Resonance parameter determination method and apparatus, electronic device, and storage medium
By adjusting the resonant inductor and capacitor parameters of the bidirectional LLC resonant converter, the current difference of the reverse current during the dead time is increased, which solves the transformer oversaturation problem caused by DC bias and improves the converter's conversion efficiency and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ECOFLOW INC
- Filing Date
- 2023-03-21
- Publication Date
- 2026-06-26
AI Technical Summary
During the discharge process of a bidirectional LLC resonant converter, the lack of a capacitor on the secondary side of the transformer for DC blocking leads to inconsistent duty cycles between the upper and lower switching transistors. This results in inconsistent maximum and minimum excitation current values, causing DC bias, increasing magnetic losses, and even damaging the transformer, thus affecting conversion efficiency.
By increasing the inductance of the resonant inductor and decreasing the capacitance of the resonant capacitor while keeping the operating frequency constant, the resonant parameters are adjusted to calculate the circuit gain, determine the selection reference parameters, increase the current difference of the reverse current in the dead time, and decrease the DC bias.
It effectively reduces DC bias, suppresses transformer magnetization, reduces the risk of oversaturation, improves conversion efficiency, and ensures normal operation of the converter.
Smart Images
Figure CN116232087B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic technology, and in particular to a method and apparatus for determining resonance parameters, electronic equipment, and storage medium. Background Technology
[0002] A bidirectional LLC resonant converter is a DC / DC conversion circuit that enables bidirectional energy transfer. Typically, the primary side of a bidirectional LLC resonant converter is the high-voltage side, used to power the load or receive power from a source, while the secondary side is the low-voltage side, used to connect a battery. That is, the bidirectional LLC resonant converter can charge the battery using an external power source and discharge the battery using its own energy. During the discharge process, that is, the transfer of energy from the transformer secondary side to the transformer primary side, because the secondary side lacks a capacitor for DC blocking, the alternating conduction of the upper and lower switching transistors in the AC / DC conversion circuit on the secondary side will result in inconsistent duty cycles; that is, the conduction durations of the upper and lower switching transistors will differ.
[0003] In this situation, the maximum and minimum values of the transformer's excitation current will be inconsistent, resulting in a large DC bias in the bidirectional LLC resonant converter. The presence of DC bias will cause the transformer to become magnetized, thereby increasing the risk of transformer oversaturation, increasing the transformer's magnetic losses, reducing the circuit's conversion efficiency, and even damaging the transformer, causing the bidirectional LLC resonant converter to malfunction. Summary of the Invention
[0004] In view of this, this application provides a method and apparatus for determining resonance parameters, an electronic device and a storage medium, which can determine suitable resonance parameters for a bidirectional LLC resonant converter, thereby enabling the bidirectional LLC resonant converter to achieve higher conversion efficiency.
[0005] Firstly, this application provides a method for determining resonant parameters, applicable to bidirectional LLC resonant converters. This method includes obtaining first resonant parameters of the bidirectional LLC resonant converter at a preset operating frequency, wherein the first resonant parameters include the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the bidirectional LLC resonant converter. Then, while keeping the operating frequency constant, the inductance value of the resonant inductor is increased while the capacitance value of the resonant capacitor is decreased to obtain second resonant parameters. Next, the circuit gain of the bidirectional LLC resonant converter is calculated based on the second resonant parameters, and then, based on the circuit gain and the second resonant parameters, selection reference parameters for the bidirectional LLC resonant converter are determined.
[0006] Based on this design, it is beneficial to determine suitable resonance parameters for the bidirectional LLC resonant converter. This allows the bidirectional LLC resonant converter to achieve better DC bias correction capability simply by changing the resonance parameters without adding components or changing other parameters. This avoids the problem of transformer oversaturation caused by DC bias, which can lead to increased transformer magnetic losses, reduced circuit conversion efficiency, and even damage to the transformer, causing the bidirectional LLC resonant converter to malfunction.
[0007] In one embodiment, while keeping the operating frequency constant, during the process of increasing the inductance value of the resonant inductor and simultaneously decreasing the capacitance value of the resonant capacitor, the proportion of the increase in the inductance value of the resonant inductor and the proportion of the decrease in the capacitance value of the resonant capacitor are reciprocals of each other.
[0008] In one embodiment, the inductance value of the resonant inductor is increased by a ratio between 1 and 2.
[0009] In one embodiment, during the process of determining the selection reference parameters for the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameter, if the circuit gain is greater than a preset lower gain threshold, the process returns to the step of increasing the inductance value of the resonant inductor and simultaneously decreasing the capacitance value of the resonant capacitor while keeping the operating frequency constant. When the circuit gain is equal to the preset lower gain threshold, the corresponding second resonant parameter is determined as the selection reference parameter. When the circuit gain is less than the preset lower gain threshold, the previously adjusted second resonant parameter is obtained and used as the selection reference parameter. In one embodiment, after determining the selection reference parameters for the bidirectional LLC resonant converter, the models of the resonant inductor and resonant capacitor and their corresponding selection parameters can be quickly determined based on the selection reference parameters.
[0010] In one embodiment, after determining the models and corresponding selection parameters of the resonant inductor and resonant capacitor, the circuit gain corresponding to the selection parameters can be calculated. Then, when the circuit gain is greater than or equal to a preset lower gain threshold, the selection parameters are determined as the final resonant parameters. When the circuit gain is less than the preset lower gain threshold, the previously adjusted second resonant parameter is determined as the selection reference parameter. In one embodiment, the first resonant parameter can be determined based on the preset quality factor, preset resonant frequency, maximum input voltage, and maximum output power of the bidirectional LLC resonant converter, such that the resonant frequency corresponding to the first resonant parameter is greater than or equal to the preset resonant frequency, and the circuit gain of the bidirectional LLC resonant converter is within the preset gain range.
[0011] Secondly, this application also provides a resonant parameter determination device applicable to a bidirectional LLC resonant converter. This device includes an acquisition module, an adjustment module, a calculation module, and a determination module. The acquisition module acquires the first resonant parameter of the bidirectional LLC resonant converter at a preset operating frequency, wherein the resonant parameter includes the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the bidirectional LLC resonant converter. The adjustment module increases the inductance value of the resonant inductor while simultaneously decreasing the capacitance value of the resonant capacitor, while keeping the operating frequency constant, to obtain the second resonant parameter. The calculation module calculates the circuit gain of the bidirectional LLC resonant converter based on the second resonant parameter. The determination module determines the selection reference parameters of the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameter.
[0012] Thirdly, this application also provides an electronic device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to perform the resonance parameter determination method described in the first aspect or any embodiment of the first aspect.
[0013] Fourthly, this application also provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the resonance parameter determination method described in the first aspect or any embodiment of the first aspect.
[0014] Compared with the prior art, this application has the following advantages:
[0015] In the resonant parameter determination method, apparatus, electronic device, and storage medium of this application, without changing other parameters of the bidirectional LLC resonant converter or adding components, the resonant inductance value of the bidirectional LLC resonant converter is increased, the resonant capacitance value is decreased, and the second resonant parameter is verified using circuit gain. This allows the determination of selection reference parameters for the bidirectional LLC resonant converter, facilitating the selection of resonant parameters. Furthermore, after selecting the resonant parameters, the selected resonant parameters are verified again using circuit gain, thereby determining the final resonant parameters of the bidirectional LLC resonant converter.
[0016] Increasing the resonant inductance and decreasing the resonant capacitance increases the magnetizing current of the bidirectional LLC resonant converter, thereby increasing the reverse current during the dead time of the upper and lower switches. This increased reverse current reduces the difference between the maximum and minimum magnetizing current, thus decreasing the DC bias of the bidirectional LLC resonant converter.
[0017] Therefore, the resonant parameter determination method, apparatus, electronic device, and storage medium of this application can effectively reduce the DC bias of the bidirectional LLC resonator and suppress transformer bias simply by changing the resonant parameters, thereby improving the DC bias correction capability of the bidirectional LLC resonant converter. Furthermore, this reduces the risk of transformer oversaturation, improves the conversion efficiency of the bidirectional LLC resonant converter, and ensures more reliable normal operation of the bidirectional LLC resonant converter. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.
[0019] Figure 1 This is a schematic diagram of a bidirectional LLC resonant converter.
[0020] Figure 2 This is a flowchart of the resonance parameter determination method provided in the embodiments of this application.
[0021] Figure 3 yes Figure 2 The flowchart for step S3 in the process.
[0022] Figure 4 This is another flowchart of the resonance parameter determination method provided in the embodiments of this application.
[0023] Figure 5 This is another flowchart of the resonance parameter determination method provided in the embodiments of this application.
[0024] Figure 6 This is a simulation diagram of a bidirectional LLC resonant converter in its first operating mode.
[0025] Figure 7 This is a simulation diagram of a bidirectional LLC resonant converter in its second operating mode.
[0026] Figure 8 This is a simulation diagram of a bidirectional LLC resonant converter in its third operating mode.
[0027] Figure 9 This is another simulation diagram of the bidirectional LLC resonant converter in the third operating mode.
[0028] Figure 10 This is a simulation diagram of the primary voltage waveform of the transformer under the third operating mode.
[0029] Figure 11 This is another simulation diagram of the transformer primary voltage waveform under the third operating mode.
[0030] Figure 12This is a simulation diagram of a bidirectional LLC resonant converter after changing the resonant parameters in the third operating mode.
[0031] Figure 13 This is a structural block diagram of the resonance parameter determination device provided in the embodiments of this application.
[0032] Figure 14 This is a structural block diagram of the electronic device provided in the embodiments of this application.
[0033] Explanation of main component symbols
[0034] Resonance parameter determination device—10 Acquisition module—101 Adjustment module—102
[0035] Calculation Module—103 Determination Module—104
[0036] Electronic devices—20 Processor—201 Memory—202
[0037] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation
[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.
[0039] It is understood that the connection relationships described in this application refer to direct or indirect connections. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For instance, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C. It is also understood that the "A connects to B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.
[0040] In the description of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.
[0041] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, nor do they imply that they must be different. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.
[0042] Please see Figure 1The diagram shows the circuit diagram of a bidirectional LLC resonant converter. Specifically, the bidirectional LLC resonant converter includes an AC / DC converter circuit, a DC / AC converter circuit, capacitors Cbus and Co, a resonant circuit, and a transformer Tr. The AC / DC converter circuit is located on the secondary side of the transformer Tr, the DC / AC converter circuit is located on the primary side of the transformer Tr, and the resonant circuit is connected between the DC / AC converter circuit and the primary side of the transformer.
[0043] The AC / DC conversion circuit can be a full-bridge switching circuit or a half-bridge switching circuit. For ease of description, we will use a full-bridge switching circuit as an example.
[0044] like Figure 1 As shown, the AC / DC converter circuit includes two bridge arms. One bridge arm consists of an upper switch Q5 and a lower switch Q6, and the other bridge arm consists of an upper switch Q7 and a lower switch Q8. During AC / DC conversion, upper switch Q5 and lower switch Q8 form one group, and upper switch Q7 and lower switch Q6 form the other group. Switches in the same group are turned on or off simultaneously. Different groups of switches are turned on alternately; that is, in each cycle, one group of switches is turned on for half of the cycle, and the other group is turned on for the other half. Furthermore, after one group of switches is turned off, the other group of switches is turned on after a dead time delay.
[0045] The structure of a DC / AC converter circuit is the same as or similar to that of an AC / DC converter circuit, and will not be described in detail here. It can be understood that the state of the switching transistors in both DC / AC and AC / DC converter circuits can be controlled by a controller (…). Figure 1 (Not shown in the image) Control.
[0046] Capacitor Cbus is connected in parallel with the bridge arm of the DC / AC converter circuit, and both are connected to the DC bus. Capacitor Co is connected in parallel with the bridge arm of the AC / DC converter circuit.
[0047] The resonant circuit includes a resonant inductor Lr and a resonant capacitor Cr.
[0048] The primary winding of transformer Tr has an equivalent inductance, which excites the core of transformer Tr, enabling the core to conduct magnetism. Therefore, this equivalent inductance can be called the magnetizing inductance Lm, and can be equivalently connected in parallel with the primary winding of transformer Tr (see [link to relevant documentation]). Figure 1 (The dashed line in the diagram). The current in the magnetizing inductor Lm is the magnetizing current Im.
[0049] In practical applications, the primary side of transformer Tr is typically used as the high-voltage side, supplied to the load connected to the DC bus via a resonant circuit and a DC / AC converter circuit. Figure 1 (Not shown in the image) Power supply or receiving power ( Figure 1The power supply (not shown in the diagram) is provided by the secondary side of transformer Tr, which serves as the low-voltage side and is used to connect the battery (not shown in the diagram) via an AC / DC converter circuit. Figure 1 (Not shown in the image). Thus, the bidirectional LLC resonant converter can use an external power supply to charge the battery. The bidirectional LLC resonant converter can also use the battery's electrical energy to discharge externally, in order to convert the input voltage Vin (i.e., the voltage of capacitor Co) into the output voltage Vout (i.e., the voltage of capacitor Cbus).
[0050] However, during the discharge process of the bidirectional LLC resonant converter, that is, during the transfer of energy from the secondary side of the transformer Tr to the primary side, the secondary side voltage contains a DC component because there is no capacitor for DC blocking on the secondary side. This causes inconsistencies in the duty cycles of the upper and lower switches in different groups (i.e., the same bridge arm) of the AC / DC conversion circuit; for example, the duty cycles of Q5 and Q6 are not both 0.5. Therefore, this results in different conduction times for the upper and lower switches in different groups (i.e., the same bridge arm).
[0051] In this case, the maximum and minimum values of the excitation current of transformer Tr will be inconsistent, resulting in a large DC bias in the bidirectional LLC resonant converter.
[0052] The presence of DC bias will cause the transformer Tr to become magnetized. That is, the volt-seconds (V*T) of the primary side of the transformer Tr will not be equal in the two half-cycles (i.e., the duration of one half-cycle multiplied by the primary voltage of the transformer Tr in that half-cycle is not equal to the duration of the other half-cycle multiplied by the primary voltage of the transformer Tr in that half-cycle; this can also be understood as the two half-wave areas of the primary voltage waveform of the transformer Tr being unequal in the same cycle, often referred to as volt-second imbalance). This will cause the core hysteresis loop of the transformer Tr to deviate, leading to oversaturation of the transformer Tr, which in turn increases the magnetic losses of the transformer Tr, reduces the conversion efficiency of the bidirectional LLC resonant converter, and may even damage the transformer Tr, causing the bidirectional LLC resonant converter to malfunction. However, during the charging process of the bidirectional LLC resonant converter, because the primary side has a resonant capacitor Cr for DC blocking, the above-mentioned DC bias problem does not exist during the charging process.
[0053] In response, this application provides a method, apparatus, electronic device, and storage medium for determining resonant parameters. These can be used to determine the resonant parameters in a bidirectional LLC resonant converter, thereby achieving better DC bias correction capability simply by changing the resonant parameters without adding components or changing other parameters. This avoids transformer oversaturation caused by DC bias, which increases transformer magnetic losses, reduces circuit conversion efficiency, and may even damage the transformer, leading to the bidirectional LLC resonant converter malfunctioning.
[0054] The technical solution of this application will be further described in detail below with reference to the accompanying drawings.
[0055] Please see Figure 2 This is a flowchart illustrating a method for determining resonance parameters provided in an embodiment of this application. It is understood that the steps of the method or algorithm described in this application embodiment can be directly embedded into the controller of an electronic device or a bidirectional LLC resonant converter, so that the electronic device or controller can execute some or all of the steps of the resonance parameter determination method.
[0056] Specifically, such as Figure 2 As shown, the methods for determining resonance parameters include:
[0057] Step S1: Obtain the first resonant parameters of the bidirectional LLC resonant converter at the preset operating frequency fn. The resonant parameters include the inductance value of the resonant inductor Lr and the capacitance value of the resonant capacitor Cr in the bidirectional LLC resonant converter.
[0058] In step S1, the first resonance parameter can be understood as the initial resonance parameter of the bidirectional LLC resonant converter, that is, the initial inductance value of the resonant inductor Lr and the initial capacitance value of the resonant capacitor Cr. Its value can be set according to the actual situation, and this application does not make specific limitations on it.
[0059] For example, in some implementations, the first resonant parameters can be determined by calculation using theoretical formulas based on the preset quality factor Q, preset resonant frequency fr, maximum input voltage Voutmax, and maximum output power Poutmax of the bidirectional LLC resonant converter.
[0060] The theoretical calculation formula is as follows:
[0061] Q = 0.8Q max
[0062]
[0063] Circuit gain k is the ratio of the magnetizing inductance to the resonant inductance, and k is a known parameter.
[0064] Resonant inductor
[0065] The equivalent resistance of the secondary side of transformer Tr to the primary side n is the turns ratio of the primary and secondary coils of transformer Tr.
[0066] Resonant capacitor
[0067] Magnetizing inductance L m =k·L r
[0068] The above calculation process is a commonly used calculation process in this field. It is understood that the first resonance parameter can also be obtained through other calculation methods in other embodiments.
[0069] Step S2: While keeping the operating frequency fn constant, increase the inductance value of the resonant inductor Lr and simultaneously decrease the capacitance value of the resonant capacitor Cr to obtain the second resonant parameter.
[0070] It can be seen that step S2 is to adjust the first resonant parameter, without changing other parameters in the bidirectional LLC resonant converter, and without adding any components.
[0071] Step S3: Calculate the circuit gain of the bidirectional LLC resonant converter based on the second resonant parameters.
[0072] In step S3, the circuit gain corresponding to the second resonance parameter can be calculated using the theoretical calculation formula for the circuit gain in step S1 above.
[0073] Step S4: Determine the selection reference parameters for the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameter.
[0074] Thus, the selection reference parameters determined in step S4 not only increase the inductance value of the resonant inductor Lr and decrease the capacitance value of the resonant capacitor Cr, but also enable the bidirectional LLC resonant converter to have a large circuit gain.
[0075] In this embodiment of the application, step S4 may involve comparing the circuit gain corresponding to the second resonance parameter calculated in step S3 with a preset lower limit threshold of gain, thereby confirming the magnitude of the circuit gain.
[0076] It is understandable that steps S2 to S3 above can be executed multiple times. Therefore, in step S4, the circuit gain corresponding to the second resonant parameter can be compared with the preset lower gain threshold multiple times, thereby determining the second resonant parameter corresponding to a circuit gain that is not less than the preset lower gain threshold and is closest to the preset lower gain threshold. This second resonant parameter can be used as a selection reference parameter, enabling the bidirectional LLC resonant converter to have the maximum circuit gain while increasing the inductance value of the resonant inductor Lr and decreasing the capacitance value of the resonant capacitor Cr.
[0077] Obviously, based on the above design, the method of this application can determine the selection reference parameters for the design of the resonant parameters of the bidirectional LLC resonant converter, which facilitates the selection of resonant parameters.
[0078] Furthermore, the method in this application increases the inductance value of the resonant inductor Lr when adjusting the resonant parameters. An increase in inductance means more energy can be stored in the resonant inductor Lr, leading to an increase in the primary current during discharge. Therefore, the magnetizing current Im can be increased. An increase in the magnetizing current Im increases the reverse current during the dead time of different sets of upper and lower switches, thereby reducing the difference between the maximum and minimum values of the magnetizing current Im, and thus reducing the DC bias of the bidirectional LLC resonant converter.
[0079] Therefore, the selection reference parameters determined by the method of this application can also help reduce the DC bias of the bidirectional LLC resonant converter and suppress the transformer bias, thereby reducing the risk of transformer oversaturation, reducing transformer magnetic losses, improving the conversion efficiency of the bidirectional LLC resonant converter, and ensuring the normal operation of the bidirectional LLC resonant converter.
[0080] Furthermore, since the selection reference parameters are determined based on the circuit gain in this application, these parameters can be understood as the resonant parameters that enable the bidirectional LLC resonant converter to generate the maximum reverse current during the dead time when the inductance value of the resonant inductor Lr increases and the capacitance value of the resonant capacitor Cr decreases, while other parameters remain unchanged. In other words, the selection reference parameters determined by the method in this application can maximize the correction capability of the bidirectional LLC resonant converter.
[0081] As can be understood, as mentioned above, the selected reference parameters can help increase the reverse current during the dead time, thereby reducing the DC bias. However, when the preset operating frequency fn is higher than the resonant frequency fr corresponding to the first resonant parameter, the resonant circuit becomes capacitive, and the current leads the voltage. This makes it difficult for the bidirectional LLC resonant converter to generate reverse current during the dead time, thus suppressing its ability to correct the DC bias. Therefore, in this embodiment, it is necessary to control the operating frequency fn of the selected resonant circuit to be less than or equal to the preset resonant frequency fr. That is to say, the method in this embodiment is applied to parameter selection in scenarios where the bidirectional LLC resonant converter operates in the condition fn ≤ fr.
[0082] In this embodiment, the circuit gain of the bidirectional LLC resonant converter is within a preset gain range. This is mainly because the circuit gain is related to k, Q, and fn. When fn of the bidirectional LLC resonant converter is within a certain frequency range (i.e., fn≤fr), the circuit gain is also within the corresponding preset gain range.
[0083] In the embodiments of this application, the method of increasing the resonant inductance and decreasing the resonant capacitance in step S2 does not constitute a limitation of this application.
[0084] For example, in this embodiment, step S2 can involve proportionally increasing the inductance value of the resonant inductor while keeping the operating frequency fn constant, and simultaneously proportionally decreasing the capacitance value of the resonant capacitor. The proportion by which the inductance value of the resonant inductor increases and the proportion by which the capacitance value of the resonant capacitor decreases are reciprocals of each other.
[0085] Based on this design, on the one hand, it ensures that the resonant frequency fr remains constant, avoiding changes in fr that would increase the complexity of the method and make it difficult to determine the selection reference parameters. On the other hand, it makes the adjustment of the resonant parameters regular, facilitating the rapid determination of the selection reference parameters in the subsequent step S4.
[0086] It is understood that the magnitude of the increase in inductance and the magnitude of the decrease in capacitance do not constitute a limitation on this application. In the embodiments of this application, the percentage increase in inductance can be set to be between 1 and 2. For example, the percentage increase in inductance can be 1.01, 1.1, 1.5, 1.99, or other values between 1 and 2. Correspondingly, the percentage decrease in capacitance can be between 0.5 and 1.
[0087] In this way, the resonant inductance can be increased while the resonant capacitance can be reduced. At the same time, it is possible to avoid a significant increase in the power consumption of the bidirectional LLC resonant converter due to an excessive increase in the resonant inductance. Therefore, it is beneficial to ensure the conversion efficiency of the bidirectional LLC resonant converter.
[0088] In this embodiment of the application, as described above, step S4 involves determining the selection reference parameters based on the circuit gain and the second resonant parameters. Therefore, specifically, as follows: Figure 3 As shown, step S4 may include the following steps:
[0089] Step S41: When the circuit gain is greater than the preset lower gain threshold, return to step S2.
[0090] This is mainly because when the circuit gain is greater than the preset lower limit threshold, it is still unknown whether the circuit gain corresponding to the next adjusted resonance parameter will be no less than and closer to the preset lower limit threshold. Therefore, in this case, we return to step S2 to continue to find the second resonance parameter when the circuit gain is no less than and closer to the preset lower limit threshold.
[0091] Step S42: When the circuit gain is equal to the preset lower gain threshold, determine the corresponding second resonant parameter as the selection reference parameter.
[0092] It is understandable that when the circuit gain equals the preset lower gain threshold, no other circuit gain will be closer to the preset lower gain threshold. Therefore, in this case, the second resonant parameter can be directly used as the selection reference parameter.
[0093] Step S43: When the circuit gain is less than the preset lower gain threshold, obtain the second resonance parameter that was adjusted last time, and use the second resonance parameter that was adjusted last time as the selection reference parameter.
[0094] This is mainly because when the circuit gain is less than the preset lower limit threshold, it is obviously because the resonant parameter has been over-adjusted, causing the circuit gain to fail to meet the condition of not being less than the preset lower limit threshold. The second resonant parameter that was adjusted last time must meet the condition of not being less than the preset lower limit threshold. Therefore, in this case, the second resonant parameter that was adjusted last time is used as the selection reference parameter.
[0095] Therefore, since the resonant parameters are adjusted proportionally in step S2 of this embodiment, by analyzing whether the circuit gain is equal to, less than, or greater than the preset lower gain threshold, it can be easily determined whether the circuit gain corresponding to the current adjustment is closest to the preset lower gain threshold. Thus, the selection reference parameters can be determined systematically and efficiently.
[0096] Clearly, the selection reference parameters can serve as the basis for selecting resonant inductors and resonant capacitors. Therefore, as... Figure 4 As shown, in some embodiments of this application, the method may further include the following steps:
[0097] Step S5: Determine the model of the resonant inductor and resonant capacitor and the corresponding selection parameters according to the selection reference parameters. This makes the selection of resonant parameters efficient and quick.
[0098] Considering that in practice, it is difficult to find inductors and capacitors with specifications that perfectly match the selection reference parameters, the selection parameters will often differ in magnitude from the reference parameters. This could cause the circuit gain of the bidirectional LLC resonant converter to fall below the preset lower gain threshold after adopting the selected parameters. Clearly, this result contradicts step S4 and fails to achieve the desired improvement in the bidirectional LLC resonant converter's bias correction capability. Therefore, in some embodiments of this application, after determining the models and corresponding selection parameters of the resonant inductor and capacitor, the circuit gain is verified again.
[0099] Specifically, such as Figure 5 As shown, the method may also include the following steps:
[0100] Step S6: Calculate the circuit gain corresponding to the selection parameters.
[0101] Step S7: Determine whether the circuit gain is greater than or equal to the preset lower gain threshold.
[0102] When the circuit gain is greater than or equal to the preset lower gain threshold, proceed to step S8.
[0103] When the circuit gain is less than the preset gain lower threshold, step S9 is entered.
[0104] Step S8: Determine the selected parameters as the final resonance parameters;
[0105] Step S9: Determine the second resonance parameters of the previous adjustment as the reference parameters for selection. Furthermore, return to execute steps S5 - S7.
[0106] Based on such a design, it can be ensured that the circuit gain of the determined final resonance parameters is not less than the preset gain lower threshold, so as to ensure that after the bidirectional LLC resonant converter adopts the final resonance parameters, a reverse current can be generated within the dead time, so that the DC bias is improved, and the volt - second numbers of the primary and secondary sides of the transformer become balanced within a half - cycle. Therefore, the magnetic bias of the transformer can be suppressed, and further the risk of transformer saturation can be reduced, the magnetic loss of the transformer can be reduced, the conversion efficiency of the bidirectional LLC resonant converter is improved, and the normal operation of the bidirectional LLC resonant converter is effectively guaranteed.
[0107] Moreover, the above design only changes the resonance parameters, does not change other parameters of the bidirectional LLC resonant converter, and does not add components. Therefore, the method of the embodiment of the present application is simple, easy to implement, and does not increase costs.
[0108] For better understanding, the method of the embodiment of the present application will be further described through simulation experiments below.
[0109] In the simulation experiment, it is set that Figure 1 the resonance frequency fr of the shown bidirectional LLC resonant converter is 80 kHz, the initial capacitance value of the resonant capacitor Cr in the first resonance parameters is 66 nF, and the initial inductance value of the resonant inductor Lr is 58 μH. Then, the discharge processes of the bidirectional LLC resonant converter in the first operating mode (operating frequency fn > fr), the second operating mode (operating frequency fn = fr), and the third operating mode (operating frequency fn < fr) are respectively simulated to analyze the magnetic bias situation of the transformer Tr.
[0110] Specifically, please refer to Figure 6 , which shows the output voltage (i.e., Figure 1 Vout in
[0111] and the excitation current Im waveforms of the bidirectional LLC resonant converter in the first operating mode.
[0112] Therefore, we can deduce that the on-time of the upper switch Q5 is 1 / 90k * 0.487 = 5.411µs, and the dead time is 1 / 90k * (0.5 - 0.487) = 144.444ns. The on-time of the lower switch Q6 is 1 / 90k * 0.493 = 5.478µs, and the dead time is 1 / 90k * (0.5 - 0.493) = 77.778ns. Therefore, the on-time difference between Q5 and Q6 is 5.478µs - 5.411µs = 67ns.
[0113] from Figure 6 It can be seen that when the output voltage Vout stabilizes (i.e. Figure 6 The output voltage waveform is linear. The peaks and troughs of the excitation current Im on the primary side of transformer Tr are inconsistent. The maximum value of Im is -25.364A, and the minimum value is -61.944A. Therefore, the DC bias current is the average of the maximum and minimum values, i.e., (-25.364A-61.944A) / 2=-43.654A.
[0114] Please see Figure 7 The output voltage Vout and excitation current Im waveforms of the bidirectional LLC resonant converter in the second operating mode are shown.
[0115] In the second operating mode, fn = 80kHz, and the duty cycles of the upper switch Q5 and the lower switch Q6 are the same as those in the first operating mode.
[0116] Therefore, we can deduce that the on-time of the upper switch Q5 is 1 / 80k * 0.487 = 6.088µs, and the dead time is 1 / 80k * (0.5 - 0.487) = 162.5ns. The on-time of the lower switch Q6 is 1 / 80k * 0.493 = 6.163µs, and the dead time is 1 / 80k * (0.5 - 0.493) = 87.5ns. Therefore, the on-time difference between Q5 and Q6 is 6.163µs - 6.088µs = 75ns.
[0117] from Figure 7 It can be seen that after the output voltage Vout stabilizes, the peak and trough of the excitation current Im waveform are still inconsistent. The maximum value of Im is 10.18A, and the minimum value of Im is -30.852A. Therefore, the DC bias current is (10.18A-30.852A) / 2=-10.336A.
[0118] Clearly, the DC bias current of the second operating mode is smaller than that of the first operating mode. This also reflects that the first operating mode has difficulty generating reverse current during the dead time, thus resulting in a more severe DC bias and a poorer bias correction capability of the bidirectional LLC resonant converter.
[0119] Please see Figure 8 The output voltage Vout and excitation current Im waveforms of the bidirectional LLC resonant converter in the third operating mode are shown.
[0120] In the third operating mode, fn = 70kHz, the duty cycles of the upper switch Q5 and the lower switch Q6 are the same as those in the first operating mode.
[0121] Therefore, we can deduce that the on-time of the upper switch Q5 is 1 / 70k * 0.487 = 6.957µs, and the dead time is 1 / 70k * (0.5 - 0.487) = 185.714ns. The on-time of the lower switch Q6 is 1 / 70k * 0.493 = 7.043µs, and the dead time is 1 / 70k * (0.5 - 0.493) = 100ns. Therefore, the on-time difference between Q5 and Q6 is 7.043µs - 6.957µs = 86ns.
[0122] from Figure 8 It can be seen that the maximum value of the excitation current Im is 7.57A, and the minimum value of Im is -39.33A. Therefore, the DC bias current is (7.57A-39.33A) / 2=-15.88A.
[0123] To facilitate comparison with the second operating mode, the conduction time difference between Q5 and Q6 in the third operating mode needs to be adjusted to match the conduction time difference in the second operating mode. Therefore, the duty cycles of the upper switch Q5 and the lower switch Q6 are changed to 0.48775 and 0.493, respectively. Correspondingly, the dead times of the upper switch Q5 and the lower switch Q6 are 175ns and 100ns, respectively. The waveform of the excitation current Im can be found in [reference needed]. Figure 9 .
[0124] from Figure 9 It can be seen that the maximum value of the excitation current Im is 8.655A, and the minimum value of Im is -38.326A. Therefore, the DC bias current is (8.655-38.326A) / 2 = -14.836A. Obviously, the DC bias current is smaller compared to the second operating mode.
[0125] And from Figure 10 As can be seen from the primary voltage waveform of transformer Tr shown, within one cycle, the primary voltage waveform of transformer Tr includes three parts: P1 to P3.
[0126] Wherein, P1 is the primary voltage waveform when the upper switch Q5 is turned on (that is, the lower switch Q6 is turned off), the voltage of P1 is represented as V1, and the time of P1 (that is, the on time of the upper switch Q5) is t1 = 7.04us.
[0127] P2 is the primary-side voltage waveform during the dead time (i.e., both the upper switch Q5 and the lower switch Q6 are off). The voltage of P2 is denoted as V2, and the time of P2 (i.e., the dead time) is t2 = 144 ns.
[0128] P3 is the primary-side voltage waveform when the lower switch Q6 is on (i.e., the upper switch Q5 is off). The voltage of P3 is denoted as V3, and the time of P3 (i.e., the on-time of the upper switch Q5) is t3 = 7.187 us.
[0129] It can be understood that the reason for the existence of P2 is that fn < fr, the resonant circuit is inductive, the current lags behind the voltage. When t1 ends, the magnetizing current is still freewheeling. During t2, the upper switch Q5 is off and the lower switch Q6 has not turned on yet, causing the current to reverse, resulting in a reverse increase in the primary-side voltage of the transformer Tr. Therefore, a protrusion P2 appears in the primary-side voltage waveform at t2.
[0130] Based on this, although t3 > t1, making the volt-seconds (which can be understood as the waveform area corresponding to the negative voltage) V3 * t3 of the negative voltage of the transformer Tr greater than V1 * t1, due to the existence of P2, the volt-seconds (which can be understood as the waveform area corresponding to the positive voltage) of the positive voltage becomes V1 * t1 + V2 * t2. Therefore, the gap between the volt-seconds of the positive and negative voltages can be reduced, resulting in a decrease in the DC bias current.
[0131] Thus, it can be seen that in the third operating mode, due to the existence of a reverse current during the dead time, the DC bias current can be reduced, and the bidirectional LLC resonant converter obtains the ability to correct the bias.
[0132] Continuing on the basis of the third operating mode, the duty cycles of the upper switch Q5 and the lower switch Q6 are changed to 0.4807 and 0.486 respectively. Correspondingly, the dead times of the upper switch Q5 and the lower switch Q6 are 275.714 ns and 200 ns respectively, that is, the dead time is extended. The waveform of the magnetizing current Im can be referred to Figure 11 .
[0133] From Figure 11 it can be seen that the maximum value of the magnetizing current Im is 16.482 A, and the minimum value of Im is -30.485 A. Therefore, the DC bias current is (16.482 A - 30.485 A) / 2 = -7.002 A. Obviously, as the magnetizing current increases, the DC bias current in the third operating mode decreases, which again verifies that as the magnetizing current increases, the reverse current during the dead time can increase, thereby suppressing the DC bias.
[0134] Therefore, based on this idea, the method of the embodiments of this application is implemented. For example, the initial inductance value of the resonant inductor Lr is increased by a ratio of 1.5, and the initial capacitance value of the resonant capacitor Cr is decreased by a ratio of 1.5, so that the inductance value of the resonant inductor Lr becomes 87uH, and the capacitance value of the resonant capacitor Cr becomes 44nF, while other parameters remain unchanged. Correspondingly, the waveforms of the primary voltage and excitation current Im of the transformer Tr can be found in [reference needed]. Figure 12 .
[0135] from Figure 12 It can be seen that the maximum value of the excitation current is 22.63A, and the minimum value is 24.35A. The DC bias current is (22.63A-24.35A) / 2 = -7.002A. Obviously, compared with... Figure 11 compared to, Figure 12 The excitation current becomes larger, and the DC bias current becomes smaller. Additionally, from... Figure 12 It can also be seen that the peak of P2 becomes higher.
[0136] Therefore, the resonant parameter determination method in this application increases the inductance of the resonant inductor and the capacitance of the resonant capacitor while keeping the resonant frequency constant. This increases the excitation current and consequently the reverse current during the dead time. This reduces the DC bias of the bidirectional LLC resonant converter, suppresses transformer magnetization, and effectively improves the DC bias correction capability of the bidirectional LLC resonant converter. Furthermore, it reduces the risk of transformer over-saturation, ensuring the conversion efficiency and normal operation of the bidirectional LLC resonant converter.
[0137] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps may be performed in other orders or simultaneously.
[0138] Please see Figure 13 , Figure 13 A schematic diagram of a resonance parameter determination device 10 provided in an embodiment of this application is shown. This resonance parameter determination device 10 can be used to implement the above-described resonance parameter determination method.
[0139] like Figure 13 As shown, the resonance parameter determination device 10 may include an acquisition module 101, an adjustment module 102, a calculation module 103, and a determination module 104.
[0140] Specifically, the acquisition module 101 is used to acquire the first resonance parameters of the bidirectional LLC resonant converter at a preset operating frequency, wherein the resonance parameters include the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the bidirectional LLC resonant converter.
[0141] The adjustment module 102 is used to increase the inductance value of the resonant inductor and decrease the capacitance value of the resonant capacitor while keeping the operating frequency constant, so as to obtain the second resonant parameter.
[0142] The calculation module 103 is used to calculate the circuit gain of the bidirectional LLC resonant converter based on the second resonant parameters.
[0143] The determination module 104 is used to determine the selection reference parameters of the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameters.
[0144] It is understood that the division of the various modules in the above-described resonance parameter determination device 10 is only for illustrative purposes. In other embodiments, the resonance parameter determination device 10 can be divided into different modules as needed to complete all or part of the functions of the above-described resonance parameter determination device 10.
[0145] The specific implementations of each module in the embodiments of this application can also be referred to accordingly. Figures 2 to 5 The corresponding descriptions of the method embodiments shown are as follows. For example, the specific implementation of the acquisition module 101 can be referred to the description of step S1 above, the specific implementation of the adjustment module 102 can be referred to the description of step S2 above, the specific implementation of the calculation module 103 can be referred to the description of step S3 above, or the description of steps S3 and S6 above, and the specific implementation of the determination module 104 can be referred to the description of step S4 above, or the description of steps S4 and S5, S7 to S9 above, so they will not be described in detail here.
[0146] In the various embodiments of this application, all functional modules can be integrated into one processing module / unit, or each module can be a separate module, or two or more modules can be integrated into one module; the integrated module can be implemented in hardware or in the form of hardware plus software functional modules.
[0147] If the integrated modules described above in this application are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROM, RAM, magnetic disks, or optical disks.
[0148] Please see Figure 14This application also provides an electronic device 20.
[0149] Specifically, such as Figure 14 As shown, the electronic device 20 may include a processor 201 and a memory 202.
[0150] It is understood that processor 201 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. General-purpose processors can be microprocessors or any conventional processor.
[0151] The memory 202 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or it may be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital versatile optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory 202 may exist independently and be connected to the processor 201 via a bus. The memory 202 may also be integrated with the processor 201.
[0152] The memory 202 stores program instructions for executing the above-described method for determining resonance parameters, and its execution is controlled by the processor 201. The processor 201 executes the program instructions stored in the memory 202. The program instructions stored in the memory 202 are executable. Figures 2 to 5 The embodiments shown include some or all of the steps of the method for determining resonance parameters.
[0153] In some embodiments, the processor 201 can also be connected to the controller of the bidirectional LLC resonant converter. Specifically, the resonant inductor in the bidirectional LLC resonant converter can be an inductor with an adjustable inductance value, and the resonant capacitor can be a capacitor with an adjustable capacitance value. Both the resonant inductor and the resonant capacitor are controlled by the controller. In this way, the processor 201 can adjust the inductance value of the resonant inductor and the capacitance value of the resonant capacitor through the controller to adjust the resonant parameters to the final resonant parameters determined by the above-mentioned resonant parameter determination method, thereby reducing the DC bias of the bidirectional LLC resonant converter, suppressing transformer bias, and improving the conversion efficiency.
[0154] This application also provides a computer-readable storage medium for storing the resonance parameter determination method or algorithm provided in the above embodiments. The computer-readable storage medium may be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disk, removable disk, or any other form of storage medium in the art.
[0155] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for determining resonance parameters, applied to a bidirectional LLC resonant converter, used to determine the resonance parameters in the bidirectional LLC resonant converter, characterized in that, The method includes: Obtain the first resonance parameter of the bidirectional LLC resonant converter at a preset operating frequency, wherein the first resonance parameter includes the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the bidirectional LLC resonant converter. While keeping the operating frequency constant, the inductance value of the resonant inductor is increased while the capacitance value of the resonant capacitor is decreased to obtain the second resonant parameter; Calculate the circuit gain of the bidirectional LLC resonant converter based on the second resonance parameter; Based on the circuit gain and the second resonance parameter, the selection reference parameters for the bidirectional LLC resonant converter are determined.
2. The method for determining resonance parameters as described in claim 1, characterized in that, While keeping the operating frequency constant, during the process of increasing the inductance value of the resonant inductor and simultaneously decreasing the capacitance value of the resonant capacitor, the proportion by which the inductance value of the resonant inductor increases and the proportion by which the capacitance value of the resonant capacitor decreases are reciprocals of each other.
3. The method for determining resonance parameters as described in claim 2, characterized in that, The inductance value of the resonant inductor increases by a ratio between 1 and 2.
4. The method for determining resonance parameters as described in claim 2, characterized in that, The step of determining the selection reference parameters for the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameter includes: When the circuit gain is greater than the preset lower gain threshold, return to the step of increasing the inductance value of the resonant inductor and simultaneously decreasing the capacitance value of the resonant capacitor while keeping the operating frequency unchanged; When the circuit gain is equal to the preset lower gain threshold, the corresponding second resonance parameter is determined as the selection reference parameter; When the circuit gain is less than the preset lower gain threshold, the second resonance parameter of the previous adjustment is obtained, and the second resonance parameter of the previous adjustment is used as the selection reference parameter.
5. The method for determining resonance parameters as described in claim 4, characterized in that, The method further includes: The model numbers and corresponding selection parameters of the resonant inductor and the resonant capacitor are determined based on the selection reference parameters.
6. The method for determining resonance parameters as described in claim 5, characterized in that, After determining the models and corresponding selection parameters of the resonant inductor and the resonant capacitor, the method further includes: Calculate the circuit gain corresponding to the selected parameters; When the circuit gain is greater than or equal to the preset lower gain threshold, the selection parameter is determined as the final resonance parameter; When the circuit gain is less than the preset lower gain threshold, the second resonant parameter of the previous adjustment is determined as the selection reference parameter.
7. The method for determining resonance parameters as described in claim 1, characterized in that, The step of obtaining the first resonance parameter of the bidirectional LLC resonant converter at a preset operating frequency includes: The first resonance parameter is determined based on the preset quality factor, preset resonant frequency, maximum input voltage, and maximum output power of the bidirectional LLC resonant converter, such that the resonant frequency corresponding to the first resonance parameter is greater than or equal to the preset resonant frequency, and the circuit gain of the bidirectional LLC resonant converter is within a preset gain range.
8. A resonant parameter determining device, applied to a bidirectional LLC resonant converter, used to determine the resonant parameters in the bidirectional LLC resonant converter, characterized in that, The resonance parameter determination device includes: The acquisition module is used to acquire the first resonance parameter of the bidirectional LLC resonant converter at a preset operating frequency, wherein the first resonance parameter includes the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the bidirectional LLC resonant converter. An adjustment module is used to increase the inductance value of the resonant inductor and simultaneously decrease the capacitance value of the resonant capacitor while keeping the operating frequency constant, to obtain a second resonant parameter. The calculation module is used to calculate the circuit gain of the bidirectional LLC resonant converter based on the second resonant parameter; The determining module is used to determine the selection reference parameters of the bidirectional LLC resonant converter based on the circuit gain and the second resonant parameter.
9. An electronic device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the resonance parameter determination method as described in any one of claims 1 to 7.
10. A computer-readable storage medium, characterized in that, The device contains a computer program that is loaded by a processor to execute the resonance parameter determination method as described in any one of claims 1 to 7.