JPH0864439A - Converter transformer - Google Patents

Abstract

PURPOSE: To provide a transformer which can stabilize an output voltage in the case of variations in the input voltage of a wide range and a load current in a switching power source of frequency control. CONSTITUTION: A first E-shaped core 1 having a central magnetic leg 4 and magnetic legs 5, 6 and a second E-shaped core having a central magnetic leg 8 and magnetic legs 9, 10 longer than those of the first core are brought into contact with one another in the opposed state a gap G1 is provided between the legs 4 and 8, a primary winding coil L1 and a secondary winding coil L2 are wound at the legs 4, 8. The gap G1 is provided in the vicinity of the center of the coil L1 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter transformer used, for example, in a current resonance type switching power supply circuit and the like, and relates to a transformer applied to a current resonance type switching power supply circuit capable of supporting world wide inputs. is there.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of a current resonance type converter circuit. In this figure, E ₁ indicates a DC voltage source for supplying a predetermined DC voltage V _I , and Q ₁ and Q ₂ indicate switching elements composed of transistors or the like that alternately repeat ON / OFF operations. T ₁₁ represents a converter transformer composed of a primary winding coil L ₁₁ having a winding number N _P and secondary winding coils L _12a and L _12b having a winding number N _S. TN1 indicates a connection terminal of the primary winding coil of the transformer T ₁₁ , and TN2 indicates a connection terminal of the secondary winding coil.

C ₁ indicates a resonance capacitor, and the transformer T
_A resonant circuit is constructed with ₁₁ leakage inductances. D ₁ and D ₂ are rectifying diodes, and C ₂ is a smoothing capacitor. The alternating voltage induced on the secondary side of the transformer T ₁₁ is rectified and smoothed to output a predetermined DC voltage V _O. ing.

[0004] 21 denotes an error detection circuit for detecting the output voltage V _O, 22 are switching elements Q on the basis of a detection signal of the detection circuit 21 so that a predetermined output voltage V _O is obtained
₁ shows a control circuit for controlling the switching frequency f _SW of ₁ and Q ₂ so as to attain a predetermined voltage V _O.
Reference numeral 23 indicates a load connected to the switching power supply.

The operation of the current resonance type converter circuit will be briefly described below. First, the switching elements Q ₁ and Q ₂
Are turned on / off alternately so that the transformer T
_An alternating current flows through the primary winding coil L ₁₁ of ₁₁ and the transformer T
_An alternating voltage V _P is generated on the primary side of ₁₁ . This energy is transmitted to the secondary side through the coupling of the transformer T ₁₁ , and the secondary side voltage V _S is generated in the secondary winding coils L _12a and L _12b . This secondary voltage V _S is rectified and smoothed by the diodes D ₁ and D ₂ and the capacitor C ₂ , and the output voltage V _O
Is supplied to the load 23 connected as. The output voltage V _O is detected by the error detection circuit 21, and the switching frequency f _SW is controlled by the control circuit 22 so that the output voltage V _O becomes a predetermined output voltage V _O.

FIG. 6 shows the resonance impedance Z and the switching frequency f of the resonance circuit constituted by the resonance capacitor C ₁ and the transformer T ₁₁ in the above switching operation.
_This shows the _SW relationship. As shown in this figure, in the case of the current resonance type converter circuit, generally, when the switching frequency f _SW becomes higher than the resonance frequency f ₀ , the resonance impedance Z becomes high and the current flows through the primary winding coil L ₁₁ of the transformer T _11. The upper side control is performed so that the output voltage V _O drops as the primary current decreases. For example, a constant frequency characteristic is provided by setting the switching frequency during steady operation to f ₁ and lowering the switching frequency f _SW output from the control circuit 22 when the output voltage V _O decreases.

Next, in FIGS. 7A and 7B, a primary winding coil L ₁₁ and a secondary winding coil ₁₂ used in the current resonance type converter circuit shown in FIG. It is an example of the figure showing the section view and outline of the converter transformer. In this figure, 11 and 12 are iron cores that form the core of the transformer T ₁₁ , and are punched iron cores of the same E-shape formed from the basic iron core 13 to the central magnetic leg 14 and magnetic legs 15 and 16 on both sides thereof. Is.

Further, the iron cores 11 and 12 are abutted against each other while facing each other, and at this time, the central magnetic leg 1 of the iron cores 11 and 12 is contacted.
A gap G ₁₁ is provided between 4 and 14. Then, as shown in FIG. 3B, a primary winding coil L ₁₁ having terminals TN1 and TN1 and a secondary winding coil L ₁₂ having terminals TN2 and TN2 are applied to form a transformer T _11. Has been done.

[0009]

By the way, the current resonance type converter circuit as described above has the advantages of high efficiency and low noise in principle. However, as mentioned above, the frequency control method is the upper side control. Therefore, for example, when the input voltage V _I is small and the current flowing through the load 23 is large, the output voltage V _O decreases and the switching frequency f _SW becomes a low frequency. Then, when the switching frequency f _SW becomes equal to or lower than the resonance frequency f ₀ , the output voltage V _O cannot be controlled.

On the contrary, for example, when the input voltage V _I is large,
When the current flowing through the load 23 is small, the output voltage V _O rises and the switching frequency f _SW becomes high. Then, in accordance with the switching frequency f _SW is high, the switching elements Q _1, Q ₂ by the storage time is a characteristic of low switching element Q ₁ when the frequency was not a problem, Q ₂ (e.g. a bipolar transistor, etc.) The on / off operation cannot be controlled, and the output voltage V _O cannot be controlled. That is, there is a drawback that it is difficult to stabilize the output voltage against a wide range of fluctuations in the input voltage and fluctuations in the load current.

Therefore, the conventional world wide (100V ±
A current resonance type switching power supply circuit cannot be applied to an electronic device such as a television receiver to which a voltage of 20% to 240V ± 20%) is input.
Rectifier circuit for input voltage of V or less, 200V system (150
Since it is necessary to provide a rectifier circuit for an input voltage of V or more) and a switching circuit for switching between them, this is an obstacle to cost reduction.

The present invention has been made in order to solve such a problem, and is a frequency control system using a primary winding coil of a converter transformer such as a current resonance type converter circuit as an inductance of series resonance. Even in a switching power supply circuit, a wide range of input voltage fluctuations,
And a converter transformer in which the output voltage is stabilized against load current fluctuations.

[0013]

[MEANS FOR SOLVING THE PROBLEMS] A primary winding and a secondary winding are provided on a part of a core forming an open magnetic path, and a magnetic field is formed at a central portion of a core region around which the primary winding is wound. A gap is formed. The secondary winding is juxtaposed adjacent to the primary winding.

[0014]

When the transformer is configured as described above, the ratio of the number of windings of the primary winding coil and the number of windings of the secondary winding coil of the transformer becomes maximum, and in a switching power supply circuit in which frequency control is performed, The output voltage can be stabilized against a wide variation of the input voltage and a variation of the load current with a small change in the switching frequency.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An outline of an example of the transformer of the present invention and a case of applying it to a current resonance type converter circuit will be described below in comparison with a conventional transformer. 1 (a),
(B) is an example showing the cross section and outline of the transformer of the present embodiment. In this figure, 1 and 2 are iron cores that form the core of the transformer T ₁ , and the iron core 1 includes the basic iron core 3 to the central magnetic leg 4 And an E-shaped punched iron core formed of magnetic legs 5 and 6 on both sides thereof.

Further, the iron core 2 includes the basic iron core 7 to the central magnetic leg 8.
And an E-shaped punched iron core formed from magnetic legs 9 and 10 on both sides thereof, and a central magnetic leg 8 and magnetic legs 9 on both sides thereof.
Reference numeral 10 denotes a central magnetic leg 4 and magnetic legs 5, 6 forming the iron core 1.
It is longer.

The iron cores 1 and 2 are abutted against each other, and at this time, a gap G ₁ is provided between the central magnetic legs 4 and 8 of the iron cores 1 and 2. And FIG. (B) terminal TN ₁ as illustrated in, TN ₁ 1 winding coil L ₁ has a, and the terminal TN _2, TN 2 winding coil L ₂ is subjected to a transformer having _two T ₁ is formed.

The primary winding coil L ₁ and the secondary winding coil L ₂ are separately arranged so as to obtain an appropriate leakage inductance, but the central magnetic leg 4 of the iron core 1 and the central magnetic leg of the iron core 2 are arranged. The position of the gap G ₁ provided in _No. 8 is set near the center of the primary winding coil L ₁ .

FIG. 2 is a graph showing the inductance L _{P of the} primary winding coil of the transformer on the vertical axis and the position of the gap on the horizontal axis. In this figure, N _P indicates the number of windings of the primary winding coil of the transformer. For example, assuming that the number of windings of the transformer T ₁ of this embodiment is N _P1 , the position of the transformer gap and the primary winding coil The relationship of the inductance L _P is a curve as shown by the solid line. Further, when the number of windings of the transformer T ₁₁ is N _P2 (N _P2 <N _P1 ), the relationship between the position of the transformer gap and the inductance L _P of the primary winding coil is a curve shown by a broken line.

In the coil arrangement as shown in this figure, the inductance L _P of the primary winding coil may take a minimum value when the position of the gap is approximately at the center l ₁ of the primary winding coil. Recognize. That is, for example, when the required value of the inductance of the primary winding coil is L _P1 , by arranging the position of the gap approximately at the center l ₁ of the primary winding coil to obtain the inductance L _P1 , The number N _P can be maximized. However, when the gap is set to the center l ₂ of the core, the number of windings N _P2 becomes smaller because the same inductance value L _P1 is obtained.

Therefore, when the gap is provided in the vicinity of the center l ₁ of the primary winding coil to obtain a predetermined inductance L _P as in the transformer T ₁ of this embodiment, the maximum number of windings is N. _It becomes _P1 , which is larger than the number of windings N _P2 in the case where a gap is provided at the central position l ₂ of the entire transformer to obtain a predetermined inductance L _P as in the conventional transformer T _11. .

Next, a case where the transformer of the present embodiment is applied to the current resonance type converter circuit shown in FIG. 5 will be described in comparison with a case where a conventional transformer is applied. FIG. 3 shows the number of windings N _{P of the} primary winding coil and the voltage V _P applied to the primary winding of the transformer of the current resonance type converter circuit shown in FIG.
It is a figure showing the relation with output voltage V _O. However, FIG. 3 shows the winding number N _P1 of the primary winding coil of the transformer T ₁ of the present embodiment, and the winding number of the primary winding coil of the conventional transformer T _{11 in which} the gap is located at the center of the core. N _P2 (N _P1 ＞
_NP2 ) is the result of measurement with only the transformer replaced. Further, the switching frequency f _sw output from the control circuit 22, the current flowing through the load 23, the number of windings N _{S of} the secondary winding coil, the inductance L _{P of the} primary winding coil is constant, and the switching frequency f _SW is the system. The upper side control is higher than the resonance frequency of.

From FIG. 3, for example, in order to output a predetermined voltage V ₀₁ from the current resonance type converter circuit, the larger the number of windings N _{P of the} primary winding coil of the transformer is (N _P1 > N _P2 ), the primary winding It can be seen that the voltage V _P applied to (V _P1 > V _P2 ) also increases.

Next, FIG. 4 shows the voltage V _P applied to the primary winding coil of the transformer when the switching frequency f _SW is changed.
It is a figure showing the relation with. Here, the curve a is the switching frequency shown in FIG. 5 when the input voltage V _I is maximum and the current flowing through the load 23 is minimum, and the curve b is the switching frequency when the input voltage V _I is minimum and the current flowing through the load 23 is maximum. It is a curve obtained by simulating the relationship between f _SW and voltage V _P.

In order to keep the output voltage V _O at a constant value, it is necessary to keep the voltage V _P applied to the primary winding coil of the transformer constant even if the input voltage and the load current fluctuate. For example the primary winding when winding number of the coil is N _P1 when the voltage value V _P1, the number of windings of the N _P2, it is necessary to stabilize the voltage value V _P2.

From FIG. 4 described above, in order to stabilize the voltage applied to the primary winding coil at V _P1 or V _P2 , within the maximum fluctuation range of the input voltage and the load current of the curves a and b obtained by the above-described simulation. Therefore, the switching frequency f _SW may be controlled by changing it within the range of Δf ₁ and Δf ₂ , respectively, as shown in the figure.

However, when the switching frequency f _SW becomes a high frequency as described above, the on / off control becomes impossible. Therefore, even if the variation Δf is small, the voltage V _P is constant with respect to the fluctuation of the input voltage and the load current. Is desirable. That is, also from this graph, it is clear that Δf ₁ <Δf ₂ , and it is better to control the voltage V _P applied to the primary winding coil of the transformer to a higher voltage V _P1 than to control it by the voltage V _P2 . Small change in switching frequency f _SW Δ
It is possible to keep the voltage V _P constant at f ₁ .

From the above, it is preferable that the primary winding N _P can be set large when one resonance condition is set and the inductance L _P of the primary winding of the transformer is set to a certain value. Therefore, the transformer gap is placed near the center of the primary winding to maximize the number of windings of the primary winding coil and maximize the ratio of the number of windings of the secondary winding coil to (N _p / N _s ). By so doing, it becomes possible to _realize a resonant converter in which the output voltage is stable with respect to a wide input voltage and a load change with a small change in the switching frequency f _SW .

Although the embodiment has been described as being applied to the converter transformer of the current resonance type converter circuit, the converter transformer of the present invention is not limited to the frequency control type switching converter circuit using the primary winding as the inductance of the series resonance. Can be applied to.

[0030]

As described above, according to the present invention,
The frequency control method, which was originally superior to other methods in terms of high efficiency and low noise, was constructed by forming a magnetic gap in the center of the core region where the next winding is wound. It is very useful because it can widen the control range for the input voltage and load fluctuation of the switching converter. In addition, even for world-wide-input electronic devices, it is possible to control with a switching converter of a frequency control system that uses the primary winding of a transformer as a series inductance. Circuits, switching circuits, etc. are not required, and it is possible to significantly reduce the number of parts and reduce the raw material ratio.

[Brief description of drawings]

FIG. 1 is a diagram showing an appearance and a cross section of a transformer.

FIG. 2 is a diagram showing a relationship between a position of a transformer gap and an inductance.

FIG. 3 is a diagram showing a relationship between a primary side voltage and an output voltage of a transformer of a current resonance converter.

FIG. 4 is a diagram showing a relationship between a switching frequency and a primary side voltage with respect to an input voltage and a load change of a current resonance converter.

FIG. 5 is a diagram showing an example of a current resonance type converter.

FIG. 6 is a diagram illustrating a control frequency of a current resonance type converter.

FIG. 7 is a diagram showing an appearance and a cross section of a conventional transformer.

[Explanation of symbols]

 1, 2 Iron core 3, 7 Basic iron core 4, 8 Central magnetic leg 5, 6, 9, 10 Magnetic leg G Gap

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location 9375-5E H01F 31/00 R

Claims (3)

[Claims] 1. A primary winding and a secondary winding are provided on a part of a core forming an open magnetic path, and a magnetic gap is formed at a central portion of a core region around which the primary winding is wound. A converter transformer characterized in that 2. The converter transformer according to claim 1, wherein the secondary winding is juxtaposed adjacent to the primary winding. 3. The converter transformer according to claim 1, wherein the converter transformer is applied to a current resonance type switching power supply circuit.