JP2007043765A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply in which the size of an inductor for resonance can be reduced even when the difference of voltage between the input and output a power conversion transformer is increased. <P>SOLUTION: The switching power supply comprises a switching circuit, a transformer for voltage conversion, and an inductor for resonance. The switching circuit comprises a switching element, and a capacitor connected in parallel with the switching element. The transformer for voltage conversion comprises a first core constituting a magnetic path in the shape of 8. A first winding provided on the primary, and second and third windings provided on the secondary are wound around the first core. The inductor for resonance comprises a second core constituting a magnetic path in the shape of 8. A first inductor for resonance connected in series with the second winding, and a second inductor for resonance connected in series with the third winding are wound around the second core. The inductor for resonance constitutes a resonance circuit together with the capacitor of the switching circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage resonance type switching power supply device.

  Conventionally, various types of switching power supply devices have been proposed and put into practical use. As one of them, as described in Patent Document 1, the input DC voltage Vin from the high-voltage battery is switched by switching operation of a switching circuit connected to the input winding of the power conversion transformer, and obtained by switching. There is a system in which the input AC voltage is input to the input winding of the power conversion transformer, and the output AC voltage converted by the power conversion transformer is taken out from the output winding of the power conversion transformer. Along with the switching operation of the switching circuit, the voltage appearing in the output winding is rectified by the rectifier circuit, then converted to the output DC voltage Vout by the smoothing circuit, and output.

  In this type of switching power supply device, the switching circuit is, for example, a full bridge type inverter circuit in which four switch elements are bridge-connected, and a capacitor is connected in parallel to each switch element. This capacitor and the resonant inductor connected in series between the switching circuit and the power conversion transformer constitute a resonant circuit, and the resonance voltage is used to reduce the surge voltage generated by turning on and off the switching element. Is done.

International Publication No. WO01-071896 Pamphlet

  By the way, when the voltage difference between the input and output of the power conversion transformer is increased, it is necessary to increase the number of turns of the resonance inductor to increase the inductance. Further, in order to increase the insulation distance between the winding and the magnetic core, it is necessary to increase the thickness of the insulating material provided between them. Thus, when the voltage difference between the input and output of the power conversion transformer is increased, it is necessary to increase the number of turns or increase the thickness of the insulating material, which increases the size of the resonant inductor. There is a possibility that the switching power supply device may be hindered in size reduction.

  The present invention has been made in view of such problems, and the object thereof is to reduce the size of the resonance inductor even when the voltage difference between the input and output of the power conversion transformer is increased. The object is to provide a switching power supply.

  The switching power supply device of the present invention includes a switching circuit, a voltage conversion transformer, a rectifier circuit, and a resonance inductor. The switching circuit is an inverter circuit that includes a switching element and a capacitor connected in parallel to the switching element, and converts a DC input voltage into an AC voltage. The voltage conversion transformer includes a first magnetic core that forms a magnetic path in an 8-shape, and a primary side winding, a secondary side first winding, and a secondary side that are respectively wound around the first magnetic core. The second winding is provided, and the alternating voltage from the switching circuit is stepped down and output. The primary winding is provided on the primary side of the voltage conversion transformer, and is connected to the switching circuit so that the direction of the current flowing through the primary winding changes according to the operation of the switching circuit. The secondary side first winding and the secondary side second winding are respectively provided on the secondary side of the voltage conversion transformer, and one end of each is connected to each other. The rectifier circuit rectifies the output AC voltage on the secondary side of the voltage conversion transformer. The resonance inductor includes a second magnetic core that forms a magnetic path in an 8-shape, and a first resonance inductor and a second resonance inductor that are wound around the second magnetic core, respectively. The first resonance inductor is provided in the first path from the connection point of the secondary side first winding and the secondary side second winding to the end of the rectifier circuit via the secondary side first winding. The second resonance inductor is provided in the second path from the connection point to the end of the rectifier circuit via the secondary side second winding. This resonance inductor constitutes a resonance circuit together with a capacitor of the switching circuit.

  The second magnetic core is configured, for example, by superposing E-type magnetic cores on each other, or superposing E-type magnetic cores and I-type magnetic cores on each other. As a method of superimposing the E-type magnetic core and the I-type magnetic core, for example, a method of placing the I-type magnetic core on the support base and superposing the E-type magnetic core thereon, or E There is a method of placing a mold magnetic core and superimposing an I-shaped magnetic core thereon.

  Further, the first magnetic core and the second magnetic core may be configured by superimposing an E-type magnetic core and an I-type magnetic core, respectively. At this time, it is preferable that the I-type magnetic cores of the first magnetic core and the second magnetic core are made common. However, the first magnetic core and the second magnetic core need to be independent from each other. Here, “independent of each other” means that not only the two E-type magnetic cores are spatially separated, but the magnetic paths of the first magnetic core and the second magnetic core are separate magnetic paths. It is magnetically separated to the extent that it can be equated with.

  In the switching power supply device of the present invention, a high-voltage DC input voltage is once converted into an AC voltage by a switching circuit, and then the AC voltage is transformed (stepped down) by a voltage conversion transformer. At this time, resonance is caused by the capacitor of the switching circuit provided on the primary side of the voltage conversion transformer and the first resonance inductor and the second resonance inductor of the resonance inductor provided on the secondary side of the voltage conversion transformer. A surge voltage generated by turning on and off the switching element is reduced by configuring a circuit and utilizing the resonance characteristics thereof.

  Thus, by providing the first resonance inductor and the second resonance inductor constituting the resonance circuit on the secondary side of the step-down voltage conversion transformer, these resonances can be obtained compared to the case where the resonance circuit is provided on the primary side. The voltage input to the inductor for the inductor is reduced, and the number of turns of the resonant inductor can be reduced. As a result, the winding does not have multiple layers, and even if an insulating material is provided between the winding and the magnetic core, it is not necessary to increase the thickness of the insulating material. This is the same even when the voltage difference between the input and output of the step-down power conversion transformer is increased.

  According to the switching power supply device of the present invention, the first resonance inductor and the second resonance inductor constituting the resonance circuit are provided on the secondary side of the step-down voltage conversion transformer. Even when the voltage difference between the input and output is increased, the resonant inductor can be made smaller than in the case where it is provided on the primary side of a conventional step-down voltage conversion transformer. Become.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration of a switching power supply apparatus according to an embodiment of the present invention. This switching power supply device functions as a DC-DC converter that converts the high-voltage DC input voltage Vin supplied from the high-voltage battery HB into a lower DC output voltage Vout and supplies the same to the load L, which will be described later. Thus, the secondary side is a switching power supply with a center tap type cathode common connection.

  This switching power supply device has a three-winding transformer 2 (voltage converting transformer) configured to include a primary winding 22 and secondary windings 23 and 24. An inverter circuit 1 (switching circuit) is provided on the primary side of the transformer 2, and a resonance inductor 3, a rectifier circuit 4, and a smoothing circuit 5 are provided on the secondary side. The inverter circuit 1 is provided between the primary high voltage line L1H and the primary low voltage line L1L.

  An input terminal T1 is provided on the primary high voltage line L1H, and an input terminal T2 is provided on the primary low voltage line L1L. These input terminals T1 and T2 are connected to the output terminal of the high voltage battery HB. It has become. An output terminal T3 is provided on the output line L0, which is a high-voltage side line of the smoothing circuit 5, and an output terminal T4 is provided on the ground line LG, which is a low-voltage side line of the smoothing circuit 5, respectively. T4 is connected to the input / output terminal of the load L.

  The inverter circuit 1 is a single-phase inverter circuit that converts a DC input voltage Vin output from the high-voltage battery HB into a substantially rectangular wave-shaped single-phase AC voltage. The inverter circuit 1 is a full bridge type switching circuit formed by full bridge connection of four switching elements 11, 12, 13, and 14 driven by switching signals supplied from a control circuit (not shown). . As the switching element, for example, an element such as a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) is used. Further, the capacitors 15, 16, 17, and 18 are connected in parallel to the switching elements 11, 12, 13, and 14, respectively. Note that when the switching element is configured by a MOS-FET, the parasitic capacitance of the MOS-FET may be used as the capacitors 15, 16, 17, and 18.

  The switching element 11 is provided between one end of the primary side winding 22 of the transformer 2 and the primary side high voltage line L1H, and the switching element 12 includes one end of the primary side winding 22 and the primary side low voltage line L1L. It is provided between. The switching element 13 is provided between the other end of the primary winding 22 and the primary high voltage line L1H, and the switching element 14 is provided between the other end of the primary winding 22 and the primary low voltage line L1L. Is provided.

  Thus, the inverter circuit 1 is switched from the primary high voltage line L1H to the primary low voltage line L1L through the switching element 11, the primary winding 11A and the switching element 14 in order from the ON operation of the switching elements 11 and 14. While the current flows through the first current path, the switching elements 12 and 13 are turned on, so that the primary side passes through the switching element 13, the primary winding 22 and the switching element 12 in order from the primary high voltage line L1H. A current flows through the second current path that reaches the low-voltage line L1L.

  The transformer 2 includes a primary side winding 22 (primary side winding), a secondary side winding 23 (secondary side first winding), and a secondary side winding 24 (secondary side second winding). The magnetic elements are magnetically coupled by being wound around the magnetic core 21 so as to have polarities in the same direction. The transformer 2 is a step-down transformer, and the number of turns of the secondary winding 23 and the secondary winding 24 is smaller than that of the primary winding 22.

  A pair of secondary windings 23 and 24 of the transformer 2 are connected to each other at a center tap C (connection point) via a first resonance inductor 32 and a second resonance inductor 33 which will be described later, and the center tap C is grounded. It is connected to the output terminal T4 via a line LG. That is, the secondary side of the transformer 2 is a center tap type connection. As a result, the transformer 2 transforms (steps down) the AC voltage converted by the inverter circuit 1, and the AC is 180 degrees out of phase with each other from the ends A and B of the pair of secondary windings 23 and 24. The voltages VO1 and VO2 are output. Note that the degree of transformation in this case is determined by the turn ratio between the primary side winding 22 and the secondary side windings 23 and 24.

  The resonance inductor 3 includes a magnetic core 31 (second magnetic core), a first resonance inductor 32 and a second resonance inductor 33 wound around the magnetic core 31. The first resonance inductor 32 is separated into two inductors 32A and 32B in a magnetically coupled state. One end of the inductor 32A is connected in series to one end of the secondary winding 23 of the transformer 2, and the inductor 32B One end is connected in series to the other end of the secondary winding 23 of the transformer 2. The other end of the inductor 32A is connected to the rectifier circuit 4, and the other end of the inductor 32B is connected to the center tap C. Similarly, the second resonance inductor 33 is separated into two inductors 33A and 33B in a magnetically coupled state, and one end of the inductor 33A is connected in series to one end of the secondary side winding 24 of the transformer 2, and the inductor One end of 33B is connected in series to the other end of the secondary winding 24 of the transformer 2. The other end of the inductor 33A is connected to the rectifier circuit 4, and the other end of the inductor 33B is connected to the center tap C.

  A path from the center tap C to the connection point D (described later) that is the terminal end of the rectifier circuit 4 via the secondary winding 23 corresponds to the “first path” of the present invention. A path from the secondary winding 24 to the connection point D (described later) that is the end of the rectifier circuit 4 corresponds to a “second path” of the present invention.

  Thereby, at least one of the capacitors 15, 16, 17, and 18 of the switching circuit 1 provided on the primary side of the voltage conversion transformer 2 and the resonance inductor 3 provided on the secondary side of the voltage conversion transformer 3. A resonance circuit is configured by the first resonance inductor 32 and the second resonance inductor 33, and a surge voltage generated by turning on and off the switching element is reduced by utilizing the resonance characteristics. ing.

  Here, the transformer 2 is a step-down type as described above, and the voltage on the secondary side of the transformer 2 is lower than the voltage on the primary side, so that the first resonance inductor 32 and the second resonance inductor 33 The number of turns can be reduced as compared with the case where the resonance circuit is provided on the primary side of the transformer 2 as in the prior art, and the number of turns can be reduced to one. Even if it is necessary to provide an insulating material (not shown) between the first resonance inductor 32 and the second resonance inductor 33 and the magnetic core 31, it is necessary to provide an insulating material (not shown) between them. Since the voltage applied to the first resonance inductor 32 and the second resonance inductor 33 is low, the insulating material can be made thinner or eliminated. Thereby, the resonance inductor 3 can be made a simple and small structure.

  Further, as described above, since the number of turns of each of the first resonance inductor 32 and the second resonance inductor 33 can be one, the first resonance inductor 32 and the second resonance inductor 33 are also used. Can be formed of a single sheet metal plate. Thereby, even when a large current is passed through the secondary side of the transformer 2, the resonance inductor 3 can have a simple and small structure.

  Incidentally, each of the magnetic core 21 and the magnetic core 31 has an 8-shaped magnetic path. The magnetic core 21 includes a first magnetic core 21A and a second magnetic core 21B. The first magnetic core 21A is placed on a conductive support base (not shown) and on the first magnetic core 21A. The second magnetic core 21B is superposed. Similarly, the magnetic core 31 includes a first magnetic core 31A and a second magnetic core 31B. The first magnetic core 31A is placed on a conductive support base (not shown) and the first magnetic core is arranged. The second magnetic core 31B is superposed on 31A.

  Here, the first magnetic core 21A and the second magnetic core 21B may have the same shape or different shapes. Similarly, the first magnetic core 31A and the second magnetic core 31B may have the same shape or different shapes. For example, as shown in FIG. 4, the first magnetic core 21 </ b> A, the second magnetic core 21 </ b> B, the first magnetic core 31 </ b> A, and the second magnetic core 31 </ b> B are all E-shaped. (First case) can be considered. As a different form, for example, the first magnetic core 21A and the first magnetic core 31A are both I-shaped, and the second magnetic core 21B and the second magnetic core 31B are both E-shaped (second case) Case) or, conversely, the first magnetic core 21A and the first magnetic core 31A are both E-shaped, and the second magnetic core 21B and the second magnetic core 31B are both I-shaped (third case). ) Is considered.

  In the second case, as shown in FIG. 5, it is preferable that the first magnetic core 21A and the first magnetic core 31A are composed of a common I-type magnetic core 21C. In the third case, As shown in FIG. 6, it is preferable that the second magnetic core 21B and the second magnetic core 31B are configured by a common I-type magnetic core 21D. Thereby, compared with the case where the shape of a magnetic core is mutually equal, the number of parts can be reduced by one.

  However, when the I-type magnetic core of the transformer 2 and the I-type magnetic core of the resonance inductor 3 are shared, it is necessary that the magnetic core 21 and the magnetic core 31 are independent from each other. Here, “independently from each other” means that not only the two E-type magnetic cores are spatially separated but each magnetic path of the magnetic core 21 and the magnetic core 31 is regarded as a separate magnetic path. It is magnetically separated as much as possible. As described above, even if the I-type magnetic core of the transformer 2 and the I-type magnetic core of the resonance inductor 3 are made common, if the magnetic core 21 and the magnetic core 31 are independent from each other, the magnetism of the transformer 2 can be obtained. The core 21 and the magnetic core 31 of the resonance inductor 3 do not affect each other, and there is no possibility that the respective inductances fluctuate and deviate from desired values. This has been confirmed by numerical simulation.

  By the way, since the surface of the magnetic core is generally warped, it is necessary to polish the surface of the surface of the magnetic core in contact with the support base and other magnetic cores. However, in the first case, The first magnetic core 21A, the second magnetic core 21B, the first magnetic core 31A, and the second magnetic core 31B have a common shape, and can be arranged on either the upper side or the lower side for mounting. A total of four sides, both sides of the core and both sides of the E-type magnetic core, must be polished. On the other hand, in the second case (including the case where the I-type magnetic core is used in common), it is only necessary to polish a total of three surfaces of both the I-type magnetic core and one side of the E-type magnetic core. In this case (including the case where the I-type magnetic core is shared), only one surface of the I-type magnetic core and both sides of the E-type magnetic core need to be polished. Thus, the number of polished surfaces can be reduced by one in the second case and the third case (both including the case where the I-type magnetic core is shared) as compared with the first case.

  Further, in order to fix the magnetic core to the support base, a fixing metal fitting is required. In the first case, the second case (including the case where the I-type magnetic core is shared) and the third case, Two metal fittings for fastening the magnetic core 21 on the transformer 2 side and the magnetic core 31 on the resonance inductor 3 side are required. On the other hand, in the case where the I-type magnetic core is shared in the third case, the I-type magnetic core is arranged on the upper side, so only one metal fitting is required. As a result, the number of parts can be reduced compared to the other cases. It can be reduced by one.

  The rectifier circuit 4 is a single-phase full-wave rectifier type composed of a pair of diodes 41 and 42. The anode of the diode 41 is connected to one end of the first resonance inductor 32, and the anode of the diode 42 is connected to one end of the second resonance inductor 33. The cathodes of the diodes 41 and 42 are connected to each other at the connection point D and to the output line LO. In other words, the rectifier circuit 4 has a cathode common connection structure, and rectifies each half-wave period of the AC output voltages VO1 and VO2 of the transformer 2 by the diodes 41 and 42, respectively, to obtain a DC voltage. It has become.

  The smoothing circuit 5 includes a choke coil 51 and a smoothing capacitor 52. The choke coil 51 is inserted into the output line LO, and one end thereof is connected to the connection point D and the other end is connected to the output terminal T3. The smoothing capacitor 52 is connected between the other end of the choke coil 51 and the ground line LG. With such a configuration, the smoothing circuit 5 smoothes the DC voltage rectified by the rectifying circuit 4 to generate the DC output voltage Vout, and supplies this to the load L from the output terminals T3 and T4. .

  Next, the operation of the switching power supply device configured as described above will be described. In the following, the case where the inverter circuit 1 is driven by a general switching operation will be described. However, for example, the inverter circuit 1 can also be driven by a zero volt switching operation.

  When the switching elements 11 and 14 of the inverter circuit 1 are turned on, current flows from the switching element 11 to the switching element 14, and the voltages VO 1 and VO 2 appearing on the secondary side windings 23 and 24 of the transformer 2 are applied to the diode 42. The reverse direction and the forward direction with respect to the diode 41. For this reason, a current flows from the secondary winding 11B through the diode 41 to the output line LO.

  Next, when the switching elements 11 and 14 are turned off from on, the voltage [−VO2] appearing in the secondary winding 24 of the transformer 2 becomes forward with respect to the diode 42. For this reason, a current flows from the secondary winding 24 through the diode 42 to the output line LO.

  Next, when the switching elements 12 and 13 are turned on, current flows from the switching element 13 to the switching element 12, and the voltages [−VO1] and [−VO2] appearing in the secondary windings 23 and 24 of the transformer 2 are generated. The forward direction is relative to the diode 42, while the reverse direction is relative to the diode 41. For this reason, a current flows from the secondary winding 24 through the diode 42 to the output line LO.

  Finally, when the switching elements 12 and 13 are turned off from on, the voltage [−VO1] appearing in the secondary winding 23 of the transformer 2 becomes forward with respect to the diode 41. For this reason, a current flows from the secondary winding 23 through the diode 41 to the output line LO.

  In this way, the power supply main body 10 transforms (steps down) the DC input voltage Vin supplied from the high voltage battery HB to the DC output voltage Vout, and supplies the transformed DC output voltage Vout to the low voltage battery LB.

  At this time, at least one of the capacitors 15, 16, 17 and 18 of the switching circuit 1, the first resonance inductor 32 and the second resonance inductor 33 of the resonance inductor 3 constitute a resonance circuit, and its resonance characteristics. Is used to reduce the surge voltage generated by switching elements 11, 12, 13 and 14 on and off.

  As described above, the first resonance inductor and the second resonance inductor constituting the resonance circuit are provided on the secondary side of the voltage conversion transformer, so that these resonance inductors are provided compared to the case where the resonance circuit is provided on the primary side. The voltage input to can be reduced.

  Thus, in the switching power supply device according to the present embodiment, the first resonance inductor 32 and the second resonance inductor 33 that constitute the resonance circuit are provided on the secondary side of the voltage conversion transformer 2. As compared with the case where the resonance inductors 32 and 33 are provided, the voltage input to the resonance inductors 32 and 33 is small, and the number of turns of the resonance inductors 32 and 33 can be reduced. As a result, the winding does not have multiple layers, and even if an insulating material is provided between the winding and the magnetic core, it is not necessary to increase the thickness of the insulating material. This is the same even when the voltage difference between the input and output of the power conversion transformer is increased.

  Therefore, in the switching power supply device of the present embodiment, even when the voltage difference between the input and output of the power conversion transformer is increased, it is provided on the primary side of the voltage conversion transformer 2 as in the prior art. In comparison, the size of the resonance inductor 3 can be reduced.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to these, and various modifications are possible.

  For example, in the switching power supply device of the above embodiment, the secondary side of the transformer 2 is a cathode common connection, but may be an anode common connection as shown in FIG. Further, the inverter circuit 1 was a full bridge type, but as shown in FIGS. 8A to 8E, the forward type 1-1, the forward type 1-2 with a reset winding, and the double forward type It may be a mold 1-3, a push-pull mold 1-4, a half-bridge mold 1-5, or the like.

  In the switching power supply device of the above embodiment, the pair of secondary windings 23 and 24 of the transformer 2 are connected to the center tap C via the first resonance inductor 32 and the second resonance inductor 33 of the resonance inductor 3. However, the pair of secondary windings 23 and 24 of the transformer 2 may be directly connected to the center tap C as shown in FIGS. 9 to 11. At this time, when the first magnetic core 21A of the transformer 2 and the first magnetic core 31A of the resonance inductor 3 are respectively configured by I-type magnetic cores, as shown in FIGS. A common core may be used.

  Further, the secondary side connection relationship of the transformer 2 may be, for example, FIG. 14 to FIG. 16, FIG. 18 to FIG. 20, FIG. The form as shown in FIG. 24 may be used. It should be noted that the secondary side connection relationship of the transformer 2 is configured as shown in FIGS. 14 to 16 and FIGS. 18 to 20, and the first magnetic core 21A of the transformer 2 and the resonance inductor are used. When the three first magnetic cores 31A are each formed of an I-type magnetic core, the respective I-type magnetic cores may be shared as shown in FIG. 17, FIG. 21, and FIG.

  Even in the case of various connection relationships as described above, the first resonance inductor 32 is connected to the connection point D (from the center tap C through the secondary winding 23 as in the above embodiment. The second resonance inductor 33 is provided in the path from the center tap C to the connection point D (terminal of the rectifier circuit 4) via the secondary winding 24. Is provided.

  In the switching power supply of the above embodiment, the secondary side of the transformer 2 is a center tap type. However, other configurations may be used, such as a forward type, a current doubler type, a full bridge type, etc. There may be. However, in such a configuration, since there is one secondary winding of the transformer 2, the first resonance inductor 32 is provided at one end of the secondary winding and the secondary winding. The second resonance inductor 33 is connected in series to the other winding on the other side.

It is a circuit diagram showing the structure of the switching power supply device which concerns on one embodiment of this invention. FIG. 2 is a top view of the magnetic cores of the transformer and the resonance inductor of FIG. 1. It is a side view of the magnetic core of FIG. It is a perspective view of the magnetic core of FIG. It is a side view showing the modification of the magnetic core of FIG. It is a side view showing the other modification of the magnetic core of FIG. It is a circuit diagram showing the structure of the modification of a switching power supply device. It is a circuit diagram showing the various modifications of a switching circuit. It is a circuit diagram showing the structure of the other modification of a switching power supply device. FIG. 10 is a top view of the magnetic core in FIG. 9. FIG. 10 is a side view of the magnetic core in FIG. 9. FIG. 10 is a side view illustrating a modification of the magnetic core in FIG. 9. It is a side view showing the other modification of the magnetic core of FIG. It is a circuit diagram showing the structure of the other modification of a switching power supply device. It is a top view of the magnetic core of FIG. It is a side view of the magnetic core of FIG. It is a side view showing the other modification of the magnetic core of FIG. It is a circuit diagram showing the structure of the other modification of a switching power supply device. It is a top view of the magnetic core of FIG. It is a side view of the magnetic core of FIG. It is a side view showing the modification of the magnetic core of FIG. It is a side view showing the other modification of the magnetic core of FIG. It is a circuit diagram showing the structure of the other modification of a switching power supply device. It is a circuit diagram showing the structure of the other modification of a switching power supply device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inverter circuit, 2 ... Transformer, 3 ... Resonance inductor, 4 ... Rectifier circuit, 5 ... Smoothing circuit, 11, 12, 13, 14 ... Switching element, 15, 16, 17, 18 ... Capacitor, 21, 21A, 21B, 21C, 21D, 31, 31A, 31B ... magnetic core, 22 ... primary winding, 23,24 ... secondary winding, 32 ... first resonance inductor, 33 ... second resonance inductor, 41 , 42 ... Diode, 51 ... Choke coil 51, 52 ... Smoothing capacitor, A, B ... End, C ... Connection point, HB ... High voltage battery, L ... Load, L1H ... Primary high voltage line, L1L ... Primary side Low voltage line, LO ... Output line, LG ... Ground line, T1, T2 ... Input terminal, T3, T4 ... Output terminal, Vin ... Input DC voltage, Vout ... Output DC voltage.

Claims (6)

A switching circuit that includes a switching element and a capacitor connected in parallel to the switching element, and converts a DC input voltage into an AC voltage;
A first magnetic core that forms a magnetic path in the shape of a figure 8, and the switching circuit is wound around the first magnetic core so that the direction of the current flowing to itself changes according to the operation of the switching circuit. A primary winding that is connected, and a secondary first winding and a secondary secondary winding that are wound around the first magnetic core and are connected to each other at one end. A voltage conversion transformer that steps down and outputs an alternating voltage from the switching circuit;
A rectifier circuit for rectifying the output AC voltage on the secondary side of the voltage conversion transformer;
The rectification from the connection point of the second magnetic core that forms a magnetic path in the shape of figure 8 and the secondary side first winding and the secondary side second winding through the secondary side first winding A first resonance inductor provided in a first path to the end of the circuit and wound around the second magnetic core; and a termination of the rectifier circuit from the connection point via the secondary side second winding And a second resonance inductor wound around the second magnetic core, and a resonance inductor constituting a resonance circuit together with the capacitor. Switching power supply. The switching power supply according to claim 1, wherein the second magnetic core is configured by superimposing E-type magnetic cores on each other. The switching power supply according to claim 1, wherein the second magnetic core is configured by superimposing an E-type magnetic core and an I-type magnetic core on each other. 2. The first magnetic core and the second magnetic core are configured by superimposing two E-type magnetic cores independent of each other and a common I-type magnetic core on each other. The switching power supply device described in 1. Further comprising a support substrate;
The first magnetic core and the second magnetic core are configured by placing the I-type magnetic core on the support base and superimposing the two E-type magnetic cores on the I-type magnetic core, respectively. The switching power supply device according to claim 4, wherein the switching power supply device is a device. Further comprising a support substrate;
The first magnetic core and the second magnetic core are configured by placing the two E-type magnetic cores on the support base and superimposing the I-type magnetic core on the two E-type magnetic cores. The switching power supply device according to claim 4, wherein

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