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 magnetic sensor and a signal processing module. The auxiliary magnetic circuit is arranged on the surface of the magnetic core; the magnetic sensor is embedded and fixed in the auxiliary magnetic circuit and is configured to obtain a magnetic density value in the auxiliary magnetic circuit, generate a first voltage signal based on the magnetic density value and output the first voltage signal to the signal processing module; the signal processing module is connected with the magnetic sensor and is configured to obtain a transformer direct current magnetic bias value based on the first voltage signal. 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 provide electrical isolation functions at the same time. However, in an isolated active bridge topology, a DC current bias may occur in the transformer during operation. When these DC biases accumulate to a certain extent, magnetic core saturation will occur, which will have a fatal impact on the entire circuit. Common methods for suppressing DC bias in 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 operating state of the circuit to shift, increasing the control difficulty. Moreover, this method will 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 DC bias in transformers in related converters.

[0004] To solve the above technical problems, in a first aspect of the embodiments of this application, a transformer DC bias feedback device is provided, which 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 magnetic sensor, and a signal processing module. The auxiliary magnetic circuit is arranged on the surface of the magnetic core;

[0005] The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit, configured to obtain the magnetic flux density value in the auxiliary magnetic circuit, generate a first voltage signal based on the magnetic flux density value, and output the first voltage signal to the signal processing module;

[0006] The signal processing module is connected to the magnetic sensor and is configured to obtain the transformer DC bias value based on the first voltage signal.

[0007] In an embodiment, the signal processing module includes a first signal processing unit and a bias value acquisition unit; wherein, the first signal processing unit is an averaging unit or a low-pass filtering unit;

[0008] The first signal processing unit is connected to the magnetic sensor and is configured to obtain a second voltage signal representing the signal average value based on the first voltage signal, and output the second voltage signal;

[0009] The bias magnetic value acquisition unit is connected to the first signal processing unit and is configured to obtain the DC bias magnetic value of the transformer based on the second voltage signal.

[0010] 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 second signal processing unit and a compensation unit;

[0011] The signal processing module is further configured to generate a third voltage signal representing the DC bias magnetic value of the transformer, and output the third voltage signal to the second signal processing unit;

[0012] The second signal 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;

[0013] The compensation unit is connected to the second signal 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.

[0014] 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;

[0015] 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;

[0016] 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.

[0017] 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;

[0018] The compensation unit is further configured to generate a third compensation value of the driving duty ratio of the switch 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 amount of the duty ratio of the fifth switch caused by the third compensation signal is q5 = x * △D3, and the expression of the change amount of the duty ratio of the sixth switch caused by the third compensation signal is q6 = -1 * x * △D3;

[0019] The compensation unit is further configured to generate a fourth compensation value of the driving duty ratio of the switch 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 amount of the duty ratio of the seventh switch caused by the fourth compensation signal is q7 = x * △D4, and the expression of the change amount of the duty ratio of the eighth switch caused by the fourth compensation signal is q8 = -1 * x * △D4.

[0020] In one embodiment, 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 switches for compensation respectively.

[0021] In one embodiment, the transformer DC bias feedback device further includes a bias warning module;

[0022] The bias detection module is further configured to output the transformer DC bias value to the bias warning module;

[0023] 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.

[0024] A 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.

[0025] In one embodiment, the transformer includes two magnetic cores. Grooves are respectively provided on the end faces of the two magnetic cores facing the side of the gap at the junction of the two magnetic cores. The two grooves jointly enclose to form the auxiliary magnetic circuit. Wherein, the magnetic core and the corresponding groove are of an integrally formed structure, or the groove is of a carved structure.

[0026] In one embodiment, the transformer includes two magnetic cores. Protrusions are respectively connected to the end faces of the two magnetic cores. The two protrusions and the end faces of the two magnetic cores jointly enclose to form the auxiliary magnetic circuit. Wherein, the magnetic core and the corresponding protrusion are of an integrally formed structure, or the magnetic core and the corresponding protrusion are connected by an adhesive.

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

[0028] The third aspect of the present application provides a method for DC bias feedback of a transformer, which is applied to a converter. The transformer in the converter includes a magnetic core. The DC bias feedback device of the transformer includes a bias magnetic detection module. The bias magnetic detection module includes an auxiliary magnetic circuit, a magnetic sensor, and a signal processing module. The auxiliary magnetic circuit is arranged on the surface of the magnetic core. The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit. The signal processing module is connected to the magnetic sensor;

[0029] The magnetic sensor acquires the magnetic flux density value in the auxiliary magnetic circuit, generates a first voltage signal based on the magnetic flux density value, and outputs the first voltage signal to the signal processing module;

[0030] The signal processing module acquires the DC bias value of the transformer based on the first voltage signal.

[0031] The DC bias feedback device of the transformer provided by the embodiment of the present application uses a small part of the magnetic core of the transformer in the relevant converter as the auxiliary magnetic circuit. By detecting the magnetic flux density of the auxiliary magnetic circuit and performing coefficient conversion, the magnetic state of the transformer magnetic core can be obtained. On the one hand, the magnetic flux density value of the magnetic core of the transformer is sampled in the embodiment of the present application, which can more directly reflect the operating state of the transformer compared with sampling other physical quantities. On the other hand, the hardware cost adopted in the embodiment of the present application is low, and the hardware volume can be saved for large current scenarios. While effectively detecting the bias magnetic value of the transformer, the detection cost of the relevant DC bias of the transformer can be effectively reduced. Description of the Drawings

[0032] To more clearly illustrate the related technologies or the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the related technologies 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 Schematic diagram of the circuit 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 Schematic diagram of the circuit 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 Schematic diagram of the structure of a transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0036] Figure 4 Schematic diagram of the auxiliary magnetic circuit provided in the first aspect of the embodiments of the present application;

[0037] Figure 5 Schematic diagram of the structure of a refined transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0038] Figure 6 Schematic diagram of the structure 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;

[0039] Figure 7 Schematic diagram of the structure 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;

[0040] Figure 8 Schematic diagram of the structure of another refined transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0041] Figure 9 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;

[0042] Figure 10 Magnetic bias suppression timing diagram provided in the first aspect of the embodiments of the present application;

[0043] Figure 11The 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 bidirectional isolated bridge-type DC-DC converter;

[0044] Figure 12 Another magnetic bias suppression timing diagram provided in the first aspect of the embodiments of the present application;

[0045] Figure 13 The structural schematic diagram of a refined transformer DC bias feedback device provided in the first aspect of the embodiments of the present application;

[0046] Figure 14 The basic structural schematic diagram of an auxiliary magnetic circuit in a converter provided in the second aspect of the embodiments of the present application;

[0047] Figure 15 The partial structural schematic diagram of a preferred auxiliary magnetic circuit in a converter provided in the second aspect of the embodiments of the present application;

[0048] Figure 16 Another partial structural schematic diagram of a preferred auxiliary magnetic circuit in a converter provided in the second aspect of the embodiments of the present application;

[0049] Figure 17 Another partial structural schematic diagram of a preferred auxiliary magnetic circuit in a converter provided in the second aspect of the embodiments of the present application;

[0050] Figure 18 Another partial structural schematic diagram of a preferred auxiliary magnetic circuit in a converter provided in the second aspect of the embodiments of the present application;

[0051] Figure 19 The flow schematic diagram of a transformer DC bias feedback method provided in the third aspect of the embodiments of the present application. Detailed implementation manners

[0052] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear and understandable, 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.

[0053] It should be noted that when an element is referred to as "fixed on" 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 "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0054] It should be understood that the orientation or positional relationship indicated by terms such as "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 drawings. It 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.

[0055] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" is one or more than one, unless otherwise specifically defined.

[0056] Figure 3 The structural schematic diagram of a transformer DC bias feedback device provided by the first aspect of the embodiment of the present application is shown. For the convenience of description, only the parts related to this embodiment are shown and are described in detail as follows:

[0057] In this embodiment, the transformer DC bias feedback device is applied to a converter. The transformer in the converter includes a magnetic core. The transformer DC bias feedback device includes a bias magnetic detection module 10. The bias magnetic detection module includes an auxiliary magnetic circuit 101, a magnetic sensor 102, and a signal processing module 103. The auxiliary magnetic circuit 101 is arranged on the surface of the magnetic core;

[0058] The magnetic sensor 102 is embedded and fixed in the auxiliary magnetic circuit 101, and is configured to acquire the magnetic flux density value in the auxiliary magnetic circuit 101, generate a first voltage signal based on the magnetic flux density value, and output the first voltage signal to the signal processing module 103;

[0059] The signal processing module 103 is connected to the magnetic sensor 102 and is configured to acquire the transformer DC bias value based on the first voltage signal.

[0060] Specifically, the hardware costs of using a chip-level current sensor, an integrated-level current sensor, or a combination of a shunt and an isolation operational amplifier for current sampling of the transformer are relatively high, and the magnetic flux density value can more directly reflect the operating state of the transformer compared with other circuit quantities. Therefore, the embodiment of the present application selects to sample the magnetic flux density value of the transformer. Considering that the sizes of power magnetic devices such as inductors and transformers in the industry are relatively large, within this volume level, using a small part of its magnetic core as an auxiliary magnetic circuit to enable it to have an attached magnetic field detection function can detect the magnetic state of the magnetic core at a relatively small volume and cost.

[0061] Specifically, the schematic diagram of the auxiliary magnetic circuit is asFigure 4 As shown in the figure. In the figure, R m1 represents the magnetic reluctance of the magnetic path in the main magnetic path that overlaps with the auxiliary magnetic path, and R m2 represents the magnetic reluctance of the auxiliary magnetic path, most of which is generated by the air gap. R m31 and R m32 represent the magnetic reluctance of the main magnetic path except for the part that overlaps with the auxiliary magnetic path. Due to the existence of the air gap, R m2 >> R m1 , so most of the core magnetic flux mainly converges in the main magnetic flux Φ1. Therefore, the influence of the auxiliary magnetic path on the main magnetic path is very small. Further, the relationship between the auxiliary magnetic flux Φ2 and the core magnetic flux Φ can be expressed as:

[0062]

[0063] The relationship between the magnetic flux density value B2 of the auxiliary magnetic path 12 and the magnetic flux density value B of the core 11 can be expressed as:

[0064]

[0065] Among them, c is affected by the cross-sectional area of the auxiliary magnetic path 12 and the air gap length, and can be obtained by experimental testing. According to the magnetic flux density value B2 measured by the magnetic sensor and the coefficient c between B2 and B, the magnetic flux density value of the transformer core can be obtained.

[0066] It can be understood that the structure of the auxiliary magnetic path for detection can be constructed at the junction of the existing core by methods such as windowing or grooving; if it is not desired to damage the original shape of the core (main magnetic path), edges can also be added on the surface of the core to construct the auxiliary magnetic path, and even the edges can be installed on the surface of the core by gluing; the size of the auxiliary magnetic path can be determined according to the size of the magnetic sensor, and the embodiments of the present application do not limit this here.

[0067] Further, in the air gap of the constructed auxiliary magnetic path, a magnetic field (magnetic flux density) detection sensor is embedded, and the instantaneous value of the magnetic flux density of the auxiliary magnetic path can be measured. The sensor outputs a first voltage signal representing the magnetic flux density value to the signal processing module, and the signal processing module converts the magnetic flux density of the auxiliary magnetic path into the transformer bias magnetic value according to a preset conversion coefficient.

[0068] Based on the Figure 3 provided transformer DC bias magnetic feedback device, this embodiment also provides a structural schematic diagram of a refined transformer DC bias magnetic feedback device. Specifically, please refer to Figure 5 . In some embodiments, the signal processing module 103 includes a first signal processing unit 1031 and a bias magnetic value acquisition unit 1032; among them, the first signal processing unit is an average value calculation unit or a low-pass filtering unit;

[0069] The first signal processing unit 1031 is connected to the magnetic sensor 102, and is configured to obtain a second voltage signal representing the signal average value based on the first voltage signal, and output the second voltage signal;

[0070] The bias magnetic value acquisition unit 1032 is connected to the first signal processing unit 1031, and is configured to obtain the DC bias magnetic value of the transformer based on the second voltage signal.

[0071] Specifically, after the magnetic sensor converts the magnetic flux density value into the first voltage signal, the first signal processing unit processes the first voltage signal to obtain its DC component, that is, the second voltage signal. The second voltage signal is a voltage signal representing the average magnetic flux density of the auxiliary magnetic circuit. Then, the bias magnetic value acquisition unit processes the second voltage signal according to the preset magnetic flux density conversion coefficient between the main magnetic circuit and the auxiliary magnetic circuit, and finally obtains the DC bias magnetic value of the transformer. It can be understood that the first signal processing unit can be implemented by an averaging circuit or a low-pass filter, and the embodiments of the present application do not make special limitations.

[0072] As Figure 6 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 isolated bridge type DC-DC converter. As Figure 7 shown is a schematic structural diagram of a transformer DC bias feedback device provided by 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 uses a phase-shifted full-bridge converter, and the bidirectional isolated bridge type DC-DC converter uses a dual active bridge converter (DAB). In the embodiment, the auxiliary magnetic circuit 101 is an edge provided by the transformer DC bias feedback device provided by this embodiment, or an additional edge is assembled with the magnetic core of the converter in the transformer and then enclosed together. In other embodiments, the auxiliary magnetic circuit 101 is constructed by methods such as windowing or grooving at the junction of the existing magnetic cores. When this device is assembled onto the magnetic core, it only needs to ensure that the magnetic sensor is located in the auxiliary magnetic circuit for correct detection. This embodiment does not make specific limitations here.

[0073] On the basis of the transformer DC bias feedback device provided in Figure 5 , this embodiment also provides a schematic structural diagram of another refined transformer DC bias feedback device. For details, please refer to Figure 8 . In some embodiments, it further includes a bias magnetic control module 20, and the bias magnetic control module includes a second signal processing unit 201 and a compensation unit 202;

[0074] The signal processing module 103 is further configured to generate a third voltage signal representing the DC bias magnetic value of the transformer, and output the third voltage signal to the second signal processing unit 201;

[0075] The second signal 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 a third voltage signal, and output the fourth voltage signal to the compensation unit;

[0076] The compensation unit 202 is connected to the second signal 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.

[0077] Specifically, after detecting the DC bias of the transformer, the DC bias can also be suppressed by the bias control module. First, the signal processing module outputs the third voltage signal representing the DC bias of the transformer to the second signal processing unit. The second signal 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 of the driving duty ratio 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, and suppress and then eliminate the bias of the transformer core.

[0078] It can be understood that the preset voltage in the second signal processing unit is usually 0. In practical applications, the preset voltage can also be preset to other values for realizing special functions. For example, if it is predicted that a large positive bias will occur in some cases, the value of the preset voltage can be adjusted in advance, so that the bias of the transformer is adjusted negatively in advance to enhance the resistance of the system to the positive bias in this case. In addition, the magnetic sensor itself also has a reference voltage, that is, the reference voltage of the magnetic sensor at zero input, which varies for different manufacturers and models. Generally, the reference voltage of a dual-power sensor is 0V, and the reference voltage of a single-power sensor is 0.5 times the power supply voltage value. The reference voltage here can be flexibly set based on actual applications, and no specific limitation is made in this embodiment.

[0079] In Figure 8 Based on the provided transformer DC bias feedback device, this embodiment also provides a circuit structure diagram of the transformer DC bias feedback device. For details, please refer to Figure 9 , 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;

[0080] The compensation unit 202 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 Q11 and the second switching tube Q12; wherein, the expression of the duty ratio change amount of the first switching tube Q11 caused by the first compensation signal is q1 = △D1, and the expression of the duty ratio change amount of the second switching tube Q12 caused by the first compensation signal is q2 = -△D1.

[0081] 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 fourth switching tubes Q14;

[0082] The compensation unit 202 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 Q13 and the fourth switching tube Q14; wherein, the expression of the duty ratio change amount of the third switching tube Q13 caused by the second compensation signal is q3 = △D2, and the expression of the duty ratio change amount of the fourth switching tube Q14 caused by the second compensation signal is q4 = -△D2.

[0083] 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 any one of the first compensation signal and the second compensation signal and output it to the corresponding switching tube for compensation.

[0084] Specifically, in this solution, the bias magnetic state of the transformer core is detected by the bias magnetic detection module, and then through the signal processing in the bias magnetic control module, the duty ratio adjustment amount of the switching tubes of each bridge arm is obtained, the duty ratio of the switching tubes of each bridge arm is adjusted, and a volt-second product opposite to the direction of the core bias magnetic is generated, finally to cancel the DC bias in the transformer. In the same bridge arm, the upper and lower tubes are complementary PWM, so when the duty ratio of the upper tube changes by △D, the lower tube changes by -1*△D. As Figure 9 The converter in the shown embodiment is a unidirectional isolated H-bridge type DC-DC converter. For a unidirectional isolated H-bridge type DC-DC converter, the compensation can be △D1 of the first bridge arm, △D2 of the second bridge arm, either one of the two or both compensated simultaneously.

[0085] Among them, the bias magnetic suppression effect can be illustrated by the timing diagram as Figure 10 shown. In the timing diagram, G xx is the drive signal of each switching tube; φ y1It is the phase-shift angle between the two bridge 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 positive bias magnetization of the transformer is detected, then through △D1, the positive half-cycle level of the midpoint voltage difference between the two bridge arms on the primary side is continuously shortened, while the negative half-cycle remains unchanged, generating a negative volt-second product on the primary side of the transformer; through △D2, the negative half-cycle level of the midpoint voltage difference between the two bridge arms on the primary side is continuously extended, while the positive half-cycle remains unchanged, generating a negative volt-second product on the primary side of the transformer, thereby suppressing and then eliminating the positive bias magnetization of the transformer. The negative bias magnetization is compensated through -△D1 and -△D2, and the bias magnetization suppression effect is similar to that of positive bias magnetization. As shown in the timing diagram, for the upper and lower switches of the first bridge arm, the normal duty cycle of each is 50%. When △D1 is compensated, the duty cycle of the upper switch becomes D1 = D0 - △D1, and the duty cycle of the lower switch becomes D2 = D0 + △D2. After D1 and D2 here are converted into actual time by the DSP, the PWM waveforms for the two paths of the upper and lower switches are adjusted and sent out from its ports, and after being power-amplified 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.

[0086] It can be understood that for judging the existence of positive or negative bias magnetization of the transformer, after the signal output by the magnetic sensor is averaged (taking the output reference of the magnetic sensor as 0V, this value can be positive or negative), and then the function of detecting the bias magnetization direction of the transformer can be achieved by judging positive and negative. Further, the compensation value △Dx also has its own positive and negative signs, and the setting of determining the bias magnetization direction through the sign can be determined according to actual needs, and the present application does not make specific limitations here.

[0087] In Figure 8 Based on the provided transformer DC bias magnetization feedback device, this embodiment also provides a circuit structure diagram of another transformer DC bias magnetization feedback device. For details, please refer to Figure 11 , in some embodiments, the secondary side of the transformer includes a third bridge arm B3, and the third bridge arm B3 includes a fifth switching tube Q21 and a sixth switching tube Q22 that are complementary to each other in PWM;

[0088] The compensation unit 202 is further configured to generate a third compensation value of the switching tube drive duty cycle 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; among them, the expression of the change amount of the duty cycle of the fifth switching tube Q21 caused by the third compensation signal is q5 = x * △D3, and the expression of the change amount of the duty cycle of the sixth switching tube Q22 caused by the third compensation signal is q6 = -1 * x * △D3.

[0089] In some embodiments, the secondary side of the transformer further includes a fourth bridge arm B4, and the fourth bridge arm B4 includes a seventh switch Q23 and an eighth switch Q24 with complementary PWMs;

[0090] The compensation unit 202 is further configured to generate a fourth compensation value of the duty cycle of the switch 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 Q23 and the eighth switch Q24; wherein, the expression of the change amount of the duty cycle of the seventh switch Q23 caused by the fourth compensation signal is q7 = x * △D4, and the expression of the change amount of the duty cycle of the eighth switch Q24 caused by the fourth compensation signal is q8 = -1 * x * △D4.

[0091] 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 switches for compensation respectively.

[0092] Specifically, as Figure 11 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, and its bias magnetic suppression function is the same as that of the primary side bridge arm, but the compensation value needs to be multiplied by a correction coefficient according to the transformer turns ratio.

[0093] Specifically, as Figure 12 shown in the timing diagram, G xx is the drive signal of each switch; φ y1 is the phase shift angle between the two bridge arms on the primary side, and φ y2 is the phase shift angle between the two bridge arms on 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 magnetic, by △D3, the positive half-cycle level of the voltage difference between the midpoints of the two bridge arms on 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; by △D4, the negative half-cycle level of the voltage difference between the midpoints of the two bridge arms on 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 eliminating the positive bias magnetic of the transformer. The negative bias magnetic is compensated by -△D3 and -△D4, and the bias magnetic suppression effect is similar to that of the positive bias magnetic.

[0094] It can be understood that for a bidirectional isolation H-bridge DC-DC converter, the compensation can be any one of ΔD1 of the first bridge arm, ΔD2 of the second bridge arm, ΔD3 of the third bridge arm, and ΔD4 of the fourth bridge arm, or any two, or any three, or all four are compensated simultaneously. And the compensated ΔD3 and ΔD4 need to be multiplied by a correction factor according to the transformer turns ratio.

[0095] It can be understood that the primary and secondary sides of the above transformer can be a half-bridge structure (corresponding to one bridge arm) or a full-bridge structure (corresponding to two bridge arms). 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 or both can be full-bridge structures at the same time. The above embodiments do not make specific restrictions on this.

[0096] In Figure 8 Based on the provided transformer DC bias feedback device, this embodiment also provides a structural schematic diagram of another refined transformer DC bias feedback device. For details, please refer to Figure 13 , in some embodiments, it further includes a bias warning module 30;

[0097] The bias detection module 10 is further configured to output the transformer DC bias value to the bias warning module 30;

[0098] The bias warning module 30 is configured to compare the transformer DC bias value with the preset DC bias maximum threshold and the preset DC bias minimum threshold. When the transformer DC bias value is greater than the preset DC bias maximum threshold or less than the preset DC bias minimum threshold, it sends a warning signal to the processor.

[0099] Specifically, another path of the output voltage signal of the bias detection module in the transformer DC bias feedback device is connected to the bias warning module, and the output of the bias warning module is connected to the output end of the processor. It can be understood that the processor can be a processor built into the device or a processor outside the transformer, depending on the actual situation. When a bias event beyond the correction ability occurs in the circuit and the detected peak 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 this 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 range, which is determined according to actual needs.

[0100] 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 circuit. By detecting the magnetic flux density of the auxiliary magnetic circuit and performing coefficient conversion, the magnetic state of the transformer core can be obtained. After being processed by the bias control module, the duty cycle adjustment amount for the switching tubes of each bridge arm is obtained, and the duty cycles of the switching tubes of each bridge arm are adjusted to generate a volt-second product opposite to the direction of core bias magnetic to cancel the DC bias in the transformer. The output signal of the bias detection module detects the peak value of the core magnetic flux density through the bias warning module, and this value is provided to the processor as a basis for judging whether the transformer core is saturated, so as to take further measures to prevent failures. On the one hand, the embodiment of the present application samples the magnetic flux density value of the transformer core, which can more directly reflect the operating state of the transformer compared with sampling other physical quantities, and can effectively suppress and finally eliminate the DC bias of the main transformer core caused by various factors; it has a fast response speed, and the bias suppression and elimination are timely; the compensated duty cycle amount is small, and the impact 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, and can save the hardware volume for large-current scenarios, so it can effectively reduce the detection cost of the relevant transformer DC bias.

[0101] 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.

[0102] In some embodiments, the transformer includes two cores. Grooves are respectively provided on the end faces of the two cores facing the side of the gap at the junction of the two cores, and the two grooves jointly enclose an auxiliary magnetic circuit; wherein, the core and the corresponding groove are of an integrally formed structure, or the groove is of a carved structure.

[0103] Specifically, as Figure 14 is a schematic diagram of the basic structure of an auxiliary magnetic circuit provided by this embodiment, which will not be introduced in detail here. In addition, this embodiment also provides a schematic diagram of a preferred structure of the auxiliary magnetic circuit, as Figure 15 and 16 shown, grooves 11a are respectively provided on the end faces of the two cores 11 facing the side of the gap, and the two grooves 11a jointly enclose an auxiliary magnetic circuit 12; to facilitate reducing the device volume, the magnetic sensor 2 is fixed at any position on the auxiliary magnetic circuit 12, so that the magnetic flux density value of the auxiliary magnetic circuit 12 can be detected. As Figure 15 shown, in the first specific implementation manner, the groove 11a is of a carved structure, that is, the groove 11a structure can be carved on the surface of the core 11 by a carving machine. Since the transformer itself has a large size, the setting of the groove 11a will not have too much impact on the main body of the core 11, and the manufacturing cost is low and it is easy to implement. As Figure 16As shown, in the second specific embodiment, the magnetic core 11 and the corresponding groove 11a are of an integrally formed structure. That is, after determining the shape and size of the groove 11a, a corresponding mold is designed, so that the magnetic core 11 with the groove 11a can be directly obtained during the mold opening process, and the production cost is low. It can be understood that the dashed line in the figure indicates that only the structure diagram above the dashed line is shown in the figure, and no specific limitation is made on the shape of the device.

[0104] In some embodiments, the transformer includes two magnetic cores. Protrusions are respectively connected to the end faces of the two magnetic cores. The two protrusions and the end faces of the two magnetic cores jointly enclose an auxiliary magnetic path; wherein, the magnetic core and the corresponding protrusion are of an integrally formed structure, or the magnetic core and the corresponding protrusion are connected by an adhesive.

[0105] Furthermore, in some embodiments, the protrusion 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 protrusion by an adhesive.

[0106] This embodiment also provides another preferred structural schematic diagram of the auxiliary magnetic path, as Figure 17 and 18 shown, protrusions 12b are respectively connected to the end faces of the two magnetic cores 11. The two protrusions 12b and the end faces of the two magnetic cores 11 jointly enclose an auxiliary magnetic path 12. That is, an air gap is formed by the enclosure of the protrusion 12b and the outer surface of the magnetic core 11, and the magnetic sensor 2 is fixed in this air gap, so that the magnetic flux density value of the auxiliary magnetic path 12 can be detected. The way of setting the protrusion 12b will not damage the original shape of the magnetic core 11 (main magnetic path), and can play a role in ensuring the stable performance of the transformer. As Figure 17 shown, in the third specific embodiment, two protrusions 12b (two additional magnetic core 11 structures) are arranged at intervals. The two protrusions 12b and the outer surfaces of the two magnetic cores 11 jointly enclose an auxiliary magnetic path 12; the magnetic core 11 and the protrusion 12b are connected by an adhesive. That is, the magnetic core 11 and the protrusion 12b can be fixed by gluing, which is simple and convenient to operate, and the size of the protrusion 12b can be controlled to be smaller. As Figure 18 shown, in the fourth specific implementation manner, two protrusions 12b (the protrusion 12b can be an additional magnetic core 11 structure) are also arranged at intervals. The two protrusions 12b and the outer surface of the magnetic core 11 jointly enclose an auxiliary magnetic path 12; the magnetic core 11 and the protrusion 12b are of an integrally formed structure, and the production cost is low. It can be understood that in the specific implementation process, which way to construct the auxiliary magnetic path 12 can be selected according to factors such as actual equipment conditions, economic conditions, size requirements in the converter, and connection requirements between related devices, and no limitation is made here.

[0107] Figure 19The figure shows a schematic flowchart of a method for transformer DC bias feedback provided in the third aspect of the embodiments 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 magnetic detection module. The bias magnetic detection module includes an auxiliary magnetic circuit, a magnetic sensor, and a signal processing module. The auxiliary magnetic circuit is disposed on the surface of the magnetic core. The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit. The signal processing module is connected to the magnetic sensor. The method includes steps 1901 and 1902;

[0108] Step 1901: The magnetic sensor acquires the magnetic flux density value in the auxiliary magnetic circuit, generates a first voltage signal based on the magnetic flux density value, and outputs the first voltage signal to the signal processing module;

[0109] Step 1902: The signal processing module acquires the transformer DC bias value based on the first voltage signal.

[0110] 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 embodiments can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into 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.

[0111] The reference to "one embodiment" or "some embodiments" etc. described in the specification of the present application means that specific features, structures, or characteristics described in conjunction with the embodiment are included in one or more embodiments of the present application. Thus, the statements "in one embodiment" and "in some embodiments" etc. that appear in different places in this specification do not necessarily refer 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.

[0112] The embodiments described above 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 described in the foregoing embodiments, or perform equivalent replacements for 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, and the bias detection module includes an auxiliary magnetic circuit, a magnetic sensor, and a signal processing module. The auxiliary magnetic circuit is disposed on the surface of the magnetic core; The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit, configured to acquire the magnetic flux density value in the auxiliary magnetic circuit, generate a first voltage signal based on the magnetic flux density value, and output the first voltage signal to the signal processing module; The signal processing module is connected to the magnetic sensor and is configured to acquire the DC bias value of the transformer based on the first voltage signal.

2. The transformer DC bias feedback device according to claim 1, characterized in that, The signal processing module includes a first signal processing unit and a bias value acquisition unit; wherein, the first signal processing unit is an average value calculation unit or a low-pass filter unit; The first signal processing unit is connected to the magnetic sensor and is configured to acquire a second voltage signal representing the signal average value based on the first voltage signal and output the second voltage signal; The bias value acquisition unit is connected to the first signal processing unit and is configured to acquire the DC bias value of the transformer based on the second voltage signal.

3. The transformer DC bias feedback device according to claim 1, characterized in that It further includes a bias control module, and the bias control module includes a second signal 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 second signal processing unit; The second signal 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 second signal 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 transformer DC bias feedback device as described in 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 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; 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 driving duty ratio of the switching tube 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 change amount of the duty ratio of the third switching tube caused by the second compensation signal is q3 = △D2, and the expression of the change amount of the duty ratio of the fourth switching tube caused by the second compensation signal is q4 = -△D2.

5. The transformer DC bias feedback device according to claim 4, characterized in that, 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; The compensation unit is further configured to generate a third compensation value of the duty cycle of the switch based on the fourth voltage signal, generate a third compensation signal based on the third compensation value and a correction factor preset according to the turns ratio of the transformer, and output the third compensation signal to the fifth switch and the sixth switch; wherein, the expression of the change in the duty cycle of the fifth switch caused by the third compensation signal is q5 = x*△D3, and the expression of the change in the duty cycle of the sixth switch caused by the third compensation signal is q6 = -1*x*△D3; The compensation unit is further configured to generate a fourth compensation value of the duty cycle of the switch based on the fourth voltage signal, generate a fourth compensation signal based on the fourth compensation value and a correction factor x preset according to the turns ratio of the transformer, and output the fourth compensation signal to the seventh switch and the eighth switch; wherein, the expression of the change in the duty cycle of the seventh switch caused by the fourth compensation signal is q7 = x*△D4, and the expression of the change in the duty cycle of the eighth switch caused by the fourth compensation signal is q8 = -1*x*△D4.

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 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.

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

8. A converter, characterized in that, It includes a transformer and the transformer DC bias magnetic feedback device according to any one of claims 1 to 8.

9. The converter according to claim 8, wherein, The transformer includes two magnetic cores, and grooves are respectively provided on the end faces of the two magnetic cores facing the gap at the junction of the two magnetic cores, and the two grooves jointly enclose the auxiliary magnetic circuit; wherein, the magnetic core and the corresponding groove are of an integrally formed structure, or the groove is of a carved structure.

10. The converter according to claim 8, characterized in that, The transformer includes two magnetic cores, and protrusions are respectively connected to the end faces of the two magnetic cores, and the two protrusions and the end faces of the two magnetic cores jointly enclose the auxiliary magnetic circuit; wherein, the magnetic core and the corresponding protrusion are of an integrally formed structure, or the magnetic core and the corresponding protrusion are connected by an adhesive.

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

12. A method for transformer DC bias feedback, characterized in that, Applied to a converter, the transformer in the converter includes a magnetic core, and the DC bias feedback device of the transformer includes a bias detection module. The bias detection module includes an auxiliary magnetic circuit, a magnetic sensor, and a signal processing module. The auxiliary magnetic circuit is disposed on the surface of the magnetic core. The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit. The signal processing module is connected to the magnetic sensor; The magnetic sensor acquires the magnetic flux density value in the auxiliary magnetic circuit, generates a first voltage signal based on the magnetic flux density value, and outputs the first voltage signal to the signal processing module; The signal processing module acquires the DC bias value of the transformer based on the first voltage signal.

Images