Ripple current cancellation device

Abstract

To provide a ripple current cancellation device that can be retrofitted to a DC / DC converter. The ripple current canceling device 2 according to the present invention includes a magnetic coupling portion L C a terminal S1 connected to one end of the coil 22 via a capacitor C1, a terminal S2 connected to the other end of the coil 23 via a capacitor C2, a terminal S3 commonly connected to the other end of the coil 22 and one end of the coil 23, and an auxiliary inductance L inserted between the one end of the coil 23 and the terminal S3. S Including,

Description

[Technical field]

[0001] The present invention relates to a ripple current cancellation device. [Background technology]

[0002] The ripple current superimposed on the output current of a switching power supply can cause increased noise, reduced efficiency, excess heat generation, electromagnetic interference with other devices, etc. Therefore, in conventional switching power supplies, many measures have been taken to minimize the ripple current.

[0003] Non-Patent Document 1 discloses an example of such a device. In the switching power supply of this document, a ripple current cancellation circuit including a coupling reactor and an auxiliary inductor is installed in parallel with the output inductor. In this way, the ripple current can be reduced. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Michael J. Schutten et al., "Ripple Current Cancellation Circuit," IEEE (Institute of Electrical and Electronics Engineers) Xplore, February 19, 2003, pp. 464-470 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when implementing the ripple current cancellation circuit described in Non-Patent Document 1, a configuration as shown in Fig. 4 has been used up until now. That is, a coil 101 separate from the output inductor L1 is wound around a toroidal core 100 that constitutes the winding core of the output inductor L1, and the coil 101 and the output inductor L1 form a coupled reactor. The symbols in Fig. 4 (excluding the toroidal core 100 and the coil 101) are based on the example in Non-Patent Document 1.

[0006] However, with the configuration shown in Figure 4, the switching power supply has to have a built-in ripple current cancellation circuit, so the switching power supply must be designed to include the ripple current cancellation circuit. Therefore, there has been a demand for a ripple current cancellation circuit that can be retrofitted to a switching power supply.

[0007] The above circumstances are the same for any DC / DC converter (power conversion device) including a switching power supply. Therefore, one of the objects of the present invention is to provide a ripple current cancellation device that can be retrofitted to a DC / DC converter. [Means for solving the problem]

[0008] The ripple current cancellation device according to the present invention is a ripple current cancellation device including a first coil and a second coil constituting a magnetic coupling portion, a first terminal connected to one end of the first coil via a first capacitor, a second terminal connected to the other end of the second coil via a second capacitor, a third terminal commonly connected to the other end of the first coil and one end of the second coil, and an auxiliary inductance inserted between one end of the second coil and the third terminal. Effect of the Invention

[0009] According to the ripple current cancellation device of the present invention, it is possible to provide a ripple current cancellation device that can be retrofitted to a DC / DC converter. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing configurations of a switching power supply 1 and a ripple current cancellation device 2 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the coils shown in FIG. 1 using circuit symbols. [Diagram 3]3 is a diagram showing the results of a simulation of currents i1 to i3 and a current iL shown in FIG. 1 and FIG. 2. [Figure 4] 1 is a diagram showing the configuration of a switching power supply according to the background art of the present invention and a ripple current cancellation circuit built therein; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0012] Fig. 1 is a diagram showing the configuration of a switching power supply 1 and a ripple current cancellation device 2 according to this embodiment. Fig. 2 is a diagram showing the coils shown in Fig. 1 in circuit symbols. These figures also show a DC power supply 3 and a load 4 connected to the switching power supply 1. The load 4 is, for example, a battery for an electric vehicle or a solar power generation system.

[0013] As shown in FIG. 1 and FIG. 2, the switching power supply 1 includes a full-bridge circuit 10 and an output reactor L L and the output capacitor C out The switching power supply 1 is a DC / DC converter having six terminals T1 to T6 as external terminals. Among these, the terminals T1 and T2 are input terminals of the switching power supply 1, and are connected to a high-side terminal and a low-side terminal of the DC power supply 3, respectively. The terminals T3 and T4 are output terminals of the switching power supply 1, and are connected to a high-side terminal and a low-side terminal of the load 4, respectively. The terminals T5 and T6 will be described later.

[0014] The full-bridge circuit 10 includes four switches S1A, S2A, S1B, and S2B. Each of the switches S1A, S2A, S1B, and S2B is a unidirectional switch including a semiconductor element such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT), and a diode connected in parallel with the semiconductor element. The on / off states of the switches S1A, S2A, S1B, and S2B are controlled by a control device (not shown).

[0015] The switches S1A and S2A correspond to a first leg of the full-bridge circuit 10, and the switches S1B and S2B correspond to a second leg of the full-bridge circuit 10. In addition, the switches S1A and S1B correspond to an upper arm of the full-bridge circuit 10, and the switches S2A and S2B correspond to a lower arm of the full-bridge circuit 10.

[0016] The high-side input terminal of the full-bridge circuit 10 is connected to a terminal T1, and the low-side input terminal is connected to a terminal T2. The output terminal of the first leg of the full-bridge circuit 10 is connected to an output reactor L L and the output end of the second leg of the full-bridge circuit 10 is connected to a terminal T4.

[0017] Output reactor L L is an inductor connected between the output end of the first leg of the full bridge circuit 10 and the terminal T3, and serves to reduce the ripple current in the output voltage and improve the stability of the output voltage. L The inductance of "L L As shown in Figure 1, the output reactor L L The output capacitor C can be constructed by winding a coil 12 around a core 11. Although FIG. 1 shows an example in which the core 11 is a toroidal core, the core 11 may be a core other than a toroidal core. outis a capacitor connected between terminal T3 and terminal T4, which serves to reduce ripple current and noise in the output voltage and improve the stability of the output voltage.

[0018] Output reactor L L The input and output ends of the output reactor L are connected to terminals T5 and T6, respectively. L In the following explanation, the output reactor L L The connection point between the wiring connecting the output end of the output terminal of the output terminal T1 and the terminal T2 is called node n1, and the output reactor L L The current flowing from node n1 to terminal T3 is i1, and the current flowing from node n1 to terminal T3 is i L It is called.

[0019] The ripple current cancellation device 2 is a magnetic coupling part L C and the auxiliary inductance L S and capacitors C1 and C2. The ripple current cancellation device 2 also has three terminals S1 to S3 as external terminals. The terminals S1, S2, and S3 are connected to the terminals T5, T6, and T4 of the switching power supply 1, respectively.

[0020] Magnetic coupling part L C is a coupling reactor or transformer formed by in-phase coupling of two coils 22 and 23, and the two coils 22 and 23 are connected to an output reactor L L The inductance L m is the magnetic coupling part L C 1 shows an example of the core 21 being a toroidal core, but it may be a core other than a toroidal core. The number of turns of the coils 22 and 23 is n p ,n s The core 21 is made of, for example, Finemet (registered trademark), which is a nanocrystalline soft magnetic core material.

[0021] One end of the coil 22 is connected to a terminal S1 via a capacitor C1. The other end of the coil 23 is connected to a terminal S2 via a capacitor C2. The other end of the coil 22 and one end of the coil 23 are commonly connected to a terminal S3. More specifically, the other end of the coil 22 is connected to a node n2 provided midway along a wire connecting one end of the coil 23 to the terminal S3. Hereinafter, the current flowing from the other end of the coil 22 to the node n2 is referred to as i2, and the current flowing from the other end of the coil 23 to the node n2 is referred to as i3.

[0022] The capacitors C1 and C2 are provided to block overcurrent (DC component) that may occur during startup or a transient state of the switching power supply 1 from flowing into the ripple current cancellation device 2. The capacitor C2 is connected to the magnetic coupling portion L C The purpose of the capacitor C1 is to block the inflow of an overcurrent from the secondary side of the MOSFET, and it is also used in the ripple current cancellation circuit according to the background art shown in FIG. 4 (capacitor C2). On the other hand, the capacitor C1 is C This is to block the inflow of an overcurrent from the primary side of the ripple current canceling device 2 according to the present embodiment, and is a characteristic configuration of the ripple current canceling device 2 according to the present embodiment. L and magnetic coupling part L C are electrically connected but are separate coils, so the inductance L L and the excitation inductance L m Depending on the balance of the magnetic coupling part L C There is a possibility that an overcurrent may flow into the ripple current cancellation device 2 from not only the secondary side but also the primary side. C It is necessary to provide a capacitor C1 on the primary side of the inverter.

[0023] An auxiliary inductance L is provided between one end of the coil 23 and the terminal S3 (more specifically, between one end of the coil 23 and the node n2). S This auxiliary inductance L S Typically, the magnetic coupling part LC However, by implementing an inductor as an element, the auxiliary inductance L S The auxiliary inductance L S The specific value of the magnetizing inductance L m , inductance L L , and the magnetic coupling portion L C This is determined based on the turns ratio of the coil. This will be explained in detail below.

[0024] The condition under which the ripple current in the output voltage of the switching power supply 1 becomes zero is expressed by the following equation (1) using the above-mentioned currents i1 to i3.

[0025]

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[0026] In addition, the magnetic coupling part L C The AC component of the primary voltage v p is the output reactor L L The AC component of the voltage across both ends v L Therefore, it is expressed as the following equation (2). However, L on the right side of equation (2) p is the composite inductance expressed by equation (3).

[0027]

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[0028] Magnetic coupling part L C The AC component of the primary voltage v p is the magnetic coupling part L C The AC component of the secondary voltage v s It can also be expressed as the following formula (4): where N in formula (4) is the magnetic coupling part L C and the number of turns of the coil 22 is n p The number of turns of coil 23 is n s Divide by n p / n sIt becomes.

number

[0029] From equations (2) and (4), the following equation (5) is obtained.

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[0030] Furthermore, the current i2 and the current i3 satisfy the following equation (6).

[0031]

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[0032] Substituting equations (5) and (6) into equation (1) gives equation (7), which can be rearranged to give the auxiliary inductance L S can be expressed as equation (8). The auxiliary inductance L S By determining the above, the ripple current of the switching power supply 1 can be suitably reduced.

[0033]

number

[0034] FIG. 3 shows currents i1 to i3 and current i L The simulation in FIG. 14 shows the results of the simulation of the auxiliary inductance L S The figure also shows a current i2+i3 obtained by adding together the currents i2 and i3.

[0035] As shown in FIG. 3, a triangular ripple current having a peak-to-peak amplitude of about 10 A is superimposed on the current i1. LIn the state shown in FIG. 3, the ripple current is significantly reduced, and only a small amount of ripple current remains. Looking at the current i2+i3 shown in FIG. 3, it can be seen that such a reduction in the ripple current is achieved because the current i2+i3 is in opposite phase to the ripple current of the current i1 and has a peak-to-peak amplitude of about 10 A. From this simulation result, it can be said that the ripple current of the switching power supply 1 can be significantly reduced by using the ripple current cancellation device 2 according to this embodiment.

[0036] As described above, the ripple current canceling device 2 according to this embodiment can be retrofitted to the switching power supply 1 by connecting the terminals S1, S2, and S3 to the terminals T5, T6, and T4 of the switching power supply 1, respectively. S The magnetic coupling part L C The excitation inductance L m , output reactor L L Inductance L L , and the magnetic coupling portion L C It is possible to significantly reduce the ripple current of the switching power supply 1 by determining the winding number ratio N based on the winding number ratio N of the winding number ratio N. Therefore, it can be said that the ripple current cancellation device 2 according to the present embodiment makes it possible to provide a ripple current cancellation device that can be retrofitted to the switching power supply 1.

[0037] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0038] For example, in the above embodiment, an example has been described in which the ripple current cancellation device 2 according to the present invention is connected to a switching power supply 1 for use, but the ripple current cancellation device according to the present invention can be connected to any DC / DC converter (power conversion device) including a switching power supply 1 for use. [Explanation of symbols]

[0039] 1 Switching power supply 2 Ripple current cancellation device 3 DC power supply 4. Load 10 Full-bridge circuit 11,21 cores 12,22,23 Coil C1, C2 capacitors C out Output Capacitor L C Magnetic coupling L S Auxiliary Inductance L L Output Reactor L m Excitation Inductance N Turn ratio S1~S3 terminals S1A, S2A, S1B, S2B Switches T1~T6 terminals

Claims

1. a first coil and a second coil that constitute a magnetic coupling portion; a first terminal connected to one end of the first coil via a first capacitor; a second terminal connected to the other end of the second coil via a second capacitor; a third terminal commonly connected to the other end of the first coil and one end of the second coil; an auxiliary inductance inserted between one end of the second coil and the third terminal; Including, the first terminal is connected to an input end of an output reactor of a switching power supply; the third terminal is connected to an output end of an output reactor of the switching power supply; The second terminal is connected to a low-side output end of the switching power supply. Ripple current cancellation device.

2. The first coil and the second coil are wound around a core that does not constitute a magnetic core of the output reactor.

2. The ripple current cancellation device according to claim 1.

3. The auxiliary inductance L Ｓ is the excitation inductance L of the magnetic coupling portion ｍ , the inductance L of the output reactor L and a turn ratio N of the magnetic coupling portion obtained by dividing the number of turns of the first coil by the number of turns of the second coil, expressed by Equation (1):

3. A ripple current canceling device according to claim 1 or 2.

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