A digital control method and device for LLC power supply

Abstract

This invention discloses a digital control method and apparatus for an LLC power supply. In one specific embodiment, the method includes generating symmetrical PFM waveforms with paired waveforms and consistent widths using a symmetrical PFM waveform generation strategy; limiting the frequency and dead time of the symmetrical PFM waveforms using a variable dead-time frequency-limiting soft-start control strategy, and adjusting the given voltage during the soft-start process; and performing closed-loop regulation of the LLC power supply using a constant voltage and current-limiting PI fast switching control strategy. This embodiment enables soft-start under high input-output voltage difference, constant voltage and constant current fast switching, and limited-number self-recovery protection for the LLC power supply.

Description

Technical Field

[0001] This invention relates to the field of digital power supply control. More specifically, it relates to a digital control method and apparatus for an LLC power supply. Background Technology

[0002] To improve the power density of DC / DC power supplies, it is usually necessary to increase the switching frequency. However, increasing the switching frequency leads to increased switching losses. Series / parallel resonant circuits can typically be used to reduce these losses. LLC power supplies are modified from traditional LC resonant converters by adding an inductor in parallel, combining the advantages of both series and parallel resonant converters. They feature low output switching losses, a wide voltage regulation range, and zero-voltage turn-on across the entire load range. Furthermore, compared to traditional power supplies that use pulse width modulation (PWM) control, LLC power supplies generally employ pulse frequency modulation (PFM) control. Their drive signal is a symmetrical square wave with a duty cycle close to 0.5, and closed-loop control is achieved by adjusting the switching frequency.

[0003] In the past, most DC / DC power supplies used analog control methods. However, analog controllers are complex in structure and difficult to implement complex control algorithms. In contrast, digital power supplies controlled by digital signal processors have the advantages of programmability and strong anti-interference capabilities, and are gradually becoming the mainstream.

[0004] For conventional LLC power supply analog controllers, their PFM generation method cannot guarantee that the drive signals appear in pairs, or that the width of the same pair of drive signals is inconsistent, which may lead to magnetization when the frequency changes rapidly; the switching method of their voltage loop and current loop is usually to take the maximum / minimum value of the output of two PID controllers, and the integral part in the PID controller will slow down the switching speed of the two loops; the controller usually uses a frequency limiting method for soft start-up during startup, which can easily cause a large current surge when the input voltage is high and the output voltage is low; the controller's protection logic is usually set to self-recovery, and when a fault occurs, it will repeatedly restart, which can easily lead to power supply damage.

[0005] Therefore, there is an urgent need to propose a digital control method and device for LLC power supplies to achieve soft start-up under high input-output voltage difference, fast switching between constant voltage and constant current, and self-recovery protection with a limited number of cycles. Summary of the Invention

[0006] The purpose of this invention is to provide a digital control method and apparatus for LLC power supplies to solve at least one of the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of this invention provides a digital control method for an LLC power supply, the method comprising:

[0009] Using a symmetrical PFM waveform generation strategy, symmetrical PFM waveforms with waveform pairs appearing and the same pair of waveforms having the same width are generated.

[0010] The frequency and dead time of the symmetrical PFM waveform are limited by a variable dead-time frequency limiting soft-start control strategy, and the given voltage is adjusted during the soft-start process.

[0011] A constant voltage and current limiting PI fast switching control strategy is used to perform closed-loop regulation of the LLC power supply.

[0012] Optionally, the method further includes

[0013] Using a limited-number self-recovery protection control strategy, the LLC power supply is judged to have a fault based on voltage and current sampling, and the number of faults is recorded.

[0014] If the number of failures is less than the set value, the LLC power output is turned off and a soft start is performed again after a delay.

[0015] Optionally, the variable dead-time frequency limiting soft-start control strategy includes:

[0016] The given voltage is linearly adjusted according to the given voltage regulation law, and remains unchanged after being adjusted to the rated voltage.

[0017] Optionally, the symmetrical PFM waveform generation strategy includes

[0018] The counter is set to operate in increment / decrement counting mode, and the symmetrical PFM waveform is flipped when the count reaches 0 and the periodic count value, respectively.

[0019] Optionally, the symmetrical PFM waveform generation strategy further includes

[0020] The switching frequency is adjusted by modifying the cycle count value, and the dead time is obtained by delaying the rising edge.

[0021] Optionally, the constant voltage current limiting PI fast switching control strategy includes:

[0022] Whether to enter the current loop is determined by whether the current sampling exceeds the rated current;

[0023] If the current sample exceeds the rated current, the output current of the LLC power supply is controlled to the rated current.

[0024] Optionally, the constant voltage current limiting PI fast switching control strategy further includes:

[0025] If the current sample does not exceed the rated current, then a judgment is made based on the voltage sample.

[0026] If the voltage sampling does not exceed the rated voltage, the LLC power supply outputs the rated current and increases the output voltage.

[0027] Optionally, the constant voltage current limiting PI fast switching control strategy further includes:

[0028] Whether to enter the voltage loop is determined based on whether the voltage sampling exceeds the rated voltage;

[0029] If the voltage sample exceeds the rated voltage, the output voltage of the LLC power supply will be controlled to the rated voltage.

[0030] Optionally, the adjustment formula for closed-loop regulation of the LLC power supply is as follows:

[0031] U(n) = U(n-1) + det[U(n)]

[0032] Where U(n) is the constant voltage and current limiting PI fast switching control signal sampled for the nth time, U(n-1) is the constant voltage and current limiting PI fast switching control signal sampled for the (n-1)th time, and det[U(n)] is the control signal related to the error;

[0033] When in the voltage loop

[0034] det[U(n)]=K P-U *-E U (n)-E U [(n-1)]+K I-U *E U (n)

[0035] Among them, K P-U K is the voltage loop proportionality coefficient. I-U E is the voltage loop integral coefficient. U (n) represents the voltage loop error, E U (n) represents the rated voltage minus the voltage sample;

[0036] When in a current loop

[0037] det[U(n)]=K P-I *[E I (n)-E I [(n-1)]+K I-I *E I (n)

[0038] Among them, K P-I K is the proportionality coefficient of the current loop. I-I E is the integral coefficient of the current loop.I (n) represents the current loop error, E I (n) is the rated current minus the current sample.

[0039] A second aspect of the present invention provides a digital control device for an LLC power supply, the device comprising:

[0040] The limited-use self-recovery protection control unit is used to determine whether the LLC power supply has a fault based on voltage and current sampling.

[0041] The symmetrical PFM waveform generation unit is used to generate symmetrical PFM waveforms in which waveform pairs appear and the width of the same pair of waveforms is consistent.

[0042] A variable dead-time frequency limiting soft-start control unit is used to limit the frequency and dead time of the symmetrical PFM waveform, and to adjust the given voltage during the soft-start process;

[0043] The constant voltage and current limiting PI fast switching control unit is used for closed-loop regulation of LLC power supply.

[0044] The beneficial effects of this invention are as follows:

[0045] This invention discloses a digital control method for LLC power supplies, which can realize soft start-up with high input-output voltage difference, fast switching between constant voltage and constant current, and self-recovery protection with a limited number of cycles. Attached Figure Description

[0046] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0047] Figure 1 A flowchart of a digital control method for an LLC power supply provided in an embodiment of the present invention is shown.

[0048] Figure 2 The flowchart of the limited-use self-recovery protection control strategy provided in the embodiment of the present invention is shown.

[0049] Figure 3 This diagram illustrates a variable dead-time frequency limiting soft-start control strategy provided in an embodiment of the present invention.

[0050] Figure 4 A schematic diagram of the symmetrical PFM waveform generation strategy provided in an embodiment of the present invention is shown.

[0051] Figure 5 The flowchart of the constant voltage current limiting PI fast switching control strategy provided in the embodiment of the present invention is shown.

[0052] Figure 6 A schematic diagram of the structure of the digital control device for an LLC power supply provided in an embodiment of the present invention is shown. Detailed Implementation

[0053] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0054] For existing LLC power supply analog controllers, their PFM generation methods cannot guarantee that drive signals appear in pairs, or that the widths of the same pair of drive signals are inconsistent, which may lead to magnetization when the frequency changes rapidly. The switching method for their voltage and current loops typically involves taking the maximum / minimum values ​​of the outputs of two PID controllers, and the integral element in the PID controller slows down the switching speed of the two loops. During controller startup, a frequency-limiting method is usually used for soft start-up, which can easily cause large current surges when the input voltage is high and the output voltage is low. The controller's protection logic is usually set to self-recovery, and when a fault occurs, it will repeatedly restart, which can easily damage the power supply. Therefore, there is an urgent need to propose a digital control method and device for LLC power supplies to achieve soft start-up under high input-output voltage difference, rapid switching between constant voltage and constant current, and limited-number self-recovery protection.

[0055] In view of this, one embodiment of the present invention provides a digital control method for an LLC power supply. The method includes generating a symmetrical PFM waveform with waveform pairs appearing and the same width of the same pair of waveforms using a symmetrical PFM waveform generation strategy; limiting the frequency and dead time of the symmetrical PFM waveform using a variable dead-time frequency limiting soft-start control strategy, and adjusting the given voltage during the soft-start process; and performing closed-loop regulation of the LLC power supply using a constant voltage current limiting PI fast switching control strategy.

[0056] In one possible implementation, the method further includes using a limited-number self-recovery protection control strategy to determine whether the LLC power supply has failed based on voltage and current sampling, and to record the number of failures.

[0057] If the number of failures is less than the set value, the LLC power output is turned off and a soft start is performed again after a delay.

[0058] Specifically, such as Figure 1The diagram shows a flowchart of a digital control method for an LLC power supply provided in an embodiment of the present invention. This embodiment discloses a digital control method for an LLC power supply, which includes a symmetrical PFM waveform generation strategy, a constant voltage and current limiting PI fast switching control strategy, a variable dead-zone frequency limiting soft-start control strategy, and a limited-number self-recovery protection control strategy. Voltage and current samples are obtained by sampling the output voltage and current. The output voltage and current samples are used to determine whether there is an output fault through the limited-number self-recovery protection control strategy. If a fault occurs and the number of faults is less than a set value, the power supply is restarted using the variable dead-zone frequency limiting soft-start control strategy. The variable dead-zone frequency limiting soft-start control strategy limits the frequency and dead zone of the generated symmetrical PFM waveform by limiting the minimum output frequency and minimum dead zone allowed by the symmetrical PFM waveform generation strategy. Simultaneously, during the soft-start process, the given voltage is adjusted so that the given voltage starts softly according to a given curve. During the operation of the LLC power supply, closed-loop regulation is performed using the constant voltage and current limiting PI fast switching control strategy.

[0059] Furthermore, such as Figure 2 The diagram shows a flowchart of the limited-number self-recovery protection control strategy provided in an embodiment of the present invention. This strategy first determines whether a fault exists based on whether the voltage and current samples exceed the fault warning value; if no fault exists, normal closed-loop control is performed; if a fault occurs, the number of faults is then assessed; if the number of faults exceeds a certain threshold, all outputs are locked and shut down; if the number of faults is less than the set value, the number of faults is recorded, the outputs are shut down for a period of time, and then a soft restart is performed.

[0060] In one possible implementation, the variable dead-zone frequency limiting soft-start control strategy includes linearly adjusting the given voltage according to a given voltage regulation law, adjusting it to the rated voltage and then keeping it unchanged.

[0061] Specifically, such as Figure 3 The diagram illustrates a variable dead-time frequency-limiting soft-start control strategy provided in an embodiment of the present invention. During the soft-start process, this strategy linearly increases the output closed-loop regulation voltage according to a pre-set voltage regulation law, and then maintains it at the rated voltage. During the voltage increase, the dead-time and minimum frequency limits also linearly decrease from their maximum values ​​to their minimum values ​​during normal operation. This variable dead-time frequency-limiting soft-start control strategy effectively limits current surges during startup.

[0062] In one possible implementation, the symmetrical PFM waveform generation strategy includes operating a counter in increment / decrement counting mode, wherein the symmetrical PFM waveform is flipped when the count reaches 0 and when the period count value is reached, respectively.

[0063] In one possible implementation, the symmetrical PFM waveform generation strategy further includes adjusting the switching frequency by modifying the period count value and obtaining the dead time by delaying the rising edge.

[0064] Specifically, such as Figure 4 The diagram illustrates a symmetrical PFM waveform generation strategy provided in an embodiment of the present invention. This strategy operates the counter in an "increment-decrement" counting mode, meaning the counter first increments from 0 to the period count value N, then decrements from N back to 0, and so on. The symmetrical PFM waveform flips when the count reaches 0 and the period count value N, respectively. The switching frequency can be adjusted by modifying the period count value N. The dead time is obtained by delaying the rising edge. When the period count value N changes, it ensures that the waveforms always appear in pairs, and the width of the same pair of driving waveforms is consistent.

[0065] In one possible implementation, the constant voltage and current limiting PI fast switching control strategy includes determining whether to enter the current loop based on whether the current sample exceeds the rated current; if the current sample exceeds the rated current, then controlling the output current of the LLC power supply to the rated current.

[0066] In one possible implementation, the constant voltage and current limiting PI fast switching control strategy further includes: if the current sampling does not exceed the rated current, then making a judgment based on the voltage sampling; if the voltage sampling does not exceed the rated voltage, then controlling the LLC power supply to output the rated current and increasing the output voltage.

[0067] In one possible implementation, the constant voltage and current limiting PI fast switching control strategy further includes determining whether to enter the voltage loop based on whether the voltage sample exceeds the rated voltage; if the voltage sample exceeds the rated voltage, then controlling the output voltage of the LLC power supply to the rated voltage.

[0068] Specifically, such as Figure 5 The diagram shows a flowchart of the constant voltage and current limiting PI fast switching control strategy provided in an embodiment of the present invention. If the current sample exceeds the limited rated current, then regardless of the output voltage, the output current is controlled at the limited rated current as the adjustment target, and current loop regulation is performed; if the current sample does not exceed the limited rated current, but the voltage sample exceeds the rated voltage, then the output voltage is controlled at the rated voltage as the adjustment target, and voltage loop regulation is performed; if the current sample does not exceed the limited rated current, and the voltage sample does not exceed the rated voltage, then the system state at the previous moment determines whether to use current or voltage as the adjustment target, and closed-loop regulation is performed.

[0069] The constant voltage and current limiting PI fast switching control strategy works as follows: when the power supply suddenly carries a load exceeding the rated load, the system will output at a limited rated current, and the output voltage will drop below the rated voltage, with the system operating in a current closed loop. Once the load is less than the rated load, since the output voltage is less than the rated voltage, the power supply still uses current as the regulation target, increasing the output voltage at the "fastest permissible speed" (limited rated current). After a period of time (when the output voltage rises to the rated voltage), once the output voltage slightly exceeds the rated voltage, the system switches to voltage closed-loop control mode to control the output voltage back to the rated voltage.

[0070] In one possible implementation, the regulation formula for closed-loop regulation of the LLC power supply is:

[0071] U(n) = U(n-1) + det[U(n)]

[0072] Where U(n) is the constant voltage and current limiting PI fast switching control signal sampled for the nth time, U(n-1) is the constant voltage and current limiting PI fast switching control signal sampled for the (n-1)th time, and det[U(n)] is the control signal related to the error;

[0073] When in the voltage loop

[0074] det[U(n)]=K P-U *[E U (n)-E U [(n-1)]+K I-U *E U (n)

[0075] Among them, K P-U K is the voltage loop proportionality coefficient. I-U E is the voltage loop integral coefficient. U (n) represents the voltage loop error, E U (n) represents the rated voltage minus the voltage sample;

[0076] When in a current loop

[0077] det[U(n)]=K P-I *[E I (n)-E I [(n-1)]+K I-I *E I (n)

[0078] Among them, K P-I K is the proportionality coefficient of the current loop. I-I E is the integral coefficient of the current loop. I (n) represents the current loop error, E I (n) is the rated current minus the current sample.

[0079] Specifically, the voltage and current loops are typically closed-loop using PI controllers. A typical PI controller expression is:

[0080] U=K p *E+K i *∑E

[0081] Where U is the controller output, E is the error, and K is the error. p K is the proportionality coefficient. i is the integral coefficient.

[0082] For digital controllers, the differential form of a PI controller is typically used as follows:

[0083]

[0084] That is

[0085] U(n)-U(n-1)=K p *[E(n)-E(n-1)]+K i *E(n)

[0086] Where n is the nth sample value and n-1 is the previous sample value.

[0087] For conventional voltage loop and current loop switching algorithms, two PI regulators are typically constructed to generate two PI controller outputs U. I (n) and U U (n), switching is achieved by taking the maximum or minimum value of the outputs of the two controllers. However, in such a switching method, due to the integral coefficient K... i The effect of this is that U(n) requires integration over a period of time to complete.

[0088] For traditional U I (n) and U U (n) This problem involves two controllers operating simultaneously, requiring a period of integration to determine the maximum or minimum value as the final output. This embodiment switches between voltage and current sampling based on the methods of voltage exceeding rated voltage and current exceeding rated current. Specifically, the output stages of the two controllers are merged, extracting U(n)-U(n-1) from the two different controllers and combining them as a common part; the error-related stages in the two different controllers are denoted as det[U(n)].

[0089] U(n) = U(n-1) + det[U(n)]

[0090] When in the voltage loop, det[U(n)] = K P-U *[E U (n)-E U[(n-1)]+K I-U *E U (n);

[0091] Among them, K P-U K is the voltage loop proportionality coefficient. I-U E is the voltage loop integral coefficient. U (n) represents the voltage loop error.

[0092] When in a current loop, det[U(n)] = K P-I *[E I (n)-E I [(n-1)]+K I-I *E I (n);

[0093] Among them, K P-I K is the proportionality coefficient of the current loop. I-I E is the integral coefficient of the current loop. I (n) represents the current loop error.

[0094] In this embodiment of dual-loop control (voltage loop and current loop), voltage and current samples are corrected and converted into actual voltage and current sample values, respectively. The voltage loop error E is... U (n) is the rated voltage 700V minus the actual voltage sampling, and the voltage loop proportionality coefficient K. P-U The voltage loop integral coefficient K is 0.05. I-U =0.00005; current loop error E I (n) is the rated output current 29A minus the actual voltage sampling, and the current loop proportionality coefficient K. P-I The integral coefficient K of the current loop is 0.1. I-I The value is 0.001, and the controller output U(n) is the value of the period register TBPRD.

[0095] In this embodiment, the switching judgment condition is voltage sampling and current sampling, which can realize the fusion of two PI regulators and improve the switching speed of the regulators; and realize the fast switching of two PI regulators without being affected by the integral link.

[0096] This embodiment discloses a digital control method for LLC power supplies, which can realize soft start-up with high input-output voltage difference, fast switching between constant voltage and constant current, and self-recovery protection with a limited number of cycles for LLC power supplies.

[0097] Another embodiment of the present invention provides a digital control device for an LLC power supply. The device includes a limited-recovery protection control unit for determining whether a fault has occurred in the LLC power supply based on voltage and current sampling; a symmetrical PFM waveform generation unit for generating symmetrical PFM waveforms with paired waveforms having the same width; a variable dead-time frequency-limiting soft-start control unit for limiting the frequency and dead time of the symmetrical PFM waveforms and adjusting the given voltage during soft-start; and a constant-voltage current-limiting PI fast-switching control unit for closed-loop regulation of the LLC power supply.

[0098] Specifically, such as Figure 6 The diagram shown is a schematic diagram of the digital control device structure of the LLC power supply provided in an embodiment of the present invention.

[0099] In a specific example, the PFM frequency adjustment range of the symmetrical PFM waveform generation strategy is 120kHz to 300kHz, the dead time range is 100ns to 500ns, the soft start time is 3s, the restart interval time is 2s, and the closed-loop control frequency is 20kHz.

[0100] Specifically, the LLC power supply in this embodiment has a rated power of 20kW, an input voltage range of 640V to 680V, ​​a rated output voltage of 700V, a rated output current of 29A, an output overvoltage protection point of 750V, and an output overcurrent protection point of 35A. This embodiment uses a TMS320F28335 DSP as the control core, operating at a 150MHz main frequency, with a PFM frequency adjustment range of 120kHz to 300kHz, a minimum dead time of 100ns, a maximum dead time of 500ns, a soft start time of 3s, a restart interval of 2s, and a closed-loop control frequency of 20kHz.

[0101] In this embodiment, the LLC power supply uses the PFM generation module of the TMS320F28335 DSP to generate a symmetrical PFM waveform. The TBCTL.CTRMODE time base register is configured for up-and-down counting mode; the TBCTL.PRDLD time base register is configured to load when the counter is 0; the CMPCTL.LOADMODE comparator register is configured to load when the count is 0, using shadow mode; and the dead-time register DBCTL is set to accept inputs from both A and B, active high, with no polarity flipping between A and B. The frequency can be modified by changing the value of the period register TBPRD, and the dead-time size can be modified by changing the values ​​of the dead-time registers DBRED and DBFED. The PFM drive pulses generated by this method appear in pairs with equal pulse widths.

[0102] In a specific example, in the symmetrical PFM waveform generation strategy, the PFM period register varies from 1250 to 500 at a main frequency of 150MHz, corresponding to a period register TBPRD variation range of 625 to 250, and the dead time adjustment range is from 100ns to 500ns, corresponding to a dead time register DBRED and DBFED adjustment range of 15 to 75.

[0103] Specifically, in this embodiment, the PFM frequency adjustment range is 120kHz to 300kHz. Corresponding to a 150MHz main frequency, the cycle register variation range is 1250 to 500, and the corresponding cycle register TBPRD variation range is 625 to 250. The dead time adjustment range is 100ns to 500ns, corresponding to the dead time registers DBRED and DBFED adjustment ranges of 15 to 75.

[0104] During the variable dead-time frequency limiting soft-start control process, as the given voltage increases from 0V to 700V, the frequency allowed by the closed-loop regulation decreases from 300kHz to 120kHz, and the dead time decreases from 500ns to 100ns.

[0105] In a specific example, the maximum number of fault protection attempts is set to 3. If the number of attempts exceeds 3, the fault will be locked. If the number of attempts does not exceed 3, the system will wait for 2 seconds and then enter a slow start with a duration of 3 seconds.

[0106] This embodiment discloses a digital control device for an LLC power supply, which can realize soft start-up when the input-output voltage difference is high, fast switching between constant voltage and constant current, and self-recovery protection with a limited number of cycles.

[0107] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0108] It should also be noted that in the description of this invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0109] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A digital control method for an LLC power supply, characterized in that, The method includes Using a symmetrical PFM waveform generation strategy, symmetrical PFM waveforms with waveform pairs appearing and the same pair of waveforms having the same width are generated. The frequency and dead time of the symmetrical PFM waveform are limited by a variable dead-time frequency limiting soft-start control strategy, and the given voltage is adjusted during the soft-start process. A constant voltage and current limiting PI fast switching control strategy is used to perform closed-loop regulation of the LLC power supply; The dead-time frequency limiting and soft-start control strategy includes: The given voltage is linearly adjusted according to the given voltage regulation law, and remains constant after being adjusted to the rated voltage. The constant voltage current limiting PI fast switching control strategy includes: Whether to enter the current loop is determined by whether the current sampling exceeds the rated current; If the current sample exceeds the rated current, then control the output current of the LLC power supply to the rated current; The constant voltage current limiting PI fast switching control strategy further includes: If the current sample does not exceed the rated current, then a judgment is made based on the voltage sample. If the voltage sampling does not exceed the rated voltage, the closed-loop regulation will be performed based on whether the current or voltage is used as the regulation target, according to the state at the previous moment. The constant voltage current limiting PI fast switching control strategy further includes: Whether to enter the voltage loop is determined based on whether the voltage sampling exceeds the rated voltage; If the voltage sample exceeds the rated voltage, the output voltage of the LLC power supply will be controlled to the rated voltage.

2. The digital control method for an LLC power supply according to claim 1, characterized in that, The method further includes Using a limited-number self-recovery protection control strategy, the LLC power supply is judged to have a fault based on voltage and current sampling, and the number of faults is recorded. If the number of failures is less than the set value, the LLC power output is turned off and a soft start is performed again after a delay.

3. The digital control method for an LLC power supply according to claim 1, characterized in that, The symmetric PFM waveform generation strategy includes The counter is set to operate in increment / decrement counting mode, and the symmetrical PFM waveform is flipped when the count reaches 0 and the periodic count value, respectively.

4. The digital control method for an LLC power supply according to claim 3, characterized in that, The symmetrical PFM waveform generation strategy further includes The switching frequency is adjusted by modifying the cycle count value, and the dead time is obtained by delaying the rising edge.

5. The digital control method for an LLC power supply according to claim 1, characterized in that, The adjustment formula for closed-loop regulation of the LLC power supply is as follows: in, For the first The constant voltage and current limiting PI fast switching control signal is sampled in the next step. For the first The constant voltage and current limiting PI fast switching control signal is sampled in the next step. For control signals related to error; When in the voltage loop in, This is the voltage loop proportionality coefficient. The voltage loop integral coefficient, This refers to voltage loop error; When in a current loop in, This is the proportionality coefficient of the current loop. The integral coefficient of the current loop is... This is the current loop error.

6. A digital control device for an LLC power supply utilizing the method described in any one of claims 1 to 5, characterized in that, The device includes The limited-use self-recovery protection control unit is used to determine whether the LLC power supply has a fault based on voltage and current sampling. The symmetrical PFM waveform generation unit is used to generate symmetrical PFM waveforms in which waveform pairs appear and the width of the same pair of waveforms is consistent. A variable dead-time frequency limiting soft-start control unit is used to limit the frequency and dead time of the symmetrical PFM waveform, and to adjust the given voltage during the soft-start process; The constant voltage and current limiting PI fast switching control unit is used for closed-loop regulation of LLC power supply.

Images