JP4387142B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device that supplies a DC stabilized voltage to industrial and consumer electronic devices.

  In recent years, with the miniaturization of electronic devices, there is a strong demand for miniaturization and thinning of magnetic parts such as transformers used in switching power supply devices. In order to meet such demands, as a transformer winding of a switching power supply device, a coil in which a conductive wire is wound in a spiral shape and a spiral coil in which a thin conductor is punched out are used. Laminated transformers are used.

A conventional switching power supply device will be described below with reference to FIG.
FIG. 6 is a conventional switching power supply device, FIG. 6A is a circuit configuration diagram of a full bridge converter, FIG. 6B is a cross-sectional view of a winding portion of the transformer, and FIG. It is an external view of the spiral coil which is one of the windings of the part.
6A includes an input DC power supply 1, an input terminal 2a-2b, a transformer 3, a first switching element 4, a second switching element 5, a third switching element 6, and a fourth switching. The device 7 includes a first rectifier diode 8a, a second rectifier diode 8b, an inductance element 9, a smoothing capacitor 10, output terminals 11a-11b, a load 12, and a control circuit 20. G1, G2, G3 and G4 indicate turn-on signals generated by the control circuit 20.
The input DC power supply 1 is connected to the input terminals 2a-2b and supplies a power supply voltage Vin.
The first switching element 4 and the second switching element 5 are connected in series and connected to the input terminals 2a-2b. The third switching element 6 and the fourth switching element 7 are connected in series and connected to the input terminals 2a-2b.

One end of the primary winding 3a is connected to the connection point between the first switching means 4 and the second switching means 5, and the other end is connected to the connection point between the third switching means 6 and the fourth switching means 7. Connected. The first secondary winding 3b and the second secondary winding 3c are connected in series. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1 (N is an arbitrary positive number).
The anode of the first rectifier diode 8a is connected to one end of the first secondary winding 3b of the transformer 3, and the anode of the second rectifier diode 8b is connected to one end of the second secondary winding 3c. ing. The cathodes of both rectifier diodes are connected to each other. The other end of the first secondary winding 3b and the other end of the second secondary winding 3c are connected to each other and connected to the output terminal 11b.

The inductance element 9 and the smoothing capacitor 10 are connected in series to constitute a smoothing circuit. One end of the inductance element 9 is connected to a connection point between the cathode of the first rectifier diode 8a and the cathode of the second rectifier diode 8b, and the other end is connected to the output terminal 11a. One end of the smoothing capacitor 10 is connected to the output terminal 11a, and the other end is connected to a connection point (output terminal 11b) between the first secondary winding 3b and the second secondary winding 3c.
The smoothing capacitor 10 has a sufficiently large capacitance and rectifies and smoothes the voltage generated in the secondary winding of the transformer 3. The voltage Vout (voltage between 11a-11b) across the smoothing capacitor 10 becomes the output voltage.
A load 12 is connected to the output terminals 11a-11b and consumes power.
A control circuit 20 outputs the turn-on signals G1 to G4 to stabilize the output DC voltage Vout, whereby the first switching element 4, the second switching element 5, the third switching element 6 and the fourth switching element are output. The switching element 7 is driven at a predetermined on / off ratio.

The transformer 3 will be described in detail with reference to FIGS. 6B and 6C. 6B is a cross-sectional view of the transformer winding portion, and FIG. 6C is an external view of the spiral coil.
As shown in FIG. 6B, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first 2 It has a secondary coil 3b1, a second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.
The first primary coil 3a1, the second primary coil 3a2, the third primary coil 3a3, and the fourth primary coil 3a4 are connected in series to form the primary winding 3a of FIG. . The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth 2 The secondary coil 3c2 is connected in series and constitutes the second secondary winding 3c of FIG.
Regarding the stacking order of each coil, the first primary coil 3a1, the first secondary coil 3b1, the second primary coil 3a2, the third secondary coil 3b2, the third primary coil 3a3, The second secondary coil 3c1, the fourth primary coil 3a4, and the fourth secondary coil 3c2 are stacked in this order.
By laminating in this way, it becomes possible to increase the magnetic coupling between the primary coil and the secondary coil. FIG. 6C is an external view of one winding of the winding portion of the transformer 3.

The operation of the switching power supply device configured as described above will be described.
FIG. 7 shows an operation waveform diagram of each part of a conventional switching power supply device. 7A shows the voltage waveform of the signal G1 for controlling the on / off of the first switching element 4, and FIG. 7B shows the voltage waveform of the signal G2 for controlling the on / off of the second switching element 5. In FIG. (C) is a voltage waveform of the signal G3 for controlling on / off of the third switching element 6, and (d) is a voltage waveform of the signal G4 for controlling on / off of the fourth switching element 7. (E) is a waveform of the voltage Vp applied to the primary winding 3 a of the transformer 3. (F) is a waveform of the current Id1 flowing through the first rectifier diode 8a, and (g) is a waveform of the current Id2 flowing through the second rectifier diode 8b.

As shown in FIG. 7, in the conventional power supply apparatus, the switching element 4 and the switching element 7 are turned on simultaneously as a set, and the switching element 5 and the switching element 6 are turned on simultaneously as a set. By alternately turning them on and off, the voltages of Vin and -Vin are alternately applied to the primary winding 3a of the transformer 3.
First, when the second switching element 5 and the third switching element 6 are simultaneously turned on by the turn-on signals G2 and G3 from the control circuit 20, a voltage of −Vin is applied to the primary winding 3a of the transformer 3. . At this time, a voltage -Vin / N is generated in the first secondary winding 3b of the transformer 3, the first rectifier diode 8a is turned off with reverse bias, and the second rectifier diode 8b is forward biased. Turn on.

Next, after both G2 and G3 are turned off by the turn-on signal from the control circuit 20, the first switching element 4 and the fourth switching element 7 are simultaneously turned on by the turn-on signals G1 and G4 from the control circuit 20. Then, the input voltage Vin is applied to the primary winding 3 a of the transformer 3. At this time, a voltage Vin / N is generated in the first secondary winding 3b of the transformer 3, the first rectifier diode 8a is turned on with forward bias, and the second rectifier diode 8b is reverse biased. Turn off. A current based on the voltage induced in the first secondary winding 3 b of the transformer 3 is passed through the inductance element 9.
The current flowing through the inductance element 9 increases linearly. At this time, the current flowing through the inductance element 9 flows through the first secondary winding 3b of the transformer 3, and the current of the winding ratio of the transformer 3 (1 / N times) flows through the primary winding 3a of the transformer 3. Flowing.
When both the second switching element 5 and the third switching element 6 are turned off, the primary winding 3a of the transformer 3 is opened, and the first secondary winding 3b and the second secondary winding 3c of the transformer 3 are opened. The induced voltage of becomes zero. In order to maintain the continuity of the magnetic flux of the transformer 3, a current flows in a divided manner to the first secondary winding 3b and the second secondary winding 3c of the transformer 3. Hereinafter, a period in which a current flows through the transformer secondary winding is described as a shunt period.

JP-A-6-302443

In the shunting period, the current flowing through the first secondary winding 3b and the second secondary winding 3c is strong in the space between the first secondary winding 3b and the second secondary winding 3c. Magnetic field is generated. In the shunting period, the primary winding 3a is in an open state, so that the current is zero between the terminals of the primary winding 3a. Therefore, the current sum of the entire conductor of the third primary coil 3a3 located between the first secondary winding 3b and the second secondary winding 3c is zero on the surface thereof. There is a problem that a loop current is induced due to a strong magnetic field generated by the first secondary winding 3b and the second secondary winding 3c, and a loss is generated by the induced current.
For example, in a transformer having a configuration in which a primary winding and a secondary winding are completely separated by winding a normal wire around an EI cut core, the average distance between the primary winding and the secondary winding is long. In addition, there is a problem that sufficient magnetic coupling cannot be obtained between the primary winding and the secondary winding. Therefore, the switching power supply device using the transformer having the above configuration has a problem that high conversion efficiency cannot be obtained.
The present invention solves the above-described problems, and an object of the present invention is to provide a switching power supply device having high conversion efficiency using a transformer having high magnetic coupling between the primary winding and the secondary winding and low loss. And

In order to solve the above problems, the present invention has the following configuration. The invention according to claim 1 includes at least a first primary coil, a first secondary coil, a second secondary coil, and a second primary coil, wherein the first primary coil, A unit laminated body in which the first secondary coil, the second secondary coil, and the second primary coil are laminated in this order; at least the first primary coil; the first secondary coil; A second secondary coil, the second primary coil, and the first primary coil, the second secondary coil, the first secondary coil, and the second primary coil. One end of the first secondary coil in which any one of the unit laminated bodies sequentially laminated is laminated in a plurality of stages, or both are laminated in a plurality of stages, and the plurality of unit laminated bodies are respectively connected. And a transformer connected to one end of the second secondary coil. , Switching means for alternately applying a voltage to the transformer in positive and negative directions, the center tap of the transformer, and the other end of the first secondary coil respectively connected to a plurality of unit laminates, or the second Rectifying means for rectifying the voltage induced between the other end of the secondary coil, smoothing means for smoothing the voltage of the rectifying means, and control for performing on / off control of the switching means so that the output voltage becomes constant And a switching power supply device.
A unit laminate in which the top and bottom are reversed (for example, the second primary coil, the second secondary coil, the first secondary coil, the unit laminate in the order of the first primary coil, or the second 1 A unit laminate including a secondary coil, a first secondary coil, a second secondary coil, and a first primary coil may be stacked.

The invention according to claim 2 is the switching power supply device characterized in that in the transformer, all the primary coils are connected in series.

According to a third aspect of the present invention, in the transformer, the primary coil used in the unit laminate body is connected in parallel to form a parallel connection body, and the parallel connection bodies are connected in series, respectively. Device.

According to a fourth aspect of the present invention, in the transformer, the primary coil and the secondary coil are composed of a printed circuit board coil provided with a conductor pattern on an insulating substrate, and are laminated in multiple stages. Is a switching power supply characterized in that it is connected via a connection portion at the inner end or outer end of the coil pattern to constitute a winding.

According to a fifth aspect of the present invention, in the transformer, the number of turns of the primary coil and / or the secondary coil is one turn in each layer or in the whole. A printed circuit board (layer) having a coil pattern of one turn is laminated, and the whole is connected in series or in parallel to form a primary winding and / or a secondary winding.
For example, when the voltage applied to the primary winding is higher than a predetermined voltage, a creepage distance of a certain level or more must be ensured between the primary winding, the secondary winding, and the core according to safety standards. If the coil pattern exceeds one turn, it is necessary to provide a through hole at the inner end of the coil pattern. However, if a through hole is provided and a creepage distance of a certain level or more is ensured between the through hole and another pattern or core, there is a problem that the transformer becomes large. In the present invention, it is not necessary to provide a through hole at the inner end of the coil pattern for the winding having the coil pattern on the substrate as one turn. According to the present invention, a small and thin transformer can be realized.

According to a sixth aspect of the present invention, in the transformer, in each layer or in total, the number of turns of the primary coil is N turns (N is an arbitrary positive number), and the first secondary coil and the second secondary coil The switching power supply device is characterized in that the number of turns is one turn.
In the transformer of the switching power supply device of the present invention, the turns ratio of the primary coil, the first secondary coil, and the second secondary coil is N: 1: 1.
A printed circuit board having an N-turn coil pattern is laminated, and the whole is connected in series or in parallel to form a primary winding. A printed circuit board having a coil pattern of one turn is laminated, and the whole is connected in series or in parallel to form a secondary winding. The secondary winding is connected through a connection portion at the outer end of the coil pattern. According to the present invention, a small and thin transformer can be realized.
The present invention has an effect of realizing a switching power supply device having high conversion efficiency using a transformer having high magnetic coupling between the primary winding and the secondary winding and low loss.

According to the present invention, it is possible to obtain an advantageous effect that a switching power supply device having high conversion efficiency using a transformer having high magnetic coupling between the primary winding and the secondary winding and low loss can be realized.
According to the switching power supply device of the present invention, the current between the first secondary winding and the second secondary winding is divided between the first secondary winding and the second secondary winding in the shunting period. Even if a strong magnetic field is generated in this space, since no conductor exists between the first secondary winding 3b and the second secondary winding 3c, no current is induced and no loss occurs. Effects can be obtained. Further, currents in opposite directions flow in the first secondary winding 3b and the second secondary winding 3c adjacent to each other during the shunting period, and magnetic fields induced by the two currents cancel each other. Therefore, there is an advantageous effect that no current is induced in the primary winding sandwiched between the first secondary winding 3b and the second secondary winding 3c, and no loss occurs.
Further, since the average distance between the first secondary winding and the second secondary winding is short, the magnetic coupling between the first secondary winding and the second secondary winding becomes high. Therefore, an advantageous effect that a switching power supply device with high conversion efficiency can be provided is obtained.

  Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.

A switching power supply device according to a first embodiment of the present invention will be described with reference to FIG.
The overall circuit configuration of the switching power supply according to the present embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device according to the present embodiment is characterized by the winding portion of the transformer 3, and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device.
Hereinafter, the configuration of the winding portion of the transformer 3 of the switching power supply device of this embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view of the transformer 3 of this embodiment.
As shown in FIG. 1, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first secondary coil 3b1. , A second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.

The first primary coil 3a1, the second primary coil 3a2, the third primary coil 3a3, and the fourth primary coil 3a4 are connected in series to form the primary winding 3a of FIG. . The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth 2 The secondary coil 3c2 is connected in series and constitutes the second secondary winding 3c in FIG. The first secondary winding 3b and the second secondary winding 3c are connected in series. So far, it is the same as the conventional example.
Regarding the stacking order of the coils, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1 (N is an arbitrary positive number).

Also in the present embodiment, as in the conventional example, the first secondary winding 3b and the second secondary winding are caused by the current flowing in the first secondary winding 3b and the second secondary winding 3c in the shunt period. A strong magnetic field is generated in the space between the windings 3c. However, in the winding configuration of this embodiment, there is no conductor between the first secondary winding 3b1 and the second secondary winding 3c1, so no current is induced between them and loss occurs. do not do. In the adjacent first secondary winding 3b2 and second secondary winding 3c2, currents in opposite directions flow in the shunt period, and magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow in the adjacent first secondary winding 3b1 and second secondary winding 3c1 during a shunt period, and magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .
The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is high as in the conventional example (FIG. 6). For example, compared with a transformer in which a primary winding and a secondary winding are completely separated and wound on an EI cut core, the magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention The degree is high.

In the switching power supply of this embodiment, the transformer windings are the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from the top. Although the description has been given using the two-layered unit laminated body laminated in this order, the same effect can be obtained by applying at least one unit laminated body having one or more layers. Here, FIG. 2 shows a cross-sectional view of the transformer winding portion in the one-stage model of the unit laminate body. In the one-layer model of the unit laminate body, no conductor is present between the first secondary winding and the second secondary winding, so no current is induced between them and no loss occurs.
For example, in a transformer in which unit laminated bodies composed of 3a1 to 3a4, 3b1, 3b2, 3c1 and 3c2 shown in FIG. 1 are laminated in two stages, the adjacent first secondary winding 3b2 and second secondary winding are arranged. In 3c2, currents in opposite directions flow during the shunt period, and the magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow in the adjacent first secondary winding 3b1 and second secondary winding 3c1 during a shunt period, and magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .

  A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, The secondary secondary coil 3c1, the first secondary coil 3b1, and the second primary coil 3a2 may be laminated in combination to form a transformer. Furthermore, a transformer may be configured by laminating the unit laminated bodies upside down. Even with such a configuration, the same effect as the embodiment can be obtained.

  By connecting the primary coils in series, it is possible to prevent an extremely uneven current distribution of the current flowing through each primary coil. Although the case where the coils constituting the first secondary winding 3b and the second secondary winding 3c are connected in series has been described, the coils are connected in parallel to form the first secondary winding 3b and It goes without saying that the same effect can be obtained even if the second secondary winding 3c is configured. In the simulation and experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared to the conventional transformer winding configuration (FIG. 6B). It was confirmed. Further, although the description has been made with a full-bridge converter type switching circuit, the same applies when applied to a half-bridge converter, a push-pull converter, and a switching power supply device using various circuit methods based on the circuit. Needless to say, an effect can be obtained.

A switching power supply apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS.
The overall circuit configuration of the switching power supply according to the present embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device according to the present embodiment is characterized by the winding portion of the transformer 3, and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device.
Hereinafter, the configuration of the winding portion of the transformer 3 of the switching power supply device of this embodiment will be described with reference to FIG. FIG. 3 is a sectional view of the transformer 3 of this embodiment.
As shown in FIG. 3, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first secondary coil 3b1. , A second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.

The first primary coil 3a1 and the second primary coil 3a2 are connected in parallel to form a first parallel connection body 3d1, and the third primary coil 3a3 and the fourth primary coil 3a4 are connected in parallel. The 2nd parallel connection body 3d2 is comprised. The first parallel connection body 3d1 and the second parallel connection body 3d2 are connected in series to form the primary winding 3a of FIG. The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth 2 The secondary coil 3c2 is connected in series and constitutes the second secondary winding 3c of FIG. The first secondary winding 3b and the second secondary winding 3c are connected in series.
Regarding the stacking order of the coils, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1.

By configuring the transformer winding as in this embodiment, the first parallel connection body 3d1 and the second parallel connection body 3d2 are connected in series even in the case of a specification with a small turn ratio of the primary winding 3a. As a result, a large current can flow through the primary winding 3a.
Similarly to the first embodiment, since no conductor exists between the first secondary winding 3b1 and the second secondary winding 3c1, the current is caused by a strong magnetic field generated in the space during the shunting period. It is not induced and no loss occurs. In the adjacent first secondary winding 3b2 and second secondary winding 3c2, currents in opposite directions flow in the shunt period, and magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow in the adjacent first secondary winding 3b1 and second secondary winding 3c1 during a shunt period, and magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .
The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is high as in the conventional example (FIG. 6). For example, compared with a transformer in which a primary winding and a secondary winding are completely separated and wound on an EI cut core, the degree of magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention is high.

In the switching power supply device of this embodiment, the transformer windings are the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from above. Although the description has been made by using the two-layer laminated unit laminated bodies, the same effect can be obtained by applying at least one layer laminated body. Here, FIG. 4 shows a cross-sectional view of the transformer winding portion in the one-stage model of the unit laminate body. In the one-layer model of the unit laminate body, no conductor is present between the first secondary winding and the second secondary winding, so no current is induced between them and no loss occurs. Moreover, although the case where the parallel connection bodies of the primary coils in the unit laminate body are connected in series has been described, the same effect can be obtained even when the parallel connection bodies are connected in parallel.
A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, The secondary secondary coil 3c1, the first secondary coil 3b1, and the second primary coil 3a2 may be laminated in combination to form a transformer. Furthermore, a transformer may be configured by laminating the unit laminated bodies upside down. Even with such a configuration, the same effect as the embodiment can be obtained.

  Although the case where the coils constituting the first secondary winding 3b and the second secondary winding 3c are connected in series has been described, the first secondary winding 3b can be obtained by connecting the coils in parallel. It goes without saying that the same effect can be obtained even if the second secondary winding 3c is configured. In the simulation and experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared to the conventional transformer winding configuration (FIG. 6B). It was confirmed. Further, although the description has been made with a full-bridge converter type switching circuit, the same applies when applied to a half-bridge converter, a push-pull converter, and a switching power supply device using various circuit methods based on the circuit. Needless to say, an effect can be obtained.

A switching power supply device according to Embodiment 3 of the present invention will be described with reference to FIG.
The overall circuit configuration of the switching power supply according to the present embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device according to the present embodiment is characterized by the winding portion of the transformer 3, and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device.

  FIG. 5A is a perspective view showing an outer shape of a transformer having a structure in which printed circuit board coils of the present embodiment are laminated, FIG. 5B is a front view thereof, and FIG. 5C is cut along a plane I-I. FIG. 5 (d) is a diagram showing a schematic appearance of one printed board coil. In FIG. 5, 30 is a laminated body in which a plurality of printed circuit board coils are laminated, 34 is a terminal, 35 is a core, and 37 is one printed circuit board coil. Each printed circuit board coil 37 has a coil pattern 31, an inner end through hole 32, and an outer end through hole 33, and a through hole 36 is provided at the center. As shown in FIG. 5 (c), the core 35 has a mid-foot portion that penetrates the through hole 36 to constitute a magnetic closed circuit.

  In the transformer of this embodiment, a laminated body 30 in which a printed circuit board coil 37 having a conductor pattern formed on an insulating substrate is laminated in multiple layers is used as a winding of the transformer. The printed circuit board coil 37 is a printed circuit board having four or more layers, and one printed circuit board may have a plurality of layers of coils. The multilayer printed circuit board coil 37 is laminated with an insulating layer having a necessary thickness between each coil pattern, and the terminals (inner end 32 and outer end 33) of each coil pattern are connected to the other printed circuit board coils 37 above and below. Configure the coil. For example, the conductor pattern provided on the back surface of the printed circuit board coil 37 that is a double-sided printed circuit board connects the inner end 32 and any one of the through holes 38 to 44 provided in the periphery of the printed circuit board coil 37. A terminal 34 is connected to the through hole and the outer end 33 to connect the upper and lower printed circuit board coils 37 to each other. For example, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, the third secondary coil 3b2, Each of the four secondary coils 3c2 and the fourth primary coil 3a4 is provided with a different conductor pattern, and a different through hole is used as a connection terminal, thereby forming each winding of the transformer.

Hereinafter, the configuration of the winding portion of the transformer 3 of the switching power supply device of this embodiment will be described with reference to FIG. Connection and lamination of the coils of the transformer 3 of this embodiment are the same as those of the first embodiment shown in FIG. FIG. 1 is a cross-sectional view of the transformer 3 of this embodiment.
In FIG. 1, a first primary coil 3 a 1, a second primary coil 3 a 2, a third primary coil 3 a 3, and a fourth primary coil 3 a 4 are formed through a through hole 32 at the inner end of the coil pattern 31 and outside the coil pattern 31. The primary winding 3a of FIG. 6 is configured in series through the end through-hole 33.

The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series via the through hole 32 at the inner end of the coil pattern 31 and the through hole 33 at the outer end, and the first secondary winding of FIG. 3b, and the second secondary coil 3c1 and the fourth secondary coil 3c2 are connected in series via the through hole 32 at the inner end of the coil pattern 31 and the through hole 33 at the outer end. Secondary winding 3c. The first secondary winding 3b and the second secondary winding 3c are connected in series.
Regarding the stacking order of the coils, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1.

With this configuration, it is possible to manufacture a transformer in which the interlayer distance between the coils is constant with high accuracy.
Similarly to the first embodiment, since no conductor exists between the first secondary winding 3b1 and the second secondary winding 3c1, the current is caused by a strong magnetic field generated in the space during the shunting period. It is not induced and no loss occurs. In the adjacent first secondary winding 3b2 and second secondary winding 3c2, currents in opposite directions flow in the shunt period, and magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow in the adjacent first secondary winding 3b1 and second secondary winding 3c1 during a shunt period, and magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. . The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is high as in the conventional example (FIG. 6). For example, compared with a transformer in which a primary winding and a secondary winding are completely separated and wound on an EI cut core, the degree of magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention is high.

In the switching power supply of this embodiment, the transformer windings are the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from the top. The multi-layer printed circuit board coil in which the unit laminated bodies laminated in this order are laminated in two stages has been described, but the same effect can be obtained by applying a laminate in which at least one stage is laminated. In the one-layer model of the unit laminate body, no conductor is present between the first secondary winding and the second secondary winding, so no current is induced between them and no loss occurs.
Moreover, although the case where each coil which comprises the 1st secondary winding and the 2nd secondary winding was connected in series was demonstrated, by connecting each coil in parallel, a 1st secondary winding and It goes without saying that the same effect can be obtained even if the second secondary winding is configured.

  A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, The secondary secondary coil 3c1, the first secondary coil 3b1, and the second primary coil 3a2 may be laminated in combination to form a transformer. A transformer may be configured by laminating including these unit laminated bodies that are upside down. Even with such a configuration, the same effect as the embodiment can be obtained. In the simulation and experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared to the conventional transformer winding configuration (FIG. 6B). It was confirmed.

It should be noted that the number of turns of the primary coil may be one turn in each layer constituting the printed circuit board coil 37 or in the transformer 3. The number of turns of the secondary coil may be one turn in each layer constituting the printed circuit board coil 37 or in the transformer 3. In the transformer 3, the number of turns of the primary coil may be N turns and the number of turns of the first secondary coil and the second secondary coil may be 1 turn in each layer constituting the printed circuit board coil 37 or the whole. By making the coil pattern of each layer constituting the printed circuit board coil 37 one turn and further connecting the coil patterns of all layers in parallel, the total number of turns of the coil can be one turn.
Preferably, the number of turns of the coil pattern of the primary coil of each layer constituting the printed circuit board coil 37 is one turn, and all are connected in series or in parallel. Furthermore, the number of turns of the coil pattern of the secondary coil of each layer constituting the printed circuit board coil 37 is one turn, and all are connected in series or in parallel.

When the number of coil turns in each layer is made larger than one turn, the coil pattern 31 becomes spiral. Therefore, it is necessary to provide a through hole 32 at the inner end of the coil pattern and connect the coil patterns in each layer by the through hole 32. When the input voltage on the primary side is a predetermined high voltage or more, the creepage distance between the primary coil, the secondary coil, and the core 35 must be a distance conforming to safety standards (for example, 10 mm) or more. However, securing the predetermined creepage distance and providing the through hole 32 at the inner end of the coil pattern causes an increase in the size of the transformer 3 and an increase in power loss. Furthermore, the connection portion by the through hole 32 at the inner end of the coil pattern has a small current capacity, so that a large current cannot flow through the coil.
By using a one-layer, one-turn configuration, the connection by the through hole 32 at the inner end of the coil pattern is completely unnecessary. A circuit board which does not have a through hole and is formed of a predetermined material itself serves as an insulating sheet. In this case, the spatial distance between the primary coil, the secondary coil, and the core 35 can be narrowed, and an effective creepage distance according to the safety standard can be secured. Thereby, it is possible to reduce the size and thickness of the transformer, increase the input / output current capacity, and reduce power loss.

Although described with a full-bridge converter type switching circuit, the same effect can be obtained when applied to a half-bridge converter, a push-pull converter, and a switching power supply device using various circuit methods based on the circuit. Needless to say, you can get it.
As in the third embodiment, it is needless to say that the transformer of the second embodiment and a switching power supply device using the same can be realized by a configuration in which printed circuit board coils are stacked.

  The switching power supply device according to the present invention is useful as a switching power supply device that supplies a stabilized DC voltage to industrial and consumer electronic devices.

Sectional drawing of the transformer coil | winding part of the switching power supply device of Example 1 Sectional drawing of the transformer coil | winding part of the unit laminated body structure of the switching power supply device of Example 1 Sectional drawing of the transformer coil | winding part of the switching power supply apparatus of Example 2 Sectional drawing of the transformer coil | winding part of the unit laminated body structure of the switching power supply apparatus of Example 2 FIG. 5A is a perspective view of a transformer of the switching power supply device according to the third embodiment, FIG. 5B is a front view thereof, FIG. 5C is a cross-sectional view taken along a plane I-I, and FIG. d) A diagram showing a schematic appearance of one printed circuit board coil. 6A is a circuit diagram of a conventional switching power supply device, FIG. 6B is a cross-sectional view of a transformer winding portion of the switching power supply device, and FIG. 6C is a transformer winding portion of the switching power supply device. Outline drawing of one winding Operation waveform diagram of each part of the conventional switching power supply

Explanation of symbols

1 Input DC Power Supply 2a-2b Input Terminal 3 Transformer 3a Primary Winding 3a1 First Primary Coil 3a2 Second Primary Coil 3a3 Third Primary Coil 3a4 Fourth Primary Coil 3b First Secondary Winding 3b1 First secondary coil 3b2 Third secondary coil 3c Second secondary winding 3c1 Second secondary coil 3c2 Fourth secondary coil 4 First switching element 5 Second switching element 6 third switching element 7 fourth switching element 8a first rectifier diode 8b second rectifier diode 9 inductance element 10 smoothing capacitor 11a-11b output terminal
DESCRIPTION OF SYMBOLS 12 Load 20 Control circuit 30 Laminated body 31 Coil pattern 32 Through hole of inner end 33 Through hole of outer end 34 Terminal 35 Core 36 Through hole 37 Printed circuit board coil 38-44 Through hole

Claims (6)

At least a first primary coil, a first secondary coil, a second secondary coil, and a second primary coil, the first primary coil, the first secondary coil, the first 2 secondary coils, a unit laminate layered in the order of the second primary coil, at least the first primary coil, the first secondary coil, the second secondary coil, the first A unit laminated body having two primary coils, the first primary coil, the second secondary coil, the first secondary coil, and the second primary coil being laminated in this order; One end of the first secondary coil and the second secondary coil, each of which is laminated in a plurality of stages, or in a combination of both and laminated in a plurality of stages, each of which is connected to a plurality of unit laminates. A transformer having a configuration in which one end is connected and taken out as a center tap;
Switching means for alternately applying a voltage to the transformer in positive and negative directions; and
Rectification for rectifying a voltage induced between the center tap of the transformer and the other end of the first secondary coil or the other end of the second secondary coil respectively connected to a plurality of unit laminated bodies. Means,
Smoothing means for smoothing the voltage of the rectifying means;
And a control means for performing on / off control of the switching means so that the output voltage becomes constant. The switching power supply according to claim 1 , wherein all the primary coils are connected in series in the transformer. The switching power supply according to claim 1 , wherein in the transformer, primary coils used in the unit laminated body are connected in parallel to form a parallel connection body, and the parallel connection bodies are connected in series. In the transformer, the primary coil and the secondary coil are composed of printed circuit board coils provided with a conductor pattern on an insulating substrate, and are laminated in multiple stages. The primary coil and the secondary coil are arranged at the inner end or the outer end of the coil pattern. the switching power supply device according to any of claims claims 1 to 3, characterized in that it constitutes a connected winding via connection. 5. The switching power supply device according to claim 4, wherein the number of turns of the primary coil and / or the secondary coil is one turn in each layer or in the transformer. In the transformer, the number of turns of the primary coil is N turns (N is an arbitrary positive number), and the number of turns of the first secondary coil and the second secondary coil is 1 turn in each layer or the whole. The switching power supply device according to claim 1 , claim 4 or claim 5 .

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