JP3218585B2 - Print coil type transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer used in electronic equipment and a power supply, and more particularly to an improvement in a printed coil type transformer having an auxiliary winding coil.

[0002]

2. Description of the Related Art An auxiliary winding coil is used, for example, in a power supply device disclosed in Japanese Patent Application Laid-Open No. 61-35613 proposed by the present applicant. FIG. 4 is a circuit diagram of a conventional switching power supply of this type. In the figure, a DC voltage Vin is applied to a primary coil 10 and is turned on and off by a switching element Q such as a transistor. Here, the DC voltage Vin is applied to one end of the primary winding terminal, and the switching element Q is connected to the other end of the primary winding terminal. The center tap CT is used here to connect the two divided primary coils 10 in series. Here, the AC voltage generated due to the on / off of the switching element has a higher potential at the other end of the primary winding terminal closer to the switching element than at one end of the primary winding terminal. Also, the secondary coil 2
Since six 0s are connected in parallel, this is explicitly shown in the drawing. Since the switching signal induced in the secondary winding is generated between the terminals for the secondary winding, the switching signal is rectified and smoothed by the output smoothing circuit, and the DC voltage is supplied to the load side. Usually, a control circuit is provided for feeding back a feedback control signal to the switching element Q in order to stabilize the output voltage.

FIG. 5 is an explanatory view in the case of employing a printed coil type transformer disclosed in Japanese Patent Application No. 5-73449, proposed by the present applicant, as each coil.
(A) shows the coil stacking order, and (B) shows the NI distribution. In the figure, the primary coil 10 is changed to Pa and Pb by 2
A secondary coil 2 which is divided and has a secondary winding S between the two
It is sandwiched between 0. The auxiliary coil AUX is stacked above the primary coil Pa. For the NI distribution,
N is the number of turns of the coil, and I is the DC current. For example, in the case of a printed coil type transformer, when a certain conductor surface has 3 turns and a current of 1 A flows, NI = 3 (AT). According to the law of electromagnetic induction, the current flows in the primary side and the secondary side in opposite directions, and the NI value of the entire coil is zero. NI
The distribution is an index representing the leakage inductance. In this case, the larger the area indicated by the oblique lines, the larger the leakage inductance is, which is undesirable.

[0004]

According to the stacking order shown in FIG. 5, the auxiliary coil is disposed outside one of the primary coils, so that the magnetic coupling between the primary coil and the secondary coil is performed. However, there is a problem that the unbalance occurs at the two boundary surfaces and the coil loss increases. In addition, since one of the outer surfaces of the laminated coil is an auxiliary coil and the other is a primary coil, there is also a problem that the outer surface of the laminated coil electrostatically interferes with the surroundings and becomes a noise source. The present invention has solved the above-mentioned problems,
An object of the present invention is to provide a printed coil type transformer having a small coil loss and a small electrostatic noise.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a primary coil (10) having a conductor pattern corresponding to a primary winding (n1) of a transformer, and a secondary winding of the transformer. A secondary coil (20) having a conductor pattern corresponding to the wire (n2) and an auxiliary coil (30) having a conductor pattern corresponding to the auxiliary winding (n3) of the transformer are laminated, and the primary coil is formed. Before splitting the side coil into two
In a printed coil transformer in which the secondary coil is sandwiched , the auxiliary coil is connected in series.
The auxiliary coil is arranged on the outermost layer, one end of the auxiliary coil is grounded to the primary winding side, and the auxiliary coil is
Voltage induced at both ends is applied to both ends of the primary coil
It is characterized in that it is lower than the voltage to be applied .

[0006]

Since the auxiliary coil is grounded on the primary side, the induced potential is AC low. In addition, since the auxiliary coil is divided into two and arranged in the outermost layer, the laminated coil is vertically symmetrical with respect to the center, and the magnetic coupling characteristics are improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a perspective view showing a configuration of an assembled state according to an embodiment of the present invention. In the drawing, a core 40 is a so-called EE type core,
Here, both side cores 41 have a rectangular cross section, and the midfoot core 42 has a circular cross section. The connecting portion 43 is a core material for connecting the both-side core 41 and the midfoot core 42 and has a rectangular cross section. The printed coil laminate 50 includes a primary coil 10 having a primary winding function of a transformer, a secondary coil 20 having a secondary winding function of a transformer, and an auxiliary coil 30 having an auxiliary winding function. The middle foot core 32 is inserted into a core insertion hole 56 provided at the center, and a magnetic circuit is formed by sandwiching the outside between the cores 31 on both sides. The terminal 60 is used to connect the primary and secondary signal lines when a transformer is used.
And a secondary terminal 62. The connecting portion 43 of the core 40 is provided at the center on the surface of the printed coil laminate 50.
Are located on both sides of the primary terminal 61 and the secondary terminal 62.
Is located.

FIG. 2 is a top view of the printed coil laminate 50. A core insertion hole 56 is located at the center, and a primary connection hole 51 and a secondary connection hole 52 are provided at both left and right ends, respectively.
They are provided in a line. After assembly, the primary connection hole 51
The primary terminal 61 is soldered to the secondary connection hole 52.
The secondary terminal 62 is soldered. The internal connection holes 53 are used to connect a part of the layers inside the printed coil laminate 50 and include a primary connection hole 51 and a secondary connection hole 52.
And near the core insertion hole 56. The conductor forming surface 54 is a region between the core insertion hole 56, the primary connection hole 51, and the secondary connection hole 52 of the printed coil laminate 50, in which a spiral conductor pattern 55 is formed as necessary. I have.

FIG. 3 is an explanatory view of a printed coil laminate.
(A) shows the coil stacking order, and (B) shows the NI distribution. In the figure, the primary coil 10 is changed to Pa and Pb by 2
A secondary coil 2 which is divided and has a secondary winding S between the two
It is sandwiched between 0. The auxiliary coil AUX is divided into two, one auxiliary coil AUXa is placed above the primary coil Pa, and the other auxiliary coil AUXb is placed below the primary coil Pb. That is, both of the outsides of the printed coil laminate (laminated coil) are auxiliary coils, and one end of the auxiliary coil is grounded to the primary winding side.

Vp is an AC voltage applied to both ends of the primary coil. For example, when a commercial AC power supply is used, the voltage is about 100 V. Then, V _AUX is an AC voltage induced at both ends of the auxiliary coil, for example, V _AUX = 1/5 · Vp. At this time, since the electrostatic energy is proportional to the square of the potential, the electrostatic energy is reduced to about 1/25 on the lower surface of the primary coil Pb as compared with the case of FIG. When the electrostatic energy is reduced, interference with surroundings is reduced, and electrostatic noise is reduced. Further, the vertical symmetry of the NI distribution is enhanced, the leakage inductance is reduced, the magnetic characteristics are improved, and the coil loss is reduced. Further, since the stacking order of the printed coil stack is vertically symmetric, the thermal characteristics are also improved.

[0011]

As described above, according to the present invention, the primary coil is divided into two coil surfaces to sandwich the secondary coil, and the auxiliary coil is divided into two and arranged on the outermost layer. In addition, since one end of the auxiliary coil is grounded to the primary winding side, there is an effect that coil loss is reduced and electrostatic noise is reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an assembled state according to an embodiment of the present invention.

FIG. 2 is a top view of the printed coil laminate 50.

FIG. 3 is an explanatory view of lamination of a printed coil laminate.

FIG. 4 is a circuit diagram of a conventional switching power supply.

FIG. 5 is a stacking diagram when a printed coil type transformer is used for each coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Primary coil 20 Secondary coil 30 Auxiliary coil 40 Core 50 Print coil laminated body

Claims (1)

(57) [Claims] 1. A primary coil (10) having a conductor pattern corresponding to a primary winding (n1) of a transformer, and a secondary coil having a conductor pattern corresponding to a secondary winding (n2) of the transformer. A side coil (20) and an auxiliary coil (30) on which a conductor pattern corresponding to an auxiliary winding (n3) of a transformer is laminated, and the primary side coil is divided into two parts.
In the printed coil type transformer sandwiching the secondary coil , the auxiliary coil is divided into two so as to be connected in series and arranged on the outermost layer, and one end of the auxiliary coil is grounded to the primary winding side. And the voltage induced at both ends of the auxiliary coil
Voltage is less than the voltage applied across the primary coil.
A printed coil type transformer characterized by being made smaller .