DCDC conversion circuit, magnetic bias control method, and power conversion device

Abstract

The invention discloses a DCDC conversion circuit, a magnetic bias control method and power conversion equipment, and belongs to the technical field of power. The DCDC conversion circuit comprises a transformer and a main power loop electrically connected with the transformer; the current detection circuit is connected between the transformer and the main power loop and is configured to detect the positive half-cycle current and the negative half-cycle current and generate a full-wave direct-current component based on the positive half-cycle current and the negative half-cycle current; and the control circuit is electrically connected with the current detection circuit and is configured to adjust the conduction time of a power tube in the main power loop according to the full-wave direct-current component, so that the full-wave direct-current component tends to zero.

Description

Technical Field

[0001] The present application belongs to the field of electric power technology, and in particular relates to a DCDC conversion circuit, a bias magnetic control method and an electric power conversion device. Background Art

[0002] Bidirectional isolated DCDC converters are prone to magnetic bias during operation. Usually, a DC blocking capacitor can be added, but this method will change the circuit structure. At the same time, when the current is large, a larger capacitance is required. Alternatively, the line impedance is used to balance the bias voltage, but the line impedance is generally small. When the magnetic bias is severe, transformer saturation cannot be avoided.

[0003] Some DCDC converters do not want to add DC blocking capacitors, but factors such as sampling deviation, control delay, and device parameter differences can cause transformer bias. In severe cases, the transformer will be saturated, causing power device failure. Therefore, how to suppress the bias phenomenon when the DCDC converter does not consider the DC blocking capacitor is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a DCDC conversion circuit, a bias control method and a power conversion device, which determine the bias state according to the positive half-cycle current and the negative half-cycle current of the transformer, and adjust the main power circuit accordingly, so as to effectively suppress the bias phenomenon without adding a DC blocking capacitor.

[0005] In a first aspect, the present application provides a DCDC conversion circuit, comprising:

[0006] A transformer and a main power circuit electrically connected to the transformer;

[0007] A current detection circuit is connected between the transformer and the main power circuit and is configured to detect the positive half-cycle current and the negative half-cycle current and generate a full-wave DC component based on the positive half-cycle current and the negative half-cycle current;

[0008] The control circuit is electrically connected to the current detection circuit and is configured to adjust the conduction time of the power tube in the main power loop according to the full-wave DC component so that the full-wave DC component tends to zero.

[0009] According to one embodiment of the present application, the current detection circuit includes:

[0010] A sampling circuit includes a current sampling transformer coupled between the transformer and the main power loop and configured to detect a positive half-cycle current and a negative half-cycle current through the current sampling transformer;

[0011] The differential circuit is electrically connected to the sampling circuit and is configured to perform differential processing on the positive half-cycle current and the negative half-cycle current and output a full-wave DC component.

[0012] According to one embodiment of the present application, the sampling circuit includes:

[0013] A first current sampling transformer comprises a primary winding and a secondary winding, wherein the primary winding is coupled between the transformer and the main power circuit;

[0014] A first unidirectional loop, wherein an input side of the first unidirectional loop is electrically connected to a first end of the secondary winding;

[0015] A second unidirectional loop, wherein an input side of the second unidirectional loop is electrically connected to a second end of the secondary winding;

[0016] A freewheeling circuit is electrically connected to the output side of the first unidirectional circuit, the output side of the second unidirectional circuit and a middle tap of the secondary winding respectively;

[0017] Wherein, both the first unidirectional loop and the second unidirectional loop are provided with a sampling output node, and the sampling output node is electrically connected to the differential circuit.

[0018] According to one embodiment of the present application, the differential circuit includes:

[0019] A first operational amplifier, wherein a non-inverting input terminal of the first operational amplifier is electrically connected to a sampling output node of the first unidirectional loop, and an inverting input terminal of the first operational amplifier is electrically connected to a sampling output node of the second unidirectional loop;

[0020] A first feedback unit, electrically connected between the inverting input terminal and the output terminal of the first operational amplifier;

[0021] The first bias circuit is electrically connected to the non-inverting input terminal of the first operational amplifier.

[0022] According to one embodiment of the present application, the sampling circuit includes:

[0023] A second current sampling transformer comprises a primary winding and a secondary winding, wherein the primary winding is coupled between the transformer and the main power loop;

[0024] a third unidirectional loop, wherein an input side of the third unidirectional loop is electrically connected to a first end of the secondary winding, and an input side of the third unidirectional loop is electrically connected to a second end of the secondary winding;

[0025] a fourth unidirectional loop, wherein an input side of the fourth unidirectional loop is electrically connected to the second end of the secondary winding, and an input side of the fourth unidirectional loop is electrically connected to the first end of the secondary winding;

[0026] The third unidirectional loop and the fourth unidirectional loop are both provided with sampling output nodes, and the sampling output nodes are electrically connected to the differential circuit.

[0027] According to one embodiment of the present application, the differential circuit includes:

[0028] A first differential operational amplifier circuit, wherein an input terminal of the first differential operational amplifier circuit is electrically connected to a sampling output node of the third unidirectional loop;

[0029] a second differential operational amplifier circuit, wherein an input terminal of the second differential operational amplifier circuit is electrically connected to a sampling output node of the fourth unidirectional loop;

[0030] A second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is electrically connected to an output terminal of the first differential operational amplifier circuit, and an inverting input terminal of the second operational amplifier is electrically connected to an output terminal of the second differential operational amplifier circuit;

[0031] A second feedback unit is electrically connected between the inverting input terminal and the output terminal of the second operational amplifier;

[0032] The second bias circuit is electrically connected to the non-inverting input terminal of the second operational amplifier.

[0033] According to one embodiment of the present application, the control circuit includes a controller, the controller is configured with a main feedback loop and a bias magnetic feedback loop, and the bias magnetic feedback loop is electrically connected to the current detection circuit;

[0034] Among them, the crossover frequency of the bias magnetic feedback loop is less than the crossover frequency of the main feedback loop.

[0035] According to one embodiment of the present application, the DCDC conversion circuit further includes:

[0036] A resonance unit, wherein a first end of the resonance unit is electrically connected to a first side of the transformer;

[0037] A conversion circuit, wherein a first side of the conversion circuit is electrically connected to a second end of the resonance unit;

[0038] The second side of the transformer is electrically connected to the main power circuit, and both the main power circuit and the conversion circuit are H-bridge switching circuits.

[0039] In a second aspect, the present application provides a bias magnetic control method for a DCDC conversion circuit, comprising:

[0040] Obtain the positive half-cycle current and negative half-cycle current of the primary side of the transformer in the DCDC conversion circuit;

[0041] Determine the DC component of the full cycle based on the positive half-cycle current and the negative half-cycle current;

[0042] The switch duty ratio of the primary side conversion circuit connected to the primary side of the transformer is adjusted according to the DC component.

[0043] According to one embodiment of the present application, adjusting the switch duty cycle of the primary side conversion circuit connected to the primary side of the transformer according to the DC component includes:

[0044] When the DC component is positive, the switch duty cycle of the power tube corresponding to the positive half cycle in the primary conversion circuit is reduced;

[0045] When the DC component is negative, the switching duty cycle of the power tube corresponding to the negative half cycle in the primary conversion circuit is reduced.

[0046] In a third aspect, the present application provides a power conversion device, including the aforementioned DCDC conversion circuit.

[0047] According to the DCDC conversion circuit, bias control method and power conversion equipment of the present application, the positive half-cycle current and negative half-cycle current between the transformer and the main power circuit are detected, and the generated full-wave DC component is used to characterize the bias condition of the transformer, and this is used as a control reference to adjust the main power circuit, thereby effectively suppressing the bias phenomenon without adding a DC blocking capacitor.

[0048] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0050] Figure 1 This is one of the structural schematic diagrams of the DCDC conversion circuit provided in the embodiment of the present application;

[0051] Figure 2 This is the second structural schematic diagram of the DCDC conversion circuit provided in the embodiment of the present application;

[0052] Figure 3 is a control block diagram of a bias magnetic feedback loop provided in an embodiment of the present application;

[0053] Figure 4 This is the third structural diagram of the DCDC conversion circuit provided in the embodiment of the present application;

[0054] Figure 5 This is the fourth structural diagram of the DCDC conversion circuit provided in the embodiment of the present application;

[0055] Figure 6 This is one of the flow charts of the bias magnetic control method of the DCDC conversion circuit provided in the embodiment of the present application;

[0056] Figure 7 This is the second flow chart of the bias magnetic control method of the DCDC conversion circuit provided in the embodiment of the present application.

[0057] Reference numerals:

[0058] Transformer T1, primary circuit 100, secondary circuit 200, current detection circuit 300, sampling circuit 310, first differential operational amplifier circuit 311, second differential operational amplifier circuit 312, differential circuit 320, control circuit 400, first to eighth power tubes Q1-Q8, first to third capacitors C1-C3, first inductor L1, current sampling transformer CT, first to fourth diodes D1-D4, first to fourth resistors R1-R4, first to fourth operational amplifiers A1-A4. DETAILED DESCRIPTION

[0059] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0060] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0061] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0062] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0063] Reference Figure 1 , Figure 1 A DCDC conversion circuit is shown. As an example, the power part of the DCDC conversion circuit may include a transformer T1, a primary circuit 100, a secondary circuit 200, and resonant devices such as inductors and capacitors.

[0064] The primary circuit 100 and the secondary circuit 200 are both based on an H-bridge circuit. The primary circuit 100 includes a first power tube Q1, a second power tube Q2, a third power tube Q3, and a fourth power tube Q4. One side of the primary circuit 100 is connected to the first capacitor C1, and the other side is electrically connected to the primary winding of the transformer T1. The first capacitor C1 is used to stabilize the power input to the primary circuit 100.

[0065] The secondary circuit 200 includes a fifth power tube Q5, a sixth power tube Q6, a seventh power tube Q7 and an eighth power tube Q8. One side of the secondary circuit 200 is electrically connected to the secondary winding of the transformer T1, and the other side is connected to the third capacitor C3. The first capacitor C3 is used to stabilize the power output by the secondary circuit 200.

[0066] The first end of the secondary winding of the transformer T1 is electrically connected to the secondary circuit 200 through the first inductor L1, and the second end of the secondary winding of the transformer T1 is electrically connected to the secondary circuit 200 through the second capacitor C2. The first inductor L1 and the second capacitor C2 serve as resonant devices to improve the conversion efficiency of the secondary side of the transformer T1 and reduce the resulting losses.

[0067] The following Figure 1 Taking the circuit structure shown as an example, the DCDC conversion circuit, bias magnetic control method and power conversion device of the present application are explained.

[0068] Reference Figure 2 , Figure 2 A DCDC conversion circuit is shown, and an embodiment of the present application proposes a DCDC conversion circuit. In this embodiment, the DCDC conversion circuit includes a transformer T1, a main power circuit, a current detection circuit 300 and a control circuit 400, the main power circuit is electrically connected to the transformer T1, the current detection circuit 300 is connected between the transformer T1 and the main power circuit, and is configured to detect the positive half-cycle current and the negative half-cycle current, and generate a full-wave DC component based on the positive half-cycle current and the negative half-cycle current, and the control circuit 400 is electrically connected to the current detection circuit 300, and is configured to adjust the conduction time of the power tube in the main power circuit according to the full-wave DC component, so that the full-wave DC component tends to zero.

[0069] As an example, the main power circuit in this embodiment can be the aforementioned primary circuit 100, and the current detection circuit 300 can be connected between the connection node of the second power tube Q2 and the fourth power tube Q4 and the first end of the primary winding of the transformer T1, or connected between the connection node of the first power tube Q1 and the third power tube Q3 and the second end of the primary winding of the transformer T1. Thus, the current detection circuit 300 can detect the current flowing through the primary winding of the transformer T1.

[0070] The secondary winding of the transformer T1 is electrically connected to the first end of the resonance unit, and the second end of the resonance unit is electrically connected to the conversion circuit. The resonance unit includes a first inductor L1 and a first capacitor C1, the first end of the secondary winding of the transformer T1 is electrically connected to the first end of the first inductor L1, and the second end of the secondary winding of the transformer T1 is electrically connected to the first end of the first capacitor C1. The conversion circuit and the main power circuit are both H-bridge switching circuits, see the above for details.

[0071] It should be noted that the full-wave DC component is the difference between the positive half-cycle current and the negative half-cycle current, and thus the full-wave DC component can be used to describe the current bias of the primary winding of the transformer T1. For example, when the positive half-cycle current is greater than the negative half-cycle current, it indicates that the primary winding of the transformer T1 has a positive current bias; when the positive half-cycle current is less than the negative half-cycle current, it indicates that the primary winding of the transformer T1 has a negative current bias.

[0072] The control circuit 400 generates a corresponding correction value based on the full-wave DC component, and adjusts the duty cycle of the switch control signal (such as the first to fourth power tubes Q1~Q4 in the example) transmitted to the main power circuit according to the correction value to control the opening time of the corresponding power tube.

[0073] As an example, when there is a positive current bias in the primary winding of the transformer T1, the control circuit 400 controls the power tubes of the positive half cycle in the main power loop to shorten the on-time, such as reducing the on-time of the first power tube Q1 and the fourth power tube Q4. When there is a negative current bias in the primary winding of the transformer T1, the control circuit 400 controls the power tubes of the negative half cycle in the main power loop to shorten the on-time, such as reducing the on-time of the second power tube Q2 and the third power tube Q3.

[0074] In some embodiments, the control circuit 400 includes a controller (not shown in the figure), which is configured with a main feedback loop and a bias magnetic feedback loop, and the bias magnetic feedback loop is electrically connected to the current detection circuit; wherein the crossover frequency of the bias magnetic feedback loop is less than the crossover frequency of the main feedback loop.

[0075] It is understandable that the main control strategy of the DCDC conversion circuit is usually to control the power tube in the main power circuit to turn on or off according to the output instruction to output the corresponding voltage and current. The main control strategy and the control strategy involved in this embodiment are usually based on feedback to form a loop control. The main feedback loop implements the aforementioned main control strategy, and the bias magnetic feedback loop implements the control strategy involved in this embodiment.

[0076] Reference Figure 3 , Figure 3 The control process of the bias magnetic feedback loop is shown in FIG. The actual values ​​of the positive half-cycle current and the negative half-cycle current after sampling are multiplied by the sampling coefficient respectively, and then multiplied by the differential amplification coefficient after differential amplification to obtain the full-wave DC component, which is then filtered by the filter and input to the controller as the feedback bias and reference quantity after calculation. The controller outputs the corresponding control quantity according to the calculated reference bias, and the sum of the control quantity and the control quantity of other loop feedback is input to the main power transfer function to control the main power loop. Among them, the reference quantity is usually zero, but it can also be other values, which are set according to specific needs.

[0077] The crossover frequency of the feedback loop is also called the bandwidth, and the size of the bandwidth can reflect the speed of the control loop response. The larger the crossover frequency, the faster the response speed of the feedback loop. In this embodiment, the crossover frequency of the bias feedback loop is less than the crossover frequency of the main feedback loop, that is, the response of the bias feedback loop in the entire system is slower than the response of the main feedback loop, thereby preventing the main power loop or other loops from being affected.

[0078] According to the DCDC conversion circuit of the present application, by detecting the positive half-cycle current and the negative half-cycle current between the transformer T1 and the main power circuit, the generated full-wave DC component is used to characterize the bias magnetization condition of the transformer, and this is used as a control reference to adjust the main power circuit, thereby effectively suppressing the bias magnetization phenomenon without adding a DC blocking capacitor.

[0079] In some embodiments, the current detection circuit 300 includes a sampling circuit 310 and a differential circuit 320. The sampling circuit 310 includes a current sampling transformer CT coupled between the transformer T1 and the main power circuit, and is configured to detect the positive half-cycle current and the negative half-cycle current through the current sampling transformer CT; the differential circuit 320 is electrically connected to the sampling circuit 310, and is configured to perform differential processing on the positive half-cycle current and the negative half-cycle current, and output a full-wave DC component.

[0080] A current sampling transformer (CT) is a transformer used for current measurement, monitoring and sampling. It is used in high voltage or high current systems and can provide accurate current signals. In this embodiment, a current sampling transformer CT is set on the primary side of the transformer T1 to perform current sampling to ensure sampling accuracy.

[0081] Reference Figure 4 As shown, Figure 4 A DCDC conversion circuit is shown. As an example, the secondary winding of the current sampling transformer CT is connected in a tapping manner, and the tap position may be located in the middle of the secondary winding.

[0082] The sampling circuit 310 includes a current sampling transformer CT, a first unidirectional loop, a second unidirectional loop and a freewheeling loop. The current sampling transformer includes a primary winding and a secondary winding. The primary winding is coupled between the transformer T1 and the main power loop. The input side of the first unidirectional loop is electrically connected to the first end of the secondary winding of the current sampling transformer CT. The input side of the second unidirectional loop is electrically connected to the second end of the secondary winding of the current sampling transformer CT. The freewheeling loop is electrically connected to the output side of the first unidirectional loop, the output side of the second unidirectional loop and the middle tap of the secondary winding of the current sampling transformer CT, respectively. The first unidirectional loop and the second unidirectional loop are both provided with a sampling output node, and the sampling output node is electrically connected to the differential circuit.

[0083] In this example, a diode is used to form a unidirectional loop, the first unidirectional loop includes a first diode D1 and a first resistor R1, and the second unidirectional loop includes a second diode D2 and a second resistor R2. The anode of the first diode D1 is electrically connected to the first end of the secondary winding of the current sampling transformer CT, the cathode of the first diode D1 is electrically connected to the first end of the first resistor R1, the anode of the second diode D1 is electrically connected to the second end of the secondary winding of the current sampling transformer CT, and the cathode of the second diode D2 is electrically connected to the first end of the second resistor R2.

[0084] The second end of the first resistor R1 is electrically connected to the second end of the second resistor R2, and the connection node is electrically connected to the tap of the current sampling transformer CT to form a freewheeling loop. The connection node between the cathode of the first diode D1 and the first end of the first resistor R1 serves as a sampling output node for sampling the positive half-cycle current; the connection node between the cathode of the second diode D2 and the first end of the second resistor R2 serves as another sampling output node for sampling the negative half-cycle current. Due to the rectification effect of the diode, the sampled positive and negative half-cycle currents are both positive values, which is convenient for subsequent differentiation.

[0085] As an example, the differential circuit 310 includes a first operational amplifier A1, a first feedback unit and a first bias circuit, the non-inverting input terminal of the first operational amplifier A1 is electrically connected to the sampling output node of the first unidirectional loop, and the inverting input terminal of the first operational amplifier A1 is electrically connected to the sampling output node of the second unidirectional loop; the first feedback unit is electrically connected between the inverting input terminal and the output terminal of the first operational amplifier A1; and the first bias circuit is electrically connected to the non-inverting input terminal of the first operational amplifier A1.

[0086] In this example, the sampled positive and negative half-cycle currents are directly input to the first operational amplifier A1 for operation. The first feedback unit forms output feedback, and the first bias circuit applies a bias to the in-phase input terminal of the first operational amplifier A1, so that the first operational amplifier A1 can achieve a differential amplification function. Among them, the first feedback unit and the first bias circuit both include capacitors and resistors in parallel, and their specific device parameters can be set according to requirements to set the corresponding differential amplification factor.

[0087] The output terminal of the first operational amplifier A1 may also be provided with an RC filtering unit, the RC filtering unit including a resistor and a capacitor. Thus, by filtering the output of the first operational amplifier A1, the active full-wave DC component is made more accurate.

[0088] Reference Figure 5 As shown, Figure 5 A DCDC conversion circuit is shown. As another example, the secondary winding of the current sampling transformer CT has no tap, and the secondary winding is connected to two sampling lines.

[0089] In some embodiments, the sampling circuit 310 includes a current sampling transformer CT, a third unidirectional loop and a fourth unidirectional loop, the current sampling transformer CT includes a primary winding and a secondary winding, the primary winding is coupled between the transformer T1 and the main power loop; the input side of the third unidirectional loop is electrically connected to the first end of the secondary winding of the current sampling transformer CT, and the input side of the third unidirectional loop is electrically connected to the second end of the secondary winding of the current sampling transformer CT; the input side of the fourth unidirectional loop is electrically connected to the second end of the secondary winding of the current sampling transformer CT, and the input side of the fourth unidirectional loop is electrically connected to the first end of the secondary winding of the current sampling transformer CT; wherein the third unidirectional loop and the fourth unidirectional loop are both provided with a sampling output node, and the sampling output node is electrically connected to the differential circuit.

[0090] In this example, a diode is used to form a unidirectional loop, the third unidirectional loop includes a third diode D3 and a third resistor R3, and the fourth unidirectional loop includes a fourth diode D4 and a fourth resistor R4. The anode of the third diode D3 is electrically connected to the first end of the secondary winding of the current sampling transformer CT, the cathode of the third diode D3 is electrically connected to the first end of the third resistor R3, and the second end of the third resistor R3 is electrically connected to the second end of the secondary winding of the current sampling transformer CT. The anode of the fourth diode D4 is electrically connected to the second end of the secondary winding of the current sampling transformer CT, the cathode of the fourth diode D4 is electrically connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is electrically connected to the first end of the secondary winding of the current sampling transformer CT. The two ends of the third resistor R3 serve as sampling output nodes for sampling the positive half-cycle current; the two ends of the fourth resistor R4 serve as sampling output nodes for sampling the negative half-cycle current.

[0091] As an example, the differential circuit 310 includes a first differential operational amplifier circuit 311, a second differential operational amplifier circuit 312, a second operational amplifier A2, a second feedback unit and a second bias circuit: the input end of the first differential operational amplifier circuit 312 is electrically connected to the sampling output node of the third unidirectional loop; the input end of the second differential operational amplifier circuit 312 is electrically connected to the sampling output node of the fourth unidirectional loop; the non-inverting input end of the second operational amplifier A2 is electrically connected to the output end of the first differential operational amplifier circuit 311, and the inverting input end of the second operational amplifier is electrically connected to the output end of the second differential operational amplifier circuit 312; the second feedback unit is electrically connected between the inverting input end and the output end of the second operational amplifier A2; and the second bias circuit is electrically connected to the non-inverting input end of the second operational amplifier A2.

[0092] The first differential operational amplifier circuit 311 may include a third operational amplifier A3 for amplifying the positive half-cycle current, and the second differential operational amplifier circuit 312 may include a fourth operational amplifier A4 for amplifying the negative half-cycle current, and the first differential operational amplifier circuit 311 and the second differential operational amplifier circuit 312 have the same amplification factor.

[0093] The second feedback unit forms output feedback, and the second bias circuit applies bias to the in-phase input terminal of the second operational amplifier A2, so that the second operational amplifier A2 can achieve differential amplification function. The second feedback unit and the second bias circuit both include capacitors and resistors connected in parallel, and their specific device parameters can be set according to requirements to set the corresponding differential amplification factor.

[0094] In this example, the positive and negative half-cycle currents obtained by sampling are amplified by the same multiple using a differential circuit and forward bias is added. The two differential outputs are then differentiated to obtain a complete full-wave current, which is then filtered to obtain the full-wave current component. Due to the presence of negative voltage, a forward bias is added to the input of the second op amp A2. The output of the second op amp A2 is filtered and the same bias voltage is subtracted to obtain the final DC component of the current.

[0095] Reference Figure 6 , Figure 6 A bias control process is shown, and an embodiment of the present application also proposes a bias control method for a DCDC conversion circuit, which can be applied to the aforementioned DCDC conversion circuit. In this embodiment, the bias control method includes step S10, step S20 and step S30.

[0096] Step S10, obtaining the positive half-cycle current and the negative half-cycle current of the primary side of the transformer in the DCDC conversion circuit;

[0097] Step S20, determining the DC component of the full cycle according to the positive half-cycle current and the negative half-cycle current;

[0098] Step S30: adjusting the switch duty ratio of the primary conversion circuit connected to the primary side of the transformer according to the DC component.

[0099] It should be noted that the specific structure of the DCDC conversion circuit can refer to the aforementioned embodiments. The DCDC conversion circuit is provided with a sampling circuit, through which the positive half-cycle current and the negative half-cycle current can be obtained.

[0100] The full-wave DC component is the difference between the positive half-cycle current and the negative half-cycle current, so the full-wave DC component can be used to describe the current bias of the primary winding of the transformer. For example, when the positive half-cycle current is greater than the negative half-cycle current, it means that the primary winding of the transformer has a positive current bias; when the positive half-cycle current is less than the negative half-cycle current, it means that the primary winding of the transformer has a negative current bias.

[0101] The control circuit 400 generates a corresponding correction value based on the full-wave DC component, and adjusts the duty cycle of the switch control signal (such as the first to fourth power tubes Q1~Q4 in the example) transmitted to the main power circuit according to the correction value to control the opening time of the corresponding power tube.

[0102] As an example, Figure 1 , 2In the DCDC conversion circuits in 4 and 5, when there is a positive current bias in the primary winding of the transformer, the control circuit 400 controls the power tubes in the positive half cycle in the main power loop to shorten the on-time, such as reducing the duty cycle of the control signals of the first power tube Q1 and the fourth power tube Q4. When there is a negative current bias in the primary winding of the transformer, the control circuit 400 controls the power tubes in the negative half cycle in the main power loop to shorten the on-time, such as reducing the duty cycle of the control signals of the second power tube Q2 and the third power tube Q3.

[0103] Reference Figure 7 , Figure 7 A bias control process is shown. After the DCDC conversion circuit starts working, the CT current is sampled; the sampling results are analyzed to determine whether the current has a DC component; if not, it means that the DCDC conversion circuit has no bias and continues to work normally; if so, the output of the differential filter circuit is subtracted from the bias. If the result is not 0, it means that there is bias. At this time, the feedback adjusts the duty cycle of the corresponding switch tube. Among them, if the output of the differential filter circuit is 0 after subtracting the bias, it means that there is no bias and the DCDC conversion circuit continues to work normally.

[0104] An embodiment of the present application further provides a power conversion device, the power conversion device comprising the DCDC conversion circuit described above. The specific structure and principle of the DCDC conversion circuit can refer to the above embodiments, and this implementation will not be repeated here.

[0105] In this article, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be noted that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0106] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A DCDC conversion circuit, characterized in that: include: A transformer and a main power circuit electrically connected to the transformer; a current detection circuit connected between the transformer and the main power circuit and configured to detect a positive half-cycle current and a negative half-cycle current, and generate a full-wave DC component based on the positive half-cycle current and the negative half-cycle current; The control circuit is electrically connected to the current detection circuit and is configured to adjust the conduction time of the power tube in the main power circuit according to the full-wave DC component so that the full-wave DC component tends to zero.

2. The DCDC conversion circuit according to claim 1, characterized in that: The current detection circuit comprises: A sampling circuit, comprising a current sampling transformer coupled between the transformer and the main power loop, and configured to detect a positive half-cycle current and a negative half-cycle current through the current sampling transformer; The differential circuit is electrically connected to the sampling circuit and is configured to perform differential processing on the positive half-cycle current and the negative half-cycle current and output the full-wave DC component.

3. The DCDC conversion circuit according to claim 2, characterized in that: The sampling circuit comprises: A first current sampling transformer, comprising a primary winding and a secondary winding, wherein the primary winding is coupled between the transformer and the main power loop; a first unidirectional loop, wherein an input side of the first unidirectional loop is electrically connected to a first end of the secondary winding; a second unidirectional loop, wherein an input side of the second unidirectional loop is electrically connected to a second end of the secondary winding; a freewheeling circuit, electrically connected to the output side of the first unidirectional circuit, the output side of the second unidirectional circuit and a middle tap of the secondary winding respectively; Wherein, the first unidirectional loop and the second unidirectional loop are both provided with a sampling output node, and the sampling output node is electrically connected to the differential circuit.

4. The DCDC conversion circuit according to claim 3, characterized in that: The differential circuit comprises: a first operational amplifier, wherein a non-inverting input terminal of the first operational amplifier is electrically connected to the sampling output node of the first unidirectional loop, and an inverting input terminal of the first operational amplifier is electrically connected to the sampling output node of the second unidirectional loop; A first feedback unit, electrically connected between the inverting input terminal and the output terminal of the first operational amplifier; The first bias circuit is electrically connected to the non-inverting input terminal of the first operational amplifier.

5. The DCDC conversion circuit according to claim 2, characterized in that: The sampling circuit comprises: A second current sampling transformer, comprising a primary winding and a secondary winding, wherein the primary winding is coupled between the transformer and the main power loop; a third unidirectional loop, wherein an input side of the third unidirectional loop is electrically connected to a first end of the secondary winding, and an input side of the third unidirectional loop is electrically connected to a second end of the secondary winding; a fourth unidirectional loop, wherein an input side of the fourth unidirectional loop is electrically connected to the second end of the secondary winding, and an input side of the fourth unidirectional loop is electrically connected to the first end of the secondary winding; Wherein, the third unidirectional loop and the fourth unidirectional loop are both provided with a sampling output node, and the sampling output node is electrically connected to the differential circuit.

6. The DCDC conversion circuit according to claim 5, characterized in that: The differential circuit comprises: a first differential operational amplifier circuit, wherein an input terminal of the first differential operational amplifier circuit is electrically connected to the sampling output node of the third unidirectional loop; a second differential operational amplifier circuit, wherein an input terminal of the second differential operational amplifier circuit is electrically connected to the sampling output node of the fourth unidirectional loop; a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is electrically connected to an output terminal of the first differential operational amplifier circuit, and an inverting input terminal of the second operational amplifier is electrically connected to an output terminal of the second differential operational amplifier circuit; A second feedback unit, electrically connected between the inverting input terminal and the output terminal of the second operational amplifier; The second bias circuit is electrically connected to the non-inverting input terminal of the second operational amplifier.

7. The DCDC conversion circuit according to any one of claims 1 to 6, characterized in that: The control circuit includes a controller, the controller is configured with a main feedback loop and a bias magnetic feedback loop, and the bias magnetic feedback loop is electrically connected to the current detection circuit; Wherein, the crossover frequency of the bias magnetic feedback loop is lower than the crossover frequency of the main feedback loop.

8. The DCDC conversion circuit according to any one of claims 1 to 6, characterized in that: The DCDC conversion circuit further includes: a resonance unit, wherein a first end of the resonance unit is electrically connected to a first side of the transformer; a conversion circuit, wherein a first side of the conversion circuit is electrically connected to a second end of the resonance unit; The second side of the transformer is electrically connected to the main power circuit, and both the main power circuit and the conversion circuit are H-bridge switching circuits.

9. A method for controlling the bias magnetic field of a DCDC conversion circuit, characterized in that: include: Obtaining the positive half-cycle current and the negative half-cycle current of the primary side of the transformer in the DCDC conversion circuit; Determine the DC component of the full cycle according to the positive half-cycle current and the negative half-cycle current; The switch duty ratio of the primary side conversion circuit connected to the primary side of the transformer is adjusted according to the DC component.

10. The bias magnetic control method according to claim 9, characterized in that: The step of adjusting the switch duty ratio of the primary side conversion circuit connected to the primary side of the transformer according to the DC component comprises: When the DC component is positive, reducing the switch duty cycle of the power tube corresponding to the positive half cycle in the primary conversion circuit; When the DC component is negative, the switch duty cycle of the power tube corresponding to the negative half cycle in the primary conversion circuit is reduced.

11. A power conversion device, characterized in that: It comprises the DCDC conversion circuit according to any one of claims 1-8.

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