JP2013214582A - Flyback transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flyback transformer that implements low noise and low loss simultaneously.SOLUTION: A tertiary winding 300, a primary winding 100 having first to third coils 101-103 connected in series, and a secondary winding 200 are wound on a leg portion 20a of an iron core 20. The primary winding 100 is connected to a DC power supply via an unshown power converting on-off element connected to the first coil 101. Power on the secondary winding generated by an on-off action of the on-off element is used to drive switching elements of a power converter, and power on the tertiary winding is supplied to another load. A distance of the secondary winding 200 from the first coil 101 experiencing the greatest voltage variation under the on-off action of the on-off element can reduce a high frequency noise current flowing owing to a stray capacitance therebetween. The intervention of the tertiary winding 300 can increase the distance between the first coil 101 and the leg portion 20a to reduce a high frequency noise current flowing owing to a stray capacitance therebetween and an eddy current loss of the primary winding 100 owing to a leakage flux about an air gap.

Description

  The present invention relates to an improvement of a flyback transformer in a DC power supply device used as, for example, a control power supply for a switching element of a power converter.

  In power converters represented by general-purpose inverter devices, power conversion is realized by high-speed on / off control of power conversion switching elements. In the general-purpose inverter device, the AC power of the three-phase system power supply is rectified by a converter and becomes DC power. Then, the power conversion switching element such as a MOSFET of the inverter circuit is subjected to switching control to be converted into AC power and supplied to the load. Here, an insulation type DC power supply device is used as a power source of a gate drive circuit for applying a voltage to the gate of the power conversion switching element to control the switching. There is a flyback converter as such an insulation type DC power supply. In a flyback converter, a primary winding wound around a core of a transformer as a flyback transformer is connected to a DC power source through a switching element, and the switching element is opened and closed at a high speed to flow through the primary winding. The current is intermittently connected at high speed, and the voltage generated in the secondary winding is rectified to obtain DC power, which is applied to the gate of a power conversion switch element such as a MOSFET of the inverter circuit to drive the power conversion switch element.

  In such a DC power supply transformer, cylindrical primary and secondary windings are concentrically wound around a core, and the primary winding is constituted by, for example, a double cylindrical coil inside and outside. The winding end of the inner coil and the winding start of the outer coil are connected in series, and the secondary winding is disposed outside the outer coil. Then, the winding start end of the inner coil is connected to the negative electrode of the DC power source via the switching element, and the winding end end of the outer coil is connected to the positive electrode of the DC power source, which is a stable voltage. In this case, since the switching element is connected to the winding start end of the inner coil, when the switching element is opened and closed, the inner coil has a larger voltage fluctuation than the outer coil, but the inner coil having a larger voltage fluctuation. Since the coil is disposed in the innermost layer far from the secondary winding, there is a configuration that is simple in structure and can reduce radiation noise (see, for example, Patent Document 1).

JP 2010-004633 A

The transformer as a conventional flyback transformer is configured as described above, and increases the distance between the inner coil having a large voltage fluctuation and the secondary winding among the coils constituting the primary winding. Low noise can be achieved because the stray capacitance is reduced. However, the fact that the inner coil is arranged in the innermost layer means that the primary winding is arranged at the closest position of the core. In many cases, the core material is a metal material such as a silicon steel plate or permalloy, or an oxide material such as ferrite. For this reason, when the primary winding is disposed at the closest position of the core, the stray capacitance between the primary winding and the core increases. This stray capacitance becomes a new noise current path, and the high-frequency noise current flowing through the stray capacitance increases, leading to an increase in noise. Further, when the core material is conductive, high-frequency noise current propagating through the stray capacitance propagates on the surface of the core material and becomes a radiation noise source, resulting in a large radiation noise.
In addition, when an air gap is provided in the core, when the primary winding is disposed at a position closest to the core, the primary winding has a large conductor cross-sectional area in order to pass a large current, and the conductor is interlinked. A large eddy current loss occurs due to leakage magnetic flux from the vicinity of the air gap. This eddy current loss is also a problem in thermal design.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a flyback transformer that can simultaneously realize low noise and low loss.

In the flyback transformer according to the present invention,
A DC power supply having a core, a primary winding, a secondary winding, and a tertiary winding, and supplying power for driving the switching element of a power converter that converts power by driving the switching element to open and close A flyback transformer used in the apparatus,
The core has a leg portion, and the leg portion has an air gap forming portion that forms an air gap.
The primary winding has a plurality of cylindrical coils arranged so as to form a plurality of layers, and the plurality of cylindrical coils are connected in series.
The secondary winding is formed in a cylindrical or annular shape,
The tertiary winding is formed in a cylindrical shape,
Surrounding the legs, the tertiary winding, the primary winding, and the secondary winding are arranged in multiple layers in this order,
The cylindrical coil of the innermost layer of the cylindrical coils of the primary winding is connected to one pole of a DC power source through a switch, and the outermost layer of the cylindrical coils of the primary winding is A cylindrical coil is connected to the other pole of the DC power source,
The power generated in the secondary winding by opening and closing the switch is supplied as the driving power for the switching element of the power converter, and the power generated in the tertiary winding is different from the switching element. 2 is supplied to the load.

The present invention provides power for driving the switching element of a power converter having a core, a primary winding, a secondary winding, and a tertiary winding, and converting the power by driving the switching element to open and close. A flyback transformer used for a DC power supply to supply,
The core has a leg portion, and the leg portion has an air gap forming portion that forms an air gap.
The primary winding has a plurality of cylindrical coils arranged so as to form a plurality of layers, and the plurality of cylindrical coils are connected in series.
The secondary winding is formed in a cylindrical or annular shape,
The tertiary winding is formed in a cylindrical shape,
Surrounding the legs, the tertiary winding, the primary winding, and the secondary winding are arranged in multiple layers in this order,
The cylindrical coil of the innermost layer of the cylindrical coils of the primary winding is connected to one pole of a DC power source through a switch, and the outermost layer of the cylindrical coils of the primary winding is A cylindrical coil is connected to the other pole of the DC power source,
The power generated in the secondary winding by opening and closing the switch is supplied as the driving power for the switching element of the power converter, and the power generated in the tertiary winding is different from the switching element. Since it is supplied to the load of 2,
A flyback transformer that can simultaneously realize low noise and low loss can be obtained.

It is sectional drawing which shows the structure of the flyback transformer which is Embodiment 1 of this invention. FIG. 2 is a winding diagram of the flyback transformer of FIG. 1. It is a block diagram of a general purpose inverter apparatus. FIG. 4 is a circuit diagram of an insulated gate drive circuit that drives the inverter circuit of FIG. 3. FIG. 5 is a circuit diagram of the flyback converter of FIG. 4. It is a schematic diagram of the voltage fluctuation of the coil | winding of the flyback transformer of FIG. It is explanatory drawing which shows an example of the path | route of the high frequency noise current which flows from a flyback transformer to an inverter circuit. It is explanatory drawing which shows the generation mechanism of another high frequency noise. It is a block diagram which shows the modification of the flyback transformer of FIG. It is sectional drawing which shows the structure of the flyback transformer which is Embodiment 2 of this invention. FIG. 11 is a winding diagram of the flyback transformer of FIG. 10. It is sectional drawing which shows the structure of the flyback transformer which is Embodiment 3 of this invention. It is sectional drawing which shows the structure of the modification of the flyback transformer of FIG. It is sectional drawing which shows the structure of the flyback transformer which is Embodiment 4 of this invention.

Embodiment 1 FIG.
1 to 8 show a first embodiment for carrying out the present invention. FIG. 1 is a sectional view showing a configuration of a flyback transformer, and FIG. 2 is a winding diagram of the flyback transformer of FIG. It is. 3 is a configuration diagram of a general-purpose inverter device, FIG. 4 is a circuit diagram of an insulated gate drive circuit for driving the inverter circuit of FIG. 3, and FIG. 5 is a circuit diagram of the flyback converter of FIG. 6 is a schematic diagram of voltage fluctuations in the winding of the flyback transformer of FIG. 5, and FIG. 7 is an explanatory diagram showing an example of a path of a high-frequency noise current flowing from the flyback transformer to the inverter circuit. FIG. 8 is an explanatory diagram showing another high-frequency noise generating mechanism. In FIG. 1, the arrow D at the left end indicates the center axis of the flyback transformer, and is a cross-sectional view of the right half of the flyback transformer. In FIG. 1, the flyback transformer 10 includes a core 20, a primary winding 100, a secondary winding 200, and a tertiary winding 300.

  The core 20 includes a first core 21 and a second core 22 made of ferromagnetic ferrite. The first core 21 includes a rectangular section arm 21a and 21b arranged at a predetermined distance and a yoke section 21c having a rectangular section that magnetically connects one end of each of the arms 21a and 21b. However, these are formed into a “U” shape. The second core 22 has a rectangular section armature 22a, 22b arranged at a predetermined distance and a yoke section 22c having a rectangular section that magnetically connects one end of each arm section 22a, 22b. However, these are formed into a “U” shape. The length of the arm portions 21a and 22a (the vertical dimension in FIG. 1) is shorter than the length of the arm portions 21b and 22b, and the arm portions 21b and 22b are moved in the vertical direction in FIG. When contacted, an air gap G having a predetermined length is formed between the arm portions 21a and 22a as air gap forming portions. A leg portion 20a of the core 20 is formed by the arm portions 21a and 22a.

  A tertiary winding 300 is formed in a cylindrical shape by winding a conductor around a flanged cylindrical bobbin (not shown). The primary winding 100 is wound in a cylindrical shape outside the tertiary winding 300, and the secondary winding 200 is wound in a cylindrical shape outside the primary winding 100. The primary winding 100 includes a cylindrical first coil 101, a second coil 102, and a third coil 103 having the same number of turns as a cylindrical coil, and the three first coils 101, the second coil 102, The third coil 103 is wound around the bobbin so as to form three layers concentrically in this order from the inside toward the outside. The first coil 101, the second coil 102, and the third coil 103 are connected in series to form the primary winding 100, and the turns ratio of the primary winding 100 and the secondary winding 200 is 3. : 1. The winding start end 100a of the primary winding 100 is indicated by a black circle ●, and the winding end end 100b is indicated by a white circle (◯). The winding start ends of the secondary winding 200 and the tertiary winding 300 are indicated by black circles ●, and the winding end ends are indicated by white circles (◯). As described above, the arm portion 21a of the first core 21 and the arm portion 22a of the second core 22 are inserted into the holes of the bobbin around which the tertiary winding 300, the primary winding 100, and the secondary winding 200 are wound. And the leg part 20a with an air gap as mentioned above is formed. The cylindrical tertiary winding 300, the primary winding 100, and the secondary winding 200 are arranged concentrically with the leg portion 20a of the core 20. A semiconductor element 8h (FIG. 5), which will be described later, is connected to the winding start end 100a of the primary winding 100.

  By the way, such a flyback transformer is used in a DC power supply device used as a power source for a gate drive circuit of a power conversion switching element of a power converter represented by a general-purpose inverter device, for example. FIG. 3 shows the configuration of the general-purpose inverter device. In FIG. 3, the AC power of the three-phase system power supply 1 is rectified by the converter 2, smoothed by the smoothing capacitor 3, and becomes DC power. The inverter circuit 4 includes a first half bridge circuit 41 in which power conversion semiconductor elements 4a and 4d as switching elements are connected in series, a second half bridge circuit 42 in which power conversion semiconductor elements 4b and 4e are connected in series, A semiconductor element for power conversion has a third half bridge circuit 43 in which conversion semiconductor elements 4c and 4f are connected in series, and both ends of the first to third half bridge circuits 41 to 43 are connected to the DC side of the converter 2. The motor 5 is connected to the connection portions 4a and 4d, the connection portions of the power conversion semiconductor elements 4b and 4e, and the connection portions of the power conversion semiconductor elements 4c and 4f. The inverter circuit 4 converts the DC power into AC power by high-speed switching of the power conversion semiconductor elements 4 a to 4 f and supplies the AC power to the motor 5. Further, an insulated gate drive circuit 30 as shown in FIG. 4 is provided to open and close the power conversion semiconductor elements 4a to 4f of the inverter circuit 4. In the insulated gate drive circuit 30 of FIG. 4, the command signal is input to the drive circuit 7 via the photocoupler 6, and the gate voltage commands of the power conversion semiconductor elements 4a, 4d and the like are output, and the power conversion semiconductor element 4a. , 4d are applied to the gates 4ag, 4dg as control terminals.

  By the way, an insulation type DC / DC converter is used as a control DC power supply for generating a drive voltage (drive power) to be applied to the gates 4ag and 4dg in order to open and close the power conversion semiconductor elements 4a and 4d. Has been. A typical circuit of the isolated DC / DC converter is a flyback converter 8 (FIG. 4). FIG. 5 shows a circuit of the flyback converter 8. In FIG. 5, the input DC power is input to the anode side terminal 8a and the cathode side terminal 8b. A capacitor 8g as a DC power source is connected between the terminals 8a and 8b. The winding start end 100a (circle in FIG. 1) of the first coil 101 of the primary winding 100 is connected to the cathode side terminal 8b via the semiconductor element 8h as a switch, and the winding end end 100b of the third coil 103 is connected. (● in FIG. 1) is connected to the terminal 8a on the anode side. Although the semiconductor element 8h is controlled by the control circuit 8k, power is supplied to the control circuit 8k as the second load from the terminal of the capacitor 8n in the series circuit of the diode 8m and the capacitor 8n connected to the tertiary winding 300. Supplied. On the other hand, a series circuit of a diode 8p and an output capacitor 8q is connected to the secondary winding 200, and output terminals 8c and 8d connected to the output capacitor 8q are connected to the power conversion semiconductor element via the drive circuit 7. 4a and 4d are connected to gates 4ag and 4dg (FIG. 4). The control circuit 8k is connected to the tertiary winding 300 and used as a power source.

  Next, the operation will be described. In the flyback converter 8 shown in FIG. 5, a current flows through the primary winding 100 when the semiconductor element 8 h is turned on. This current fills the core 20 of the flyback transformer 10 with magnetic flux and accumulates it as energy. During this period, no induced current flows through the secondary winding 200 and the tertiary winding 300. While the semiconductor element 8h is off, the energy stored in the core 20 is released, current flows from the secondary winding 200 through the diode 8p, and the voltage generated in the output capacitor 8q is supplied to the drive circuit 7 in FIG. Is done. The voltage generated in the tertiary winding is supplied to the control circuit 8k as another load. In this way, the flyback converter 8 is an on / off type isolated DC / DC converter that outputs during a period when the semiconductor element 8h is off. The flyback converter 8 is an isolated DC / DC converter that has a relatively simple circuit configuration and is suitable for miniaturization and cost reduction, and is widely used. While a normal transformer is intended for voltage conversion by electromagnetic induction, the flyback transformer 10 is intended to fill the core 20 with a magnetic flux generated by the current of the primary winding 100 and store energy. For this reason, the flyback transformer 10 is usually provided with an air gap G (FIG. 1) in the leg portion 20a in order to increase the magnetic flux that can be accumulated.

In such a flyback transformer 10, power conversion of the inverter circuit 4 is performed between the first coil 101 constituting the primary winding 100 shown in FIG. 1 connected to the semiconductor element 8 h and the leg portion 20 a of the core 20. A tertiary winding 300 that is not directly electrically connected to the semiconductor elements 4a to 4f is provided. Therefore, a distance can be secured between the first coil 101 of the primary winding 100 and the leg portion 20a of the core 20, and the stray capacitance can be reduced. As a result, it is possible to reduce the high-frequency noise current propagating from the first coil 101 of the primary winding 100 to the leg portion 20a of the core 20.
On the other hand, since the first coil 101 forming the primary winding 100 and the tertiary winding 300 that is not directly electrically connected to the power conversion semiconductor element of the inverter circuit 4 are close to each other, the stray capacitance is reduced. There is a possibility that the high frequency noise current becomes large. However, in this embodiment, the tertiary winding 300 is not directly electrically connected to the power conversion semiconductor elements 4a to 4f of the inverter circuit 4, and thus does not induce propagation of common-mode high-frequency leakage current. Accordingly, it is possible to prevent deterioration of the electromagnetic environment of the power conversion device including the inverter circuit 4.

  Further, in the flyback transformer 10, the winding start end 100a of the primary winding 100 connected to the semiconductor element 8h shown in FIG. 5 is arranged on the inner side, and the secondary winding 200 directly electrically connected to the power conversion semiconductor element. Is arranged outside the primary winding 100. FIG. 6 schematically shows voltage fluctuation due to switching of the semiconductor element 8h (FIG. 5) in the flyback transformer 10 as described above. In FIG. 6, the first, second, and third coils 101, 102, and 103 that constitute the primary winding 100 and the secondary winding that is directly electrically connected to the power conversion semiconductor elements 4 a to 4 f of the inverter circuit 4. The stray capacitance C12 formed between the line 200 is shown. The primary winding 100 includes first to third coils 101 to 103 constituting three coil layers having the same number of turns, and the secondary winding 200 is illustrated as an example of a single layer coil.

Here, when the DC voltage Vin applied to the primary winding 100 is controlled to be opened and closed at a high frequency by the semiconductor element 8h, the voltages of the first to third coils 101 to 103 are changed to the voltages v11 and v12 shown in FIG. , V13 and 0. At this time, a voltage of 1/3 Vin is generated in the secondary winding 200 because the turn ratio with the primary winding 100 is 3: 1. In addition, the voltage of each part is represented on the basis of the cathode side of the input DC power supply. Therefore, a high-frequency noise current J1 expressed by the following equation is generated between the third coil 103 of the primary winding 100 and the secondary winding 200.
J1 = (C12) × (dV / dt) (1)
In the above equation, C12 is a stray capacitance between the third coil 103 and the secondary winding 200, and V is a voltage fluctuation applied between the third coil 103 and the secondary winding 200.
By disposing the first coil 101 having the largest voltage fluctuation in the innermost layer and away from the secondary winding 200, the (dV / dt) term shown in the equation (1) is reduced, and therefore the generation of the high-frequency noise current J1 occurs. It is reduced.

  The high frequency noise current J1 propagates from the flyback transformer 10 through the drive circuit 7 to the power conversion semiconductor elements 4a and 4d of the inverter circuit 4 as indicated by arrows as shown in FIG. The power conversion semiconductor elements 4 a and 4 d of the inverter circuit 4 are installed on the cooling fin 48 for cooling, and the stray capacitance Cs formed between the power conversion semiconductor elements 4 a and 4 d and the cooling fin 48 propagates. The high-frequency noise current J1 flows out from the secondary winding 200 of the flyback transformer to the power conversion semiconductor elements 4a and 4d of the inverter circuit 4 to the stray capacitance Cs to the cooling fin 48 to the ground to become a common mode current. . Since the common mode current becomes a radiation noise source due to the size of the circulation loop and deteriorates the electromagnetic environment compatibility of the power converter, reduction of the common mode current is a problem to be solved in product development. According to this embodiment, since the generation of the high frequency noise current J1 is reduced, the common mode current can be reduced.

  FIG. 8 shows a high-frequency noise current generation mechanism different from that in FIG. 8, the leakage inductance L of the first to third coils 101, 102, 103 (primary winding 100), the leakage inductance L21, L22 of the secondary winding 200, and the winding start end 100a of the primary winding 100 are illustrated. And the stray capacitance C3 formed between the secondary winding 200 and the secondary winding 200. In the flyback transformer 10 of this embodiment, as shown in FIG. 8, a floating formed between the winding start end 100a of the primary winding 100 connected to the semiconductor element 8h (FIG. 5) and the secondary winding 200. Since the capacitance C3 is small, the series resonance point caused by the stray capacitance C3 and the leakage inductance L1 of the primary winding 100 or the leakage inductances L21 and L22 of the secondary winding 200 can be moved to a high frequency range. When the series resonance point moves to the high frequency range, the generated high frequency noise current also moves to the high frequency range. As the frequency is higher, the internal resistance of the inverter circuit 4 and the like increases due to the skin effect or the like, so that the amplitude of the high-frequency noise current is suppressed. That is, low noise can be realized.

In the flyback transformer 10 in this embodiment, as shown in FIG. 1, the tertiary winding 300 is installed in the innermost layer near the leg portion 20 a of the core 20. As shown in FIG. 5, leakage flux from the vicinity of the facing portions of the arms 21 a and 22 a that form the air gap G of the core 20 is linked to the tertiary winding 300. Since the capacitor 8n is connected, the capacitor 8n is substantially short-circuited, a current flows in a direction to cancel the interlinkage leakage magnetic flux, and the leakage magnetic flux is canceled. That is, the tertiary winding 300 functions as an electromagnetic shield against leakage magnetic flux. Therefore, the leakage magnetic flux interlinking with the primary winding can be reduced, and as a result, eddy current loss can be reduced. In the flyback transformer 10 according to the present invention, since the current flowing through the primary winding 100 is large, the reduction of eddy current loss in the primary winding 100 is effective because it directly leads to a reduction in the loss of the entire flyback transformer. is there. Since the distance between the leg 20a of the core 20 and the primary winding 100 is increased to reduce eddy current loss due to leakage magnetic flux from the vicinity of the air gap, the capacitor 8n is connected to the tertiary winding 300. Even if it is not, it is possible to sufficiently reduce eddy current loss. In addition, since the distance between the leg 20a of the core 20 and the primary winding 100 is increased and the tertiary winding 300 is disposed in this vacant space, it is possible to effectively use the space and increase the size of the flyback transformer. There is no risk of incurring.
According to the first embodiment, it is possible to obtain the flyback transformer 10 that simultaneously realizes low noise and low loss.

  The winding structure of the flyback transformer is not limited to that shown in FIG. For example, it may be as shown in FIG. In FIG. 9, the flyback transformer 50 includes a rectangular cylindrical quaternary winding 400 provided between the primary winding 100 and the secondary winding 200. The core 20 is the same as the core 20 of FIG. 1 except that the lengths of the yoke portions 21c and 22c in the left-right direction are longer by the length of the quaternary winding. Also in this case, the rectangular cylindrical tertiary winding 300, the primary winding 100, the quaternary winding 400, and the secondary winding 200 are concentric in this order from the inside to the outside with the leg 20a as the center. Is arranged. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted. The quaternary winding 400 is a winding that is not directly electrically connected to the power conversion semiconductor element, and is used for a power supply such as a communication device or a cooling fan as a third load.

  In this case, since the quaternary winding 400 is provided between the primary winding 100 and the secondary winding 200, the distance between the primary winding 100 and the secondary winding 200 increases, The stray capacitance between them (see the stray capacitance C12 in FIG. 6) is reduced. Therefore, the high-frequency noise current propagating from the primary winding 100 to the secondary winding 200 is also smaller than that of the flyback transformer 10 shown in FIG.

Embodiment 2. FIG.
10 and 11 show the second embodiment of the present invention, FIG. 10 is a cross-sectional view showing the configuration of the flyback transformer, and FIG. 11 is a winding diagram of the flyback transformer. In these figures, the flyback transformer 60 has a plurality of secondary windings 220, 230, and 240 as a plurality of secondary windings for power supply provided outside the primary winding 100. Secondary windings 220, 230, and 240 are used for power supply to drive circuit 7 for driving first, second, and third half bridge circuits 41, 42, and 43 of inverter circuit 4 shown in FIG. used. All of the secondary windings 220, 230, and 240 have the same shape of a rectangular cylinder, and are outside the primary winding 100 in FIG. 10 and overlap in the vertical direction that is the axial direction. Has been placed. The secondary winding 220 has a rectangular annular first coil 221, second coil 222, and third coil 223 having the same number of turns, and the three first coils 221, second coil 222, and third coil 223 are The three layers are concentrically arranged in this order from the inside to the outside. The first coil 221, the second coil 222, and the third coil 223 are connected in series to form the secondary winding 220, and the turns ratio of the primary winding 100 and the secondary winding 220 is 3 : 1.

  The secondary winding 230 includes a rectangular annular first coil 231, second coil 232, and third coil 233 having the same number of turns, and the three first coils 231, second coil 232, and third coil 233 are The three layers are concentrically arranged in this order from the inside to the outside. The first coil 231, the second coil 232, and the third coil 233 are connected in series to form the secondary winding 230, and the turns ratio of the primary winding 100 and the secondary winding 230 is 3 : 1. The secondary winding 240 has a rectangular annular first coil 241, second coil 242, and third coil 243 having the same number of turns, and the three first coils 241, second coil 242, and third coil 243 are The three layers are concentrically arranged in this order from the inside to the outside. The first coil 241, the second coil 242, and the third coil 243 are connected in series to form the secondary winding 240, and the turns ratio of the primary winding 100 and the secondary winding 240 is 3 : 1. The winding start ends of the secondary windings 220, 230, and 240 are indicated by black circles ●, and the winding end ends are indicated by white circles (◯). Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted.

In the present embodiment, the secondary windings 220, 230, and 240 that are directly electrically connected to the gates of the power conversion semiconductor elements 4a to 4f of the inverter circuit 4 are respectively wound in the height (axis) direction. Are composed of three layers of first to third coils wound in the same manner. Therefore, the facing area between the primary winding 100 and each secondary winding 220, 230, 240 (221, 231, 241) is reduced to about one third, and the stray capacitance between the windings is further reduced. Can do. In the present embodiment, C12 of the above formula (1) can be reduced as compared with the flyback transformer 10 shown in FIG. 1, and generation of high frequency noise current can be reduced. In addition, although each 1st-3rd coil which comprises each secondary winding 220,230,240 showed what was cyclic | annular, it is cyclic | annular thru | or cylindrical shape by the electric current of secondary winding, voltage, the number of turns, and other specifications. Is adopted.
According to this embodiment, it is possible to obtain a flyback transformer that simultaneously realizes low loss and low noise.

Embodiment 3 FIG.
12 and 13 show a third embodiment of the present invention, and FIG. 12 is a cross-sectional view showing a configuration of the flyback transformer, and a cross-sectional view showing a configuration of a modification of the flyback transformer of FIG. In FIG. 12, the flyback transformer 70 has three secondary windings 251, 252, and 253 as a plurality of collective winding secondary windings provided outside the primary winding 100. The secondary windings 251, 252, and 253 are used for power supply to the drive circuit 7 for driving the first, second, and third half bridge circuits 41, 42, and 43 of the inverter circuit 4 shown in FIG. used. The turn ratio between the primary winding 100 and each of the secondary windings 251, 252, 253 is 3: 1. The secondary windings 251, 252, and 253 are arranged in the axial direction (vertical direction in FIG. 12) of three conductors that are insulated from each other as three phases, and from the winding start ends 251a, 252a, and 253a (●). Winding three turns outward in the radial direction, then shifting upward by three conductors and winding again three turns from the inside to the outside, repeating these operations, each secondary winding has a predetermined number of turns (turn ratio 1 Winding is performed until the next winding: secondary winding = 3: 1), and the winding ends at the winding end ends 251b, 252b, 253b (◯). As a result, a coil in which the three secondary windings 251, 252, and 253 are wound together is formed. The winding diagram is the same as the winding diagram shown in FIG.

  Further, a flyback transformer 80 as shown in FIG. 13 may be used. The flyback transformer 80 includes three secondary windings 261, 262, and 263 for three phases as a plurality of collective winding secondary windings provided outside the primary winding 100. Secondary windings 261, 262, and 263 are used for power supply to drive circuit 7 for driving first, second, and third half bridge circuits 41, 42, and 43 of inverter circuit 4 shown in FIG. used. The turn ratio between the primary winding 100 and each of the secondary windings 261, 262, and 263 is 3: 1. The secondary windings 261, 262, and 263 are arranged such that three insulated conductors are collectively arranged in the axial direction (vertical direction in FIG. 13), and the upper ends in FIG. Wrap in a spiral shape and fold back to the second layer at the top. Fold again at the bottom of the second layer. By repeating such operations, each secondary winding is wound until the number of turns reaches a predetermined number of turns (turn ratio: primary winding: secondary winding = 3: 1), and the winding end ends 261b, 262b, 263b (◯). To finish.

In the present embodiment, the secondary windings 251, 252, 253 and the secondary windings 261, 262, 263 that are directly electrically connected to the power conversion semiconductor elements 4 a to 4 f of the inverter circuit 4 include three windings. Since it is composed of a coil layer formed by winding a minute conductor in a lump, the area facing the primary winding 100 is reduced to about one third, and the stray capacitance between the windings can be reduced. . That is, in the present embodiment, C12 in the formula (1) can be reduced, and generation of high frequency noise current can be suppressed.
According to this embodiment, it is possible to obtain a flyback transformer that simultaneously realizes low loss and low noise.

Embodiment 4 FIG.
FIG. 14 is a cross-sectional view showing the configuration of the flyback transformer according to the fourth embodiment of the present invention. In FIG. 14, the flyback transformer 90 has a primary winding 110. The primary winding 110 includes a rectangular cylindrical first coil 111, a second coil 112, a third coil 113, and a fourth coil 114 having the same number of turns as a cylindrical coil, and the four first coils 111. The second coil 112, the third coil 113, and the fourth coil 114 are arranged to form four layers concentrically in this order from the inside toward the outside. The first coil 111, the second coil 112, the third coil 113, and the fourth coil 114 are connected in series to form the primary winding 110, and the primary winding 110, the secondary winding 200, The turns ratio is 4: 1. The winding start end 110a of the primary winding 110 is indicated by a black circle ●, and the winding end end 110b as a connecting portion with the terminal 8a on the anode side of the input DC power supply is indicated by a white circle (◯). The winding start end 110a and the winding end end 110b are positioned inside the bag. The semiconductor element 8h (FIG. 5) is connected to the winding start end 110a of the primary winding 110 as a connection portion with the semiconductor element 8h. A rectangular cylindrical tertiary winding 300, a primary winding 110, and a secondary winding 200 wound around a bobbin (not shown) are concentrically arranged with the leg portion 20a as a center. The winding diagram of the flyback transformer 90 is the same as FIG.

In the present embodiment, primary winding 110 formed by a plurality of coil layers is configured by an even number of layers (four layers) of coil layers. Therefore, both the winding start end and the winding end ends 110a and 110b, which are both ends of the primary winding 110, can be positioned on one side of the bobbin (not shown) (the lower side in FIG. 14). It becomes easy to connect the drawers at both ends of 110, that is, the lead lines, and the productivity is improved.
According to the present embodiment, low loss and low noise can be realized simultaneously and productivity can be improved.

In each of the above embodiments, the core is formed of ferrite. However, other appropriate magnetic materials such as a silicon steel plate and an amorphous magnetic material may be used. The shape can also be formed in a field track shape or the like with a wound iron core instead of a frame shape. Further, the shape of each winding or coil may be circular, field track, or other shapes.
Further, in the present invention, within the scope of the invention, the above-described embodiments can be freely combined, and each embodiment can be appropriately changed or omitted.

4 inverter circuit, 4a to 4d power conversion semiconductor element, 4ag, 4dg gate,
6 Photocoupler, 7 Drive circuit, 8 Flyback converter,
8h semiconductor element, 8k control circuit, 10 flyback transformer, 20 cores,
20a Leg part, 21 1st core, 22 2nd core, 21a, 22a Arm part,
30 Insulated gate drive circuit, 41-43 1st-3rd half bridge circuit,
50, 60, 70, 80, 90 flyback transformer, 100 primary winding,
100a winding start end, 100b winding end end, 101-103 first to third coils,
110 primary winding, 110a winding start end, 110b winding end end,
111-114 1st coil-4th coil, 200 secondary winding, 220 secondary winding,
221 to 223 1st coil to 3rd coil, 230 secondary winding,
231 to 233 1st coil to 3rd coil, 240 secondary winding,
241-243 1st coil-3rd coil, 251, 252, 253 secondary winding,
261, 262, 263 secondary winding, 300 tertiary winding, 400 quaternary winding.

Claims (5)

A DC power supply having a core, a primary winding, a secondary winding, and a tertiary winding, and supplying power for driving the switching element of a power converter that converts power by driving the switching element to open and close A flyback transformer used in the apparatus,
The core has a leg portion, and the leg portion has an air gap forming portion that forms an air gap.
The primary winding has a plurality of cylindrical coils arranged so as to form a plurality of layers, and the plurality of cylindrical coils are connected in series.
The secondary winding is formed in a cylindrical or annular shape,
The tertiary winding is formed in a cylindrical shape,
Surrounding the legs, the tertiary winding, the primary winding, and the secondary winding are arranged in multiple layers in this order,
The cylindrical coil of the innermost layer of the cylindrical coils of the primary winding is connected to one pole of a DC power source through a switch, and the outermost layer of the cylindrical coils of the primary winding is A cylindrical coil is connected to the other pole of the DC power source,
By opening and closing the switch, the power generated in the secondary winding is supplied to the switching element of the power converter as driving power, and the power generated in the tertiary winding is different from the switching element. A flyback transformer that is supplied to a load of 2. The secondary winding has a plurality of secondary windings for supplying power,
Each of the secondary windings for power supply has a plurality of cylindrical or annular coils arranged in a plurality of layers, and the plurality of cylindrical or annular coils are connected in series. ,
2. The fly according to claim 1, wherein the plurality of secondary windings for power supply are arranged so as to face the primary winding and overlap each other in the axial direction of the primary winding. Back transformer. 2. The flyback transformer according to claim 1, wherein the secondary winding is formed by winding a plurality of conductors insulated from each other in a cylindrical shape. A cylindrical quaternary winding is provided,
The quaternary winding is provided between the primary winding and the secondary winding, and is connected to a third load different from the switching element and the second load. The flyback transformer according to any one of claims 1 to 3. The primary winding has an even number of cylindrical coils,
The even-numbered cylindrical coil is wound around a bobbin with a hook in multiple layers, and the winding start and end of the primary winding are both located on one side of the hook of the bobbin. The flyback transformer according to any one of claims 1 to 4.

Images