the above-mentioned lightning surge current is superimposed on the current from the power supply 2. The current Is flows through the bypass path 40, whereby the auxiliary winding 41 uses the electric energy sent to the bypass path 40 to change the magnetic flux passing through the main winding 30, and generates the following voltage between the main winding 30, that is, the power supply 2 and the main circuit unit 50, which is a voltage that suppresses the current including the lightning surge current from flowing in the direction of the main circuit unit 50. As a result, the equivalent impedance between the power supply 2 and the main circuit unit 50 increases. Therefore, as Figure 4 As shown in the portion surrounded by the double-dashed line, in the first embodiment, when a lightning surge occurs and the current Is flows through the bypass path 40, the voltage V of the main winding 30 L In addition, Figure 4 As shown by the arrow in the middle, the current Im of the main winding 30 is smaller than that of the comparative example. As a result, the input voltage V DC Therefore, compared with the comparative example, the main circuit unit 50 is less likely to be destroyed by the lightning surge.

[0056] In the first embodiment, compared with the comparative example, when the lightning surge current is superimposed on the current from the power source 2, the current flowing from the power source 2 to the main winding 30 and the capacitor 70 can be reduced. Therefore, compared with the comparative example, the main winding 30 and the capacitor 70 can be miniaturized.

[0057] In the first embodiment, since the electric energy of the lightning surge current can be used to suppress the lightning surge current from intruding into the main circuit unit 50 , the electric energy can be effectively used.

[0058] In the first embodiment, since the varistor 42 is provided on the bypass path 40, it is possible to limit the current flowing through the bypass path 40 when no lightning surge occurs. On the other hand, when a lightning surge occurs, since the surge absorber 42 is short-circuited, the current can flow through the bypass path 40. Therefore, since it is not necessary to control whether the current flows through the bypass path 40 by a computer, the delay time from the occurrence of the lightning surge to the current flowing to the bypass path 40 can be shortened.

[0059] exist Figure 3 and Figure 4 , the voltages and currents during the period when the switching operation of the switching elements 61a to 66a is stopped are illustrated. During the period when the switching operation of the switching elements 61a to 66a is stopped, the charge of the capacitor 70 does not flow to the load 3, so the input voltage V DC However, when the switching elements 61a to 66a are switched to supply current to the load 3, the current flowing from the power supply 2 to the main winding 30 and the capacitor 70 when a lightning surge occurs can be reduced.

[0060] (Modification of the first embodiment)

[0061] Figure 5 A power conversion device 1 according to a modified example of the first embodiment of the present disclosure is shown. In this modified example, one end of the main winding 30 is connected to the second output terminal 20e of the rectifier circuit 20, and the other end of the main winding 30 is connected to the second input node 60b of the direct-to-alternating-current conversion circuit 60. In addition, the first input node 60a of the direct-to-alternating-current conversion circuit 60 is connected to the first output terminal 20d of the rectifier circuit 20. On the bypass path 40, an auxiliary winding 41 and a varistor 42 are sequentially provided from the second output terminal 20e side.

[0062] Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0063] (Second Embodiment)

[0064] Figure 6 A power conversion device 1 according to a second embodiment of the present disclosure is shown. In the second embodiment, the first to third main windings 30 a to 30 c and the first to third bypass paths 40 a to 40 c are provided between the power source 2 and the rectifier circuit 20 .

[0065] In detail, the first main winding 30a is disposed between the power source 2 and the first input terminal 20a of the rectifier circuit 20, that is, on the first power line L1.

[0066] The second main winding 30b is disposed between the power source 2 and the second input terminal 20b of the rectifier circuit 20, that is, on the second power line L2.

[0067] The third main winding 30c is arranged between the power source 2 and the third input terminal 20c of the rectifier circuit 20, that is, on the third power line L3.

[0068] As the bypass path 40 , first to third bypass paths 40 a to 40 c are provided.

[0069] One end of the first bypass path 40a is connected to the first power line L1 at a position closer to the power source 2 than the first main winding 30a. On the other hand, the other end of the first bypass path 40a is connected to the second power line L2 at a position closer to the rectifier circuit 20 than the second main winding 30b. The auxiliary winding 41 and the varistor 42 of the first bypass path 40a are connected in sequence from the first power line L1 side.

[0070] One end of the second bypass path 40b is connected to the second power line L2 at a position closer to the power source 2 than the second main winding 30b. On the other hand, the other end of the second bypass path 40b is connected to the third power line L3 at a position closer to the rectifier circuit 20 than the third main winding 30c. The auxiliary winding 41 and the varistor 42 of the second bypass path 40b are connected in sequence from the second power line L2 side.

[0071] One end of the third bypass path 40c is connected to the third power line L3 at a position closer to the power source 2 than the third main winding 30c. On the other hand, the other end of the third bypass path 40c is connected to the first power line L1 at a position closer to the rectifier circuit 20 than the first main winding 30a. The auxiliary winding 41 and the varistor 42 of the third bypass path 40c are connected in sequence from the third power line L3 side.

[0072] Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0073] (Third Embodiment)

[0074] Figure 7A power conversion device 1 according to a third embodiment of the present disclosure is shown. In the third embodiment, the power supply 2 is a single-phase AC power supply. Therefore, the rectifier circuit 20 includes only a first input terminal 20a connected to the first power line L1 and a second input terminal 20b connected to the second power line L2 as input terminals. In addition, the number of diodes 21 to 24 provided in the rectifier circuit 20 is four. The main winding 30 is provided between the power supply 2 and the rectifier circuit 20. That is, the rectifier circuit 20 is connected to the power supply 2 via the main winding 30.

[0075] In detail, the main winding 30 is disposed on the first power line L1 , that is, between the power source 2 and the first input terminal 20 a of the rectifier circuit 20 .

[0076] One end of the bypass path 40 is connected to the first power line L1 at a position closer to the power source 2 than the main winding 30. On the other hand, the other end of the bypass path 40 is connected to the second power line L2. An auxiliary winding 41 and a varistor 42 are connected in order from the first power line L1 side.

[0077] The capacitance of the capacitor 70 is set so as to allow the output voltage of the rectifier circuit 20 to pulsate so that the maximum value is twice or more the minimum value.

[0078] Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0079] (Variation of the Third Embodiment)

[0080] Figure 8 The power conversion device 1 according to the modified example of the third embodiment of the present disclosure is shown. In this modified example, the main winding 30 is provided on the second power line L2, that is, between the power source 2 and the second input terminal 20b of the rectifier circuit 20. In addition, one end of the bypass path 40 is connected to the second power line L2 at a position closer to the power source 2 than the main winding 30. On the other hand, the other end of the bypass path 40 is connected to the first power line L1. An auxiliary winding 41 and a varistor 42 are connected in sequence from the second power line L2 side.

[0081] Since the other configurations are the same as those of the third embodiment, the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0082] (Fourth Embodiment)

[0083] Fig. 9 A power conversion device 1 according to a fourth embodiment of the present disclosure is shown. In the fourth embodiment, the power supply 2 is a DC power supply. In addition, the power supply unit 10 does not include the rectifier circuit 20.

[0084] Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0085] It should be noted that in the first embodiment, the power supply 2 may be a single-phase AC power supply, and the rectifier circuit 20 may be the rectifier circuit 20 of the third embodiment, that is, the rectifier circuit 20 having four diodes 21 to 24 .

[0086] It should be noted that in the first to fourth embodiments and the modified examples of the first and third embodiments, other power conversion circuits may be provided in place of the direct-to-alternating-current conversion circuit 60, such as a DC-DC converter having a function of performing power conversion such as stepping up or stepping down a direct-current voltage through a switching action. Moreover, the power conversion circuit may also constitute the main circuit unit 50.

[0087] In the first to fourth embodiments and the modified examples of the first and third embodiments, the main circuit unit 50 has the power conversion function performed by the inverter circuit 60 , but the main circuit unit 50 may not have the power conversion function.

[0088] In the first to fourth embodiments and the modified examples of the first and third embodiments, the diodes 21 to 26 may be replaced with IGBTs or power MOSFETs including wide-bandgap semiconductors such as silicon carbide and gallium nitride to form part or all of the rectifier circuit 20 .

[0089] The above embodiments and modifications are described, but it should be understood that various changes can be made to their forms and details without departing from the spirit and scope of the claims. As long as the functions of the objects of the present disclosure are not affected, the above embodiments and modifications can also be appropriately combined or replaced.

[0090] - Industrial Applicability -

[0091] As described above, the present disclosure is useful as a circuit including a power supply unit and a main circuit unit to which electric power is supplied from a power source via the power supply unit.

[0092] - Explanation of symbols -

[0093] 1 Power conversion device

[0094] 2 Power supply

[0095] 10 Power supply

[0096] 11 Impedance Rising Circuit

[0097] 20 Rectification circuit

[0098] 30 Main winding

[0099] 40 Bypass path

[0100] 41 Auxiliary winding

[0101] 42 Varistor (surge absorber)

[0102] 50 Main circuit

[0103] 60 DC to AC conversion circuit

[0104] 60a First input node

[0105] 60b Second input node

[0106] 70 Capacitors

Claims

1. A circuit, comprising a power supply unit (10) and a main circuit unit (50), wherein power is supplied from a power supply (2) via the power supply unit (10) to the main circuit unit (50), characterized in that: The power supply unit (10) includes a bypass path (40, 40a-40c) through which a portion of a current including a lightning surge current flows, the lightning surge current being a current superimposed on a current from the power supply (2), and The power supply unit (10) includes an impedance increasing circuit (11) which increases the equivalent impedance between the power supply (2) and the main circuit unit (50) according to the current flowing through the bypass path (40, 40a-40c).

2. The circuit according to claim 1, characterized in that: When a part of the current including the lightning surge current flows through the bypass path (40, 40a to 40c), the impedance increasing circuit (11) increases the impedance using the electric energy sent to the bypass path (40, 40a to 40c).

3. The circuit according to claim 1 or 2, characterized in that: The impedance increasing circuit (11) generates a voltage between the power supply (2) and the main circuit unit (50) for suppressing the current flowing toward the main circuit unit (50) based on the current flowing through the bypass path (40, 40a-40c), the current including the lightning surge current.

4. The circuit according to any one of claims 1 to 3, characterized in that: The impedance increasing circuit (11) comprises a main winding (30) and an auxiliary winding (41). The main winding (30) is provided on a path for supplying electric power from the power source (2) to the main circuit unit (50), the auxiliary winding (41) is provided on the bypass path (40) and is magnetically coupled to the main winding (30), and the impedance increasing circuit (11) generates the voltage by causing a part of the current including the lightning surge current to flow through the auxiliary winding (41), thereby causing a magnetic flux passing through the main winding (30) to change.

5. The circuit according to claim 4, characterized in that: A surge absorber (42) connected in series with the auxiliary winding (41) is provided on the bypass path (40, 40a-40c).

6. The circuit according to claim 4 or 5, characterized in that: The polarity directions of the main winding (30) and the auxiliary winding (41) are the same as each other.

7. The circuit according to any one of claims 1 to 6, characterized in that: The power source (2) is an AC power source, The power supply unit (10) includes a rectifier circuit (20) for rectifying the alternating current output from the power supply (2). The main circuit unit (50) includes a DC-AC conversion circuit (60) and a capacitor (70). The DC-AC conversion circuit (60) converts the DC output from the rectifier circuit (20) into AC through a switching action. The capacitor (70) is connected between input nodes (60a, 60b) of the DC-AC conversion circuit (60) to allow pulsation of the output voltage of the rectifier circuit (20).

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