A flyback converter voltage equalization control method and a flyback converter

Abstract

The application relates to a voltage equalization control method of a flyback converter and the flyback converter, which comprises the following steps: sampling the output voltage of each flyback module of N flyback modules which are in parallel at the input and in series at the output, comparing the output voltage with a voltage setting value, and marking the N flyback modules as over-standard flyback modules and standard flyback modules based on the comparison result; calculating the flyback switch period and the conduction time of the N flyback modules; correcting the conduction time of the over-standard flyback modules or correcting the conduction time of the standard flyback modules to obtain first corrected conduction time or second corrected conduction time; and generating N flyback drive signals for controlling the N flyback modules based on the flyback switch period, the conduction time, and the first corrected conduction time or the second corrected conduction time. The application can realize voltage equalization.

Description

Technical Field

[0001] This invention relates to the field of flyback transformers, and more specifically, to a voltage equalization control method for a flyback converter and a flyback converter. Background Technology

[0002] Modern electric vehicle charging stations, server power supplies, and energy storage converters have increasingly higher requirements for output voltage levels and power density. To improve the output voltage level, an Input-Parallel Output-Series (IPOS) architecture is typically used. In this architecture, the input terminals of each power conversion module are connected in parallel to the same DC bus, and the output terminals are connected in series to increase the output voltage, giving the system advantages such as high output voltage gain and low switching voltage stress.

[0003] Flyback converters are simple in structure, low in cost, and have built-in electrical isolation, making them a common base module in IPOS architectures. However, in practical applications, the transformer turns ratio, inductance, and drive signal delay of each flyback converter cannot be perfectly consistent, resulting in uneven output voltage across all converters. This uneven output voltage can cause numerous adverse effects, such as the flyback converter with higher output voltage needing to withstand excessive power, leading to uneven heat distribution; and the flyback converter with higher output voltage needing to withstand excessive voltage stress, which can even damage the switching transistors in severe cases. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a voltage equalization control method for a flyback converter, which enables voltage equalization at the output, in view of the above-mentioned defects of the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is: constructing a voltage equalization control method for a flyback converter, wherein the flyback converter includes N flyback modules, the inputs of the N flyback modules are connected in parallel and the outputs are connected in series, where N is a positive integer and N≧2; the voltage equalization control method for the flyback converter includes: The output voltage of each flyback module is sampled and compared with the voltage set value. Based on the comparison result, the N flyback modules are marked as out-of-standard flyback modules and standard flyback modules, respectively. Calculate the flyback switching cycle and conduction time of the N-channel flyback module; The conduction time of the over-standard flyback module or the conduction time of the compliant flyback module is corrected to obtain a first corrected conduction time or a second corrected conduction time. Based on the flyback switch cycle, the on-time, and the first or second corrected on-time, N flyback drive signals are generated to control the N flyback modules.

[0006] In the voltage equalization control method for the flyback converter described in this invention, the output voltage of each flyback module is sampled, and the output voltage is compared with a voltage setpoint. Based on the comparison result, the N flyback modules are respectively marked as out-of-range flyback modules and compliant flyback modules, including: Sample the output voltage of each flyback module and calculate the average output voltage of the N flyback modules; The voltage setting value is calculated based on the average output voltage and the preset threshold value; The output voltage of each flyback module is compared with the voltage setting value. Flyback modules with output voltage greater than the voltage setting value are marked as out-of-standard flyback modules, and flyback modules with output voltage less than the voltage setting value are marked as compliant flyback modules.

[0007] In the voltage equalization control method for the flyback converter described in this invention, calculating the flyback switching period and conduction time of the N-channel flyback modules includes: The difference between the total output voltage of the flyback converter and the voltage setpoint is input into the outer loop PI controller to obtain the PI calculation result. The PI calculation result, the input voltage of the flyback converter, and the total output voltage are input into the QR calculation unit to calculate the flyback switching cycle and conduction time of the N-channel flyback module.

[0008] In the voltage equalization control method for the flyback converter described in this invention, correcting the conduction time of the over-standard flyback module or the conduction time of the standard-compliant flyback module to obtain a first corrected conduction time or a second corrected conduction time includes: The conduction time of each of the out-of-standard flyback modules is corrected to obtain a first corrected conduction time, while the conduction time of any of the compliant flyback modules is not corrected; or The conduction time of each of the standard-compliant flyback modules is corrected to obtain a second corrected conduction time, while the conduction time of any of the non-standard-compliant flyback modules is not corrected.

[0009] In the voltage equalization control method for the flyback converter described in this invention, the first corrected conduction time is equal to the conduction time minus the correction amount. ; The second corrected conduction time is equal to the conduction time plus the correction amount. ;

[0010] in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. represents the output voltage of the flyback module, and n represents the flyback transformer turns ratio of the flyback module.

[0011] In the voltage equalization control method for the flyback converter described in this invention, the resonant period The value is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or The resonance period Obtained through calculation:

[0012] in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

[0013] In the voltage equalization control method for the flyback converter described in this invention, N flyback drive signals for controlling the N flyback modules are generated based on the flyback switching period, the conduction time, and the first corrected conduction time or the second corrected conduction time, including: Based on the flyback switching period and the conduction time, an EPWM-based EPWM-based flyback drive signal is generated to control the standard-compliant flyback module, and an over-standard flyback drive signal is generated based on the flyback switching period and the first corrected conduction time to control the over-standard flyback module; or Based on the flyback switching period and the conduction time, an over-standard flyback drive signal for controlling the over-standard flyback module is generated by EPWM assignment, and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module is generated based on the flyback switching period and the second corrected conduction time.

[0014] Another technical solution adopted by the present invention to solve its technical problem is to construct a flyback converter, comprising: N-way flyback modules, wherein the inputs of the N-way flyback modules are connected in parallel and the outputs are connected in series, where N is a positive integer and N≧2; The sampling module is used to sample the output voltage of each flyback module; The marking module is used to compare the output voltage of each flyback module with the voltage set value, and mark the N flyback modules as out-of-standard flyback modules and standard flyback modules respectively based on the comparison result; The calculation module is used to calculate the flyback switching cycle and conduction time of the N-channel flyback module; The on-time correction module is used to correct the on-time of the over-standard flyback module or the on-time of the compliant flyback module to obtain a first corrected on-time or a second corrected on-time. A drive signal generation module is used to generate N flyback drive signals for controlling the N flyback modules based on the flyback switch cycle, the conduction time, and the first corrected conduction time or the second corrected conduction time.

[0015] In the flyback converter of the present invention, the conduction time correction module is used to correct the conduction time of each of the out-of-standard flyback modules to obtain a first corrected conduction time, and does not correct the conduction time of any of the standard-compliant flyback modules; or The conduction time correction module is used to correct the conduction time of each of the standard-compliant flyback modules to obtain a second corrected conduction time, and does not correct the conduction time of any of the non-standard flyback modules. The first corrected conduction time is equal to the conduction time minus the correction amount. ; The second corrected conduction time is equal to the conduction time plus the correction amount. ;

[0016] in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. The output voltage of the flyback module is represented by , and n represents the flyback transformer turns ratio of the flyback module. The resonance period The value is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or The resonance period Obtained through calculation:

[0017] in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

[0018] In the flyback converter of the present invention, the marking module is used to calculate the average output voltage of the N flyback modules; calculate the voltage setting value based on the average output voltage and a preset threshold value; compare the output voltage of each flyback module with the voltage setting value, and mark the flyback module whose output voltage is greater than the voltage setting value as an out-of-standard flyback module, and mark the flyback module whose output voltage is less than the voltage setting value as a standard-compliant flyback module; The computing module includes: A voltage outer-loop PI controller is used to generate PI calculation results based on the difference between the total output voltage of the flyback converter and the voltage setpoint. The QR calculation unit is used to calculate the flyback switching cycle and conduction time of the N-channel flyback module based on the PI calculation results, the input voltage of the flyback converter, and the total output voltage. The drive signal generation module is used to generate a standard-compliant flyback drive signal for controlling the standard-compliant flyback module by EPWM assignment based on the flyback switch period and the conduction time, and an over-standard flyback drive signal for controlling the over-standard flyback module based on the flyback switch period and the first corrected conduction time; or to generate an over-standard flyback drive signal for controlling the over-standard flyback module by EPWM assignment based on the flyback switch period and the conduction time, and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module based on the flyback switch period and the second corrected conduction time.

[0019] The voltage equalization control method and flyback converter of the present invention, by comparing the output voltage of each channel in real time, mark the N flyback modules as over-standard flyback modules and standard flyback modules respectively, and then correct the conduction time Ton of the over-standard flyback module or the standard flyback module, while not correcting the conduction time of the other flyback modules, can achieve voltage equalization. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a block diagram of the flyback converter to which the voltage equalization control method of the flyback converter of the present invention is applicable; Figure 2 This is a flowchart of a preferred embodiment of the voltage equalization control method for the flyback converter of the present invention; Figure 3 This is a schematic diagram illustrating the calculation process of the flyback switching period, conduction time, and flyback drive signal for the out-of-standard path and the flyback drive signal for the standard path in the voltage equalization control method of the flyback converter of the present invention. Figure 4This is a schematic diagram illustrating the derivation process of the correction amount in the voltage equalization control method of the flyback converter of the present invention; Figure 5 This is a schematic block diagram of a preferred embodiment of the flyback converter of the present invention; Figure 6 This is a circuit diagram of a flyback converter to which the voltage equalization control method of the flyback converter of the present invention is applicable. Figure 7 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The diagram shows the voltage, current, and drive signal waveforms of the flyback converter. Figure 8 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The instantaneous waveforms of the voltage, current, and drive signal of the flyback converter are shown below. Figure 9 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The following are steady-state waveforms of the voltage, current, and drive signal of the flyback converter. Figure 10 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The diagram shows the dynamic waveforms of the voltage, current, and drive signal of the flyback converter. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0022] like Figure 1 As shown, the flyback converter may include N flyback modules, with their inputs connected in parallel and their outputs connected in series, where N is a positive integer and N≧2. The flyback modules can be constructed based on any known flyback module in the art. Those skilled in the art will understand that a flyback module necessarily includes a primary-side switch, a flyback transformer, and a coupling inductor. Of course, the flyback module may further include an input rectifier filter circuit, an output rectifier diode, an output filter capacitor, and a control circuit, etc. The voltage equalization control method of the flyback converter of the present invention is applicable to flyback modules of any topology.

[0023] Current voltage equalization control in flyback converters is generally achieved through an outer-loop PI controller, a QR calculation module, and EPWM assignment. The voltage setpoint of the outer-loop PI controller is VoRef, which is fed back as the total output voltage Vo of the flyback converter. The difference between the voltage setpoint VoRef and the total output voltage Vo is input to the outer-loop PI controller to obtain the PI calculation result. The PI calculation result, the input voltage of the flyback converter, and the total output voltage Vo of the flyback converter are used as inputs to the QR calculation module. The output of the QR calculation module is N (N is an integer greater than or equal to 2) flyback switching periods Ts and on-time Ton. Then, based on the flyback switching periods Ts and on-time Ton, N flyback drive signals are generated through EPWM assignment. These N flyback drive signals then control the primary-side switches (i.e., main switches) in the N flyback modules.

[0024] The voltage equalization control method of the flyback converter of the present invention achieves voltage equalization by comparing the output voltages of each channel in real time and correcting the conduction time (Ton) of the flyback modules with excessively high or low output voltages, while leaving the conduction time of the other flyback modules uncorrected. When each flyback module operates in valley conduction mode, the resonant characteristics of the QR mode can be utilized to achieve voltage equalization while maintaining the interleaved and valley conduction states of multiple flyback modules. Figure 2 This is a flowchart of a preferred embodiment of the voltage equalization control method for the flyback converter of the present invention.

[0025] like Figure 2 As shown, in step S1, the output voltage of each flyback module is sampled, and the output voltage is compared with the voltage setting value. Based on the comparison result, the N flyback modules are respectively marked as out-of-standard flyback modules and standard flyback modules.

[0026] In a preferred embodiment of the present invention, the output voltage of each flyback module is sampled, and the average output voltage of the N flyback modules is calculated; the voltage setting value is calculated based on the average output voltage and a preset threshold value; the output voltage of each flyback module is compared with the voltage setting value, and the flyback module whose output voltage is greater than the voltage setting value is marked as an out-of-standard flyback module, and the flyback module whose output voltage is less than the voltage setting value is marked as a compliant flyback module.

[0027] In a preferred embodiment of the present invention, the output voltage Vo_1~Vo_N of each flyback module is sampled. Then, the average output voltage Vo_avg of the N flyback modules is calculated based on the N output voltages Vo_1~Vo_N. Then, the voltage setting value Vo_avg+Vo_delta is calculated based on the average output voltage Vo_avg and a preset threshold value Vo_delta (Vo_delta>=0). Then, the output voltage Vo_1~Vo_N of each flyback module is compared with the voltage setting value Vo_avg+Vo_delta. When Vo_n (n∈(1~N))>Vo_avg+Vo_delta (Vo_delta is the preset threshold value, Vo_delta>=0), the nth flyback module is recorded as an out-of-standard flyback module; otherwise, it is recorded as a compliant flyback module.

[0028] In step S2, the flyback switching period and on-time of the N-channel flyback module are calculated. The flyback switching period and on-time of the flyback module can be calculated using any known method in the art.

[0029] In a preferred embodiment of the present invention, the difference between the total output voltage of the flyback converter and the voltage setpoint can be input to the voltage outer loop PI controller to obtain the PI calculation result; the PI calculation result, the input voltage of the flyback converter, and the total output voltage are input to the QR calculation unit to calculate the flyback switching cycle and conduction time of the N-channel flyback module.

[0030] Figure 3 This is a schematic diagram illustrating the calculation process of the flyback switching period, conduction time, and flyback drive signals for the out-of-range and within-range paths in the voltage equalization control method of the flyback converter of the present invention. Figure 3 As shown, the voltage setpoint of the outer-loop PI controller is VoRef, and the feedback is the total output voltage Vo of the flyback converter. The difference between the voltage setpoint VoRef and the total output voltage Vo is input to the outer-loop PI controller to obtain the PI calculation result. The PI calculation result, the input voltage of the flyback converter, and the total output voltage Vo of the flyback converter are used as the input of the QR calculation module. The output of the QR calculation module is N channels (N is an integer greater than or equal to 2) of flyback switching period Ts and conduction time Ton. Then, by assigning values ​​through EPWM, the over-standard flyback drive signal and the standard flyback drive signal can be obtained respectively. Here, the over-standard flyback drive signal has H outputs, and the standard flyback drive signal has L outputs, that is, the flyback transformer has N channels, where H channels are for the over-standard flyback module and L channels are for the standard flyback module.

[0031] In step S3, the conduction time of the over-standard flyback module or the conduction time of the compliant flyback module is corrected to obtain a first corrected conduction time or a second corrected conduction time.

[0032] In a preferred embodiment of the present invention, such as Figure 3 As shown, the conduction time of each of the non-compliant flyback modules can be corrected to obtain a first corrected conduction time, while the conduction time of any of the compliant flyback modules is not corrected. The first corrected conduction time is equal to the conduction time minus the correction amount. That is, for example Figure 3 As shown, the correction amount is subtracted from the conduction time Ton. The first corrected on-time is obtained, and then the first corrected on-time and the flyback switching period Ts are EPWM-assigned to obtain the flyback drive signal for the non-standard path. For the flyback module that meets the standard, its on-time is not corrected, that is, the on-time Ton and the flyback switching period Ts are directly EPWM-assigned to obtain the flyback drive signal for the standard path.

[0033] In another preferred embodiment of the invention, the conduction time of each of the standard-compliant flyback modules is corrected to obtain a second corrected conduction time, while the conduction time of any of the non-standard-compliant flyback modules is not corrected. The second corrected conduction time is equal to the conduction time plus a correction amount. .

[0034] In this invention,

[0035] in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. represents the output voltage of the flyback module, and n represents the flyback transformer turns ratio of the flyback module.

[0036] The resonance period The value is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or The resonance period Obtained through calculation:

[0037] in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

[0038] Figure 4 This is a schematic diagram illustrating the derivation process of the correction amount for the voltage equalization control method of the flyback converter of the present invention. Below, we will combine... Figure 4 For correction amount The derivation process is explained below. We correct the conduction time of the flyback module in the H-path that exceeds the standard to obtain the first corrected conduction time, without adjusting the conduction time of the flyback module in the L-path that meets the standard (or it can be understood as the correction amount of the flyback module in the L-path). Taking [example 1] as an example, the first corrected conduction time of each of the above-standard flyback modules is equal to the conduction time Ton minus the correction amount. To better compare the difference between the adjusted on-time (Ton) of the flyback module for out-of-standard paths and the flyback module for standard paths, in Figure 4 In this paper, the phase misalignment angle of the H-channel over-standard flyback module and the L-channel compliant flyback module is defined as 0°. It should be noted that the method of this invention is also applicable to application scenarios with phase misalignment angles ranging from 0° to 360°. Figure 4 In this diagram, the inductor current of the L-channel compliant flyback module is labeled as the L-channel inductor current, and the junction voltage of the flyback switch in the L-channel compliant flyback module is expressed as Vgs and Vds of the L-channel flyback switch. Similarly, the inductor current of the H-channel over-standard flyback module is labeled as the H-channel inductor current, and the junction voltage of the flyback switch in the H-channel over-standard flyback module is expressed as Vgs and Vds of the H-channel flyback switch. The over-standard flyback module does not adjust its on-time Ton during switching cycle 1, but decreases its on-time Ton during switching cycle 2. To obtain the first corrected on-time, the voltage equalization principle is as follows: If the output voltage of the flyback module in the over-limit circuit is higher than the voltage setpoint (average output voltage Vo_avg + preset threshold Vo_delta, Vo_delta>=0), then the average current during the switching cycle of the flyback module in the over-limit circuit needs to be reduced to lower the output voltage of the flyback module. The method to reduce the average current during the switching cycle is to reduce the on-time Ton of the flyback module in the over-limit circuit, and the reduction amount is the correction amount. When the on-time Ton of the flyback module in the over-standard circuit is reduced, the peak inductor current also decreases, and the demagnetizing time Tr also decreases. The reduction in demagnetizing time Tr plus the reduction in on-time Ton just causes the junction capacitance voltage Vds of the primary-side switch (i.e., the flyback switch) of the over-standard circuit flyback module to have one more resonant cycle. Therefore, it can also ensure valley-level conduction and that the switching frequencies of the L-flyback module and the over-standard circuit flyback module are consistent.

[0039] Correction amount The derivation process is as follows.

[0040] Based on the inductor volt-second balance principle, it is not difficult to deduce the decrease in demagnetization time Tr. for:

[0041] The decrease in demagnetization time plus the decrease in conduction time Ton equals one resonant period. :

[0042] The resonant period Tres is a known quantity. The resonant period is obtained by measuring the junction capacitance voltage Vds of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module, or by calculating it using the following formula. The resonant period... Obtained through calculation:

[0043] in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

[0044] therefore:

[0045] In special cases, the decrease in Ton is one. If the pressure is still insufficient to equalize, the reduction in Ton needs to be further increased, so that... ,therefore: ; where M is an integer greater than or equal to 1.

[0046] It should be noted that, although the correction amount was reduced by decreasing the on-time Ton of the flyback module in the over-standard path. As will be apparent to those skilled in the art based on the foregoing analysis, it is also possible to change the conduction time of the flyback modules in the compliant paths instead of altering the conduction time of the flyback modules in the non-compliant paths. Specifically, the conduction time of each compliant flyback module in the compliant path can be modified to obtain a second modified conduction time, without modifying the conduction time of any of the flyback modules in the non-compliant paths. Furthermore, the second modified conduction time is equal to the conduction time plus the modification amount. The derivation process is similar and will not be repeated here. However, it should be noted that when the conduction time of each of the standard-compliant flyback modules is corrected to obtain the second corrected conduction time, and the conduction time of any of the non-standard-compliant flyback modules is not corrected, the demagnetization time Tr ≥ 1.5 * resonant period is generally considered to be corrected. At this time, voltage equalization can be achieved in valley conduction mode, but when the demagnetization time Tr < 1.5 * resonant period. When the demagnetization time Tr is smaller, it will gradually deviate from the valley bottom and even enter continuous mode.

[0047] In step S4, N flyback drive signals for controlling the N flyback modules are generated based on the flyback switch cycle, the on-time, and the first corrected on-time or the second corrected on-time. Figure 3 This is a schematic diagram illustrating the calculation process of the flyback switching period, conduction time, and overrun flyback drive signal in the voltage equalization control method of the flyback converter of the present invention.

[0048] like Figure 3 As shown, when the conduction time of each of the out-of-standard flyback modules is corrected to obtain a first corrected conduction time, and the conduction time of any of the standard-compliant flyback modules is not corrected, a standard-compliant flyback drive signal for controlling the standard-compliant flyback module is generated by EPWM assignment based on the flyback switching period and the conduction time, and an out-of-standard flyback drive signal for controlling the out-of-standard flyback module is generated based on the flyback switching period and the first corrected conduction time.

[0049] Of course, when the conduction time of each of the standard-compliant flyback modules is corrected to obtain the second corrected conduction time, and the conduction time of any of the non-standard-compliant flyback modules is not corrected, similarly, an over-standard-compliant flyback drive signal for controlling the non-standard-compliant flyback module and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module can be generated by EPWM assignment based on the flyback switching period and the conduction time.

[0050] The voltage equalization control method for flyback converters of this invention, when the flyback converter operates in valley conduction mode, only shortens or extends the on-time of the switching transistors of flyback modules whose output voltage is higher than the voltage setpoint (average output voltage Vo_avg + preset threshold Vo_delta, Vo_delta>=0) based on a correction amount. This solves the voltage imbalance problem of multiple flyback outputs connected in series, and also has many advantages such as simple control, fast response speed, valley conduction, no frequency hopping, and no impact on phase reversal. In the voltage equalization control method of flyback converters of this invention, a precise adjustment method based on circuit physical parameters is adopted. This makes the adjustment amount It can automatically adapt to the current input and output voltages, with high voltage equalization accuracy and fast dynamic response speed, without the need for complex PI loop parameter tuning. In the voltage equalization control method of the flyback converter of this invention, only the flyback module in the out-of-range or in-range path is adjusted, shortening or extending its conduction time Ton, breaking the coupling of the bidirectional closed-loop regulation, eliminating the risk of self-excited oscillation of the voltage equalization loop, and the control logic is simple and robust. In the voltage equalization control method of the flyback converter of this invention, the correction amount The resonant time is adjusted precisely to change by one resonant cycle, ensuring that valley-level conduction is still achieved during the voltage equalization adjustment process, thus improving efficiency. Simultaneously, the switching cycle Ts is not affected, avoiding EMI performance degradation caused by frequency hopping. Furthermore, the voltage equalization control method for the flyback converter of this invention only adjusts the on-time, maintaining consistency in the switching frequencies of the out-of-standard and standard-compliant flyback modules. This prevents phase instability caused by inconsistent switching frequencies between the out-of-standard and standard-compliant flyback modules, which could further increase input current ripple. The voltage equalization control method for the flyback converter of this invention, by adjusting the on-time Ton, ensures that inductor magnetic balance is maintained throughout the voltage equalization adjustment process, preventing inductor bias from entering CCM mode and improving system reliability. The voltage equalization control method for the flyback converter of this invention is applicable to various charging modules, three-phase single-stage inverters, and micro-inverters, including flyback converters.

[0051] Figure 5 This is a schematic block diagram of a preferred embodiment of the flyback converter of the present invention. Figure 5 As shown, the flyback converter includes: N flyback modules 1~N, a sampling module 100, a marking module 200, a calculation module 300, a conduction time correction module 400, and a drive signal generation module 500. Figure 5 As shown, the inputs of the N flyback modules 1 to N are connected in parallel and the outputs are connected in series, where N is a positive integer and N≧2; the sampling module 100 is used to sample the output voltage of each flyback module; the marking module 200 is used to compare the output voltage of each flyback module with the voltage set value, and based on the comparison result, the N flyback modules are marked as out-of-standard flyback modules and standard flyback modules respectively; the calculation module 300 is used to calculate the flyback switching cycle and conduction time of the N flyback modules; the conduction time correction module 400 is used to correct the conduction time of the out-of-standard flyback modules or the conduction time of the standard flyback modules to obtain a first corrected conduction time or a second corrected conduction time; the drive signal generation module 500 is used to generate N flyback drive signals for controlling the N flyback modules based on the flyback switching cycle, the conduction time, and the first corrected conduction time or the second corrected conduction time.

[0052] The marking module 200 is further used to average the output voltage of the N flyback modules; calculate the voltage setting value based on the average output voltage and the preset threshold value; compare the output voltage of each flyback module with the voltage setting value, and mark the flyback module whose output voltage is greater than the voltage setting value as an out-of-standard flyback module, and mark the flyback module whose output voltage is less than the voltage setting value as a compliant flyback module.

[0053] The calculation module 300 preferably includes: a voltage outer loop PI controller, used to generate PI calculation results based on the difference between the total output voltage of the flyback converter and the voltage setpoint; and a QR calculation unit, used to calculate the flyback switching cycle and conduction time of the N-channel flyback module based on the PI calculation results, the input voltage of the flyback converter, and the total output voltage.

[0054] The conduction time correction module 400 is used to correct the conduction time of each of the out-of-standard flyback modules to obtain a first corrected conduction time, and not to correct the conduction time of any of the standard-compliant flyback modules; or the conduction time correction module 400 is used to correct the conduction time of each of the standard-compliant flyback modules to obtain a second corrected conduction time, and not to correct the conduction time of any of the out-of-standard flyback modules; the first corrected conduction time is equal to the conduction time minus the correction amount. The second corrected conduction time is equal to the conduction time plus the correction amount. ;

[0055] in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. represents the output voltage of the flyback module, and n represents the flyback transformer turns ratio of the flyback module.

[0056] Preferably, the resonance period The resonance period is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or the resonant period Obtained through calculation:

[0057] in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

[0058] The drive signal generation module 500 is used to generate a standard-compliant flyback drive signal for controlling the standard-compliant flyback module by EPWM assignment based on the flyback switch period and the conduction time, and an over-standard flyback drive signal for controlling the over-standard flyback module based on the flyback switch period and the first corrected conduction time; or to generate an over-standard flyback drive signal for controlling the over-standard flyback module by EPWM assignment based on the flyback switch period and the conduction time, and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module based on the flyback switch period and the second corrected conduction time.

[0059] Here, the N-channel flyback modules 1 to N can be constructed using any known flyback module in the art. The sampling module 100, the marking module 200, the calculation module 300, the conduction time correction module 400, and the drive signal generation module 500 can be constructed based on common knowledge in the art and the aforementioned voltage equalization control method for flyback converters, and will not be elaborated further here.

[0060] To verify the voltage equalization control method of the flyback converter and the effectiveness of the flyback converter of the present invention, a system was built in the PSIM environment. Figure 6 The simulation model of the flyback converter shown is used for verification. Figure 6 The parameters of the flyback converter shown are as follows:

[0061]

[0062] To simulate the discreteness of actual parameters, the upper and lower flyback inductors of the two flyback modules were set to 30uH and 31uH, respectively. A preset threshold value Vo_delta=0 and an adjustment coefficient M=1 were set. Voltage equalization adjustment was not performed before 20ms, and the voltage equalization control method of this invention was activated after 20ms. The simulation waveform is shown below. Figures 7-10 As shown. Figure 7 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The diagram shows the voltage, current, and drive signal waveforms of the flyback converter. Figure 8 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The instantaneous waveforms of the voltage, current, and drive signal of the flyback converter are shown below. Figure 9 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The following are steady-state waveforms of the voltage, current, and drive signal of the flyback converter. Figure 10 The voltage equalization control method of the flyback converter of the present invention is applicable to Figure 6 The diagram shows the dynamic waveforms of the voltage, current, and drive signal of the flyback converter. Figures 7-10In the above, the operating conditions are: input voltage 500V, output voltage 1000V, and load power 12KW; Vout1 and Vout2 are the upper flyback output voltage and lower flyback output voltage, I1 and I2 are the upper flyback inductor current and lower flyback inductor current, G1 and G2 are the drive signals for the upper flyback switch and the lower flyback switch, respectively; Vds1 and Vds2 are the junction capacitance voltages for the upper flyback switch and the lower flyback switch, respectively.

[0063] like Figures 7-10 As shown, after the voltage equalization control method of this invention is activated at 20ms, the output voltage difference between the two flyback modules gradually decreases until equalization occurs. The output voltage waveform is smooth during the equalization process, with no oscillation or overshoot. The flyback drive signal G1 of the first flyback module has a conduction time of 2.67µs, and the flyback drive signal G2 of the second flyback module has a conduction time of 3.21µs. =0.54us. Both flyback modules can maintain valley-level conduction and maintain a 180° phase shift. After entering steady state, the output voltages of the two flyback modules are basically the same, achieving voltage equalization. At 20ms, when the load is changed from 1.2KW to 12KW, the output voltages of the two flyback modules still remain consistent, and no voltage imbalance occurs. The voltage equalization control method of this invention performs excellently in large dynamic processes.

[0064] Although the present invention has been described through specific embodiments, those skilled in the art will understand that various modifications and equivalent substitutions can be made to the invention without departing from its scope. Furthermore, various modifications can be made to the invention for specific situations or materials without departing from its scope. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A voltage equalization control method for a flyback converter, characterized in that, The flyback converter includes N flyback modules, the inputs of which are connected in parallel and the outputs are connected in series, where N is a positive integer and N≧2; The voltage equalization control method for the flyback converter includes: The output voltage of each flyback module is sampled and compared with the voltage set value. Based on the comparison result, the N flyback modules are marked as either out-of-standard flyback modules or compliant flyback modules. Calculate the flyback switching cycle and conduction time of the N-channel flyback module; The conduction time of the over-standard flyback module or the conduction time of the compliant flyback module is corrected to obtain a first corrected conduction time or a second corrected conduction time. Based on the flyback switch cycle, the on-time, and the first or second corrected on-time, N flyback drive signals are generated to control the N flyback modules.

2. The voltage equalization control method for a flyback converter according to claim 1, characterized in that, The output voltage of each flyback module is sampled, and the output voltage is compared with the voltage setpoint. Based on the comparison result, the N flyback modules are respectively marked as out-of-standard flyback modules and standard flyback modules, including: Sample the output voltage of each flyback module and calculate the average output voltage of the N flyback modules; The voltage setting value is calculated based on the average output voltage and the preset threshold value; The output voltage of each flyback module is compared with the voltage setting value. Flyback modules with output voltage greater than the voltage setting value are marked as out-of-standard flyback modules, and flyback modules with output voltage less than the voltage setting value are marked as compliant flyback modules.

3. The voltage equalization control method for a flyback converter according to claim 1, characterized in that, Calculating the flyback switching cycle and conduction time of the N-channel flyback module includes: The difference between the total output voltage of the flyback converter and the voltage setpoint is input into the outer loop PI controller to obtain the PI calculation result. The PI calculation result, the input voltage of the flyback converter, and the total output voltage are input into the QR calculation unit to calculate the flyback switching cycle and conduction time of the N-channel flyback module.

4. The voltage equalization control method for a flyback converter according to claim 1, characterized in that, Correcting the conduction time of the flyback module in the out-of-standard path or the conduction time of the flyback module in the compliant path to obtain a first corrected conduction time or a second corrected conduction time includes: The conduction time of each of the out-of-standard flyback modules is corrected to obtain a first corrected conduction time, while the conduction time of any of the compliant flyback modules is not corrected; or The conduction time of each of the standard-compliant flyback modules is corrected to obtain a second corrected conduction time, while the conduction time of any of the non-standard-compliant flyback modules is not corrected.

5. The voltage equalization control method for a flyback converter according to claim 4, characterized in that, The first corrected conduction time is equal to the conduction time minus the correction amount. ; The second corrected conduction time is equal to the conduction time plus the correction amount. ; in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. represents the output voltage of the flyback module, and n represents the flyback transformer turns ratio of the flyback module.

6. The voltage equalization control method for a flyback converter according to claim 5, characterized in that, The resonance period The value is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or The resonance period Obtained through calculation: in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

7. The voltage equalization control method for a flyback converter according to any one of claims 4 to 6, characterized in that, Based on the flyback switch cycle, the on-time, and the first or second corrected on-time, N flyback drive signals are generated to control the N flyback modules, including: Based on the flyback switching period and the conduction time, an EPWM-based EPWM-based flyback drive signal is generated to control the standard-compliant flyback module, and an over-standard flyback drive signal is generated based on the flyback switching period and the first corrected conduction time to control the over-standard flyback module; or Based on the flyback switching period and the conduction time, an over-standard flyback drive signal for controlling the over-standard flyback module is generated by EPWM assignment, and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module is generated based on the flyback switching period and the second corrected conduction time.

8. A flyback converter, characterized in that, include: N-way flyback modules, wherein the inputs of the N-way flyback modules are connected in parallel and the outputs are connected in series, where N is a positive integer and N≧2; The sampling module is used to sample the output voltage of each flyback module; The marking module is used to compare the output voltage of each flyback module with the voltage set value, and mark the N flyback modules as out-of-standard flyback modules and standard flyback modules respectively based on the comparison result; The calculation module is used to calculate the flyback switching cycle and conduction time of the N-channel flyback module; The on-time correction module is used to correct the on-time of the over-standard flyback module or the on-time of the compliant flyback module to obtain a first corrected on-time or a second corrected on-time. A drive signal generation module is used to generate N flyback drive signals for controlling the N flyback modules based on the flyback switch cycle, the conduction time, and the first corrected conduction time or the second corrected conduction time.

9. The flyback converter according to claim 8, characterized in that, The conduction time correction module is used to correct the conduction time of each of the over-standard flyback modules to obtain a first corrected conduction time, and does not correct the conduction time of any of the compliant flyback modules. or The conduction time correction module is used to correct the conduction time of each of the standard-compliant flyback modules to obtain a second corrected conduction time, and does not correct the conduction time of any of the non-standard flyback modules. The first corrected conduction time is equal to the conduction time minus the correction amount. ; The second corrected conduction time is equal to the conduction time plus the correction amount. ; in, The resonant period is represented by M, which is a positive integer and M ≧ 1; ;in, This represents the input voltage of the flyback converter. The output voltage of the flyback module is represented by , and n represents the flyback transformer turns ratio of the flyback module. The resonance period The value is obtained by measuring the junction capacitance voltage of the primary-side switch of the flyback module or the resonant period of the primary-side inductor current of the flyback module; or The resonance period Obtained through calculation: in, L This represents the inductance value of the primary-side inductance of the flyback module. This represents the junction capacitance value of the primary-side switch transistor in the flyback module.

10. The flyback converter according to claim 8, characterized in that, The marking module is used to calculate the average output voltage of the N flyback modules; the voltage setting value is calculated based on the average output voltage and a preset threshold value; the output voltage of each flyback module is compared with the voltage setting value, and the flyback module whose output voltage is greater than the voltage setting value is marked as an out-of-standard flyback module, and the flyback module whose output voltage is less than the voltage setting value is marked as a compliant flyback module. The computing module includes: A voltage outer-loop PI controller is used to generate PI calculation results based on the difference between the total output voltage of the flyback converter and the voltage setpoint. The QR calculation unit is used to calculate the flyback switching cycle and conduction time of the N-channel flyback module based on the PI calculation results, the input voltage of the flyback converter, and the total output voltage. The drive signal generation module is used to generate a standard-compliant flyback drive signal for controlling the standard-compliant flyback module by EPWM assignment based on the flyback switch period and the conduction time, and an over-standard flyback drive signal for controlling the over-standard flyback module based on the flyback switch period and the first corrected conduction time; or to generate an over-standard flyback drive signal for controlling the over-standard flyback module by EPWM assignment based on the flyback switch period and the conduction time, and a standard-compliant flyback drive signal for controlling the standard-compliant flyback module based on the flyback switch period and the second corrected conduction time.

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