JP2003188032A - Step-down transformer for single-phase full-wave rectifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a step-down transformer for a single-phase full wave rectifier which can reduce the magnetic wave radiation of a secondary coil, an overlapping surge voltage and resistance loss controlling an increase in size and can improve an electrical insulation property between an independent end of a secondary coil and a common connection end. <P>SOLUTION: The transformer 300 has a core 10 in squarish an 'eight' shape and draws the independent ends 61 and 71 and the common connection ends 62 and 72 of the secondary coils 6 and 7 in substantially a C shape of one turn out of a pair of secondary coil lead-out openings 8 and 9 in the same direction. The step-down transformer is provided for the single-phase full wave rectifier which can reduce the magnetic wave radiation of the secondary coil, the overlapping surge voltage and the resistance loss controlling an increase in size and can improve the electrical insulation property between the independent end and the common connection end of the secondary coil by narrowing a sidewall 3 near the secondary coil lead-out openings 8 and 9 and increasing a width in a horizontal face of the sidewall portion 3 moving away from the secondary coil lead-out openings 8 and 9. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a step-down transformer for a single-phase full-wave rectifier.

[0002]

2. Description of the Related Art In an electric vehicle including a hybrid vehicle, a dual power supply system in which electric power is supplied to a traveling motor from a high-voltage main battery and various auxiliary devices are supplied from a low-voltage auxiliary battery is useful in various respects. . In addition, even in a normal internal combustion engine, due to various factors, there has been a tendency to mount a two-battery power supply system that mounts both a high-voltage main battery and an auxiliary battery for low-voltage load power supply. In this dual power source vehicle power supply system, it is a rational choice to make the auxiliary battery small in capacity and to transmit power from the main battery to the auxiliary battery through the step-down DC-DC converter device.

This step-down DC-DC converter device is
An inverter circuit that forms a single-phase AC voltage from an input DC voltage, a step-down transformer that transforms this single-phase AC voltage, a rectifying unit that rectifies the output voltage of this step-down transformer, and a smoothing circuit that smoothes the rectified voltage. However, it is usual that the secondary coil of the step-down transformer is provided with an intermediate terminal and the rectification unit is configured by a single-phase full-wave rectification method. Hereinafter, this step-down transformer is also referred to as a single-phase full-wave rectifier step-down transformer.

Explaining further, this step-down transformer for a single-phase full-wave rectifier has a pair of secondary coils wound in the same direction and connected in series, and the rectifier circuit is composed of a pair of rectifying elements. The midpoint of the secondary coils connected to each other is grounded or used as an output terminal to the smoothing circuit.

It is preferable to use a plate coil for the step-down transformer for a single-phase full-wave rectifier that outputs such a large secondary current in terms of simplification of the manufacturing process and reduction of electric resistance. As an example of this type of step-down transformer for a single-phase full-wave rectifier using a plate coil, the step-down transformer structure for a single-phase full-wave rectifier shown in FIGS. 3 and 4 is known.

In FIGS. 3 and 4, 1 is a base portion, 2 is a central column portion, 3 is a side wall portion divided into two, 4 is a coil accommodating groove, 5 is a primary coil outlet, and 6 and 7 are two. Next coil,
Reference numerals 8 and 9 denote secondary coil outlets.

First, the core will be described.

The base 1 is formed in a substantially rectangular shape, and the central pillar 2 is provided upright from the center of the upper end of the base 1. The pair of side wall portions 3 are erected from both sides of the upper end of the base portion 1 with the coil housing groove 4 and the central pillar portion 2 sandwiched therebetween, and the coil housing groove 4 includes the inner side surfaces of the side wall portions 3 and the central pillar portion 2. A pair of secondary coil outlets 8 and 9 opened in the same direction on the outer peripheral surface of the secondary coil, and a primary coil outlet 5 opened on the opposite side of the secondary coil outlets 8 and 9; It is formed between the central pillar portion 2 and the side wall portion 3 with the upper surface of 1 as the bottom portion. Further, although not shown in the drawings, a top plate portion that is in contact with the upper surface of the central pillar portion 2 and the upper surfaces of both side wall portions 3 and closes the upper ends of the coil housing grooves 4 is provided, and the base portion 1, the central pillar portion 2, The side wall portion 3 constitutes a letter-shaped core 10, and the coil housing groove 4, the secondary coil outlets 8 and 9, and the primary coil outlet 5 are defined.

Next, the secondary coils 6 and 7 are formed by plate-shaped coils which are wound around the coil housing groove 4 once each with their main surfaces being axially overlapped with each other in a posture parallel to the bottom surface of the coil housing groove 4. One end portion 61, 71 as an independent end portion and the other end portion 62, 72 as a common connection end portion are individually drawn out from the pair of secondary coil lead-out ports 8, 9 respectively. A primary coil (not shown) is wound around the coil housing groove, both ends of which are drawn out from the primary coil outlet 5, and the horizontal section of the central column 2 has a circular shape.

In FIG. 3, the horizontal cross section of the side wall portions 3 has a rectangular shape, and the inner side surfaces of the side wall portions 3 are vertical planes parallel to each other, whereby the width of the coil accommodating groove 4 is It gradually expands toward the primary coil outlet 5 and both secondary coil outlets 8 and 9. As a result, the independent ends 61 and 71 of both the secondary coils 6 are extended near the side wall 3 near the secondary coil outlets 8 and 9 and on a plane parallel to the bottom surface of the coil housing groove 4. The secondary coil outlets 8 and 9 are arranged at positions close to the secondary coil outlets 8 and 9 so as to sandwich the common connection ends 62 and 72 of the secondary coils 6, respectively, and are linearly parallel to each other. Protruding from. Common connection ends 6 of both secondary coils 6 and 7
Positions 2 and 72, which are extended near the central column portion 2 near the secondary coil outlets 8 and 9 and are close to both the secondary coil outlets 8 and 9 on a plane parallel to the bottom surface of the coil housing groove 4. It is fastened on top of each other.

In FIG. 4, the inner side surfaces of the side wall portions 3 are partial cylindrical surfaces coaxial with the central pillar portion 2, and thus the width of the coil housing groove 4 in the radial direction of the central pillar portion 2 is equal. It is wide. Independent end portions 61 and 71 of both secondary coils 6
After being discharged from the secondary coil outlets 8 and 9, they are curved with small curvatures in opposite directions so as not to come into contact with the common connection ends 62 and 72, and both of them on a plane parallel to the bottom surface of the coil housing groove 4. It is arranged so as to sandwich the respective common connection ends 13 of both the secondary coils 6 and 7 at positions close to the secondary coil outlets 8 and 9. Common connection ends 6 of both secondary coils 6 and 7
Positions 2 and 72, which are extended near the central column portion 2 near the secondary coil outlets 8 and 9 and are close to both the secondary coil outlets 8 and 9 on a plane parallel to the bottom surface of the coil housing groove 4. It is fastened on top of each other.

[0012]

However, in the above-mentioned dual power supply system for a vehicle, the terminal voltage of the main battery is set to a high voltage such as several hundreds V for various reasons, while the auxiliary battery meets the conventional battery specifications. Normally 12V is used.
For this reason, the secondary current of the step-down transformer becomes extremely large, and the resistance loss and heat generation of the secondary coil have an adverse effect that cannot be overlooked by the temperature of the heat insulating resin of the step-down transformer and the temperature of the diode connected to the secondary coil.

In addition, the step-down ratio is large at the end of the secondary coil (also referred to as the outer core conductor) which is the conductor of the secondary coil from the core of the step-down transformer to the rectifying diode element or the base plate. Therefore, a large current flows, but in the single-phase full-wave rectification method, since half-wave currents of different single-phase alternating currents flow in each secondary coil, the current in each secondary coil contains large harmonics. As a result, the inductance component of the end portion (outer core conductor portion) of the secondary coil exposed from the core generates a large surge voltage, radiates electromagnetic noise, and causes other electronic circuit elements to malfunction.

Next, in the conventional core as shown in FIG. 3 described above, the overall shape becomes large, so that the apparatus becomes large in size, and at the same time, the weight and the core material cost increase. Further, since the coil largely protrudes from the left side opening of the core, this portion becomes a magnetic circuit with a large gap in terms of an equivalent circuit and radiates a large electromagnetic noise to the surrounding space.

Further, in the conventional core as shown in FIG. 4 described above, although the overall shape can be made small, the total length of the secondary coil 6 is extended by bending the independent ends 13 of the secondary coils 6 with a small curvature. The distance increases, which causes an increase in resistance loss and heat generation, an increase in electromagnetic radiation noise and an increase in high-frequency surge voltage due to an increase in line inductance, and between the independent end portion 13 and the common connection end portions 11 and 12. Interval X
Since it is not easy to secure the electrical insulation, there is a problem that it is difficult to secure electrical insulation.

The present invention has been made in view of the above problems, and it is possible to reduce the electromagnetic wave radiation of the secondary coil, the superimposed surge voltage, and the resistance loss while suppressing the increase in the size of the secondary coil. It is an object of the present invention to provide a step-down transformer for a single-phase full-wave rectifier, which can improve the electrical insulation between the end and the common connection end.

[0017]

A step-down transformer for a single-phase full-wave rectifier according to the present invention is provided with a substantially rectangular base portion, a central pillar portion standing upright from an upper end central portion of the base portion, and a predetermined interval. Side walls that surround the central pillar and are erected from both sides of the upper end of the pedestal, and a pair of secondary openings that are opened in the same direction on the inner side surface of the sidewall and the outer peripheral surface of the central pillar. A coil accommodating groove that has a coil outlet and is formed between the central pillar portion and the side wall portion by making the upper surface of the base portion a bottom portion, and contacts the upper surface of the central pillar portion and the upper surface of the side wall portion. A core having a top plate portion that closes the upper end of the coil housing groove,
One end and a common connection end as independent ends, each of which is composed of a plate-shaped coil whose main surface is axially overlapped with each other in a posture parallel to the bottom surface of the coil accommodating groove and wound around the coil accommodating groove once The other end as a part has a pair of secondary coils individually drawn from the pair of secondary coil outlets, and a primary coil wound in the coil housing groove, and the width of the coil housing groove. Gradually expands toward the secondary coil outlets, and the independent ends of the secondary coils are extended toward the side wall portion near the secondary coil outlets to form the coil housing groove. Is disposed on both sides parallel to the bottom surface of the secondary coil outlet at positions close to the secondary coil outlets, and the common connection ends of the secondary coils are , Pull out the secondary coil The side wall portion is extended and close to the central pillar portion in the vicinity of the mouth, and is fastened to be overlapped with each other at a position on the plane parallel to the bottom surface of the coil accommodating groove and close to the both secondary coil lead-out openings. It is characterized in that it is formed so as to become narrower toward the secondary coil in a horizontal section parallel to the main surface of the secondary coil.

That is, the step-down transformer for a single-phase full-wave rectifier of the present invention has a pair of two coils each having a core having a cross-section including the center of the central pillar portion in a day shape and a one-turn substantially C-shaped coil. A pair of secondary coils in which the independent end and the common connection end of the secondary coil are pulled out in the same direction from the pair of secondary coil outlets, and the pair of independent ends overlap each other in the thickness direction in the vicinity of the secondary coil outlet. 3 in the point of horizontally sandwiching
Same as the conventional structure, but the side wall is narrowed in the vicinity of the secondary coil outlet, and the horizontal cross-sectional area of the side wall (reduction of magnetic path) is reduced as it moves away from the secondary coil outlet. The feature of this is that the width of the portion in the horizontal plane is increased (the opening width of the primary coil outlet is reduced) to ensure and prevent the square shape of the entire core.

It should be noted that the primary coil outlet may be provided with a height equal to the height of the central column to completely divide the side wall portion by the primary coil outlet, but instead, the primary coil outlet is A predetermined portion of one side wall portion may be a groove portion that is recessed from the horizontal end surface (upper surface or lower surface) of the side wall portion in the axial direction of the central column portion by a predetermined depth.

Further, the above-mentioned base portion, central pillar portion, side wall portion,
The core composed of the top plate portion is preferably divided into two parts, but the division surface can be set in various patterns as long as the primary coil and the secondary coil can be placed in the coil accommodating groove. A typical dividing method is one in which the one is E-shaped and the other is I-shaped.
Although it is in the shape of a letter, both may be in the shape of an E.

According to the step-down transformer for a single-phase full-wave rectifier of the present invention configured as described above, while suppressing an increase in size,
Single-phase full-wave rectification capable of reducing electromagnetic radiation, superimposed surge voltage, and resistance loss of the secondary coil, and improving the electrical insulation between the independent end of the secondary coil and the common connection end. A step-down transformer for equipment can be realized. This effect will be described later with reference to the embodiments, because the explanation using the drawings is easy to understand.

In a preferred embodiment, the horizontal cross section of the central pillar portion has a circular shape, and the coil accommodating groove is formed to have almost the same width in a direction parallel to the bottom surface except in the vicinity of the secondary coil outlet. A horizontal cross section of the inner side surface of the side wall portion is a semi-circular curve formed by a pair of substantially parallel straight lines located in the vicinity of the outlet of the secondary coil, and a substantially semicircular curve connected to one end of each of the straight line portions. It consists of a circle and
The independent ends of the both secondary coils project from the secondary coil outlet in a straight line shape substantially parallel to each other.

By doing so, the effects of the present invention can be further improved. This effect will be described later with reference to the embodiments, because the explanation using the drawings is easy to understand.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of a step-down DC-DC converter device for a two-battery vehicle equipped with a step-down transformer for a single-phase full-wave rectifier according to the present invention will be described with reference to the following embodiments. Explain.

[0025]

Example 1 Step-down DC using a step-down transformer for a single-phase full-wave rectifier of this example (hereinafter, also simply referred to as a transformer)
The circuit configuration of the DC converter device will be described below with reference to FIG. (Circuit configuration) 100 is an input-side smoothing capacitor, 200
Is an inverter, 300 is a transformer, 400 is a pair of diodes forming a rectifying unit, and 500 is a smoothing circuit. 501
Is a choke coil of the smoothing circuit, and 502 is a smoothing capacitor of the smoothing circuit.

The transformer 300 has a core 10, a primary coil 600, and secondary coils 6 and 7. One ends (common connection ends) of the secondary coils 6 and 7 are grounded and both ends (independent ends) are connected to the choke coil 501 through a pair of diodes 400. The secondary coils 6 and 7
It is also possible to connect one end (common connection end) to the choke coil 501 through the pair of diodes 400 and ground both ends (independent end).

The high-voltage high-frequency voltage output from the inverter 200 is stepped down by the transformer 300. Both the secondary coils 6 and 7 alternately output the half-wave rectified voltage to the low-voltage battery through the diode 400 and the smoothing circuit 500 for each different half-wave period. Since this type of DC-DC converter is well known, further description will be omitted.

Next, the transformer 3 which is the main part of this embodiment.
00 will be described in detail with reference to FIG. Figure 2
Shows a state in which the upper core and the primary coil are removed in the example in which the core 10 is formed by combining the E-shaped lower core 10X and the I-shaped upper core (not shown) each formed of sintered ferrite. It is a top view. However, in order to avoid complication of understanding, the same reference numerals are given to the components having the same main function as the components of FIG.

Reference numeral 1 is a rectangular parallelepiped base portion, 2 is a central column portion, 3
Is a side wall portion, 4 is a coil accommodating groove, 5 is a pair of primary coil outlets, 6 and 7 are secondary coils, and 8 and 9 are secondary coil outlets.

First, the core 10 will be described.

The base 1 is formed in a substantially rectangular shape, and the central pillar 2 is provided upright from the center of the upper surface 11 of the base 1. The side wall portion 3 is erected from both side portions in the X direction and the left side portion in the Y direction of the upper surface of the base portion 1 with the coil housing groove 4 and the central pillar portion 2 interposed therebetween.

The coil accommodating groove 4 is formed on the inner side surface 3 of both side wall portions 3.
0 and a pair of secondary coil outlets 8 and 9 opened in the same direction on the outer peripheral surface of the central column portion 2, and a shallow recess provided on the opposite side to the secondary coil outlets 8 and 9 by a predetermined depth. An upper surface 1 of the base 1 having a pair of groove-shaped primary coil outlets 5.
It is formed between the central pillar portion 2 and the side wall portion 3 with 2 as the bottom portion.

Although not shown in the drawings, a top plate portion is provided which is in contact with the upper surface 20 of the central pillar portion 2 and the upper surface of the side wall portion 3 and closes the upper end of the coil housing groove 4, and the base portion 1 and the central pillar portion 2 are provided. The side wall 3 and the side wall 3 constitute a day-shaped core 10, and the coil housing groove 4, the secondary coil outlets 8 and 9, and the primary coil outlet 5 are defined.

Each of the secondary coils 6 and 7 is composed of a plate-shaped coil which is wound around the coil receiving groove 4 once, with its main surface parallel to the bottom surface 12 of the coil receiving groove 4 and axially overlapping each other. On the other hand, one end portions 61 and 71 as independent end portions and the other end portions 62 and 72 as common connection end portions are individually drawn out from the pair of secondary coil lead-out ports 8 and 9, respectively. Further, the primary coil (not shown) has a coil housing groove 4
And both ends thereof are drawn out from the primary coil draw-out port 5 to the outside.

The outer side surface of the side wall portion 3 is formed by extending the three outer side surfaces of the base portion 1 upward, and the horizontal cross section of the inner side surface 30 of the side wall portion 3 is located substantially in the vicinity of the secondary coil outlets 8 and 9. It is composed of a pair of straight line portions 301 and 302 formed of parallel straight lines, and a semicircular portion 303 formed of a substantially semicircular curved line having both ends connected to one end of each of the straight line portions 301 and 302.

The horizontal cross section of the central column portion 2 has a circular shape coaxial with the inner side surface of the side wall portion 3, and the coil housing groove 4 is the bottom surface of the coil housing groove 4 except in the vicinity of the secondary coil outlets 8 and 9. Almost the same width is formed in the direction parallel to 12. The width of the coil accommodating groove 4 gradually widens toward both secondary coil outlets 8 and 9, and the side wall portion 3 has a secondary coil outlet in a horizontal cross section parallel to the main surfaces of the secondary coils 6 and 7. The width becomes narrower as it approaches 8 and 9.

Independent end portions 61 and 7 of both secondary coils 6 and 7, respectively.
1 is formed in a straight line substantially parallel to each other and protrudes from the secondary coil outlets 8 and 9 in the Y direction. The common connection ends 62 and 72 of both the secondary coils 6 and 7 project from the oblique secondary coil outlets 8 and 9 with respect to the independent ends 61 and 71 on the horizontal plane, and are arranged in the height direction at the tips. Are overlaid.

Reference numeral 63 is a fastening hole formed through the independent end portion 61 of the secondary coil 6, and 64 is a common connection end portion 6 of the secondary coil 6.
2, fastening holes 73, fastening holes penetrating the independent ends 71 of the secondary coil 7, 74, fastening holes penetrating the common connection end 72 of the secondary coil 7. Is. The fastening holes 63 and 64 are connected to the anode electrode terminals of different diodes 300, and the fastening holes 64 and 74 are fastened to a ground substrate (not shown).

The step-down transformer 300 for a single-phase full-wave rectifier according to this embodiment having the above-mentioned structure can achieve the following effects.

First, as compared with the transformer shown in FIG. 3, the overall shape can be made smaller, so that the device can be made smaller. Further, since the secondary coils 6 and 7 are covered with the side wall portion 3 also in the left side opening (primary coil lead-out port) 5 of the core 10, the currents of the secondary coils 6 and 7 are the single-phase full-wave rectification method. It is possible to prevent a large electromagnetic noise from being radiated to the surrounding space even though it contains a large harmonic wave. Next, as compared with the transformer shown in FIG. 4, the total extension distance of the secondary coils 6 and 7 is reduced by the amount that it is not necessary to bend the independent ends 61 and 71 of the secondary coils 6 and 7 with a small curvature. As a result, resistance loss and heat generation can be reduced, and electromagnetic radiation noise and high-frequency surge voltage can be reduced by reducing line inductance. Furthermore, both independent ends 61 and 71 and both common connection ends 6 can be realized.
Since the interval X between the two and 72 can be remarkably enlarged, the electrical insulation can be improved. Further, since the primary coil lead-out port 5 is reduced to the minimum size, it is possible to reduce electromagnetic noise radiation to the surrounding space.

[0041]

Second Embodiment Another embodiment will be described below with reference to FIG. FIG. 5 is a front view of the core.

In this embodiment, the core 10 is the lower core 10.
It is characterized in that it is composed of Y and an upper core 10Z, the lower core 10Y has a central pillar portion 2Y and a side wall portion 3Y, and the upper core 10Z has a central pillar portion 2Z and a side wall portion 3Z. Further, since the central pillar portion 2Y and the central pillar portion 2Z are fitted with each other on the tapered surface and the side wall portion 3Y and the side wall portion 3Z are fitted with each other on the tapered surface, an extremely large magnetic resistance component ( The cross-sectional area of the gap, which is the magnetic flux reduction component), perpendicular to the magnetic path can be significantly increased, and loss and heat generation can be reduced by reducing the magnetizing current.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a step-down DC-DC converter device for a vehicle according to a first embodiment.

FIG. 2 is a plan view showing a transformer of the first embodiment.

FIG. 3 is a plan view showing a transformer of Reference Example 1. FIG.

FIG. 4 is a plan view showing a transformer of Reference Example 2. FIG.

5 is a vertical cross-sectional view showing a core of Example 2. FIG.

[Explanation of symbols]

300 transformers 10 cores 6 secondary coil 7 Secondary coil 8 Secondary coil outlet 9 Secondary coil outlet 61 Independent end of secondary coil 62 Common connection end of secondary coil 71 Independent end of secondary coil 72 Common connection end of secondary coil

Claims (2)

[Claims] 1. A substantially rectangular base portion, a central pillar portion standing upright from a central portion of an upper end of the base portion, and a vertical pillar extending from both side portions of an upper end of the central pillar portion so as to surround the central pillar portion at a predetermined interval. And a pair of secondary coil outlets formed between the inner side surface of the side wall portion and the outer peripheral surface of the central column portion and opened in the same direction, and the bottom surface of the base portion is a bottom portion. However, a coil housing groove formed between the central pillar portion and the side wall portion, and a top plate that contacts the upper surface of the central pillar portion and the upper surface of the side wall portion and closes the upper end of the coil housing groove. An independent end formed by a core having a part, and a plate-shaped coil that is wound once in each coil accommodating groove so that its main surface is axially overlapped with each other in a posture parallel to the bottom surface of the coil accommodating groove. And the other end as a common connection end is a pair of The secondary coil has a pair of secondary coils individually drawn out from the secondary coil outlet, and a primary coil wound in the coil housing groove, and the width of the coil housing groove is set to the both secondary coil outlets. The respective independent ends of the secondary coils are extended toward the side wall portion near the secondary coil outlet and are formed on the surface parallel to the bottom surface of the coil housing groove. The common connection ends of the both secondary coils are arranged at a position close to the secondary coil outlet, and the common connection ends of the both secondary coils are disposed near the secondary coil outlet. The side wall portion of the secondary coil is extended to the central pillar portion and is fastened to each other at a position parallel to the bottom surface of the coil housing groove and close to the secondary coil outlets. Smell of horizontal section parallel to the main surface Single-phase full-wave rectifier for step-down transformer, characterized in that it is formed narrower as it approaches the secondary coil outlet. 2. The step-down transformer for a single-phase full-wave rectifier according to claim 1, wherein a horizontal cross section of the central pillar portion has a circular shape, and the coil accommodating groove is provided except for the vicinity of the outlet of the secondary coil. The horizontal cross section of the inner side surface of the side wall portion is formed to have almost the same width in a direction parallel to the bottom surface, and a pair of straight line portions formed of substantially parallel straight lines located near the secondary coil outlet and And a semi-circular portion formed of a substantially semi-circular curve connected to each end, wherein the independent ends of the secondary coils project from the secondary coil outlet in a straight line substantially parallel to each other. Single-phase full-wave rectifier step-down transformer.