Transformer direct current magnetic bias feedback device, converter and method

Abstract

The invention provides a transformer direct-current magnetic bias feedback device, a converter and a method, the transformer direct-current magnetic bias feedback device is applied to the converter, a transformer in the converter comprises a magnetic core, the transformer direct-current magnetic bias feedback device comprises a magnetic bias detection module, and the magnetic bias detection module comprises an auxiliary magnetic circuit, a current detection unit and a signal processing module. The auxiliary magnetic circuit comprises an auxiliary magnet and a short-circuited auxiliary winding, the auxiliary winding is wound on the auxiliary magnet, and the auxiliary magnetic circuit is arranged on the surface or the edge of the magnetic core; the current detection unit is connected with the auxiliary winding and is configured to obtain degaussing current flowing through the auxiliary winding; and the signal processing module is connected with the current detection unit and is configured to obtain a direct current magnetic bias value of the transformer based on the degaussing current. By applying the device provided by the invention, the hardware volume can be saved, and the detection cost of the direct current magnetic bias of the related transformer can be effectively reduced while the magnetic bias value of the transformer can be effectively detected.

Description

Technical Field

[0001] This application belongs to the field of power electronics, and particularly relates to a transformer DC bias feedback device, a converter, and a method. Background Art

[0002] Isolated converters are widely used in power electronic systems. They achieve energy conversion between input and output through electromagnetic coupling of transformers, and at the same time provide electrical isolation functions. However, in an isolated active bridge topology, the transformer may generate DC current bias during operation. When these DC biases accumulate to a certain extent, it will cause magnetic core saturation, which will have a fatal impact on the entire circuit. Common methods to suppress the DC bias of transformers are as Figure 1 and Figure 2 shown by connecting a DC-blocking capacitor in series in the main circuit. However, when the current in the main circuit is large, the DC-blocking capacitor will generate significant losses, reducing the conversion efficiency. The current in the main circuit will also generate a certain voltage drop across the DC-blocking capacitor, which will cause the working state of the circuit to shift, increasing the control difficulty. And this method will also greatly increase the volume and cost of the circuit. Summary of the Invention

[0003] Embodiments of this application provide a transformer DC bias feedback device and a converter, aiming to solve the problems of high detection difficulty and high cost of transformer DC bias in related converters.

[0004] To solve the above technical problems, a first aspect of an embodiment of this application provides a transformer DC bias feedback device, which is applied to a converter. It is characterized in that the transformer in the converter includes two symmetrically arranged magnetic cores. The transformer DC bias feedback device includes a bias detection module. The bias detection module includes an auxiliary magnetic circuit, a current detection unit, and a signal processing module. The auxiliary magnetic circuit includes an auxiliary magnet and a short-circuited auxiliary winding. The auxiliary winding is wound around the auxiliary magnet. The auxiliary magnetic circuit is arranged on the surface or edge of the magnetic core;

[0005] The current detection unit is connected to the auxiliary winding and is configured to obtain the demagnetizing current flowing through the auxiliary winding;

[0006] The signal processing module is connected to the current detection unit and is configured to obtain the transformer DC bias value based on the demagnetizing current.

[0007] In one embodiment, the signal processing module includes a band-pass filtering unit, a peak detection unit, and a bias value acquisition unit;

[0008] The band-pass filtering unit is connected to the current detection unit and is configured to obtain a first voltage signal based on the demagnetizing current and output the first voltage signal to the peak detection unit;

[0009] The peak detection unit is connected to the band-pass filtering unit, and is configured to obtain a second voltage signal based on the first voltage signal and output the second voltage signal to the bias magnetic value acquisition unit;

[0010] The bias magnetic value acquisition unit is connected to the peak detection unit, and is configured to obtain the transformer DC bias magnetic value from the second voltage signal based on a preset conversion coefficient.

[0011] In one embodiment, the transformer DC bias magnetic feedback device further includes a bias magnetic control module, and the bias magnetic control module includes a voltage processing unit and a compensation unit;

[0012] The signal processing module is further configured to generate a third voltage signal representing the transformer DC bias magnetic value and output the third voltage signal to the voltage processing unit;

[0013] The voltage processing unit is connected to the signal processing module, and is configured to generate a fourth voltage signal based on a preset voltage and the third voltage signal and output the fourth voltage signal to the compensation unit;

[0014] The compensation unit is connected to the voltage processing unit, and is configured to generate a compensation signal based on the fourth voltage signal and output the compensation signal to the switching tube in the converter.

[0015] In one embodiment, the primary side of the transformer includes a first bridge arm and / or a second bridge arm; wherein, the first bridge arm includes a first switching tube and a second switching tube with two complementary PWMs, and the second bridge arm includes a third switching tube and a fourth switching tube with two complementary PWMs;

[0016] The compensation unit is further configured to generate a first compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a first compensation signal based on the first compensation value, and output the first compensation signal to the first switching tube and the second switching tube; wherein, the expression of the duty ratio change amount of the first switching tube caused by the first compensation signal is q1 = △D1, and the expression of the duty ratio change amount of the second switching tube caused by the first compensation signal is q2 = -△D1;

[0017] The compensation unit is further configured to generate a second compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a second compensation signal based on the second compensation value, and output the second compensation signal to the third switching tube and the fourth switching tube; wherein, the expression of the duty ratio change amount of the third switching tube caused by the second compensation signal is q3 = △D2, and the expression of the duty ratio change amount of the fourth switching tube caused by the second compensation signal is q4 = -△D2.

[0018] In one embodiment, the secondary side of the transformer includes a third bridge arm and / or a fourth bridge arm; wherein, the third bridge arm includes a fifth switch and a sixth switch with complementary PWMs, and the fourth bridge arm includes a seventh switch and an eighth switch with complementary PWMs;

[0019] The compensation unit is further configured to generate a third compensation value of the duty ratio of the switch drive based on the fourth voltage signal, generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and output the third compensation signal to the fifth switch and the sixth switch; wherein, the expression of the change in the duty ratio of the fifth switch caused by the third compensation signal is q5 = x * △D3, and the expression of the change in the duty ratio of the sixth switch caused by the third compensation signal is q6 = -1 * x * △D3;

[0020] The compensation unit is further configured to generate a fourth compensation value of the duty ratio of the switch drive based on the fourth voltage signal, generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and output the fourth compensation signal to the seventh switch and the eighth switch; wherein, the expression of the change in the duty ratio of the seventh switch caused by the fourth compensation signal is q7 = x * △D4, and the expression of the change in the duty ratio of the eighth switch caused by the fourth compensation signal is q8 = -1 * x * △D4.

[0021] In one embodiment, the compensation unit is further configured to simultaneously generate any plurality of the first compensation signal, the second compensation signal, the third compensation signal, and the fourth compensation signal and output them to the corresponding switches for compensation respectively.

[0022] In one embodiment, the transformer DC bias feedback device further includes a bias warning module;

[0023] The bias detection module is further configured to output the transformer DC bias value to the bias warning module;

[0024] The bias warning module is configured to compare the transformer DC bias value with a preset DC bias maximum threshold and a preset DC bias minimum threshold, and send a warning signal to the processor when the transformer DC bias value is greater than the preset DC bias maximum threshold or less than the preset DC bias minimum threshold.

[0025] The second aspect of the present application provides a converter, including a transformer and the transformer DC bias feedback device as described in any one of the above. The transformer includes a magnetic core, and a groove is provided on the surface or edge of the magnetic core. The auxiliary magnet is disposed in the groove, and the auxiliary winding is wound around the auxiliary magnetic path. The auxiliary magnet and the auxiliary winding together form the auxiliary magnetic path; wherein, the magnetic core and the corresponding groove are of an integrally formed structure, or the groove is of a carved structure.

[0026] The third aspect of the present application provides a converter, including a transformer and the transformer DC bias feedback device as described in any one of the above. The transformer includes a magnetic core, and the auxiliary magnet having a convex ear-shaped structure is provided on the surface of the magnetic core. The auxiliary winding is wound around the auxiliary magnet, and the auxiliary magnet and the auxiliary winding together form the auxiliary magnetic path; wherein, the magnetic core and the corresponding auxiliary magnet are connected by an adhesive, or the magnetic core and the corresponding auxiliary magnet are of an integrally formed structure.

[0027] In one embodiment, the auxiliary magnet and the transformer DC bias feedback device are of an integrally encapsulated structure, and the integrally encapsulated structure is connected to the magnetic core through the convex via an adhesive.

[0028] The fourth aspect of the present application provides a method for transformer DC bias feedback, which is applied to a converter. The transformer in the converter includes a magnetic core, and the transformer DC bias feedback device includes a bias detection module. The bias detection module includes an auxiliary magnetic path, a current detection unit, and a signal processing module. The auxiliary magnetic path includes an auxiliary magnet and a short-circuited auxiliary winding. The auxiliary winding is wound around the auxiliary magnet. The auxiliary magnetic path is disposed on the surface or edge of the magnetic core. The current detection unit is connected to the auxiliary winding, and the signal processing module is connected to the current detection unit. The method includes:

[0029] The current detection unit obtains the demagnetizing current flowing through the auxiliary winding;

[0030] The signal processing module obtains the transformer DC bias value based on the demagnetizing current.

[0031] The transformer DC bias feedback device provided by the embodiments of the present application sets an auxiliary magnet and an auxiliary winding together as an auxiliary magnetic path on the magnetic core of the transformer in a relevant converter. By detecting the demagnetizing current passing through the auxiliary magnetic path and performing coefficient conversion, the DC bias value of the transformer magnetic core can be obtained. The embodiments of the present application abandon the DC-blocking capacitor in the main circuit, can save the hardware volume in a large-current scenario, and have low hardware costs. While effectively detecting the transformer bias value, the detection cost of the relevant transformer DC bias can also be effectively reduced. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the related art or in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the related art or the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, rather than all embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a schematic circuit diagram of a unidirectional transmission isolation type converter in the related art with a DC blocking capacitor connected in series in the main circuit;

[0034] Figure 2 It is a schematic circuit diagram of a bidirectional transmission isolation type converter in the related art with a DC blocking capacitor connected in series in the main circuit;

[0035] Figure 3 It is a schematic structural diagram of a transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0036] Figure 4 It is a schematic diagram of the auxiliary magnetic circuit structure provided in the first aspect of the embodiments of the present application;

[0037] Figure 5 It is the schematic principle diagram of the auxiliary magnetic circuit provided in the first aspect of the embodiments of the present application

[0038] Figure 6 It is a schematic structural diagram of a refined transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0039] Figure 7 It is a schematic structural diagram of a transformer DC bias feedback device provided in the first aspect of the embodiments of the present application applied to a unidirectional isolation bridge type DC-DC converter;

[0040] Figure 8 It is a schematic structural diagram of a transformer DC bias feedback device provided in the first aspect of the embodiments of the present application applied to a bidirectional isolation bridge type DC-DC converter;

[0041] Figure 9 It is a schematic structural diagram of another refined transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0042] Figure 10 It is a circuit structure diagram of a transformer DC bias feedback device provided in the first aspect of the embodiments of the present application applied to a unidirectional isolation bridge type DC-DC converter;

[0043] Figure 11A magnetic bias suppression timing diagram provided in the first aspect of the embodiment of the present application;

[0044] Figure 12 A circuit structure diagram of a transformer DC bias feedback device applied to a bidirectional isolation bridge type DC-DC converter provided in the first aspect of the embodiment of the present application;

[0045] Figure 13 Another magnetic bias suppression timing diagram provided in the first aspect of the embodiment of the present application;

[0046] Figure 14 A partial structural schematic diagram of an auxiliary magnetic circuit in a converter provided in the second aspect of the embodiment of the present application;

[0047] Figure 15 Another partial structural schematic diagram of an auxiliary magnetic circuit in a converter provided in the second aspect of the embodiment of the present application;

[0048] Figure 16 A partial structural schematic diagram of an auxiliary magnetic circuit in a converter provided in the third aspect of the embodiment of the present application;

[0049] Figure 17 A flow schematic diagram of a transformer DC bias feedback method provided in the fourth aspect of the embodiment of the present application. Detailed implementation manners

[0050] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0051] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0052] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0053] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means one or more than one, unless otherwise specifically defined.

[0054] Figure 3 FIG. 4 shows a schematic structural diagram of a transformer DC bias feedback device provided in the first aspect of the embodiments of this application. For ease of description, only the parts related to this embodiment are shown and are described in detail as follows:

[0055] In this embodiment, the transformer DC bias feedback device is applied to a converter. The transformer in the converter includes two symmetrically arranged magnetic cores. The transformer DC bias feedback device includes a bias detection module 10. The bias detection module includes an auxiliary magnetic circuit 101, a current detection unit 102, and a signal processing module 103. The auxiliary magnetic circuit includes an auxiliary magnet 1011 and a short-circuited auxiliary winding 1012. The auxiliary winding 1012 is wound around the auxiliary magnet 1011. The auxiliary magnetic circuit 101 is arranged on the surface or edge of the magnetic core;

[0056] The current detection unit 102 is connected to the auxiliary winding 1012 and is configured to obtain the demagnetizing current flowing through the auxiliary winding 1012;

[0057] The signal processing module 103 is connected to the current detection unit 103 and is configured to obtain the transformer DC bias value based on the demagnetizing current.

[0058] Specifically, the hardware costs of chip-level current sensors, integrated-level current sensors, or the combination of shunts and isolation op amps used for current sampling of transformers are relatively high, and the sizes of power magnetic devices in the industry, such as inductors and transformers, are relatively large. At this volume level, using a small part of its magnetic core as an auxiliary magnetic circuit and leading out an auxiliary winding to enable it to have the function of detecting the exciting current, the exciting current of the transformer can be detected at a relatively small volume and cost. Then, separating the information of the DC component contained in the exciting current can obtain the DC bias value of the transformer.

[0059] In detail, Figure 4 FIG. 5 is a schematic structural diagram of the auxiliary magnetic circuit provided in the first aspect of this embodiment, Figure 5 FIG. 6 is a schematic principle diagram of the auxiliary magnetic circuit provided in the first aspect of this embodiment. In the figure, since a short-circuited winding is wound on the auxiliary magnetic circuit, a demagnetizing current will flow through this winding, and the magnetomotive force generated by it is denoted as F2. This demagnetizing current makes the auxiliary magnetic flux Φ2≈0 on the auxiliary magnetic circuit, and Φ≈Φ1; therefore, the demagnetizing current magnetomotive force F2 and the magnetomotive force F at both ends of the magnetic resistance R m1 at both ends of the magnetic resistance Rm1 Equal

[0060] The reluctance on the main magnetic path is only related to the magnetic path length. Assuming the length of the hanging part is l, and the length of the main magnetic path is k times the length of the hanging part, then:

[0061] R m1 +R m31 +R m32 = k·R m1

[0062] At this time, the relationship between the demagnetizing current magnetomotive force F2 and the exciting current electromotive force F can be calculated as:

[0063]

[0064] When the exciting current is referred to the primary side, the exciting current electromotive force F = N1·i m ; the demagnetizing current magnetomotive force F2 = N·i aux , where N is the number of turns of the auxiliary winding, and N1 is the number of turns of the primary side of the transformer;

[0065] Finally, the relationship between the current of the short-circuit winding of the auxiliary magnetic path and the exciting current can be obtained as:

[0066]

[0067] It can be understood that the structure of the auxiliary magnetic path for detection can be constructed on the surface or edge of the existing magnetic core by methods such as windowing or grooving; if it is not desired to damage the original shape of the magnetic core (main magnetic path), an additional ear-shaped structure can also be cast or engraved on the surface of the magnetic core to construct the auxiliary magnetic path, and even the ear-shaped structure can be added to the surface of the magnetic core by means of glue pasting; the size of the auxiliary magnetic path can be determined according to actual needs. Preferably, the transformer usually has two magnetic cores joined together, and a columnar structure separated from the main magnetic core can be cast or engraved at the joint of the two magnetic cores. Both ends of the columnar structure are connected to the main magnetic core, but it is suspended in the middle. The embodiments of the present application do not make specific limitations here.

[0068] Furthermore, there is an auxiliary winding with N turns wound in the above magnetic structure and the winding is short-circuited. When the transformer is operating, the current in the auxiliary winding is proportional to the exciting current value. By measuring the current value of the auxiliary winding and then performing proportional conversion, the exciting current value of the transformer can be obtained. Since the exciting current value can represent the magnetic core magnetic density value and has a certain mapping relationship, the DC bias value of the transformer can ultimately be obtained from the DC component value of the exciting current.

[0069] In Figure 3Based on the provided transformer DC bias feedback device, this embodiment further provides a schematic structural diagram of a refined transformer DC bias feedback device. For details, please refer to Figure 6 , in some embodiments, the signal processing module 103 includes a band-pass filtering unit 1031, a peak detection unit 1032, and a bias magnetic value acquisition unit 1033;

[0070] The band-pass filtering unit 1031 is connected to the current detection unit 102 and is configured to obtain a first voltage signal based on the demagnetizing current and output the first voltage signal to the bias magnetic value acquisition unit;

[0071] The peak detection unit 1032 is connected to the band-pass filtering unit 1031 and is configured to obtain a second voltage signal based on the first voltage signal and output the second voltage signal to the bias magnetic value acquisition unit 1033;

[0072] The bias magnetic value acquisition unit 1033 is connected to the peak detection unit 1032 and is configured to obtain the transformer DC bias magnetic value from the second voltage signal based on a preset conversion coefficient.

[0073] Specifically, after the current detection unit detects the demagnetizing current in the auxiliary magnetic circuit, a voltage signal representing the current value is obtained and provided to the subsequent circuit. The first voltage signal is obtained through the processing of the band-pass filtering unit, and then the DC component thereof, that is, the second voltage signal, is obtained through the processing of the peak detection unit. Among them, the band-pass filtering unit is preferably a double switching frequency narrow-band band-pass filter, and the second voltage signal is a voltage signal representing the DC component in the exciting current. Then, the bias magnetic value acquisition unit processes the second voltage signal according to the preset conversion coefficient to finally obtain the transformer DC bias magnetic value.

[0074] As Figure 7 shown is a schematic structural diagram of a transformer DC bias feedback device provided by an embodiment of the present application applied to a unidirectional isolation bridge type DC-DC converter. As Figure 8The figure shows a schematic structural diagram of a transformer DC bias feedback device provided in this embodiment applied to a bidirectional isolated bridge-type DC-DC converter. It should be understood that in some alternative embodiments, the unidirectional isolated bridge-type DC-DC converter adopts a phase-shifted full-bridge converter, and the bidirectional isolated bridge-type DC-DC converter adopts a dual-active bridge converter (DAB). In some embodiments, the auxiliary magnetic circuit 101 is composed of the auxiliary magnet and the auxiliary winding provided by the transformer DC bias feedback device of this embodiment itself, or the auxiliary winding of the device itself and an additional auxiliary magnet assembled with the magnetic core of the transformer in the converter. In other embodiments, the auxiliary magnetic circuit 101 is constructed by methods such as windowing or grooving on the surface or edge of the existing magnetic core. When assembling this device onto the magnetic core, it is only necessary to ensure that the auxiliary winding is correctly wound around the auxiliary magnet. This embodiment does not make specific limitations here.

[0075] Based on the Figure 6 transformer DC bias feedback device provided, this embodiment also provides another schematic structural diagram of a refined transformer DC bias feedback device. For details, please refer to Figure 9 , in some embodiments, it further includes a bias control module 20, and the bias control module includes a voltage processing unit 201 and a compensation unit 202;

[0076] The signal processing module 103 is further configured to generate a third voltage signal representing the DC bias value of the transformer and output the third voltage signal to the voltage processing unit 201;

[0077] The voltage processing unit 201 is connected to the signal processing module 103 and is configured to generate a fourth voltage signal based on a preset voltage and the third voltage signal, and output the fourth voltage signal to the compensation unit;

[0078] The compensation unit 202 is connected to the voltage processing unit 201 and is configured to generate a compensation signal based on the fourth voltage signal and output the compensation signal to the switching tube in the converter.

[0079] Specifically, after detecting the DC bias of the transformer, the DC bias can also be suppressed through the bias control module. First, the signal processing module outputs the third voltage signal representing the DC bias of the transformer to the voltage processing unit. The voltage processing unit subtracts the third voltage signal from the preset voltage to obtain a fourth voltage signal. Then, the compensation unit generates a compensation value for the driving duty cycle of the switching tube based on the fourth voltage signal and sends the compensation signal to the corresponding switching tube in the converter, so as to generate a volt-second product opposite to the existing core bias on the primary or secondary side of the transformer, suppressing and then eliminating the bias of the transformer core.

[0080] It can be understood that the preset voltage in the voltage processing unit is usually 0. In actual applications, the preset voltage can also be preset to other values to achieve special functions. For example, if it is predicted that a large positive bias magnetic field will be generated in some cases, the value of the preset voltage can be adjusted in advance, so that the bias magnetic field of the transformer is adjusted negatively in advance to enhance the resistance of the system to the positive bias magnetic field in this case. The preset voltage here can be flexibly set based on actual applications, and no specific limitation is made here in this embodiment.

[0081] Based on Figure 9 the provided transformer DC bias magnetic feedback device, this embodiment also provides a circuit structure diagram of the transformer DC bias magnetic feedback device. For details, please refer to Figure 10 , in some embodiments, the primary side of the transformer includes a first bridge arm B1, and the first bridge arm B1 includes two complementary PWM first switching tubes Q11 and Q12;

[0082] The compensation unit 202 is further configured to generate a first compensation value of the switching tube drive duty cycle based on the fourth voltage signal, generate a first compensation signal based on the first compensation value, and output the first compensation signal to the first switching tube Q11 and the second switching tube Q12; wherein, the expression of the duty cycle change amount of the first switching tube Q11 caused by the first compensation signal is q1 = △D1, and the expression of the duty cycle change amount of the second switching tube Q12 caused by the first compensation signal is q2 = -△D1.

[0083] In some embodiments, the primary side of the transformer further includes a second bridge arm B2, and the second bridge arm B2 includes two complementary PWM third switching tubes Q13 and Q14;

[0084] The compensation unit 202 is further configured to generate a second compensation value of the switching tube drive duty cycle based on the fourth voltage signal, generate a second compensation signal based on the second compensation value, and output the second compensation signal to the third switching tube Q13 and the fourth switching tube Q14; wherein, the expression of the duty cycle change amount of the third switching tube Q13 caused by the second compensation signal is q3 = △D2, and the expression of the duty cycle change amount of the fourth switching tube Q14 caused by the second compensation signal is q4 = -△D2.

[0085] In some embodiments, the primary side of the transformer includes the first bridge arm B1 and the second bridge arm B2, and the compensation unit 202 is further configured to generate the first compensation signal and the second compensation signal simultaneously and output them to the corresponding switching tubes respectively.

[0086] Specifically, in this solution, the bias magnetic state of the transformer core is detected by the bias magnetic detection module, and after signal processing in the bias magnetic control module, the duty cycle adjustment amount for the switching tubes of each arm is obtained, the duty cycle of the switching tubes of each arm is adjusted, and a volt-second product opposite to the bias magnetic direction of the core is generated, finally canceling the DC bias in the transformer. In the same arm, the upper and lower tubes are complementary PWM. Therefore, when the duty cycle of the upper tube changes by ΔD, the lower tube changes by -1 * ΔD. As Figure 10 shown in the embodiment, the converter is a unidirectional isolated H-bridge DC-DC converter. For a unidirectional isolated H-bridge DC-DC converter, the compensation can be ΔD1 of the first arm, ΔD2 of the second arm, either one of them or both compensated simultaneously.

[0087] Among them, the bias magnetic suppression effect can be illustrated by the timing diagram as Figure 11 shown. In the timing diagram, G xx is the drive signal of each switching tube; φ y1 is the phase shift angle between the two arms on the primary side. Taking the direction of the magnetic flux generated by the exciting current flowing into the same-named terminal as positive as an example, if it is detected that the transformer has positive bias magnetic, then through ΔD1, the positive half-cycle level of the midpoint voltage difference between the two arms on the primary side is continuously shortened, and the negative half-cycle remains unchanged, generating a negative volt-second product on the primary side of the transformer; through ΔD2, the negative half-cycle level of the midpoint voltage difference between the two arms on the primary side is continuously extended, and the positive half-cycle remains unchanged, generating a negative volt-second product on the primary side of the transformer, thus suppressing and then eliminating the positive bias magnetic of the transformer. Negative bias magnetic is compensated by -ΔD1 and -ΔD2, and the bias magnetic suppression effect is similar to that of positive bias magnetic. As shown in the timing diagram, for the upper and lower tubes of the first arm, the normal duty cycle is 50% for each. When compensated by ΔD1, the duty cycle of the upper tube becomes D1 = D0 - ΔD1, and the duty cycle of the lower tube becomes D2 = D0 + ΔD2. Here, D1 and D2 are converted into actual time by the processor, and then the PWM waveforms for the two paths of the upper and lower tubes are adjusted at its port, and after power amplification by the drive circuit, they are directly connected to the switching tubes. Among them, considering the existence of the dead zone, D0 is generally a little smaller than 0.5, and D0 is near 0.5.

[0088] It can be understood that for judging whether the transformer has positive or negative bias magnetic, after obtaining the average value of the signal output by the current detection unit, taking the output reference of the current detection unit as 0V as an example, this value can be positive or negative, and thus the function of detecting the bias magnetic direction of the transformer can be achieved by judging positive and negative. Further, the compensation value ΔDx also has its own positive and negative signs, and the setting of determining the bias magnetic direction through the sign can be determined according to actual needs, and this application does not make specific limitations here.

[0089] In Figure 9Based on the provided transformer DC bias feedback device, this embodiment also provides a circuit structure diagram of another transformer DC bias feedback device. For details, please refer to Figure 12 In some embodiments, the secondary side of the transformer includes a third bridge arm B3, and the third bridge arm B3 includes two complementary PWM fifth switching tubes Q21 and sixth switching tubes Q22;

[0090] The compensation unit 202 is further configured to generate a third compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and output the third compensation signal to the fifth switching tube and the sixth switching tube; wherein, the expression of the duty ratio change amount of the fifth switching tube Q21 caused by the third compensation signal is q5 = x * △D3, and the expression of the duty ratio change amount of the sixth switching tube Q22 caused by the third compensation signal is q6 = -1 * x * △D3.

[0091] In some embodiments, the secondary side of the transformer further includes a fourth bridge arm B4, and the fourth bridge arm B4 includes two complementary PWM seventh switching tubes Q23 and eighth switching tubes Q24;

[0092] The compensation unit 202 is further configured to generate a fourth compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and output the fourth compensation signal to the seventh switching tube Q23 and the eighth switching tube Q24; wherein, the expression of the duty ratio change amount of the seventh switching tube Q23 caused by the fourth compensation signal is q7 = x * △D4, and the expression of the duty ratio change amount of the eighth switching tube Q24 caused by the fourth compensation signal is q8 = -1 * x * △D4.

[0093] In some embodiments, the primary side of the transformer includes a first bridge arm and a second bridge arm, the secondary side of the transformer includes a third bridge arm and a fourth bridge arm, and the compensation unit is further configured to simultaneously generate any multiple of the first compensation signal, the second compensation signal, the third compensation signal, and the fourth compensation signal and output them to the corresponding switching tubes respectively.

[0094] Specifically, as Figure 12 shown in the embodiment, the converter is a bidirectional isolated H-bridge DC-DC converter. In addition to the first bridge arm and the second bridge arm on the primary side of the transformer, there will also be a third bridge arm and a fourth bridge arm on the secondary side of the transformer. Similarly, for the bidirectional isolated H-bridge DC-DC converter, the bias magnetic suppression can also be implemented on the secondary side bridge arm. The principle of its bias magnetic suppression function is the same as that of implementing bias magnetic suppression on the primary side bridge arm, but the compensation value needs to be multiplied by a correction coefficient according to the transformer turns ratio.

[0095] It can be understood that the primary side and the secondary side of the above transformer can be a half-bridge structure (corresponding to one arm of a bridge) or a full-bridge structure (corresponding to two arms of a bridge). That is, it can be selected that one side is a half-bridge structure and the other side is a full-bridge structure, or both can be half-bridge structures simultaneously or both can be full-bridge structures simultaneously. The above embodiments do not make specific limitations on this.

[0096] Specifically, as Figure 13 shown in the timing diagram, G xx is the drive signal of each switch tube; φ y1 is the phase shift angle between the two arms of the primary side, and φ y2 is the phase shift angle between the two arms of the secondary side. Taking the case where the magnetic flux direction generated by the exciting current flowing into the same-named terminal is positive as an example, if it is detected that the transformer has positive bias magnetization, through △D3, the positive half-cycle level of the voltage difference between the midpoints of the two arms of the secondary side is continuously shortened, and the negative half-cycle remains unchanged, generating a negative volt-second product on the primary side of the transformer; through △D4, the negative half-cycle level of the voltage difference between the midpoints of the two arms of the secondary side is continuously extended, and the positive half-cycle remains unchanged, generating a negative volt-second product on the secondary side of the transformer, thereby suppressing and then eliminating the positive bias magnetization of the transformer. The negative bias magnetization is compensated by -△D3 and -△D4, and the bias magnetization suppression effect is similar to that of the positive bias magnetization.

[0097] It can be understood that for a bidirectional isolation H-bridge type DC-DC converter, the compensation can be any one, or any two, or any three, or all four of △D1 of the first arm, △D2 of the second arm, △D3 of the third arm, and △D4 of the fourth arm for compensation, and the compensated △D3 and △D4 need to be multiplied by a correction factor according to the transformer turns ratio.

[0098] As Figure 9 shown, in some embodiments, it further includes a bias magnetization warning module 30;

[0099] The bias magnetization detection module 10 is further configured to output the DC bias magnetization value of the transformer to the bias magnetization warning module 30;

[0100] The bias magnetization warning module 30 is configured to compare the DC bias magnetization value of the transformer with a preset maximum DC bias magnetization threshold and a preset minimum DC bias magnetization threshold. When the DC bias magnetization value of the transformer is greater than the preset maximum DC bias magnetization threshold or less than the preset minimum DC bias magnetization threshold, it sends a warning signal to the processor.

[0101] Specifically, another path of the output voltage signal of the bias magnetic detection module in the transformer DC bias feedback device is connected to the bias magnetic warning module, and the output of the bias magnetic warning module is connected to the output end of the processor. It can be understood that the processor can be the processor built in the device or the processor outside the transformer, depending on the actual situation. When a bias magnetic event beyond the correction ability occurs in the circuit and the detected peak value of the magnetic flux density exceeds the preset value in the processor, a warning signal will be sent to the processor, and the processor will be responsible for judging the next action, such as immediately stopping the PWM wave generation. It can be understood that the preset value is set at the critical saturation value with a certain safety margin from the saturation magnetic density of the transformer. The preset value can be positive or negative, and the maximum value and the minimum value can be set to form a safe bias magnetic range, which is determined according to the actual requirements.

[0102] The transformer DC bias feedback device provided by the embodiment of the present application uses a small part of the transformer core in the relevant converter as an auxiliary magnetic path and leads out an auxiliary winding, so that it has the function of detecting the exciting current. The bias magnetic value of the transformer is obtained through the signal processing module, and then through the processing of the bias magnetic control module, the duty cycle adjustment amount of the switching tubes of each bridge arm is obtained, and the duty cycle of the switching tubes of each bridge arm is adjusted to generate a volt-second product opposite to the direction of the core bias magnetic to cancel the DC bias in the transformer. On the one hand, the present application can effectively suppress and finally eliminate the DC bias of the main transformer core caused by various factors; the response speed is fast, and the bias magnetic suppression and elimination are timely; the compensated duty cycle amount is small, and the influence on the working state of the main circuit is extremely small; on the other hand, the embodiment of the present application abandons the DC blocking capacitor in the main circuit, has a low hardware cost, can save the hardware volume for large current scenarios, and thus can effectively reduce the detection cost of the relevant transformer DC bias.

[0103] The second aspect of the embodiment of the present application provides a converter, including a transformer and any one of the above-mentioned transformer DC bias feedback devices. The transformer includes a core, and a groove is provided on the surface or edge of the core, and the auxiliary magnet is arranged in the groove, and the auxiliary winding is wound around the auxiliary magnetic path. The auxiliary magnet and the auxiliary winding together form the auxiliary magnetic path; wherein the groove is a carved molding structure, or the core and the corresponding groove are an integral molding structure.

[0104] This embodiment also provides a schematic structural diagram of an auxiliary magnetic path, as Figure 14As shown, in a specific embodiment, a groove 12a is provided on the surface of the magnetic core 11. A cylindrical auxiliary magnet 13a and an auxiliary winding 13b wound around the auxiliary magnet 13a are provided in the groove 12a. The auxiliary magnet 13a and the auxiliary winding 13b together form an auxiliary magnetic circuit 13. The groove 12a can be a carved structure, that is, the groove 12a structure can be carved on the surface of the magnetic core 11 by a carving machine. Since the transformer itself has a large size, the setting of the groove 12a will not have too much impact on the main body of the magnetic core 11, and the manufacturing cost is low and it is easy to implement. It can also be an integrally formed structure, that is, after determining the shape and size of the groove 12a, a corresponding mold is designed, so that the magnetic core 11 with the groove 12a can be directly obtained during the mold opening process, and the production cost is low. As Figure 15 As shown, in another specific embodiment, the groove 12b is provided on the edge of the surface of the magnetic core 11, and its principle and structure are the same as those of the foregoing specific embodiment, and will not be elaborated here.

[0105] The third aspect of the embodiments of the present application provides a converter, including a transformer and any one of the above-mentioned transformer DC bias feedback devices. The transformer includes a magnetic core, and the raised auxiliary magnet is provided on the surface of the magnetic core. The auxiliary winding is wound around the auxiliary magnet, and the auxiliary magnet and the auxiliary winding together form the auxiliary magnetic circuit; wherein, the magnetic core and the corresponding auxiliary magnet are connected by an adhesive, or the magnetic core and the corresponding auxiliary magnet are of an integrally formed structure.

[0106] In some embodiments, the auxiliary magnet and the transformer DC bias feedback device are of an integrally encapsulated structure, and the integrally encapsulated structure is connected to the magnetic core through a protrusion by an adhesive.

[0107] This embodiment also provides a structural schematic diagram of another auxiliary magnetic circuit, as Figure 16 As shown, an ear-shaped auxiliary magnet 13a is provided on the surface of the magnetic core 11, and an auxiliary winding 13b wound around the auxiliary magnet 13a. The auxiliary magnet 13a and the auxiliary winding 13b together enclose to form an auxiliary magnetic circuit 13. The method of setting the ear-shaped auxiliary magnet 13a will not damage the original shape of the magnetic core 11 (main magnetic circuit), and can play a role in ensuring the stable performance of the transformer. The magnetic core 11 and the auxiliary magnet 13a are connected by an adhesive, that is, the magnetic core 11 and the auxiliary magnet 13a can be fixed by gluing, the operation is simple and convenient, and the size of the auxiliary magnet 13a can be controlled to be smaller. In addition, the magnetic core 11 and the auxiliary magnet 13a can also be of an integrally formed structure, and the production cost is low. It can be understood that in the specific implementation process, which method is used to construct the auxiliary magnetic circuit 12 can be selected according to factors such as actual equipment conditions, economic conditions, converter size requirements, and connection requirements between related devices, and no limitation is made here.

[0108] Figure 17 Figure 17 shows a schematic flowchart of a method for transformer DC bias feedback provided by the fourth aspect of the present application. The method for transformer DC bias feedback is applied to a converter. The transformer in the converter includes a magnetic core. The transformer DC bias feedback device includes a bias detection module. The bias detection module includes an auxiliary magnetic circuit, a current detection unit, and a signal processing module. The auxiliary magnetic circuit includes an auxiliary magnet and a short-circuited auxiliary winding. The auxiliary winding is wound around the auxiliary magnet. The auxiliary magnetic circuit is disposed on the surface or edge of the magnetic core. The current detection unit is connected to the auxiliary winding. The signal processing module is connected to the current detection unit. The method includes steps 1701 and 1702.

[0109] Step 1701: The current detection unit obtains the demagnetizing current flowing through the auxiliary winding.

[0110]

[0109] Step 1702: The signal processing module obtains the transformer DC bias value based on the demagnetizing current.

[0111] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the present application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0112] In the description of the present application, reference to "one embodiment" or "some embodiments" etc. means that a specific feature, structure, or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment" and "in some embodiments" etc. that appear in different places in this specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0113] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A DC bias feedback device for a transformer, applied to a converter, characterized in that, The transformer in the converter includes a magnetic core. The transformer DC bias feedback device includes a bias detection module. The bias detection module includes an auxiliary magnetic circuit, a current detection unit, and a signal processing module. The auxiliary magnetic circuit includes an auxiliary magnet and a short-circuited auxiliary winding. The auxiliary winding is wound around the auxiliary magnet. The auxiliary magnetic circuit is disposed on the surface or edge of the magnetic core; The current detection unit is connected to the auxiliary winding and is configured to obtain the demagnetizing current flowing through the auxiliary winding; The signal processing module is connected to the current detection unit and is configured to obtain the DC bias value of the transformer based on the demagnetizing current.

2. The DC bias feedback device for a transformer according to claim 1, characterized in that, The signal processing module includes a band-pass filtering unit, a peak detection unit, and a bias value acquisition unit; The band-pass filtering unit is connected to the current detection unit and is configured to obtain a first voltage signal based on the demagnetizing current and output the first voltage signal to the peak detection unit; The peak detection unit is connected to the band-pass filtering unit and is configured to obtain a second voltage signal based on the first voltage signal and output the second voltage signal to the bias value acquisition unit; The bias value acquisition unit is connected to the peak detection unit and is configured to obtain the DC bias value of the transformer from the second voltage signal based on a preset conversion coefficient.

3. The transformer DC bias feedback device according to claim 1, wherein It further includes a bias control module. The bias control module includes a voltage processing unit and a compensation unit; The signal processing module is further configured to generate a third voltage signal representing the DC bias value of the transformer and output the third voltage signal to the voltage processing unit; The voltage processing unit is connected to the signal processing module and is configured to generate a fourth voltage signal based on a preset voltage and the third voltage signal and output the fourth voltage signal to the compensation unit; The compensation unit is connected to the voltage processing unit and is configured to generate a compensation signal based on the fourth voltage signal and output the compensation signal to the switching tube in the converter.

4. The DC bias feedback device for a transformer according to claim 3, wherein The primary side of the transformer includes a first bridge arm and / or a second bridge arm; wherein, the first bridge arm includes two first switching tubes and second switching tubes with complementary PWM, and the second bridge arm includes two third switching tubes and fourth switching tubes with complementary PWM; The compensation unit is further configured to generate a first compensation value of the driving duty ratio of the switching tube based on the fourth voltage signal, generate a first compensation signal based on the first compensation value, and output the first compensation signal to the first switching tube and the second switching tube; wherein, the expression of the change amount of the duty ratio of the first switching tube caused by the first compensation signal is q1 = △D1, and the expression of the change amount of the duty ratio of the second switching tube caused by the first compensation signal is q2 = -△D1; The compensation unit is further configured to generate a second compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a second compensation signal based on the second compensation value, and output the second compensation signal to the third switching tube and the fourth switching tube; wherein, the expression of the duty ratio change amount of the third switching tube caused by the second compensation signal is q3 = ΔD2, and the expression of the duty ratio change amount of the fourth switching tube caused by the second compensation signal is q4 = -ΔD2.

5. The transformer DC bias feedback device according to claim 4, wherein The secondary side of the transformer includes a third bridge arm and / or a fourth bridge arm; wherein, the third bridge arm includes a fifth switching tube and a sixth switching tube with complementary PWMs, and the fourth bridge arm includes a seventh switching tube and an eighth switching tube with complementary PWMs; The compensation unit is further configured to generate a third compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and output the third compensation signal to the fifth switching tube and the sixth switching tube; wherein, the expression of the duty ratio change amount of the fifth switching tube caused by the third compensation signal is q5 = x * ΔD3, and the expression of the duty ratio change amount of the sixth switching tube caused by the third compensation signal is q6 = -1 * x * ΔD3; The compensation unit is further configured to generate a fourth compensation value of the switching tube drive duty ratio based on the fourth voltage signal, generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and output the fourth compensation signal to the seventh switching tube and the eighth switching tube; wherein, the expression of the duty ratio change amount of the seventh switching tube caused by the fourth compensation signal is q7 = x * ΔD4, and the expression of the duty ratio change amount of the eighth switching tube caused by the fourth compensation signal is q8 = -1 * x * ΔD4.

6. The transformer DC bias feedback device as described in claim 5, characterized in that, The compensation unit is further configured to simultaneously generate any multiple of the first compensation signal, the second compensation signal, the third compensation signal, and the fourth compensation signal and output them to the corresponding switching tubes for compensation respectively.

7. The transformer DC bias feedback device according to claim 1, wherein It further includes a bias magnetic warning module; The bias magnetic detection module is further configured to output the transformer DC bias value to the bias magnetic warning module; The bias magnetic warning module is configured to compare the transformer DC bias value with a preset DC bias maximum threshold and a preset DC bias minimum threshold, and send a warning signal to the processor when the transformer DC bias value is greater than the preset DC bias maximum threshold or less than the preset DC bias minimum threshold.

8. A converter, characterized in that, It includes a transformer and the transformer DC bias feedback device according to any one of claims 1 to 7. The transformer includes a magnetic core, and a groove is provided on the surface or edge of the magnetic core. The auxiliary magnet is arranged in the groove, and the auxiliary winding is wound around the auxiliary magnetic path. The auxiliary magnet and the auxiliary winding together form the auxiliary magnetic path; wherein, the magnetic core and the corresponding groove are of an integrally formed structure, or the groove is of a carved structure.

9. A converter, characterized in that, Comprising a transformer and a transformer DC bias feedback device as described in any one of claims 1 to 7, the transformer includes a magnetic core, the surface of the magnetic core is provided with the raised auxiliary magnet, the auxiliary winding is wound around the auxiliary magnet, and the auxiliary magnet and the auxiliary winding together form the auxiliary magnetic circuit; wherein, the magnetic core and the corresponding auxiliary magnet are of an integrally formed structure, or the magnetic core and the corresponding auxiliary magnet are connected by an adhesive.

10. The converter according to claim 9, characterized in that, The auxiliary magnet and the transformer DC bias feedback device are of an integrally encapsulated structure, wherein the integrally encapsulated structure is connected to the magnetic core through the raised portion by an adhesive.

11. A method for transformer DC bias feedback, characterized in that, Applied to a converter, the transformer in the converter includes a magnetic core, the transformer DC bias feedback device includes a bias detection module, the bias detection module includes an auxiliary magnetic circuit, a current detection unit and a signal processing module, the auxiliary magnetic circuit includes an auxiliary magnet and a short-circuited auxiliary winding, the auxiliary winding is wound around the auxiliary magnet, the auxiliary magnetic circuit is arranged on the surface or edge of the magnetic core, the current detection unit is connected to the auxiliary winding, the signal processing module is connected to the current detection unit, and the method includes: The current detection unit obtains the demagnetizing current flowing through the auxiliary winding. The signal processing module obtains the DC bias value of the transformer based on the demagnetizing current.

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