Power supply circuit and motor unit

Abstract

One embodiment of the power supply circuit of the present invention is a power supply circuit converting an AC input into a DC output, comprising: a common mode choke having a first coil and a second coil that are magnetically coupled, one end of each of the first coil and the second coil being electrically connected to the AC input; a rectifying circuit electrically connected to the other end of each of the first coil and the second coil and rectifying an AC input to a DC output; a smoothing circuit that smoothes the DC voltage output from the rectifying circuit via the pair of wirings; a first capacitor; a second capacitor; and a main body ground terminal electrically connected to an external metal member, the first capacitor is electrically connected between one end of the first coil and one end of the second coil, and the second capacitor is electrically connected between the main body ground terminal and the other of the pair of wirings having a lower potential than the one of the wirings.

Description

Technical Field

[0001] The invention relates to a power supply circuit and a motor unit. Background Art

[0002] In a power supply circuit that converts a single-phase AC voltage supplied from a commercial AC power supply into a DC voltage, it is necessary to reduce both noise intruding from the commercial AC power supply to the power supply circuit and noise intruding from a load of the power supply circuit to the power supply circuit. For example, Patent Document 1 discloses a power supply circuit that includes an input filter composed of a line filter transformer and four capacitors in order to attenuate external noise and prevent high-frequency noise generated by an electrical device connected to the power supply circuit from escaping through an AC line. [Prior art literature] [Patent Document]

[0003] Patent Document 1: Japanese Patent No. 3116565 Summary of the invention

[0004] The input filter included in the power supply circuit of Patent Document 1 is composed of a line filter transformer and four capacitors, and therefore the cost increases due to the increase in the number of parts.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply circuit that can achieve a high noise suppression effect with a relatively simple structure and a motor unit including the power supply circuit.

[0006] One embodiment of the power supply circuit of the present invention is a power supply circuit that converts AC input into DC output, including: a common mode choke, the common mode choke having a first coil and a second coil that are magnetically coupled, one end of each of the first coil and the second coil being electrically connected to the AC input; a rectifier circuit, the rectifier circuit being electrically connected to the other end of each of the first coil and the second coil, and rectifying the AC input into the DC output; a smoothing circuit, the smoothing circuit smoothing a DC voltage output from the rectifier circuit via a pair of wirings; a first capacitor; a second capacitor; and a main body grounding terminal, the main body grounding terminal being electrically connected to an external metal component, the first capacitor being electrically connected between the one end of the first coil and the one end of the second coil, and the second capacitor being electrically connected between the other wiring of the pair of wirings having a lower potential than one wiring and the main body grounding terminal.

[0007] One embodiment of the motor unit of the present invention includes: a DC motor; a power supply circuit of the above embodiment; a drive circuit, which uses a DC voltage output from the power supply circuit to generate a drive voltage for driving the DC motor and outputs the drive voltage to the DC motor; and a control circuit, which outputs a control signal for generating the drive voltage to the drive circuit.

[0008] According to the above-described aspects of the present invention, there are provided a power supply circuit capable of achieving a high noise suppression effect with a relatively simple structure and a motor unit including the power supply circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 : is a block diagram showing the structure of the motor unit according to the present embodiment. Figure 2 : is a circuit diagram showing the configuration of a power supply circuit in this embodiment. (Explanation of symbols) 1…motor unit, 2…power supply circuit, 3…drive circuit, 4…control circuit, 5…DC motor, 10…common mode choke, 11…first coil, 12…second coil, 20…fuse, 30…first capacitor, 40…varistor, 51…first surge absorption element, 52…second surge absorption element, 60…rectifier circuit, 70…smoothing circuit, 80…bypass circuit, 81…varistor, 82…lightning arrester, 90…second capacitor, L1…first AC line, L2…second AC line, L3…first DC line, L4…second DC line, P1…first AC input terminal, P2…second AC input terminal, P3…first DC output terminal, P4…second DC output terminal, P5…body ground terminal. DETAILED DESCRIPTION

[0010] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 1 is a block diagram showing the structure of the motor unit 1 of the present embodiment. Figure 1 As shown, the motor unit 1 includes a power supply circuit 2, a drive circuit 3, a control circuit 4, and a DC motor 5. The motor unit 1 uses a single-phase AC voltage supplied from a commercial AC power supply (not shown) via a two-core power cable 6 as a power supply voltage. The two-core power cable 6 has a power line 7 electrically connected to the L terminal of the commercial AC power supply, and a neutral line 8 electrically connected to the N terminal of the commercial AC power supply.

[0011] The power circuit 2 converts AC input from a commercial AC power source into DC output. More specifically, the power circuit 2 converts a single-phase AC voltage supplied from a commercial AC power source via a two-core power cable 6 into a DC voltage, and outputs the DC voltage to the drive circuit 3. The power circuit 2 includes a first AC input terminal P1, a second AC input terminal P2, a first DC output terminal P3, a second DC output terminal P4, and a main body ground terminal P5.

[0012] The first AC input terminal P1 is electrically connected to the power line 7. The second AC input terminal P2 is electrically connected to the neutral line 8. That is, a single-phase AC voltage is input to the power circuit 2 from the commercial AC power supply via the first AC input terminal P1 and the second AC input terminal P2.

[0013] The first DC output terminal P3 and the second DC output terminal P4 are respectively electrically connected to the drive circuit 3. The power supply circuit 2 outputs a DC voltage to the drive circuit 3 through the first DC output terminal P3 and the second DC output terminal P4.

[0014] The main body ground terminal P5 is electrically connected to an external metal component (illustration omitted). For example, the metal component electrically connected to the main body ground terminal P5 is a metal housing that contains the power supply circuit 2. The metal housing that contains the power supply circuit 2 may also be the housing of the motor unit 1. The power supply circuit 2 is electrically connected to a metal component such as a metal housing via the main body ground terminal P5.

[0015] The drive circuit 3 generates a drive voltage for driving the DC motor 5 using the DC voltage output from the power circuit 2, and outputs the drive voltage to the DC motor 5. For example, the drive circuit 3 is a three-phase full-bridge circuit composed of six power semiconductor switch components. The drive circuit 3 converts the DC voltage supplied from the power circuit 2 into a three-phase AC voltage, and outputs the three-phase AC voltage to the DC motor 5 as the drive voltage.

[0016] The control circuit 4 outputs a control signal for generating a driving voltage to the driving circuit 3. The control circuit 4 controls the on-operation and off-operation of each power semiconductor switch component by outputting a control signal to each of the six power semiconductor switch components.

[0017] For example, the control circuit 4 receives a speed command signal from a higher-level control device (not shown), and outputs a control signal to the drive circuit 3 to rotate the DC motor 5 at a target speed indicated by the speed command signal. For example, the control circuit 4 is a processor having a built-in memory (not shown). As an example, the control circuit 4 is a microcontroller unit (MCU) and controls the drive circuit 3 according to a program pre-stored in a memory.

[0018] The DC motor 5 rotates according to the driving voltage supplied from the driving circuit 3. For example, the DC motor 5 is a three-phase brushless DC motor that rotates according to the three-phase AC voltage supplied from the driving circuit 3.

[0019] Below, refer to Figure 2 , the structure of the power supply circuit 2 in this embodiment is described in detail. Figure 2 2 is a circuit diagram showing the structure of the power supply circuit 2. Figure 2 As shown, the power supply circuit 2 includes: a common mode choke 10, a fuse 20, a first capacitor 30, a varistor 40, a first surge absorption element 51, a second surge absorption element 52, a rectifier circuit 60, a smoothing circuit 70, a bypass circuit 80, a second capacitor 90, a first AC line L1, a second AC line L2, a first DC line L3, and a second DC line L4.

[0020] The common mode choke coil 10 has a magnetically coupled first coil 11 and a second coil 12. One end of the first coil 11 is electrically connected to one end of the first AC line L1. The other end of the first AC line L1 is electrically connected to the first AC input terminal P1 via the fuse 20. That is, one end of the first coil 11 is electrically connected to the first AC input terminal P1 via the first AC line L1 and the fuse 20.

[0021] One end of the second coil 12 is electrically connected to one end of the second AC line L2. The other end of the second AC line L2 is electrically connected to the second AC input terminal P2. That is, one end of the second coil 12 is electrically connected to the second AC input terminal P2 via the second AC line L2. In this way, the first AC line L1 and the second AC line L2 are a pair of wiring that transmits the single-phase AC voltage input to the power supply circuit 2 via the two-core power supply cable 6 to the common mode choke coil 10.

[0022] The other end of each of the first coil 11 and the second coil 12 is electrically connected to the rectifier circuit 60. Specifically, the other end of the first coil 11 is electrically connected to the anode terminal of the first diode 61 included in the rectifier circuit 60. The other end of the second coil 12 is electrically connected to the anode terminal of the third diode 63 included in the rectifier circuit 60.

[0023] The first capacitor 30 is electrically connected between one end of the first coil 11 and one end of the second coil 12. Specifically, one end of the first capacitor 30 is electrically connected to one end of the first coil 11 via the first AC line L1, and the other end of the first capacitor 30 is electrically connected to one end of the second coil 12 via the second AC line L2. For example, the first capacitor 30 is a film capacitor.

[0024] The varistor 40 is electrically connected in parallel with the first capacitor 30. Specifically, one end of the varistor 40 is electrically connected to one end of the first coil 11 via the first AC line L1, and the other end of the varistor 40 is electrically connected to one end of the second coil 12 via the second AC line L2. The varistor 40 is arranged in the front stage of the first capacitor 30.

[0025] The first surge absorbing element 51 and the second surge absorbing element 52 are elements for absorbing surge voltage. Specifically, the surge absorbing element of the present embodiment has the property of functioning as an insulator when a voltage below a predetermined value is applied, and functioning as a conductor when a voltage exceeding the predetermined value is applied.

[0026] The first surge absorbing element 51 is electrically connected in parallel with the first coil 11 . Specifically, one end of the first surge absorbing element 51 is electrically connected to one end of the first coil 11 , and the other end of the first surge absorbing element 51 is electrically connected to the other end of the first coil 11 .

[0027] The second surge absorbing element 52 is electrically connected in parallel with the second coil 12 . Specifically, one end of the second surge absorbing element 52 is electrically connected to one end of the second coil 12 , and the other end of the second surge absorbing element 52 is electrically connected to the other end of the second coil 12 .

[0028] As an example, the first surge absorbing element 51 and the second surge absorbing element 52 are lightning arresters. As another example, the first surge absorbing element 51 and the second surge absorbing element 52 may be varistors.

[0029] The rectifier circuit 60 rectifies a single-phase AC voltage input from the first AC input terminal P1 and the second AC input terminal P2 via the common mode choke coil 10 into a DC voltage. The rectifier circuit 60 includes a first diode 61 , a second diode 62 , a third diode 63 , and a fourth diode 64 .

[0030] The anode terminal of the first diode 61 is electrically connected to the other end of the first coil 11, the other end of the first surge absorbing element 51, and the cathode terminal of the second diode 62. The anode terminal of the third diode 63 is electrically connected to the other end of the second coil 12, the other end of the second surge absorbing element 52, and the cathode terminal of the fourth diode 64.

[0031] The cathode terminal of the first diode 61 is electrically connected to the cathode terminal of the third diode 63 and one end of the first DC line L3. The anode terminal of the second diode 62 is electrically connected to the anode terminal of the fourth diode 64 and one end of the second DC line L4.

[0032] The other end of the first DC line L3 is electrically connected to the first DC output terminal P3. The other end of the second DC line L4 is electrically connected to the second DC output terminal P4. Thus, the first DC line L3 and the second DC line L4 are a pair of wirings that transmit a DC voltage from the rectifying circuit 60 to the smoothing circuit 70.

[0033] The smoothing circuit 70 smoothes the DC voltage output from the rectifying circuit 60. The smoothing circuit 70 includes a third capacitor 71 and a fourth capacitor 72. The third capacitor 71 is electrically connected between the first DC line L3 and the second DC line L4. For example, the third capacitor 71 is an electrolytic capacitor. The fourth capacitor 72 is electrically connected between the first DC line L3 and the second DC line L4, and is arranged at a subsequent stage of the third capacitor 71.

[0034] The bypass circuit 80 includes a varistor 81 and a lightning arrester 82 electrically connected in series between the first DC line L3 and the second DC line L4. One end of the varistor 81 is electrically connected to the first DC line L3. One end of the lightning arrester 82 is electrically connected to the other end of the varistor 81, and the other end of the lightning arrester 82 is electrically connected to the second DC line L4. The bypass circuit 80 is configured between the rectifier circuit 60 and the smoothing circuit 70.

[0035] The second capacitor 90 is electrically connected between the second DC line L4 having a lower potential than the first DC line L3 and the main body ground terminal P5. That is, the second DC line L4 is electrically connected to a metal component such as a metal case of the built-in power supply circuit 2 via the second capacitor 90 and the main body ground terminal P5. For example, the second capacitor 90 is a ceramic capacitor.

[0036] In the power supply circuit 2 configured as described above, the noise that invades from the subsequent stage of the smoothing circuit 70 and is transmitted to the rectifier circuit 60 can be released to the metal parts such as the metal case of the built-in power supply circuit 2 via the second capacitor 90 and the main body ground terminal P5. In addition, the noise that is transmitted from the rectifier circuit 60 to the commercial AC power supply side via the common mode choke coil 10 can be reduced by the filter circuit composed of the common mode choke coil 10 and the first capacitor 30.

[0037] In the power supply circuit 2 configured as described above, when a common mode lightning surge voltage enters the power supply circuit 2 from the first AC input terminal P1 via the power supply line 7 of the two-core power supply cable 6 , the lightning surge voltage is transmitted to the first coil 11 of the common mode choke coil 10 via the first AC line L1 .

[0038] In this case, since the first surge absorbing element 51 is electrically connected in parallel with the first coil 11, the lightning surge voltage does not pass through the first coil 11, but is transmitted to the rectifier circuit 60 via the first surge absorbing element 51. The lightning surge voltage transmitted to the rectifier circuit 60 via the first surge absorbing element 51 is transmitted to the first DC line L3 via the first diode 61.

[0039] On the other hand, when a common mode lightning surge voltage enters the power supply circuit 2 from the second AC input terminal P2 via the neutral line 8 of the two-core power cable 6 , the lightning surge voltage is transmitted to the second coil 12 of the common mode choke coil 10 via the second AC line L2 .

[0040] In this case, since the second surge absorbing element 52 is electrically connected in parallel with the second coil 12, the lightning surge voltage does not pass through the second coil 12, but is transmitted to the rectifier circuit 60 via the second surge absorbing element 52. The lightning surge voltage transmitted to the rectifier circuit 60 via the second surge absorbing element 52 is transmitted to the first DC line L3 via the third diode 63.

[0041] The lightning surge voltage transmitted to the first DC line L3 is transmitted to the second DC line L4 via the bypass circuit 80 having the varistor 81 and the arrester 82. The lightning surge voltage transmitted to the second DC line L4 is transmitted to metal parts such as a metal case including the power supply circuit 2 via the second capacitor 90 and the body ground terminal P5.

[0042] As described above, when a common-mode lightning surge voltage invades the power supply circuit 2 from the commercial AC power supply via the two-core power supply cable 6, by transmitting the lightning surge voltage through the path described above, not only the first coil 11 and the second coil 12 of the common-mode choke 10 can be protected, but also the circuit elements arranged after the smoothing circuit 70 can be protected from the influence of the common-mode lightning surge voltage.

[0043] In addition, when a normal mode lightning surge voltage invades the power supply circuit 2 from the commercial AC power supply via the two-core power supply cable 6, the varistor 40 electrically connected between the first AC line L1 and the second AC line L2 absorbs the lightning surge voltage, thereby protecting each circuit element from the influence of the normal mode lightning surge voltage.

[0044] As described above, the power supply circuit 2 of the present embodiment is a power supply circuit 2 that converts AC input into DC output, and includes: a common mode choke 10, which has a magnetically coupled first coil 11 and a second coil 12, and one end of each of the first coil 11 and the second coil 12 is electrically connected to the AC input; a rectifier circuit 60, which is electrically connected to the other end of each of the first coil 11 and the second coil 12, and rectifies the AC input into a DC output; a smoothing circuit 70, which smoothes the DC voltage output from the rectifier circuit 60 via the first DC line L3 and the second DC line L4; a first capacitor 30; a second capacitor 90; and a main body ground terminal P5, which is electrically connected to an external metal part, the first capacitor 30 is electrically connected between one end of the first coil 11 and one end of the second coil 12, and the second capacitor 90 is electrically connected between the second DC line L4 having a lower potential than the first DC line L3 and the main body ground terminal P5.

[0045] In the power supply circuit 2 of the present embodiment as described above, the noise that invades from the subsequent stage of the smoothing circuit 70 and is transmitted to the rectifier circuit 60 can be released to the metal parts such as the metal case of the built-in power supply circuit 2 via the second capacitor 90 and the main body ground terminal P5. In addition, the noise that is transmitted from the rectifier circuit 60 to the commercial AC power supply side via the common mode choke coil 10 can be reduced by the filter circuit composed of the common mode choke coil 10 and the first capacitor 30. Therefore, according to the present embodiment, compared with the power supply circuit of Patent Document 1, it is possible to provide a power supply circuit 2 that can obtain a high noise suppression effect with a relatively simple structure.

[0046] In the power supply circuit 2 of the present embodiment, the first capacitor 30 is a film capacitor.

[0047] On the primary side of the power supply circuit 2 (previous stage of the rectifier circuit 60), since external surges are directly superimposed, it is required to use a non-smoking and non-flammable element with high withstand voltage and large capacity. Therefore, by using a film capacitor as the first capacitor 30, this requirement can be met.

[0048] In the power supply circuit 2 of the present embodiment, the second capacitor 90 is a ceramic capacitor.

[0049] On the secondary side of the power circuit 2 (the subsequent stage of the rectifier circuit 60 ), it is required to suppress high-frequency noise and suppress leakage current to the body ground line. Therefore, by using a ceramic capacitor as the second capacitor 90 , these requirements can be met.

[0050] The power supply circuit 2 of the present embodiment further includes a first surge absorption element 51 electrically connected in parallel with the first coil 11 , and a second surge absorption element 52 electrically connected in parallel with the second coil 12 .

[0051] In the power supply circuit of Patent Document 1, since the surge absorbing component is connected to only one of the same pole and the opposite pole before and after the common mode choke coil, only one of the two coils of the common mode choke coil can be protected from the influence of the lightning surge voltage. In contrast, according to the power supply circuit 2 of the present embodiment as described above, both the first coil 11 and the second coil 12 of the common mode choke coil 10 can be protected from the influence of the lightning surge voltage.

[0052] In the power supply circuit 2 of the present embodiment, the first surge absorbing element 51 and the second surge absorbing element 52 are lightning arresters.

[0053] According to the power supply circuit 2 of the present embodiment, both the first coil 11 and the second coil 12 of the common mode choke coil 10 can be effectively protected, in particular, from a relatively high lightning surge voltage of about several kV caused by a lightning strike.

[0054] In the power supply circuit 2 of the present embodiment, the first surge absorption element 51 and the second surge absorption element 52 may be varistors.

[0055] According to the power supply circuit 2 of the present embodiment described above, both the first coil 11 and the second coil 12 of the common mode choke coil 10 can be effectively protected, particularly from a relatively low lightning surge voltage of about several hundred V caused by a lightning strike.

[0056] The power supply circuit 2 of the present embodiment further includes a bypass circuit 80 including a varistor 81 and a lightning arrester 82 which are electrically connected in series between the first DC line L3 and the second DC line L4 .

[0057] According to the power supply circuit 2 of the present embodiment as described above, the lightning surge voltage sent to the output side (particularly the first DC line L3) of the rectifier circuit 60 via at least one of the first surge absorbing element 51 and the second surge absorbing element 52 can be bypassed to the second DC line L4 at the preceding stage of the smoothing circuit 70. The lightning arrester 82 has a characteristic of continuing and continuously flowing the current once it starts to flow, but can prevent the current from continuously flowing at the constant voltage set by the varistor 81. In addition, the lightning surge voltage that is bypassed to the second DC line L4 through the bypass circuit 80 at the front stage of the smoothing circuit 70 can be released to metal parts such as the metal shell of the built-in power supply circuit 2 via the second capacitor 90 and the main body grounding terminal P5, thereby protecting the circuit elements after the smoothing circuit 70 from the influence of the lightning surge voltage.

[0058] The motor unit 1 of this embodiment includes: a DC motor 5; a power supply circuit 2; a drive circuit 3, which uses the DC voltage output from the power supply circuit 2 to generate a drive voltage for driving the DC motor 5 and outputs the drive voltage to the DC motor 5; and a control circuit 4, which outputs a control signal for generating the drive voltage to the drive circuit 3.

[0059] As described above, the motor unit 1 of the present embodiment includes the power supply circuit 2 that achieves a high noise suppression effect with a relatively simple structure. Therefore, according to the present embodiment, there is provided a motor unit 1 that can achieve a high noise suppression effect with a relatively simple structure.

[0060] [Modifications] The present invention is not limited to the above-described embodiment, and the various configurations described in this specification can be appropriately combined within a range that does not contradict each other. For example, the following modified examples can be cited.

[0061] In the above embodiment, a three-phase brushless DC motor is exemplified as the DC motor 5 , but the DC motor of the present invention may be a DC motor other than a three-phase brushless DC motor. In addition, any one of the first AC line L1 , the second AC line L2 , the first DC line L3 , and the second DC line L4 may be passed through an inrush current suppression component (power thermistor). In the above embodiment, the power supply circuit 2 of the motor unit 1 is illustrated as the power supply circuit of the present invention, but the power supply circuit of the present invention can be widely used as a power supply circuit of an electronic device that uses a single-phase AC voltage supplied from a commercial AC power supply via a two-core power cable 6 as a power supply voltage.

[0062] Note that the present technology can adopt the following structures. (1) A power supply circuit for converting an AC input into a DC output, comprising: a common mode choke coil having a first coil and a second coil that are magnetically coupled, each having one end electrically connected to the AC input; a rectifier circuit electrically connected to the other end of each of the first coil and the second coil, and rectifying the AC input into the DC output; a smoothing circuit that smoothes a DC voltage output from the rectifier circuit via a pair of wirings; a first capacitor; a second capacitor; and a main body ground terminal electrically connected to an external metal component, the first capacitor electrically connected between the one end of the first coil and the one end of the second coil, and the second capacitor electrically connected between the other wiring of the pair of wirings having a lower potential than the other wiring and the main body ground terminal. (2) In the power supply circuit described in (1), the first capacitor is a film capacitor. (3) In the power supply circuit described in (1) or (2), the second capacitor is a ceramic capacitor. (4) The power supply circuit described in any one of (1) to (3) further includes: a first surge absorption element, the first surge absorption element being electrically connected in parallel with the first coil; and a second surge absorption element, the second surge absorption element being electrically connected in parallel with the second coil. (5) In the power supply circuit described in (4), the first surge absorbing element and the second surge absorbing element are lightning arresters. (6) In the power supply circuit described in (4), the first surge absorbing element and the second surge absorbing element are varistors. (7) The power supply circuit described in any one of (4) to (6) further includes a bypass circuit including a varistor and a lightning arrester electrically connected in series between the pair of wirings. (8) A motor unit comprising: a DC motor; a power supply circuit as described in any one of (1) to (7); a drive circuit, wherein the drive circuit uses the DC voltage output from the power supply circuit to generate a drive voltage for driving the DC motor and outputs the drive voltage to the DC motor; and a control circuit, wherein the control circuit outputs a control signal for generating the drive voltage to the drive circuit.

Claims

1. A power supply circuit that converts AC input into DC output, characterized in that: include: a common mode choke having a first coil and a second coil that are magnetically coupled, wherein one end of each of the first coil and the second coil is electrically connected to the AC input; a rectifier circuit, the rectifier circuit being electrically connected to the other end of each of the first coil and the second coil, and rectifying the AC input into the DC output; a smoothing circuit for smoothing a DC voltage output from the rectifying circuit via a pair of wirings; a first capacitor; a second capacitor; as well as A main body grounding terminal, the main body grounding terminal being electrically connected to an external metal component, The first capacitor is electrically connected between the one end of the first coil and the one end of the second coil, The second capacitor is electrically connected between the other wiring of the pair of wirings having a lower potential than the one wiring and the main body ground terminal.

2. The power supply circuit according to claim 1, characterized in that: The first capacitor is a film capacitor.

3. The power supply circuit according to claim 1, characterized in that: The second capacitor is a ceramic capacitor.

4. The power supply circuit according to claim 1, characterized in that: Also includes: a first surge absorbing element, the first surge absorbing element being electrically connected in parallel with the first coil; as well as A second surge absorbing element is electrically connected in parallel with the second coil.

5. The power supply circuit according to claim 4, characterized in that: The first surge absorbing element and the second surge absorbing element are lightning arresters.

6. The power supply circuit according to claim 4, characterized in that: The first surge absorbing element and the second surge absorbing element are varistors.

7. The power supply circuit according to claim 4, characterized in that: A bypass circuit including a varistor and a lightning arrester electrically connected in series between the pair of wirings is also included.

8. A motor unit, characterized in that: include: DC motor; The power supply circuit according to any one of claims 1 to 7; as well as a drive circuit that generates a drive voltage for driving the DC motor using the DC voltage output from the power supply circuit and outputs the drive voltage to the DC motor; as well as A control circuit outputs a control signal for generating the drive voltage to the drive circuit.

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