Gate drive circuit for power converter

Abstract

A gate drive circuit for a power converter, comprising: semiconductor devices connected in series; pulse transformers each comprising a primary winding and a secondary winding, wherein: the primary windings of the pulse transformers are connected in series; the secondary windings of the pulse transformers are connected directly or indirectly to the semiconductor devices, respectively; and the pulse transformers establish an insulation between a primary side and a secondary side of the pulse transformers and transfer power or power and control signals from the primary side to the secondary side; and an auxiliary winding establishing a magnetic coupling between the pulse transformers.

Description

Technical Field

[0001] This invention relates to a gate drive circuit for a power converter. Background Technology

[0002] Figure 6 The circuit configuration according to Patent Document 1 is shown. Patent Document 1 ( Figure 6 The invention discloses a gate drive circuit for a semiconductor device, configured to drive a pulse transformer 15 with an AC / DC converter 13 and a transformer drive circuit 14, thereby transmitting power for gate drive while establishing insulation.

[0003] However, Figure 6 The circuit is configured to connect the primary winding 16 of the pulse transformer 15 in series and apply a voltage to the primary winding 16. This may cause uneven excitation inductance of the pulse transformer 15, resulting in the following problems.

[0004] Uneven secondary-side voltages may increase the workload of diode bridge rectifier circuits 27, etc.

[0005] In addition, voltage imbalance applied to pulse transformer 15 may increase iron loss of pulse transformer 15, thereby increasing the size of its core.

[0006] In view of the above, it is desirable to provide a gate drive circuit for a power converter to solve the applied voltage imbalance caused by unevenness in the manufacturing of the pulse transformer.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: JP5221203B Summary of the Invention

[0010] This invention addresses the aforementioned problems in existing circuitry. According to one aspect of the invention, a gate drive circuit for a power converter includes: semiconductor devices connected in series; pulse transformers, each including a primary winding and a secondary winding, wherein the primary windings of the pulse transformers are connected in series, and the secondary windings of the pulse transformers are directly or indirectly connected to the semiconductor devices, and the pulse transformers establish insulation between the primary and secondary sides of the pulse transformers and transmit power or power and control signals from the primary side to the secondary side; and an auxiliary winding that establishes magnetic coupling between the pulse transformers.

[0011] According to another aspect, the gate drive circuit includes n-stage pulse transformers, where n is a natural number greater than or equal to 2. The first-stage pulse transformer is provided with a subsequent coupling auxiliary winding that is magnetically coupled to the subsequent pulse transformer of the first stage. Each pulse transformer, except for the first and nth stages, is provided with: a preceding coupling auxiliary winding that is magnetically coupled to the preceding pulse transformer of each stage; and a subsequent coupling auxiliary winding that is magnetically coupled to the subsequent pulse transformer of each stage. The nth-stage pulse transformer is provided with a preceding coupling auxiliary winding that is magnetically coupled to the preceding pulse transformer of the nth stage. The subsequent coupling auxiliary winding of the k-th stage pulse transformer and the preceding coupling auxiliary winding of the (k+1)-th stage pulse transformer are connected to each other, where k is one of the natural numbers from 1 to n-1.

[0012] The above aspects of the present invention are used to provide a gate drive circuit for a power converter that eliminates applied voltage imbalance caused by unevenness in the manufacturing of the pulse transformer. Attached Figure Description

[0013] Figure 1 A diagram illustrating the gate drive circuit of the power converter according to the first embodiment.

[0014] Figure 2 A timing diagram is shown to illustrate the simulation results based on Patent Document 1.

[0015] Figure 3 A timing diagram is provided to illustrate the simulation results according to the first embodiment.

[0016] Figure 4 A diagram illustrating the gate drive circuit of the power converter according to the second embodiment.

[0017] Figure 5 A diagram illustrating the gate drive circuit of a power converter according to a third embodiment.

[0018] Figure 6 A diagram illustrating the gate drive circuit of the power converter according to Patent Document 1. Detailed Implementation

[0019] The following is for reference Figures 1 to 5 The first to third embodiments of the gate drive circuit of the power converter according to the present invention are described in detail.

[0020] [First Embodiment]

[0021] Figure 1 The circuit configuration of the gate drive circuit of the power converter according to the first embodiment is illustrated.

[0022] Figure 1The diagram shows an AC power supply 1, a modulation circuit 2, pulse transformers tr1 and tr2, an auxiliary winding 3, demodulation circuits 4a and 4b, and semiconductor devices S1 and S2. Semiconductor devices S1 and S2 are connected in series, thereby achieving high voltage withstand capability.

[0023] The gate drive circuit of the power converter according to the first embodiment is an example of connecting two pulse transformers tr1 and tr2 in series.

[0024] The first-stage pulse transformer tr1 includes a primary winding tr1a and a secondary winding tr1b, and is also provided with a subsequent coupling auxiliary winding tr1c. This subsequent coupling auxiliary winding tr1c is used to establish magnetic coupling with the subsequent pulse transformer tr2.

[0025] The second-stage pulse transformer tr2 includes a primary winding tr2a and a secondary winding tr2b, and is also provided with a pre-stage coupling auxiliary winding tr2d. This pre-stage coupling auxiliary winding tr2d is used to establish magnetic coupling with the pre-stage pulse transformer tr1.

[0026] In pulse transformers tr1 and tr2, the primary windings tr1a and tr2a are connected in series, and the secondary windings tr1b and tr2b are indirectly connected to semiconductor devices S1 and S2 via demodulation circuits 4a and 4b, respectively. Pulse transformers tr1 and tr2 establish insulation between the primary and secondary sides of pulse transformers tr1 and tr2, and transmit power or power and control signals from the primary side to the secondary side.

[0027] The subsequent coupling auxiliary winding tr1c and the preceding coupling auxiliary winding tr2d are connected to each other, thereby forming auxiliary winding 3. Auxiliary winding 3 establishes magnetic coupling between pulse transformers tr1 and tr2. Furthermore, reference numeral i1 indicates the current flowing in the primary windings tr1a and tr2a. Reference numeral i2 indicates the current flowing in auxiliary winding 3.

[0028] When the magnetizing inductance between pulse transformers tr1 and tr2 is uneven, resulting in a voltage difference between them, current i2 flows through auxiliary winding 3. This balances the voltage applied to pulse transformers tr1 and tr2. The effect of auxiliary winding 3 can be proven using the following mathematical expression.

[0029] The following mathematical expressions (1) and (2) represent the voltage vtr1 applied to pulse transformer tr1 and the voltage vtr2 applied to pulse transformer tr2, respectively. In these expressions, L1 is the self-inductance of pulse transformer tr1, M1 is the mutual inductance between pulse transformer tr1 and the subsequent coupling auxiliary winding tr1c, L2 is the self-inductance of pulse transformer tr2, and M2 is the mutual inductance between pulse transformer tr2 and the preceding coupling auxiliary winding tr2d.

[0030] [Mathematical Expression 1]

[0031]

[0032] [Mathematical Expression 2]

[0033]

[0034] The following mathematical expressions (3) and (4) represent the mutual inductances M1 and M2, respectively. In them, L3 is the self-inductance of the subsequent coupling auxiliary winding tr1c set for pulse transformer tr1, k1 is the magnetic coupling coefficient between pulse transformer tr1 and subsequent coupling auxiliary winding tr1c, L4 is the self-inductance of the preceding coupling auxiliary winding tr2d set for pulse transformer tr2, and k2 is the magnetic coupling coefficient between pulse transformer tr2 and preceding coupling auxiliary winding tr2d.

[0035] [Mathematical Expression 3]

[0036]

[0037] [Mathematical Expression 4]

[0038]

[0039] The following mathematical expression (5) represents the voltage equation in the auxiliary winding 3 derived from Kirchhoff's laws.

[0040] [Mathematical Expression 5]

[0041]

[0042] Then, assuming that the turns ratio between the primary winding tr1a of pulse transformer tr1 and the subsequent coupling auxiliary winding tr1c is equal to the turns ratio between the primary winding tr2a of pulse transformer tr2 and the preceding coupling auxiliary winding tr2d, and that magnetic coupling is ideally established (i.e., coupling coefficients k1, k2 = 1), then equations L3 = L1 and L4 = L2 are satisfied. Therefore, satisfying equations M1 = L1 and M2 = L2, mathematical expression (5) can be transformed into the following mathematical expression (6).

[0043] [Mathematical Expression 6]

[0044]

[0045] Substituting mathematical expressions (1) and (2) into mathematical expression (6), we obtain the following mathematical expression (7). This shows that even if the excitation inductance values ​​are different between pulse transformer tr1 and pulse transformer tr2, the auxiliary winding 3 can still make the voltages applied to pulse transformer tr1 and tr2 equal.

[0046] [Mathematical Expression 7]

[0047] vtr1=vtr2……(7)

[0048] Figure 2 The simulation results based on Patent Document 1 are shown. Figure 3 Simulation results according to the first embodiment are shown. These simulation results are for the case where pulse transformers tr1 and tr2 are connected in series and an inductance difference of 27.5% is set between pulse transformers tr1 and tr2.

[0049] Figure 3 The simulation results show that the voltage Vtr1 of pulse transformer tr1 and the voltage Vtr2 of pulse transformer tr2 have essentially the same waveform. This indicates that the auxiliary winding 3 is used to equalize the voltages applied to pulse transformers tr1 and tr2, and the above mathematical expression is correct.

[0050] (Effect)

[0051] In the first embodiment, an auxiliary winding 3 is configured between pulse transformers tr1 and tr2, whose primary windings are connected in series, thereby establishing magnetic coupling with pulse transformers tr1 and tr2. Even if the excitation inductance between pulse transformers tr1 and tr2 is uneven due to manufacturing unevenness, this ensures that the voltage applied to pulse transformers tr1 and tr2 is evenly distributed.

[0052] This achieves the following effects (1) and (2).

[0053] (1) The iron loss of pulse transformers tr1 and tr2 is reduced, thereby reducing the size of their cores.

[0054] (2) It can level out and reduce the load on secondary-side circuit components. This helps improve reliability or enables the use of low-duty circuit components, thereby reducing costs.

[0055] Compared to existing pulse transformers, the first embodiment additionally includes an auxiliary winding, and the core size can be reduced due to the reduced iron loss of the pulse transformer.

[0056] This is because, regardless of whether it is based on existing technology or the first embodiment, circuits using pulse transformers are configured to maintain a sufficient distance between the primary and secondary sides to ensure insulation distance, and then use low-turn windings for both the primary and secondary windings. This allows for the addition of approximately one auxiliary winding close to the secondary winding without affecting the dimensions.

[0057] Therefore, the first embodiment helps to reduce the size of the pulse transformer, and thereby reduce the size of the power converter.

[0058] [Second Embodiment]

[0059] Figure 4 The circuit configuration of the gate drive circuit of the power converter according to the second embodiment is shown. The second embodiment illustrates an example in which three semiconductor devices S1, S2, and S3 are connected in series and three pulse transformers tr1, tr2, and tr3 are also connected in series. Corresponding to the three semiconductor devices S1, S2, and S3 and the three pulse transformers tr1, tr2, and tr3, three demodulation circuits 4a, 4b, and 4c are also provided.

[0060] The first-stage pulse transformer tr1 has a primary winding tr1a and a secondary winding tr1b, and is also equipped with a subsequent coupling auxiliary winding tr1c. The subsequent coupling auxiliary winding tr1c is used to establish magnetic coupling with the subsequent pulse transformer tr2.

[0061] The second-stage pulse transformer TR2 includes a primary winding TR2a and a secondary winding TR2b, and is also equipped with a pre-stage coupling auxiliary winding TR2d and a post-stage coupling auxiliary winding TR2c. The pre-stage coupling auxiliary winding TR2d is used to establish magnetic coupling with the pre-stage pulse transformer TR1. The post-stage coupling auxiliary winding TR2c is used to establish magnetic coupling with the post-stage pulse transformer TR3.

[0062] The third-stage pulse transformer TR3 includes a primary winding TR3a and a secondary winding TR3b, and is also equipped with a pre-stage coupling auxiliary winding TR3d. The pre-stage coupling auxiliary winding TR3d is used to establish magnetic coupling with the pre-stage pulse transformer TR2.

[0063] The auxiliary coupling winding tr1c for the first-stage pulse transformer tr1 and the auxiliary coupling winding tr2d for the second-stage pulse transformer tr2 are connected to each other. Additionally, the auxiliary coupling winding tr2c for the second-stage pulse transformer tr2 and the auxiliary coupling winding tr3d for the third-stage pulse transformer tr3 are connected to each other.

[0064] The subsequent coupling auxiliary winding TR1c and the preceding coupling auxiliary winding TR2d are connected to each other, thus forming auxiliary winding 3a. The subsequent coupling auxiliary winding TR2c and the preceding coupling auxiliary winding TR3d are connected to each other, thus forming auxiliary winding 3b. Auxiliary winding 3a establishes magnetic coupling between pulse transformers TR1 and TR2. Auxiliary winding 3b establishes magnetic coupling between pulse transformers TR3 and TR4.

[0065] The second-stage pulse transformer tr2 is coupled to the auxiliary windings of the first-stage pulse transformer tr1 and the third-stage pulse transformer tr3, which allows the voltage applied to the pulse transformers tr1 and tr3, whose auxiliary windings are not directly coupled, to be balanced.

[0066] Current i1 flows through the primary windings tr1a to tr3a of the pulse transformer tr1 to tr3, current i2 flows through the auxiliary winding 3a, and current i3 flows through the auxiliary winding 3b.

[0067] When the magnetizing inductances of pulse transformers tr1 to tr3 are uneven, resulting in a difference in the voltage applied to pulse transformers tr1 to tr3, current flows through auxiliary windings 3a and 3b. This balances the voltage applied to pulse transformers tr1 to tr3. This effect of auxiliary windings 3a and 3b can be proven using the following mathematical expression.

[0068] The following mathematical expressions (8), (9) and (10) represent the voltage vtr1 applied to pulse transformer tr1, the voltage vtr2 applied to pulse transformer tr2, and the voltage vtr3 applied to pulse transformer tr3, respectively, where: L1 is the self-inductance of pulse transformer tr1, M1 is the mutual inductance between pulse transformer tr1 and the subsequent coupling auxiliary winding tr1c, L2 is the self-inductance of pulse transformer tr2, M2 is the mutual inductance between pulse transformer tr2 and the preceding coupling auxiliary winding tr2d, M3 is the mutual inductance between pulse transformer tr2 and the subsequent coupling auxiliary winding tr2c, L3 is the self-inductance of pulse transformer tr3, and M4 is the mutual inductance between pulse transformer tr3 and the preceding coupling auxiliary winding tr3d.

[0069] [Mathematical Expression 8]

[0070]

[0071] [Mathematical Expression 9]

[0072]

[0073] [Mathematical Expression 10]

[0074]

[0075] The following mathematical expressions (11), (12), (13), (14), and (15) represent the mutual inductance M1 between pulse transformer tr1 and the subsequent coupling auxiliary winding tr1c, the mutual inductance M2 between pulse transformer tr2 and the preceding coupling auxiliary winding tr2d, the mutual inductance M3 between pulse transformer tr2 and the subsequent coupling auxiliary winding tr2c, the mutual inductance M4 between pulse transformer tr3 and the preceding coupling auxiliary winding tr3d, and the mutual inductance M5 between auxiliary winding 3a and auxiliary winding 3b, respectively. Where: L4 is the self-inductance of the subsequent coupling auxiliary winding tr1c set for pulse transformer tr1, and k1 is the mutual inductance between pulse transformer tr1 and the subsequent coupling auxiliary winding tr2c. The magnetic coupling coefficient between r1c, L5 is the self-inductance of the pre-stage coupling auxiliary winding tr2d for pulse transformer tr2, k2 is the magnetic coupling coefficient between pulse transformer tr2 and the pre-stage coupling auxiliary winding tr2d, L6 is the self-inductance of the post-stage coupling auxiliary winding tr2c for pulse transformer tr2, k3 is the magnetic coupling coefficient between pulse transformer tr2 and the post-stage coupling auxiliary winding tr2c, L7 is the self-inductance of the pre-stage coupling auxiliary winding tr3d for pulse transformer tr3, k4 is the magnetic coupling coefficient between pulse transformer tr3 and the pre-stage coupling auxiliary winding tr3d, and k5 is the magnetic coupling coefficient between auxiliary winding 3a and auxiliary winding 3b.

[0076] [Mathematical Expression 11]

[0077]

[0078] [Mathematical Expression 12]

[0079]

[0080] [Mathematical Expression 13]

[0081]

[0082] [Mathematical Expression 14]

[0083]

[0084] [Mathematical Expression 15]

[0085]

[0086] The following mathematical expressions (16) and (17) represent the voltage equations in auxiliary winding 3a and auxiliary winding 3b, respectively, derived from Kirchhoff's laws.

[0087] [Mathematical Expression 16]

[0088]

[0089] [Mathematical Expression 17]

[0090]

[0091] Then, assuming that the turns ratio between the primary winding tr1a and the subsequent coupling auxiliary winding tr1c of pulse transformer tr1, the turns ratio between the primary winding tr2a and the preceding coupling auxiliary winding tr2d of pulse transformer tr2, the turns ratio between the primary winding tr2a and the subsequent coupling auxiliary winding tr2c of pulse transformer tr2, and the turns ratio between the primary winding tr3a and the preceding coupling auxiliary winding tr3d of pulse transformer tr3 are all equal, and that magnetic coupling is ideally established (i.e., coupling coefficients k1 = k2 = k3 = k4 = k5 = 1), then the equations L4 = L1, L5 = L2, L6 = L2, and L7 = L3 are satisfied. Therefore, satisfying the equations M1=L1, M2=L2, M3=L2, M4=L3 and M5=L2, the mathematical expressions (8), (9), (10), (16) and (17) can be transformed into the following mathematical expressions (18), (19), (20), (21) and (22), respectively.

[0092] [Mathematical Expression 18]

[0093]

[0094] [Mathematical Expression 19]

[0095]

[0096] [Mathematical Expression 20]

[0097]

[0098] [Mathematical Expression 21]

[0099]

[0100] [Mathematical Expression 22]

[0101]

[0102] Substituting mathematical expressions (18) and (19) into mathematical expression (21), we obtain the following mathematical expression (23).

[0103] [Mathematical Expression 23]

[0104] vtr1=vtr2……(23)

[0105] Substituting mathematical expressions (19) and (20) into mathematical expression (22), we obtain the following mathematical expression (24).

[0106] [Mathematical Expression 24]

[0107] vtr2=vtr3……(24)

[0108] This indicates that even when the excitation inductance values ​​of pulse transformers tr1, tr2, and tr3 are different from each other, the auxiliary windings 3a and 3b according to the second embodiment can make the voltages vtr1, vtr2, and vtr3 applied to pulse transformers tr1, tr2, and tr3 equal.

[0109] Therefore, the above example of connecting three pulse transformers tr1, tr2 and tr3 in series also has the same effect as the first embodiment.

[0110] [Third Embodiment]

[0111] Figure 5 The circuit configuration of the gate drive circuit of the power converter according to the third embodiment is shown. The third embodiment illustrates a case in which n semiconductor devices S1 to Sn are connected in series and n pulse transformers tr1 to trn are connected in series, where n is any natural number greater than 2. Corresponding to the n semiconductor devices S1 to Sn and the n pulse transformers tr1 to trn, n demodulation circuits 4a to 4n are also provided.

[0112] The first-stage pulse transformer tr1 includes a primary winding tr1a and a secondary winding tr1b, and is also provided with a subsequent coupling auxiliary winding tr1c that establishes magnetic coupling with the subsequent pulse transformer tr2.

[0113] Each pulse transformer tr2 to trn-1 between stage 1 and stage n includes a primary winding and a secondary winding, and is also provided with a front-stage coupling auxiliary winding that establishes magnetic coupling with the preceding pulse transformer and a rear-stage coupling auxiliary winding that establishes magnetic coupling with the following pulse transformer.

[0114] The nth stage pulse transformer trn includes a primary winding trna and a secondary winding trnb, and is also equipped with a front-stage coupling auxiliary winding trnd that establishes magnetic coupling with the preceding stage pulse transformer trn-1.

[0115] Thus, the auxiliary winding of the k-th stage pulse transformer is connected to the auxiliary winding of the (k+1)-th stage pulse transformer, where k is one of the natural numbers from 1 to n-1. In other words, any pulse transformer except for the 1st and nth stages is connected to both the auxiliary windings of the upper and lower stage pulse transformers.

[0116] The first embodiment corresponds to the case where n=2, and there is no pulse transformer between the first stage and the nth stage.

[0117] The second embodiment corresponds to the case where n=3, and there is a pulse transformer tr2 between the first stage and the nth stage.

[0118] According to the third embodiment, when the excitation inductance of the pulse transformer is uneven, resulting in a difference in the voltage applied to the pulse transformer, current flows through the auxiliary winding. This balances the voltage applied to the pulse transformer. Details of these operations are similar to those in the first and second embodiments and are therefore omitted.

[0119] The above only explains the specific examples described herein in detail. It will be apparent to those skilled in the art that various changes and modifications can be made to the above details within the scope of the inventive concept. Such changes and modifications naturally fall within the scope of these claims.

Claims

1. A gate drive circuit for a power converter, comprising series-connected semiconductor devices, characterized in that it includes: Multiple pulse transformers, wherein primary windings are connected in series, and secondary windings are directly or indirectly connected to each of the semiconductor devices, the primary and secondary sides are insulated, and power, or power and control signals, are transmitted from the primary side to the secondary side; and An auxiliary winding is used to magnetically couple the plurality of pulse transformers to each other, wherein, The gate drive circuit has n stages of the pulse transformer, where n is a natural number greater than or equal to 2. The first-stage pulse transformer is provided with a subsequent-stage coupling auxiliary winding for establishing magnetic coupling with the subsequent-stage pulse transformer. The pulse transformer between the first stage and the nth stage is provided with a front-stage coupling auxiliary winding for establishing magnetic coupling with the preceding pulse transformer and a rear-stage coupling auxiliary winding for establishing magnetic coupling with the following pulse transformer. The nth stage pulse transformer is provided with a pre-stage coupling auxiliary winding for establishing magnetic coupling with the preceding stage pulse transformer. The subsequent coupling auxiliary winding of the pulse transformer at stage k and the preceding coupling auxiliary winding of the pulse transformer at stage (k+1) are connected, where k is a natural number from 1 to n-1.

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