Digital power supply control method based on wide output range of APFC + LLC structure

Abstract

The invention relates to the technical field of power electronic conversion, and discloses a wide output range digital power supply control method based on an APFC + LLC structure, and the method comprises the following steps: S1, detecting an output voltage (Vout) and a load current (Iload); s2, carrying out LCC frequency modulation control; s3, when light load or low voltage output occurs, LCC wave modulation control is started; and S4, when extremely light load or no load occurs, switching to an intermittent wave sending mode. By means of frequency modulation, wave modulation and intermittent wave generation, the output voltage is continuously adjusted by reducing the wave generation number when the upper limit of the adjustment frequency is reached, when the adjustable wave generation number is reduced to one wave, the intermittent wave generation mode is entered, and the purposes of wide output voltage adjustment range and small ripples can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic conversion control, and specifically to a digital power control method with a wide output range based on the APFC+LLC structure. Background Art

[0002] The LLC resonant converter controls the energy transfer and regulates the output voltage by adjusting the switching frequency (fsw) to change the impedance characteristics of the resonant network. Its core principle is based on the frequency response characteristics of the resonant tank (inductor Lr, capacitor Cr, and magnetizing inductor Lm).

[0003] The control methods include frequency conversion control (PFM, Pulse Frequency Modulation), burst mode control, and output voltage regulation mechanism. Specifically:

[0004] 1. Frequency conversion control (PFM, Pulse Frequency Modulation)

[0005] Operating frequency range:

[0006] Higher than the resonant frequency (fsw>fr): The resonant network is inductive, achieving zero voltage switching (ZVS) for efficient regulation;

[0007] Lower than the resonant frequency (fsw<fr): It may enter the capacitive region, resulting in an increase in switching losses;

[0008] Gain formula:

[0009]

[0010] Where: <00xxxxxx><00xxxxxx>Ln = Lm / Lr (inductance ratio), <00xxxxxx><00xxxxxx>fn = fsw / fr (normalized frequency), <00xxxxxx><00xxxxxx>[[ID=4x]]Q is the quality factor; <00xxxxxxy><00xxxxxx>2. Burst mode control <00xxxxxx><00xxxxxx>Applicable scenario: Under light load or no load conditions, to reduce switching losses; <00xxxxxx><00xxxxxx>Operating logic: <00xxxxxx><00xxxxxx>Wave generation period: Operate at a fixed frequency for a short time to transfer energy to the output; <00xxxxxx><00xxxxxx>Sleep period: Turn off the switch tube, and the output capacitor maintains the voltage until the voltage drops to the threshold and then wave generation resumes; <00xxxxxx>

[0019] 3. Output voltage regulation mechanism

[0020] Closed-loop feedback control:

[0021] Sample the output voltage Vout, compare it with the reference voltage Vref, and dynamically adjust fsw through the PID controller;

[0022] Gain curve adjustment:

[0023] By changing fsw, voltage regulation is achieved by utilizing the monotonic range of the resonant gain curve (fsw>fr).

[0024] Currently, LLCs regulate output by adjusting the switching frequency (fsw). When the load is light or no-load, the switching frequency reaches the upper limit and cannot be adjusted further. In this case, intermittent wave control is used to stabilize the output. This method has the following problems:

[0025] 1. Directly using intermittent ripple when light load is applied, and relying on capacitor energy storage during the dormant period, results in increased voltage ripple (typically 1%-3%), which is not suitable for high-precision scenarios;

[0026] 2. When the frequency adjustment upper limit is reached, it can only rely on intermittent wave transmission and cannot continue to adjust the frequency. The voltage adjustment range is narrow.

[0027] Based on this, the present application proposes a digital power supply control method with a wide output range based on an APFC+LLC structure to solve the above problems. Summary of the Invention

[0028] (1) Technical problems solved

[0029] In response to the shortcomings of the existing technology, the present invention provides a digital power supply control method with a wide output range based on the APFC+LLC structure. This method can continue to adjust the output voltage by reducing the number of waves when the upper limit of the adjustment frequency is reached. When the number of adjustable waves is reduced to 1 wave, the method enters the intermittent wave mode, which can achieve the purpose of adjusting the output voltage over a wide range and small ripple.

[0030] (2) Technical solution

[0031] To achieve the above objectives, the present invention provides the following technical solution: a digital power supply control method with a wide output range based on an APFC+LLC structure, comprising the following steps:

[0032] S1, detect output voltage (Vout) and load current (Iload);

[0033] S2, perform LCC frequency modulation control;

[0034] S3: When light load or low voltage output occurs, LCC wave modulation control is enabled;

[0035] S4. When extremely light load or no load occurs, switch to the intermittent wave - sending mode.

[0036] Preferably, the LCC frequency modulation control includes the following steps:

[0037] (1) Detect the output voltage (Vout) and compare it with the reference value (Vref);

[0038] (2) If Vout < Vref, increase the switching frequency (fs);

[0039] (3) If Vout > Vref, decrease the switching frequency (fs);

[0040] (4) Adjust the driving signal frequency through the PWM controller;

[0041] (5) Return to the detection link and perform closed - loop feedback.

[0042] Preferably, the enabling of LCC wave modulation control includes the following steps:

[0043] (1) If the frequency modulation control frequency > the maximum switching frequency fsMax, reduce the number of wave - sendings, and the minimum reduction is to 1 wave;

[0044] (2) If the frequency modulation control frequency < 250 Khz, increase the number of wave - sendings, and the maximum increase is to full - wave;

[0045] (3) Adjust the driving signal frequency and the number of waves through the PWM controller;

[0046] (4) Return to the control link and perform closed - loop feedback.

[0047] Preferably, the switching to the intermittent wave - sending mode includes the following steps:

[0048] (1) Detect the load current (Iload) or the output voltage (Vout); <00****100>

[0049] (2) If Iload < the light - load threshold and Vout > Vmax, enter the intermittent wave - sending mode; [[ID=****46]]

[0050] (3) Turn off the driving signal and stop the switching action;

[0051] (4) Monitor Vout until it drops to the lower limit (Vmin);

[0052] (5) Restart the PFM control until Vout rises to Vmax;

[0053] (6) Cycle the start - stop switching action;

[0054] [[ID=5**9]] (7) If Iload > the light - load threshold, continue with PFM control;

[0055] (8) Return to the testing phase.

[0056] (3) Beneficial effects

[0057] Compared with the prior art, the present invention provides a digital power supply control method with a wide output range based on the APFC+LLC structure, which has the following beneficial effects:

[0058] The present invention uses frequency modulation plus wave modulation and intermittent wave generation to continue adjusting the output voltage by reducing the number of waves when the upper limit of the adjustment frequency is reached. When the number of adjustable waves is reduced to 1 wave, the intermittent wave generation mode is entered again, thereby achieving the purpose of adjusting the output voltage to a wide range and small ripple. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the combined control strategy of the present invention;

[0060] Figure 2 This is the LLC frequency modulation control (PFM) flow chart of the present invention;

[0061] Figure 3 This is the LLC wave modulation control flow chart of the present invention;

[0062] Figure 4 This is a waveform diagram of the wave modulation control of the present invention;

[0063] Figure 5 This is a flow chart of the intermittent wave control (Burst Mode) of the present invention. DETAILED DESCRIPTION

[0064] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0065] The present invention aims to provide a digital power supply control method with a wide output range based on an APFC+LLC structure. The method can continue to adjust the output voltage by reducing the number of waves when the upper limit of the adjustment frequency is reached. When the number of adjustable waves is reduced to 1 wave, the method enters the intermittent wave mode, thereby achieving the purpose of adjusting the output voltage over a wide range and reducing ripple.

[0066] For details, please refer to Figure 1 , including the following steps:

[0067] S1, detect output voltage (Vout) and load current (Iload);

[0068] S2. Perform LCC frequency modulation control;

[0069] S3. When there is light load or low-voltage output, enable LCC wave modulation control;

[0070] S4. When there is extremely light load or no load, switch to the intermittent wave mode.

[0071] Among them, please refer to Figure 2 , the LCC frequency modulation control includes the following steps:

[0072] (1) Detect the output voltage (Vout) and compare it with the reference value (Vref);

[0073] (2) If Vout < Vref, increase the switching frequency (fs);

[0074] (3) If Vout > Vref, decrease the switching frequency (fs);

[0075] (4) Adjust the driving signal frequency through the PWM controller;

[0076] (5) Return to the detection link and perform closed-loop feedback.

[0077] The frequency adjustment mechanism is: The LLC resonant converter controls the output voltage by adjusting the switching frequency (fs).

[0078] When fs is higher than the resonant frequency (fr), the gain decreases;

[0079] When fs is lower than fr, the gain increases.

[0080] During light load: Increase fs to reduce the gain and maintain voltage stability;

[0081] During heavy load: Decrease fs to increase the gain.

[0082] Specifically, the difference between Vout and Vref is converted into a frequency control signal through a voltage error amplifier (EA), and the frequency of the driving signal is adjusted through a digital controller (such as an MCU).

[0083] Please refer to Figure 3 , enabling the LCC wave modulation control includes the following steps:

[0084] (1) If the frequency modulation control frequency > the maximum switching frequency fsMax, reduce the number of waves, and the minimum reduction is to 1 wave;

[0085] (2) If the frequency modulation control frequency < 250Khz, increase the number of waves, and the maximum increase is to full wave;

[0086] (3) Adjust the driving signal frequency and the number of waves through the PWM controller;

[0087] (4) Return to the control link and close the loop feedback.

[0088] The principle of wave modulation control is: when the LLC output can be stabilized by adjusting the frequency within the frequency range of 250Khz, the LLC output is controlled by frequency modulation. When the frequency adjustment is increased to more than 250Khz and is still not enough to stabilize the LLC output, the frequency is continued to be increased, and the maximum frequency is limited to within 300Khz. At the same time, the number of waves sent is reduced, and 5 waves are sent first, and then a wave is not sent, to stabilize the LLC output. If the frequency reaches 300Khz and is still not enough to stabilize the output, the number of waves sent is further reduced. The minimum number of waves sent is 1 wave and 5 waves are left blank. For details, please refer to Figure 4 .

[0089] At very light load or no load, PFM frequency modulation may cause the frequency to be too high and the efficiency to drop. At this time, switch to intermittent wave mode. Figure 5 , switching to intermittent wave mode includes the following steps:

[0090] (1) Detect load current (Iload) or output voltage (Vout);

[0091] (2) If Iload < light load threshold and Vout > Vmax, enter intermittent wave mode;

[0092] (3) Turn off the drive signal and stop the switch action;

[0093] (4) Monitor Vout until it drops to the lower limit (Vmin);

[0094] (5) Restart PFM control until Vout rises to Vmax;

[0095] (6) Cyclic start and stop switch action;

[0096] (7) If Iload>light load threshold, continue PFM control;

[0097] (8) Return to the testing phase.

[0098] Its control logic is:

[0099] Stop phase: When Vout reaches the upper limit (Vmax), the drive signal is completely turned off and energy transmission stops;

[0100] Wave generation stage: When Vout drops to the lower limit (Vmin), PFM control is re-enabled and works for a short time to replenish energy.

[0101] The present invention uses frequency modulation plus wave modulation and intermittent wave generation to continue adjusting the output voltage by reducing the number of waves when the upper limit of the adjustment frequency is reached. When the number of adjustable waves is reduced to 1 wave, the intermittent wave generation mode is entered again, thereby achieving the purpose of adjusting the output voltage to a wide range and small ripple.

[0102] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A digital power supply control method with a wide output range based on an APFC+LLC structure, characterized in that: It includes the following steps: S1. Detect the output voltage (Vout) and the load current (Iload); S2. Perform LCC frequency modulation control; S3. When there is a light load or a low voltage output, enable the LCC wave modulation control; S4. When there is an extremely light load or no load, switch to the intermittent wave generation mode.

2. The digital power supply control method based on the APFC+LLC structure with a wide output range according to claim 1, characterized in that: The LCC frequency modulation control includes the following steps: (1) Detect the output voltage (Vout) and compare it with the reference value (Vref); (2) If Vout < Vref, increase the switching frequency (fs); (3) If Vout > Vref, decrease the switching frequency (fs); (4) Adjust the driving signal frequency through the PWM controller; (5) Return to the detection link and perform closed-loop feedback.

3. The digital power supply control method based on the APFC+LLC structure with a wide output range according to claim 1, characterized in that: The enabling of the LCC wave modulation control includes the following steps: (1) If the frequency modulation control frequency > the maximum switching frequency fsMax, reduce the number of generated waves, with the minimum reduction to 1 wave; (2) If the frequency modulation control frequency < 250 Khz, increase the number of generated waves, with the maximum increase to full waves; (3) Adjust the driving signal frequency and the number of waves through the PWM controller; (4) Return to the control link and perform closed-loop feedback.

4. The digital power supply control method based on the APFC+LLC structure with a wide output range according to claim 1, characterized in that: The switching to the intermittent wave generation mode includes the following steps: (1) Detect the load current (Iload) or the output voltage (Vout); (2) If Iload < the light load threshold and Vout > Vmax, enter the intermittent wave generation mode; (3) Turn off the driving signal and stop the switching action; (4) Monitor Vout as it drops to the lower limit (Vmin); (5) Restart the PFM control until Vout rises to Vmax; (6) Cyclically start and stop the switching action; (7) If Iload > the light load threshold, continue with the PFM control; (8) Return to the detection link.

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