JPH0722049B2 - Flyback transformer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flyback transformer.

[Prior art]

The flyback transformer 1 generally includes a plurality of secondary windings SC magnetically coupled to a primary winding PC as shown in FIG.
Rectifier diodes D1 to D4 are connected between the secondary windings SC1 to SC4 including 1 to SC4, respectively. And 1
Connected to the next winding PC is a pulse generation circuit 2 including a transistor Tr, a damper diode Od, a resonant capacitor Cp, a DC power supply E, and the like arranged on another circuit board.

Such a conventional flyback transformer 1 generally has a secondary winding SC as shown in FIGS. 16A and 16B.
1 to SC4 is wound around a bobbin 3 with a collar, a split spiral type, or as shown in FIGS. 17A and 17B, each secondary winding SC1 to SC4 is placed on the primary winding PC. There was a split flat winding type, which was wound in a laminated manner in order.

In the flyback transformer 1, it is desired that the voltage fluctuation rate be as small as possible.

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.

[Problems to be Solved by the Invention]

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

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, this power source There was a problem that it affects the function as.

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]

Briefly, the present invention provides a long first insulating sheet,
A first conductor formed on one surface of the first insulating sheet so as to extend in the longitudinal direction thereof, two first terminals attached to the first conductor, and a second laminated on the first insulating sheet. Insulation sheet, second insulation sheet formed on one surface of the second insulation sheet
A conductor, a second terminal attached to a position deviated from the center of the second conductor, and a winding body formed by winding the first and second insulating sheets in a laminated state, A primary winding is formed between the two first terminals by the first conductor, and an LC distributed constant type resonance capacitor connected to the primary winding is formed between the first and second conductors. , A flyback transformer further comprising a secondary winding arranged on the winding body.

[Action]

Generally, in a flyback transformer, the voltage fluctuation rate depends on 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 Vx
Is determined by the vector sum of.

Vf = Vd + (Rd x Ip) Vr = Ip x Rc Vx = ωLl x Ip where Vd: constant Rd: constant Ip: secondary winding peak current Rc: winding resistance ωLl: leakage reactance.

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

When the second terminal is attached at a position deviated from the center of the second conductor, an LC distributed constant type resonance capacitor connected to the primary winding is formed between the first and second conductors. In this way, by making the resonant capacitor of the LC distributed constant type, the combined primary pulse waveform approximates to a rectangular wave, which reduces the peak current Ip flowing through the secondary winding.

〔The invention's effect〕

According to the present invention, the peak current is reduced to reduce the forward voltage drop Vr of 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. In comparison with any of the conventional methods, it is not necessary to add another circuit, and the cost does not increase. That is, the peak current can be reduced only by shifting the mounting position of the second terminal, and thus the circuit configuration need not be changed.

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〕

With reference to FIGS. 1 and 2A and 2B, the flyback transformer 10 of this embodiment includes a film winding body 12.

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. On the upper surface of the second insulating sheet 16, the same conductor foil 20 is provided 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.

In addition, a second terminal 28 is also formed on the second insulating sheet 16 at a position deviated from the center of the second conductor foil 20 in the lengthwise direction, that is, an end portion in this embodiment, similarly by another conductor foil 26. It is attached. 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.

In this film winding body 12, as shown in FIGS. 5A and 5B, the first terminals 24a and 24b and the second terminal 28 are both exposed on one end surface of the film winding body 12.

In the film winding body 12 shown in FIGS. 3, 4, 5A and 5B, the first and second conductor foils 18 and 20 can also be formed by vapor deposition, plating or the like.

The film winding body 12 formed in this manner is formed by the first conductor foil 18 between the first terminals 24a and 24b.
The primary winding PC shown is formed. Therefore, the distance between these first terminals 24a and 24b affects the inductance of the primary winding PC. Therefore, the first terminal 24a
The magnitude of the inductance of the primary winding PC can be appropriately adjusted only by changing the mounting positions of and 24b.

The inductance of such a primary winding PC is the first conductor foil.
18 is divided into a plurality in the width direction to form elongated parallel conductors,
If you connect them in series between the first terminals 24a and 24b,
It can be a larger value. In this way 1
Controls the number of turns (inductance) and mounting capacity of the next winding.

Further, in the film winding body 12, the second insulating sheet 16 which is a dielectric is interposed between the first and second conductor foils 18 and 20, and the second terminal 28 has the second insulating sheet 16. Conductor foil 20
Since it is attached to the end portion in the length direction of, the LC distributed constant type capacitance is formed. This LC distributed constant type capacitance acts as the resonance capacitor Cp shown in FIG.
That is, the resonance capacitor Cp formed by the first and second conductor foils 18 and 20 is equivalently connected to the second terminal 28 at one electrode and to the primary winding Pc at the other electrode. It Therefore, if the first terminal 24a and the second terminal 28 are connected to each other in the external circuit (or may be inside), the resonance capacitor Cp is connected in parallel to the primary winding PC. The capacitance of the resonance capacitor Cp can be appropriately adjusted by the facing area of the first and second conductor foils 18 and 20, the dielectric constant of the second insulating sheet 16, and the mounting position of the second terminal 28.

As in this embodiment, the resonance capacitor Cp is formed as an LC distributed constant by mounting the second terminal 28 on the second conductor 20 so as to be unevenly distributed not at the center but at the end. This is because residual inductance is generated in the second conductor 20. That is, if it is attached to the center, a current flows in the opposite direction on the second conductor 20 with the center second terminal 28 interposed therebetween, thereby canceling out the residual inductance, resulting in the resonance capacitor. Is formed as a lumped constant. On the other hand, in this embodiment, the resonance capacitor Cp is formed as an LC distributed constant. Therefore, the values of the resonance capacitor Cp and the residual inductance can be adjusted by changing the mounting position of the second terminal 28.

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

The secondary windings SC1 to SC4 are preferably 6A
The plating coil 30 shown in the figure and FIG. 6B 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. For example, as shown in FIG. 7, the conductor 34 has 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. 7 on the entire outer surface of the bobbin 32, and then forming a spiral slit 43 by, for example, a laser. The starting end and the terminating end of the conductor 34 are used as the connection terminals 44a and 44b.

By preparing four types of plating coils 30 each having a different bobbin diameter and sequentially fitting them in the film winding body 12, 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.

Although the plated coil 30 is used as the secondary windings SC1 to SC4 in the above embodiment, it is not the plated coil but the 16A coil.
It goes without saying that the same secondary winding as in the prior art shown in FIGS. 16B and 17A and 17B may be wound.

In the flyback transformer 10 thus obtained, since the resonance capacitor Cp is formed as the LC distributed constant type, the composite primary pulse waveform changes from the conventional half sinusoidal wave shown in FIG. 12A to that shown in FIG. 12B. The waveform is close to the rectangular wave shown. As a result, the current flowing through the secondary winding is
The waveform shown in FIG. 13B is not a conventional waveform having a narrow conduction angle Tonl and a large peak value Ip1, but a rectangular wave having a relatively wide conduction angle Ton2 and a relatively small peak Ip2.

Therefore, the peak current Ip becomes smaller than in the conventional case, 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. 14 shows the voltage fluctuation rate of the conventional flyback transformer.

Next, referring to FIG. 8, another flyback transformer 10 of this embodiment includes two film winding bodies 12a and 12b.

Since the film winding bodies 12a and 12b can be configured in the same manner as the film winding body 12 shown in FIG. 3, detailed description thereof will be omitted here.

In this embodiment, as shown in FIGS. 9A and 9B, first, the film winding body 12a is prepared. Secondary windings SC1 to SC4 are sequentially stacked on top of it. Secondary winding SC1
Through SC4, the plating coil 30 shown in FIGS. 6A and 6B is used. After that, the uppermost secondary winding SC4
The insulating sheet 46 is wound on the
12b is wound.

9A and 9B, the first and second terminals of each film winding body are the same as in FIGS. 2A and 2B above or FIGS. 11A and 11B described later. Note that the illustration is omitted to avoid complication of the drawing.

In the flyback transformer 10 thus configured, the two primary windings PC1 and PC2 are driven in parallel.

In the flyback transformer 10 of this embodiment, by setting the LC distribution constants of the two resonance capacitors Cp1 and CP2 to different values, as shown in FIG. 12C, the central time of each synthetic pulse waveform is set to T1.
And T2 so that the waveform is closer to a rectangular wave as a whole. As a result, the current flowing through the secondary winding is
As shown in FIG. C, the waveform has a wider conduction angle Ton3 and a smaller peak current Ip3.

In this embodiment, since the secondary windings SC1 to SC4 are sandwiched between the two film winding bodies 12a and 12b, the primary windings
The magnetic coupling between PC1 and PC2 and the secondary windings SC1 to SC4 is tight. Therefore, the secondary leakage magnetic flux, that is, the secondary leakage inductance can be reduced.

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 B in FIG. 14 shows the case where the primary winding is divided into two, but the respective resonance capacitors are formed as a lumped constant type and the resonance frequencies are set to be equal.

Referring to FIG. 10, the flyback transformer of this embodiment
10 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 12 shown in FIG. 3, detailed description thereof will be omitted here.

In this example, as shown in FIGS. 11A and 11B,
First, the film winding body 12a is prepared. Secondary windings SC1 and SC2 are sequentially stacked on top of it. Secondary winding
The plating coils 30 shown in FIGS. 6A and 6B are used as SC1 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 stacked on the film winding body 12b. Above the secondary windings SC3 and SC4, via an insulating sheet 462,
The film winding body 12c 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 arranged 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, three resonance capacitors Cp1 and Cp2
By setting the LC distribution constants of Cp3 and Cp3 to different values, as shown in FIG. 12D, the center times of the composite pulse waveforms are shifted from T1, T2, and T3, respectively, and the waveform becomes closer to a rectangular wave as a whole. . Along with this, the current flowing through the secondary winding has a waveform having a wider conduction angle Ton4 and a smaller peak current Ip4 as shown in FIG. 13D.

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

By the way, the line C in FIG. 14 shows the case where the primary winding is divided into three, but the respective resonance capacitors are formed as a lumped constant type and the resonance frequencies are set equal.

9A and 9B and FIGS. 11A and 11B.
Also in the illustrated embodiment, the secondary winding may be of a conventional type as shown in FIGS. 16A and 16B and FIGS. 17A and 17B.

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 film winding body in which the first and second insulating sheets are wound, FIG. 5A is a partially cutaway front view, and FIG. 5B is a right side view. . 6A and 6B are schematic views showing a plated coil used as a secondary winding. FIG. 6A is a front view and FIG. 6B is a side view. FIG. 7 is an enlarged sectional view showing a conductor portion of the plating coil shown in FIG. FIG. 8 is a connection diagram showing another embodiment of the present invention. 9A and 9B are schematic views showing the structure of this embodiment, FIG. 9A is a partially cutaway front view, and FIG. 9B is a partially omitted right side view. FIG. 10 is a connection diagram showing another embodiment of the present invention. 11A and 11B are illustrative views showing an embodiment showing the structure of this embodiment, and FIG. 11A is a partially cutaway front view, 11B.
The figure is a right side view with some parts omitted. 12A to 12D are composite primary pulse waveform diagrams,
FIG. 12A is a waveform chart of the prior art, FIG. 12B is a waveform chart of the embodiment of FIG. 1, FIG. 12C is a waveform chart of the embodiment of FIG. 8, and FIG.
FIG. 10 is a waveform chart of the embodiment. 13A to 13D are waveform diagrams of the secondary current.
FIG. A is a waveform chart of the prior art, FIG. 13B is a waveform chart of the embodiment of FIG. 1, FIG. 13C is a waveform chart of the embodiment of FIG. 8, and FIG. 13D is a waveform chart of the embodiment of FIG. FIG. 14 is a graph showing the voltage fluctuation rate of each example together with the comparative example. FIG. 15 is a connection diagram showing a conventional flyback transformer. 16A and 16B are schematic views showing the structure of a conventional split-back winding type flyback transformer.
The figure is a partially cutaway front view, and FIG. 16B is a partially omitted right side view. 17A and 17B are schematic views showing the structure of a conventional split flat winding type flyback transformer. FIG. 17A is a partially cutaway front view, and FIG. 17B is a partially omitted right side view. In the figure, 10 is a flyback transformer, 12, 12a, 12b, 1
2c is a film winding body, 14 is a first insulating sheet, and 16 is a second
Insulation sheet, 18 is the first conductor foil, 20 is the second conductor foil,
24a, 24b, 24a1, 24a2, 24a3, 24b1, 24b2, 24b3 is the first terminal, 28, 281, 282, 283 is the second terminal, 30 is a plated coil,
PC, PC1, PC2 and PC3 are primary windings, Cp, Cp1, Cp2 and Cp3 are resonant capacitors, and SC1 to SC4 are secondary windings.

Claims (2)

[Claims] 1. A long first insulating sheet, and a first insulating sheet formed on one surface of the first insulating sheet so as to extend in the longitudinal direction thereof.
Conductor, two first terminals attached to the first conductor, a second insulating sheet laminated on the first insulating sheet, and a second insulating sheet formed on one surface of the second insulating sheet. And a second terminal attached at a position deviated from the center of the second conductor, and a wound body formed by winding the first and second insulating sheets in a laminated state. An LC distributed constant type, wherein a primary winding is formed between the two first terminals by the first conductor, and is connected to the primary winding between the first and second conductors And a secondary winding disposed on the winding body.
Flyback transformer. 2. The wound body, each of a plurality of sets, the first insulating sheet, the first conductor, the two first terminals, the second insulating sheet, the second conductor, The flyback transformer according to claim 1, further comprising: and the second terminal.