JP2000209742A - Electric circuit material and electrical junction box provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an electric circuit material that is applicable to various kinds of circuit shape by combining connecting unit materials with terminal unit materials. SOLUTION: As a bus bar that constitutes an internal circuit to be stored in an electric junction box, unit materials 12-1 to 12-7 provided with vertical parts including 12d-1 and horizontal parts equipped with 12e-1 are combined with connecting unit materials 11-1, 11-2 which are formed by cutting a continuous material of a certain width at a required length and by folding it back at required position to make it extend in a required horizontal direction, to fit a required circuit shape, and an electric circuit material 10 is formed by welding those materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric circuit member and an electric connection box provided with the electric circuit member.
The purpose is to provide versatility to the electric circuit material constituting the internal circuit so that it can be applied to different types of vehicles to be mounted, and to easily cope with circuit changes and the like.

[0002]

2. Description of the Related Art Conventionally, in an electric connection box in which a branch circuit is housed in a junction box or the like, a circuit may be formed at a high density by connecting electric wires and bus bars by pressure welding or the like. The bus bar is often used for a power supply circuit or the like where a large current flows.

For example, in the electric junction box shown in FIG. 12, an electric wire (single core wire) w-1 is laid inside the lower case 1 and the upper case 2 and arranged in the lowermost layer, and a first insulating plate is placed thereon. 6A, the bus bar 7, and the second insulating plate 6B are stacked and arranged, and the electric wire w-2 is arranged on the uppermost layer.
A slot 7A having a pressure contact blade at the tip protruding from the bus bar 7 is press-connected to the electric wires w-1 and w-2, and a connector 3 and a relay socket provided integrally with the lower case 1 and the upper case 2 are provided. Press-fit terminal 5 inside 4 etc.
And pressure terminals 5 and the like are arranged, and these press contact terminals 5 and the like are also connected to the electric wires w-1 and w-2 to form a high-density internal circuit.

[0004]

The busbar accommodated in the electric junction box is adapted to the shape of the internal circuit.
The conductive metal plate is stamped into the required shape, formed by bending and tapping, and the internal circuit differs depending on the vehicle type and specifications. Become. The above punching process is performed by a punching press machine using a die for punching,
Since this die is also required for each required shape to be punched out, various types of dies must be manufactured, which is very costly. Furthermore, even if the internal model is changed due to improvements, even if the vehicle type and specifications are the same, there is a problem that the shape of the busbar is constant, so it is not easy to respond to circuit changes. If this is not possible, it is necessary to manufacture a new bus bar, which requires time and effort for designing and the like, and has the problem of high cost.

[0005] The present invention has been made in view of the above problems, and instead of manufacturing a dedicated bus bar for each vehicle type and specification, an electric circuit material configured by combining basic single components is used as the bus bar. Accordingly, it is an object of the present invention to be able to easily cope with a change of a different vehicle type or a circuit at a low cost.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention refracts a bus bar for accommodating an internal circuit of an electric junction box into a vertical portion and a horizontal portion including a substantially L shape and a substantially U shape. In the shape provided, a single piece of terminal material with a terminal formed at the tip of the vertical part and a continuous material of a fixed width are cut at the required length, and these cut pieces are folded back at the required location and horizontally in the required direction. A single piece of material for connection is formed in combination, the single piece of connection is used as a continuous horizontal bus bar, and the horizontal portion of the single piece of terminal is connected to its required position by welding or rivets. Electrical circuit materials.

As described above, the bus bar is formed by combining the single terminal material and the single connection material, and the electric circuit material formed by welding or the like is the location where the bus bar is used.
By using the internal circuit at a location where a large current flows, the internal circuit can be configured without using a bus bar formed by conventional punching. Accordingly, various types of punching dies are not required, and the cost required for manufacturing the dies can be significantly reduced.

In addition, since the above-mentioned electric circuit materials are configured by combining individual materials based on the designed circuit,
If the circuit is configured so that these single materials can be shared,
It is possible to flexibly cope with various circuit shapes, and it is possible to provide versatility to different vehicle types and specifications. Further, it is possible to easily cope with circuit changes by appropriately combining the individual materials. In particular, since the single piece of connecting material constituting the electric circuit material is formed by folding a continuous material cut to a required length, the base portion of the electric circuit material can be easily adapted to the circuit shape. Can be formed.

The connection used for the combination of the above-mentioned single connection material and the single terminal material can be easily and reliably connected by welding such as resistance welding or laser welding or by using rivets. As a connection method other than the above, soldering may be used.

Further, the electric circuit material of the present invention provides a bus bar for accommodating an internal circuit of an electric junction box in a substantially L shape, a substantially U shape.
In the shape provided by refracting the vertical part and the horizontal part including the shape,
A single piece of terminal material with a terminal formed at the tip of the vertical part, and a continuous material of a certain width are cut at the required length, and these cut pieces are folded at required places, turned in the required direction in the horizontal direction, and bent in the vertical direction. The connecting single-piece material is formed in combination, and the horizontal portion of the terminal single-piece material is connected to a required position of the horizontal portion of the connecting single-piece material by welding or rivet.

[0011] As described above, by forming the base portion by folding the connecting single material constituting the electric circuit material in the horizontal and vertical directions, it is possible to cope with more various circuit shapes. The applicable range of the electric circuit material can be widened.

Further, the above-mentioned single terminal material is commonly used for various types of vehicles, and includes a tab having a substantially L-shaped vertical end and a slot provided with a press-contact blade at the substantially L-shaped vertical end. Chipped, substantially L-shaped vertical part with female terminal at the tip, horizontal part connected to the connecting piece of material, substantially U-shaped with vertical parts at both ends, and tabs at the ends of both vertical parts ,
It is preferable that the terminal is provided with one of a slot and a female terminal. As described above, by providing the tab at the end of the vertical portion of the single terminal material and directly inserting it into the connector such as the lower case, the connection circuit portion to the external circuit can be easily formed. Further, by providing a slot provided with a pressure contact blade at the tip of the other vertical portion, direct pressure connection with the electric wire inside the electric connection box can be made, so that an internal circuit with a different layer can be easily connected. Further, by providing a female terminal at the tip of another vertical portion, tabs such as electric circuit materials of different layers and tabs such as relays can be directly inserted, and various connections can be made directly.

[0013] Further, the plurality of connecting single members are overlapped in a linear, orthogonal or oblique direction and connected by welding or rivets, and the connecting single members are connected to required positions by the connecting form of the connecting single members. are doing. in this way,
Even if the circuit has a complicated shape, the base part of the electric circuit material can be formed corresponding to the complicated shape by connecting and connecting the individual parts for connection. Can be connected to a required position to form a required circuit. In addition, since the connection between the above-mentioned connected single-piece materials is performed by welding or rivets, it is possible to ensure connection reliability and the like. Other than the connection method described above, soldering may be used.

Further, the present invention provides an electric connection box containing the electric circuit material as a power supply circuit. By using the electric circuit material formed as described above as a power supply circuit, an internal circuit can be formed without using a bus bar for a conventional power supply circuit, which was required for manufacturing a mold and the like. Costs can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electric circuit member 10 according to the present invention. The electric circuit member 10 is a single connecting member 11-1, 11-2 and a vertical portion 12d used as a continuous horizontal bus bar.
-1 to 12d-7 and single terminal materials 12-1 to 12-7 having horizontal portions 12e-1 to 12e-7, respectively.

As shown in FIG. 2, the single connection material 11-1 is a continuous material D-1 which is a long conductive plate such as a brass plate or a copper alloy having a constant thickness t and a constant width w. It is cut to the required length, folded back at the required location, and formed horizontally in the required direction. The constant thickness t and the constant width w of the continuous material D-1 have a cross-sectional area enough to cope with a current value flowing through the conductive plate D-1, and are different from other connecting single materials or terminal single materials. When connecting, the dimensions are set to have a sufficient contact area. In addition, the required length to be cut is such that the length is cut in accordance with the designed circuit shape, and the turn is also made at the position corresponding to the circuit shape. Note that the connecting single-piece material 11-2 is also formed in the same manner as described above.

On the other hand, the terminal material 12-1 to 12-7
As shown in FIG. 1, there are a single terminal material 12-1 having a substantially L shape composed of a vertical portion and a horizontal portion, and a single terminal material 12-4 having a substantially U shape. In the case of the substantially L shape, the tips of the vertical portions 12d-1, 12d-5 and the like are connected to the tab 12a-1,
Single terminal materials 12-1 and 12-5, such as 2a-5
Single terminal material 12-2 or the like in which a slot 12b-2 or the like provided with a pressure contact blade at the tip of a vertical portion 12d-2 or the like is cut out.
Further, there is a type such as 12-6 having a female terminal portion 12c-6 at the end of the vertical portion. On the other hand, the single U-shaped terminal material 12-4 has a vertical portion 12d-
4, 12d-4, with a tab at one vertical end and a slot at the other end. In addition, another single U-shaped terminal material is provided with tabs 1 at the ends of both vertical portions.
2a, a slot 12b, and a female terminal 12c.

As shown in FIG. 3, the substantially L-shaped terminal material 12-1 and the like are formed by using a punching press or the like to form a single conductive plate D-2 made of a brass plate or a copper alloy. The sheet is punched into a required shape, bent, bent, and formed into a substantially L shape having a vertical portion 12d and a horizontal portion 12e. At the time of the above punching, those having the tab 12a at the tip on the side that becomes the vertical portion 12d are punched so as to form the tab 12a, and those having the press contact blade are punched so as to cut out the slot 12b. . In addition, those having a female terminal are punched into a shape capable of forming a female terminal.

Thereafter, a portion (hatched portion in the figure) which is not necessary for forming the circuit is cut to obtain a substantially L-shaped terminal material 12-.
1 and so on. After the above cutting, the female terminal is formed at the end of the vertical portion by bending or the like to form the female terminal. Note that the order of the above manufacturing procedure may be appropriately changed in consideration of workability and the like.

Further, the above-mentioned single U-shaped terminal material 12-
5A, etc., as shown in FIG. 4A, similarly to the above, the conductive plate D-2 ′ is formed into a substantially U shape by bending by punching and bending, and unnecessary portions (shaded lines in the drawing) ) Is cut into a substantially U-shape having two vertical portions 12d at both ends of a horizontal portion 12e. The positional relationship between the vertical portions 12d is not limited to the positional relationship facing each other as described above. For example, as shown in FIGS. 4B and 4C, the vertical portions 12d 'and 12d " May not be opposed.

The above substantially L-shaped or substantially U-shaped terminal single material 1
2-1 and the like are not limited to one vehicle type or specification, but are shared by other vehicle types. Standardization of the dimensions of the vertical portion 12d and the horizontal portion 12e further generalizes the use as standard parts. May be achieved. In addition, the shape of the single terminal material is not limited to the substantially L-shape or the substantially U-shape as described above, and the shape is not limited as long as the vertical and horizontal portions are provided.

The electric circuit member 10 shown in FIG. 1 is composed of the above-mentioned single connecting members 11-1 and 11-2 and a single terminal member 12-1.
In addition to using the connecting single-piece materials 11-1 and 11-2 as continuous horizontal bus bars, they are connected to the horizontal portion of the terminal single-piece material 12-1 or the like by welding at a required position matching the circuit shape. are doing. For details, single connection material 11
-1 and 11-2 are overlapped and welded in the orthogonal direction in accordance with the designed circuit shape to form a connection form of a base portion.
2-1 and the like are connected by welding to required positions corresponding to the designed circuit. In addition, the direction in which the single connecting materials are stacked is not limited to the orthogonal direction, and may be a linear direction or an oblique direction in accordance with a required circuit shape.

In the welding for connection and connection, for example, as shown in FIG. 5 (A), the connection single material 11-1 is brought into contact with the terminal single material 12-1 and the connection single material 11-2. The contact portion is welded by sandwiching the contact portion with a resistance welding electrode (not shown). Spot welding or the like is used for the resistance welding, and laser welding, ultrasonic welding, or the like may be used as another welding method.

FIG. 5 shows a connection method other than welding.
As shown in (B), connection may be made with rivets 13. When the rivet 13 is used, the insertion holes 11f-1 and 12f are used in the punching process at the time of manufacturing the connection single materials 11-1 and 11-2 and the terminal single material 12-1 and the like.
-1 and the like, and the insertion holes 11f-1 and 12f
The connecting single-piece material 11-1 and the terminal single-piece material 12-1 are overlapped so that f-1 communicates, and the rivet 13 is inserted into the insertion hole 1.
1f-1 and 12f-1 are inserted, and a rivet hammer (not shown) is used to form a fastening head for connection.
The connection with the connection single materials 11-1 and 11-2 and the other terminal single materials is also performed by rivets in the same manner as described above.
As a connection method other than the above, connection may be performed by soldering.

The electric circuit material 10 is not limited to the shape shown in FIG. 1, but is adapted to various designed circuit shapes, and the connection single material 11 and the terminal single material 12 are respectively formed. In combination, various shapes of electric circuit materials can be formed.

FIG. 6 shows an electric circuit material 10 'according to a modification of the present embodiment. In order to cope with a high-density internal circuit, horizontal portions 11e-2' and 11e-3 'and a second portion are provided. It has horizontal portions 11g-2 'and 11g-3'. The electric circuit material 10 'is a single connection material 11-1', 11-.
2 ', 11-3' and single material for terminal 12-1 'to 12
-9 'in combination.

The single connecting material 11-1 'is formed in the same manner as in the present embodiment, but the single connecting material 11-1' is used.
2 ′, as shown in FIG. 7, a continuous material D-1 ′ cut to a required length of a constant width is turned back at a required location and is directed in a required direction in a horizontal direction, and a horizontal portion is provided at a position corresponding to a circuit shape. Vertical part 1 refracted vertically from 11e-2 '
1d-2 'is provided, and the second horizontal portion 11g-2' is provided by being refracted in the horizontal direction again. In addition, the single piece material for connection 11-3 'is also the same as the horizontal part 1 as described above.
1e-3 'is refracted in the vertical direction to form a vertical portion 11d.
-3 ', and further refracted in the horizontal direction to provide a second horizontal portion 11g-3'.

On the other hand, the terminal materials 12-1 'to 12-
9 'is formed in a shape having a vertical portion and a horizontal portion including an L shape and a U shape, similarly to the above-described embodiment, and a tip of each of the vertical portions is provided with one of a tab, a slot, and a female terminal. Have. These connection single materials 11-1 'to 11-
Similarly to the present embodiment, the 3 'and the single terminal materials 12-1' to 12-9 'are combined and connected according to the circuit shape to form an electric circuit material 10' having a two-layer horizontal portion. Has formed. In addition, the electric circuit material 10 ′ is not limited to the shape shown in FIG. 6. For example, by providing a plurality of vertical portions in a single connecting material, a shape having two or more layers of horizontal portions is provided. Good.

FIG. 8 shows an electric connection box 20 containing the electric circuit material 10 of the present embodiment as a power supply circuit. The electric connection box 20 includes a lower case 21 and an upper case 2
The electric circuit member 10 is arranged between the lower electric wire w-1 and the upper electric wire w-2.

The lower case 21 and the upper case 22 shown in FIGS. 9 (A) and 9 (B) are formed of resin, and the lower surface 21a of the lower case 21 and the upper surface 22 of the upper case 22 are formed.
a has an opening 21b in which a connector 23, a relay socket 24, and a fuse socket 25 can be removably mounted and fixed;
22b-1, 22b-2 and 22b-3 are provided. Note that these openings 21b, 22b-1 and the like are shown in FIG.
The present invention is not limited to the state shown in (B), and may be provided as appropriate according to the number of connection points between the internal circuit and the external circuit housed in the electric connection box and the required number of relays and fuses. Further, an electronic control unit housing portion 22c is provided on a part of the upper surface 22a of the upper case 22.

FIGS. 10 (A), 10 (B) and 10 (C) show the opening 2
1b, connector 2 mounted on 22b-1 to 22b-3
3, a relay socket 24 and a fuse socket 25 are shown. The connector 23 shown in FIG. 10A is connected to the internal circuit by inserting the press contact terminal 26 and fitting a connector (not shown) for an external circuit into the connector fitting portion 23b. Further, a flange portion 23a is provided on the outer peripheral portion of the connector 23 for stability during mounting. The size of the connector 23 may be variously set in accordance with the number of terminals to be connected, and these dimensions may be set as standard dimensions in order to share the connector 23.

The relay socket 24 shown in FIG. 10B is a socket for inserting a relay (not shown), and has a relay insertion portion 24b on an upper surface and a flange portion 24a on an outer peripheral portion. Also,
A fuse socket 25 shown in FIG. 10C is a socket for inserting a fuse (not shown), and has a fuse insertion portion 2 at the top.
5b, a flange 25a is provided on the outer periphery in the same manner as described above.
Standard dimensions may be set in order to share the outer diameter of the relay socket 24 and the fuse socket 25 and the like.

The procedure for manufacturing the electric junction box 20 is as follows: first, the lower case 21 and the openings 21b, 22b of the upper case 22
-1, etc., a connector 23, a relay socket 24, and a fuse socket 25 are mounted and fixed. Also, due to the circuit configuration, there is no need to mount the connector 23, etc.
A closing lid 26 shown in FIG. 10D is attached to 22b-1 and the like to close the opening 21b and the like. If it is necessary to fix the connector 23 or the like more firmly, the connector 23 or the like may be fixed by welding or using an adhesive.

Next, as shown in FIG.
1 and the upper case 22 are arranged with a gap C therebetween with the inner surface facing upward, and the electric wire (single-core wire) w is drawn in a single stroke across the gap C along the inner surfaces of the lower case 21 and the upper case 22. Are connected to each other by press contact with a press contact terminal 26 attached to the lower case 21 and the upper case 22. After the electric wire w is wired in this manner, the electric wire w is cut at the gap C as shown by a two-dot chain line in the drawing, and separated into an electric wire w-1 on the lower case 21 side and an electric wire w-2 on the upper case 22 side. ing.

After cutting the electric wires as described above, as shown in FIG. 8, the electric circuit member 10 is arranged between the electric wires w-1 and w-2, and the tab 12a of the electric circuit member 10 is connected. The slot 12b is inserted into the electric wire w-
1, w-2, and the female terminal 12c is positioned below the relay socket 24 and the like, and the lower case 21 and the upper case 22 are combined to form the electric connection box 20. The connection between the electric wires w-1 and w-2 for forming the internal circuit of the electric connection box 20 is performed by the connection bus bar 2.
7 is performed.

As shown in FIG. 8, the connection bus bar 27 is formed in a required shape from a conductive plate and has a vertical portion 27a.
The upper and lower ends are bent at 90 degrees to form upper and lower horizontal portions 27b, 27
c, and press contact blades 27d and 27e are provided at the tips of the upper and lower horizontal portions 27b and 27c, respectively. The connection bus bar 27 is arranged along the side surfaces of the lower case 21 and the upper case 22 to connect the connection locking portions 21d on the side surfaces of the case.
22d, and the electric wire w-
1, w-2. Then, the protective cover 2
8 is attached.

An electronic control unit 30 composed of a printed circuit board having various electronic components is mounted in the electronic control unit housing portion 22c of the upper case 22, and a cover 29 having a connector 29a is mounted thereon. It is trying to centralize electrical components.

The procedure for manufacturing the electric junction box is not limited to the above, and the order may be appropriately changed in consideration of workability and the like. Further, the form of the electric connection box is not limited to the above-described form. For example, a connector or the like may be integrated with the lower case or the upper case to have a simple structure.
It is not always necessary to mount the electric control unit. Further, a plurality of electric wires and electric circuit materials may be arranged with an insulating plate or the like interposed therebetween to form a multi-layer laminated structure, and an electric circuit material having a large number of horizontal portions is used. You may. Further, the electric circuit material may be used not only for the power supply circuit but also for a circuit for other purposes in the internal circuit.

[0039]

As is apparent from the above description, the use of the electric circuit material of the present invention eliminates the need for a complicated mold corresponding to the electric circuit shape required for forming a conventional bus bar, and greatly Cost can be reduced. In addition, since the electric circuit material of the present invention is formed by combining a single component material for connection and a single component material for terminals, various combinations of circuit shapes can be accommodated by these combinations. Sharing can be achieved. Further, it is possible to easily cope with a circuit change or the like accompanying the improvement by changing a combination of the above-mentioned single materials. Further, by providing a single material for connection of an electric circuit material to have a plurality of horizontal portions, it is possible to easily cope with a higher-density internal circuit.

Also, in the electric connection box provided with the electric circuit material, the upper and lower electric wires are connected by the connecting bus bar, so that the electric connection box is easily manufactured and the lower case constituting the electric connection box is formed. By making connectors and other components detachable from the upper case, the above case can be made more versatile, and the flexibility of the electric circuit material is increased, and the versatility of the electric connection box itself is improved. Can be done. Furthermore, by allowing the electronic control unit to be accommodated in the upper case, electronic and electrical components that need to be connected to an external circuit can be centralized in the electrical junction box, and the wiring harness that is responsible for the connection of each circuit Performance can also be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an electric circuit material of the present invention.

FIG. 2 is a perspective view showing a manufacturing process of a single material for connection of an electric circuit material.

3A and 3B are a plan view and a perspective view, respectively, showing a manufacturing process of a single terminal material having a substantially L shape.

FIGS. 4A and 4B are a plan view and a perspective view, respectively, showing a manufacturing process of a single U-shaped terminal material; FIGS.
It is a perspective view which shows another single material for terminals of substantially U shape.

5A and 5B are perspective views showing a connection state between a connection single material and a terminal single material, and FIG.
(B) is a perspective view showing a connection state by rivets.

FIG. 6 is a perspective view showing an electric circuit material according to a modified example of the present invention.

FIG. 7 is a perspective view illustrating a manufacturing process of a single material for connecting electric circuit materials according to a modified example.

FIG. 8 is an exploded perspective view showing the electric connection box of the present invention.

9A is a perspective view of a lower case, and FIG. 9B is a perspective view of an upper case.

10A is a perspective view of a connector, FIG. 10B is a perspective view of a relay socket, FIG. 10C is a perspective view of a fuse socket, and FIG. 10D is a perspective view of a closing lid.

FIG. 11 is a perspective view illustrating a manufacturing process of the electric junction box.

FIG. 12 is an exploded perspective view showing a conventional electric junction box.

[Explanation of symbols]

 1, 21 Lower case 2, 22 Upper case 10, 10 'Electric circuit material 11-1, 11-2 Single material for connection 12-1 to 12-7 Single material for terminal w-1, w-2 Electric wire

Claims (5)

[Claims] 1. A bus bar housed as an internal circuit of an electric junction box, having a shape in which a vertical portion including a substantially L shape and a substantially U shape and a horizontal portion are bent and provided, and a terminal is formed at a tip of the vertical portion. Forming a single piece of terminal material and a single piece of connecting material that cuts a continuous material of a certain width at the required length and turns these cut pieces back at the required location to face the required direction in the horizontal direction. An electric circuit material comprising a single material for a terminal used as a continuous horizontal bus bar and a horizontal portion of the single material for a terminal connected to a required position by welding or rivets. 2. A bus bar to be housed as an internal circuit of an electric junction box, having a shape in which a vertical portion including a substantially L shape and a substantially U shape and a horizontal portion are bent and provided, and a terminal is formed at a tip of the vertical portion. Combination of a single piece of terminal material and a single piece of connecting material that cuts a continuous material of a certain width to the required length, turns these cut pieces at required places, turns them in the required direction in the horizontal direction, and refracts them in the vertical direction An electric circuit member formed by connecting a horizontal portion of the single terminal material by welding or a rivet to a required position of a horizontal portion of the single connection material. 3. The single terminal material is commonly used for various types of vehicles, and has a substantially L-shaped vertical portion with a tab at the tip.
A substantially L-shaped vertical portion with a notched slot provided with a press-contact blade at the distal end, a substantially L-shaped vertical portion with a female terminal portion at the distal end, and at both ends of a horizontal portion connected to the connecting single material. The electric circuit material according to claim 1 or 2, wherein the electric circuit material is substantially U-shaped with a vertical portion, and has one of a tab, a slot, and a female terminal at a tip of each of the vertical portions. 4. A plurality of connection single members are overlapped in a linear, orthogonal or oblique direction and connected by welding or rivets, and the terminal single members are connected to required positions by the connection form of the connection single members. Claims 1 to 3
The electric circuit material according to any one of the above. 5. An electric connection box containing the electric circuit material according to claim 1 as a power supply circuit.