WO2019117241A1 - Isolated switching power supply - Google Patents

Isolated switching power supply Download PDF

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Publication number
WO2019117241A1
WO2019117241A1 PCT/JP2018/045851 JP2018045851W WO2019117241A1 WO 2019117241 A1 WO2019117241 A1 WO 2019117241A1 JP 2018045851 W JP2018045851 W JP 2018045851W WO 2019117241 A1 WO2019117241 A1 WO 2019117241A1
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Prior art keywords
transformer
secondary coil
current
primary coil
coil
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PCT/JP2018/045851
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French (fr)
Japanese (ja)
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羽田　正二
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Ntn株式会社
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Priority to KR1020207016745A priority Critical patent/KR102640341B1/en
Publication of WO2019117241A1 publication Critical patent/WO2019117241A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Definitions

  • the present invention relates to a flyback-type isolated switching power supply capable of suppressing a surge voltage.
  • the high back electromotive force in the present specification, “electromotive force” and “back electromotive force” are used in the sense of voltage) in the primary coil of the transformer at the moment when the switching element is turned off A surge voltage is generated and applied to the switching element. For this reason, it has been necessary to use a high withstand voltage switching element or to provide a snubber circuit or the like for processing a back electromotive force.
  • the first aspect of the isolated switching power supply of the present invention which achieves the above object is as follows.
  • A a first transformer comprising a primary coil and a secondary coil;
  • B a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal;
  • C A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point The second transformer connected in parallel, the second connection point being one end of the secondary coil of the second transformer and also the first output end;
  • D a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction;
  • E a second rectifying element connected to conduct a current flowing from the second output end to the other end of the secondary coil of the second transformer and to block a current in the opposite direction;
  • the second aspect of the isolated switching power supply of the present invention is as
  • A a first transformer comprising a primary coil and a secondary coil
  • B a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal
  • C A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point Connected in parallel by the second transformer, the second connection point being a first output end
  • D an inductor connected between one end of the secondary coil of the second transformer and the first output end
  • E a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction
  • F a second rectifying element connected so as to conduct current flowing from the second output end to the other end of the secondary coil of the second transformer and block current flowing in the opposite direction
  • G having a third rectifying element connected to conduct current flowing from the second output end to one end of the secondary coil of the second
  • the present invention in an isolated switching power supply, it is possible to suppress the back electromotive force generated in the primary coil of the transformer when the switching element is off, that is, the surge voltage, and reduce the withstand voltage required for the switching element.
  • FIG. 1 is a diagram schematically showing a circuit configuration example of a first embodiment of the isolated switching power supply of the present invention.
  • FIGS. 2 (a) and 2 (b) schematically show the flow of current in the on period and the off period in the circuit of FIG. 1, respectively.
  • 3 (a) and 3 (b) are diagrams schematically showing an example of the potential relationship on the transformer secondary side of the on period and the off period in the circuit of FIG. 1, respectively.
  • FIG. 4 is a view schematically showing a circuit configuration example of a second embodiment of the isolated switching power supply of the present invention.
  • 5 (a) and 5 (b) are diagrams schematically showing the flow of current in the on period and the off period in the circuit of FIG. 4, respectively.
  • 6 (a) and 6 (b) are diagrams schematically showing an example of the potential relationship on the transformer secondary side of the on period and the off period in the circuit of FIG. 4, respectively.
  • the isolated switching power supply of the present invention will be described by way of an example of a DC / DC converter to which a DC voltage is input.
  • the isolated switching power supply according to the present invention functions similarly even if a voltage of any waveform is inputted, such as a pulsating current or a rectangular wave whose voltage fluctuates, or an alternating current other than a direct current having a constant voltage. It is a power converter capable of outputting a voltage.
  • FIG. 1 is a view schematically showing a circuit configuration example of a first embodiment of the isolated switching power supply of the present invention. is there.
  • This circuit is an isolated switching power supply in which the input side and the output side are electrically isolated by a transformer, and is based on a flyback method.
  • This switching power supply has a first transformer T1 and a second transformer T2.
  • the primary side and the secondary side are isolated by the transformer T1.
  • the transformer T1 includes a primary coil 1Np and a secondary coil 1Ns.
  • the transformer T2 includes a primary coil 2Np and a secondary coil 2Ns.
  • the polarities of the primary coil and the secondary coil are opposite to each other, and are the same as a general flyback type transformer. It is preferable that both the transformer T1 and the transformer T2 have the coupling degree as high as possible, that is, the primary coil and the secondary coil be closely coupled.
  • the winding start end of each coil is shown by a black circle.
  • the coil corresponds to the “roll start end” and the “roll end”
  • the coil end corresponds to the "roll end” and the “roll start end”, respectively.
  • the winding start end is referred to as one end, and the winding end is referred to as the other end.
  • An input voltage is applied between a pair of terminals consisting of a first input 1 and a second input 2.
  • One end of the primary coil 1 Np of the transformer T 1 is connected to the input end 1.
  • the input end 2 is the input side reference potential end.
  • the switching element Q is connected in series to the primary coil 1Np of the transformer T1.
  • the switching element Q is connected between the primary coil 1 Np and the input terminal 2.
  • the switching element Q has a control end, and the control end is on / off controlled to conduct or interrupt the current path including the primary coil 1Np.
  • the control end of the switching element Q is controlled by a control signal Vg.
  • the control signal Vg is, for example, a PWM signal having a pulse waveform of a predetermined frequency and a duty ratio.
  • the switching element Q is an n-channel MOSFET (hereinafter referred to as "FET Q"), one end is a drain, the other end is a source, and the control end is a gate.
  • FET Q n-channel MOSFET
  • the control signal Vg is a voltage signal.
  • an IGBT or a bipolar transistor can be used as a switching element other than the FET.
  • a positive output end p which is a first output end and a negative output end n which is a second output end are provided on the secondary side of the transformer T1.
  • a DC voltage is output between the positive electrode output end p and the negative electrode output end n.
  • the negative electrode output end n is the secondary side reference potential end.
  • An output voltage is applied to a load (not shown) connected between the positive electrode output end p and the negative electrode output end n, and an output current is supplied.
  • the primary coil 2Np of the transformer T2 is connected in parallel to the secondary coil 1Ns of the transformer T1.
  • one end of the secondary coil 1Ns of the transformer T1 and one end of the primary coil 2Np of the transformer T2 are connected at the first connection point a
  • the secondary coil of the transformer T1 is connected at the second connection point b.
  • the other end of 1 Ns is connected to the other end of the primary coil 2 Np of the transformer T2.
  • connection point b is also one end of the secondary coil 2Ns of the transformer T2, and the second connection point b is also the positive electrode output end p.
  • a first rectifying element D1 is connected between the first connection point a and the negative output end n.
  • the rectifying element D1 is connected so as to conduct the current flowing from the negative electrode output end n to the first connection point a and to cut off the current in the opposite direction. Therefore, when the rectifying element D1 is a diode, the diode D1 has an anode connected to the negative output terminal n and a cathode connected to the first connection point a.
  • a second rectifying element D2 is connected between the other end of the secondary coil 2Ns of the transformer T2 and the negative output end n.
  • the rectifying element D2 is connected so as to conduct current flowing from the negative electrode output end n to the other end of the secondary coil 2Ns and to cut off current in the opposite direction. Therefore, when the rectifying element D2 is, for example, a diode, the diode D2 has an anode connected to the negative output terminal n and a cathode connected to the other end of the secondary coil 2Ns.
  • the rectifying element such as a diode in this circuit preferably has a small forward voltage drop and operates at high speed.
  • straightening elements other than a diode the other element or circuit which has an equivalent rectification function can be used (the same may be said of each rectification
  • a smoothing capacitor C is connected between the positive electrode output end p and the negative electrode output end n.
  • control unit that generates a control signal Vg for the switching element Q.
  • the control unit detects an input voltage and / or an output voltage, determines a duty ratio of the control signal Vg based on the detected voltage, and generates a control signal Vg of a predetermined high frequency pulse based thereon.
  • a PWM IC can be used as a main part of such a control unit (the same applies to the following embodiments).
  • FIGS. 2 (a) and 2 (b) schematically show the flow of current during on and off periods, respectively (arrows indicate the direction of the current).
  • FIGS. 3A and 3B are diagrams schematically showing an example of the potential relationship between components on the secondary side of the transformer T1 in the on period and the off period, respectively.
  • the vertical direction corresponds to the level of the potential
  • the secondary side reference potential (the potential of the negative electrode output end n) is indicated by a thick line.
  • Voltages at both ends of the secondary coil 1Ns of the transformer T1, the primary coil 2Np and the secondary coil 2Ns of the transformer T2, and the capacitor C are indicated by double arrows.
  • the winding start end side is shown as a black circle (the same may be said of the electrical potential relationship figure of other embodiment).
  • the transformer T1 is excited by the flow of the current i1 through the primary coil 1Np, and predetermined magnetic energy is accumulated in the on period.
  • the voltage across the primary coil 2Np of the transformer T2 has the same magnitude as the electromotive force generated in the secondary coil 1Ns of the transformer T1.
  • the diode D2 conducts because it is forward biased, and the current i3 flows in the following path.
  • Current i3 negative electrode output terminal n ⁇ diode D2 ⁇ secondary coil 2Ns of transformer T2 ⁇ positive electrode output terminal p
  • the transformer T2 also has an effect of suppressing an inrush current to the capacitor C at the time of circuit start-up, like the external inductor in the forward system.
  • the transformer T2 is excited by the current i2 flowing through the primary coil 2Np and stores magnetic energy, and at the same time the current i3 flows through the secondary coil 2Ns by mutual induction and power is transferred.
  • the magnetic energy stored in the transformer T1 is smaller than that of the normal flyback system.
  • the reduced magnetic energy is transferred to the transformer T2.
  • the energy transferred to the transformer T2 is larger than the magnetic energy stored in the transformer T1.
  • the energy transferred to the transformer T2 becomes the magnetic energy stored in the transformer T2 and the output power (current i3) from the transformer T2.
  • this circuit is based on the flyback method, it can be said that it is similar to a forward type power supply that allows the external inductor to store magnetic energy and output power during the on period.
  • the inductance, the turns ratio, the number of turns, and the like of each of the coils of the transformers T1 and T2 it is possible to realize the transfer of larger energy by the transformer T2 during the on period.
  • the provision of the transformer T2 in this circuit reduces the amount of magnetic energy stored in the transformer T1 during the on period as compared to a normal flyback type power supply.
  • the back electromotive force or surge voltage generated in the primary coil 1Np also decreases.
  • a voltage obtained by adding an input voltage and a back electromotive force generated in the primary coil 1Np is applied to the switching element Q (between the drain and the source in the case of an FET). Therefore, in the present circuit, the withstand voltage required for the switching element Q is reduced, and the processing capacity of the snubber circuit can be reduced. Similarly, since the possibility of magnetic saturation of the transformer T1 is also reduced, the size of the transformer T1 can be reduced.
  • the magnetic energy stored in the on period in the transformer T2 is output as power in the off period. Further, when the current i5 flows, the magnetic energy accumulated in the on period in the transformer T1 is output as the power in the off period. In the preferred design, the magnetic energy stored in the transformer T1 is smaller than the magnetic energy stored in the transformer T2, so the current i5 is smaller than the current i4.
  • FIG. 4 is a diagram schematically showing a circuit configuration example of the second embodiment.
  • FIGS. 5 (a) and 5 (b) schematically show the flow of current during on and off periods, respectively.
  • two flyback transformers T1 and T2 are used.
  • the configuration of the primary side of the transformer T1 is the same as that of the first embodiment.
  • the inductor L is connected between one end of the secondary coil 2Ns of the transformer T2 and the second connection point b, that is, the positive electrode output end p.
  • a third rectifying element D3 is connected between one end of the secondary coil 2Ns of the transformer T2 and the negative output end n.
  • the rectifying element D3 is connected so as to conduct current flowing from the negative electrode output end n to one end of the secondary coil 2Ns, and to cut off current in the opposite direction. Therefore, when the rectifying element D3 is, for example, a diode, the diode D3 has an anode connected to the negative output terminal n and a cathode connected to one end of the secondary coil 2Ns.
  • FIGS. 5 (a) and 5 (b) schematically show the flow of current during on and off periods, respectively (arrows indicate the direction of the current).
  • FIGS. 6A and 6B are diagrams schematically showing an example of the potential relationship between components on the secondary side of the transformer T1 in the on period and the off period, respectively.
  • the transformer T2 in the on period is excited by the current i2 flowing through the primary coil 2Np and stores magnetic energy, and at the same time, the current i3 flows through the secondary coil 2Ns by mutual induction and the power transfer is also performed. It will be.
  • the inductor L is excited by the flow of the current i3 to accumulate magnetic energy, like the inductor in the normal forward system.
  • the inductor L also plays a role of suppressing inrush current to the capacitor C at the start of the circuit.
  • the diode D3 is cut off because it is reverse biased.
  • the other on-period operations are the same as in the first embodiment.
  • the flow of current during the on period in the second embodiment is the same as in the first embodiment. Also in the second embodiment, it is preferable to make the energy transferred to the transformer T2 and the inductor L larger than the magnetic energy stored in the transformer T1.
  • the magnetic energy stored in the on period in the transformer T2 is output as power in the off period. Further, when the current i5 flows, the magnetic energy accumulated in the on period in the transformer T1 is output as the power in the off period.
  • the diode D3 is forward biased and becomes conductive, and the current i6 flows in the following path as shown in FIG. 5 (b).
  • ⁇ Current i6 negative electrode output terminal n ⁇ diode D3 ⁇ inductor L ⁇ positive electrode output terminal p
  • the second embodiment there are more current paths during the off period than in the first embodiment. By distributing the current, the processing capacity required for each component is reduced, and as a result, the output can be increased.

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Abstract

The present invention suppresses counter electromotive force generated in a primary coil of a transformer when a switching element is off in a flyback isolated switching power supply. This isolated switching power supply comprises: a first transformer; a switching element that is series-connected to a primary coil of the first transformer and on/off controlled by a control signal; a second transformer that is provided with a primary coil parallel-connected to a secondary coil of the first transformer by a first connection point and a second connection point, the second connection point being one end of a secondary coil of the second transformer and being a first output end; a first rectification element that is connected so as to conduct an electric current flowing from a second output end to the first connection point and interrupt an electric current flowing in the opposite direction thereof; a second rectification element that is connected so as to conduct an electric current flowing from the second output end to the other end of the secondary coil of the second transformer and interrupt an electric current flowing in the opposite direction thereof; and a capacitor between the first and second output ends.

Description

絶縁型スイッチング電源Isolated switching power supply
　本発明は、サージ電圧を抑制することができるフライバック方式の絶縁型スイッチング電源に関する。 The present invention relates to a flyback-type isolated switching power supply capable of suppressing a surge voltage.
　トランスを用いて入力側と出力側を絶縁する絶縁型スイッチング電源が知られている。入力が交流電圧の場合は、一般的には、ＡＣ／ＤＣ変換回路の後にＤＣ／ＤＣコンバータが配置されている（特許文献１～５）。入力が直流電圧の場合は、直接ＤＣ／ＤＣコンバータに入力される。スイッチング電源の代表的方式として、フライバック方式とフォワード方式がある。 There is known an isolated switching power supply in which a transformer is used to isolate the input side from the output side. When the input is an alternating voltage, generally, a DC / DC converter is disposed after the AC / DC conversion circuit (Patent Documents 1 to 5). When the input is a DC voltage, it is directly input to the DC / DC converter. There are a flyback method and a forward method as typical methods of the switching power supply.
　フライバック方式のスイッチング電源では、スイッチング素子のオン期間にフライバック用トランスの一次コイルに電流が流れるが、トランスの二次コイルに接続されたダイオードがオフであるために二次側には電流が流れず、トランスに磁気エネルギーが蓄積される。スイッチング素子のオフ期間には、トランスに蓄積された磁気エネルギーがダイオードを通じて二次側に電力として出力される。 In a flyback type switching power supply, current flows to the primary coil of the flyback transformer during the on period of the switching element, but current flows to the secondary side because the diode connected to the secondary coil of the transformer is off. It does not flow and magnetic energy is stored in the transformer. During the off period of the switching element, the magnetic energy stored in the transformer is output as power to the secondary side through the diode.
特開平７－３１１５０号公報Japanese Patent Application Laid-Open No. 7-31150 特開平８－３３１８６０号公報JP-A-8-331860 特開２００２－１０６３２号公報Japanese Patent Application Laid-Open No. 2002-10632 特開２００５－２１８２２４号公報JP 2005-218224 A 特開２００７－３７２９７号公報JP 2007-37297 A
　フライバック方式のスイッチング電源においては、スイッチング素子がオフになった瞬間にトランスの一次コイルに高い逆起電力（本明細書における「起電力」及び「逆起電力」は電圧の意味で用いる）すなわちサージ電圧が発生してスイッチング素子に印加される。このため、高耐圧のスイッチング素子を用いたり、逆起電力を処理するためのスナバ回路等を設けたりすることが必要であった。 In a flyback type switching power supply, the high back electromotive force (in the present specification, “electromotive force” and “back electromotive force” are used in the sense of voltage) in the primary coil of the transformer at the moment when the switching element is turned off A surge voltage is generated and applied to the switching element. For this reason, it has been necessary to use a high withstand voltage switching element or to provide a snubber circuit or the like for processing a back electromotive force.
　以上の問題点に鑑み本発明の目的は、フライバック方式の絶縁型スイッチング電源において、スイッチング素子のオフ時にトランスの一次コイルに発生する逆起電力を抑制し、スイッチング素子に要求される耐圧性を軽減することである。 In view of the above problems, it is an object of the present invention to suppress the back electromotive force generated in the primary coil of the transformer when the switching element is off in an isolated switching power supply of flyback type, and to set the withstand voltage required of the switching element. It is to reduce.
　上記の目的を達成する本発明の絶縁型スイッチング電源の第１の態様は、以下の通りである。
　（ａ）一次コイルと二次コイルを具備する第１のトランスと、
　（ｂ）前記第１のトランスの一次コイルと直列接続されかつ制御信号によりオンオフ制御されるスイッチング素子と、
　（ｃ）一次コイルと二次コイルを具備する第２のトランスであって、前記第１のトランスの二次コイルと該第２のトランスの一次コイルが第１の接続点及び第２の接続点により並列接続され、該第２の接続点が該第２のトランスの二次コイルの一端であると共に第１の出力端でもある、前記第２のトランスと、
　（ｄ）第２の出力端から前記並列接続における第１の接続点へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第１の整流要素と、
　（ｅ）第２の出力端から前記第２のトランスの二次コイルの他端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第２の整流要素と、を有することを特徴とする。
　さらに、本発明の絶縁型スイッチング電源の第２の態様は、以下の通りである。
　（ａ）一次コイルと二次コイルを具備する第１のトランスと、
　（ｂ）前記第１のトランスの一次コイルと直列接続されかつ制御信号によりオンオフ制御されるスイッチング素子と、
　（ｃ）一次コイルと二次コイルを具備する第２のトランスであって、前記第１のトランスの二次コイルと該第２のトランスの一次コイルが第１の接続点及び第２の接続点により並列接続され、該第２の接続点が第１の出力端である、前記第２のトランスと、
　（ｄ）前記第２のトランスの二次コイルの一端と前記第１の出力端の間に接続されたインダクタと、
　（ｅ）第２の出力端から前記並列接続における第１の接続点へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第１の整流要素と、
　（ｆ）第２の出力端から前記第２のトランスの二次コイルの他端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第２の整流要素と、
　（ｇ）第２の出力端から前記第２のトランスの二次コイルの一端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第３の整流要素と、を有することを特徴とする。 The first aspect of the isolated switching power supply of the present invention which achieves the above object is as follows.
(A) a first transformer comprising a primary coil and a secondary coil;
(B) a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal;
(C) A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point The second transformer connected in parallel, the second connection point being one end of the secondary coil of the second transformer and also the first output end;
(D) a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction;
(E) a second rectifying element connected to conduct a current flowing from the second output end to the other end of the secondary coil of the second transformer and to block a current in the opposite direction; It is characterized by
Furthermore, the second aspect of the isolated switching power supply of the present invention is as follows.
(A) a first transformer comprising a primary coil and a secondary coil;
(B) a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal;
(C) A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point Connected in parallel by the second transformer, the second connection point being a first output end;
(D) an inductor connected between one end of the secondary coil of the second transformer and the first output end;
(E) a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction;
(F) a second rectifying element connected so as to conduct current flowing from the second output end to the other end of the secondary coil of the second transformer and block current flowing in the opposite direction;
(G) having a third rectifying element connected to conduct current flowing from the second output end to one end of the secondary coil of the second transformer and to block current flowing in the opposite direction; It is characterized by
　本発明により、絶縁型スイッチング電源において、スイッチング素子のオフ時にトランスの一次コイルに発生する逆起電力すなわちサージ電圧を抑制し、スイッチング素子に要求される耐圧性を軽減することが実現される。 According to the present invention, in an isolated switching power supply, it is possible to suppress the back electromotive force generated in the primary coil of the transformer when the switching element is off, that is, the surge voltage, and reduce the withstand voltage required for the switching element.
図１は、本発明の絶縁型スイッチング電源の第１の実施形態の回路構成例を概略的に示した図である。FIG. 1 is a diagram schematically showing a circuit configuration example of a first embodiment of the isolated switching power supply of the present invention. 図２（ａ）（ｂ）は、それぞれ図１の回路におけるオン期間及びオフ期間の電流の流れを概略的に示した図である。FIGS. 2 (a) and 2 (b) schematically show the flow of current in the on period and the off period in the circuit of FIG. 1, respectively. 図３（ａ）（ｂ）は、それぞれ図１の回路におけるオン期間及びオフ期間のトランス二次側の電位関係の一例を概略的に示した図である。3 (a) and 3 (b) are diagrams schematically showing an example of the potential relationship on the transformer secondary side of the on period and the off period in the circuit of FIG. 1, respectively. 図４は、本発明の絶縁型スイッチング電源の第２の実施形態の回路構成例を概略的に示した図である。FIG. 4 is a view schematically showing a circuit configuration example of a second embodiment of the isolated switching power supply of the present invention. 図５（ａ）（ｂ）は、それぞれ図４の回路におけるオン期間及びオフ期間の電流の流れを概略的に示した図である。5 (a) and 5 (b) are diagrams schematically showing the flow of current in the on period and the off period in the circuit of FIG. 4, respectively. 図６（ａ）（ｂ）は、それぞれ図４の回路におけるオン期間及びオフ期間のトランス二次側の電位関係の一例を概略的に示した図である。6 (a) and 6 (b) are diagrams schematically showing an example of the potential relationship on the transformer secondary side of the on period and the off period in the circuit of FIG. 4, respectively.
　以下、実施例を示した図面を参照しつつ、本発明による絶縁型スイッチング電源の実施形態について説明する。各実施形態の図面において、同一又は類似の構成要素については、同じ符号で示している。 Hereinafter, embodiments of the isolated switching power supply according to the present invention will be described with reference to the drawings showing the embodiments. In the drawings of each embodiment, the same or similar components are denoted by the same reference numerals.
　以下では、直流電圧が入力されるＤＣ／ＤＣコンバータの場合を実施例として本発明の絶縁型スイッチング電源を説明する。しかしながら、本発明の絶縁型スイッチング電源は、電圧が一定の直流以外に、電圧が変動する脈流若しくは矩形波、又は交流等、どのような波形の電圧が入力されても同様に機能し、直流電圧を出力することができる電力変換装置である。 In the following, the isolated switching power supply of the present invention will be described by way of an example of a DC / DC converter to which a DC voltage is input. However, the isolated switching power supply according to the present invention functions similarly even if a voltage of any waveform is inputted, such as a pulsating current or a rectangular wave whose voltage fluctuates, or an alternating current other than a direct current having a constant voltage. It is a power converter capable of outputting a voltage.
（１）第１の実施形態
（１－１）第１の実施形態の回路構成
　図１は、本発明の絶縁型スイッチング電源の第１の実施形態の回路構成例を概略的に示した図である。 (1) First Embodiment (1-1) Circuit Configuration of First Embodiment FIG. 1 is a view schematically showing a circuit configuration example of a first embodiment of the isolated switching power supply of the present invention. is there.
　図１を参照して、第１の実施形態の回路構成を説明する。本回路は、トランスにより入力側と出力側を電気的に絶縁する絶縁型スイッチング電源であり、フライバック方式をベースとしている。このスイッチング電源は、第１のトランスＴ１及び第２のトランスＴ２を有する。トランスＴ１により一次側と二次側が絶縁されている。トランスＴ１は、一次コイル１Ｎｐと二次コイル１Ｎｓを具備する。トランスＴ２は、一次コイル２Ｎｐと二次コイル２Ｎｓを具備する。トランスＴ１及びトランスＴ２はいずれも、一次コイルと二次コイルの極性が逆向きであり、一般的なフライバック方式のトランスと同じである。トランスＴ１及びトランスＴ２はいずれも、結合度をできるだけ高くする、すなわち一次コイルと二次コイルを密結合とすることが好適である。 The circuit configuration of the first embodiment will be described with reference to FIG. This circuit is an isolated switching power supply in which the input side and the output side are electrically isolated by a transformer, and is based on a flyback method. This switching power supply has a first transformer T1 and a second transformer T2. The primary side and the secondary side are isolated by the transformer T1. The transformer T1 includes a primary coil 1Np and a secondary coil 1Ns. The transformer T2 includes a primary coil 2Np and a secondary coil 2Ns. In each of the transformer T1 and the transformer T2, the polarities of the primary coil and the secondary coil are opposite to each other, and are the same as a general flyback type transformer. It is preferable that both the transformer T1 and the transformer T2 have the coupling degree as high as possible, that is, the primary coil and the secondary coil be closely coupled.
　図中、各コイルの巻き始端を黒丸で示している。本明細書でコイルについて「一端」と「他端」という場合は、それぞれ「巻き始端」と「巻き終端」に対応する場合と、「巻き終端」と「巻き始端」に対応する場合のいずれも含むものとする。以下の説明では、各コイルについて、巻き始端を一端と称し、巻き終端を他端と称する。 In the figure, the winding start end of each coil is shown by a black circle. In the present specification, when the coil is referred to as "one end" and "the other end", the coil corresponds to the "roll start end" and the "roll end", and the coil end corresponds to the "roll end" and the "roll start end", respectively. Shall be included. In the following description, for each coil, the winding start end is referred to as one end, and the winding end is referred to as the other end.
　入力電圧は、第１の入力端１と第２の入力端２からなる一対の端子間に印加される。トランスＴ１の一次コイル１Ｎｐの一端は、入力端１に接続されている。ここでは、入力端２が入力側基準電位端である。 An input voltage is applied between a pair of terminals consisting of a first input 1 and a second input 2. One end of the primary coil 1 Np of the transformer T 1 is connected to the input end 1. Here, the input end 2 is the input side reference potential end.
　スイッチング素子Ｑが、トランスＴ１の一次コイル１Ｎｐに直列接続されている。ここでは、スイッチング素子Ｑは一次コイル１Ｎｐと入力端２の間に接続されている。スイッチング素子Ｑは制御端を具備し、制御端は、一次コイル１Ｎｐを含む電流路を導通又は遮断するようにオンオフ制御される。 The switching element Q is connected in series to the primary coil 1Np of the transformer T1. Here, the switching element Q is connected between the primary coil 1 Np and the input terminal 2. The switching element Q has a control end, and the control end is on / off controlled to conduct or interrupt the current path including the primary coil 1Np.
　スイッチング素子Ｑの制御端は、制御信号Ｖｇにより制御される。制御信号Ｖｇは、例えば所定の周波数及びデューティ比のパルス波形をもつＰＷＭ信号である。図示の例では、スイッチング素子Ｑがｎチャネル形ＭＯＳＦＥＴ（以下「ＦＥＴＱ」と称する）であり、一端がドレイン、他端がソース、制御端がゲートである。この場合、制御信号Ｖｇは電圧信号である。 The control end of the switching element Q is controlled by a control signal Vg. The control signal Vg is, for example, a PWM signal having a pulse waveform of a predetermined frequency and a duty ratio. In the illustrated example, the switching element Q is an n-channel MOSFET (hereinafter referred to as "FET Q"), one end is a drain, the other end is a source, and the control end is a gate. In this case, the control signal Vg is a voltage signal.
　なお、ＦＥＴ以外のスイッチング素子として、例えばＩＧＢＴ又はバイポーラトランジスタを用いることもできる。 For example, an IGBT or a bipolar transistor can be used as a switching element other than the FET.
　トランスＴ１の二次側には、第１の出力端である正極出力端ｐと第２の出力端である負極出力端ｎが設けられている。正極出力端ｐと負極出力端ｎの間に直流電圧が出力される。ここでは、負極出力端ｎが二次側基準電位端である。正極出力端ｐと負極出力端ｎの間に接続された負荷（図示せず）に出力電圧が印加され、出力電流が供給される。 On the secondary side of the transformer T1, a positive output end p which is a first output end and a negative output end n which is a second output end are provided. A DC voltage is output between the positive electrode output end p and the negative electrode output end n. Here, the negative electrode output end n is the secondary side reference potential end. An output voltage is applied to a load (not shown) connected between the positive electrode output end p and the negative electrode output end n, and an output current is supplied.
　トランスＴ１の二次コイル１Ｎｓに対してトランスＴ２の一次コイル２Ｎｐが並列接続されている。ここでは、第１の接続点ａにおいて、トランスＴ１の二次コイル１Ｎｓの一端とトランスＴ２の一次コイル２Ｎｐの一端とが接続されると共に、第２の接続点ｂにおいて、トランスＴ１の二次コイル１Ｎｓの他端とトランスＴ２の一次コイル２Ｎｐの他端とが接続されている。 The primary coil 2Np of the transformer T2 is connected in parallel to the secondary coil 1Ns of the transformer T1. Here, one end of the secondary coil 1Ns of the transformer T1 and one end of the primary coil 2Np of the transformer T2 are connected at the first connection point a, and the secondary coil of the transformer T1 is connected at the second connection point b. The other end of 1 Ns is connected to the other end of the primary coil 2 Np of the transformer T2.
　さらに、第２の接続点ｂはトランスＴ２の二次コイル２Ｎｓの一端でもあり、かつ、第２の接続点ｂは、正極出力端ｐでもある。 Furthermore, the second connection point b is also one end of the secondary coil 2Ns of the transformer T2, and the second connection point b is also the positive electrode output end p.
　さらに、第１の接続点ａと負極出力端ｎの間に第１の整流要素Ｄ１が接続されている。整流要素Ｄ１は、負極出力端ｎから第１の接続点ａへ流れる電流を導通させ、それとは逆方向の電流を遮断することができるように接続されている。したがって、整流要素Ｄ１がダイオードである場合、ダイオードＤ１は、アノードが負極出力端ｎに、カソードが第１の接続点ａに接続されている。 Furthermore, a first rectifying element D1 is connected between the first connection point a and the negative output end n. The rectifying element D1 is connected so as to conduct the current flowing from the negative electrode output end n to the first connection point a and to cut off the current in the opposite direction. Therefore, when the rectifying element D1 is a diode, the diode D1 has an anode connected to the negative output terminal n and a cathode connected to the first connection point a.
　さらに、トランスＴ２の二次コイル２Ｎｓの他端と負極出力端ｎの間に第２の整流要素Ｄ２が接続されている。整流要素Ｄ２は、負極出力端ｎから二次コイル２Ｎｓの他端へ流れる電流を導通させ、それとは逆方向の電流を遮断することができるように接続されている。したがって、整流要素Ｄ２が例えばダイオードである場合、ダイオードＤ２は、アノードが負極出力端ｎに、カソードが二次コイル２Ｎｓの他端に接続されている。 Furthermore, a second rectifying element D2 is connected between the other end of the secondary coil 2Ns of the transformer T2 and the negative output end n. The rectifying element D2 is connected so as to conduct current flowing from the negative electrode output end n to the other end of the secondary coil 2Ns and to cut off current in the opposite direction. Therefore, when the rectifying element D2 is, for example, a diode, the diode D2 has an anode connected to the negative output terminal n and a cathode connected to the other end of the secondary coil 2Ns.
　本回路におけるダイオード等の整流要素は、順方向電圧降下が小さくかつ高速動作を行うものが好適である。なお、ダイオード以外の整流要素の例としては、同等の整流機能を有する他の素子又は回路を用いることができる（以下の実施形態の各整流要素についても同じ）。 The rectifying element such as a diode in this circuit preferably has a small forward voltage drop and operates at high speed. In addition, as an example of rectification | straightening elements other than a diode, the other element or circuit which has an equivalent rectification function can be used (the same may be said of each rectification | straightening element of the following embodiment).
　さらに、正極出力端ｐと負極出力端ｎの間には、平滑用のコンデンサＣが接続されている。 Furthermore, a smoothing capacitor C is connected between the positive electrode output end p and the negative electrode output end n.
　図示しないが、スイッチング素子Ｑのための制御信号Ｖｇを発生する制御部を有することが好ましい。一例として制御部は、入力電圧及び／又は出力電圧を検出し、検出した電圧に基づいて制御信号Ｖｇのデューティ比を決定し、それに基づいて所定の高周波パルスの制御信号Ｖｇを生成する。このような制御部の主要部として、ＰＷＭＩＣを用いることができる（以下の実施形態においても同じ）。 Although not shown, it is preferable to have a control unit that generates a control signal Vg for the switching element Q. As an example, the control unit detects an input voltage and / or an output voltage, determines a duty ratio of the control signal Vg based on the detected voltage, and generates a control signal Vg of a predetermined high frequency pulse based thereon. A PWM IC can be used as a main part of such a control unit (the same applies to the following embodiments).
（１－２）第１の実施形態の動作
　図２及び図３を参照して図１に示した回路の動作を説明する。図２（ａ）及び（ｂ）は、それぞれオン期間及びオフ期間における電流の流れを概略的に示している（矢印は電流の向きを示す）。図３（ａ）及び（ｂ）は、それぞれオン期間及びオフ期間におけるトランスＴ１の二次側の各構成要素の電位関係の一例を模式的に示す図である。 (1-2) Operation of the First Embodiment The operation of the circuit shown in FIG. 1 will be described with reference to FIGS. 2 and 3. FIGS. 2 (a) and 2 (b) schematically show the flow of current during on and off periods, respectively (arrows indicate the direction of the current). FIGS. 3A and 3B are diagrams schematically showing an example of the potential relationship between components on the secondary side of the transformer T1 in the on period and the off period, respectively.
　図３（ａ）（ｂ）では、上下方向が電位の高低に対応しており、二次側基準電位（負極出力端ｎの電位）を太線で示している。トランスＴ１の二次コイル１Ｎｓ、トランスＴ２の一次コイル２Ｎｐ及び二次コイル２Ｎｓ、並びにコンデンサＣの両端電圧を両矢印で示している。また、各コイルについては、巻き始端側を黒丸で示している（他の実施形態の電位関係図についても同じ）。 In FIGS. 3A and 3B, the vertical direction corresponds to the level of the potential, and the secondary side reference potential (the potential of the negative electrode output end n) is indicated by a thick line. Voltages at both ends of the secondary coil 1Ns of the transformer T1, the primary coil 2Np and the secondary coil 2Ns of the transformer T2, and the capacitor C are indicated by double arrows. Moreover, about each coil, the winding start end side is shown as a black circle (the same may be said of the electrical potential relationship figure of other embodiment).
　なお、本回路の始動時及び停止時の過渡的動作は例外とし、本回路が定常状態にある場合の動作について説明する。定常状態では、平滑用のコンデンサＣは、リップル的な変動を除いてほぼ一定の両端電圧で充電されている。以下の説明では、コンデンサＣの充放電電流及び各ダイオードの順方向電圧降下については無視する（他の実施形態についても同じ）。 The transient operation at the start and stop of the circuit is an exception, and the operation when the circuit is in the steady state will be described. In the steady state, the smoothing capacitor C is charged at a substantially constant voltage across it, except for ripple fluctuations. In the following description, the charge / discharge current of the capacitor C and the forward voltage drop of each diode are ignored (the same applies to the other embodiments).
（１－２－１）オン期間におけるトランスＴ１の一次側及び二次側の動作
［オン期間：一次側］
　トランスＴ１の一次側では、オン期間に制御信号Ｖｇがオンになると、ＦＥＴＱがオンとなり電流路が導通する。図２（ａ）に示すように、トランスＴ１の一次コイル１Ｎｐには、入力電圧による入力電流ｉ1が以下の経路で流れる。
　・入力電流ｉ1：入力端１→トランスＴ１の一次コイル１Ｎｐ→ＦＥＴＱ→入力端２ (1-2-1) Operation of the primary side and secondary side of the transformer T1 in the on period [on period: primary side]
On the primary side of the transformer T1, when the control signal Vg is turned on in the on period, the FET Q is turned on and the current path is conducted. As shown in FIG. 2A, an input current i1 according to an input voltage flows through the primary coil 1Np of the transformer T1 in the following path.
· Input current i1: input end 1 → primary coil 1Np of transformer T1 → FET Q → input end 2
　トランスＴ１は、一次コイル１Ｎｐに電流ｉ1が流れることにより励磁され、オン期間に所定の磁気エネルギーが蓄積される。 The transformer T1 is excited by the flow of the current i1 through the primary coil 1Np, and predetermined magnetic energy is accumulated in the on period.
［オン期間：二次側］
　図２（ａ）に示すように、トランスＴ１の一次コイル１Ｎｐに入力電流ｉ1が流れることにより、二次コイル１Ｎｓに起電力が生じ、短絡電流である電流ｉ2が以下の経路で流れる。ダイオードＤ１は、逆バイアスとなるため遮断されている。
　・電流ｉ2：トランスＴ１の二次コイル１Ｎｓ→トランスＴ２の一次コイル２Ｎｐ [On period: Secondary side]
As shown in FIG. 2A, when the input current i1 flows through the primary coil 1Np of the transformer T1, an electromotive force is generated in the secondary coil 1Ns, and a current i2 which is a short circuit current flows in the following path. The diode D1 is cut off because it is reverse biased.
Current i2: secondary coil 1Ns of transformer T1 → primary coil 2Np of transformer T2
　図３（ａ）の電位関係図に示すように、トランスＴ２の一次コイル２Ｎｐの両端電圧は、トランスＴ１の二次コイル１Ｎｓに生じた起電力と同じ大きさである。トランスＴ２においては、一次コイル２Ｎｐに電流ｉ2が流れることにより、二次コイル２Ｎｓに起電力が生じる。ダイオードＤ２は、順バイアスとなるため導通し、以下の経路で電流ｉ3が流れる。
　・電流ｉ3：負極出力端ｎ→ダイオードＤ２→トランスＴ２の二次コイル２Ｎｓ→正極出力端ｐ As shown in the potential relationship diagram of FIG. 3A, the voltage across the primary coil 2Np of the transformer T2 has the same magnitude as the electromotive force generated in the secondary coil 1Ns of the transformer T1. In the transformer T2, when the current i2 flows through the primary coil 2Np, an electromotive force is generated in the secondary coil 2Ns. The diode D2 conducts because it is forward biased, and the current i3 flows in the following path.
Current i3: negative electrode output terminal n → diode D2 → secondary coil 2Ns of transformer T2 → positive electrode output terminal p
　トランスＴ２は、フォワード方式における外付けインダクタと同様に、回路始動時におけるコンデンサＣへの突入電流を抑制する効果もある。 The transformer T2 also has an effect of suppressing an inrush current to the capacitor C at the time of circuit start-up, like the external inductor in the forward system.
　トランスＴ２は、一次コイル２Ｎｐに流れる電流ｉ2により励磁されて磁気エネルギーが蓄積されると同時に、相互誘導により二次コイル２Ｎｓに電流ｉ3が流れ出力されることにより電力伝達が行われる。 The transformer T2 is excited by the current i2 flowing through the primary coil 2Np and stores magnetic energy, and at the same time the current i3 flows through the secondary coil 2Ns by mutual induction and power is transferred.
　ここで、トランスＴ１は、通常のフライバック方式とは異なり、二次コイル１Ｎｓに相互誘導による電流ｉ2が流れるので、通常のフライバック方式に比べてトランスＴ１に蓄積される磁気エネルギーは小さくなる。その低減した分の磁気エネルギーは、トランスＴ２に移行する。 Here, unlike the normal flyback system, since the current i2 due to mutual induction flows through the secondary coil 1Ns, the magnetic energy stored in the transformer T1 is smaller than that of the normal flyback system. The reduced magnetic energy is transferred to the transformer T2.
　好適には、トランスＴ１に蓄積される磁気エネルギーよりも、トランスＴ２に移行するエネルギーの方を大きくする。トランスＴ２に移行したエネルギーは、トランスＴ２に蓄積される磁気エネルギーと、トランスＴ２からの出力電力（電流ｉ3）になる。 Preferably, the energy transferred to the transformer T2 is larger than the magnetic energy stored in the transformer T1. The energy transferred to the transformer T2 becomes the magnetic energy stored in the transformer T2 and the output power (current i3) from the transformer T2.
　したがって、本回路は、フライバック方式をベースとしているにも拘わらず、オン期間に外付けインダクタに磁気エネルギーを蓄積させかつ電力を出力するフォワード方式電源に類似しているとも言える。トランスＴ１、Ｔ２の各コイルのインダクタンス、巻数比及び巻線数等を適切に設計することにより、オン期間にトランスＴ２により大きなエネルギーを移行させることを実現できる。 Therefore, although this circuit is based on the flyback method, it can be said that it is similar to a forward type power supply that allows the external inductor to store magnetic energy and output power during the on period. By appropriately designing the inductance, the turns ratio, the number of turns, and the like of each of the coils of the transformers T1 and T2, it is possible to realize the transfer of larger energy by the transformer T2 during the on period.
（１－２－２）オフ期間におけるトランスＴ１の一次側及び二次側の動作
［オフ期間：一次側］
　図２（ｂ）に示すように、トランスＴ１の一次側では、制御信号Ｖｇがオフになると、ＦＥＴＱもオフとなる。これにより、トランスＴ１の一次コイル１Ｎｐの電流路は遮断され、電流が零となる。その結果、トランスＴ１の一次コイル１Ｎｐ及び二次コイル１Ｎｓにそれぞれ逆起電力が生じる。 (1-2-2) Operation of primary side and secondary side of transformer T1 in off period [off period: primary side]
As shown in FIG. 2B, on the primary side of the transformer T1, when the control signal Vg is turned off, the FET Q is also turned off. As a result, the current path of the primary coil 1Np of the transformer T1 is cut off and the current becomes zero. As a result, a back electromotive force is generated in each of the primary coil 1Np and the secondary coil 1Ns of the transformer T1.
　上述した通り、本回路ではトランスＴ２を設けたことにより、通常のフライバック方式電源に比べて、オン期間にトランスＴ１に蓄積される磁気エネルギーが少なくなるので、オフとなった瞬間にトランスＴ１の一次コイル１Ｎｐに生じる逆起電力すなわちサージ電圧も小さくなる。 As described above, the provision of the transformer T2 in this circuit reduces the amount of magnetic energy stored in the transformer T1 during the on period as compared to a normal flyback type power supply. The back electromotive force or surge voltage generated in the primary coil 1Np also decreases.
　スイッチング素子Ｑ（ＦＥＴの場合、ドレインソース間）には、入力電圧と一次コイル１Ｎｐに生じる逆起電力を加算した電圧が印加される。したがって、本回路では、スイッチング素子Ｑに要求される耐圧性が軽減されるとともに、スナバ回路等の処理容量を低減できる。同様に、トランスＴ１の磁気飽和の可能性も小さくなることから、トランスＴ１のサイズを小さくすることができる。 A voltage obtained by adding an input voltage and a back electromotive force generated in the primary coil 1Np is applied to the switching element Q (between the drain and the source in the case of an FET). Therefore, in the present circuit, the withstand voltage required for the switching element Q is reduced, and the processing capacity of the snubber circuit can be reduced. Similarly, since the possibility of magnetic saturation of the transformer T1 is also reduced, the size of the transformer T1 can be reduced.
［オフ期間：二次側］
　図３（ｂ）の電位関係図に示すように、オフ期間になると、トランスＴ１の二次コイル１Ｎｓ、トランスＴ２の一次コイル２Ｎｐ及び二次コイル２Ｎｓの各々の両端の電位関係が反転する。ダイオードＤ２は、逆バイアスとなり遮断される。一方、ダイオードＤ１が順バイアスとなり導通し、図２（ｂ）に示すように電流ｉ4及び電流ｉ5が以下の経路で流れる。
　・電流ｉ4：負極出力端ｎ→ダイオードＤ１→トランスＴ２の一次コイル２Ｎｐ→正極出力端ｐ
　・電流ｉ5：負極出力端ｎ→ダイオードＤ１→トランスＴ１の二次コイル１Ｎｓ→正極出力端ｐ [Off period: Secondary side]
As shown in the potential relationship diagram of FIG. 3B, in the off period, the potential relationship between both ends of each of the secondary coil 1Ns of the transformer T1, the primary coil 2Np of the transformer T2, and the secondary coil 2Ns is reversed. The diode D2 is reverse biased and cut off. On the other hand, the diode D1 becomes forward biased and becomes conductive, and as shown in FIG. 2B, the current i4 and the current i5 flow in the following path.
Current i4: negative electrode output terminal n → diode D1 → primary coil 2Np of transformer T2 → positive electrode output terminal p
Current i5: negative electrode output end n → diode D1 → secondary coil 1Ns of transformer T1 → positive electrode output end p
　電流ｉ4が流れることにより、トランスＴ２にオン期間に蓄積された磁気エネルギーが、オフ期間に電力として出力される。また、電流ｉ5が流れることにより、トランスＴ１にオン期間に蓄積された磁気エネルギーが、オフ期間に電力として出力される。好適な設計においては、トランスＴ１に蓄積された磁気エネルギーは、トランスＴ２に蓄積された磁気エネルギーよりも小さいため、電流ｉ5は電流ｉ4に比べて小さい。 When the current i4 flows, the magnetic energy stored in the on period in the transformer T2 is output as power in the off period. Further, when the current i5 flows, the magnetic energy accumulated in the on period in the transformer T1 is output as the power in the off period. In the preferred design, the magnetic energy stored in the transformer T1 is smaller than the magnetic energy stored in the transformer T2, so the current i5 is smaller than the current i4.
（２）第２の実施形態
（２－１）第２の実施形態の回路構成
　本発明の絶縁型スイッチング電源の第２の実施形態は、第１の実施形態の変形形態である。図４は、第２の実施形態の回路構成例を概略的に示した図である。図５（ａ）及び（ｂ）は、それぞれオン期間及びオフ期間の電流の流れを概略的に示している。 (2) Second Embodiment (2-1) Circuit Configuration of Second Embodiment The second embodiment of the isolated switching power supply according to the present invention is a modification of the first embodiment. FIG. 4 is a diagram schematically showing a circuit configuration example of the second embodiment. FIGS. 5 (a) and 5 (b) schematically show the flow of current during on and off periods, respectively.
　第２の実施形態においても、フライバック方式の２つのトランスＴ１、Ｔ２を用いている。トランスＴ１の一次側の構成は、第１の実施形態と同じである。さらに、トランスＴ１の二次コイル１ＮｓとトランスＴ２の一次コイル２Ｎｐが並列接続された構成、その並列接続における第１の接続点ａと負極出力端ｎの間にダイオードＤ１が接続された構成、トランスＴ２の二次コイル２Ｎｓの他端と負極出力端ｎの間にダイオードＤ２が接続された構成、並びに、出力端ｐ、ｎの間に平滑用のコンデンサＣが接続された構成も、第１の実施形態と同じである。 Also in the second embodiment, two flyback transformers T1 and T2 are used. The configuration of the primary side of the transformer T1 is the same as that of the first embodiment. Furthermore, a configuration in which the secondary coil 1Ns of the transformer T1 and the primary coil 2Np of the transformer T2 are connected in parallel, a configuration in which the diode D1 is connected between the first connection point a and the negative output terminal n in the parallel connection, a transformer A configuration in which the diode D2 is connected between the other end of the secondary coil 2Ns of T2 and the negative electrode output end n, and a configuration in which a smoothing capacitor C is connected between the output ends p and n are also the first It is the same as the embodiment.
　第２の実施形態では、トランスＴ２の二次コイル２Ｎｓの一端と第２の接続点ｂすなわち、正極出力端ｐの間にインダクタＬが接続されている。 In the second embodiment, the inductor L is connected between one end of the secondary coil 2Ns of the transformer T2 and the second connection point b, that is, the positive electrode output end p.
　さらに、トランスＴ２の二次コイル２Ｎｓの一端と負極出力端ｎとの間に第３の整流要素Ｄ３が接続されている。整流要素Ｄ３は、負極出力端ｎから二次コイル２Ｎｓの一端へ流れる電流を導通させ、それとは逆方向の電流を遮断することができるように接続されている。したがって、整流要素Ｄ３が例えばダイオードである場合、ダイオードＤ３は、アノードが負極出力端ｎに、カソードが二次コイル２Ｎｓの一端に接続されている。 Furthermore, a third rectifying element D3 is connected between one end of the secondary coil 2Ns of the transformer T2 and the negative output end n. The rectifying element D3 is connected so as to conduct current flowing from the negative electrode output end n to one end of the secondary coil 2Ns, and to cut off current in the opposite direction. Therefore, when the rectifying element D3 is, for example, a diode, the diode D3 has an anode connected to the negative output terminal n and a cathode connected to one end of the secondary coil 2Ns.
（２－２）第２の実施形態の動作説明
　図５及び図６を参照して、第２の実施形態の動作について、主に第１の実施形態とは異なる点を説明する。図５（ａ）及び（ｂ）は、それぞれオン期間及びオフ期間における電流の流れを概略的に示している（矢印は電流の向きを示す）。図６（ａ）及び（ｂ）は、それぞれオン期間及びオフ期間におけるトランスＴ１の二次側の各構成要素の電位関係の一例を模式的に示す図である。 (2-2) Description of Operation of Second Embodiment The operation of the second embodiment will be described mainly with reference to FIGS. 5 and 6, except for differences from the first embodiment. FIGS. 5 (a) and 5 (b) schematically show the flow of current during on and off periods, respectively (arrows indicate the direction of the current). FIGS. 6A and 6B are diagrams schematically showing an example of the potential relationship between components on the secondary side of the transformer T1 in the on period and the off period, respectively.
（２－２－１）オン期間におけるトランスＴ１の一次側及び二次側の動作
［オン期間：一次側］
　トランスＴ１の一次側では、オン期間に制御信号Ｖｇがオンになると、ＦＥＴＱがオンとなり電流路が導通する。トランスＴ１の一次コイル１Ｎｐには、図５（ａ）に示すように入力電圧による入力電流ｉ1が以下の経路で流れる。
　・入力電流ｉ1：入力端１→トランスＴ１の一次コイル１Ｎｐ→ＦＥＴＱ→入力端２ (2-2-1) Operation of the primary side and secondary side of the transformer T1 in the on period [on period: primary side]
On the primary side of the transformer T1, when the control signal Vg is turned on in the on period, the FET Q is turned on and the current path is conducted. In the primary coil 1Np of the transformer T1, as shown in FIG. 5A, an input current i1 according to the input voltage flows in the following path.
· Input current i1: input end 1 → primary coil 1Np of transformer T1 → FET Q → input end 2
［オン期間：二次側］
　図５（ａ）に示すように、トランスＴ１の一次コイル１Ｎｐに入力電流ｉ1が流れることにより、二次コイル１Ｎｓに起電力が生じ、短絡電流である電流ｉ2が以下の経路で流れる。ダイオードＤ１は、逆バイアスであるため遮断されている。
　・電流ｉ2：トランスＴ１の二次コイル１Ｎｓ→トランスＴ２の一次コイル２Ｎｐ [On period: Secondary side]
As shown in FIG. 5A, when the input current i1 flows through the primary coil 1Np of the transformer T1, an electromotive force is generated in the secondary coil 1Ns, and a current i2 which is a short circuit current flows in the following path. The diode D1 is blocked because it is reverse biased.
Current i2: secondary coil 1Ns of transformer T1 → primary coil 2Np of transformer T2
　図６（ａ）の電位関係図に示すように、トランスＴ２の一次コイル２ＮｐとトランスＴ１の二次コイル１Ｎｓは並列であるので両端電圧は同じ大きさである。トランスＴ２においては、一次コイル２Ｎｐに電流ｉ2が流れることにより、二次コイル２Ｎｓに起電力が生じる。ダイオードＤ２は順バイアスとなるため導通し、以下の経路で電流ｉ3が流れる。
　・電流ｉ3：負極出力端ｎ→ダイオードＤ２→トランスＴ２の二次コイル２Ｎｓ→インダクタＬ→正極出力端ｐ As shown in the potential relationship diagram of FIG. 6A, since the primary coil 2Np of the transformer T2 and the secondary coil 1Ns of the transformer T1 are parallel to each other, the voltages at both ends are the same. In the transformer T2, when the current i2 flows through the primary coil 2Np, an electromotive force is generated in the secondary coil 2Ns. The diode D2 conducts because it becomes forward bias, and the current i3 flows in the following path.
Current i3: negative electrode output end n → diode D2 → secondary coil 2Ns of transformer T2 → inductor L → positive electrode output end p
　オン期間のトランスＴ２においては、一次コイル２Ｎｐに流れる電流ｉ2により励磁されて磁気エネルギーが蓄積されると同時に、相互誘導により二次コイル２Ｎｓに電流ｉ3が流れ出力されることにより、電力伝達も行われる。 The transformer T2 in the on period is excited by the current i2 flowing through the primary coil 2Np and stores magnetic energy, and at the same time, the current i3 flows through the secondary coil 2Ns by mutual induction and the power transfer is also performed. It will be.
　インダクタＬは、通常のフォワード方式におけるインダクタと同様に、電流ｉ3が流れることにより励磁されて磁気エネルギーが蓄積される。また、インダクタＬは、回路始動時におけるコンデンサＣへ突入電流を抑制する役割も果たす。 The inductor L is excited by the flow of the current i3 to accumulate magnetic energy, like the inductor in the normal forward system. In addition, the inductor L also plays a role of suppressing inrush current to the capacitor C at the start of the circuit.
　なお、ダイオードＤ３は逆バイアスとなるため遮断されている。その他のオン期間の動作については、第１の実施形態と同じである。 The diode D3 is cut off because it is reverse biased. The other on-period operations are the same as in the first embodiment.
　第２の実施形態におけるオン期間の電流の流れは、第１の実施形態と同じである。第２の実施形態においても、トランスＴ１に蓄積させる磁気エネルギーよりも、トランスＴ２及びインダクタＬに移行させるエネルギーの方を大きくすることが好適である。 The flow of current during the on period in the second embodiment is the same as in the first embodiment. Also in the second embodiment, it is preferable to make the energy transferred to the transformer T2 and the inductor L larger than the magnetic energy stored in the transformer T1.
（２－２－２）オフ期間におけるトランスＴ１の一次側及び二次側の動作の詳細
［オフ期間：一次側］
　トランスＴ１の一次側では、制御信号Ｖｇがオフになると、ＦＥＴＱもオフとなりスイッチが開く。トランスＴ１の一次コイル１Ｎｐの電流路は遮断され、電流が零となる。これによりトランスＴ１の一次コイル１Ｎｐ及び二次コイル１Ｎｓにそれぞれ逆起電力が生じる。 (2-2-2) Details of operation of the primary side and secondary side of the transformer T1 in the off period [off period: primary side]
On the primary side of the transformer T1, when the control signal Vg is turned off, the FET Q is also turned off and the switch is opened. The current path of the primary coil 1Np of the transformer T1 is cut off, and the current becomes zero. As a result, back electromotive force is generated in the primary coil 1Np and the secondary coil 1Ns of the transformer T1, respectively.
［オフ期間：二次側］
　図６（ｂ）に示すように、オフ期間になると、トランスＴ１の二次コイル１Ｎｓ、トランスＴ２の一次コイル２Ｎｐ及び二次コイル２Ｎｓ、並びにインダクタＬの各々の両端の電位関係が反転する。第１の実施形態と同様に、ダイオードＤ２が逆バイアスとなり遮断される一方、ダイオードＤ１が順バイアスとなり導通し、図５（ｂ）に示すように電流ｉ4及び電流ｉ5が以下の経路で流れる。
　・電流ｉ4：負極出力端ｎ→ダイオードＤ１→トランスＴ２の一次コイル２Ｎｐ→正極出力端ｐ
　・電流ｉ5：負極出力端ｎ→ダイオードＤ１→トランスＴ１の二次コイル１Ｎｓ→正極出力端ｐ [Off period: Secondary side]
As shown in FIG. 6B, in the off period, the potential relationship between both ends of each of the secondary coil 1Ns of the transformer T1, the primary coil 2Np and the secondary coil 2Ns of the transformer T2, and the inductor L is inverted. Similar to the first embodiment, while the diode D2 is reverse biased and is cut off, the diode D1 is forward biased and becomes conductive, and the current i4 and the current i5 flow in the following path as shown in FIG. 5 (b).
Current i4: negative electrode output terminal n → diode D1 → primary coil 2Np of transformer T2 → positive electrode output terminal p
Current i5: negative electrode output end n → diode D1 → secondary coil 1Ns of transformer T1 → positive electrode output end p
　電流ｉ4が流れることにより、トランスＴ２にオン期間に蓄積された磁気エネルギーが、オフ期間に電力として出力される。また、電流ｉ5が流れることにより、トランスＴ１にオン期間に蓄積された磁気エネルギーが、オフ期間に電力として出力される。 When the current i4 flows, the magnetic energy stored in the on period in the transformer T2 is output as power in the off period. Further, when the current i5 flows, the magnetic energy accumulated in the on period in the transformer T1 is output as the power in the off period.
　さらに、第２の実施形態においては、ダイオードＤ３が順バイアスとなり導通し、図５（ｂ）に示すように電流ｉ6が以下の経路で流れる。
　・電流ｉ6：負極出力端ｎ→ダイオードＤ３→インダクタＬ→正極出力端ｐ Furthermore, in the second embodiment, the diode D3 is forward biased and becomes conductive, and the current i6 flows in the following path as shown in FIG. 5 (b).
· Current i6: negative electrode output terminal n → diode D3 → inductor L → positive electrode output terminal p
　第２の実施形態では、第１の実施形態よりもオフ期間の電流の経路が多い。電流が分散されることにより、各構成要素に要求される処理容量が軽減され結果的に高出力化が可能となる。 In the second embodiment, there are more current paths during the off period than in the first embodiment. By distributing the current, the processing capacity required for each component is reduced, and as a result, the output can be increased.
　１　入力端
　２　入力端
　ｐ　第１の出力端（正極出力端）
　ｎ　第２の出力端（負極出力端）
　Ｔ１、Ｔ２　トランス
　１Ｎｐ、２Ｎｐ　一次コイル
　１Ｎｓ　２Ｎｓ　二次コイル
　Ｑ　スイッチング素子（ＦＥＴ）
　Ｄ１、Ｄ２、Ｄ３　整流要素（ダイオード）
　Ｃ　コンデンサ
　Ｌ　インダクタ 1 input end 2 input end p first output end (positive electrode output end)
n Second output end (negative output end)
T1, T2 transformer 1Np, 2Np Primary coil 1Ns 2Ns Secondary coil Q switching element (FET)
D1, D2, D3 Rectifying elements (diodes)
C capacitor L inductor

Claims (2)

  1. 　（ａ）一次コイルと二次コイルを具備する第１のトランスと、
    　（ｂ）前記第１のトランスの一次コイルと直列接続されかつ制御信号によりオンオフ制御されるスイッチング素子と、
    　（ｃ）一次コイルと二次コイルを具備する第２のトランスであって、前記第１のトランスの二次コイルと該第２のトランスの一次コイルが第１の接続点及び第２の接続点により並列接続され、該第２の接続点が該第２のトランスの二次コイルの一端であると共に第１の出力端でもある、前記第２のトランスと、
    　（ｄ）第２の出力端から前記並列接続における第１の接続点へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第１の整流要素と、
    　（ｅ）第２の出力端から前記第２のトランスの二次コイルの他端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第２の整流要素と、を有することを特徴とする
    　絶縁型スイッチング電源。     (A) a first transformer comprising a primary coil and a secondary coil;
    (B) a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal;
    (C) A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point The second transformer connected in parallel, the second connection point being one end of the secondary coil of the second transformer and also the first output end;
    (D) a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction;
    (E) a second rectifying element connected to conduct a current flowing from the second output end to the other end of the secondary coil of the second transformer and to block a current in the opposite direction; An isolated switching power supply characterized by
  2. 　（ａ）一次コイルと二次コイルを具備する第１のトランスと、
    　（ｂ）前記第１のトランスの一次コイルと直列接続されかつ制御信号によりオンオフ制御されるスイッチング素子と、
    　（ｃ）一次コイルと二次コイルを具備する第２のトランスであって、前記第１のトランスの二次コイルと該第２のトランスの一次コイルが第１の接続点及び第２の接続点により並列接続され、該第２の接続点が第１の出力端である、前記第２のトランスと、
    　（ｄ）前記第２のトランスの二次コイルの一端と前記第１の出力端の間に接続されたインダクタと、
    　（ｅ）第２の出力端から前記並列接続における第１の接続点へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第１の整流要素と、
    　（ｆ）第２の出力端から前記第２のトランスの二次コイルの他端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第２の整流要素と、
    　（ｇ）第２の出力端から前記第２のトランスの二次コイルの一端へ流れる電流を導通させかつその逆向きの電流を遮断するように接続された第３の整流要素と、を有することを特徴とする
    　絶縁型スイッチング電源。     (A) a first transformer comprising a primary coil and a secondary coil;
    (B) a switching element connected in series with the primary coil of the first transformer and on / off controlled by a control signal;
    (C) A second transformer comprising a primary coil and a secondary coil, wherein the secondary coil of the first transformer and the primary coil of the second transformer are connected at a first connection point and a second connection point Connected in parallel by the second transformer, the second connection point being a first output end;
    (D) an inductor connected between one end of the secondary coil of the second transformer and the first output end;
    (E) a first rectifying element connected so as to conduct current flowing from the second output end to the first connection point in the parallel connection and block current flowing in the opposite direction;
    (F) a second rectifying element connected so as to conduct current flowing from the second output end to the other end of the secondary coil of the second transformer and block current flowing in the opposite direction;
    (G) having a third rectifying element connected to conduct current flowing from the second output end to one end of the secondary coil of the second transformer and to block current flowing in the opposite direction; Isolated switching power supply.
PCT/JP2018/045851 2017-12-13 2018-12-13 Isolated switching power supply WO2019117241A1 (en)

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