JP3647913B2 - High frequency switching transformer - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a switching power supply, and more particularly to a high-frequency switching transformer used for a low voltage and large current output.
[0002]
[Prior art]
For a power source for large computers, communication devices, electromagnetic coils, etc., a DC power supply device with a low voltage and a large current is required. Conventionally, series power supplies that use commercial frequency transformers to reduce the commercial voltage and perform constant voltage control using thyristors or transistors have been used for these power supplies. Accounted for. Therefore, in recent years, switching power supplies that do not use commercial frequency transformers have become widespread due to demands for miniaturization and weight reduction.
[0003]
Conventionally, a switching transformer used in this type of switching power supply generally uses a tripod core 10 as shown in FIG. 7, for example, and a primary coil 9 is wound around the middle leg 10a, and as shown in the sectional view of FIG. In order to improve the coupling, a secondary coil 11 wound around an insulating tape 13 is used. The tripod core 10 has a rectangular parallelepiped block made of a magnetic material provided with rectangular holes on the left and right sides, the two rectangular holes serving as window portions 12, and the portion sandwiched between the window portions 12 is a middle leg 10a. It is what.
[0004]
As the core material, ferrite or the like with low iron loss at high frequency is used, and the output current often reaches several hundred amperes, and the large core 10 having a large window area is required. On the other hand, in order to suppress an increase in AC resistance due to the skin effect, a litz wire, a thin copper plate, or a copper square is used for the coil wire. When forming a coil with these copper plates etc., since a raw material is thick and hard, an electric wire winding device etc. cannot be used and it has to rely on manual work, but work is difficult and requires skill.
[0005]
Also, because the output is low voltage and high current, the turns ratio is large and the leakage inductance is inevitably large. However, this leakage inductance may cause surge voltage in switching devices and diodes, which may damage these devices. There is. Therefore, a snubber circuit is used to suppress the surge voltage.
[0006]
[Problems to be solved by the invention]
In the conventional power supply device, the larger core 10 is used as the output capacity increases. However, the price of the ferrite core increases exponentially with respect to the weight (volume), and thus is expensive. . Furthermore, a cost is high such as a labor cost when a coil is formed by using a litz wire, a copper plate or the like when a litz wire is used as the coil material, and a simple manufacturing method using an inexpensive material has been desired.
[0007]
The power loss consumed by the snubber circuit that suppresses the surge voltage corresponds to the energy stored in the leakage inductance, and can be expressed by the following equation, where L is the leakage inductance and I is the current.
(1/2) LI ²
As indicated by the above equation, the energy stored in the leakage inductance increases in proportion to the square of the current, and there is a problem that the surge voltage countermeasure becomes more difficult as the output capacity increases.
[0008]
The present invention has been made in view of such points, the purpose of which is that the cost of manufacturing a coil is low, can be easily manufactured with an inexpensive material, and without increasing the snubber loss, An object of the present invention is to provide a high-frequency switching transformer that can easily prevent surge voltage.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention achieves N (N is 2 or more) cores 2a, 2b to 2n, 6a, 6b to 6n having at least one window, and the cores 2a, 2b to 2n, 6a, 6b-6n primary coils 1a, 1b-1n, 5a, 5b-5n wound over one turn so as to pass through the windows, and all the cores 2a, 2b-2n, 6a, 6b Secondary coils 3, 7 penetrating through the 6n window portions 4a, 4b-4n, 8a, 8b-8n, and the N pieces so that the window portions of the cores face each other. The core is arranged.
[0010]
Further, each of the core 2a, 2B～2n, 6a, each core 2a such that the magnetic path of the 6B～6n is substantially parallel, 2B～2n, 6a, and sideways 6B～6n, and their respective window portions 4a, 4b to 4n, 8a, has a configuration in which 8b~8n is arranged to form a space for inserting the secondary coil 3 and 7 communicate with each other.
[0011]
Furthermore, the driving method of the high frequency switching transformer according to claim 1 or 2, wherein each of the primary coils 1a, 1b to 1n, 5a, 5b to 5n has a constant or arbitrary phase difference. The excitation drive is used.
[0012]
[Action]
When a plurality of primary coils 1a, 1b to 1n, 5a, 5b to 5n are excited by the switching circuit, the primary coils 1a, 1b to 1n, An induced voltage corresponding to the number of turns 5a and 5b to 5n and the applied voltage is generated, and the total voltage appears at both ends of the secondary coil. Therefore, when the high-frequency switching transformer is composed of N cores 2a, 2b to 2n, 6a, 6b to 6n and primary coils 1a, 1b to 1n, 5a, 5b to 5n, the individual primary coils 1a, The currents 1b to 1n, 5a, and 5b to 5n are 1 / N when the number of the cores and the primary coil is one, and it is possible to use an inexpensive small-sized core that is mass-produced.
[0013]
Also, the cores 2a, 2b to 2n, 6a, 6b to 6n are turned sideways so that the magnetic paths of the cores 2a, 2b to 2n, 6a, 6b to 6n are substantially parallel, and the windows 4a, 4b to 4n Since 4n, 8a, 8b to 8n communicate with each other to form a space through which the secondary coils 3 and 7 are inserted, the secondary coils 3 and 7 are connected to the cores 2a, 2b to 2n, 6a, 6b to 6n. The work of penetrating the windows 4a, 4b to 4n, 8a, 8b to 8n is simple.
[0014]
Further, since each primary coil N1 of the high-frequency switching transformer configured as described above is excited and driven with a constant or arbitrary phase difference, the effective input current is reduced and generated on the secondary side. Since the instantaneous value of the voltage is also reduced, the withstand voltage of the secondary diodes D1 and D2 is small, and the secondary frequency is increased, so that the choke coil L1 and the capacitor C can be reduced in size.
[0015]
【Example】
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing an embodiment using a toroidal core.
In the figure, 1a, 1b-1n are primary coils, 2a, 2b-2n are cores, and here a toroidal core is used. Reference numeral 3 denotes a secondary coil, and 4a and 4b to 4n denote window portions corresponding to the hollow portions of the cores 2a and 2b to 2n.
[0016]
Thus, primary coils 1a and 1b to 1n are wound around the plurality of cores 2a and 2b to 2n, respectively. The cores 2a, 2b to 2n are so-called toroidal cores, and are formed in a so-called donut shape having a hollow cylindrical shape.
[0017]
The plurality of cores 2a, 2b-2n around which the primary coils 1a, 1b-1n are wound are laterally oriented so that the magnetic paths thereof are substantially parallel so that the central axes of the cylinders of the cores 2a, 2b-2n coincide. In series, that is, the windows 4a, 4b to 4n are arranged to communicate with each other to form one cylindrical space, and the secondary coil 3 is passed through the windows 4a, 4b to 4n.
[0018]
In the high-frequency switching transformer having such a configuration, a current is supplied to each primary coil 1a, 1b to 1n wound around each core 2a, 2b to 2n from a switching circuit as described later, for example. , 1b to 1n are excited, an induced voltage is generated in the secondary coil 3 according to the number of turns of the primary coils 1a and 1b to 1n and the applied voltage, and the voltage across the secondary coil 3 is the sum of the voltages. As a result, it operates as a transformer equivalent to a large transformer having the ability of the sum of the induced voltages from the cores 2a, 2b to 2n.
[0019]
Next, another embodiment of the present invention will be described. FIG. 2 is a view showing a case where a tripod core is used as another embodiment of the present invention.
In the figure, 5a, 5b to 5n are primary coils, 6a, 6b to 6n are cores, and a three-legged core is used here. Reference numeral 7 denotes a secondary coil formed of a copper plate, and 8a and 8b to 8n denote window portions formed on both sides of the middle legs of the tripod cores 6a and 6b to 6n.
[0020]
Thus, primary coils 5a, 5b-5n are wound around the middle legs of the plurality of cores 6a, 6b-6n. The cores 6a, 6b to 6n are so-called tripod cores, and a substantially rectangular rectangular hole is provided in a block made of a substantially rectangular magnetic material on both sides, and a portion sandwiched between the two rectangular holes is formed. It is a leg.
[0021]
The plurality of cores 6a, 6b-6n around which the primary coils 5a, 5b-5n are wound are turned sideways in the same manner as in the above embodiment, and the surfaces of the outer frames of the cores 6a, 6b-6n are coincident. In this way, the windows 8a, 8b to 8n are arranged to communicate with each other to form one square hole-like space, and the windows 8a, 8b to 8n are made of a copper plate. The coil 7 is penetrated.
[0022]
Also in the high-frequency switching transformer having such a configuration, when the primary coils 5a and 5b to 5n are excited by the switching circuit as in the above embodiment, the number of turns of the primary coils 5a and 5b to 5n and An induced voltage corresponding to the applied voltage is generated, and the voltage across the secondary coil 7 is the sum of the voltages.
[0023]
In the above two embodiments, when the high-frequency switching transformer is composed of N cores 2a, 2b to 2n, 6a, 6b to 6n and primary coils 1a, 1b to 1n, 5a, 5b to 5n, The current of the primary coils 1a, 1b to 1n, 5a, 5b to 5n becomes 1 / N when the number of the core and the primary coil is one, and it becomes possible to use an inexpensive and small-sized core for mass production. As the wire, a round wire that can be easily wound can be used, and the secondary coil simply allows a conductor such as a copper plate to pass through each of the communicating windows 8a, 8b to 8n, thereby reducing the labor cost and material cost.
[0024]
The secondary coils 3 and 7 are only in contact with the primary coils 1a, 1b to 1n, 5a, 5b to 5n, and are in close contact with the primary coils 1a, 1b to 1n, 5a, 5b to 5n. However, since the secondary coils 3 and 7 are not covered, the primary coils 1a, 1b to 1n, 5a, and 5b to 5n also have better heat dissipation, heat generation is suppressed, and reliability is improved.
[0025]
In addition, the energy stored in the leakage inductance is considered to be substantially equal to the leakage inductance of each coil of the high-frequency switching transformer according to the present invention when configured with one core, and in the case of the high-frequency switching transformer according to the present invention, ( 1/2) L (I / N) ² N
As a result, the snubber loss is reduced to 1 / N 2 and miniaturization and high efficiency are possible.
[0026]
Furthermore, the switching transformer is generally designed each time according to the rated output voltage and current. According to the present invention, the primary coils 1a, 1b to 1n, 5a for the cores 2a, 2b to 2n, 6a, 6b to 6n1 are provided. , 5b to 5n, the output voltage can be set according to the number of cores 2a, 2b to 2n, 6a, 6b to 6n, and the output current can be set according to the cross-sectional area of the wires of the secondary coils 3 and 7. This is possible and facilitates transformer design. Since a common material can be used, the cost can be reduced.
[0027]
Next, a method for driving the high-frequency switching transformer will be described with reference to FIGS.
FIG. 3 is a diagram showing an example of a circuit for driving the high-frequency switching transformer according to the present invention.
[0028]
In the figure, 20 is a high-frequency switching transformer according to the present invention, E is a power source, SW is a switch element, and is shown as a mechanical contact in the figure, but in reality, a high-speed switching element such as a transistor, MOSFET, IGBT or the like is used. The B1, B2 to Bn correspond to 2a, 2b to 2n, 6a, 6b to 6n in the above-described embodiments in each core. N1 is a primary coil corresponding to 1a, 1b to 1n, 5a, 5b to 5n of the above embodiment, and N2 is a secondary coil corresponding to 3 and 7 of the above embodiment. D1 and D2 are secondary side diodes, D1 functions as a rectifier diode, and D2 functions as a flywheel diode. L1 is a choke coil and C is a capacitor.
[0029]
In this circuit, the power source E and the primary coil N1 of each of the cores B1, B2 to Bn are connected in parallel via one switch element SW, and the secondary coil N2 of each of the cores B1, B2 to Bn is respectively Connected in series, one end is connected to the anode of the secondary diode D1, its cathode is connected to the cathode of the secondary diode D2 and one end of the choke coil L1, and the other end is connected to one end of the capacitor C and the output terminal. It is connected. The other end of the secondary coil N2 is connected to the anode of the secondary diode D2, the other end of the capacitor C, and the other end of the output terminal.
[0030]
In the circuit having such a configuration, when the switch element SW is turned on / off at a constant cycle, the primary coil N1 connected in parallel is simultaneously excited, and the secondary coil N2 is applied with the number of turns of the primary coil N1 and the applied voltage. Inductive voltage is generated at the same time, and the voltage across the secondary coil N2 shows the sum of the voltages. As a result, a large transformer having the ability of the sum of the induced voltages from the cores B1, B2 to Bn Operates as an equivalent transformer. Then, only the forward component is extracted by the secondary diodes D1 and D2, and then smoothed by the choke coil L1 and the capacitor C, and output as a DC power source having a predetermined voltage and current value.
[0031]
FIG. 4 is a diagram showing another example of a circuit for driving the high-frequency switching transformer according to the present invention. In this circuit, the power source E and the primary coils N1 of the respective cores B1, B2 to Bn are connected via switching elements SW1, SW2 to SWn corresponding to the primary coils N1 of the respective B1, B2 to Bn, Other configurations are the same as those of the circuit of FIG. 3, and the same components are denoted by the same reference numerals and description thereof is omitted.
[0032]
FIG. 5 shows a method for driving the high-frequency switching transformer 20 in the circuit having such a configuration. (A) shows the case where each switch element SW1, SW2 to SWn is driven with the same pulse, and the operation is the same as the circuit of FIG. 3 after all.
[0033]
(B) is a case where each switch element SW1, SW2-SWn is driven by a plurality of pulses having a phase difference, that is, n switch elements SW1, SW2-SWn are driven by a pulse having a phase difference of 360 ° / n. Is shown.
[0034]
The pulse having a phase difference can be easily generated by using known means such as a frequency divider using a combination of a crystal oscillator and a flip-flop, a monostable multivibrator, and other programmable timers. .
[0035]
When the high frequency switching transformer 20 is driven by this method, the primary coils N1 of the cores B1, B2 to Bn are sequentially excited with a phase difference of 360 ° / n, and the current supplied from the power source E is Since the averaged input current of the high-frequency switching transformer 20 is reduced compared to the method (a) and the ripple of the power supply E is reduced, the capacitor of the power supply E can be made smaller. Further, since the excitation voltage is sequentially generated in the secondary coil N2, the instantaneous value of the secondary side voltage is reduced, and the withstand voltage of the secondary side diodes D1 and D2 can be reduced. Further, as a result, the frequency of the voltage generated on the secondary side is higher than that on the primary side, so that the choke coil L1 and the capacitor C can be small.
[0036]
In actual use, for example, a reset coil N3 as shown in FIG. 6 is provided, one end of which is connected to the primary coil N1, and the other end is reversely connected to the primary coil via a backflow prevention diode D3. By using a circuit connected to the power supply E side from the switch element SW on the other end side of N1, the back electromotive force of the primary coil N1 is suppressed and the switching noise is reduced, so that the effect of the present invention is further enhanced. It is effective to enhance. The circuit shown in FIG. 6 shows an application example of the circuit of FIG. 3, but it goes without saying that the circuit of FIG. 4 can be similarly applied.
[0037]
Further, by driving with a phase difference in this way, AC output is possible, and it can be applied to an inverter.
[0038]
【The invention's effect】
As described above, according to the present invention, a plurality of cores wound with one or more turns of the primary coil are disposed, and the secondary coils are formed so as to penetrate through the windows of all the cores.
(1) The current of each primary coil is 1 / N when there is only one core and one primary coil, making it possible to use a small, inexpensive mass-produced core and using a round wire that is easy to wind the wire. Because it can be done, both labor and material costs can be reduced.
(2) Since the secondary coil is only partly in contact with the primary coil and does not adhere to and cover the primary coil, both the secondary coil and the primary coil can dissipate heat and heat generation is suppressed. Reliability is improved.
(3) The leakage inductance energy of the high-frequency switching transformer according to the present invention is (1/2) L (I / N) ² N
As a result, the snubber loss is reduced to 1 / N 2 and miniaturization and high efficiency are possible.
(4) If the specification of the primary coil for one core is determined, it is possible to set the output voltage according to the number of cores and the output current according to the cross-sectional area of the wire material of the secondary coil.
Transformer design becomes easy and cost can be reduced because common materials can be used.
[0039]
Also, because each core is placed sideways so that the magnetic paths of each core are substantially parallel, and the windows are connected to form a space through which the secondary coil is inserted,
Since the work of penetrating the secondary coil through the window portion of each core is simple, the production efficiency is improved.
[0040]
Further, since each primary coil of the high-frequency switching transformer configured as described above is excited and driven with a constant or arbitrary phase difference, the input effective current is reduced and the voltage generated on the secondary side is reduced. Since the instantaneous value of the secondary diode becomes low, the withstand voltage of the secondary diode can be reduced, and the secondary frequency increases, so that the choke coil and the capacitor can be downsized.
It has the effect.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention using a toroidal core.
FIG. 2 is a configuration diagram showing another embodiment of the present invention when a tripod core is used.
FIG. 3 is a diagram showing an example of a circuit for driving a high-frequency switching transformer according to the present invention.
FIG. 4 is a diagram showing another example of a circuit for driving a high-frequency switching transformer according to the present invention.
5A and 5B are diagrams illustrating a method of driving the circuit of FIG. 4, in which FIG. 5A illustrates a case where the same pulse is driven simultaneously, and FIG. 5B illustrates a case where the circuit is driven using a pulse having a phase difference.
6 shows a case where a reset coil is provided as an application example of the circuit of FIG.
FIG. 7 is a diagram showing a configuration of a conventional transformer.
8 is a cross-sectional view of the transformer of FIG.
[Explanation of symbols]
1a, 1b to 1n Primary coil 2a, 2b to 2n Core 3 Secondary coil 4a, 4b to 4n Window part 5a, 5b to 5n Primary coil 6a, 6b to 6n Core 7 Secondary coil 8a, 8b to 8n Window part 9 Primary coil 10 Core 10a Middle leg 11 Secondary coil 12 Window 13 Insulating tape 20, 20a High frequency switching transformer SW Switch elements SW1, SW2-SWn Switch elements B1, B2-Bn Core N1 Primary coil N2 Secondary coil N3 Reset coil E Power supply

Claims (3)

N (N is 2 or more) cores (2a, 2b to 2n, 6a, 6b to 6n) in which at least one window is opened,
A primary coil (1a, 1b to 1n, 5a, 5b to 5n) wound more than one turn so as to pass through the window of each of the cores (2a, 2b to 2n, 6a, 6b to 6n);
Secondary coils (3, 7) formed through the windows (4a, 4b-4n, 8a, 8b-8n) of all the cores (2a, 2b-2n, 6a, 6b-6n) Have
The high frequency switching transformer , wherein the N cores are arranged so that the window portions of the cores face each other . Wherein each core (2a, 2b~2n, 6a, 6b~6n ) each core so that the magnetic path is substantially parallel to (2a, 2b~2n, 6a, 6b~6n ) was sideways, and each of its windows ( 4. The high frequency switching transformer according to claim 1, wherein 4 a, 4 b to 4 n, 8 a, 8 b to 8 n) communicate with each other to form a space for inserting the secondary coil (3, 7). A method for driving a high-frequency switching transformer according to claim 1 or 2,
A driving method of a high-frequency switching transformer, wherein each of the primary coils ( 1a, 1b to 1n, 5a, 5b to 5n ) is excited and driven with a constant or arbitrary phase difference.

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