JPH0720094U - Inverter circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To make the inverter circuit smaller and cheaper. [Structure] A reactor of an AC filter of an inverter circuit is inserted into a line of an inverter circuit as a two-winding type reactor L11 wound around the same magnetic core, and a first capacitor C11 is connected in parallel to an output of an inverter unit. Further, the second capacitor C12 and the third capacitor C13
Insert a series circuit of in parallel and ground the connection point of both capacitors. As a result, the AC filter has a high frequency noise filter function of reducing both normal mode noise appearing between the output lines of the inverter circuit and common mode noise appearing between the output of the inverter circuit and the ground.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of an AC filter of an inverter circuit. The present invention relates to an inverter circuit for reducing high frequency noise of the output of an inverter circuit, that is, normal mode noise appearing between lines of the output of an inverter circuit and common mode noise appearing between the output of the inverter circuit and ground.

[0002]

[Prior art]

 The AC filter of the conventional inverter circuit has mainly the configuration shown in FIG. As shown in FIG. 2, the inverter circuit connects one end of a reactor L21 having a winding N21 to one output of the inverter unit 21, and connects a capacitor C21 to the other output of the inverter unit 21 and the other end of the reactor L21. A high-frequency noise filter 23 is connected between both ends of the capacitor C21 and the output of the inverter circuit.

FIG. 3 shows an example of the circuit configuration of the high-frequency noise filter 23. A capacitor C31 is connected in parallel with the input end, and one ends of two windings N31 and N32 of a reactor L31 are connected to both ends of this capacitor C31. Connect the capacitors C32 in parallel to the other ends of the windings N31 and N32 of the reactor L31, connect one end of the capacitors C33 and C34 to both ends of the capacitor C32, and connect the other ends of the capacitors C33 and C34. Each was grounded to form a general high-frequency noise filter.

Recently, the inverter section has adopted a high frequency PWM control method using a high speed switching element such as a power transistor, a power MOS FET, or an IGBT (Gate Insulated Bipolar Transistor) as a main semiconductor element. High-frequency noise of hundreds of tens of KHz to several tens of MHz appears significantly on the output line. If this high frequency noise is directly supplied to the load side, noise or malfunction such as malfunction may occur in the load device, so it is necessary to reduce the high frequency noise as much as possible.

In FIG. 2 showing a conventional example, of this high frequency noise, normal mode noise is reduced mainly by the AC filter 22 composed of the reactor L21 and the capacitor C21, and common mode noise is mainly reduced by the high frequency noise filter 23. It is decreasing.

[0006]

[Problems to be solved by the device]

 Regarding the high frequency noise generated in the inverter section, the AC filter 22 shown in FIG. 2 reduces normal mode noise with the reactor L21 and the capacitor C21, but since the reactor L21 is included in only one line of the output of the inverter section 21, The common mode noise that has passed through the other line of the output of the inverter section 21 that does not contain the reactor cannot be reduced, and it appears in the output of the inverter circuit as it is. In order to reduce this common mode noise, it is necessary to install a separately prepared high frequency noise filter as shown in FIG. 3, which has an attenuation characteristic for high frequency noise. For this reason, there is a problem that a device using the conventional inverter circuit as shown in FIG. 2 becomes large and expensive.

The present invention solves the above problems, and an object of the present invention is to provide an inverter circuit that can be downsized without separately providing a high-frequency noise filter.

[0008]

[Means for Solving the Problems]

 The present invention relates to an inverter circuit including an AC filter for converting the output of an inverter unit that outputs an AC voltage into a sine wave, wherein the reactor of the AC filter is a two-winding type reactor wound around the same magnetic core, The first capacitor is connected in parallel to the output of, and the series circuit of the second capacitor and the third capacitor is connected in parallel to this output, and the connection point of the second capacitor and the third capacitor is It is characterized by being grounded.

[0009]

[Action]

 The two windings of the AC filter reactor enter both the output lines of the inverter circuit, and the inductance for high frequency noise increases for each line. Together with the capacitors between the lines on the output side of the reactor, normal mode noise To reduce. Also, common mode noise is reduced together with two capacitors between each line and ground.

[0010]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an inverter circuit according to an embodiment of the present invention, which is a circuit in which an AC filter 12 is connected to an inverter unit 11 which outputs an AC voltage using a high-speed switching element. In the AC filter 12, one end of each winding of the reactor L11 in which two windings N11 and N12 are wound around the same magnetic core is connected to the output of the inverter unit 11, and the other windings of the windings N11 and N12 are connected. The end is connected to the capacitor C11 to make the output of the inverter circuit a sine wave. Further, one ends of the capacitors C12 and C13 connected in series are connected to both ends of the capacitor C11, respectively, and the connection point of the capacitors C12 and C13 is grounded. This reduces high-frequency noise (common mode noise) that appears between the output line of the inverter circuit and ground.

FIG. 4 shows a specific example of the reactor L11. For example, an iron core formed by combining two identical U-shapes and windings N41 and N42 having the same number of turns wound on the respective iron core legs. Composed of and. When the windings N41 and N42 have half the number of turns of the winding N21 of the reactance L21 of FIG. 2, the total inductance is the same in the case of the same iron core, and the reactor L11 of FIG. 1 has two windings N11 and N12. However, compared to the reactor L21 in Fig. 2, it can be manufactured with almost the same size and price.

Further, in the reactor of FIG. 4, since the windings N41 and N42 are separated from each other, they have leakage inductances that are not coupled to each other, and this reactor is used to wind the winding N12 of the reactor L11 of FIG. Even if the initial direction is opposite to the initial direction of the winding N32 of the reactor L31 of the high frequency noise filter of FIG. 3, the windings N11 and N12 of the reactor L11 of FIG. The inductance acts as an inductance against the common mode noise, and the common mode noise can be reduced together with the capacitor C12 and the capacitor C13.

If the capacitor C11 of FIG. 1 and the capacitor C21 of FIG. 2 are the same, the degree of reduction with respect to normal mode noise is the same for the AC filter 12 of FIG. 1 and the AC filter 22 of FIG. Become.

[0015]

[Effect of device]

 As described above, according to the present invention, by dividing the reactor of the AC filter into two windings and inserting each winding into each output line of the inverter circuit, each winding has impedance against high frequency noise. , Both normal mode noise and common mode noise of the output of the inverter circuit can be reduced.

As a result, it is possible to reduce the high frequency noise as a whole by using only an AC filter, which has conventionally been provided with a large and expensive high frequency noise filter, and it is possible to reduce the size and cost of the device using the inverter circuit. Became.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an inverter circuit according to the present invention.

FIG. 2 is a circuit diagram showing a conventional inverter circuit.

FIG. 3 is a circuit diagram showing an example of a high frequency noise filter.

FIG. 4 is a schematic structural view showing an example of a reactor according to the present invention.

[Explanation of symbols]

11, 21 Inverter part 12, 22 AC filter L11, L21 reactor C11-C13, C21, C31-C34 Capacitor N11, N12, N21, N31, N32, N41, N
42 winding

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Seiichi Muroyama 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Norikazu Takeuchi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo No. Japan Telegraph and Telephone Corporation (72) Inventor Yoshito Yamanishi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Isamu Kawasaki 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo No. Japan Telegraph and Telephone Corporation (72) Inventor Tetsuo Suzuki 1-15-1 Kitaotsuka, Toshima-ku, Tokyo Sanyo Electric Co., Ltd. (72) Inventor Junji Iioka 1-10-12 Ueno, Taito-ku, Tokyo No. Nippon Denki Seiki Co., Ltd. (72) Inventor Someji Inoue 1-23-11 Sengoku, Bunkyo-ku, Tokyo Shinano Denki Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. In an inverter circuit including an AC filter for converting the output of an inverter unit that outputs an AC voltage into a sine wave, the reactor of the AC filter is a two-winding reactor wound around the same magnetic core, and the inverter unit The first capacitor is connected in parallel with the output of, and the series circuit of the second capacitor and the third capacitor is connected in parallel with this output, and the connection point of the second capacitor and the third capacitor is grounded. Inverter circuit characterized by being done.