Transformer direct current bias feedback device and method, and converter

Abstract

The present application provides a transformer direct current bias feedback device and method, and a converter. The transformer direct current bias feedback device is applied to the converter; a transformer in the converter comprises magnetic cores; the transformer direct current bias feedback device comprises a bias detection module; the bias detection module comprises an auxiliary magnetic circuit, a magnetic sensor, and a signal processing module; the auxiliary magnetic circuit is provided on the surfaces of the magnetic cores; the magnetic sensor is embedded and fixed in the auxiliary magnetic circuit, and is configured to acquire a magnetic flux density value in the auxiliary magnetic circuit, generate a first voltage signal on the basis of the magnetic flux density value, and output the first voltage signal to the signal processing module; and the signal processing module is connected to the magnetic sensor, and is configured to acquire a transformer direct current bias value on the basis of the first voltage signal. By applying the device of the present application, the hardware volume can be reduced, and the detection costs of the related transformer direct current bias can be effectively reduced while the transformer bias value can be effectively measured.

Description

A transformer DC bias feedback device, converter and method Technical Field

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

[0002] Isolated converters are widely used in power electronic systems, achieving energy conversion between input and output through the electromagnetic coupling of a transformer while providing electrical isolation. However, in isolated active bridge topologies, the transformer may generate DC current bias during operation. When this DC bias accumulates to a certain level, it will lead to core saturation, which can have a fatal impact on the entire circuit. A common method to suppress transformer DC bias is to connect a DC blocking capacitor in series in the main circuit, as shown in Figures 1 and 2. However, when the current in the main circuit is large, the DC blocking capacitor will generate considerable losses, reducing conversion efficiency. The current in the main circuit will also generate a voltage drop across the DC blocking capacitor, causing the circuit's operating state to deviate, increasing control difficulty, and this method will also significantly increase the circuit's size and cost. Technical issues

[0003] This application provides a transformer DC bias feedback device and converter, which aims to solve the problems of high difficulty and high cost in detecting transformer DC bias in related converters. Technical solutions

[0004] To address the aforementioned technical problems, the first aspect of this application provides a transformer DC bias feedback device 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 magnetic sensor, and a signal processing module, and the auxiliary magnetic circuit is disposed on the surface of the magnetic core.

[0005] The magnetic sensor is embedded and fixed in the auxiliary magnetic circuit, and is 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.

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

[0007] In one 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 acquire a second voltage signal representing the average value of the signal based on the first voltage signal, and to output the second voltage signal;

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

[0010] In one embodiment, the transformer DC bias feedback device further includes a bias control module, which includes a second signal processing unit and a compensation unit.

[0011] The signal processing module is further configured to generate a third voltage signal characterizing the DC bias 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 transistor 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 switch and a second switch of two complementary PWMs, and the second bridge arm includes a third switch and a fourth switch of two complementary PWMs.

[0015] The compensation unit is further configured to generate a first compensation value for the duty cycle of the switching transistor 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 transistor and the second switching transistor; wherein the first compensation signal causes the expression for the change in the duty cycle of the first switching transistor to be q1=△D1, and the first compensation signal causes the expression for the change in the duty cycle of the second switching transistor to be q2=-△D1.

[0016] The compensation unit is further configured to generate a second compensation value for the duty cycle of the switching transistor 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 and fourth switching transistors; wherein the second compensation signal causes the expression for the change in the duty cycle of the third switching transistor to be q3=ΔD2, and the second compensation signal causes the expression for the change in the duty cycle of the fourth switching transistor to be q4=-ΔD2.

[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 and a sixth switch with two complementary PWMs, and the fourth bridge arm includes a seventh and an eighth switch with two complementary PWMs.

[0018] The compensation unit is further configured to generate a third compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and to output the third compensation signal to the fifth and sixth switching transistors; wherein, the expression for the change in the duty cycle of the fifth switching transistor caused by the third compensation signal is q5=x*△D3, and the expression for the change in the duty cycle of the sixth switching transistor caused by the third compensation signal is q6=-1*x*△D3;

[0019] The compensation unit is further configured to generate a fourth compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and to output the fourth compensation signal to the seventh and eighth switching transistors; wherein, the expression for the change in the duty cycle of the seventh switching transistor caused by the fourth compensation signal is q7=x*△D4, and the expression for the change in the duty cycle of the eighth switching transistor 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 switching transistors for compensation.

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

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

[0023] The biased magnetic field warning module is configured to compare the DC biased magnetic field value of the transformer with a preset maximum DC biased magnetic field threshold and a preset minimum DC biased magnetic field threshold. When the DC biased magnetic field value of the transformer is greater than the preset maximum DC biased magnetic field threshold or less than the preset minimum DC biased magnetic field threshold, a warning signal is sent to the processor.

[0024] A second aspect of this application provides a converter including a transformer and a transformer DC bias feedback device as described in any of the preceding claims.

[0025] In one embodiment, the transformer includes two magnetic cores, and each of the two magnetic cores has a groove on its end face facing the gap at the junction of the two magnetic cores. The two grooves together enclose the auxiliary magnetic circuit. The magnetic core and the corresponding groove are integrally formed, or the groove is an engraved structure.

[0026] In one embodiment, the transformer includes two magnetic cores, each with a protrusion connected to its end face. The two protrusions and the end faces of the two magnetic cores together form the auxiliary magnetic circuit. The magnetic cores and the corresponding protrusions are integrally formed, or the magnetic cores and the corresponding protrusions are connected by an adhesive.

[0027] In one embodiment, the protrusion and the transformer DC bias feedback device are integrated into a single package structure, wherein the integrated package structure is connected to the magnetic core via the protrusion using an adhesive.

[0028] A third aspect of this application provides a transformer DC bias feedback method 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 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, and 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 obtains the DC bias value of the transformer based on the first voltage signal. Beneficial effects

[0031] The transformer DC bias feedback device provided in this application uses a small portion 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. On the one hand, this application embodiment samples the magnetic flux density value of the transformer core, which can more directly reflect the operating state of the transformer compared to sampling other physical quantities. On the other hand, the hardware used in this application embodiment has low cost, can save hardware size in high-current scenarios, and can effectively detect the transformer bias value while effectively reducing the detection cost of the related transformer DC bias. Attached Figure Description

[0032] To more clearly illustrate the related technologies or the technical solutions in the embodiments of this application, the drawings used in the description of the related technologies or the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application, and not all embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

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

[0037] Figure 5 is a structural schematic diagram of a refined transformer DC bias feedback device provided in the first aspect of the embodiments of this application;

[0038] Figure 6 is a schematic diagram of the structure of a transformer DC bias feedback device applied to a unidirectional isolated bridge DC-DC converter according to the first aspect of the embodiments of this application;

[0039] Figure 7 is a schematic diagram of the structure of a transformer DC bias feedback device applied to a bidirectional isolated bridge DC-DC converter according to the first aspect of the present application.

[0040] Figure 8 is a schematic diagram of another refined transformer DC bias feedback device provided in the first aspect of the embodiments of this application;

[0041] Figure 9 is a circuit diagram of a transformer DC bias feedback device applied to a unidirectional isolated bridge DC-DC converter according to the first aspect of the embodiments of this application.

[0042] Figure 10 is a timing diagram of bias suppression provided by the first aspect of the embodiments of this application;

[0043] Figure 11 is a circuit diagram of a transformer DC bias feedback device applied to a bidirectional isolated bridge DC-DC converter according to the first aspect of the present application.

[0044] Figure 12 is another timing diagram of bias suppression provided by the first aspect of the embodiments of this application;

[0045] Figure 13 is a schematic diagram of another refined transformer DC bias feedback device provided in the first aspect of the embodiments of this application;

[0046] Figure 14 is a schematic diagram of the basic structure of an auxiliary magnetic circuit in a converter provided by the second aspect of the embodiments of this application;

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

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

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

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

[0051] Figure 19 is a schematic flowchart of a transformer DC bias feedback method provided in the third aspect of the embodiments of this application. Embodiments of the present invention

[0052] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0053] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0054] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means one or more, unless otherwise explicitly specified.

[0056] Figure 3 shows a schematic diagram of a transformer DC bias feedback device according to a first aspect of this application. For ease of explanation, only the parts related to this embodiment are shown, which are described in detail below:

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

[0060] Specifically, the hardware used for current sampling of transformers, such as chip-level current sensors, integrated-level current sensors, or combinations of shunts and isolation operational amplifiers, is relatively expensive. Furthermore, magnetic flux density (MFD) directly reflects the transformer's operating state compared to other circuit quantities. Therefore, this application's embodiment selects to sample the transformer's MFD. Given that power magnetic devices in the industry, such as inductors and transformers, are generally quite large, within this size range, utilizing a small portion of their magnetic core as an auxiliary magnetic circuit to provide an additional magnetic field detection function allows for the detection of the core's magnetic state with a smaller size and lower cost.

[0061] A detailed schematic diagram of the auxiliary magnetic circuit is shown in Figure 4. In the figure, The magnetic reluctance represents the portion of the main magnetic circuit that overlaps with the auxiliary magnetic circuit. This represents the magnetic reluctance of the auxiliary magnetic circuit, most of which is generated by the air gap. and This represents the magnetic reluctance of the main magnetic circuit excluding the portion overlapping with the auxiliary magnetic circuit. Due to the presence of the air gap, Therefore, most of the magnetic flux in the core is concentrated in the main magnetic flux. Therefore, the auxiliary magnetic circuit has a very small impact on the main magnetic circuit. Furthermore, the auxiliary magnetic flux... With magnetic core flux The relationship between them can be represented as:

[0062]

[0063] Magnetic flux density of auxiliary magnetic circuit 12 magnetic flux density of magnetic core 11 The relationship between them can be represented as:

[0064]

[0065] in, The cross-sectional area and air gap length of the auxiliary magnetic circuit 12 are affected, and can be obtained through experimental testing. This is based on the magnetic flux density value measured by the magnetic sensor. ,as well as and The magnetic flux density of the transformer core can be obtained by finding the coefficient c between the two.

[0066] It is understandable that the auxiliary magnetic circuit used for detection can be constructed at the junction of the existing magnetic core by methods such as opening windows or slots. If it is not desired to destroy the original shape of the magnetic core (main magnetic circuit), edges can be added to the surface of the magnetic core to construct the auxiliary magnetic circuit. The edges can even be added to the surface of the magnetic core by adhesive. The size of the auxiliary magnetic circuit can be determined according to the size of the magnetic sensor, and this application embodiment does not limit it here.

[0067] Furthermore, a magnetic field (magnetic flux density) detection sensor is embedded in the air gap of the constructed auxiliary magnetic circuit, which can measure the instantaneous value of the magnetic flux density of the auxiliary magnetic circuit. The sensor outputs a first voltage signal characterizing the magnetic flux density value to the signal processing module. The signal processing module converts the magnetic flux density of the auxiliary magnetic circuit into the transformer bias value according to a preset conversion coefficient.

[0068] Based on the transformer DC bias feedback device provided in Figure 3, this embodiment also provides a detailed structural schematic diagram of the transformer DC bias feedback device. Please refer to Figure 5 for details. In some embodiments, the signal processing module 103 includes a first signal processing unit 1031 and a bias value acquisition unit 1032; wherein, the first signal processing unit is an averaging 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 acquire a second voltage signal representing the average value of the signal based on the first voltage signal, and to output the second voltage signal.

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

[0071] Specifically, after the magnetic sensor converts the magnetic flux density value into a first voltage signal, the first signal processing unit processes the first voltage signal to obtain its DC component, which is the second voltage signal. The second voltage signal is a voltage signal that characterizes 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 to finally obtain 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 by a low-pass filter. This application embodiment does not make any special limitation.

[0072] Figure 6 shows a schematic diagram of a transformer DC bias feedback device applied to a unidirectional isolated bridge DC-DC converter according to an embodiment of this application. Figure 7 shows a schematic diagram of a transformer DC bias feedback device applied to a bidirectional isolated bridge DC-DC converter according to an embodiment of this application. It should be understood that in some optional embodiments, the unidirectional isolated bridge DC-DC converter adopts a phase-shifted full-bridge converter, and the bidirectional isolated bridge DC-DC converter adopts a dual active bridge converter (DAB). In the embodiments, the auxiliary magnetic circuit 101 is the edge provided by the transformer DC bias feedback device itself, or an additional edge, which is assembled with the magnetic core of the transformer in the converter to form a ring. In other embodiments, the auxiliary magnetic circuit 101 is constructed at the junction of the existing magnetic core by means of opening a window or slotting. When the device is assembled onto the magnetic core, it is only necessary 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] Based on the transformer DC bias feedback device provided in Figure 5, this embodiment also provides another detailed structural schematic diagram of the transformer DC bias feedback device, as shown in Figure 8. In some embodiments, it also includes a bias control module 20, which includes a second signal processing unit 201 and a compensation unit 202.

[0074] The signal processing module 103 is also configured to generate a third voltage signal characterizing the DC bias 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 transistor in the converter.

[0077] Specifically, after detecting DC bias in the transformer, the bias control module can suppress the DC bias. First, the signal processing module outputs the third voltage signal characterizing 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 the fourth voltage signal. Then, the compensation unit generates a compensation value for the duty cycle of the switch drive based on the fourth voltage signal and sends the compensation signal to the corresponding switch in the converter. This generates a volt-second product opposite to the current core bias on the primary or secondary side of the transformer, suppressing and eliminating the core bias.

[0078] It is understandable that the preset voltage in the second signal processing unit is usually 0. In practical applications, the preset voltage can be preset to other values ​​to achieve special functions. For example, if a large positive bias is predicted to occur under certain conditions, the preset voltage value can be adjusted in advance to adjust the transformer's bias to the negative direction in advance, thereby enhancing the system's resistance to positive bias in such cases. In addition, the magnetic sensor itself also has a reference voltage, which is the reference voltage of the magnetic sensor when there is zero input. Different manufacturers and models of magnetic sensors will have different reference voltages. Generally, the reference voltage of a dual-power supply sensor is 0V, and the reference voltage of a single-power supply sensor is 0.5 times the power supply voltage. The reference voltage here can be flexibly set based on the actual application, and this embodiment does not impose specific limitations here.

[0079] Based on the transformer DC bias feedback device provided in Figure 8, 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, which contains a first switch Q11 and a second switch Q12 of two complementary PWM transistors.

[0080] The compensation unit 202 is also configured to generate a first compensation value for the duty cycle of the switching transistor 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 transistor Q11 and the second switching transistor Q12; wherein, the first compensation signal causes the expression for the change in the duty cycle of the first switching transistor Q11 to be q1=△D1, and the first compensation signal causes the expression for the change in the duty cycle of the second switching transistor Q12 to be q2=-△D1.

[0081] In some embodiments, the primary side of the transformer further includes a second bridge arm B2, which includes a third switch Q13 and a fourth switch Q14 with two complementary PWMs.

[0082] The compensation unit 202 is also configured to generate a second compensation value for the duty cycle of the switching transistor 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 transistor Q13 and the fourth switching transistor Q14; wherein, the expression for the change in the duty cycle of the third switching transistor Q13 caused by the second compensation signal is q3=ΔD2, and the expression for the change in the duty cycle of the fourth switching transistor Q14 caused by the second compensation signal is q4=-ΔD2.

[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 either the first compensation signal or the second compensation signal and output it to the corresponding switching transistor for compensation.

[0084] Specifically, this solution detects the bias state of the transformer core using a bias detection module. Then, through signal processing in the bias control module, it obtains the duty cycle adjustment amount for the switching transistors of each bridge arm. Adjusting the duty cycle of each bridge arm's switching transistors generates a volt-second product opposite to the bias direction of the core, ultimately canceling the DC bias in the transformer. Within the same bridge arm, the upper and lower transistors use complementary PWM; therefore, when the duty cycle of the upper transistor changes by ΔD, the lower transistor changes by -1*ΔD. As shown in the embodiment in Figure 9, the converter is a unidirectional isolated H-bridge DC-DC converter. For a unidirectional isolated H-bridge DC-DC converter, compensation can be either ΔD1 of the first bridge arm or ΔD2 of the second bridge arm, or both simultaneously.

[0085] The bias suppression effect can be illustrated by the timing diagram shown in Figure 10. In the timing diagram, G xx For each switching transistor, φ is the drive signal. y1This represents the phase shift angle between the two primary arms. Taking the direction of the magnetic flux generated by the excitation current flowing into the same-named terminals as positive, if a positive bias is detected in the transformer, then ΔD1 continuously shortens the positive half-cycle level of the voltage difference between the midpoints of the two primary arms while keeping the negative half-cycle unchanged, generating a negative volt-second product on the primary side of the transformer. Similarly, ΔD2 continuously extends the negative half-cycle level of the voltage difference between the midpoints of the two primary arms while keeping the positive half-cycle unchanged, generating a negative volt-second product on the primary side of the transformer, thereby suppressing and ultimately eliminating the positive bias of the transformer. Negative bias is compensated for by -ΔD1 and -ΔD2, with a similar effect to positive bias suppression. As shown in the timing diagram, the upper and lower transistors of bridge arm 1 normally have a 50% duty cycle each. When ΔD1 is compensated, the duty cycle of the upper transistor becomes D1 = D0 - ΔD1, and the duty cycle of the lower transistor becomes D2 = D0 + ΔD2. Here, D1 and D2 are converted into actual time by the DSP, and the port is adjusted to output two PWM waveforms for the upper and lower transistors. After power amplification by the driver circuit, they are directly connected to the switching transistors. Considering the existence of dead time, D0 is generally slightly smaller than 0.5, and D0 is around 0.5.

[0086] It is understandable that, to determine whether a transformer has positive or negative magnetic bias, the signal output by the magnetic sensor can be averaged (taking the magnetic sensor output reference as 0V, this value can be positive or negative). Then, the direction of the transformer's magnetic bias can be detected by judging the positive or negative sign. Furthermore, the compensation value △Dx also has a sign. The setting of the magnetic bias direction determined by the sign can be determined according to actual needs. This application does not make specific limitations here.

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

[0088] The compensation unit 202 is also configured to generate a third compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and to output the third compensation signal to the fifth and sixth switching transistors; wherein, the expression for the change in the duty cycle of the fifth switching transistor Q21 caused by the third compensation signal is q5=x*△D3, and the expression for the change in the duty cycle of the sixth switching transistor 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, which includes a seventh switch Q23 and an eighth switch Q24 with two complementary PWMs.

[0090] The compensation unit 202 is also configured to generate a fourth compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and to output the fourth compensation signal to the seventh switching transistor Q23 and the eighth switching transistor Q24; wherein, the expression for the change in the duty cycle of the seventh switching transistor Q23 caused by the fourth compensation signal is q7=x*△D4, and the expression for the change in the duty cycle of the eighth switching transistor 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 compensation signals among the first compensation signal, the second compensation signal, the third compensation signal and the fourth compensation signal, and output them to the corresponding switching transistors for compensation.

[0092] Specifically, the converter in the embodiment shown in Figure 11 is a bidirectional isolated H-bridge DC-DC converter. In addition to the first and second bridge arms on the primary side of the transformer, the bidirectional isolated H-bridge DC-DC converter also has a third and fourth bridge arm on the secondary side. Similarly, for the bidirectional isolated H-bridge DC-DC converter, bias suppression can also be implemented on the secondary bridge arm. Its bias suppression function is the same as the bias suppression principle implemented on the primary bridge arm, but the compensation value needs to be multiplied by a correction coefficient according to the transformer turns ratio.

[0093] Detailed timing diagram as shown in Figure 12, G xx For each switching transistor, φ is the drive signal. y1 φ is the phase shift angle between the two bridge arms on the primary side. y2 This represents the phase shift angle between the two arms of the secondary winding. Taking the direction of the magnetic flux generated by the excitation current flowing into the same-named terminals as positive, if a positive bias is detected in the transformer, ΔD3 continuously shortens the positive half-cycle level of the voltage difference between the midpoints of the two arms of the secondary winding while keeping the negative half-cycle unchanged, generating a negative volt-second product on the primary winding of the transformer. ΔD4 continuously extends the negative half-cycle level of the voltage difference between the midpoints of the two arms of the secondary winding while keeping the positive half-cycle unchanged, generating a negative volt-second product on the secondary winding of the transformer, thereby suppressing and ultimately eliminating the positive bias of the transformer. Negative bias is compensated for by -ΔD3 and -ΔD4, with a similar effect to positive bias suppression.

[0094] It is understandable that for a bidirectional isolated H-bridge DC-DC converter, compensation can be provided for any one, two, three, or all four of the following: 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. Furthermore, the compensation for ΔD3 and ΔD4 needs to be multiplied by a correction factor based on the transformer turns ratio.

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

[0096] Based on the transformer DC bias feedback device provided in Figure 8, this embodiment also provides a more detailed structural schematic diagram of the transformer DC bias feedback device, as shown in Figure 13. In some embodiments, it also includes a bias warning module 30.

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

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

[0099] Specifically, another path of the output voltage signal from the bias detection module in the transformer DC bias feedback device is connected to the bias early warning module. The output of the bias early warning module is connected to the processor output. This processor can be either an integrated processor within the device or an external processor, depending on the specific requirements. When a bias event exceeding the correction capability occurs in the circuit, and the detected peak magnetic flux density exceeds a preset value in the processor, an early warning signal is sent to the processor, which then determines the next action, such as immediately stopping PWM wave generation. This preset value is set at a critical saturation value with a certain safety margin from the transformer's saturation magnetic flux density. The preset value can be positive or negative, and a maximum and minimum value can be set to form a safe bias range, determined according to actual needs.

[0100] The transformer DC bias feedback device provided in this application utilizes a small portion of the transformer core in the correlated 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 processing by the bias control module, the duty cycle adjustment amount for the switching transistors of each bridge arm is obtained. Adjusting the duty cycle of each bridge arm's switching transistors generates a volt-second product opposite to the bias direction of the core, thereby canceling 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 early warning module. This value is provided to the processor as a basis for determining whether the transformer core is saturated, so as to take further measures to prevent faults. On the one hand, the embodiments of this application sample the magnetic flux density of the transformer core, which can more directly reflect the operating state of the transformer compared to sampling other physical quantities. It can effectively suppress and ultimately eliminate DC bias of the main transformer core caused by various factors; the response speed is fast and the bias suppression and elimination are timely; the compensation duty cycle is small and the impact on the main circuit operating state is minimal. On the other hand, the embodiments of this application eliminate the DC blocking capacitor in the main circuit, which uses low-cost hardware and can save hardware volume in high-current scenarios, thus effectively reducing the detection cost of DC bias of the transformer.

[0101] A second aspect of this application provides a converter, including a transformer and any one of the above-described transformer DC bias feedback devices.

[0102] In some embodiments, the transformer includes two magnetic cores, and the end faces of the two magnetic cores facing the gap at the junction of the two magnetic cores are respectively provided with grooves, and the two grooves together enclose an auxiliary magnetic circuit; wherein, the magnetic cores and the corresponding grooves are integrally formed structures, or the grooves are engraved structures.

[0103] Specifically, Figure 14 is a basic structural diagram of an auxiliary magnetic circuit provided in this embodiment, which will not be described in detail here. In addition, this embodiment also provides a preferred structural diagram of the auxiliary magnetic circuit, as shown in Figures 15 and 16. The end faces of the two magnetic cores 11 facing the gap are respectively provided with grooves 11a, and the two grooves 11a together form the auxiliary magnetic circuit 12. This facilitates the reduction of device size. The magnetic sensor 2 is fixed at any position on the auxiliary magnetic circuit 12, thereby detecting the magnetic flux density value of the auxiliary magnetic circuit 12. As shown in Figure 15, in the first specific embodiment, the groove 11a is a carved structure, that is, the groove 11a structure can be carved on the surface of the magnetic core 11 by a carving machine. Since the transformer itself is large, the setting of the groove 11a will not have a significant impact on the main body of the magnetic core 11, resulting in low manufacturing cost and ease of implementation. As shown in Figure 16, in the second specific embodiment, the magnetic core 11 and the corresponding groove 11a are integrally formed. In other words, after determining the shape and size of the groove 11a, a corresponding mold is designed, so that a magnetic core 11 with the groove 11a can be directly obtained during the mold-making process, resulting in low production costs. It is understood that the dashed lines in the figure indicate that only the structural diagram above the dashed lines is shown, and no specific restrictions are placed on the shape of the device.

[0104] In some embodiments, the transformer includes two magnetic cores, each with a protrusion connected to its end face. The two protrusions and the end faces of the two magnetic cores together form an auxiliary magnetic circuit. The magnetic cores and the corresponding protrusions are integrally formed, or the magnetic cores and the corresponding protrusions are connected by an adhesive.

[0105] Furthermore, in some embodiments, the protrusion and the transformer DC bias feedback device are integrated into a single package structure, wherein the integrated package structure is connected to the magnetic core by an adhesive through the protrusion.

[0106] This embodiment also provides another preferred structural diagram of the auxiliary magnetic circuit, as shown in Figures 17 and 18. Two 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 together form the auxiliary magnetic circuit 12. That is, the protrusions 12b and the outer surface of the magnetic cores 11 form an air gap. The magnetic sensor 2 is fixed in this air gap, thereby detecting the magnetic flux density value of the auxiliary magnetic circuit 12. Setting the protrusions 12b does not damage the original shape of the magnetic cores 11 (main magnetic circuit) and can ensure the stable performance of the transformer. As shown in Figure 17, in the third specific embodiment, two protrusions 12b (two additional magnetic core 11 structures) are spaced apart. The two protrusions 12b and the outer surfaces of the two magnetic cores 11 together form the auxiliary magnetic circuit 12. The magnetic cores 11 and the protrusions 12b are connected by adhesive. That is, the magnetic cores 11 and the protrusions 12b can be fixed by adhesive, which is simple and convenient to operate, and the size of the protrusions 12b can be controlled to be smaller. As shown in Figure 18, in the fourth specific implementation, two protrusions 12b are also spaced apart (the protrusions 12b can be additional magnetic core 11 structures). The two protrusions 12b and the outer surface of the magnetic core 11 together form an auxiliary magnetic circuit 12. The magnetic core 11 and the protrusions 12b are integrally formed, resulting in low production costs. It can be understood that in the specific implementation process, the method used to construct the auxiliary magnetic circuit 12 can be selected based on factors such as actual equipment conditions, economic conditions, size requirements in the converter, and connection requirements between related devices, and no restrictions are imposed here.

[0107] Figure 19 shows a schematic flowchart of a transformer DC bias feedback method provided in the third aspect of the present application. The transformer DC bias feedback method 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 disposed on the surface of the magnetic core. The magnetic sensor is embedded and fixed within 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 obtains the DC bias value of the transformer based on the first voltage signal.

[0110] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0111] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, phrases such as "in one embodiment," "in some embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0112] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions 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 this application, and should all be included within the protection scope of this application.

Claims

1. A transformer DC bias feedback device, applied to a converter, characterized in that, 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, and is 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 obtain the DC bias value of the transformer based on the first voltage signal.

2. The transformer DC bias feedback device as described in 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 averaging unit or a low-pass filtering unit; The first signal processing unit is connected to the magnetic sensor and is configured to acquire a second voltage signal representing the average value of the signal based on the first voltage signal, and to output the second voltage signal; The bias magnetization value acquisition unit is connected to the first signal processing unit and is configured to acquire the DC bias magnetization value of the transformer based on the second voltage signal.

3. The transformer DC bias feedback device as described in claim 1, characterized in that, It also includes a bias control module, which includes a second signal processing unit and a compensation unit; The signal processing module is further configured to generate a third voltage signal characterizing 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 transistor in the converter.

4. The transformer DC bias feedback device as described in claim 3, characterized in that, 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 switch and a second switch of two complementary PWMs, and the second bridge arm includes a third switch and a fourth switch of two complementary PWMs. The compensation unit is further configured to generate a first compensation value for the duty cycle of the switching transistor 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 transistor and the second switching transistor; wherein the first compensation signal causes the expression for the change in the duty cycle of the first switching transistor to be q1=△D1, and the first compensation signal causes the expression for the change in the duty cycle of the second switching transistor to be q2=-△D1. The compensation unit is further configured to generate a second compensation value for the duty cycle of the switching transistor 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 and fourth switching transistors; wherein the second compensation signal causes the expression for the change in the duty cycle of the third switching transistor to be q3=ΔD2, and the second compensation signal causes the expression for the change in the duty cycle of the fourth switching transistor to be q4=-ΔD2.

5. The transformer DC bias feedback device as described in 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 and a sixth switch with two complementary PWMs, and the fourth bridge arm includes a seventh and an eighth switch with two complementary PWMs. The compensation unit is further configured to generate a third compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a third compensation signal based on the third compensation value and a correction coefficient preset according to the transformer turns ratio, and to output the third compensation signal to the fifth and sixth switching transistors; wherein, the expression for the change in the duty cycle of the fifth switching transistor caused by the third compensation signal is q5=x*△D3, and the expression for the change in the duty cycle of the sixth switching transistor caused by the third compensation signal is q6=-1*x*△D3; The compensation unit is further configured to generate a fourth compensation value for the duty cycle of the switching transistor based on the fourth voltage signal, and to generate a fourth compensation signal based on the fourth compensation value and a correction coefficient x preset according to the transformer turns ratio, and to output the fourth compensation signal to the seventh and eighth switching transistors; wherein, the expression for the change in the duty cycle of the seventh switching transistor caused by the fourth compensation signal is q7=x*△D4, and the expression for the change in the duty cycle of the eighth switching transistor 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 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 transistors for compensation.

7. The transformer DC bias feedback device as described in claim 1, characterized in that, It also includes a magnetic bias warning module; The bias detection module is also configured to output the DC bias value of the transformer to the bias early warning module; The biased magnetic field warning module is configured to compare the DC biased magnetic field value of the transformer with a preset maximum DC biased magnetic field threshold and a preset minimum DC biased magnetic field threshold. When the DC biased magnetic field value of the transformer is greater than the preset maximum DC biased magnetic field threshold or less than the preset minimum DC biased magnetic field threshold, a warning signal is sent to the processor.

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

9. The converter as claimed in claim 8, characterized in that, The transformer includes two magnetic cores, and each of the two magnetic cores has a groove on its end face facing the gap at the junction of the two magnetic cores. The two grooves together enclose the auxiliary magnetic circuit. The magnetic core and the corresponding groove are integrally formed, or the groove is an engraved structure.

10. The converter as claimed in claim 8, characterized in that, The transformer includes two magnetic cores, and protrusions are connected to the end faces of the two magnetic cores respectively. The two protrusions and the end faces of the two magnetic cores together form the auxiliary magnetic circuit. The magnetic cores and the corresponding protrusions are integrally formed, or the magnetic cores and the corresponding protrusions are connected by adhesive.

11. The converter as claimed in claim 10, characterized in that, The protrusion and the transformer DC bias feedback device are integrated into a single package structure, wherein the integrated package structure is connected to the magnetic core through the protrusion using an adhesive.

12. A method for DC bias feedback of a transformer, characterized in that, The device is applied to a converter, wherein the transformer in the converter includes a magnetic core, 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, and 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 obtains the DC bias value of the transformer based on the first voltage signal.

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