Current-sharing control method for two-way interleaving LLC (Logical Link Control) converter

Abstract

The invention relates to a current-sharing control method for a two-way interleaving LLC converter, and the method comprises the steps: obtaining a first resonant current effective value of a first resonant conversion circuit of the two-way interleaving LLC converter and a second resonant current effective value of a second resonant conversion circuit of the two-way interleaving LLC converter, calculating a resonance current difference value based on the first resonance current effective value and the second resonance current effective value; and when the resonance current difference value is greater than a current-sharing dead-zone adjustment intervention value and the output power is greater than a dead-zone adjustment power threshold value, performing current-sharing dead-zone time adjustment to obtain a dead-zone time adjustment result. According to the current-sharing control method for the two-way interleaving LLC converter, current-sharing dead-zone time adjustment is carried out based on the resonance current difference value and the output power, so that current-sharing adjustment can be accurately realized, and the reliability of the two-way interleaving LLC converter is ensured.

Description

Technical Field

[0001] The present invention relates to the field of current sharing control of resonant converters, and more specifically, to a current sharing control method for a dual-path interleaved parallel LLC converter. Background Art

[0002] Currently, the current sharing methods for interleaved parallel LLC resonant converters mainly include two types: passive current sharing method and active current sharing method. The passive current sharing method means that the LLC resonant converter does not need to add a current sharing control circuit or a current sharing algorithm, and only realizes the automatic current sharing method through the design of circuit topologies such as automatic balancing of capacitor voltages, magnetic element coupling, and series-parallel connection of resonant elements. The active current sharing method realizes current sharing control by sampling the transmission current of each resonant converter and using closed-loop control to adjust the voltage gain of each resonant converter to eliminate the current error of the parallel resonant converters.

[0003] The active current sharing method includes a method of realizing current sharing by adjusting the dead time of the LLC resonant converter. Although this method is simple and easy to implement without adding additional auxiliary circuits or devices, it cannot accurately achieve current sharing adjustment and has poor reliability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a current sharing control method for a dual-path interleaved parallel LLC converter, which can accurately achieve current sharing adjustment, thereby ensuring the reliability of the dual-path interleaved parallel LLC converter, aiming at the above-mentioned defects of the prior art.

[0005] The technical solution adopted by the present invention to solve its technical problems is to construct a current sharing control method for a dual-path interleaved parallel LLC converter, including: Obtaining the effective value of the first resonant current of the first resonant conversion circuit and the effective value of the second resonant current of the second resonant conversion circuit of the dual-path interleaved parallel LLC converter, and calculating the resonant current difference based on the effective value of the first resonant current and the effective value of the second resonant current; When the resonant current difference is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, performing current sharing dead time adjustment to obtain the dead time adjustment result.

[0006] In the current-sharing control method of the dual-channel interleaved parallel LLC converter according to the present invention, when the difference between the resonant currents is greater than the intervention value for current-sharing dead-time adjustment and the output power is greater than the dead-time adjustment power threshold, performing current-sharing dead-time adjustment to obtain the dead-time adjustment result includes: obtaining the upper limit of the current-sharing dead-time based on the characteristics of the dual-channel interleaved parallel LLC converter; when the difference between the resonant currents is greater than the intervention value for current-sharing dead-time adjustment and the output power is greater than the dead-time adjustment power threshold, closed-loop adjusting the current-sharing dead-time of the first resonant conversion circuit and the second resonant conversion circuit based on the difference between the resonant currents until the difference between the resonant currents is less than or equal to the intervention value for current-sharing dead-time adjustment or the current-sharing dead-time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current-sharing dead-time.

[0007] In the current-sharing control method of the dual-channel interleaved parallel LLC converter according to the present invention, the closed-loop adjusting the current-sharing dead-time of the first resonant conversion circuit and the second resonant conversion circuit based on the difference between the resonant currents until the difference between the resonant currents is less than or equal to the intervention value for current-sharing dead-time adjustment or the current-sharing dead-time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current-sharing dead-time includes: when the effective value of the first resonant current is greater than the effective value of the second resonant current, closed-loop adjusting the current-sharing dead-time of the second resonant conversion circuit to 0, then adjusting the current-sharing dead-time of the first resonant conversion circuit to the upper limit of the current-sharing dead-time, and then controlling the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current-sharing dead-time; when the effective value of the second resonant current is greater than the effective value of the first resonant current, closed-loop adjusting the current-sharing dead-time of the first resonant conversion circuit to 0, then adjusting the current-sharing dead-time of the second resonant conversion circuit to the upper limit of the current-sharing dead-time, and then controlling the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current-sharing dead-time.

[0008] In the current-sharing control method of the dual-channel interleaved parallel LLC converter according to the present invention, it further includes: performing derating adjustment based on the difference between the resonant currents, the output power, the dead-time adjustment result, and the derating time threshold.

[0009] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the derating adjustment based on the resonant current difference, the output power, the dead-time adjustment result, and the derating time threshold includes: when the current-sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current-sharing dead time, the resonant current difference is greater than the intervention value for current-sharing derating adjustment, and the output power is greater than the derating adjustment power threshold, and all of these conditions continuously reach the derating time threshold, calculate the derated output power based on the output power, the effective value of the first resonant current, the effective value of the second resonant current, the resonant current difference, and the intervention value for current-sharing derating adjustment; control the dual-path interleaved parallel LLC converter to output according to the derated output power; repeat the foregoing steps until the resonant current difference is less than the intervention value for derating adjustment or the output power is less than or equal to the derating adjustment power threshold.

[0010] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the derated output power is calculated based on the following formula: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)|-△Ib)*X; where Po(n) represents the output power, Pomax(n + 1) represents the derated output power, △Ib represents the intervention value for current-sharing derating adjustment, IL1(n) represents the effective value of the first resonant current, IL2(n) represents the effective value of the second resonant current, X represents the derating speed, and n represents the current sampling time.

[0011] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the derating adjustment based on the resonant current difference, the output power, the dead-time adjustment result, and the derating time threshold further includes: maintaining the current output power when the output power is less than or equal to the derating protection power threshold and when the resonant current difference is less than the intervention value for current-sharing derating adjustment; outputting at the minimum power when the output power is less than the first current-sharing derating power threshold, and no longer derating.

[0012] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the current-sharing derating adjustment intervention values include a first current-sharing derating adjustment intervention value, a second current-sharing derating adjustment intervention value, and a third current-sharing derating adjustment intervention value; the derating adjustment power thresholds include a first derating adjustment power threshold, a second derating adjustment power threshold, a third derating adjustment power threshold, and a fourth derating adjustment power threshold; the resonant current difference being greater than the current-sharing derating adjustment intervention value and the output power being greater than the derating adjustment power threshold includes: the resonant current difference being greater than the first current-sharing derating adjustment intervention value and the output power being greater than the first derating adjustment power threshold and less than or equal to the second derating adjustment power threshold; or the resonant current difference being greater than the second current-sharing derating adjustment intervention value and the output power being greater than the second derating adjustment power threshold and less than or equal to the third derating adjustment power threshold; or the resonant current difference being greater than the third current-sharing derating adjustment intervention value and the output power being greater than the third derating adjustment power threshold and less than or equal to the fourth derating adjustment power threshold; the first current-sharing derating adjustment intervention value, the second current-sharing derating adjustment intervention value, and the third current-sharing derating adjustment intervention value decrease in sequence; the first derating adjustment power threshold, the second derating adjustment power threshold, the third derating adjustment power threshold, and the fourth derating adjustment power threshold increase in sequence.

[0013] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, it further includes performing current-sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold.

[0014] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the performing current-sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold includes: when the resonant current difference is greater than the current-sharing protection adjustment intervention value and the output power is less than the derating protection power threshold and lasts for the protection time threshold, controlling the dual-path interleaved parallel LLC converter to shut down.

[0015] In the current-sharing control method of the dual-path interleaved parallel LLC converter according to the present invention, the performing current-sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold further includes: when the derating adjustment result is not received, performing current-sharing protection adjustment only based on the resonant current difference, the output power, and the protection time threshold.

[0016] In the current sharing control method of the dual - path interleaved parallel LLC converter according to the present invention, the current sharing protection adjustment intervention values include a first current sharing protection adjustment intervention value, a second current sharing protection adjustment intervention value, a third current sharing protection adjustment intervention value, and a fourth current sharing protection adjustment intervention value; the derating protection power thresholds include a first derating protection power threshold, a second derating protection power threshold, a third derating protection power threshold, and a fourth derating protection power threshold; the resonant current difference is greater than the current sharing protection adjustment intervention value and the output power is less than the derating protection power threshold, including: the resonant current difference is greater than the first current sharing protection adjustment intervention value and the output power is less than or equal to the first derating protection power threshold; the resonant current difference is greater than the second current sharing protection adjustment intervention value and the output power is greater than the first derating protection power threshold and less than or equal to the second derating protection power threshold; the resonant current difference is greater than the third current sharing protection adjustment intervention value and the output power is greater than the second derating protection power threshold and less than or equal to the third derating protection power threshold; the resonant current difference is greater than the fourth current sharing protection adjustment intervention value and the output power is greater than the third derating protection power threshold and less than or equal to the fourth derating protection power threshold; the first current sharing protection adjustment intervention value, the second current sharing protection adjustment intervention value, the third current sharing protection adjustment intervention value, and the fourth current sharing protection adjustment intervention value decrease in sequence; the first derating protection power threshold, the second derating protection power threshold, the third derating protection power threshold, and the fourth derating protection power threshold increase in sequence.

[0017] Implementing the current sharing control method of the dual - path interleaved parallel LLC converter according to the present invention can accurately achieve current sharing adjustment by adjusting the current sharing dead - time based on the resonant current difference and the output power, thereby ensuring the reliability of the dual - path interleaved parallel LLC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings: Figure 1 is a flowchart of the current sharing control method of the dual - path interleaved parallel LLC converter according to the present invention; Figure 2 is a control logic block diagram of the two - path interleaved parallel LLC resonant converter according to the present invention; Figure 3 is a circuit schematic diagram of the two - path interleaved parallel LLC resonant converter according to the present invention; Figure 4 is a flowchart of a preferred embodiment of the current sharing control method of the dual - path interleaved parallel LLC converter according to the present invention; Figure 5 is a curve diagram of a preferred embodiment of the upper limit Tjmax setting value of the current sharing dead - time according to the present invention; Figure 6 is the flowchart of the current sharing dead time adjustment step of the preferred embodiment of the present invention; Figure 7 is the flowchart of the derating adjustment step of the preferred embodiment of the present invention; Figure 8 is the flowchart of the current sharing protection adjustment step of the preferred embodiment of the present invention; Figures 9A - 9B is the waveform diagram of the primary side current of the two-way resonant conversion circuit before and after adding the current sharing dead time adjustment in the embodiment of the present invention; Figures 10A - 10B is the waveform diagram of the primary side drive of the two-way resonant conversion circuit before and after adding the current sharing dead time adjustment in the embodiment of the present invention; Figures 11A - 11B is the waveform diagram of the primary side current of the two-way resonant conversion circuit before and after adding the derating adjustment in the embodiment of the present invention; Figure 12 is the waveform diagram of the primary side current of the two-way resonant conversion circuit before adding the current sharing protection adjustment in the embodiment of the present invention; Figure 13 is the parameter step table for implementing the current sharing control method of the dual-channel interleaved LLC converter of the present invention with a 40KW interleaved two-way LLC resonant converter as an example; Figure 14 is the test result of the current sharing dead time Tj under different loads for meeting derating - the measured result value of Tjmax. Detailed implementation manners

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0020] Figure 1 is the flowchart of the current sharing control method of the dual-channel interleaved LLC converter of the present invention. As Figure 1 shown, in step S1, the effective value of the first resonant current of the first resonant conversion circuit and the effective value of the second resonant current of the second resonant conversion circuit of the dual-channel interleaved LLC converter are obtained, and the resonant current difference is calculated based on the effective value of the first resonant current and the effective value of the second resonant current.

[0021] In step S2, when the resonant current difference is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, the current sharing dead time is adjusted to obtain the dead time adjustment result.

[0022] In a further preferred embodiment of the present invention, when the difference between the resonant currents is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, performing the current sharing dead time adjustment to obtain the dead time adjustment result includes: obtaining an upper limit of the current sharing dead time based on the characteristics of the dual-path interleaved LLC converter; when the difference between the resonant currents is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, closed-loop adjusting the current sharing dead time of the first resonant conversion circuit and the second resonant conversion circuit based on the difference between the resonant currents until the difference between the resonant currents is less than or equal to the current sharing dead time adjustment intervention value or the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time.

[0023] In a further preferred embodiment of the present invention, the closed-loop adjusting the current sharing dead time of the first resonant conversion circuit and the second resonant conversion circuit based on the difference between the resonant currents until the difference between the resonant currents is less than or equal to the current sharing dead time adjustment intervention value or the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time includes: when the effective value of the first resonant current is greater than the effective value of the second resonant current, closed-loop adjusting the current sharing dead time of the second resonant conversion circuit to 0, then adjusting the current sharing dead time of the first resonant conversion circuit to the upper limit of the current sharing dead time, and then controlling the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current sharing dead time; when the effective value of the second resonant current is greater than the effective value of the first resonant current, closed-loop adjusting the current sharing dead time of the first resonant conversion circuit to 0, then adjusting the current sharing dead time of the second resonant conversion circuit to the upper limit of the current sharing dead time, and then controlling the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current sharing dead time.

[0024] Implementing the current sharing control method of the dual-path interleaved LLC converter of the present invention can accurately achieve current sharing adjustment by adjusting the current sharing dead time based on the difference between the resonant currents and the output power, thereby ensuring the reliability of the dual-path interleaved LLC converter.

[0025] In a further preferred embodiment of the present invention, the current sharing control method of the dual-path interleaved parallel LLC converter further includes derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold. In a preferred embodiment of the present invention, the derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold includes: when the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the resonant current difference is greater than the current sharing derating adjustment intervention value, and the output power is greater than the derating adjustment power threshold, and all continue to reach the derating time threshold, calculate the derated output power based on the output power, the effective value of the first resonant current, the effective value of the second resonant current, the resonant current difference, and the current sharing derating adjustment intervention value; control the dual-path interleaved parallel LLC converter to output according to the derated output power; repeat the foregoing steps until the resonant current difference is less than the derating adjustment intervention value or the output power is less than or equal to the derating adjustment power threshold.

[0026] Preferably, the derated output power is calculated based on the following formula: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)|-△Ib)*X; where Po(n) represents the output power, Pomax(n + 1) represents the derated output power, △Ib represents the current sharing derating adjustment intervention value, IL1(n) represents the effective value of the first resonant current, IL2(n) represents the effective value of the second resonant current, X represents the derating speed, and n represents the current sampling time.

[0027] In a preferred embodiment of the present invention, the derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold further includes: maintaining the current output power when the output power is less than or equal to the derating protection power threshold and when the resonant current difference is less than the current sharing derating adjustment intervention value; outputting at the minimum power when the output power is less than the first current sharing derating power threshold, and no longer derating.

[0028] In a preferred embodiment of the present invention, the current sharing derating adjustment intervention values include a first current sharing derating adjustment intervention value, a second current sharing derating adjustment intervention value, and a third current sharing derating adjustment intervention value; the derating adjustment power thresholds include a first derating adjustment power threshold, a second derating adjustment power threshold, a third derating adjustment power threshold, and a fourth derating adjustment power threshold. The resonant current difference being greater than the current sharing derating adjustment intervention value and the output power being greater than the derating adjustment power threshold includes: the resonant current difference being greater than the first current sharing derating adjustment intervention value and the output power being greater than the first derating adjustment power threshold and less than or equal to the second derating adjustment power threshold; or the resonant current difference being greater than the second current sharing derating adjustment intervention value and the output power being greater than the second derating adjustment power threshold and less than or equal to the third derating adjustment power threshold; or the resonant current difference being greater than the third current sharing derating adjustment intervention value and the output power being greater than the third derating adjustment power threshold and less than or equal to the fourth derating adjustment power threshold; the first current sharing derating adjustment intervention value, the second current sharing derating adjustment intervention value, and the third current sharing derating adjustment intervention value decrease in sequence; the first derating adjustment power threshold, the second derating adjustment power threshold, the third derating adjustment power threshold, and the fourth derating adjustment power threshold increase in sequence.

[0029] Implementing the current sharing control method of the dual-channel interleaved parallel LLC converter of the present invention, by adjusting the dead time for current sharing based on the resonant current difference and the output power, current or power balance can be achieved. At the same time, by performing derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold, the adaptability to the inconsistency of the two-channel resonant parameters of the dual-channel interleaved parallel LLC resonant converter can be improved, enabling it to adapt to the inconsistency of the two-channel LLC resonant parameters to the greatest extent while still being able to reliably output the maximum power.

[0030] In a further preferred embodiment of the present invention, the current sharing control method of the dual-channel interleaved parallel LLC converter of the present invention further includes performing current sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold. In a preferred embodiment of the present invention, the performing current sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold includes: when the resonant current difference is greater than the current sharing protection adjustment intervention value and the output power is less than the derating protection power threshold and lasts for the protection time threshold, controlling the dual-channel interleaved parallel LLC converter to shut down.

[0031] Preferably, the current sharing protection adjustment intervention values include a first current sharing protection adjustment intervention value, a second current sharing protection adjustment intervention value, a third current sharing protection adjustment intervention value, and a fourth current sharing protection adjustment intervention value; the derating protection power thresholds include a first derating protection power threshold, a second derating protection power threshold, a third derating protection power threshold, and a fourth derating protection power threshold; the resonant current difference being greater than the current sharing protection adjustment intervention value and the output power being less than the derating protection power threshold includes: the resonant current difference being greater than the first current sharing protection adjustment intervention value and the output power being less than or equal to the first derating protection power threshold; the resonant current difference being greater than the second current sharing protection adjustment intervention value and the output power being greater than the first derating protection power threshold and less than or equal to the second derating protection power threshold; the resonant current difference being greater than the third current sharing protection adjustment intervention value and the output power being greater than the second derating protection power threshold and less than or equal to the third derating protection power threshold; the resonant current difference being greater than the fourth current sharing protection adjustment intervention value and the output power being greater than the third derating protection power threshold and less than or equal to the fourth derating protection power threshold; the first current sharing protection adjustment intervention value, the second current sharing protection adjustment intervention value, the third current sharing protection adjustment intervention value, and the fourth current sharing protection adjustment intervention value decrease in sequence; the first derating protection power threshold, the second derating protection power threshold, the third derating protection power threshold, and the fourth derating protection power threshold increase in sequence.

[0032] Implementing the current sharing control method of the dual-channel interleaved parallel LLC converter of the present invention can achieve current or power balance by adjusting the current sharing dead time based on the resonant current difference and the output power. At the same time, by performing derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold, the adaptability to the inconsistency of the two-channel resonant parameters of the dual-channel interleaved parallel LLC resonant converter can be improved, enabling it to adapt to the inconsistency of the two-channel LLC resonant parameters to the greatest extent while still reliably outputting the maximum power. By performing current sharing protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold, damage to the dual-channel interleaved parallel LLC converter can be prevented. Further, the current sharing control method of the dual-channel interleaved parallel LLC converter of the present invention ensures the stability and reliability of the dual-channel interleaved parallel LLC converter by restricting the upper limit of the current sharing dead time adjustment (i.e., setting the current sharing dead time upper limit). Finally, by formulating appropriate derating and protection strategies, the adaptability of the product to the inconsistency of the two-channel resonant parameters of the dual-channel interleaved parallel LLC resonant converter is improved, enabling the product to adapt to the inconsistency of the two-channel LLC resonant parameters to the greatest extent while still reliably outputting the maximum power.

[0033] Figure 2It is the control logic block diagram of the two-channel interleaved parallel LLC resonant converter of the present invention. The current sharing control method of the dual-channel interleaved parallel LLC converter of the present invention is preferably applicable to Figure 2 The two-channel interleaved parallel LLC resonant converter. As Figure 2 shown, the two-channel interleaved parallel LLC resonant converter is an LLC full-bridge resonant converter or an LLC half-bridge resonant converter, and includes a full-bridge or half-bridge switch circuit, an LLC resonant circuit, a high-frequency transformer, and an output rectifying and filtering circuit. The dual-channel interleaved parallel LLC converter includes a first resonant conversion circuit and a second resonant conversion circuit. The inputs and outputs of the two resonant conversion circuits are connected in parallel, that is, the inputs of each LLC resonant conversion circuit share the DC input voltage, and the output terminals of the rectifying and filtering circuits of each channel are connected in parallel to jointly provide the output voltage for the load. The parallel output voltage and output current are sampled by the output voltage and output current sampling circuit and then sent to the control circuit, and are converted into corresponding digital quantities through A / D. The microcontroller (MCU), which can be a DSP, a single-chip microcomputer, an ARM embedded processor, or an FPGA programmable chip, performs closed-loop control according to this digital quantity. The resonant currents of the two LLC resonant conversion circuits are sampled by the resonant current sampling circuit and then sent to the control circuit, and are converted into corresponding digital quantities through A / D. The microcontroller performs current sharing closed-loop control according to this digital quantity. The microcontroller outputs multiple PWM signals, and every two PWM signals (complementary) form a set of positive and negative drive signals. The positive and negative drive signals drive the isolation transformer through the drive IC to obtain a set of isolated upper and lower transistor drives, and drive the silicon carbide switch tubes of the half-bridge or full-bridge to work.

[0034] Referring to Figure 1 it can be seen that the current sharing control method of the dual-channel interleaved parallel LLC converter mainly includes current sharing dead time adjustment (hereinafter referred to as current sharing dead time adjustment) based on the difference in resonant current and output power of the dual-channel interleaved parallel LLC converter, derating adjustment (hereinafter referred to as derating adjustment) based on the difference in resonant current, the output power, the result of dead time adjustment, and the derating time threshold, and current sharing protection adjustment (hereinafter referred to as current sharing protection adjustment) based on the difference in resonant current, the output power, the result of derating adjustment, and the protection time threshold.

[0035] Among them, the adjustment of the current-sharing dead time includes current-sharing adjustment control, upper limit test and determination of the current-sharing dead time. In the current-sharing adjustment control, the operating frequencies of the two interleaved LLC resonant converters are the same, and the phase difference is π / 2, forming an interleaved parallel structure. By detecting the resonant cavity current values of the two LLC resonant converters, the dead time of the resonant converter is closed-loop adjusted to achieve current sharing between the two LLC resonant converters, so that the transmitted currents and powers of the two resonant converter circuits are balanced. As is well known, the dead time of the LLC resonant converter cannot be too large (if the dead time is too large, the resonant current will reverse and then turn on, and ZVS cannot be achieved and hard switching is relatively serious). Therefore, after increasing the current-sharing dead time, we need to limit the upper limit of the current-sharing dead time to ensure the reliability and stability of the LLC resonant converter. And this upper limit of the current-sharing dead time needs to be formulated according to the actual test data according to the test current-sharing requirements and test derating requirements.

[0036] Derating adjustment is because when the current-sharing dead time is adjusted to the upper limit value (the current-sharing ability is adjusted to the allowable limit) and still cannot meet the current-sharing performance requirements, the difference between the two resonant currents will become larger and larger as the deviation degree of the resonant parameters increases. When it reaches a certain level and triggers the derating intervention condition, derating starts to ensure the working reliability of the resonant converter and prevent the converter from overheating and damage.

[0037] Current-sharing protection adjustment is because when the deviation of the two LLC resonant parameters is particularly serious or one of them is damaged, sudden load application will first trigger derating. Because the derating time adjustment period is shorter, after derating to a certain extent or to the power lower limit, the difference between the two resonant currents is still very large. After a period of time, it triggers current-sharing protection shutdown to avoid overheating and damage of one of the two resonant protectors with too large a load for a long time.

[0038] Figure 4 It is a flowchart of a preferred embodiment of the current-sharing control method for the dual interleaved LLC converter of the present invention. As Figure 4 shown, in step 1, first obtain the effective value of the first resonant current of the first resonant conversion circuit of the dual interleaved LLC converter and the effective value of the second resonant current of the second resonant conversion circuit, and calculate the difference between the resonant currents based on the effective value of the first resonant current and the effective value of the second resonant current. For example, the microcontroller outputs a driving signal to drive the switching tubes of the two LLC resonant conversion circuits to work. In each switching cycle, the resonant currents of the two resonant converter circuits are detected, and after filtering, the effective values of the resonant currents of the two resonant converter circuits are obtained. Define the effective value of the first resonant current as IL1, the effective value of the second resonant current IL2, and the absolute value of the resonant current difference △I = |IL1 - IL2|.

[0039] Then, step 2 is executed to judge the intervention condition for regulating the current-sharing dead time. When the difference between the resonant currents is greater than the intervention value for regulating the current-sharing dead time and the output power is greater than the dead-time regulation power threshold, the current-sharing dead time is regulated to obtain the dead-time regulation result. For example, when the output power is greater than Pomax / 4 (the power of Pomax / 4 is small, and there is no thermal risk even without current sharing) and the absolute value of the difference between the two-way LLC resonant currents is greater than the intervention value for regulating the current-sharing dead time (defined as △Ia), the current-sharing dead-time regulation action is triggered, that is, Po>Pomax / 4 and △I>△Ia trigger the current-sharing dead-time regulation.

[0040] Then, step 3 is executed to obtain the upper limit of the current-sharing dead time based on the characteristics of the dual-channel interleaved parallel LLC converter. Here, it should be clear that each LLC resonant conversion circuit has an original basic dead time (referred to as the basic dead time Tb here) that changes according to the operating frequency and load size. Now, a current-sharing dead time (referred to as the current-sharing dead time Tj here) is added to regulate the current sharing. Then, the total dead time (referred to as Ts here) is equal to the basic dead time plus the current-sharing dead time, that is, Ts = Tb + Tj. The basic dead time Tb is formulated according to the characteristics of the switching tube and the ZVS operating characteristics of the LLC resonant converter, and its magnitude and range remain unchanged. The current-sharing dead-time regulation is only to superimpose the current-sharing dead time on the basis of the basic dead time Tb. As is well known, the dead time of the LLC resonant converter cannot be too large (if the dead time is too large, the resonant current will reverse and then turn on, and ZVS cannot be achieved and the hard switching is relatively serious). Therefore, after adding the current-sharing dead time Tj, we need to limit the upper limit of the current-sharing dead time (defined as Tjmax) to ensure the reliability and stability of the operation of the LLC resonant converter, especially when it is heavily loaded. At this time, the resonant current is the largest, the hard-switching loss is the largest, and the thermal influence is the most serious. Therefore, the larger the load, the greater the limitation on Tjmax should be, so as to ensure the thermal reliability of the product. As described above, theoretically, Tjmax is a curve that becomes smaller as the load increases. The larger the load, the smaller Tjmax. The formulation of this curve needs to be tested and determined according to the actual working conditions. On the premise that the thermal stress, voltage stress of the switching tube and the thermal stress of the magnetic device meet the test derating, a larger Tjmax should be taken as much as possible to achieve better current-sharing performance. Figure 5 is a curve graph of the preferred embodiment of the set value of the upper limit Tjmax of the current-sharing dead time of the present invention. Figure 14 Shows the test results of the current-sharing dead time Tj that meets the derating under different loads - the measured result value of Tjmax. Among them Figure 5 The Tjmax curve of Figure 14 is obtained by fitting the measured result value of -Tjmax shown in

[0041] Then, step 4 is executed, that is, the specific current sharing dead time adjustment process is as follows. After triggering the current sharing dead time adjustment, the difference in resonant current (preferably the absolute value) ΔI of the two-way resonant current is sent to the microcontroller, and the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit is adjusted through digital PID control in a closed loop to reach the upper limit of the current sharing dead time.

[0042] The specific adjustment method is as follows: when IL1 > IL2 + ΔIa (here, the current sharing dead time of the first resonant conversion circuit is defined as Tj1, and the current sharing dead time of the second resonant conversion circuit is defined as Tj2. Tj1 and Tj2 cannot have numerical values at the same time, and at least one of them must be 0), first reduce Tj2. After Tj2 is reduced to 0, then increase Tj1 (if Tj2 is already 0, then directly adjust Tj1); when IL2 > IL1 + ΔIa, first reduce Tj1. After Tj1 is reduced to 0, then increase Tj2 (if Tj1 is already 0, then directly adjust Tj2)); the microprocessor outputs complementary switch signals to perform closed-loop control on the two-way resonant converter circuit, so that the absolute value of the difference in resonant current ΔI becomes smaller.

[0043] After the difference in resonant current ΔI becomes smaller, repeat steps 1 and 4 until ΔI is less than the required threshold (≤ΔIa). After achieving current sharing between the two-way resonant converter circuits, keep Tj1 and Tj2 unchanged and no longer adjust the current sharing dead time. If one of the current sharing dead times Tj1 or Tj2 is adjusted to Tjmax, the resonant converter operates according to the adjusted limit Tjmax (one of Tj1 and Tj2 is 0, and the other is Tjmax), and no longer adjusts the current sharing dead time.

[0044] Step 6, when the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the difference in resonant current is greater than the intervention value of current sharing derating adjustment, and the output power is greater than the derating adjustment power threshold, and all of them continuously reach the derating time threshold, calculate the derated output power based on the output power, the effective value of the first resonant current, the effective value of the second resonant current, the difference in resonant current, and the intervention value of current sharing derating adjustment. Here, those skilled in the art can understand that when the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the difference in resonant current is greater than the intervention value of current sharing derating adjustment, and the output power is greater than the derating adjustment power threshold, and all of them continuously reach the derating time threshold, it means that the duration for the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit to reach the upper limit of the current sharing dead time, the duration for the difference in resonant current to be greater than the intervention value of current sharing derating adjustment, and the duration for the output power to be greater than the derating adjustment power threshold all reach the derating time threshold.

[0045] That is, when the deviation of the resonance parameters of the two paths is small, the current sharing dead-time regulation can control the difference between the LLC resonance currents of the two paths within △Ia for stable operation. However, when the deviation of the resonance parameters of the two paths is large, after the current sharing dead-time is adjusted to Tjmax (the current sharing regulation reaches the limit), the current sharing performance requirements are still not met, and the difference between the resonance currents of the two paths will increase with the increase of the deviation degree of the resonance parameters. When the difference △I between the resonance currents is greater than the intervention value of the current sharing derating regulation (defined as △Ib), the current sharing derating is triggered. For example, when the output power Po>Pomax / 4 and the difference △I between the resonance currents>△Ib lasts for 5 seconds, the derating starts. Here, the intervention value of the current sharing derating regulation may include a first intervention value of the current sharing derating regulation, a second intervention value of the current sharing derating regulation, and a third intervention value of the current sharing derating regulation; the derating regulation power thresholds include a first derating regulation power threshold, a second derating regulation power threshold, a third derating regulation power threshold, and a fourth derating regulation power threshold. That is, when the difference between the resonance currents is greater than the intervention value of the current sharing derating regulation and the output power is greater than the derating regulation power threshold, it includes: the difference between the resonance currents is greater than the first intervention value of the current sharing derating regulation and the output power is greater than the first derating regulation power threshold and less than or equal to the second derating regulation power threshold; or the difference between the resonance currents is greater than the second intervention value of the current sharing derating regulation and the output power is greater than the second derating regulation power threshold and less than or equal to the third derating regulation power threshold; or the difference between the resonance currents is greater than the third intervention value of the current sharing derating regulation and the output power is greater than the third derating regulation power threshold and less than or equal to the fourth derating regulation power threshold; the first intervention value of the current sharing derating regulation, the second intervention value of the current sharing derating regulation, and the third intervention value of the current sharing derating regulation decrease in sequence; the first derating regulation power threshold, the second derating regulation power threshold, the third derating regulation power threshold, and the fourth derating regulation power threshold increase in sequence.

[0046] Step 7: Execute the current sharing derating regulation process. The microcontroller can calculate the current output power Po(n) through the output voltage and current sampling, and can also obtain the current resonance currents IL1(n) and IL2(n) of the two paths through the resonance current sampling circuit, and then calculate the current output power Po(n). When executing the current sharing derating regulation, the following formula can be used to calculate the derated output power according to different output power levels: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)|-△Ib)*X; ​Where Po(n) represents the output power, Pomax(n + 1) represents the output power after derating, △Ib represents the intervention value of current sharing derating adjustment, which is one of the triggering derating conditions, IL1(n) represents the effective value of the first resonant current, IL2(n) represents the effective value of the second resonant current, X represents the derating speed, and its unit is KW / A, that is, for every 1A exceeding the intervention value of current sharing derating adjustment, the derating is X KW, that is, the derating is performed based on the current output power. n represents the current sampling time. After the derating calculation, the output power after derating, that is, the maximum power after derating Pomax(n + 1), is sent to the microcontroller, and the microcontroller controls the output power through digital PID control closed-loop regulation to reduce the output power to Pomax(n + 1). Preferably, when Pomax(n + 1) ≤ Pomax / 4, take Pomax(n + 1) = Pomax / 4 (the derating lower limit Pomax / 4).

[0047] Step 8: Execute current sharing derating stabilization, and then continue with a new round of derating strategy determination after derating. If the derating intervention condition is triggered again after derating, repeat the actions in Step 6 and Step 7 until |△I| < △Ib or Po < Pomax / 4, and stop derating.

[0048] Step 9: Execute current sharing protection intervention, that is, when the difference between the resonant currents is greater than the intervention value of current sharing protection adjustment and the output power is less than the derating protection power threshold and lasts for the protection time threshold, control the dual-path interleaved LLC converter to shut down. If the resonant parameters of the two LLCs deviate severely or one of them is damaged, and when a sudden heavy load is applied, the absolute value |△I| of the difference between the resonant currents will be very large, and the resonant converter cannot withstand it for a long time, otherwise it will be relatively dangerous. Moreover, the adjustment speed of derating cannot reduce the difference |△I| of the resonant currents to a relatively small value through one derating. After one derating, the difference |△I| of the resonant currents is still relatively large. Therefore, an intervention value of current sharing protection (defined as △Ic) is introduced on the basis of current sharing derating, and △Ic > △Ib, leaving a certain judgment value space and time difference. When |△I| > △Ic lasts for 10S, the resonant converter shuts down for current sharing protection to prevent the resonant converter with a high resonant current from overheating and being damaged or exploding. In a further preferred embodiment of the present invention, when the derating adjustment result is not received, current sharing protection adjustment is performed only based on the difference between the resonant currents, the output power, and the protection time threshold. For example, when the derating adjustment result is invalid or not received due to signal transmission, current sharing protection adjustment can be directly performed only based on the difference between the resonant currents, the output power, and the protection time threshold.

[0049] In a preferred embodiment of the present invention, the current sharing protection adjustment intervention values include a first current sharing protection adjustment intervention value, a second current sharing protection adjustment intervention value, a third current sharing protection adjustment intervention value, and a fourth current sharing protection adjustment intervention value; the derating protection power thresholds include a first derating protection power threshold, a second derating protection power threshold, a third derating protection power threshold, and a fourth derating protection power threshold; the resonant current difference being greater than the current sharing protection adjustment intervention value and the output power being less than the derating protection power threshold includes: the resonant current difference being greater than the first current sharing protection adjustment intervention value and the output power being less than or equal to the first derating protection power threshold; the resonant current difference being greater than the second current sharing protection adjustment intervention value and the output power being greater than the first derating protection power threshold and less than or equal to the second derating protection power threshold; the resonant current difference being greater than the third current sharing protection adjustment intervention value and the output power being greater than the second derating protection power threshold and less than or equal to the third derating protection power threshold; the resonant current difference being greater than the fourth current sharing protection adjustment intervention value and the output power being greater than the third derating protection power threshold and less than or equal to the fourth derating protection power threshold; the first current sharing protection adjustment intervention value, the second current sharing protection adjustment intervention value, the third current sharing protection adjustment intervention value, and the fourth current sharing protection adjustment intervention value decrease in sequence; the first derating protection power threshold, the second derating protection power threshold, the third derating protection power threshold, and the fourth derating protection power threshold increase in sequence.

[0050] Figure 3 is the circuit schematic diagram of the two-way interleaved parallel LLC resonant converter of the present invention. The following is combined with Figure 3The preferred embodiments of the current sharing control method for the dual-path interleaved parallel LLC converter of the present invention are further described as follows. The dual-path interleaved parallel LLC converter is a two-path interleaved parallel full-bridge LLC resonant converter, including: a full-bridge switching circuit composed of Q1~Q4, a first resonant conversion circuit composed of a resonant inductor Lr1, a resonant capacitor Cr1 and the primary winding of T1, and an output rectifying and filtering circuit composed of D1~D8 and C5; a full-bridge switching circuit composed of Q5~Q8, a second resonant conversion circuit composed of a resonant inductor Lr2, a resonant capacitor Cr2 and the primary winding of T2, and an output rectifying and filtering circuit composed of D9~D16 and C3~C4. The two-path interleaved parallel full-bridge LLC resonant converters form a parallel input and parallel output structure, with the inputs paralleled at both ends of the series connection of input capacitors C1 and C2, and the outputs paralleled at both ends of the series connection of output capacitors C3 and C4. The microcontroller used is a DSP (TMS320F28062PZPS). The microcontroller outputs 8 PWM signals. Every two PWM signals form a group of complementary signals, and after being driven by a driving IC to drive an isolation transformer, a group of positive and negative voltage driving signals isolated by the transformer are obtained. Every 4 PWM signals form two groups of complementary full-bridge positive and negative voltage driving signals, and 8 PWM signals form two-path full-bridge LLC positive and negative voltage driving signals. The frequencies of the two-path full-bridge LLC driving signals are the same and are staggered by 90°, forming an interleaved parallel structure. Each group of positive and negative voltage driving signals passes through an isolation transformer for isolation. The output voltage sampling circuit samples the paralleled output voltage, and the output current sampling circuit samples the paralleled output current. The sampled values of the output voltage and output current are sent into the A / D converter of the DSP to be converted into digital quantities for the system to perform closed-loop control to output a stable voltage. There are two paths in the resonant current sampling circuit, which respectively sample the resonant currents of the two-path LLC resonant conversion circuits, and are converted into digital quantities through the A / D converter of the DSP for the system to use for current sharing control.

[0051] The rated input voltage of the two-path interleaved parallel LLC resonant conversion circuits is 860V, the rated output voltage is 500V, the rated output power is 40KW, and the resonant frequency is 105KHZ. The initial value of the resonant inductor of the first resonant conversion circuit is Lr1 = 26uH, and the initial value of the resonant capacitor is Cr1 = 77nF; the initial value of the resonant inductor of the second resonant conversion circuit is Lr2 = 26uH, and the initial value of the resonant capacitor is Cr2 = 77nF. The intervention value △Ia of the current sharing dead zone adjustment for the two-path LLC resonant conversion circuits is set to 2A. The intervention values of the current sharing derating adjustment and the current sharing protection intervention are set differently in different power segments, and the specific settings are as follows: (for reference, see Figure 13) When Po ≤ 15KW, ΔIc = 16.5A; when 15KW < Po ≤ 20KW, ΔIb = 11A, ΔIc = 13A; when 20KW < Po ≤ 30KW, ΔIb = 7.5A, ΔIc = 9.5A; when 30KW < Po ≤ 40KW, ΔIb = 4A, ΔIc = 6A. Among them, when Po ≤ 15KW, ΔIc = 16.5A is for the equal - current protection adjustment based on the resonant current difference, the output power, the derating adjustment result, and the protection time threshold. When 15KW < Po ≤ 20KW, ΔIb = 11A, ΔIc = 13A; when 20KW < Po ≤ 30KW, ΔIb = 7.5A, ΔIc = 9.5A; when 30KW < Po ≤ 40KW, ΔIb = 4A, ΔIc = 6A is for the equal - current protection adjustment only based on the resonant current difference, the output power, and the protection time threshold when the derating adjustment result is not received.

[0052] Before verifying the equal - current control method of the dual - path interleaved parallel LLC converter of the present invention, it is also necessary to test and formulate the upper limit of the dead - time for equal - current Tjmax. Refer to Figure 14 , and the data in the table are the test results of the upper limit of the dead - time for equal - current Tjmax that meet the test derating requirements and equal - current requirements under different loads (normally, the maximum deviation degree of the resonant parameters is only considered 10%). It can be seen from the table that when Po < 35KW, the device test derating margin is relatively sufficient. When Po = 35KW, it just meets the requirement. When Po > 35KW, it is necessary to reduce the deviation degree of the resonant parameters to meet the test derating, indicating that when the deviation of the resonant parameters is relatively large, simply limiting the upper limit of the dead - time for equal - current is not enough, and derating measures need to be added. According to this test result, a Tjmax data curve (curve 1) is plotted in Appendix Figure 5 . Theoretically, a set - value curve with a margin (taking 90% of the test result) is redrawn. If the Tjmax dead - time is required according to the set - value curve, the reliability of the product can be guaranteed. However, making a piece - wise curve is relatively complex, and from Figure 14 it can be seen that when Po < 35KW (the resonant parameter deviation is 10% and the equal - current performance is met), the test derating margin is still very large. Therefore, it is decided to merge the two curves into a straight line with the same slope (such as curve 2 in Appendix Figure 5 , which is easier to implement in the software algorithm). On this basis, the set - value curve with a 90% margin is obtained (such as curve 3 in Appendix Figure 5 ). After fitting this Tjmax curve into the DSP control software program for testing and verification, when Po < 35KW, the device test derating is sufficient, and this curve 3 passes the verification.

[0053] To facilitate the verification of the effectiveness of the present invention, the resonant parameters of the two - path resonant converter circuit need to take different values. From Figure 14It can be seen that a 10% deviation in the resonant parameters will cause derating under heavy load (this state can verify the current sharing dead-time regulation and current sharing derating control), but it will not cause current sharing protection. Therefore, two prototypes need to be prepared. One is a dual-channel interleaved LLC converter with a 10% deviation in the resonant parameters to verify the current sharing dead-time regulation and current sharing derating control, and the other is a dual-channel interleaved LLC converter with a 40% deviation in the resonant parameters to verify the current sharing protection. The resonant parameters of the two prototypes are as follows: Prototype 1 (the inductance and capacitance of the second path are both 5% higher): Lr1 = 26uH, Cr1 = 77nF, Lr2 = 27.3uH, Cr2 = 80.85nF; Prototype 2 (the inductance and capacitance of the second path are both 20% higher): Lr1 = 26uH, Cr1 = 77nF, Lr2 = 31.2uH, Cr2 = 92.4nF. Based on these two prototypes, the current sharing control method of the dual-channel interleaved LLC converter of the present invention is verified below.

[0054] The verification of the current sharing dead-time adjustment process is as follows (Prototype 1), (the process can refer to Figure 6 ) Step 1: Calculate the difference in the resonant currents of the two resonant converter circuits. The microcontroller outputs a driving signal to drive the switching tubes of the two LLC resonant conversion circuits to work. The resonant currents of the two resonant converter circuits are detected within each switching cycle, and after filtering, the effective values of the resonant currents of the two resonant converter circuits are obtained. Define the effective value of the first resonant current of the first resonant conversion circuit as IL1, and the effective value of the second resonant current of the second resonant conversion circuit as IL2. The absolute value of the resonant current difference △I = |IL1 - IL2|.

[0055] Step 2: Judge the intervention condition for current sharing dead-time adjustment. When the output power Po > 15KW and △I > 2A, the current sharing dead-time adjustment is triggered.

[0056] Step 3, execute the current sharing dead-time adjustment process. After triggering the current sharing dead-time adjustment, the △I obtained in Step 1 is sent to the DSP microcontroller, and the dead-time of the two resonant converter circuits is adjusted through digital PID control in a closed loop. The specific adjustment method is as follows: When IL1 > IL2 + 2 (here, define the current sharing dead-time of the first resonant conversion circuit as Tj1, and the current sharing dead-time of the second resonant conversion circuit as Tj2. Tj1 and Tj2 cannot have numerical values at the same time, and at least one of them must be 0). First, reduce Tj2. After Tj2 is reduced to 0, then increase Tj1 (if Tj2 is already 0, then directly adjust Tj1); when IL2 > IL1 + 2, first reduce Tj1. After Tj1 is reduced to 0, then increase Tj2 (if Tj1 is already 0, then directly adjust Tj2)); the microprocessor outputs complementary switching signals to perform closed-loop control on the two resonant converter circuits, making the absolute value of the resonant current difference △I smaller.

[0057] Step 4, the equal - current dead - time regulation is stable. After the absolute value of the resonant - current difference △I becomes smaller, repeat Steps 1 - 3 until the absolute value of the resonant - current difference △I is less than the required threshold (≤2A). After achieving equal - current between the two resonant - converter circuits, keep Tj1 and Tj2 unchanged, no longer adjust the equal - current dead - time, the equal - current regulation is stable, and the equal - current control ends. If one of the equal - current dead - times Tj1 or Tj2 is adjusted to Tjmax, the resonant converter operates according to the adjusted Tjmax (one of Tj1 and Tj2 is 0, and the other is Tjmax), and no longer adjusts the equal - current dead - time.

[0058] The verification of the equal - current dead - time regulation result is as follows: The state of Prototype 1 before adding equal - current regulation: Po = 20KW, IL1 = 24.94A, IL2 = 12.282A, △I = 12.685A, the equal - current dead - time regulation time Tj = |Ts1 - Ts2| = 0.015us (transmission - delay error and oscilloscope - measurement error, approximately 0), equal - current not regulated, the difference in the primary - side currents of the two resonant - converter circuits is very large. The working waveform diagrams of the two - path resonant currents are shown in Appendix Figure 9A , and the driving waveform diagrams of the two - path resonant - converter circuits are shown in Appendix Figure 10A The state of Prototype 1 after adding equal - current regulation: Po = 20KW, IL1 = 18.2A, IL2 = 18.6A, △I = 0.4A, the equal - current dead - time regulation time Tj = |Ts1 - Ts2| = 1.056us, equal - current regulation action. After adding the equal - current dead - time regulation function, △I < 2A, the equal - current effect is very good. The working waveform diagrams of the two - path resonant currents are shown in Appendix Figure 9B , and the driving waveform diagrams of the two - path resonant - converter circuits are shown in Appendix Figure 10B . It can be seen from the implementation examples that although there are differences in the circuit parameters of the two - path LLC resonant - conversion circuits in interleaved parallel operation, resulting in inconsistent resonant currents in the two - path LLC resonant - conversion circuits, after adopting the equal - current method proposed in the present invention, the resonant currents of the two - path LLC resonant - conversion circuits meet the equal - current requirements, balance the transmission power of the two - path LLC resonant - conversion circuits, and improve the reliability and stability of the entire power - supply system. The verification of the equal - current derating process is as follows, and the process can be seen in Appendix Figure 7 .

[0059] Among them, Step 1: Judging the intervention conditions of current sharing and derating. The microcontroller can calculate the current output power Po(n) through the output voltage and current sampling, and can also obtain the current two-way resonant currents IL1(n) and IL2(n) through the resonant current sampling circuit. The absolute value of the difference in resonant currents △I(n)=|IL1(n)-IL2(n)|. When the deviation of the two-way resonant parameters is small, the current sharing dead time adjustment can control the difference in the two-way LLC resonant currents within 2A for stable operation. However, when the deviation of the two-way resonant parameters is large, after the current sharing dead time adjustment reaches Tjmax (the current sharing adjustment reaches the limit), the current sharing performance requirements are still not met, and the difference in the two-way resonant currents will increase with the increase in the deviation degree of the resonant parameters. When it reaches a certain level, it will trigger the derating intervention condition. When Po>15KW and the absolute value of the difference between the two-way resonant currents is greater than the intervention value for 5 seconds, derating starts. The criteria for judging the intervention of current sharing and derating are as follows: Criterion A: Po≤15KW, no derating; Criterion B: The current sharing dead time is adjusted to Tjmax, 15KW<Po≤20KW, and |△I|>11A for 5S, triggering derating; Criterion C: The current sharing dead time is adjusted to Tjmax, 20KW<Po≤30KW, and |△I|>7.5A for 5S, triggering derating; Criterion D: The current sharing dead time is adjusted to Tjmax, 30KW<Po≤40KW, and |△I|>4A for 5S, triggering derating; Substituting the Po(n) and △I(n) calculated by the microcontroller into the above criterion conditions can determine whether the current sharing and derating are triggered.

[0060] It should be noted that the foregoing specific values are only examples. In other preferred embodiments of the present invention, different value ranges can also be selected. That is, when the output power is less than or equal to the derating adjustment power threshold, derating adjustment is stopped or not performed. For example, the current sharing derating adjustment intervention values include a first current sharing derating adjustment intervention value, a second current sharing derating adjustment intervention value, and a third current sharing derating adjustment intervention value; the derating adjustment power thresholds include a first derating adjustment power threshold, a second derating adjustment power threshold, a third derating adjustment power threshold, and a fourth derating adjustment power threshold. When the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the difference in resonant current is greater than the current sharing derating adjustment intervention value, the difference in resonant current is greater than the first current sharing derating adjustment intervention value, and the output power is greater than the first derating adjustment power threshold and less than or equal to the second derating adjustment power threshold, and all of these conditions continuously reach the derating time threshold, derating is triggered. Similarly, when the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the difference in resonant current is greater than the current sharing derating adjustment intervention value, the difference in resonant current is greater than the second current sharing derating adjustment intervention value, and the output power is greater than the second derating adjustment power threshold and less than or equal to the third derating adjustment power threshold, and all of these conditions continuously reach the derating time threshold, derating is triggered. When the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, the difference in resonant current is greater than the current sharing derating adjustment intervention value, the difference in resonant current is greater than the third current sharing derating adjustment intervention value, and the output power is greater than the third derating adjustment power threshold and less than or equal to the fourth derating adjustment power threshold, and all of these conditions continuously reach the derating time threshold, derating is triggered. The first current sharing derating adjustment intervention value, the second current sharing derating adjustment intervention value, and the third current sharing derating adjustment intervention value decrease in sequence; the first derating adjustment power threshold, the second derating adjustment power threshold, the third derating adjustment power threshold, and the fourth derating adjustment power threshold increase in sequence.

[0061] Step 2: Current sharing and derating adjustment process. After derating is triggered, according to different output power levels, substitute Po(n), IL1(n), and IL2(n) into the following formula to calculate the maximum output power Pomax(n + 1) after derating. There are three cases for calculating the derating amount: ① If the criterion B in Step 1 is triggered, the calculation result is: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)| - 11)*3; ② If the criterion C in Step 1 is triggered, the calculation result is: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)| - 7.5)*3; ③ If the criterion D in Step 1 is triggered, the calculation result is: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)| - 4)*3; Note: Po(n)--the current output power, Pomax(n + 1)--the maximum power limit after derating; Derating method: for every 1A exceeding the intervention value, derate by 3KW (derating is performed based on the current output power); After the derating is calculated, send the maximum power Pomax(n + 1) after derating to the microcontroller. The microcontroller controls the output power through digital PID control closed-loop regulation to reduce the output power to Pomax(n + 1). When Pomax(n + 1) ≤ 15KW, take Pomax(n + 1)=15KW (the lower limit of Po is 15KW).

[0062] Step 3: Current sharing and derating stabilization. After derating, continue to perform a new round of derating strategy determination, repeating the actions in Step 1 and Step 2 until △I < derating intervention value or Po ≤ 15KW, then keep the current Pomax(n) working without further derating, and the current sharing and derating control ends.

[0063] Verification of current sharing and derating adjustment results: Before adding current sharing and derating adjustment to Prototype 1, the state was: Po = 40KW, IL1 = 38.137A, IL2 = 31.865A, △I = 6.272A, the current sharing dead zone adjustment time Tj = |Ts1 - Ts2| = 0.665us (adjusted to the limit), current sharing adjustment action, △I > 4A. After the difference in the primary side currents of the two resonant converter circuits was adjusted to the limit, it was still relatively large. For the working waveform diagram, refer to the appendix Figure 11A After adding current sharing and derating adjustment to Prototype 1, the state was: Po = 32.5KW (stable power after derating), IL1 = 29.586A, IL2 = 27.945A, △I = 1.641A, the current sharing dead zone adjustment time Tj = |Ts1 - Ts2| = 0.746us (not reaching the limit, the lower the load, the larger Tjmax). When the current sharing adjustment action was performed while adding the current sharing and derating adjustment function, △I < 4A, and the effect was very good. For the working waveform diagram, refer to the appendix Figure 11B 。

[0064] It can be seen from the implementation examples that although the function of regulating the current sharing dead zone is added, when the circuit parameters of the two-way LLC resonant conversion circuit are quite different, the current sharing performance cannot be adjusted very well even when the current sharing dead zone regulation function is adjusted to the limit. At this time, the thermal risk of the resonant converter with the larger current is relatively high. However, after adopting the current sharing derating method proposed by the present invention, the effective value and difference of the resonant currents of the two-way LLC resonant conversion circuit are reduced by derating, which not only meets the current sharing requirements but also avoids overheating damage of a single circuit, improving the reliability and stability of the entire power supply system.

[0065] The verification of the current sharing protection process is as follows. The process can be referred to in the appendix Figure 8 。

[0066] Step 1: Judgment of the intervention of current sharing protection. If the resonant parameters of the two-way LLC deviate severely or one of them is damaged, when a sudden heavy load is applied, the difference in resonant current △I will be very large, far exceeding the Figure 13 Current sharing protection intervention value in the table. First, current sharing derating is triggered. After derating to the lower limit of the output power (15KW), the difference in resonant current between the two paths is still very large (△I > △Ic). After a period of time, current sharing protection shutdown is triggered to avoid overheating damage of one of the two-way resonant converter circuits due to too large a load for a long time. Po ≤ 15KW, △Ic = 16.5A; 15KW < Po ≤ 20KW, △Ic = 13A; 20KW < Po ≤ 30KW, △Ic = 9.5A; 30KW < Po ≤ 40KW, △Ic = 6A. Among them, Po ≤ 15KW, △Ic = 16.5A is for current sharing protection regulation based on the difference in resonant current, the output power, the derating adjustment result, and the protection time threshold. 15KW < Po ≤ 20KW, △Ib = 11A, △Ic = 13A; 20KW < Po ≤ 30KW, △Ib = 7.5A, △Ic = 9.5A; 30KW < Po ≤ 40KW, △Ib = 4A, △Ic = 6A is for current sharing protection regulation only based on the difference in resonant current, the output power, and the protection time threshold when the derating adjustment result is not received.

[0067] Verification of the current sharing protection result: The state of prototype 2 before adding current sharing protection: Po = 40KW (CR dynamic sudden load). Due to the large difference in resonant parameters between the two-way resonant converter circuits, the current sharing adjustment is first triggered during the load. After the current sharing adjustment reaches the limit, current sharing derating is triggered, and the derating reaches the minimum output power Pomax = 15KW. At this time, IL1 = 24.716A, IL2 = 5.492A, △I = 19.224A, △I > 4A. Even though the output power is very low at this time, △I is relatively large, which affects the reliability of the power supply product during long-term operation. The working waveform diagram can be referred to in the appendix Figure 12Status of the prototype 2 after adding current sharing protection: Po = 40KW (CR dynamic sudden load). The dynamic process is the same as above. After stabilization, even if the output power is very low, but △I is relatively large (>16.5A). After 10S, the power supply shuts down due to current sharing protection.

[0068] The present invention detects the resonant current values of two LLC resonant conversion circuits, and closed-loop adjusts the dead time of the resonant converter with the larger resonant current value, so that the interleaved parallel LLC resonant converter can perform current sharing control on the resonant current without being affected by circuit parameter deviations, and realizes the power transmission balance of the interleaved parallel LLC resonant converter. The switching signal frequencies of the two LLC resonant conversion circuits are the same and the phases are interleaved, reducing the output current ripple of the interleaved parallel LLC resonant converter. Through this current sharing adjustment method, the reliability and stability of the operation of the interleaved parallel LLC resonant converter are improved. The present invention clarifies that the ability to adjust current sharing with dead time has a certain upper limit, and this upper limit value needs to be tested and determined according to the actual requirements of the product. After the current sharing adjustment of the two resonant converter circuit parameters deviates too much to the limit, the present invention uses the difference between the two resonant currents for current sharing derating control. This current sharing derating strategy has sufficient judgment value space (derating intervention value) and time (5S), will not trigger derating by mistake, and can also respond quickly (within 5S) to situations exceeding the judgment value, and derate in time to ensure the stability and reliability of the operation of the resonant converter. After the current sharing adjustment and the current sharing derating strategy, the present invention further adds current sharing protection measures, which can quickly protect and shut down in some extreme situations (such as extremely large resonant parameter deviations or damage to a single resonant converter, etc.). The current sharing protection judgment value also has a certain space and time, will not trigger protection by mistake, and can also protect the situation that needs protection in time.

[0069] Although the present invention is described through specific embodiments, those skilled in the art should understand that various transformations and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. In addition, various modifications can be made to the present invention for specific situations or materials without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims of the present invention.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A current sharing control method for a dual-channel interleaved parallel LLC converter, characterized in that, Including: Obtain the effective value of the first resonant current of the first resonant conversion circuit of the dual-path interleaved LLC converter and the effective value of the second resonant current of the second resonant conversion circuit, and calculate the resonant current difference based on the effective value of the first resonant current and the effective value of the second resonant current; When the resonant current difference is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, perform current sharing dead time adjustment to obtain the dead time adjustment result.

2. The current sharing control method of the dual-channel interleaved parallel LLC converter according to claim 1, wherein The step of when the resonant current difference is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, perform current sharing dead time adjustment to obtain the dead time adjustment result, includes: Obtain the upper limit of the current sharing dead time based on the characteristics of the dual-path interleaved LLC converter; When the resonant current difference is greater than the current sharing dead time adjustment intervention value and the output power is greater than the dead time adjustment power threshold, close-loop adjust the current sharing dead time of the first resonant conversion circuit and the second resonant conversion circuit based on the resonant current difference until the resonant current difference is less than or equal to the current sharing dead time adjustment intervention value or the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time.

3. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 2, characterized in that, The step of close-loop adjust the current sharing dead time of the first resonant conversion circuit and the second resonant conversion circuit based on the resonant current difference until the resonant current difference is less than or equal to the current sharing dead time adjustment intervention value or the current sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current sharing dead time, includes: When the effective value of the first resonant current is greater than the effective value of the second resonant current, close-loop adjust the current sharing dead time of the second resonant conversion circuit to 0, then adjust the current sharing dead time of the first resonant conversion circuit to the upper limit of the current sharing dead time, and then control the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current sharing dead time; When the effective value of the second resonant current is greater than the effective value of the first resonant current, close-loop adjust the current sharing dead time of the first resonant conversion circuit to 0, then adjust the current sharing dead time of the second resonant conversion circuit to the upper limit of the current sharing dead time, and then control the first resonant conversion circuit and the second resonant conversion circuit to operate at the adjusted current sharing dead time.

4. The current sharing control method of the dual-channel interleaved parallel LLC converter according to any one of claims 1 to 3, characterized in that, Further including: Perform derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold.

5. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 4, characterized in that, The step of perform derating adjustment based on the resonant current difference, the output power, the dead time adjustment result, and the derating time threshold, includes: When the current-sharing dead time of the first resonant conversion circuit or the second resonant conversion circuit reaches the upper limit of the current-sharing dead time, the difference between the resonant currents is greater than the intervention value of current-sharing derating adjustment, and the output power is greater than the derating adjustment power threshold, and all these conditions continuously reach the derating time threshold, calculate the derated output power based on the output power, the effective value of the first resonant current, the effective value of the second resonant current, the difference between the resonant currents, and the intervention value of current-sharing derating adjustment; Control the dual-path interleaved LLC converter to output according to the derated output power; Repeat the above steps until the difference between the resonant currents is less than the intervention value of derating adjustment or the output power is less than or equal to the derating adjustment power threshold.

6. The current sharing control method of the dual-channel interleaved parallel LLC converter according to claim 5, characterized in that, Calculate the derated output power based on the following formula: Pomax(n + 1)=Po(n)-(|IL1(n)-IL2(n)|-△Ib)*X; Where Po(n) represents the output power, Pomax(n + 1) represents the derated output power, △Ib represents the intervention value of current-sharing derating adjustment, IL1(n) represents the effective value of the first resonant current, IL2(n) represents the effective value of the second resonant current, X represents the derating speed, and n represents the current sampling time.

7. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 5, wherein The derating adjustment based on the difference between the resonant currents, the output power, the dead time adjustment result, and the derating time threshold further includes: Maintain the current output power when the output power is less than or equal to the derating protection power threshold and when the difference between the resonant currents is less than the intervention value of current-sharing derating adjustment; when the output power is less than the first current-sharing derating power threshold, output at the minimum power and no longer derate.

8. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 5, characterized in that, The intervention value of current-sharing derating adjustment includes the first intervention value of current-sharing derating adjustment, the second intervention value of current-sharing derating adjustment, and the third intervention value of current-sharing derating adjustment; the derating adjustment power threshold includes the first derating adjustment power threshold, the second derating adjustment power threshold, the third derating adjustment power threshold, and the fourth derating adjustment power threshold; The difference between the resonant currents is greater than the intervention value of current-sharing derating adjustment and the output power is greater than the derating adjustment power threshold, including: The difference between the resonant currents is greater than the first intervention value of current-sharing derating adjustment, and the output power is greater than the first derating adjustment power threshold and less than or equal to the second derating adjustment power threshold; Or The difference between the resonant currents is greater than the second intervention value of current-sharing derating adjustment, and the output power is greater than the second derating adjustment power threshold and less than or equal to the third derating adjustment power threshold; or The difference between the resonant currents is greater than the third intervention value of current-sharing derating adjustment, and the output power is greater than the third derating adjustment power threshold and less than or equal to the fourth derating adjustment power threshold; The first intervention value of current-sharing derating adjustment, the second intervention value of current-sharing derating adjustment, and the third intervention value of current-sharing derating adjustment decrease in sequence; The first derating adjustment power threshold, the second derating adjustment power threshold, the third derating adjustment power threshold, and the fourth derating adjustment power threshold increase in sequence.

9. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 5, wherein Further includes: Perform current sharing protection regulation based on the resonant current difference, the output power, the derating regulation result, and the protection time threshold.

10. The current sharing control method of the dual-path interleaved parallel LLC converter according to claim 9, wherein, The performing current sharing protection regulation based on the resonant current difference, the output power, the derating regulation result, and the protection time threshold includes: When the resonant current difference is greater than the current sharing protection regulation intervention value and the output power is less than the derating protection power threshold for the protection time threshold continuously, control the dual-channel interleaved LLC converter to shut down; and When the derating regulation result is not received, perform current sharing protection regulation only based on the resonant current difference, the output power, and the protection time threshold.

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