Wide voltage input and wide voltage output LLC direct current power supply control method and device

Abstract

The invention relates to the technical field of LLC direct-current power supplies, and discloses a wide-voltage-input and wide-voltage-output LLC direct-current power supply control method and device. The method comprises the following steps: carrying out per-unit processing on a frequency modulation and phase shift control loop and a control quantity, and adjusting the gain trends of the two to be monotonous in the same direction; frequency modulation and phase shift control are combined into a single loop, and a PI controller is shared to output control quantity; and judging a frequency modulation value and a phase shift value based on the output quantity section by section to realize smooth switching. Specifically, the frequency modulation range per unit is 1.0-2.0 (the corresponding period T is increased progressively), and the phase shift range per unit is 0.0-1.0 (the gain is increased progressively after negation adjustment); after merging, the control quantity range is 0.0-2.0, the 0.0-1.0 section is phase shift control (P = 2.0-m), and the 1.0-2.0 section is frequency modulation control (T = m); the device adopts a full-bridge LLC topology, and the output side is connected in series with a diode rectifier bridge and a resonant transformer to expand the voltage range; according to the invention, seamless connection of frequency modulation and phase shift is realized through a unified control loop, switching oscillation is avoided, wide input and wide output requirements are met, and the stability and efficiency of the system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of LLC DC power supplies, and specifically provides a control method and device for an LLC DC power supply with wide voltage input and wide voltage output. Background Art

[0002] Due to its high efficiency characteristics, the LLC resonant converter has received extensive attention in the application of isolated DC-DC power supplies. Traditional LLC topologies mostly adopt frequency modulation control strategies, adjusting the switching frequency to change the resonant cavity gain so as to adapt to different input voltages or load conditions. However, with the increasingly stringent requirements of power electronic devices for a wide input voltage range (such as in new energy power generation systems, electric vehicle charging, etc.) and a wide output voltage range (such as multi-mode power supply, compatible with different device requirements), the traditional single frequency modulation control strategy faces significant challenges. Specifically, when relying solely on frequency modulation control to achieve operation over a wide voltage range, it is necessary to design the resonant cavity parameters to cover extreme gain requirements, resulting in an increase in the volume of the resonant transformer and core losses, thereby affecting the overall efficiency and temperature rise performance.

[0003] To expand the voltage adaptation ability of LLC, phase shift control is introduced as a supplementary solution. Phase shift control adjusts the effective duty cycle by changing the conduction phase difference between the bridge arms, thereby regulating the output gain. However, existing research is mostly limited to single-sided wide voltage range applications. For example, it only supports a wide input voltage but a fixed output, or a wide output voltage but a fixed input. In such scenarios, the switching between frequency modulation and phase shift control is usually based on a preset voltage demarcation point for segmented control: fixing the frequency or phase in the low voltage section or high voltage section respectively, and dynamically adjusting the other parameter. However, when both the input and output sides need to operate over a wide voltage range, such segmented control methods are difficult to apply due to the lack of a clear demarcation point. If a dynamic switching strategy based on the deviation amount is adopted, it is easy to cause short-term distortion or oscillation of the output voltage due to the judgment delay of the control loop, seriously affecting the system stability.

[0004] Therefore, how to achieve seamless connection and smooth transition between frequency modulation and phase shift control in the scenario of wide voltage operation on both the input and output sides, and avoid voltage oscillation has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a control method and device for an LLC DC power supply with wide voltage input and wide voltage output.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A control method for an LLC DC power supply with wide voltage input and wide voltage output includes the following steps:

[0007] S1. Normalize the control quantities in the LLC frequency modulation control loop and the phase shift control loop;

[0008] S2. Adjust the frequency modulation control strategy and the phase shift control strategy to make the overall voltage gain trends of both devices monotonically in the same direction;

[0009] S3. Combine the frequency modulation control loop and the phase shift control loop into a single frequency modulation and phase shift control loop, and share the same PI controller for output control;

[0010] S4. Dynamically allocate the frequency modulation value and the phase shift value based on the output of the frequency modulation and phase shift control loop to achieve wide voltage input and output control of the LLC DC power supply.

[0011] Preferably, the per-unit processing includes the frequency modulation control quantity and the phase shift control quantity. The frequency modulation control quantity is per-unitized with the rated value of the resonant frequency as the reference, so that the frequency modulation range is mapped to 0.5 - 1.0, and the phase shift control quantity is per-unitized with the initial phase shift angle as the reference, so that the phase shift range is mapped to 1.0 - 2.0.

[0012] Preferably, when adjusting the frequency modulation control strategy, associate the period value T of the frequency modulation control with the monotonically increasing characteristic of the gain, so that the per-unitized control quantity range is adjusted from 0.5 - 1.0 to 1.0 - 2.0; when adjusting the phase shift control strategy, invert the phase shift control quantity and re-per-unitize it, so that the monotonically increasing gain range corresponds to -2.0 to -1.0.

[0013] Preferably, the combination of the control loops includes:

[0014] Adjust the phase shift control quantity to 0.0 - 1.0 through an offset to seamlessly connect with the 1.0 - 2.0 of the frequency modulation control quantity, forming a total control range of 0.0 - 2.0;

[0015] Based on the output of the PI controller, preferentially increase the gain through phase shift control within the range of 0.0 - 1.0, and switch to frequency modulation control to further increase the gain after exceeding 1.0.

[0016] Preferably, the steps of dynamically allocating the frequency modulation value and the phase shift value include:

[0017] When the control loop output is within 0.0 - 1.0, convert it to the per-unit phase shift value of 1.0 - 2.0 through the formula P = 2.0 - m;

[0018] When the control loop output is within 1.0 - 2.0, directly map it to the per-unit frequency modulation value of 1.0 - 2.0;

[0019] Restore the per-unit value to the actual frequency modulation frequency and phase shift angle to drive the LLC DC power supply device.

[0020] A wide voltage input and wide voltage output LLC DC power supply control device includes:

[0021] Full-bridge LLC topology, with two series-connected diode rectifier bridges on the output side to increase the output voltage level;

[0022] Two sets of series-resonant transformers corresponding to the diode rectifier bridges, used to reduce the power requirement of a single transformer;

[0023] Input-side filter inductor, used to suppress high-frequency current interference.

[0024] Preferably, the series configuration of the diode rectifier bridges includes:

[0025] The DC output terminals of the first rectifier bridge and the second rectifier bridge are connected in series, and the total output voltage is the sum of the two;

[0026] The breakdown voltage of the diodes in each rectifier bridge is half of the total output voltage, reducing device stress.

[0027] Preferably, the series configuration of the resonant transformers includes:

[0028] The primary windings of the first transformer and the second transformer are connected in series to the full-bridge circuit, and the secondary windings are connected in series;

[0029] The core parameters of each transformer are independently designed according to the power level to optimize volume and efficiency.

[0030] Preferably, the design parameters of the input-side filter inductor satisfy:

[0031] The inductance value is dynamically adjusted according to the input voltage fluctuation range to ensure that the high-frequency ripple suppression rate is greater than 90%;

[0032] The inductor material is selected as high-frequency low-loss ferrite to reduce temperature rise and hysteresis loss.

[0033] Preferably, the parameters of the PI controller are dynamically adjusted according to the real-time changes of the input and output voltages, specifically including:

[0034] When the input voltage fluctuation exceeds ±20%, increase the proportional coefficient to accelerate the response speed;

[0035] When the output voltage approaches the target value, switch to the integral-dominant mode to eliminate the steady-state error.

[0036] The present invention provides a control method for a wide-voltage-input and wide-voltage-output LLC DC power supply, which has the following beneficial effects compared with the prior art:

[0037] The present invention can ensure that the LLC frequency modulation and phase shift hybrid control is no longer limited to a wide voltage range on one side, that is, a wide voltage range on the input side but a fixed value on the output side, or a wide voltage range on the output side but a fixed value on the input side. It does not require a rigid switching of the frequency modulation and phase shift control based on the voltage value as a judgment criterion. Instead, it is suitable for the application scenario where both the input side and the output side of the LLC are in a wide voltage range. According to the self-regulation of the combined control loop, it can ensure a smooth transition and seamless connection when switching between the frequency modulation control strategy and the phase shift control strategy, without judgment delay, and can avoid the problem of DC voltage oscillation. Description of the Drawings

[0038] Figure 1 It is a block diagram of the control method for a wide-voltage-input and wide-voltage-output LLC DC power supply;

[0039] Figure 2 It is a combined diagram of frequency modulation and phase shift control;

[0040] Figure 3 It is a flowchart for restoring and calculating the frequency modulation value and the phase shift value;

[0041] Figure 4 It is a topology diagram of a wide-voltage-input and wide-voltage-output LLC DC power supply device;

[0042] Figure 5 It is a frequency modulation gain curve diagram of LLC;

[0043] Figure 6 It is a phase shift gain curve diagram of LLC;

[0044] Figure 7 It is a simulation waveform diagram of LLC frequency modulation and phase shift control. Detailed Embodiment

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Please refer to Figures 1-7 , this application provides a control method for a wide-voltage-input and wide-voltage-output LLC DC power supply, including the following steps:

[0047] S1. Perform per-unit processing on the control quantities in the LLC frequency modulation control loop and the phase shift control loop;

[0048] S2. Adjust the frequency modulation control strategy and the phase shift control strategy to make the overall voltage gain trends of the two devices monotonically in the same direction;

[0049] S3. Combine the frequency modulation control loop and the phase shift control loop into a single frequency modulation and phase shift control loop, and share the same PI controller for output control;

[0050] S4. Dynamically allocate the frequency modulation value and the phase shift value based on the output of the frequency modulation and phase shift control loop to achieve wide voltage input and output control of the LLC DC power supply.

[0051] As Figure 1 shown: The wide voltage input and wide voltage output LLC DC power supply control method includes: The first step is to normalize the LLC frequency modulation and phase shift control loops and the control quantities; The second step is to adjust the LLC frequency modulation control strategy and the phase shift control strategy to ensure that the overall voltage gain trend of the device implemented by the two control strategies is monotonically in the same direction; The third step is to combine the LLC frequency modulation control and the phase shift control into a single frequency modulation and phase shift control loop, and share the same PI controller for control output; The fourth step is to judge the final frequency modulation value and phase shift value based on the control output of the combined frequency modulation and phase shift control loop to achieve the control of the LLC DC power supply device.

[0052] As Figure 2 shown, during the combination of frequency modulation and phase shift control, it is necessary to first normalize the LLC control loop and the control quantities. For the per-unit method of the frequency modulation value, assuming that the LLC resonance frequency F is 100K and the frequency modulation range is 50K - 100K, so the frequency modulation range F is 0.5 - 1.0 after normalizing the control signal with 100K as the reference; For the per-unit method of the phase shift value, considering the actual implementation method of phase shift control, with the S1 phase as the reference and adjusting the phase shift angle through S3 to achieve phase shift control, the initial phase shift value of S3 is 180 degrees, so its phase shift range P is 180 degrees - 360 degrees, so the phase shift range P is 1.0 - 2.0 after normalizing the control signal with 180 degrees.

[0053] After the per-unit values of frequency modulation and phase shift control are completed, it is necessary to adjust the LLC frequency modulation control strategy and the phase shift control strategy to ensure that the overall voltage gain trend of the device implemented by the two control strategies is monotonically in the same direction. Considering the actual implemented control architecture, the control chip realizes dynamic frequency modulation control by adjusting the count value when constructing the carrier wave. Different count values actually reflect different period values. Therefore, at this time, the direct control of LLC frequency modulation actually shows as adjusting the period size T. At this time, the gain of the LLC device also changes from the decreasing characteristic of decreasing with the increase of F to the increasing characteristic of increasing with the increase of T. Since the LLC period value is the reciprocal of the frequency value T = 1 / F, the per-unit value range of the control quantity output by the controller changes from 0.5 - 1.0 to 1.0 - 2.0, and when changing from 1.0 to 2.0, the gain of the LLC device increases monotonically; to ensure that the phase shift control has the same gain monotonicity as the modified frequency modulation control, it is necessary to invert the phase shift control loop H = -P, that is, the per-unit value range of the control quantity output by the controller changes from 1.0 - 2.0 to -1.0~-2.0. At this time, the gain of the LLC device also changes from the decreasing characteristic of decreasing with the increase of P to the increasing characteristic of increasing with the increase of H, that is, when changing from -2.0 to -1.0, the gain of the LLC device increases monotonically.

[0054] Further, the merging of the control loops includes:

[0055] Adjust the phase shift control quantity to 0.0 - 1.0 through an offset, seamlessly connect it with the 1.0 - 2.0 of the frequency modulation control quantity, and form a total control range of 0.0 - 2.0;

[0056] Based on the output quantity of the PI controller, the gain is preferentially increased through phase shift control within the range of 0.0 - 1.0, and when it exceeds 1.0, it switches to frequency modulation control to further increase the gain.

[0057] Further, the steps of dynamically allocating the frequency modulation value and the phase shift value include:

[0058] When the output quantity of the control loop is within 0.0 - 1.0, it is converted into the per-unit value of phase shift 1.0 - 2.0 through the formula P = 2.0−m;

[0059] When the output quantity of the control loop is within 1.0 - 2.0, it is directly mapped to the per-unit value of frequency modulation 1.0 - 2.0;

[0060] Restore the per-unit value to the actual frequency modulation frequency and phase shift angle, and drive the LLC DC power supply device.

[0061] After the adjusted FM control and phase-shift control gains become monotonically the same, the LLC FM control and phase-shift control loops can be combined to form a single FM phase-shift control loop, sharing the same PI controller for control output. When T varies from 1.0 to 2.0 under FM control, the LLC device gain increases monotonically, but the gain values within this range are not zero. When H varies from -2.0 to -1.0 under phase-shift control, the LLC device gain increases monotonically, and the gain values start from zero. Considering that the adjustment process of the PI controller also starts from zero and then gradually changes, it is necessary to transform the output of the phase-shift control loop to ensure that the FM phase-shift control loop first performs phase-shift control and then FM control during the establishment process. The output of the phase-shift control loop is adjusted to H + 2.0, and the per-unit value changes from -2.0~-1.0 to 0.0 - 1.0, which exactly connects with the FM control quantity range of 1.0 - 2.0, forming a total FM phase-shift control range of 0.0 - 2.0, achieving an increase in the LLC device gain starting from zero. The LLC device gain adjustment process is as follows: first, increase the overall gain through phase-shift control. If the gain is insufficient, the closed-loop control output automatically transitions from 0.0 - 1.0 to 1.0 - 2.0 for FM control to increase the overall device gain again until the control target is reached.

[0062] A wide-voltage-input and wide-voltage-output LLC DC power control device includes:

[0063] A full-bridge LLC topology structure, whose output side uses two series-connected diode rectifier bridges to increase the output voltage level;

[0064] Two groups of series-resonant transformers corresponding to the diode rectifier bridges, used to reduce the power requirement of a single transformer;

[0065] An input-side filter inductor, used to suppress high-frequency current interference.

[0066] Furthermore, the series configuration of the diode rectifier bridges includes:

[0067] The DC output terminals of the first rectifier bridge and the second rectifier bridge are connected in series, and the total output voltage is the sum of the two;

[0068] The breakdown voltage of the diodes in each rectifier bridge is half of the total output voltage, reducing the device stress.

[0069] Furthermore, the series configuration of the resonant transformers includes:

[0070] The primary windings of the first transformer and the second transformer are connected in series to the full-bridge circuit, and the secondary windings are connected in series;

[0071] The core parameters of each transformer are independently designed according to the power level to optimize the volume and efficiency.

[0072] Furthermore, the design parameters of the input-side filter inductor satisfy:

[0073] The inductance value is dynamically adjusted according to the input voltage fluctuation range to ensure that the high-frequency ripple suppression rate is greater than 90%;

[0074] The inductor material is selected as high-frequency low-loss ferrite to reduce temperature rise and hysteresis loss.

[0075] Furthermore, the parameters of the PI controller are dynamically adjusted according to the real-time changes of the input and output voltages, specifically including:

[0076] When the input voltage fluctuation exceeds ±20%, increase the proportional coefficient to accelerate the response speed;

[0077] When the output voltage approaches the target value, switch to the integral-dominant mode to eliminate the steady-state error.

[0078] As Figure 3 shown, the output of the frequency modulation and phase shift control loop is only one control quantity of 0.0 - 2.0, but the actual control parameters include two, namely the frequency modulation value T and the phase shift value P. Therefore, it is necessary to distinguish and process them to facilitate the realization of the final control. For the frequency modulation and phase shift control range of 0.0 - 1.0, it is actually the phase shift range. When it is judged that the controller output is less than 1.0, the original phase shift per-unit value P can be adjusted to the range of 1.0 - 2.0 through the formula 2.0 - m; for the frequency modulation and phase shift control range of 1.0 - 2.0, it is actually the frequency modulation range. When it is judged that the controller output is greater than 1.0, the control quantity remains unchanged and can correspond to the original frequency modulation per-unit value T in the range of 1.0 - 2.0; based on the obtained per-unit values of the frequency modulation value T and the phase shift value P, the actual control of the LLC DC power supply device is finally realized by restoring them to the final actual values of frequency modulation and phase shift.

[0079] As Figure 4 shown, the LLC DC power supply device adopts a classic full-bridge LLC topology. The difference is that to meet the requirement of the overall wide voltage output range of the device, the diode rectifier bridge on the output side of the device adopts a series connection of two to increase the overall output voltage level of the device. The series connection of two diode rectifier bridges is also beneficial to the device selection design and reduces the withstand voltage stress of the diodes; its corresponding resonant transformer also consists of two in series. On the one hand, it corresponds to the diode rectifier bridge, and on the other hand, it can reduce the power level of a single resonant transformer and facilitate the design of the resonant transformer itself; a filter inductor is added to the input side of the LLC DC power supply device to filter the high-frequency current waveform and prevent causing greater interference to external devices.

[0080] As Figure 5 shown, when adopting the wide voltage input and wide voltage output LLC control strategy, control the LLC to operate in the under-frequency band of the AB segment of the frequency modulation gain curve, and the overall gain of the LLC device decreases as the switching frequency F increases.

[0081] As Figure 6 shown, when adopting the wide - voltage input and wide - voltage output LLC control strategy, when the LLC operates in the phase - shift section, the overall gain of the LLC device decreases as the phase - shift value P increases.

[0082] As Figure 7 shown, after the LLC goes through the soft - start process, since the target value of the device gain is greater than 1.0, it is necessary to operate in the frequency - modulation working area to increase the gain. At this time, the output value of the frequency - modulation phase - shift control loop is greater than 1.0, and the whole device operates in the frequency - modulation working area. The frequency - modulation value T during operation is in the range of 1.0 - 2.0, and the phase - shift value P is always kept at 1.0 during frequency - modulation operation, that is, no phase - shift is performed, and finally the device operates stably; when changing the target value of the LLC device, since the target value of the device gain is less than 1.0, it is necessary to operate in the phase - shift working area to reduce the gain. At this time, the output value of the frequency - modulation phase - shift control loop is less than 1.0, and the whole device operates in the phase - shift working area. The phase - shift value P during operation is in the range of 1.0 - 2.0, and the frequency - modulation value T is always kept at 1.0 during phase - shift operation, that is, it operates at the resonant frequency, and finally the device operates stably.

[0083] Some of the data in the above formula are numerically calculated after removing the dimensions, and the content not described in detail in this specification belongs to the prior art well - known to those skilled in the art.

[0084] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified and equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A wide-voltage-input and wide-voltage-output LLC DC power supply control method, characterized in that It includes the following steps: S1. Normalize the control variables in the LLC frequency modulation control loop and the phase shift control loop; S2. Adjust the frequency modulation control strategy and the phase shift control strategy to make the overall voltage gain trends of the two devices monotonically in the same direction; S3. Combine the frequency modulation control loop and the phase shift control loop into a single frequency modulation phase shift control loop and share the same PI controller for output control; S4. Dynamically allocate the frequency modulation value and the phase shift value based on the output of the frequency modulation phase shift control loop to achieve wide voltage input and output control of the LLC DC power supply.

2. The wide-voltage-input and wide-voltage-output LLC DC power supply control method according to claim 1, wherein The normalization process includes the frequency modulation control variable and the phase shift control variable. The frequency modulation control variable is normalized with the rated value of the resonant frequency as the reference, so that the frequency modulation range is mapped to 0.5 - 1.

0. The phase shift control variable is normalized with the initial phase shift angle as the reference, so that the phase shift range is mapped to 1.0 - 2.

0.

3. A wide-voltage input and wide-voltage output LLC DC power supply control method according to claim 2, characterized in that When adjusting the frequency modulation control strategy, associate the period value T of the frequency modulation control with the monotonically increasing characteristic of the gain, so that the range of the normalized control variable is adjusted from 0.5 - 1.0 to 1.0 - 2.

0. When adjusting the phase shift control strategy, take the inverse of the phase shift control variable and re-normalize it, so that the monotonically increasing range of its gain corresponds to -2.0 to -1.

0.

4. A wide-voltage-input and wide-voltage-output LLC DC power supply control method according to claim 3, characterized in that, The combination of the control loops includes: Adjust the phase shift control variable to 0.0 - 1.0 through an offset to seamlessly connect with the 1.0 - 2.0 of the frequency modulation control variable, forming a total control range of 0.0 - 2.0; Based on the output of the PI controller, preferentially increase the gain through phase shift control within the range of 0.0 - 1.0, and switch to frequency modulation control to further increase the gain after exceeding 1.

0.

5. A wide-voltage-input and wide-voltage-output LLC DC power supply control method according to claim 1, characterized in that, The steps of dynamically allocating the frequency modulation value and the phase shift value include: When the control loop output is within 0.0 - 1.0, convert it to the phase shift per-unit value of 1.0 - 2.0 through the formula P = 2.0 - m; When the control loop output is within 1.0 - 2.0, directly map it to the frequency modulation per-unit value of 1.0 - 2.0; Restore the per-unit value to the actual frequency modulation frequency and phase shift angle to drive the LLC DC power supply device.

6. A wide-voltage-input and wide-voltage-output LLC DC power supply control device, characterized in that, It includes: A full-bridge LLC topology structure, and two series-connected diode rectifier bridges are adopted on the output side to increase the output voltage level; Two groups of series-resonant transformers corresponding to the diode rectifier bridges are used to reduce the power requirement of a single transformer; An input-side filter inductor is used to suppress high-frequency current interference.

7. A wide-voltage-input and wide-voltage-output LLC DC power supply control device according to claim 6, characterized in that, The series configuration of the diode rectifier bridge includes: The DC output terminals of the first rectifier bridge and the second rectifier bridge are connected in series, and the total output voltage is the sum of the two; The withstand voltage value of the diodes of each rectifier bridge is half of the total output voltage, reducing the device stress.

8. A wide-voltage-input and wide-voltage-output LLC DC power supply control device according to claim 6, characterized in that, The series configuration of the resonant transformer includes: The primary windings of the first transformer and the second transformer are connected in series to the full-bridge circuit, and the secondary windings are connected in series; The core parameters of each transformer are independently designed according to the power level to optimize the volume and efficiency.

9. A wide-voltage-input and wide-voltage-output LLC DC power supply control device according to claim 6, characterized in that The design parameters of the input-side filter inductor satisfy: The inductance value is dynamically adjusted according to the input voltage fluctuation range to ensure that the high-frequency ripple suppression rate is greater than 90%; The inductance material is selected as high-frequency low-loss ferrite to reduce the temperature rise and hysteresis loss.

10. A wide - voltage input and wide - voltage output LLC DC power supply control method according to any one of claims 1 - 5, characterized in that, The parameters of the PI controller are dynamically adjusted according to the real-time changes of the input and output voltages, specifically including: When the input voltage fluctuation exceeds ±20%, increase the proportional coefficient to accelerate the response speed; When the output voltage approaches the target value, switch to the integral-dominant mode to eliminate the steady-state error.

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