JP6478434B2 - Switching power supply - Google Patents

Description

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

  Conventionally, for example, Patent Document 1 describes a technique of a laminated transformer. The laminated transformer is formed by laminating a plurality of printed wiring boards on which primary windings made of coiled conductor patterns are formed and printed wiring boards on which secondary windings made of coiled conductor patterns are formed, An iron core is inserted through the plurality of printed wiring boards. The primary winding and the secondary winding are electromagnetically coupled through the iron core, and a magnetic flux in a predetermined direction is formed in the iron core by the primary voltage applied to the primary winding. A secondary voltage is induced. In general transformers, a primary winding and a secondary winding are wound around a coil bobbin, and an iron core is inserted through the coil bobbin. In contrast to such a general transformer, the interval between the primary winding and the secondary winding is narrow in the laminated transformer, so that the electromagnetic coupling becomes dense and the value of the leakage inductance becomes small.

  Therefore, for example, when a laminated transformer is used for an LLC resonant converter, it becomes difficult to realize soft switching of the switching element (that is, switching in a zero current state or a zero voltage state), increasing a switching loss, and power conversion. Efficiency is reduced. Furthermore, since the value of the leakage inductance is small in the multilayer transformer, a new choke coil (reactor) must be added to compensate for this, and the LLC resonant converter becomes larger due to an increase in the number of parts.

  In order to solve such inconvenience, in the laminated transformer of Patent Document 1, a device for increasing the value of the leakage inductance by increasing the leakage magnetic flux by increasing the interval between the primary winding and the secondary winding. I am doing.

JP 2009-289879 A

  Since the conventional laminated transformer can be tightly coupled between the primary winding and the secondary winding, there is an advantage that the AC resistance can be suppressed low. However, when the conventional multilayer transformer is used in an LLC resonant converter that does not have a choke coil on the secondary side such as an LLC resonant circuit, the current flowing through the capacitance between the primary winding and the secondary winding of the multilayer transformer As a result, a large loss (hereinafter referred to as “capacity loss”) occurs. This capacity loss becomes prominent especially when the turn ratio of the primary winding and the secondary winding of the laminated transformer is large, and there is a problem that the high efficiency is hindered. No. 1 does not disclose anything, nor suggests a solution.

  The switching power supply device of the present invention includes a switching circuit that switches a DC voltage to convert it to an AC voltage, a resonance circuit that resonates with an output voltage of the switching circuit, a laminated transformer that is provided with an output voltage of the resonance circuit, And a rectifier circuit that rectifies the AC voltage output from the laminated transformer.

The laminated transformer includes a plurality of first conductive coil layers, a primary winding to which an output voltage of the resonance circuit is applied, and a plurality of second conductive coil layers, and outputs the AC voltage. A secondary winding, wherein the plurality of first conductive coil layers and the plurality of second conductive coil layers are laminated via an insulating layer, and the primary winding and the secondary winding are: The first conductive coil layer and the second conductive layer that are electromagnetically coupled through an iron core and have a large potential fluctuation due to a circulating current flowing through the interwinding capacitance between the primary winding and the secondary winding . between the conductive coil layer, characterized in that it has a layer structure such that electromagnetic loosely coupled.

  According to the switching power supply device of the present invention, in the laminated transformer, the capacitance loss caused by the current flowing through the capacitance between the primary winding and the secondary winding, and the resistance of the primary winding and the secondary winding due to the load current. Since the total loss of the laminated transformer having the copper loss, which is a loss, is minimized, the switching power supply device can be easily and easily made highly efficient.

FIG. 1 is a circuit diagram showing a switching power supply device 1 in Embodiment 1 of the present invention. FIG. 2A is a diagram showing a symbol of the laminated transformer 30 in FIG. 2B is a schematic longitudinal sectional view showing the laminated transformer 30 of FIG. 2A. FIG. 2C is a schematic perspective view showing an appearance of the first printed wiring board 31.1 in FIG. 2B. 2D is a schematic perspective view showing an appearance of the second printed wiring board 32.1 in FIG. 2B. FIG. 2D is a schematic perspective view showing the appearance of the second printed wiring board 33.1 in FIG. 2B. FIG. 3A is a cross-sectional view showing a layer configuration example of a tightly coupled DCS. FIG. 3B is a cross-sectional view showing a layer configuration example of loosely coupled SCS from one side. FIG. 3C is a cross-sectional view showing a layer configuration example of loosely coupled SCS from one side. FIG. 3D is a cross-sectional view showing a configuration example of the loosely coupled SCS from the outside. FIG. 4 is a waveform diagram showing the circulating current ic2 and the reverse circulating current -ic2 in FIG. FIG. 5A is an equivalent circuit diagram of the switching power supply device 1 when the resonant circuit 20 is connected to the FET 11. FIG. 5B is a diagram showing the voltage waveforms Vct1 and Vct2 in FIG. 5A. FIG. 6A is a diagram illustrating a loss with respect to the layer configuration of the laminated transformer 30. FIG. 6B is a diagram showing experimental results of loss with respect to the thickness of the insulating plates 31c, 32c, and 33c. FIG. 6C is a diagram showing experimental results of loss with respect to the relative dielectric constant εr of the insulating plates 31c, 32c, and 33c. FIG. 7A is an equivalent circuit diagram showing a switching power supply apparatus 1A according to the second embodiment of the present invention. FIG. 7B is a diagram showing the voltage waveforms Vct1 and Vct2 in FIG. 7A. FIG. 8A is an equivalent circuit diagram showing the switching power supply device 1B according to the third embodiment of the present invention. FIG. 8B is a diagram showing the voltage waveforms Vct1 and Vct2 in FIG. 8A.

  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. 1 is a schematic circuit diagram showing a switching power supply device 1 having a laminated transformer in Embodiment 1 of the present invention.

  The switching power supply device 1 is, for example, an LLC resonant converter that is a current resonant converter, and includes a positive side input terminal 2a and a negative side input terminal 2b. A DC power source 3 such as a solar cell and an internal resistor 4 are connected in series between the positive input terminal 2a and the negative input terminal 2b, and a DC input voltage Vin is connected between the input terminals 2a and 2b. (For example, 400V) is input. The input terminal 2b is connected to the ground GND through the resistor 5. A switching circuit 10 is connected to the input terminals 2a and 2b via a smoothing input capacitor 6.

  The switching circuit 10 includes two switching elements (for example, field effect transistors, hereinafter referred to as “field effect transistors”) between a connection point N1 connected to the positive input terminal 2a and a connection point N2 connected to the negative input terminal 2b. FET ”) 11 and 12 are in a half-bridge configuration connected in series. The two FETs 11 and 12 have a function of performing on / off operations complementarily by the switching signals S1 and S2 and converting the DC input voltage Vin into an AC voltage. Between the source and drain of the FET 11, a body diode 11a is connected in antiparallel, and a series circuit of a parasitic resistance 11b and a parasitic capacitance 11c is connected in parallel. Similarly, a body diode 12a is connected in antiparallel between the source and drain of the FET 12, and a series circuit of a parasitic resistor 12b and a parasitic capacitor 12c is connected in parallel.

  A resonance circuit 20 is connected to a connection point N1 on the input terminal 2a side and a connection point N3 of the two FETs 11 and 12. The resonance circuit 20 includes a resonance capacitor 21, a resonance inductor 22, an excitation inductor 23 of the multilayer transformer 30, and a resistor 24 inside the multilayer transformer 30, and these resonance capacitor 21, resonance inductor 22, excitation inductor 23, and resistor 24 is connected in series between the connection point N1 and the connection point N3.

  A connection point N4 between the resonance capacitor 21 and the exciting inductor 23 and a connection point N5 between the resonance inductor 22 and the resistor 24 include the leakage inductor 25, the primary winding 31 of the multilayer transformer 30, and the primary winding 31. An internal resistor 26 is connected in series.

  The laminated transformer 30 has one primary winding 31 and two secondary windings 32, 33, and these primary winding 31 and secondary windings 32, 33 are connected via an iron core 34. Are electromagnetically coupled. On the winding start side of the secondary winding 32, a resistor 41, a leakage inductor 42, and a connection point N6 inside the secondary winding 32 are connected in series. On the winding end side of the secondary winding 33, a resistor 43, a leakage inductor 44, and a connection point N7 inside the secondary winding 33 are connected in series. Further, a connection point N8 is connected to the center tap TP between the two secondary windings 32 and 33 via an internal resistor 45 on the center tap TP side.

  The leakage inductor 25 on the primary winding 31 side is obtained by converting the leakage inductors of the secondary windings 32 and 33 to the primary side. The leakage inductors 42 and 44 on the secondary windings 32 and 33 side are obtained by converting the leakage inductor of the primary winding 31 to the secondary side. The leakage inductor 25 on the winding start side of the primary winding 31 causes a loss in a normal forward converter or the like. However, in the current resonance type converter as in the first embodiment, since the leakage inductor 25 becomes a resonance element in series with the resonance inductor 22, it does not cause a loss. The resonant inductor 22 on the primary winding 31 side may be constituted by a leakage inductor of the primary winding 31.

  Between the primary-side connection point N4 of the multilayer transformer 30 and the secondary-side connection point N6 of the multilayer transformer 30, there are a resistance 46 inside the multilayer transformer 30 and primary windings 31 and 2 that are parasitic capacitances. The interwinding capacitance 47 of the next winding 32 is connected in series. Similarly, between the primary-side connection point N5 of the multilayer transformer 30 and the secondary-side connection point N7 of the multilayer transformer 30, there are a resistor 48 inside the multilayer transformer 30 and a primary winding that is a parasitic capacitance. 31 and the interwinding capacitance 49 of the secondary winding 33 are connected in series.

  A rectifier circuit 50 is connected to the connection points N6 and N7. The rectifier circuit 50 is a circuit for half-wave rectifying the AC voltage at the connection points N6 and N7, and is composed of two rectifier elements (for example, FETs) 51 and 52. The two FETs 51 and 52 are elements that allow a current to flow in the forward direction when turned on by the switching signals S3 and S4, respectively. Between the source and drain of the FET 51, a body diode 51a is connected in antiparallel, and a series circuit of a parasitic resistor 51b and a parasitic capacitor 51c is connected in parallel. Similarly, a body diode 52a is connected in antiparallel between the source and drain of the FET 52, and a series circuit of a parasitic resistance 52b and a parasitic capacitance 52c is connected in parallel.

  The use of the FETs 51 and 52 as the rectifying elements has an advantage that current can be cut off when unnecessary. Instead of the two FETs 51 and 52, two diodes may be provided.

  Between a connection point N9 on the output side of the FETs 51 and 52 and a connection point N8 on the center tap TP side, a positive output terminal 55a and a negative side are connected via a series circuit of a smoothing output capacitor 53 and a resistor 54. An output terminal 55b is connected. The DC output voltage Vout output from the output terminals 55 a and 55 b is supplied to the load circuit 60.

  The load circuit 60 has a load resistor 61 connected between the output terminals 55a and 55b. The output terminal 55b is connected to the ground GND through the resistor 62 and the capacitor 63.

Incidentally, one-dot chain line arrow in FIG. 1 is a path of the circulating current ic1 flowing through the winding capacitance 47 and 49. A thick solid line arrow is a path of the circulating current ic2 corresponding to the circulating current ic1.

  FIG. 2A is a diagram showing a symbol of the laminated transformer 30 in FIG. 2B is a schematic longitudinal sectional view showing the laminated transformer 30 of FIG. 2A. FIG. 2C is a schematic perspective view showing an appearance of the first printed wiring board 31.1 in FIG. 2B. FIG. 2D is a schematic perspective view showing an appearance of the second printed wiring board 32.1 in FIG. 2B. Further, FIG. 2E is a schematic perspective view showing the appearance of the second printed wiring board 33.1 in FIG. 2B.

  The primary winding 31 of the laminated transformer 30 has a winding start 31a and a winding end 31b. Of the two secondary windings 32 and 33, the secondary winding 32 has a winding start 32a and a winding end 32b, and the secondary winding 33 also has a winding start 33a and a winding end 33b. Yes. 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 one primary winding 31 and two secondary windings 32 and 33 of the multilayer transformer 30, interwinding capacitances 47 and 49, which are parasitic capacitances, are connected, respectively. The laminated transformer 30 includes, for example, an EI type iron core 34, a single primary winding 31 composed of a plurality of (for example, eight layers) first printed wiring boards 31.1-31.8, and a plurality of (for example, 16 layers) of the second printed wiring boards 32.1-32.8, 33.1-33.8, and two secondary windings 32, 33, and a plurality of the first windings. A printed wiring board 31.1-31.8 and a plurality of second printed wiring boards 32.1-32.8, 33.1-33.8 are supported and stacked on an EI iron core 34.

  A plurality of first printed wiring boards 31.1-31.8 constituting the primary winding 31 and a plurality of second printed board wirings 32.1-32.8 constituting the secondary winding 32, and 2 Each of the plurality of second printed wiring boards 33.1 to 33.8 constituting the next winding 33 is provided with only eight layers, but the number of layers is arbitrarily selected according to the capacity of the laminated transformer 30 and the like. Is done.

  The EI type iron core 34 has an E type iron core 34a having three iron core legs 34a1, 34a2, and 34a3, and an I type iron core 34b. An I-shaped iron core 34b is fixed to the tops of the three iron core legs 34a1, 34a2, and 34a3.

  The plurality of first printed wiring boards 31.1-31.8 constituting the primary winding 31 have the same structure. For example, the first printed wiring board 31.1 includes a first insulating plate 31c having an insulating layer, and an iron core leg insertion hole 31d for inserting the iron core leg 34a2 is formed at the center of the first insulating plate 31c. ing. On the first insulating plate 31c, a first conductive coil layer 31e wound once is formed around the central core leg insertion hole 31d. The first conductive coil layer 31e may be wound twice or the like. The eight first conductive coil layers 31e that are stacked are connected in series via through holes formed on the winding start 31a side and the winding end 31b side.

  The plurality of second printed wiring boards 32.1-32.8 constituting the secondary winding 32 have the same structure. For example, the second printed wiring board 32.1 includes a second insulating plate 32c having an insulating layer, and an iron core leg insertion hole 32d for inserting the iron core leg 34a2 is formed in the center of the second insulating plate 32c. ing. On the second insulating plate 32c, a second conductive coil layer 32e wound once is formed around the central core leg insertion hole 32d. The second conductive coil layer 32e may be wound twice.

  Similarly, the plurality of second printed wiring boards 33.1 to 33.8 constituting the secondary winding 33 have the same structure. For example, the second printed wiring board 33.1 includes a second insulating plate 33c having an insulating layer, and a core leg insertion hole 33d for inserting the core leg 34a2 is formed at the center of the second insulating plate 33c. ing. On the second insulating plate 33c, a second conductive coil layer 33e wound once is formed around the central core leg insertion hole 33d. The second conductive coil layer 33e may be wound twice.

  The two second conductive coil layers 32e and 33e are connected in parallel through through-holes formed on the winding start 32a and 33a side and the winding end 32b and 33b side to form a set of two layers. The two sets of the two layers of the second conductive coil layers 32e and 33e that are stacked are connected in series via a through hole.

  Hereinafter, when a plurality of second printed wiring boards 32.1-32.8, 33.1-33.8 in a set are schematically represented, reference numerals “32, 33.1-32, 33.8” are used. ".

  The plurality of first printed wiring boards 31.1-31.8 and the plurality of second printed wiring boards 32, 33.1-32, 33.8 are bonded and laminated with an insulating adhesive or the like. .

  3A, 3B, 3C, and 3D show the first printed wiring board 31.1-31.8 and the second printed wiring board 32, 33.1-32, and 33.8 in FIGS. 2B to 2E. It is sectional drawing which shows the layer structural example. 3A is a layer configuration example of a tightly coupled DCS, FIGS. 3B and 3C are layer configuration examples of a loosely coupled SCS from one side, and FIG. 3D is a layer configuration example of a loosely coupled SCS from the outside.

  In the layer configuration example of FIG. 3A, the first printed wiring board 31.1-31.8 and the second printed wiring board 32 / 33.1 are vertically arranged between the I-shaped iron core 34b and the E-shaped iron core 34a. 32, 33.8 are alternately arranged, and the electromagnetic coupling between the first printed wiring board 31.1-31.8 and the second printed wiring board 32, 33.1-32, 33.8 It is in a tightly coupled DCS state.

  In the layer configuration example of FIG. 3B, between the I-shaped iron core 34b and the E-shaped iron core 34a, three first printed wiring boards 31.6-31.8 and three second printed wiring boards from one side near the E-shaped iron core 34a. The printed wiring boards 32, 33.6-32, and 33.8 are in a loosely coupled SCS state. The other five first printed wiring boards 31.1-31.5 and the five second printed wiring boards 32, 33.1-32, 33.5 are in a tightly coupled DCS state.

  In the layer configuration example of FIG. 3C, three first printed wiring boards 31.1-31.3 and three second ones are formed between the I-shaped core 34b and the E-shaped core 34a from one side near the I-shaped core 34b. The printed wiring boards 32, 33.1-32, and 33.3 are in a loosely coupled SCS state. The other five first printed wiring boards 31.4-31.8 and the five second printed wiring boards 32, 33.4-32, 33.8 are in a tightly coupled DCS state.

  In the layer configuration example of FIG. 3D, three printed wiring boards 31.1-31.3 and three second printed wiring boards 32 and 33 are located outside from the vicinity of the center between the I-shaped iron core 34b and the E-shaped iron core 34a. The electromagnetic coupling with 1-32 / 33.3 is in a loosely coupled SCS state, and three printed wiring boards 31.6-31.8 and three second printed wiring boards 32. 33.6-32 and 33.8 are in a loosely coupled SCS state. The two first printed wiring boards 31.4 and 31.5 near the center and the two second printed wiring boards 32 · 33.4, 32 · 33.5 are in a tightly coupled DCS state.

  In the switching power supply device 1 of FIG. 1 of the first embodiment, the laminated transformer 30 having the layer configuration of FIG. 3B is employed.

(Operation of Example 1)
Overall operation (I) of the switching power supply device 1 according to the first embodiment, a primary side circuit configuration example (II) in the multilayer transformer 30, determination of an optimum layer configuration in the multilayer transformer 30 (III), and loose coupling The SCS formation example (IV) will be described below.

(I) Overall Operation of Switching Power Supply Device 1 In FIGS. 1 and 2A-2E, two FETs 11 and 12 in the switching circuit 10 are rectified by four switching signals S1-S4 output from a control circuit (not shown). The two FETs 51 and 52 in the circuit 50 are turned on / off. The two FETs 11 and 12 in the switching circuit 10 are turned on and off in a complementary manner, and the two FETs 11 and 12 are turned on / off so that the two FETs 11 and 12 are turned on simultaneously and no through current flows. At the time of switching, a short dead time is provided in which the two FETs 11 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 (ZCS)) to reduce switching loss and noise generation, thereby achieving high efficiency. It has been.

  The FET 51 in the rectifier circuit 50 is turned on / off in synchronization with the FET 11 in the switching circuit 10, and the FET 52 in the rectifier circuit 50 is also turned on / off in synchronization with the FET 12 in the switching circuit 10. It has become.

  For example, when the FETs 11 and 51 are turned off and the FETs 12 and 52 are turned on, the DC input voltage Vin supplied from the DC power supply 3 to the input terminal 2 a via the resistor 4 is smoothed by the input capacitor 6. The smoothed power supply current is input to the resonance circuit 20 through the connection point N1, and is shunted to the connection point N5 through the path of the resonance capacitor 21, the connection point N4, the exciting inductor 23, and the resistor 24, and the leakage inductor 25. Then, the current is shunted to the connection point N5 through the path of the primary winding 31 of the laminated transformer 30 and the resistor 26. The two divided currents are merged at the connection point N5, and then a resonance current flows through the path of the resonance inductor 22 and the connection point N3. The resonance current at the connection point N3 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 secondary windings n2 / number of primary windings n1)) 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 FET 52 in the rectifier circuit 50 through the resistor 45, the leakage inductor 44, and the resistor 43, and further smoothed by the output capacitor 53 and the resistor 54. A DC output voltage Vout is output from the output terminals 55 a and 55 b and supplied to the load circuit 60.

  Next, when the FETs 11 and 51 are turned on and the FETs 12 and 52 are turned off, the charges accumulated in the resonance capacitor 21 in the resonance circuit 20 are connected to the connection point N1, the FET 11 in the on state, the connection point N3, and the resonance inductor 22. , And the path of the connection point N5. This resonance current is shunted to the resistor 24 and the exciting inductor 23, and is shunted to the resistor 26, the primary winding 31 of the multilayer transformer 30, and the leakage inductor 25. The two divided currents are merged at the connection point N4 and then flow to the resonance 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 secondary windings n2 / number of primary windings n1)) is induced in the secondary winding 32 of the laminated transformer 30, and the secondary winding 32 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 32 is rectified by the FET 51 in the rectifier circuit 50 through the resistor 45, the leakage inductor 42, and the resistor 41, and further smoothed by the output capacitor 53 and the resistor 54. A DC output voltage Vout is output from the output terminals 55 a and 55 b and supplied to the load circuit 60.

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

  FIG. 4 is a waveform diagram showing the circulating current ic2 and the reverse circulating current -ic2 in FIG. In FIG. 4, the horizontal axis represents time (t) and the vertical axis represents current (i).

In the circuit of FIG. 1, when the FETs 11 and 51 are in an off state and the FETs 12 and 52 are in an on state, a circulating current ic1 as shown by a one-dot chain line arrow in FIG. This circulating current ic1 is the interwinding capacitance 47, resistor 46, connection point N4, leakage inductor 25, primary winding 31 of the laminated transformer 30, resistor 26, connection point N5, resistor 48, interwinding capacitance 49, connection. Point N7, leakage inductor 44, resistor 43, secondary winding 33 of laminated transformer 30, center tap TP, resistor 45, node N8, output capacitor 53, resistor 54, node N9, body diode 51a of FET 51 in the off state , And the path of the connection point N6 and the interwinding capacitance 47. Assuming that the voltage per unit time is dv / dt, a large dv / dt voltage is applied to the location of the interwinding capacitance 49.

  Corresponding to the circulating current ic1, a circulating current ic2 as shown in FIG. 4 flows, and an oscillating current oc is generated in the circulating current ic2. The reverse circulation current -ic2 is a current that flows in a direction opposite to the circulation current ic2, and an oscillating current oc is generated in the same manner as the circulation current ic2. The circulating currents ic2 and -ic2 are currents that are times the turns ratio of the primary winding 31 and the secondary winding 33 of the laminated transformer 30, and the secondary winding 33, the resistor 45, the connection point N8, the output capacitor 53, It flows through the path of the resistor 54, the connection point N 9, the FET 52 in the ON state, the connection point N 7, the leakage inductor 44, the resistance 43, and the secondary winding 33. Therefore, the loss increases due to the generation of the oscillating current oc.

(II) Example of Primary Side Circuit Configuration in Multilayer Transformer 30 In the switching power supply device 1 of FIG. 1, the primary side circuit configuration using the multilayer transformer 30 is changed, and the primary winding 31 of the multilayer transformer 30 and The voltage applied between the secondary windings 32 and 33 was investigated and the loss was examined.

  FIG. 5A is an equivalent circuit diagram that simplifies the switching power supply device 1 when the resonant circuit 20 is connected between the source and drain of the upper FET 11, as in FIG. 1. In FIG. 5A, elements common to the elements in FIG.

  In the equivalent circuit of FIG. 5A, the rectifier circuit 50 is equivalently illustrated by two diodes 51A and 52A. A measuring instrument (for example, an oscilloscope) 71 for measuring the voltage waveform Vct1 is connected instead of the interwinding capacitance 47 between the primary winding 31 and the secondary winding 32 in FIG. Further, a measuring instrument (for example, an oscilloscope) 72 for measuring the voltage waveform Vct2 is connected instead of the interwinding capacitance 49 between the primary winding 31 and the secondary winding 33 in FIG.

  FIG. 5B is a diagram showing voltage waveforms Vt1 and Vct2 measured by the oscilloscopes 71 and 72 in FIG. 5A. In FIG. 5B, the horizontal axis represents time (t) and the vertical axis represents voltage (V).

  As shown in FIG. 5A, voltage waveforms Vct1 and Vct2 applied between the primary winding 31 and the secondary windings 32 and 33 of the laminated transformer 30 were measured using oscilloscopes 71 and 72, as shown in FIG. 5B. In addition, it was found that a voltage Vh having a large dv / dt was applied to the voltage waveform Vct2. The voltage Vh generates an oscillating current oc as shown in FIG.

  For this reason, as shown in FIGS. 3A to 3D, an experiment was performed in which the layer configuration of the laminated transformer 30 was changed and the layer position of the loosely coupled SCS was changed. The loss of “loose coupling from one side” shown in FIG. This is considered that the capacitance loss Lc can be reduced by reducing the inter-winding capacitance 49 of the layer on the voltage waveform Vct2 side where the potential change is large.

(III) Determination of Optimal Layer Configuration in 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 varies 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 which 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 generated by a current flowing through the interwinding capacitances 47 and 49. In addition, stray loads due to eddy currents are also included. Since losses other than the iron loss Li, the copper loss Lr, and the capacity loss Lc are small, it is desirable that the total transformer loss Lt in the laminated transformer 30 is represented by the iron loss Li, the copper loss Lr, and the capacity loss Lc.

  6A is a diagram illustrating a loss L (W) (that is, a transformer total loss Lt, an iron loss Li, a copper loss Lr, and a capacitance loss Lc) with respect to the layer configuration of the multilayer transformer 30 illustrated in FIGS. 3B, 3C, and 3D. It is. In FIG. 6A, the horizontal axis represents the layer configuration 3B, 3C, 3D of the laminated transformer 30, and the vertical axis represents the loss L (W).

  As shown in FIG. 3B and FIG. 3C, the copper loss Lr, which is an AC resistance, slightly increases by using a loosely coupled SCS between layers where the potential variation between the primary winding 31 and the secondary windings 32 and 33 is large. However, the effect of reducing the interwinding capacitances 47 and 49, which are parasitic capacitances, is greater than that, and the capacitance loss Lc can be reduced. Further, since the capacitance loss Lc is small between the layers with small potential fluctuations, the copper loss Lr can be minimized by using the tightly coupled DCS. In the above combination, as shown in FIG. 6A, it is possible to realize a layer configuration in which the overall transformer loss Lt is minimized.

  When designing an actual transformer, it is necessary to make an optimum layer configuration while observing the balance between the capacitance loss Lc and the copper loss Lr. The laminated transformer 30 in the switching power supply device 1 shown in FIG. 1 according to the first embodiment employs the layer configuration shown in FIG. 3B.

(IV) Formation Example of Loosely Coupled SCS Loosely coupled SCS for reducing the capacitance loss Lc is an insulating layer (for example, printed wiring board 31.1-31.8, 32 / 33.1-32 / 33.8). The insulating plates 31c, 32c, 33c) are thickened, or the insulating layers (for example, the insulating plates 31c, 32c of the printed wiring boards 31.1-31.8, 32, 33.1-32, 33.8) are used. , 33c) may be reduced.

  FIG. 6B is a diagram illustrating an experimental result of the loss L (W) with respect to the thickness of the insulating plates 31c, 32c, and 33c. In FIG. 6B, the horizontal axis represents capacitance C (pF), and the vertical axis represents loss L (W). In the horizontal axis, the thickness of the insulating plates 31c, 32c, and 33c is thin in the right direction of the arrow (Tn) and thick in the left direction of the arrow (Tk).

  As shown in FIG. 6B, if the insulating plates 31c, 32c, and 33c are thickened, the distance between the conductive coil layers in the laminated printed wiring boards 31.1-31.8, 32.33.1-32, and 33.8. Becomes larger. As a result, the copper loss Lr is increased, but the capacitance loss Lc is greatly reduced as compared with the increase in the copper loss Lr, so that the total transformer loss Lt is reduced. Accordingly, the capacitance loss Lc can be reduced by increasing the thickness of the insulating plates 31c, 32c, and 33c and increasing the distance between the conductive coil layers as indicated by Tk in the left direction of the arrow.

  FIG. 6C is a diagram illustrating an experimental result of the loss L (W) with respect to the relative dielectric constant εr of the insulating plates 31c, 32c, and 33c.

  As shown in FIG. 6C, when the relative dielectric constant εr of the insulating plates 31c, 32c, and 33c is decreased, the iron loss Li increases. However, the capacitance loss Lc greatly decreases as compared with the increase in the iron loss Li. The total transformer loss Lt is reduced. Accordingly, it is possible to reduce the dielectric loss εr of the insulating plates 31c, 32c, and 33c and reduce the capacitance loss Lc.

  In order to reduce the relative dielectric constant εr of the insulating plates 31c, 32c, and 33c, for example, the insulating plates 31c, 32c, and 33c may be formed of an insulating material having a low dielectric constant.

(Effect of Example 1)
According to the first embodiment, the primary winding 31 and the secondary winding at the layer position of the electromagnetically loosely coupled SCS between the primary winding 31 and the secondary windings 32 and 33 in the laminated transformer 30. The inter-winding capacitance 49 between 33 is reduced, and the capacitance loss Lc can be reduced. Thereby, the switching power supply device 1 having the laminated transformer 30 can be made highly efficient simply and easily.

(Configuration and operation of the second embodiment)
FIG. 7A is an equivalent circuit diagram showing a switching power supply apparatus 1A according to the second embodiment of the present invention. In FIG. 7A, the same code | symbol is attached | subjected to the element which is common in the element in FIG. 5A which shows Example 1. FIG.

  FIG. 7A shows an equivalent circuit diagram that simplifies the switching power supply device 1 </ b> A when the resonance circuit 20 is connected between the source and drain of the lower FET 12.

  FIG. 7B is a diagram showing voltage waveforms Vct1 and Vct2 measured by the oscilloscopes 71 and 72 in FIG. 7A. Similar to FIG. 5B showing Example 1, in FIG. 7B, the horizontal axis represents time (t) and the vertical axis represents voltage (V).

  As shown in FIG. 7A, voltage waveforms Vct1 and Vct2 applied between the primary winding 31 and the secondary windings 32 and 33 were measured. As shown in FIG. 7B, the voltage waveform Vct1 has a dv / dt of It was found that a large voltage Vh was applied. The voltage Vh generates an oscillating current oc as shown in FIG.

  Therefore, from the experimental results shown in FIGS. 3A to 3D, the loss of “loosely coupled from one side” shown in FIG. This is considered that the capacitance loss Lc could be reduced by reducing the inter-winding capacitance 47 of the layer on the voltage waveform Vct1 side where the potential change is large.

(Effect of Example 2)
According to the second embodiment, the primary winding 31 and the secondary winding at the layer position of the electromagnetic loosely coupled SCS between the primary winding 31 and the secondary windings 32 and 33 in the laminated transformer 30. The interwinding capacitance 47 between 32 is reduced, and the capacitance loss Lc can be reduced. As a result, the switching power supply device 1A having the laminated transformer 30 can be made highly efficient simply and easily.

(Configuration and operation of Example 3)
FIG. 8A is an equivalent circuit diagram illustrating the switching power supply device 1B according to the third embodiment of the present invention. In FIG. 8A, elements common to the elements in FIGS. 5A and 7A showing the first and second embodiments are denoted by the same reference numerals.

  FIG. 8A shows an equivalent circuit diagram in which the switching power supply device 1B when the switching circuit 10 is replaced with a full bridge type switching circuit 10A is simplified.

  In the equivalent circuit of FIG. 8A, the full bridge type switching circuit 10 </ b> A includes four FETs 11, 12, 13, and 14. The resonance circuit 20 is connected between the connection point of the two FETs 11 and 12 and the connection point of the other two FETs 13 and 14. The two FETs 11 and 14 and the two FETs 12 and 13 are complementarily turned on / off with a dead time.

  FIG. 8B is a diagram showing voltage waveforms Vct1 and Vct2 measured by the oscilloscopes 71 and 72 in FIG. 8A. Like FIG. 5B and FIG. 7B which show Example 1 and Example 2, in FIG. 8B, a horizontal axis is time (t) and a vertical axis | shaft is a voltage (V).

  As shown in FIG. 8A, the voltage waveforms Vct1 and Vct2 applied between the primary winding 31 and the secondary windings 32 and 33 were measured. As shown in FIG. 8B, the two voltage waveforms Vct1 and Vct2 In both cases, it was found that voltages Vh1 and Vh2 having large dv / dt were respectively applied. Oscillating current oc as shown in FIG. 4 is generated by these voltages Vh1 and Vh2.

  Therefore, from the experimental results shown in FIGS. 3A to 3D, the loss of “loose coupling from the outside” shown in FIG. 3D is the smallest when layers on both sides of the voltage waveforms Vct1 and Vct2 having large potential changes are loosely coupled SCS. This is considered that the capacitance loss Lc can be reduced by reducing the inter-winding capacitances 47 and 49 in the layers on both sides of the voltage waveforms Vct1 and Vct2 having a large potential change.

  As can be seen from FIGS. 5A, 5B, 7A, 7B, 8A, and 8B, the voltage between the primary winding 31 and the secondary windings 32 and 33 is determined by the circuit configuration on the primary side of the laminated transformer 30. Since the waveforms Vct1 and Vct2 are different, the layer positions to be loosely coupled SCS are different.

(Effect of Example 3)
According to the third embodiment, the primary winding 31 and the secondary winding at the layer position of the electromagnetic loose coupling SCS between the primary winding 31 and the secondary windings 32 and 33 in the laminated transformer 30. The interwinding capacitances 47 and 49 between 32 and 33 are reduced, and the capacitance loss Lc can be reduced. Thereby, the switching power supply device 1B having the laminated transformer 30 can be made highly efficient simply and easily.

(Modification of Example 1-3)
The present invention is not limited to Examples 1-3 described above, and various usage forms and modifications are possible. For example, the following forms (a) to (d) are used as the usage form and the modified examples.

  (A) The laminated transformer 30 is not limited to the configuration shown in FIG. 2A. In the embodiment, two secondary windings 32 and 33 are provided. However, for example, even a laminated transformer having one primary winding 31 and one secondary winding 32 may be Applicable.

  (B) The laminated transformer 30 is not limited to the structure shown in FIGS. 2B to 2E. In the iron core 34 of the embodiment, an EI type iron core is used, but iron cores of other shapes such as an EE type, an EF type, an EER type, and an ETD type may be used. Further, in the embodiment, in order to form the loosely coupled SCS, the thickness of the insulating plates 31c, 32c, 33c in the printed wiring boards 31.1-31.8, 32, 33.1-32, 33.8 is increased. However, it is not limited to this. For example, a loosely coupled SCS is formed by inserting an insulating plate or insulating sheet as an insulating layer between the stacked printed wiring boards 31.1-31.8, 32, 33.1-32, 33.8. You may do it.

  (C) In the embodiment, the primary winding 31 and the secondary windings 32 and 33 are configured by the printed wiring boards 31.1-31.8, 32 · 33.1−32 · 33.8. It is not limited. For example, instead of the conductive coil layers 31e, 32e, and 33e formed on the printed wiring boards 31.1-31.8, 32, 33.1-32, and 33.8, a plurality of conductive layers respectively formed by wires. The primary winding 31 and the secondary windings 32 and 33 may be formed by laminating coil layers separated by a predetermined distance and inserting or filling an insulating member as an insulating layer between the conductive coil layers. .

  (D) The switching power supply devices 1, 1 </ b> A, 1 </ b> B using the laminated transformer 30 of the embodiment are not limited to the LLC resonant converter of FIG. 1. The LLC resonant converter of FIG. 1 may be changed to another circuit configuration. Further, the laminated transformer 30 of the embodiment can be used for other switching power supply devices than the LLC resonant converter.

1, 1A, 1B Switching power supply device 10, 10A Switching circuit 20 Resonant circuit 30 Laminated transformer 31 Primary winding 32, 33 Secondary winding 34 Iron core 31.1-31.8 First printed wiring board 31c First insulating plate 31e First conductive coil layer 32.1-32.8, 33.1-33.8, 32, 33.1-32, 33.8 Second printed wiring board 32c, 33c Second insulating plate 32e, 33e Second Conductive coil layer 47, 49 Capacitance between windings 50 Rectifier circuit 60 Load circuit

Claims (5)

A switching circuit that switches a DC voltage to an AC voltage;
A resonant circuit that resonates with an output voltage of the switching circuit;
A laminated transformer to which an output voltage of the resonant circuit is applied;
A rectifier circuit for rectifying the AC voltage output from the laminated transformer;
A switching power supply device comprising:
The laminated transformer is
A primary winding having a plurality of first conductive coil layers to which an output voltage of the resonant circuit is applied;
A secondary winding having a plurality of second conductive coil layers and outputting the AC voltage;
With
The plurality of first conductive coil layers and the plurality of second conductive coil layers are laminated via an insulating layer, and the primary winding and the secondary winding are electromagnetically coupled via an iron core. ,
Between windings between the first conductive coil layer big fluctuations in potential caused by the circulating current flowing through the capacitor and the second conductive coil layer between the secondary winding and the primary winding, electromagnetic sparse A switching power supply device having a layer structure to be combined. The laminated transformer further includes:
Between the smaller the first conductive coil layer of potential variation and the second conductive coil layer between the secondary winding and the primary winding, so the layer structure such that electromagnetic tightly coupled The switching power supply device according to claim 1, wherein: The loosely coupled layer is:
3. The switching power supply device according to claim 1, wherein the switching power supply device is formed by increasing a thickness of the insulating layer or reducing a relative dielectric constant of the insulating layer. 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 wiring boards each comprising:
The plurality of first printed wiring 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 wiring boards each comprising:
The plurality of second printed wiring boards are connected in series via through holes formed in the second insulating plates,
The loosely coupled layer is:
By increasing the thickness of the first insulating plate and the second insulating plate, or by reducing the relative dielectric constant of the first insulating plate and the second insulating plate,
The switching power supply device according to claim 1, wherein the switching power supply device is formed. 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 wiring boards each comprising:
The secondary winding is
A first secondary winding and a second secondary winding connected in parallel;
The first secondary winding and the second secondary winding are respectively
A second insulating plate having the insulating layer;
The second conductive coil layer formed on the second insulating plate;
A plurality of second printed wiring boards each comprising:
The plurality of second printed wiring boards are connected in series via through holes formed in the second insulating plates,
The loosely coupled layer is:
By increasing the thickness of the first insulating plate and the second insulating plate, or by reducing the relative dielectric constant of the first insulating plate and the second insulating plate,
The switching power supply device according to claim 1, wherein the switching power supply device is formed.

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