JP2019146359A - Switching power supply device - Google Patents

Abstract

To provide a switching power supply device capable of reducing losses in laminated transformers and increase efficiency.SOLUTION: A laminated transformer 30 in a switching power supply device includes: a primary winding 31 which has a plurality of first conductive coil layers 37b and to which an output voltage of a resonance circuit is applied; and secondary windings 32 and 33 having a plurality of second conductive coil layers 38b, 39b and outputting a second AC voltage and a second AC current. In the laminated transformer 30, the plurality of first conductive coil layers 37b and the second conductive coil layers 38b, 39b are laminated, and only a wiring width of the first conductive coil layer 37b having a large potential difference between the opposing first conductive coil layer 37b and the second conductive coil layers 38b and 39b becomes narrower than wiring widths of the first conductive coil layers 37b other than the first coil layer 37b having the large potential difference.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a switching power supply device such as an LLC resonant converter using a laminated transformer (laminated transformer) formed by laminating a plurality of windings (coils) on an iron core (core).

  Patent Documents 1 to 3 describe a technique of a laminated transformer that is a planar transformer (transformer) used in a switching power supply device. In Patent Document 1, in a laminated transformer including a primary winding having a plurality of first conductive coil layers and a secondary winding having a plurality of second conductive coil layers, the plurality of first conductive coils. By devising the connection state of the layers and the plurality of second conductive coil layers, the leakage magnetic flux is reduced and the noise performance is improved. In Patent Document 2, by devising the wiring width and arrangement of the first conductive coil layer and the second conductive coil layer, parasitic capacitance (capacitance) between the first conductive coil layer and the second conductive coil layer is disclosed. To reduce the occurrence of common mode noise. Further, in Patent Document 3, by forming a layer configuration in which a conductive coil layer having a large potential fluctuation between the primary winding and the secondary winding is electromagnetically loosely coupled, Loss is reduced.

JP 2000-173837 A No. 2015-207693 WO / 2017/085785

  In a switching power supply device using a laminated transformer, it is necessary to design the AC resistance (copper loss, which is a resistance loss) of the winding as small as possible in order to reduce the loss generated in the laminated transformer. For this purpose, it is necessary to have a winding structure with good coupling between the primary winding and the secondary winding.

  However, in the laminated transformer in which the winding is configured by a printed circuit board (printed wiring board), since the facing area between the conductive coil layers is large, a very large capacitance is generated between the primary winding and the secondary winding, Loss (capacity loss that is stray load loss) or malfunction due to this capacitance occurs. In particular, the copper loss and the capacity loss are in a trade-off relationship (that is, the capacity loss increases when the copper loss is reduced, and the copper loss increases when the capacity loss is reduced). Even if the techniques of Patent Documents 1 to 3 are applied, it is difficult to optimize the loss of the winding design so as to reduce the capacity loss while suppressing the increase in copper loss.

  The switching power supply of the present invention includes a switching circuit that switches a DC voltage to convert it to a first AC voltage, a resonance circuit that resonates with the converted first AC voltage, and a plurality of first conductive coil layers, A laminated transformer comprising: a primary winding to which an output voltage of the resonance circuit is applied; and a secondary winding having a plurality of second conductive coil layers and outputting a second AC voltage and a second AC current; A rectifier circuit for rectifying the second alternating current.

  Here, in the laminated transformer, the first conductive coil layer and the second conductive coil layer are laminated in a plurality of layers via an insulating layer, and the primary winding and the secondary winding pass through an iron core. Only the wiring width of the first conductive coil layer which is electromagnetically coupled and has a large potential difference between the first conductive coil layer and the second conductive coil layer facing each other, except for the first conductive coil layer having the large potential difference. The wiring width of the first conductive coil layer is narrower.

  According to the switching power supply device of the present invention, in the laminated transformer, only the wiring width of the first conductive coil layer having a large potential difference between the first conductive coil layer and the second conductive coil layer facing each other is the first The wiring width of the first conductive coil layer other than the one conductive coil layer is narrower. Therefore, in the laminated transformer, the capacity loss caused by the current flowing through the interwinding capacitance between the primary winding and the secondary winding, and the copper loss of the primary winding and the secondary winding due to the load current, Since the entire loss of the laminated transformer is minimized, the switching power supply device can be easily and easily made highly efficient.

The top view of the printed wiring board which comprises the laminated transformer of Example 1 of this invention 1 is a schematic equivalent circuit diagram of a switching power supply device 1 having a laminated transformer according to a first embodiment of the present invention. Schematic perspective view showing the external appearance of the laminated transformer 30 in FIG. FIG. 3 is a schematic longitudinal sectional view showing the laminated transformer 30 of FIG. FIG. 4 is an enlarged cross-sectional view showing an example of a laminated structure of the printed circuit board in FIG. Voltage waveform diagram of the capacitance between windings in Fig. 2 1 is a characteristic diagram of load loss generated in the laminated transformer 30 of FIG. 1 is a characteristic diagram of conversion efficiency in the laminated transformer 30 of FIG.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Example 1)
FIG. 2 is a schematic equivalent circuit diagram of the switching power supply device 1 having the laminated transformer according to the first embodiment of the present invention.

  The switching power supply device 1 is, for example, an LLC resonant converter, which is a current resonance type converter, and has a positive electrode side input terminal 2a and a negative electrode side input terminal 2b to which a DC input voltage Vin (for example, 400V) is applied from a solar cell or the like. doing. The input terminal 2b is connected to the ground GND. A switching circuit 10 is connected to the input terminals 2a and 2b.

  The switching circuit 10 includes two switching elements (for example, field effect transistors, hereinafter referred to as “FETs”) 11 and 12, and the FETs 11 and 12 are connected in series between the two input terminals 2a and 2b. It has a half-bridge configuration. The two FETs 11 and 12 have a function of performing on / off operations complementarily by switching drive signals S1 and S2 supplied from a control unit (not shown) to convert the DC input voltage Vin into a first AC voltage. . Between the drains and the sources of the FETs 11 and 12, body diodes 11a and 12a are connected in antiparallel.

  A resonance circuit 20 is connected to a connection point N1 between the input terminal 2a and the drain of the FET 11 and a connection point N2 between the source of the FET 11 and the drain of the FET 12. The resonance circuit 20 is a circuit that resonates with the first AC voltage converted by the switching circuit 10, and includes a resonance capacitor 21, a resonance inductor 22, and an excitation inductor 23 of the multilayer transformer 30. An inductor 22 and an exciting inductor 23 are connected in series between the two connection points N1 and N2. A primary winding 31 of a laminated transformer 30 is connected to the exciting inductor 23 in parallel.

  The laminated transformer 30 converts the output voltage of the resonance circuit 20 into a predetermined voltage, and has one primary winding 31 and two secondary windings 32 and 33, and these primary windings. 31 and secondary windings 32 and 33 are electromagnetically coupled via an iron core 34. A winding start 31a (a black dot in FIG. 2) 31a of the primary winding 31 is connected to a connection point between the resonance capacitor 21 and the exciting inductor 23. A winding end 31b of the primary winding 31 is connected to the resonance inductor 22 and It is connected to the connection point of the exciting inductor 23. The winding end 32b of the secondary winding 32 and the winding start 33a of the secondary winding 33 are connected to each other via a center tap TP. Between the winding start 31 a of the primary winding 31 and the center tap TP between the secondary windings 32 and 33, an interwinding capacitance 35 that is a parasitic capacitance is generated. Similarly, an inter-winding capacitance 36 that is a parasitic capacitance is also generated between the winding end 31 b of the primary winding 31 and the center tap TP between the secondary windings 32 and 33.

  A rectifier circuit 50 is connected to the winding start 32 a of the secondary winding 32 and the winding end 33 b of the secondary winding 33. The rectifier circuit 50 is a circuit that rectifies the second alternating current output from the secondary windings 32 and 33, and has a half-bridge configuration with two rectifier elements (for example, diodes) 51 and 52. The anode of the diode 51 is connected to the winding start 32 a of the secondary winding 32, and the anode of the diode 52 is connected to the winding end 33 b of the secondary winding 33. The cathodes of the two diodes 51 and 52 are connected to each other.

  A smoothing capacitor 53 that smoothes the output voltage of the rectifier circuit 50 is connected between the cathodes of the diodes 51 and 52 and the center tap TP of the secondary windings 32 and 33. A positive output terminal 54a and a negative output terminal 54b for outputting a DC output voltage Vout are connected to both ends of the smoothing capacitor 53. A load 55 is connected between the output terminals 54a and 54b.

  FIG. 3 is a schematic perspective view showing the appearance of the laminated transformer 30 in FIG. 4 is a schematic longitudinal sectional view showing the laminated transformer 30 of FIG. FIG. 5 is an enlarged cross-sectional view showing an example of a laminated structure of the printed board in FIG. FIG. 1 is a plan view of a printed wiring board constituting the laminated transformer according to the first embodiment of the present invention.

  As shown in FIGS. 1, 3, and 4, the laminated transformer 30 includes, for example, an EE type iron core 34 and a plurality of (for example, four layers) first printed circuit boards 37 (1) to 37 (4) (here And the primary winding 31 composed of parentheses (1), (2), (3), and (4) each representing a layer, and the same shall apply hereinafter) and a plurality of (for example, four layers) second prints. A secondary winding 32 constituted by the boards 38 (1) to 38 (4) and a secondary winding constituted by a plurality of (for example, four layers) second printed boards 39 (1) to 39 (4). 33. The plurality of first printed circuit boards 37 (1) to 37 (4) and the plurality of second printed circuit boards 38 (1) to 38 (4), 39 (1) to 39 (4) are supported by an EE type iron core 34. Have been stacked.

  A plurality of first printed circuit boards 37 (1) to 37 (4) constituting the primary winding 31 and a plurality of second printed circuit boards 38 (1) to 38 (4) constituting the secondary winding 32, The plurality of second printed circuit boards 39 (1) to 39 (4) constituting the secondary winding 33 are each provided with only four layers, but the number of layers depends on the capacity of the laminated transformer 30 and the like. Arbitrarily selected.

  The EE type iron core 34 is constituted by two E type iron cores 34a and 34b which are joined to face each other. One E-shaped iron core 34a has three iron core legs 34a1, 34a2, and 34a3. Similarly, the other E-shaped core 34b has three core legs 34b1, 34b2, and 34b3.

  The four-layer first printed circuit boards 37 (1) to 37 (4) constituting the primary winding 31 have the same structure. For example, the first printed circuit boards 37 (1) to 37 (4) of each phase have a first insulating plate 37a having an insulating layer, and core legs 34a2 and 34b2 are inserted in the center of the first insulating plate 37a. An insertion hole is formed for this purpose. On each first insulating plate 37a, a first conductive coil layer 37b wound a plurality of times is formed around the central insertion hole. In the laminated four layers of the first conductive coil layer 37b, the first layer is formed with a winding start 31a, and the fourth layer is formed with a winding end 31b. The winding end of the third layer and the winding start of the fourth layer are connected in series via the through hole 37c.

  The four-layer second printed boards 38 (1) to 38 (4) constituting the secondary winding 32 have the same structure. For example, the second printed circuit boards 38 (1) to 38 (4) of each phase have a second insulating plate 38a having an insulating layer, and core legs 34a2 and 34b2 are inserted in the center of the second insulating plate 38a. An insertion hole is formed for this purpose. On each of the second insulating plates 38a, a second conductive coil layer 38b wound a plurality of times is formed around the central insertion hole. In the laminated second conductive coil layer 38b, a winding start 32a and a winding end 32b are formed, the first winding starts, the second winding starts, the third winding starts, the fourth layer Is connected to the winding start of the secondary winding 32 through the through-hole 38c, the first winding end, the second winding end, the third winding end, and the fourth layer The end of the eye is connected to the center tap TP through the through hole 38d.

  Similarly, the four-layer second printed circuit boards 39 (1) to 39 (4) constituting the secondary winding 33 have the same structure. For example, each phase of the second printed circuit board 39 (1) to 39 (4) has a second insulating plate 39a having an insulating layer, and core legs 34a2 and 34b2 are inserted in the center of the second insulating plate 39a. An insertion hole is formed for this purpose. On each second insulating plate 39a, a second conductive coil layer 39b wound a plurality of times is formed around the central insertion hole. In the laminated second conductive coil layer 39b, a winding start 33a and a winding end 33b are formed, the first winding starts, the second winding starts, the third winding starts, the fourth layer The first winding end is connected to the center tap TP via the through hole 38d, and the first layer winding end, the second layer winding end, the third layer winding end, and the fourth layer winding end are The secondary winding 33 is connected to the end of winding through the through hole 39c.

  As shown in FIG. 5, the plurality of first printed circuit boards 37 (1) to 37 (4) and the plurality of second printed circuit boards 38 (1) to 38 (4), 39 (1) to 39 (4) And laminated with an insulating adhesive or the like.

  As an example of the vertical laminated structure, in the first printed circuit boards 37 (1) to 37 (4), the first printed circuit board 37 (1) is the second layer, the first printed circuit board 37 (2) is the fifth layer, The first printed circuit board 37 (3) is disposed on the eighth layer, and the first printed circuit board 37 (4) is disposed on the eleventh layer, and is connected in series via the through hole 37c. Among the second printed boards 38 (1) to 38 (4), the second printed board 38 (1) is the first layer, the second printed board 38 (2) is the fourth layer, and the second printed board 38 (3) is The seventh layer and the second printed circuit board (4) are arranged in the tenth layer and are connected in parallel through the through hole 38c and the through hole 38d. Further, in the second printed circuit boards 39 (1) to 39 (4), the second printed circuit board 39 (1) is the third layer, the second printed circuit board 39 (2) is the sixth layer, and the second printed circuit board 39 (3 ) Is arranged in the ninth layer and the second printed circuit board 39 (4) is arranged in the twelfth layer, and is connected in parallel through the through hole 39c and the through hole 38d. The second printed circuit boards 38 (1) to 38 (4) connected in parallel and the second printed circuit boards 39 (1) to 39 (4) connected in parallel are connected in series.

  As shown in FIG. 1, the feature of the first embodiment is that only the wiring width of the first conductive coil layer 37b having a large potential difference between the first conductive coil layer 37b and the second conductive coil layers 38b and 39b facing each other is the potential difference. Is narrower than the wiring width of the first conductive coil layer 37b other than the large first conductive coil layer 37b. For example, the first conductive coil layer 37b having a large potential difference is the layer at the beginning of winding 31a, that is, the first printed circuit board (1).

(Operation of Example 1)
Overall operation (I) of the switching power supply device 1 according to the first embodiment, circulating current (II) flowing through the interwinding capacitors 35, 36, loss (III) of the laminated transformer 30 and efficiency (IV) of the laminated transformer 30 Will be described below.

(I) Overall Operation of Switching Power Supply Device 1 In the switching power supply 1 of FIG. 2, two FETs 11 and 12 in the switching circuit 10 are turned on / off by two switching drive signals S1 and S2 supplied from a control unit (not shown). Operates off. The two FETs 11 and 12 are turned on and off in a complementary manner, and when the two FETs 11 and 12 are switched on / off so that the two FETs 11 and 12 are simultaneously turned on and no through current flows. There is a short dead time in which the FETs 1 and 12 are simultaneously turned off. Within the dead time period, the two FETs 11 and 12 perform soft switching (that is, zero voltage switching (ZVS) or zero current switching (ZIS)) to reduce switching loss and noise generation, thereby achieving high efficiency. It has been.

  For example, when the FET 11 is turned off and the FET 12 is turned on, the DC input voltage Vin applied to the input terminal 2a is inputted to the resonance circuit 20 through the connection point N1, and the inputted current is changed to the resonance capacitor. 21 and the exciting inductor 23 and the path of the resonant capacitor 21 and the primary winding 31 of the multilayer transformer 30. After the two divided currents are merged, a resonance current flows through the path of the resonance inductor 22 and the connection point N2. The resonance current at the connection point N2 flows to the input terminal 2b through the FET 12 in the on state.

  A primary voltage v <b> 1 is generated between both end electrodes of the primary winding 31 by the primary current i <b> 1 flowing through the primary winding 31 of the laminated transformer 30. Then, a secondary current i2 (= primary current i1 × (number of primary windings n1 / 2 number of secondary windings n2)) is induced in the secondary winding 33 of the laminated transformer 30, and the secondary winding 33 A secondary voltage v2 (= primary voltage v1 × (number of secondary windings n2 / number of primary windings n1)) is generated between the electrodes at both ends. The secondary current i2 flowing through the secondary winding 33 is rectified by the diode 52 in the rectifier circuit 50 and further smoothed by the smoothing capacitor 53, and then the DC output voltage Vout is output from the output terminals 54a and 54b, and the load 55.

  Next, when the FET 11 is turned on and the FET 12 is turned off, the electric charge accumulated in the resonant capacitor 21 in the resonance circuit 20 passes through the path of the connection point N1, the on-state FET 11, the connection point N2, and the resonance inductor 22. Flowing. This resonance current is shunted to the exciting inductor 23 and to the primary winding 31 of the multilayer transformer 30. The two divided currents are merged and then flow to the resonant capacitor 21.

  A primary voltage v <b> 1 is generated between both end electrodes of the primary winding 31 by the primary current i <b> 1 flowing through the primary winding 31 of the laminated transformer 30. Then, a secondary current i2 (= primary current i1 × (number of primary windings n1 / 2 number of secondary windings n2)) is induced in the secondary winding 32 of the laminated transformer 30. A secondary voltage v2 (= primary voltage v1 × (number of secondary windings n2 / number of primary windings n1)) is generated between the electrodes at both ends. The secondary current i2 flowing in the secondary winding 32 is rectified by the diode 51 in the rectifier circuit 50 and further smoothed by the smoothing capacitor 53, and then the DC output voltage Vout is output from the output terminals 54a and 54b, and the load 55.

  When controlling the output voltage Vout, a control unit (not shown) detects a change in the output voltage Vout. When the output voltage Vout becomes higher than the target value, the frequency of the switching drive signals S1 and S2 is increased, and the output voltage Vout is set. Lower. Further, when the detected output voltage Vout becomes lower than the target value, the control unit (not shown) decreases the frequency of the switching drive signals S1 and S2 and increases the output voltage Vout. Thus, constant voltage control is performed in which fluctuations in the output voltage Vout are suppressed and maintained at the target value.

(II) Circulating current flowing through interwinding capacitances 35 and 36 In the switching power supply 1 of FIG. 2, when the FET 11 is in an off state and the FET 12 is in an on state, for example, the winding end 31b of the primary winding 31 → the winding Inter-capacitance 36 → center tap TP between secondary windings 32, 33 → secondary winding 33 → diode 52 → smoothing capacitor 53 → center tap TP between secondary windings 32 and 33 → inter-winding capacitance 35 → 1 The circulating current ic flows through the path of the winding start 31a of the next winding 31. Therefore, when the voltage per unit time is dv / dt, a large voltage of dv / dt is applied to the location of the interwinding capacitance 36.

  In FIG. 6, the interwinding capacitances 35 and 36 in FIG. FIG. In FIG. 6, the horizontal axis represents time (t), and the vertical axis represents voltage (V).

  When the voltage waveforms V35 and V36 applied between the primary winding 31 and the secondary windings 32 and 33 of the laminated transformer 30 were measured using the oscilloscope, as shown in FIG. It was found that a large voltage Vh of / dt was applied. Oscillating current is generated by this voltage Vh. The generation of such an oscillating current causes a malfunction or malfunction due to loss, common mode noise, or the like.

(III) Loss of Multilayer Transformer 30 Losses of the multilayer transformer 30 can be broadly divided into a no-load loss that occurs regardless of the load and a load loss that changes depending on the load current. The no-load loss is mainly an iron loss Li generated in the iron core 34 that is a path of magnetic flux, but in addition, the resistance loss of the primary winding 31 and the secondary windings 32 and 33 due to the exciting current and the insulation Dielectric loss is included. The load loss mainly includes a copper loss Lr that is a resistance loss of the primary winding 31 and the secondary windings 32 and 33 due to a load current, and a capacitance loss Lc that is generated by a current flowing through the interwinding capacitances 35 and 36. In addition, stray loads due to eddy currents are also included. Since the loss other than the copper loss Lr and the capacity loss Lc is small in the load loss, it is desirable that the total loss Lt of the load loss in the multilayer transformer 30 is represented by the copper loss Lr and the capacity loss Lc.

  FIG. 7 is a diagram showing characteristics of load loss generated in the laminated transformer 30 of FIG. 1, where the horizontal axis represents the wiring width of the primary winding 31 and the vertical axis represents the magnitude of the load loss.

  In order to reduce the loss generated in the laminated transformer 30, it is necessary to design the copper loss Lr that is the AC resistance of the primary winding 31 and the secondary winding 32 as small as possible. For this purpose, it is necessary to have a winding structure with good coupling between the primary winding 31 and the secondary winding 32. However, in the laminated transformer 30 in which the primary winding 31 and the secondary winding 32 are configured by printed circuit boards 37 (1) to 37 (4) and 38 (1) to 38 (4), the conduction of the primary winding 31. Since the facing area between the coil layer 37b and the conductive coil layers 38b and 39b of the secondary windings 32 and 33 is large, a winding having a very large capacitance between the primary winding 31 and the secondary windings 32 and 33. Capacitances 35 and 36 between the lines are generated, and a malfunction due to capacitance loss Lc and noise due to the interwinding capacitances 35 and 36 occurs. Since the copper loss Lr, which is a load loss, and the capacitance loss Lc are in a trade-off relationship, a design of the winding design is required to reduce the capacitance loss Lc while suppressing an increase in the copper loss Lr.

  Thus, in the first embodiment, the wiring loss of a part of the conductive coil of the primary winding 31 is reduced to reduce the capacity loss Lc, and the optimum point at which the total loss Lt of the copper loss Lr and the capacity loss Lc is minimized. I thought about the design method. Although various conditions can be considered for narrowing the wiring width, the following three (a), (b), and (c) were considered.

(A) The wiring width of the primary winding 31 is all wide.
(B) A part of the primary winding 31 is narrow (for example, as shown in FIG. 1, only the wiring width of the first printed circuit board 37 (1) at the beginning of winding 31a is narrow).
(C) The wiring width of the primary winding 31 is all narrow (for example, the entire wiring width of the primary winding 31 is 1/2 of the wiring width of (a)).

  In the case of these three (a), (b), and (c), the loss generated in the primary winding 31 and the secondary windings 32 and 33 theoretically has a relationship as shown in FIG. Conceivable.

  In FIG. 7, as the wiring width of the primary winding 31 is reduced, the copper loss Lr increases while the capacitance loss Lc decreases. Although the copper loss Lr and the capacity loss Lc are in a trade-off relationship, it is considered that the total loss Lt of these totals tends to have the optimum point (b) as shown in the theoretical diagram of FIG.

  In the first embodiment, only the wiring width of the winding start 31a in the primary winding 31 in which the potential difference between the primary winding 31 and the secondary windings 32 and 33 is large is narrowed. At this time, by adjusting the amount to be narrowed, the balance (equilibrium) of the capacity loss Lc and the copper loss Lr is determined, and the condition that becomes the optimum point of the total loss Lt is set.

(IV) Efficiency of Multilayer Transformer FIG. 8 is a characteristic diagram of conversion efficiency in the multilayer transformer 30 of FIG. 1, where the horizontal axis represents input voltage (V) and the vertical axis represents power conversion efficiency (%).

  As shown in FIGS. 1 and 5, when the wiring width of the primary winding 31 is uniformly reduced to, for example, 1.25 mm, 0.83 mm, and 0.625 mm, the wiring width becomes 1.25 mm → Conversion efficiency increased at 0.625 mm. It is expected that the effect of common mode noise and the like due to the interwinding capacitances 35 and 36 is greatly reduced, leading to an increase in efficiency. In the first embodiment, since only the wiring width of the winding start 31a in the primary winding 31 is narrowed, the total loss can be optimized compared with the characteristics of the wiring width of 0.625 mm, and the efficiency further increases. .

(Effect of Example 1)
According to the switching power supply device 1 of the first embodiment, in the laminated transformer 30, the first printed circuit board 37 (1) has a large potential difference between the first conductive coil layer 37b and the second conductive coil layers 38b and 39b facing each other. Only the wiring width of the first conductive coil layer 37b is narrower than the wiring width of the first conductive coil layer 37b in the first printed boards 37 (2) to 37 (4). Therefore, in the laminated transformer 30, a laminated transformer having a capacitance loss Lc caused by a current flowing through the interwinding capacitances 35 and 36 and a copper loss Lr of the primary winding 31 and the secondary winding 32 due to a load current. Since the total loss Lt of 30 is minimized, the switching power supply device 1 can be made highly efficient simply and easily.

(Modification of Example 1)
The present invention is not limited to the first embodiment, and various usage forms and modifications are possible. For example, the following forms (A) to (D) are available as usage forms and modifications.

(A) The laminated transformer 30 is not limited to the configuration shown in FIGS. In the first embodiment, the two secondary windings 32 and 33 are connected in parallel, but the present invention is applicable to a laminated transformer having a configuration in which the two secondary windings 32 and 33 are connected in series. Can be applied.
(B) The laminated transformer 30 is not limited to the structure shown in FIGS. 3 and 4. Although the EE type iron core is used in the iron core 34 of the first embodiment, iron cores having other shapes such as an EI type, an EF type, an EER type, and an ETD type may be used. Also, the laminated structure of the first printed circuit boards 37 (1) to 37 (4) and the second printed circuit boards 38 (1) to 38 (4), 39 (1) to 39 (4) in the laminated transformer 30 of FIG. However, the present invention is not limited to this. The number of layers of the printed boards 37 (1) to 37 (4), 38 (1) to 38 (4), 39 (1) to 39 (4) and the arrangement of the layers are changed to a number and arrangement other than those shown in the figure. May be.

(C) In the first embodiment, the primary winding 31 and the secondary windings 32 and 33 are printed boards 37 (1) to 37 (4), 38 (1) to 38 (4), 39 (1) to 39. Although it comprised by (4), it is not limited to this. For example, instead of the conductive coil layers 37b, 38b, 39b formed on the printed circuit boards 37 (1) -37 (4), 38 (1) -38 (4), 39 (1) -39 (4), A plurality of conductive coil layers each constituted by a wire are laminated with a predetermined interval between them, and an insulating member as an insulating layer is inserted or filled between each conductive coil layer, and the primary winding 31 and the secondary winding 32 and 33 may be formed.
(D) The switching power supply device 1 using the laminated transformer 30 of the first embodiment is not limited to the LLC resonant converter of FIG. The LLC resonant converter of FIG. 2 may be changed to another circuit configuration. Further, the laminated transformer 30 of the first embodiment can be applied to other switching power supply devices other than the LLC resonant converter.

DESCRIPTION OF SYMBOLS 1 Switching power supply device 10 Switching circuit 20 Resonant circuit 30 Laminated transformer 31 Primary winding 32,33 Secondary winding 34 Iron core 35,36 Capacitance between windings 37 (1) -37 (4) 1st printed circuit board 37a 1st Insulating plate 37b First conductive coil layer 37c, 38c, 38d, 39c Through hole 38 (1) -38 (4), 39 (1) -39 (4) Second printed circuit board 38a, 39a Second insulating plate 38b, 39b Second conductive coil layer 50 Rectifier circuit

Claims (3)

A switching circuit for switching a DC voltage to convert it to a first AC voltage;
A resonant circuit that resonates with the converted first AC voltage;
A primary winding having a plurality of first conductive coil layers, to which an output voltage of the resonance circuit is applied, and a plurality of second conductive coil layers, and outputting a second AC voltage and a second AC current 2 A laminated transformer comprising a next winding;
A rectifier circuit for rectifying the second alternating current;
In a switching power supply device comprising:
The laminated transformer is
A plurality of layers of the first conductive coil layer and the second conductive coil layer are laminated via an insulating layer, and the primary winding and the secondary winding are electromagnetically coupled via an iron core,
The first conductive coil layer other than the first conductive coil layer having a large potential difference is only the wiring width of the first conductive coil layer having a large potential difference between the first conductive coil layer and the second conductive coil layer facing each other. It is narrower than the wiring width of
The switching power supply device characterized by the above-mentioned. The first conductive coil layer having a large potential difference is an initial winding layer.
The switching power supply device according to claim 1. The primary winding is
A first insulating plate having the insulating layer;
The first conductive coil layer formed on the first insulating plate;
A plurality of first printed circuit boards each comprising:
The plurality of first printed circuit boards are connected in series via through holes formed in the first insulating plates,
The secondary winding is
A second insulating plate having the insulating layer;
The second conductive coil layer formed on the second insulating plate;
A plurality of second printed circuit boards each comprising:
The plurality of second printed circuit boards are connected in series or in parallel through through holes formed in the second insulating plates.
The switching power supply device according to claim 1 or 2,

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