JP2004153020A - Transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the primary current value free from adverse effect of noise by suppressing voltages to be induced at the magnetic sensor output terminal side even when the primary current is high in frequency. <P>SOLUTION: A magnetosensitive section 2 is connected to a lead terminal 4 with four wires 3. An output current is supplied to the magnetosensitive section 2 from terminals 11 and 13 through lead lines 5 and the lead terminals 4 provided on the surface of a substrate 8. Output signals are outputted across terminals 12 and 14 after travelling along a channel consisting of the magnetosensitive section 2, a lead terminal 4, a lead line 5, and then the terminal 12, and along a channel consisting of the magnetosensitive section 2, a lead terminal 4, a through hole 6, a backside lead line 7, a through hole 6, and then the terminal 14. The lead lines and the lead terminals constituting the lead wire channels for extracting output from the magnetosensitive section 2 are arranged so that the opening area of the channels from the terminal 12 through the terminal 14 is zero relative to the magnetic flux. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transformer used for a DC / DC converter or an AC / DC converter used as a DC power supply, for example.
[0002]
[Prior art]
As is well known, most electronic devices cannot perform their functions satisfactorily with a commercial power supply of AC 100 V. Therefore, a power supply device for converting an input AC voltage such as DC 5 V or DC 24 V is required. .
[0003]
On the other hand, recently, there is a demand for higher power efficiency, and there is a demand for an improved power supply configuration for various devices. In order to further increase the efficiency of the power supply, it is common to provide current detection means such as a current sensor at various points in the power supply circuit, and to feed back to the control circuit based on the output value to improve the efficiency.
[0004]
As one solution for detecting the current, a method using a shunt resistor is widely known. However, in this method, since a voltage drop occurs in the shunt resistor, the power loss in a power supply circuit handling a large current becomes a large value that cannot be ignored.
[0005]
In addition, since the shunt resistor has a temperature characteristic, a correction circuit corresponding to the temperature characteristic is required, which causes a problem that the power supply device becomes expensive.
[0006]
Furthermore, in order to perform feedback control in order to achieve power efficiency, it is necessary to newly install various sensors that have not been used in the past, so that the size of the entire power supply device becomes large and it becomes expensive. Problems arise.
[0007]
On the other hand, another technical document (see Patent Document 1) discloses a current detecting device of a circuit with a built-in choke coil. However, since the choke coil is a component for smoothing the inrush of the input current, a magnetic flux density due to the current before smoothing slightly different from the output current after smoothing is generated in the core portion. As a matter of course, a similar magnetic flux density also occurs in the magnetic sensor portion. Therefore, in order to further improve the efficiency, it is necessary in a power supply circuit or the like to perform current detection not in a choke portion but in a transformer portion that performs voltage conversion after smoothing.
[0008]
[Patent Document 1]
JP-A-2002-181851 (page 4, FIG. 1)
[0009]
[Problems to be solved by the invention]
In view of such a conventional problem, the present inventor has made the power supply device of an existing size by adding a current sensor function to the transformer itself, which is an indispensable part of the power supply device. We have found a transformer that is left as it is and prevents power loss in the current sensor. That is, in a transformer including a core formed of a magnetic material and a plurality of sets of windings wound around the core, a magnetic flux density generated in a gap provided in at least a part of the core is detected. It is characterized by having an analog output type magnetic sensor (Japanese Patent Application No. 2002-258186).
[0010]
However, this transformer has a problem that when the frequency of the primary current is high, an induced voltage is generated at the output terminal side of the magnetic sensor, and the S / N of the output of the magnetic sensor is reduced.
This problem is described in further detail below.
[0011]
The principle of operation when a magnetic field is detected by a conventionally used magnetoelectric conversion element, for example, a Hall element will be described with reference to FIG.
[0012]
In FIG. 8, the Hall element 1 is placed in a magnetic field having a magnetic flux density B perpendicular to the plane of the drawing. A line 9-10 indicates a boundary line of a region where the magnetic field changes, and a magnetic field is applied on the arrow side of the boundary line 9-10. When a drive current is applied to the terminals 11 and 13, the Hall voltage generated in the magnetic sensing unit 2 is extracted from the terminals 12 and 14.
[0013]
On the other hand, when the magnetic flux φ intersecting the Hall element 1 changes with time due to the movement or increase or decrease of the magnetic field, it is formed by the lead wire 4 connected to the terminals 12 and 14 and is hatched in FIG. An electromotive force Vφ is generated in a loop-shaped conductive line having an opening area S indicated by an electromagnetic induction effect.
[0014]
The electromotive force Vφ is generally called an induced voltage,
Vφ = −dφ / dt = −SdB / dt (1)
It becomes.
[0015]
Originally, if the product sensitivity of the Hall element is KH and the drive current is IC, the terminals 12 and 14
VH = KH ・ IC ・ B (2)
Should be output, but if the induced voltage Vφ is mixed, the output voltage Vout becomes
Vout = VH + Vφ (3)
Therefore, an error occurs for the purpose of obtaining the output VH proportional to the magnetic flux density.
[0016]
This error component, that is, the induced voltage Vφ is proportional to the temporal change rate of the magnetic flux amount or the magnetic flux density. Therefore, when the magnetic field changes abruptly, for example, in a high-frequency alternating magnetic field or the like, it is equal to or larger than the Hall voltage. The voltage may be higher than that described above, causing a large error, which is a problem.
[0017]
Accordingly, an object of the present invention is to provide a current sensor function in the transformer itself, which is an indispensable part of the power supply device, in view of such a problem, thereby keeping the power supply device of the existing size, and An object of the present invention is to provide a transformer in which power loss in a current sensor does not occur.
[0018]
In particular, an object of the present invention is to suppress the generation of an induced voltage on the output terminal side of the magnetic sensor even when the frequency of the primary current is high, and to eliminate the problem of reducing the S / N of the magnetic sensor output. Is to provide.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the present invention according to claim 1 is a transformer including a core formed of a magnetic material and a plurality of sets of windings wound on the core, wherein at least one of the cores is provided. An analog output type magnetic sensor for detecting a magnetic flux density generated in a gap portion provided in a part thereof, and a suppression unit for suppressing generation of an induced voltage on an output side of the magnetic sensor are provided.
[0020]
According to a second aspect of the present invention, in the transformer according to the first aspect, the magnetic sensor includes a magnetic sensing unit that detects a magnetic field to be detected formed on the substrate, and the suppression unit includes a magnetic sensor. An output conducting line formed on both surfaces to take out an electrical output according to the strength of the detected magnetic field from the magnetic sensing unit, and an opening area at which the output conducting line intersects the detected magnetic field is set to zero. In addition, at least one of the output conducting lines formed over both the front and back surfaces has a large area portion that completely covers one surface of the magneto-sensitive portion when viewed from the direction of the detected magnetic field, and further includes: A portion of the output conductive line formed on both front and back surfaces except for the large area portion has a structure substantially overlapping with the substrate interposed therebetween.
[0021]
According to a third aspect of the present invention, in the transformer according to the second aspect, a slit-shaped opening is provided in a large area of the output conducting line.
[0022]
According to a fourth aspect of the present invention, in the transformer according to any one of the first to third aspects, the core formed of the magnetic material includes a first E-type core and a second E-type core, or an E-type core. It is composed of a mold core and an I-type core.
[0023]
According to a fifth aspect of the present invention, in the transformer according to any one of the first to fourth aspects, the analog output type magnetic sensor is a Hall element or a Hall IC.
[0024]
By adopting the above configuration, it is possible to configure a transformer having the function of a current sensor while maintaining the existing size, and to contribute to power saving by adopting an inexpensive configuration that does not cause power loss in the sensor. Transformer is obtained.
[0025]
In particular, even when the frequency of the primary current is high, generation of an induced voltage on the output terminal side of the magnetic sensor is suppressed, and the S / N of the magnetic sensor output does not decrease.
[0026]
As the core material, in addition to ferrite, which is a general magnetic material, various magnetic materials such as a silicon steel sheet and a soft magnetic metal material typified by electromagnetic soft iron can be used, and frequency characteristics and temperature characteristics can be used. It is necessary to select the most suitable material in consideration of such factors.
[0027]
There is no particular limitation on the core shape, but various shapes such as a case where two mass-produced E-shaped cores are used, a case where an E-shaped core and an I-shaped core are used, and a toroidal shape are also used. It is possible, and it is necessary to have at least one gap portion. The gap is necessary to prevent magnetic saturation in the core, and is not newly provided for disposing a magnetic sensor.
[0028]
For the analog output type magnetic sensor, a Hall element, Hall IC, MR, flux gate sensor, MI sensor, etc. can be applied, but a small and inexpensive Hall element or linear output type that outputs an output depending on the polarity of magnetic flux. Is desirable.
[0029]
The induced voltage suppressing means of the magnetic sensor can be provided at least on the output terminal side to remove most of the influence of the induced voltage, but it is desirable to suppress the induced voltage also on the input terminal side.
Further, it is preferable to provide a slit-shaped opening in a large area of the conductive line.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0031]
FIG. 1A is a simplified schematic diagram illustrating a cross-sectional structure according to an embodiment of the present invention. FIG. 1B is a plan view of FIG. 1A viewed from above.
[0032]
The core of the transformer according to the present embodiment includes an E-type core 41 having three magnetic legs 53, 54, and 55, and an I-type core 42 connecting the magnetic legs 53 and 55 of the E-type core 41. The distal end of the center magnetic leg 54 included in the E-type core 41 and the I-type core 42 are arranged to face each other with a gap 43 therebetween. The gap 43 between the E-shaped core 41 and the I-shaped core 42 is necessary for avoiding magnetic saturation, and is not newly provided for disposing the sensor.
[0033]
Both the primary winding and the secondary winding 31 constituting the transformer according to the present embodiment are wound around the center magnetic leg 54 of the E-shaped core 41 as a winding axis. Usually, the primary winding and the secondary winding 31 are integrally wound by a current division winding or a voltage division winding to improve the coupling between the primary and secondary windings. The wound shaft is a shaft-shaped object on which a coil is mounted, and is a magnetic leg for directly winding a coil, or a magnetic leg for mounting a bobbin around which a coil is wound.
[0034]
In the transformer according to the present embodiment, the Hall element 21 which is a magnetic sensor of an analog output type is disposed in the gap 43 between the E-shaped core 41 and the I-shaped core 42. This makes it possible to detect the density of the magnetic flux generated in the gap 43.
[0035]
FIG. 2 is a characteristic diagram illustrating a relationship between the primary current of the transformer according to the present embodiment and the magnetic flux density of the Hall element unit. Since the magnetic flux density of the gap portion 43 naturally becomes a value proportional to the primary current flowing through the primary winding of the transformer, the characteristic is that the output of the Hall element 21 changes linearly with respect to the primary current. From the output of the Hall element 21, the primary current value can be measured without causing power loss.
[0036]
In addition, since a low power consumption type magnetic sensor such as the Hall element 21 is used, basically no power loss occurs. Therefore, the power loss is remarkably reduced as compared with the conventional example in which the primary current is detected by the shunt resistor, and it is possible to realize higher power efficiency.
[0037]
As the core material, in addition to ferrite, which is a general magnetic material, various magnetic materials such as a silicon steel sheet and a soft magnetic metal material typified by electromagnetic soft iron can be used, and frequency characteristics and temperature characteristics can be used. It is necessary to select the most suitable material in consideration of such factors.
[0038]
There is no particular limitation on the core shape, but various shapes such as a case where two mass-produced E-shaped cores are used, a case where an E-shaped core and an I-shaped core are used, and a toroidal shape are also used. It is possible, and it is necessary to have at least one gap portion.
[0039]
As the analog output type magnetic sensor, a Hall element, a Hall IC, an MR, a flux gate sensor, an MI sensor, etc. are applicable. Is desirable.
[0040]
FIG. 3 is a configuration diagram showing a Hall element portion used in the present embodiment.
In FIG. 3, reference numeral 1 denotes a DIP (Dual Inline Package) type Hall element, and the Hall element 1 is mounted on a substrate 8. The magnetic sensing part 2 is connected to the lead terminal 4 by four wires 3. Further, the lead terminal 4 is drawn out of the resin mold portion surrounded by the dashed line, and is passed through the lead wire 5 provided on the surface of the substrate 8 and the lead wire 7 provided on the back surface of the substrate 8 to the terminals 11 and 12. , 13 and 14. That is, the input current is supplied from the terminals 11 and 13 to the magnetic sensing unit 2 through the lead wire 5 and the lead terminal 4 provided on the surface of the substrate 8.
[0041]
On the other hand, the output signal is transmitted through the magnetic sensing part 2 → lead terminal 4 → lead wire 5 → terminal 12 and the sensing part 2 → lead terminal 4 → through hole 6 → back side lead wire 7 → through hole 6 → terminal 14. It is output between terminals 12 and 14. As shown in FIG. 3, each lead wire and lead terminal constituting a conductive line for taking out the output from the magnetic sensing unit 2 is such that the path from the terminal 12 to the terminal 14 has an opening area for magnetic flux of zero. It is arranged in.
[0042]
As the substrate 8, a flexible substrate having a thickness of about 0.2 mm is used. The lead wires 5 and 7 are obtained by etching a copper foil having a thickness of 20 μm adhered to both surfaces of the substrate 8 to form a wiring pattern as shown in FIG. The lead wire 7 on the back side is connected to the lead terminal 4 and the terminal 14 on the front side by a through hole 6.
[0043]
A gold wire is used as the wire 3, and this wire wire connects the magnetic sensing part 2 and the lead terminal 4 by wire bonding. The lead terminal 4 is connected to the lead wire 5 by solder.
[0044]
A boundary line 9-10 indicates a boundary of a region where the magnetic field changes, and indicates that a magnetic field having a magnetic flux density B in a direction perpendicular to the paper on the arrow side of the boundary line 9-10 is applied.
[0045]
With such a structure, a loop-shaped conductive line extending from the terminal 12 to the terminal 14 through the lead wire 5, the lead terminal 4, the wire 3, the magnetic sensing part 2, and the through hole 6 and the lead wire 7 on the back surface is formed by a magnetic flux. Since the intersecting opening area is zero, no induced voltage Vφ is generated.
[0046]
In the present embodiment, the lead wire 7 is formed to have a large width on the back surface of the Hall element 1 so that the lead wire 7 has an opening in the loop-shaped conductive line even if the Hall element 1 is displaced or the wire 3 is deformed. No area was created.
[0047]
Although the area of the lead wire 7 crossing the magnetic flux is larger than that of the lead wire 5 on the surface, the influence of the loss due to the eddy current can be substantially eliminated by reducing the thickness of the copper foil to 20 μm or less. Can be.
[0048]
Further, as shown in FIGS. 4 and 5, by providing the thin slit-shaped opening 15 in the lead wire 7, even if the magnetic flux density or the frequency of the magnetic field increases, the eddy current can be canceled. In this case, by forming a slit having a width of about 5 to 10 times the thickness of the copper foil, the generation of the induced voltage Vφ due to the opening surface of the conductive line can be ignored compared to the Hall voltage VH. The slits may be formed in a net shape, a ladder shape, or the like, instead of being provided in parallel as in the illustrated example, and the direction in which the slits are arranged may be arbitrarily determined such as vertical, horizontal, or oblique. Can be.
[0049]
On the other hand, a loop extending from the terminal 11 of the input line to the terminal 13 through the magnetic sensing part 2 generates an induced voltage. In this case, the voltages at the output terminals 12 and 14 change in the same phase. If it is connected to a circuit or an amplifier, it is apparently unaffected.
[0050]
【Example】
The outline of the created transformer is shown below.
Primary winding: 10 turns Secondary winding: 20 turns Gap part thickness: 0.6 mm
Hall element used: HW003C (trade name) manufactured by Asahi Kasei Electronics
Core: Ferrite EI core Primary current frequency: 100 kHz
Input current: 0.4 A / div
Hall element induced electromotive voltage: 50 mV / div
[0051]
FIG. 6 shows an induced voltage waveform of the Hall element in the transformer when the induction is not suppressed, and FIG. 7 shows an induced voltage waveform of the Hall element in the transformer after the induction compensation.
[0052]
Assuming that the input voltage of the Hall element is 1 V and the primary current of ± 1 A flows in the current configuration of the transformer, the output voltage of the Hall element is about ± 50 mV. However, as can be seen from FIG. 6, if the induction suppression is not performed, an induced voltage of about ± 150 mV is generated, and noise larger than the output voltage of the Hall element is generated, making it impossible to measure the primary current.
[0053]
On the other hand, when the induction is suppressed, the generation of the induced voltage can be dramatically reduced, so that the value of the primary current can be measured without being affected by noise.
[0054]
【The invention's effect】
As described above, by implementing the present invention, it is possible to realize a transformer having a current sensor function while maintaining the existing size, and to adopt a low-cost configuration that does not cause power loss in the sensor. It is possible to realize a transformer that can contribute to realization.
[0055]
In particular, even when the frequency of the primary current is high, the generation of an induced voltage on the output terminal side of the magnetic sensor can be dramatically reduced, and the value of the primary current can be measured without being affected by noise.
[Brief description of the drawings]
FIG. 1 is a simplified diagram showing a partially broken side structure of a transformer according to an embodiment of the present invention, and a plan view of the transformer as viewed from above.
FIG. 2 is a characteristic diagram illustrating a relationship between a primary current and a magnetic flux density of a transformer according to the present embodiment.
FIG. 3 is a configuration diagram showing a Hall element portion used in the present embodiment.
FIG. 4 is a plan view showing a slit-shaped opening provided in a lead wire 7 used in the present embodiment.
FIG. 5 is a plan view showing a slit-shaped opening provided in a lead wire 7 used in the present embodiment.
FIG. 6 is a diagram showing an induced voltage waveform of a Hall element in a transformer when induction is not suppressed.
FIG. 7 is a diagram showing an induced voltage waveform of a Hall element in a transformer that has performed inductive compensation as one example of the present invention.
FIG. 8 is an operation principle diagram when a magnetic field is detected by a conventionally used magnetoelectric conversion element.
[Explanation of symbols]
1 Hall element 2 Magnetic sensing part 4 Lead terminal 5 Lead wire (surface)
6 Through hole 7 Lead wire (back side)
8 Board 11, 12, 13, 14 Terminal 15 Opening 21 Hall element 31 which is an analog output type magnetic sensor Primary winding and secondary winding 41 E type core 42 I type core 43 Gap parts 53, 54, 55 leg

Claims (5)

In a transformer including a core formed of a magnetic material and a plurality of sets of windings wound around the core,
An analog output type magnetic sensor for detecting a magnetic flux density generated in a gap provided in at least a part of the core,
Suppression means for suppressing generation of an induced voltage on the output side of the magnetic sensor,
A transformer comprising: The transformer according to claim 1,
The magnetic sensor includes a magnetic sensing unit that detects a magnetic field to be detected formed on the substrate,
The suppression means includes an output conducting line formed over both the front and back surfaces of the substrate, and for taking out an electrical output according to the intensity of the detected magnetic field from the magnetic sensing unit,
In order to make the opening area where the output conducting line intersects with the detected magnetic field zero, at least one of the output conducting lines formed on both the front and back surfaces has the above-mentioned sensitivity as viewed from the direction of the detected magnetic field. It has a large area that completely covers one surface of the magnetic part, and the portion of the output conducting line formed over the front and back surfaces except for the large area substantially overlaps via the substrate. Having a structure,
A transformer characterized by that. The transformer according to claim 2,
A transformer, wherein a slit-shaped opening is provided in a large area of the output conducting line. The transformer according to any one of claims 1 to 3,
A transformer characterized in that the core formed of the magnetic material comprises a first E-type core and a second E-type core, or an E-type core and an I-type core. The transformer according to any one of claims 1 to 4,
The transformer, wherein the analog output type magnetic sensor is a Hall element or a Hall IC.

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