JPH0758650B2 - Flyback transformer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flyback transformer.

[Conventional technology]

As shown in FIG. 12, a conventional flyback transformer 1 generally includes a plurality of secondary windings SC1 to SC4 magnetically coupled to a primary winding PC, and each of the secondary windings SC1 to SC4. S
Rectifier diodes D1 to D4 are connected between C4. The primary winding PC is connected to the pulse generating circuit 2 including a transistor Tr, a damper diode Dd, a resonance capacitor Cp, a DC power source E, and the like arranged on another circuit board.

Such a conventional flyback transformer 1 generally has a secondary winding as shown in FIGS. 13A and 13B.
Split winding type (section winding type) in which SC1 to SC4 are wound around the bobbin 3 with a collar, and FIG. 14A and FIG.
As shown in FIG. 4B, there is a flat winding type in which the respective secondary windings SC1 to SC4 are sequentially wound in a stacked manner from the top of the primary winding PC.

[Problems to be Solved by the Invention]

As a conventional method for improving the voltage fluctuation rate, there are a saturable reactor type, a variable capacitance type, a supply voltage control type and the like.

However, in any of these methods, a separate circuit is added, which increases the cost and takes up space.

Further, since the pulse width fluctuates in the saturable reactor type and the variable capacitance type, and the tertiary voltage fluctuates in the supply voltage control type, when using the output of the flyback transformer as another power source, There was a problem that the function as the power source was affected.

Therefore, a main object of the present invention is to provide a flyback transformer that can more easily improve the voltage fluctuation rate.

[Means for Solving the Problems]

This invention is divided into a plurality of primary windings, one for each
A secondary winding magnetically coupled to the next winding wire and a resonance capacitor added to each primary winding are provided, and the resonance frequencies are shifted from each other by each primary winding and the resonance capacitor. , A flyback transformer.

[Action]

Generally, in a flyback transformer, the voltage fluctuation rate is determined by the forward voltage drop Vf due to the rectifying diode, the voltage drop Vr due to the winding resistance of the primary winding and the secondary winding, and the leakage reactance as shown below. Voltage drop due to
It is determined by the vector sum of Vx.

Vf = Vd + (Rd × Ip) Vr = Ip × Rc Vx = ωL ₁ × Ip where Vd: constant Rd: constant Ip: secondary winding peak current Rc: winding resistance ωL _l : leakage reactance.

Therefore, the present invention is intended to improve the voltage fluctuation rate by reducing the peak current Ip related to all of Vf, Vr and Vx.

When the resonance frequencies of the respective primary windings and the resonance capacitor are shifted from each other, the combined primary pulse waveform approximates to a rectangular wave, which causes the peak current Ip flowing through the secondary winding.
Becomes smaller.

〔The invention's effect〕

According to the present invention, the peak current is reduced to reduce the forward voltage drop Vr due to the diode, the voltage drop Vr due to the winding resistance, and the voltage drop Vx due to the leakage reactance to improve the voltage fluctuation rate. ,
Compared with the conventional methods, there is no need to add another circuit, and the cost does not increase. That is, since the resonance frequency can be shifted only by changing the inductance value of each primary winding and / or the capacitance value of the resonance capacitor, it is not necessary to change the circuit configuration.

Further, since the peak current is suppressed, the noise caused by it is reduced, and a diode with a small rating can be used as the rectifier diode, which further reduces the cost.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

〔Example〕

Referring to FIG. 1, the flyback transformer of this embodiment.
10 includes primary windings PC1 and PC2 divided in two.
Resonant capacitors Cp1 and Cp2 are added to the respective primary windings PC1 and PC2. As described above, as the primary windings PC1 and PC2 to which the resonance capacitors Cp1 and Cp2 are respectively added, preferably, for example, the film winding body 12 as shown in FIG. 3 is used.

As shown in FIG. 3, the film winding body 12 includes elongated first and second insulating sheets 14 and 16, and the first and second insulating sheets 14 and 16 are, for example, polyester films. And so on. On the upper surface of the first insulating sheet 14, a conductor foil 18 made of a highly conductive metal such as aluminum or copper is attached so as to extend continuously in the longitudinal direction. A similar conductor foil 20 is formed on the upper surface of the second insulating sheet 16 on the ground terminal side in the length direction.
Is pasted.

First terminals 24a and 24b are attached to both ends of the conductor foil 18 on the first insulating sheet 14 by fixing different conductor foils 22 by spot welding, for example. That is, the first terminals 24a and 24b are sandwiched between the portions of the substantially rectangular conductor foil 22 that are folded back and spot-welded, and are integrally fixed to the conductor foil 22. Further, the second terminal 28 is attached by another conductor foil 26 to the second conductor foil 20 on the second insulating sheet 16 substantially at the center in the lengthwise direction. That is, the second terminal 28 is sandwiched between the second conductor foil 20 and the conductor foil 26 and integrally fixed by spot welding or the like.

After stacking the first and second insulating sheets 14 and 16 thus formed, the second conductor foil 20 on the upper surface of the second insulating sheet 16 is placed inside as shown in FIG. To
The film winding body 12 is formed by winding the first and second insulating sheets 14 and 16 in a cylindrical shape, and the first terminal 24a is formed.
And 24b and the second terminal 28 are exposed on one end surface of the film winding body 12.

In the film winding body 12 shown in FIGS. 3 and 4, the first and second conductor foils 18 and 20 can also be formed by vapor deposition, plating or the like.

Each of the primary windings is constructed in this manner. In FIGS. 1, 2A and 2B, the film winding body used for the primary winding PC1 to which the resonance capacitor Cp1 is added is formed into a film. The winding body 12a is used as the film winding body 12b, which is used for the primary winding PC2 to which the resonance capacitor Cp2 is added. Similarly, film rolls 12a and 12b
24a1, 24b1 and 24a2, 24b2, and the respective second terminals are identified as 281, 282.

Since both film windings 12a and 12b are considered similarly, only the film winding 12a will be described here. The film winding body 12a is formed by the first conductor foil 18.
The primary winding PC1 shown in FIG. 1 is formed between the first terminals 24a1 and 24b1. Therefore, these first terminals 24a
The distance between 1 and 24b1 affects the inductance of the primary winding PC1. Therefore, the first terminals 24a1 and 24b1
By changing the mounting position of, the magnitude of the inductance of the primary winding PC1 can be adjusted appropriately.

The inductance of the primary winding PC1 as described above is increased by dividing the first conductor foil 18 into a plurality of elongated parallel conductors in the width direction and connecting them in series between the first terminals 24a1 and 24b1. It can be a value. In this way, the number of turns (inductance) of the primary winding and the acquired capacity are controlled.

Further, in the film winding body 12a, since the second insulating sheet 16 which is a dielectric is interposed between the first and second conductor foils 18 and 20, a capacitance is formed. This capacitance acts as the resonance capacitor Cp1 shown in FIG. That is, the resonance capacitor Cp1 formed by the first and second conductor foils 18 and 20 is equivalently connected at its one electrode to the second terminal 281 and at the other electrode of the primary winding PC1.
Connected to. Therefore, in the external circuit (or may be inside), the first terminal 24a1 and the second terminal 24a1
281, the resonance capacitor Cp1 is connected in parallel to the primary winding PC1. The capacitance of the resonance capacitor Cp1 can be appropriately adjusted by the facing area of the first and second conductor foils 18 and 20 and the dielectric constant of the second insulating sheet 16.

By appropriately adjusting the inductance of the primary windings PC1 and PC2 and the capacitance of the resonance capacitors Cp1 and Cp2 determined in this way, the resonance frequencies of the primary windings PC1 and PC2 due to the respective combinations can be shifted from each other. You can

2A and 2B, the secondary windings SC1 to SC4 are sequentially stacked on the film winding body 12a described above.

The secondary windings SC1 to SC4 are preferably the 5A
The plating coil 30 shown in FIG. 5 and FIG. 5B is used. The plating coil 30 includes a hollow bobbin 32 formed in a tubular shape from an insulating resin such as Noryl, polycarbonate, or polyimide, and a spiral conductor 34 is formed on the outer surface of the bobbin 32. This conductor 34 has, for example, as shown in FIG. 6, a three-layer structure in which an electroless plating layer 36 of nickel, an electrolytic plating layer 38 of copper and an electrolytic plating layer 40 of chromium are laminated. Such a spiral conductor 34 is
It is formed by forming a conductor 34 having a three-layer structure as shown in FIG. 6 on the entire outer surface of the bobbin 32, and then forming a spiral slit 42 by, for example, a laser. The start end and the rear end of the conductor 34 are used as the connection terminals 44a and 44b.

Four types of plating coils 30 formed in this way are prepared, each having a different bobbin diameter, and are sequentially fitted into the film winding body 12a. After that, the insulating sheet 46 is wound around the uppermost secondary winding SC4, and the film winding body 12b is wound thereon.
To wind. In this way, the flyback transformer 10 as shown in FIGS. 1 and 2A and 2B is obtained.

Then, as shown in FIGS. 1 and 2A and 2B, the rectifying diodes D1 to D4 are connected between the respective secondary windings SC1 to SC4 using the above-mentioned connection terminals 44a and 44b. Has been done.

In this flyback transformer 10, two primary windings PC1
And PC2 are driven in parallel.

In the flyback transformer 10, the resonance frequency of the primary winding PC1 and the resonance capacitor Cp1 and the resonance frequency of the primary winding PC2 and the resonance capacitor Cp2 are shifted from each other by the above-described method. In this embodiment, the third
By changing the area of the conductor foil 20 shown in the figure, the resonance capacitors Cp1 and Cp2 are set to different capacitance values, for example, 3000 pF and 5000 pF.

As a result, the synthesized primary pulse has a waveform close to a rectangular wave as shown in FIG. 9B, instead of the conventional half sinusoidal wave shown in FIG. 9A. That is, the horizontal output transistor (not shown) is turned off, and at the same time, the two pulses P1 and P2 shown in FIG.
Occurs. Along with this, the current flowing in the secondary winding is
Conventional conduction angle Ton1 shown in FIG. 10A is narrow and peak value Ip1
Is not a large waveform but the conduction angle Ton as shown in Fig. 10B.
2 is a rectangular wave with a relatively wide peak value and a relatively small peak value Ip2.

Therefore, the peak current Ip becomes smaller than in the past, and the forward voltage drop Vf of the diode, the voltage drop Vr due to the winding resistance, and the voltage drop Vl due to the leakage reactance that depend on the magnitude of the peak current Ip are all small As a result, the voltage fluctuation rate can be improved as shown by the line D in FIG.

Incidentally, the line A in FIG. 11 shows the case where the primary winding is not divided, and the line B shows the case where the primary winding is divided into two but the respective resonance frequencies are set equal.

In FIGS. 2A and 2B and FIGS. 8A and 8B described later, the first and second terminals of each film winding body are not shown in order to avoid complication of the drawing. Please note.

Another embodiment of the flyback transformer 10 shown in FIG.
It includes three film rolls 12a, 12b and 12c. Since the film winding bodies 12a, 12b and 12c can be configured in the same manner as the film winding body 11 shown in FIG. 3, detailed description thereof will be omitted here.

In this embodiment, as shown in FIGS. 8A and 8B, first, the film winding body 12a is prepared. Secondary windings SC1 and SC2 are sequentially stacked on top of it. Secondary winding SC
The plating coil 30 shown in FIGS. 5A and 5B can be used as 1 and SC2. And the secondary windings SC1 and S
The film winding body 1 is provided on the C2 via the insulating sheet 461.
2b is wound. Secondary windings SC3 and SC4 are further arranged thereon in a stacked manner. Secondary winding SC3 and SC4
On top of that, the film winding body 12c is provided through the insulating sheet 462.
Is wound.

In this embodiment, the secondary windings SC1 to SC4 are respectively
It is formed by two plated coils. Therefore,
Each of the secondary windings SC1 to SC4 has a shape in which two coils are connected in parallel as shown in FIG. By using the parallel connection of the two coils in this way, it is possible to reduce the DC resistance of the secondary windings SC1 to SC4 and increase the current capacity. Further, even if one of the coils connected in parallel fails, the operation can be continued.

In the flyback transformer 10 of this embodiment, three primary windings PC1, PC2 and PC3 are driven in parallel.

In this embodiment, the respective resonant frequencies of the primary windings PC1, PC2 and PC3 are shifted from each other in the same manner as in the previous embodiment to obtain a composite primary pulse waveform.
As shown in Fig. 9C, the waveform can be closer to a rectangular wave. Therefore, the current flowing through the secondary winding becomes a rectangular wave having a wider conduction angle Ton3 and a smaller peak value Ip3.

As a result, the voltage fluctuation rate of the flyback transformer 10 of this embodiment is further improved as shown by the line E in FIG.

Incidentally, the line C in FIG. 11 shows the voltage fluctuation rate when the primary winding is divided into three parts but the resonance frequencies are equal to each other.

Although the plated coil 30 is used as the secondary windings SC1 to SC4 in the above-mentioned embodiment, the 13th coil is formed on the film winding body 12.
Of course, a secondary winding similar to the conventional one shown in the drawings and FIG. 14 may be wound.

In addition, Figures 2A and 2B and Figures 8A and 8B
In the embodiment shown in the figure, a film winding body incorporating the primary winding and the resonance capacitor was used as the primary winding. However, the resonance capacitor may be configured as a separate component as in the conventional case, and the primary winding may be the same winding as in the conventional case.

Further, the secondary winding does not necessarily have to be sandwiched between the primary windings.

Further, the divided primary windings PC1, PC2 (and PC3) do not necessarily have to be driven in parallel, but may be driven in series.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of the present invention. 2A and 2B are schematic views showing the structure of this embodiment, FIG. 2A is a partially cutaway front view, and FIG. 2B is a partially omitted right side view. FIG. 3 is an exploded perspective view showing an insulating sheet of the film winding body of this embodiment. FIG. 4 is an illustrative view showing a state in which the first and second insulating sheets shown in FIG. 3 are overlapped and rolled up. 5A and 5B are schematic views showing a plated coil used as a secondary winding. FIG. 5A is a front view and FIG. 5B is a side view. FIG. 6 is an enlarged sectional view showing a conductor portion of the plating coil shown in FIG. FIG. 7 is a connection diagram showing another embodiment of the present invention. 8A and 8B are schematic views showing the structure of this embodiment, FIG. 8A is a partially cutaway front view, and FIG. 8B is a partially omitted right side view. 9A to 9C are synthetic primary pulse waveform diagrams.
FIG. 9A is a waveform chart of the prior art, FIG. 9B is a waveform chart of the embodiment of FIG. 1, and FIG. 9C is a waveform chart of the embodiment of FIG. 10A to 10C are waveform diagrams of the secondary current.
FIG. A is a waveform chart of the prior art, FIG. 10B is a waveform chart of the embodiment of FIG. 1, and FIG. 10C is a waveform chart of the embodiment of FIG. FIG. 11 is a graph showing the voltage fluctuation rate of each example together with a comparative example. FIG. 12 is a connection diagram showing a conventional flyback transformer. 13A and 13B are schematic views showing a structure of a conventional split-winding type flyback transformer, FIG. 13A is a partially cutaway front view, and FIG. 13B is a partially omitted right side view. 14A and 14B are schematic views showing the structure of a conventional flyback transformer of the flat winding type. FIG. 14A is a partially cutaway front view, and FIG. 14B is a partially omitted right side view. In the figure, 10 is a flyback transformer, PC1, PC2, PC3
Is the primary winding, Cp1, Cp2, Cp3 are resonant capacitors, SC1 or
SC4 indicates a secondary winding.

Claims (1)

[Claims] 1. A plurality of divided primary windings, a secondary winding magnetically coupled to each of the primary windings, and a resonance capacitor added to each of the primary windings, A flyback transformer in which the resonance frequencies of the respective primary windings and the resonance capacitor are offset from each other.