Flyback power supply circuit and inverter device

Abstract

To provide a flyback power supply circuit capable of reducing the size of multiple transformers and the size of switching elements that control the current flowing through the primary side winding of each transformer.SOLUTION: In a flyback power supply circuit, a power supply for driving six semiconductor switching elements that constitute a three-phase inverter circuit is generated by multiple transformers (2, 12, 32) having primary windings (3, 33) and secondary windings (4, 34, 35). The primary windings of the plurality of transformers are connected in series. A control unit (9) controls a semiconductor switch (5) that turns on and off the current flowing through the primary windings from the input power supply.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flyback power supply circuit that generates power for driving each semiconductor switch element that constitutes a three-phase inverter, and to an inverter device including the power supply circuit. [Background technology]

[0002] For example, Patent Document 1 discloses a flyback power supply that uses six or three transformers to generate power for driving each semiconductor switching element that makes up a three-phase inverter, and connects the primary windings of these transformers in parallel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6817298 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the primary windings of multiple transformers are connected in parallel, the current flowing through the switching element increases by a factor of several times the number of parallel connections, which necessitates the size of the switching element to be increased. The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a flyback power supply circuit that can reduce the size of multiple transformers and the size of switching elements that control the current flowing through the primary windings of these transformers, and an inverter device including the power supply circuit. [Means for solving the problem]

[0005] According to the flyback power supply circuit of claim 1, the power supply for driving six semiconductor switching elements constituting a three-phase inverter circuit (42) is generated by a plurality of transformers (2, 12, 32) having primary windings (3, 33) and secondary windings (4, 34, 35). The primary windings of the plurality of transformers are connected in series. A control unit (9) controls a semiconductor switch (5) that turns on and off the current flowing from the input power supply to the primary winding.

[0006] In this way, by connecting the primary windings of multiple transformers in series, the inductance per transformer is reduced, which makes it possible to reduce the size of the transformer. Also, the current flowing through the switching element via the primary winding is reduced, which makes it possible to reduce the size of the switching element.

[0007] According to the flyback power supply circuit of claim 2, a transformer (12) having auxiliary windings (13) is used, one end of each auxiliary winding is commonly connected to ground, and input terminals of a plurality of rectifier elements (14(1)-14(6)) are connected to the other ends of each auxiliary winding. One end of a capacitor (15) is connected to an output terminal of the plurality of rectifier elements, and the other end is connected to ground. With this configuration, when the current flowing through the secondary winding of the transformer increases, the current flowing through the auxiliary winding decreases accordingly. Therefore, even if there is a variation in the current flowing through the load, the variation in each output voltage can be suppressed.

[0008] According to the flyback power supply circuit of claim 3, a transformer (12) having auxiliary windings (13) is used, one end of each auxiliary winding is commonly connected to ground, and an input terminal of one rectifier element (14) is connected to the other end of each auxiliary winding. One end of a capacitor (15) is connected to the output terminal of the rectifier element, and the other end is connected to ground. With this configuration, the number of rectifier elements can be reduced more than in claim 2.

[0009] According to an inverter device of claim 8, the inverter device includes a three-phase inverter circuit and the flyback power supply circuit (1, 11, 16, 21) of any one of claims 1 to 3, and the number of transformers (2, 12) is six. If the three phases are U-phase, V-phase, and W-phase, on a circuit board (41) on which the three-phase inverter circuit is mounted, the connection order of the primary windings of each transformer is the input power supply, U-phase upper arm, V-phase upper arm, W-phase upper arm, W-phase lower arm, V-phase lower arm, U-phase lower arm, and semiconductor switch. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a configuration of a flyback power supply circuit in a first embodiment; [Diagram 2] FIG. 1 shows a configuration of a flyback power supply circuit in a second embodiment. [Diagram 3] FIG. 13 is a diagram showing a configuration of a flyback power supply circuit in a third embodiment. [Figure 4] FIG. 1 is a diagram showing a load current variation and an output voltage variation in a flyback power supply circuit according to a first embodiment; [Diagram 5] FIG. 11 is a diagram showing the load current variation and the output voltage variation in the flyback power supply circuits of the second and third embodiments. [Figure 6] FIG. 13 is a diagram showing a model circuit for explaining the effects of the second and third embodiments. [Figure 7] FIG. 7 is a diagram showing voltage and current waveforms on the primary and secondary sides of a transformer with respect to variations in load current when the circuit shown in FIG. 6 employs the first embodiment. [Figure 8] This diagram shows the voltage and current waveforms on the primary and secondary sides of the transformer in response to load current variations in the circuit shown in Figure 6. [Figure 9] FIG. 13 is a diagram showing a configuration of a flyback power supply circuit in a fourth embodiment. [Figure 10] FIG. 13 is a diagram showing a configuration of a flyback power supply circuit in a fifth embodiment. [Figure 11] FIG. 13 is a diagram showing a configuration of a flyback power supply circuit in a sixth embodiment. [Figure 12]FIG. 13 is a diagram showing how wiring is arranged between six transformers on a circuit board when the flyback power supply circuit of the first to fourth embodiments is applied to an inverter device in a seventh embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) As shown in Fig. 1, the flyback power supply circuit 1 of this embodiment is applied to an inverter circuit configured by connecting six power semiconductor switching elements, such as power MOSFETs or IGBTs, in a three-phase bridge configuration, and generates a power supply for driving the gates of each semiconductor switching element. For this purpose, the flyback power supply circuit 1 uses six transformers 2(1) to 2(6). The transformer 2 has a primary winding 3 and a secondary winding 4.

[0012] A series circuit of the primary windings 3(1)-3(6) of six transformers 2(1)-2(6) and a semiconductor switch, for example an N-channel MOSFET 5, is connected between the input power supply Vin and ground. A rectifier circuit 8 consisting of a series circuit of a diode 6 and a capacitor 7 is connected between each of the secondary windings 4(1)-4(6). A DC voltage is output from both ends of the capacitor 7. This output voltage is supplied as a drive power supply to a drive circuit that drives the gates of each semiconductor switching element that constitutes the inverter circuit.

[0013] The gate of the FET 5 is driven by a control unit 9. The control unit 9 monitors one of the output voltages and controls the on / off of the FET 5 so that the output voltage becomes a predetermined voltage. A control voltage VCC for operation is supplied to the control unit 9. For example, the input voltage is about 100V to 1000V, the control voltage VCC is about 10V to 20V, and the output voltage of the flyback power supply circuit 1 is about 20V to 30V.

[0014] The flyback power supply circuit 1 of this embodiment configured as above has the following advantages. By connecting the primary windings 3(1)-3(6) of the six transformers 2(1)-2(6) in series, the inductance of each transformer 2 is reduced, and the transformer 2 can be made smaller. Also, compared to the configuration in which the primary windings of multiple transformers are connected in parallel as in Patent Document 1, the current flowing through the primary winding 3 is smaller. Therefore, the size of the FET 5 can also be reduced.

[0015] Second embodiment Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and only the different parts will be described. As shown in FIG. 2, the flyback power supply circuit 11 of the second embodiment uses transformers 12(1)-12(6) instead of the transformers 2(1)-2(6). The transformer 12 includes an auxiliary winding 13 in addition to a primary winding 3 and a secondary winding 4. One end of each of the auxiliary windings 13(1)-13(6) is commonly connected to the ground, and the other end is connected to the input terminals (anodes) of the diodes 14(1)-14(6) which are rectifying elements, respectively. The output terminals (cathodes) of the diodes 14(1)-14(6) are connected to a common connection point between the control power supply VCC and one end of the capacitor 15. The other end of the capacitor 15 is connected to the ground.

[0016] Here, assuming that the number of turns of the primary winding 3 is Np, the number of turns of the secondary winding 4 is Ns, and the number of turns of the auxiliary winding 13 is Naux, it is preferable to set Np, Ns > Naux. This allows the size of the transformer 12 to be further reduced. According to the second embodiment configured as above, even if the load current varies, the variation in the output voltage can be suppressed, and this effect will be described in the third embodiment.

[0017] Third embodiment 3, the flyback power supply circuit 16 of the third embodiment uses only one diode 14, and the other ends of the auxiliary windings 13(1) to 13(6) are commonly connected to the anode of the diode 14. With this configuration, the number of diodes 14 can be reduced compared to the flyback power supply circuit 11 of the second embodiment.

[0018] Next, the operation of the second and third embodiments will be described. As shown in Fig. 4, in the flyback power supply circuit 1 of the first embodiment, when the current flowing through the load varies, the output voltage also varies accordingly. In contrast, as shown in Fig. 5, in the flyback power supply circuits 11 and 16 of the second and third embodiments, even if the load current varies, there is almost no variation in the output voltage. This principle will be described using a model using two transformers 12(1) and 12(2) shown in Fig. 6.

[0019] In the above model, a configuration is assumed in which the primary windings 3(1) and 3(2) are simply connected in series as in the first embodiment. In this case, the power supplied to the primary windings 3(1) and 3(2) is the same, and the energy propagated to the secondary side is also the same. Therefore, as shown in FIG. 7, if the load currents Io1 and Io2 vary, the output voltages Vout1 and Vout2 will also vary. In the example shown in the figure, Io1<Io2になることでVout1> It is Vout2.

[0020] In contrast, when the auxiliary windings 13(1) and 13(2) are provided as in the second embodiment, the energy excited on the primary side is distributed to the secondary winding 4 and the auxiliary winding 13. Therefore, as shown in FIG. 8, when the load current Io2 becomes larger, the current Is2 flowing through the secondary winding 4(2) becomes larger than the current Is1. Accordingly, the current Iaux2 flowing through the auxiliary winding 13(2) becomes smaller than the current Iaux1. As a result, the variation in the output voltage Vout2 is suppressed.

[0021] In Patent Document 1, the primary windings are connected in parallel on the assumption that there is little variation in the load connected to the secondary side of the transformer. Therefore, when there is variation in the load on the secondary side, the secondary output voltage of the flyback power supply will vary. Patent Document 1 also describes feedback control of any one of the secondary output voltages, but in order to suppress the variation, feedback control of all three phases is required.

[0022] In contrast, according to the second and third embodiments, the output voltage variations can be suppressed by using a transformer 12 having auxiliary windings 13, connecting the primary windings 3 in series, connecting one end of each auxiliary winding 13 to ground, and connecting the other end in parallel via diodes 14(1) to 14(6) or commonly connecting them to the anode of one diode 14. In this case, the control unit 9 may perform feedback control by monitoring the terminal voltage of the capacitor 15.

[0023] (Fourth embodiment) As shown in Fig. 9, a flyback power supply circuit 21 of the fourth embodiment has a configuration in which a voltage averaging circuit 22 is added to the flyback power supply circuit 1 of the first embodiment. The output voltages from the rectifier circuits 8(4) to 8(6) are input to the voltage averaging circuit 22. If the three phases are U, V, and W, respectively, and the output voltages from the rectifier circuits 8(1) to 8(6) are U-phase to W-phase upper arm power supplies and U-phase to W-phase lower arm power supplies, respectively, as shown in the figure, the voltages of the U-phase to W-phase lower arm power supplies are input to the voltage averaging circuit 22.

[0024] In the voltage averaging circuit 22, for example, the input three-phase voltages are averaged by applying them to a common capacitor via respective resistive elements, and the control unit 9 controls the on / off of the FET 5 based on the averaged voltage. According to the fourth embodiment configured as above, the control unit 9 controls the switching of the FET 5 based on the three-phase voltages averaged by the voltage averaging circuit 22, so that the variation in the output voltage of the flyback power supply circuit 21 can be further suppressed.

[0025] Fifth embodiment As shown in FIG. 10, a flyback power supply circuit 31 of the fifth embodiment uses three transformers 32(1) to 32(3). The transformer 32 includes a primary winding 33 and two secondary windings 34 and 35. The three primary windings 33(1) to 33(3) are connected in series as in each embodiment. Rectifier circuits 8(1) to 8(6) are connected to secondary windings 34(1), 35(1) to 34(3), and 35(3) of the transformers 32(1) to 32(3), respectively. The output voltages of the rectifier circuits 8(1) to 8(6) are assigned to the U- to W-phase upper arm power supplies and the U- to W-phase lower arm power supplies as in the fourth embodiment.

[0026] According to the fifth embodiment configured as above, six driving power sources can be generated using three transformers 32(1) to 32(3), so that the number of transformers used can be reduced.

[0027] Sixth embodiment As shown in FIG. 11, in the flyback power supply circuit 36 ​​of the sixth embodiment, three transformers 32(1)-32(3) are used like the flyback power supply circuit 31 of the fifth embodiment, but the secondary windings 35(1)-35(3) are connected in parallel to the rectifier circuit 8(6). The rectifier circuits 8(2) and 8(4) are deleted. A series circuit of a coil 37(1) and a capacitor 38(1), and a series circuit of a coil 37(2) and a capacitor 38(2) are connected in parallel to the anode of the diode 6 constituting the rectifier circuit 8(6). The output voltage from the rectifier circuit 8(6) is supplied as the power supply for the U-phase lower arm, and the output voltages from the capacitors 38(1) and 38(2) are supplied as the power supplies for the V- and W-phase lower arms, respectively.

[0028] According to the sixth embodiment configured as described above, the secondary windings 35(1) to 35(3) of the transformers 32(1) to 32(3) are connected in parallel to the rectifier circuit 8(6) and power for the U-, V-, and W-phase lower arms is branched and supplied therefrom, thereby making it possible to further reduce the number of parts.

[0029] Seventh embodiment In the seventh embodiment, any one of the flyback power supply circuits 1, 11, 16, and 21 using six transformers 2 or 12 as in the first to fourth embodiments is applied to an inverter device. As shown in Fig. 12, six semiconductor switching elements are mounted on a circuit board 41 to configure an inverter circuit 42. The six frames shown in the figure indicate the areas where the semiconductor switching elements are mounted, and correspond to the U- to W-phase upper arms and the U- to W-phase lower arms, respectively.

[0030] For example, in the case of a flyback power supply circuit 1, the primary windings 3(1)-3(6) of six transformers 2(1)-2(6) are connected linearly from left to right in the order U→V→W on the upper arm side between the input power supply Vin located at the upper left in the figure and the SW element and FET 5 located at the lower left in the figure, in accordance with the arrangement of the six semiconductor switching elements. When the W-phase upper arm is turned back to the lower arm side, the lower arm side is connected linearly from right to left in the order U←V←W. In addition, a snubber circuit 43 is connected between the input power supply Vin and FET 5. The above constitutes an inverter device 44.

[0031] According to the seventh embodiment configured as described above, when the flyback power supply circuit 1 and the like are mounted on the circuit board 41 constituting the inverter device 44, the wiring connecting the primary windings 3(1)-3(6) of the six transformers 2(1)-2(6) in series can be routed as short as possible.

[0032] This application also includes the following inventions. [1] A power supply for driving six semiconductor switching elements constituting a three-phase inverter circuit (42) is generated. A plurality of transformers (2, 12, 32) each having a primary winding (3, 33) and a secondary winding (4, 34, 35); a semiconductor switch (5) for turning on and off a current flowing from an input power source to the primary winding; A control unit (9) for controlling the on / off of the semiconductor switch; a rectifier circuit (8) connected to the secondary winding, A flyback power supply circuit in which the primary windings of multiple transformers are connected in series. [2] The transformer (12) has an auxiliary winding (13), One end of each auxiliary winding is commonly connected to ground; a plurality of rectifier elements (14(1) to 14(6)) whose input terminals are connected to the other ends of the respective auxiliary windings; a capacitor (15) having one end connected to output terminals of the plurality of rectifier elements and the other end connected to ground. [3] The transformer (12) has an auxiliary winding (13), One end of each auxiliary winding is commonly connected to ground; a rectifier element (14) having an input terminal commonly connected to the other end of each auxiliary winding; a capacitor (15) having one end connected to the output terminal of the rectifier element and the other end connected to ground. "4" The flyback power supply circuit according to [2] or [3], wherein the number of turns of the auxiliary winding is set to be smaller than the number of turns of the primary winding and the secondary winding. [5] The number of the transformers (32) is three, The flyback power supply circuit according to any one of [1] to [4], wherein the transformers each have two secondary windings (34, 35). [6] [5] A flyback power supply circuit as described in [5], in which one of the secondary windings of each transformer is connected in parallel. [7] The flyback power supply circuit according to any one of [1] to [6], wherein the control unit monitors output voltages for a plurality of phases and feedback-controls the on / off of the semiconductor switch. [8] The three-phase inverter circuit; A flyback power supply circuit (1, 11, 16, 21) according to any one of [1] to [4], The number of the transformers (2, 12) is six, If the three phases are U phase, V phase, and W phase, An inverter device in which, on a circuit board (41) on which the three-phase inverter circuit is mounted, the connection order of the primary windings of each of the transformers is an input power supply, a U-phase upper arm, a V-phase upper arm, a W-phase upper arm, a W-phase lower arm, a V-phase lower arm, a U-phase lower arm, and the semiconductor switch.

[0033] (Other embodiments) The semiconductor switching elements are not limited to power MOSFETs and IGBTs. Semiconductor switching is not limited to N-channel MOSFETs. The relationship between the number of turns Np of the primary winding 3, the number of turns Ns of the secondary winding 4, and the number of turns Naux of the auxiliary winding 13 does not necessarily need to be set such that Np, Ns>Naux. In the fourth embodiment, the number of transformers 2 for which the output voltage is averaged may be equal to or greater than 2. Moreover, it is not always necessary to average a plurality of output voltages.

[0034] The specific voltage values ​​may be changed as appropriate depending on the individual design. The embodiments that can be combined can be implemented in appropriate combinations. Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0035] In the drawing, 1 indicates a flyback power supply circuit, 2 indicates a transformer, 3 indicates a primary winding, 4 indicates a secondary winding, 5 indicates an N-channel MOSFET, 6 indicates a diode, 7 indicates a capacitor, 8 indicates a rectifier circuit, and 9 indicates a control unit.

Claims

1. A power supply for driving six semiconductor switching elements constituting a three-phase inverter circuit (42) is generated, a plurality of transformers (2, 12, 32) each having a primary winding (3, 33) and a secondary winding (4, 34, 35); a semiconductor switch (5) for turning on and off a current flowing from an input power source to the primary winding; A control unit (9) for controlling the on / off of the semiconductor switch; a rectifier circuit (8) connected to the secondary winding, A flyback power supply circuit in which the primary windings of multiple transformers are connected in series.

2. The transformer (12) has an auxiliary winding (13), One end of each auxiliary winding is commonly connected to ground; A plurality of rectifying elements (14(1) to 14(6)) whose input terminals are connected to the other ends of the respective auxiliary windings; 2. The flyback power supply circuit according to claim 1, further comprising: a capacitor (15) having one end connected to the output terminals of the plurality of rectifying elements and the other end connected to ground.

3. The transformer (12) has an auxiliary winding (13), One end of each auxiliary winding is commonly connected to ground; A rectifier element (14) having an input terminal commonly connected to the other end of each auxiliary winding; 2. The flyback power supply circuit according to claim 1, further comprising: a capacitor (15) having one end connected to the output terminal of the rectifier element and the other end connected to ground.

4. 4. The flyback power supply circuit according to claim 2, wherein the number of turns of said auxiliary winding is set to be smaller than the number of turns of said primary winding and said secondary winding.

5. The number of the transformers (32) is three, 2. The flyback power supply circuit of claim 1, wherein said transformers each have two secondary windings (34, 35).

6. 6. The flyback power supply circuit according to claim 5, wherein one of the secondary windings of each transformer is connected in parallel.

7. 2. The flyback power supply circuit according to claim 1, wherein the control unit monitors output voltages for a plurality of phases and performs feedback control of turning on and off the semiconductor switch.

8. The three-phase inverter circuit; A flyback power supply circuit (1, 11, 16, 21) according to any one of claims 1 to 3, The number of the transformers (2, 12) is 6, If the three phases are U-phase, V-phase, and W-phase, An inverter device in which, on a circuit board (41) on which the three-phase inverter circuit is mounted, the connection order of the primary windings of each of the transformers is an input power supply, a U-phase upper arm, a V-phase upper arm, a W-phase upper arm, a W-phase lower arm, a V-phase lower arm, a U-phase lower arm, and the semiconductor switch.

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