A Digital Phase-Shift Control Method and Device for a Wide-Input Full-Bridge LLC Resonant Converter

Abstract

The present invention belongs to the technical field of resonant switching converters, and specifically relates to a digital phase-shift control method and device for a wide-input full-bridge LLC resonant converter, which is used to solve the problem that the switching loss of the resonant switching converter circuit increases and the efficiency decreases as the switching frequency increases, and at the same time broaden the input voltage range. The present invention includes a power supply, a power supply circuit, a feedback circuit, and an output load R0. In the present invention, the digital controller DSP samples the output voltage V0, compares the sampled output voltage V0 with the reference voltage V ref for comparison. The digital controller DSP judges the obtained error signal, and according to the preset program, the DSP completes the adjustment of the output voltage by controlling the adjustment of the phase-shift angle size. For the transformer rear-stage circuit, a shunt voltage regulator is used to easily achieve zero-voltage switching under full load and wide-range input conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of resonant switching converters, in particular to a digital phase-shift control method and device for a wide-input full-bridge LLC resonant converter. Background Art

[0002] A switch-mode power supply (SMPS), also known as a switching power supply or a switch converter, is a high-frequency power conversion device and a type of power supply. Its function is to convert a voltage level into the voltage or current required by the user through different forms of architectures. The input of a switch power supply is mostly an AC power supply (such as the mains power) or a DC power supply, and the output is mostly devices that require a DC power supply, such as a personal computer, and the switch power supply performs the conversion of voltage and current between the two.

[0003] A switch power supply is different from a linear power supply. The switching transistors used in a switch power supply mostly switch between the fully-on mode (saturation region) and the fully-off mode (cut-off region). Both of these modes have the characteristic of low dissipation. Although there is relatively high dissipation during the switching between them, the time is very short, so it is more energy-saving and generates less waste heat. Ideally, a switch power supply itself does not consume electrical energy. Voltage regulation is achieved by adjusting the on and off times of the transistors. On the contrary, during the process of generating the output voltage, the transistors in a linear power supply operate in the amplification region and consume electrical energy themselves. The high conversion efficiency of a switch power supply is one of its major advantages. Moreover, because the switch power supply operates at a high frequency, small-size and light-weight transformers can be used, so the switch power supply is also smaller in size and lighter in weight than a linear power supply.

[0004] When the high efficiency, volume, and weight of the power supply are the key considerations, a switch power supply is better than a linear power supply. However, a switch power supply is more complex, and the internal transistors switch frequently. If the switching current is not processed, it may generate noise and electromagnetic interference, affecting other devices. Moreover, if the switch power supply is not specially designed, its power factor may not be high.

[0005] With the rapid development of the automotive industry, the problems of energy and environment are becoming increasingly serious. New energy electric vehicles that are clean and environmentally friendly have emerged in the public view. The key to the charging technology of new energy electric vehicles is DC-DC (direct current conversion), which converts through PFC (power factor correction) into direct current that meets the requirements of automotive batteries. Research shows that an LLC resonant converter can achieve wide-range voltage regulation, and does not increase the switching loss as the switching frequency increases, nor does the conversion efficiency decrease accordingly. At the same time, it can also effectively reduce the volume of the charger, thereby increasing the power density. Therefore, the research on LLC resonant converters has received more and more attention from the academic and industrial circles.

[0006] The present invention uses a digital phase-shift control method to achieve the stabilization of the output voltage of an LLC resonant converter. The control idea is as follows: The control circuit selects the voltage loop. The voltage loop compares the detected output voltage with the reference voltage, judges the obtained error signal, and transmits the judgment result to the inside of the DSP. The DSP adjusts the magnitude of the phase-shift angle α by controlling the full-bridge switch composed of four switches, and maintains the stability of the output voltage by changing the magnitude of the phase-shift angle. This method is used for a full-bridge LLC resonant converter, which has a simple circuit structure and is easy to implement, can achieve soft switching within the effective phase-shift angle range, and can improve the efficiency of the converter at the same time, realizing a high-frequency and high-efficiency switching converter.

[0007] In the prior art, there are problems such as switching losses and conduction losses in the converter. By adopting the digital phase-shift control technology in a full-bridge converter, zero-voltage startup or zero-current turn-off can be achieved without increasing the circuit cost and reducing the circuit volume, resulting in a significant reduction in the loss power. For the conduction loss, adding a switching tube on the secondary output rectification side has a lower forward voltage drop, which can significantly improve the overall power supply efficiency. Summary of the Invention

[0008] The purpose of the present invention is to provide a digital phase-shift control method and device for a wide-input full-bridge LLC resonant converter to solve the problems mentioned in the above background technology. The purpose is to provide a method and device combined with DSP technology, making it have the characteristics of high frequency, high efficiency, and a simple and easy-to-implement circuit structure, and at the same time, it can also maintain the stability of the output voltage within a relatively wide input voltage range.

[0009] The present invention provides the following technical solutions to solve the above technical problems:

[0010] A digital phase-shift control device for a wide-input full-bridge LLC resonant converter includes a power supply, a power supply circuit, a digital controller DSP, and an output load R0. The power supply circuit includes a full-bridge conversion circuit coupled to the power supply with a drive circuit, a resonant network coupled to the full-bridge conversion circuit, an isolation transformer coupled to the resonant network, a parallel voltage regulator coupled to the isolation transformer, and a load output R0 coupled to the parallel voltage regulator;

[0011] The parallel voltage regulator includes a main rectifier and a regulator connected in parallel with each other, and a filter connected in series after the main rectifier and the regulator are connected in parallel;

[0012] The main rectifier includes a winding and diodes D2 and D3 connected in parallel;

[0013] The regulator includes a winding, a diode D1 and a diode D4 connected in parallel with each other, an inductor Lf1 and a switching transistor G5 connected in series after being connected in parallel; a connection point is provided between the inductor Lf1 and the switching transistor G5, one end of a capacitor Cf1 is connected to the connection point, and the other end is grounded;

[0014] The filter includes an inductor Lf and a capacitor Cf connected to the inductor Lf, and the other end of the capacitor Cf is grounded; the capacitor Cf is connected in parallel with a load output R0;

[0015] The input end of the digital controller DSP is connected to the non-grounded side of the output load R0, and the output end of the digital controller DSP is respectively connected to switching transistors G1, G2, G3, G4 bridged in a full-bridge conversion circuit and the gate of the switching transistor G5.

[0016] After adopting this technical solution, the full-bridge conversion circuit adopts a full-bridge switching structure composed of four switching transistors. The digital controller DSP issues a pulse signal, and the dead time is controlled through the internal program of the digital controller DSP to control the conduction and cutoff of the switching transistors G1, G2, G3, and G4. When the switching transistors G1 and G4 are conducting, G2 and G3 are cutoff. After half a cycle, when the switching transistors G2 and G3 are conducting, G1 and G4 are cutoff. When G1, G4 and G2, G3 are conducting, the turn-on times are not simultaneous. The interval of this turn-on time is the phase-shift angle α of the switching transistors G1, G4 or G2, G3. The overlapping conduction time of the switching transistors G1, G4 or G2, G3 is the time when the input voltage of the power supply is transmitted to the resonant network, which can be called the conduction angle θ.

[0017] The control loop of the circuit controls the simultaneous conduction time of the switching transistors G1, G4 or G2, G3 through the conduction angle θ, and the duty cycle of the circuit always remains at 0.5, converting the power input voltage Vin passing through the full-bridge conversion circuit into Vab transmitted to the LLC resonant network. Within one cycle, the conduction time of the Vab voltage is controlled by the magnitude of the conduction angle θ. The digital controller DSP is responsible for sampling the output voltage and controlling the change of the phase-shift angle α through the internal program: when the output voltage Vo is greater than the reference voltage Vref, the DSP reduces the conduction angle θ; when the output voltage Vo is less than the reference voltage Vref, the DSP increases the conduction angle θ. Until the output voltage is stabilized near the rated output voltage, the conduction angle θ is fixed, thereby maintaining the stability of the output voltage.

[0018] In the present invention, the circuit structure is simple and easy to implement, soft switching can be achieved within the effective phase-shift angle range, and at the same time, the efficiency of the converter can be improved to achieve high-frequency and high-efficiency switching.

[0019] A parallel voltage regulator is adopted at the rear stage of the transformer. The parallel regulator consists of a filter composed of Lf1 and Cf1. The parallel voltage regulator reduces the voltage stress between the main rectifier diodes D2 and D3; most of the output power is effectively transmitted through the unregulated main rectifier diodes D2 and D3, and the remaining output power is transmitted by the parallel voltage regulator, thus significantly improving the efficiency.

[0020] The winding between the main rectifier diodes D2 and D3 is grounded to make its level consistent with the level of the load ground terminal.

[0021] Preferably, the digital controller DSP controls the on and off of the switching tubes G1, G2, G3, and G4 of the full-bridge conversion circuit, and the duty cycle of the full-bridge conversion circuit always remains at 0.5.

[0022] Preferably, the digital controller DSP is the digital controller TMS320F28335.

[0023] After adopting this technical solution, TMS320F28335 has a high-speed processing ability of 150MHz. Compared with TI's previous generation digital signal controller, the performance is increased by an average of 50%. For complex calculation algorithms such as fast Fourier transform (FFT), the performance is doubled. There are up to 18 PWM outputs, among which 6 are TI's unique higher-precision PWM outputs (HRPWM), meeting the requirements of this invention for PWM waves. Based on the 32-bit floating-point processing unit, control algorithms can be quickly written and are compatible with the fixed-point C28x controller software, thus simplifying software development, shortening the development cycle, and reducing the development cost.

[0024] A digital phase-shifting control method for a wide-input full-bridge LLC resonant converter includes the following steps:

[0025] Step 1: Write a program for the digital controller DSP to implement digital control, and set the dead time and phase-shifting angle in the program;

[0026] Step 2: The digital controller DSP collects the output voltage V0 of the parallel voltage regulator, compares the collected output voltage V0 with the preset reference voltage V ref to obtain an error signal, and then judges the value of the error signal to adjust the size of the phase-shifting angle. If the error signal is greater than 0, the phase-shifting angle is adjusted by a corresponding value; on the contrary, if the error signal is less than 0, the phase-shifting angle is adjusted smaller;

[0027] Step 3: The digital controller DSP controls the on and off of the switching tubes G1, G2, G3, and G4 of the full-bridge conversion circuit according to the set program;

[0028] Step 4: Repeat Step 2 and Step 3 until the output voltage V0 is stabilized at the preset reference voltage Vref 。

[0029] Preferably, the DSP program of the digital controller is as follows:

[0030] Initialization;

[0031] Accumulate the PWM cycle counter;

[0032] Parallel regulator switch tube G5;

[0033] Obtain the output voltage;

[0034] Calculate the PI loop voltage error;

[0035] Calculate the integral quantity;

[0036] Limit the integral quantity;

[0037] PI output = integral quantity + proportional quantity;

[0038] Limit the phase shift angle;

[0039] Set the conduction and turn-off of Q1, Q2, Q3, and Q4 according to the PWM cycle count and phase shift angle conditions;

[0040] Set the dead zone;

[0041] Clear the PWM cycle counter, and one cycle is completed.

[0042] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0043] 1. The present invention realizes a digital phase shift control method in an LLC resonant converter, effectively improving the stability of the system, greatly reducing the volume and manufacturing cost of the circuit, and thus enhancing the power density of the circuit.

[0044] 2. The present invention realizes a control technology for broadening the input voltage range, can achieve soft switching in a large range, and realizes high efficiency.

[0045] 3. The parallel regulator reduces the voltage stress between the main rectifiers D2 and D3; it also reduces the conduction losses of D1 and D4, as well as the switching losses. At the same time, only a very small requirement for the output filter makes the power density increase significantly. In addition, most of the output power is effectively transmitted through the unregulated main rectifier, and the remaining part of the output power is regulated by the parallel regulator, thereby significantly improving the efficiency at high input voltages. Brief Description of the Drawings

[0046] Figure 1 It is the circuit topology diagram of the present invention.

[0047] Figure 2This is the circuit structure block diagram of the post-stage parallel voltage regulator of the transformer adopted by the present invention.

[0048] Figure 3 This is the main waveform diagram of the LLC resonant circuit.

[0049] Figure 4 This is the main working waveform of the full-bridge switching module of the present invention.

[0050] Figure 5 This is the brief flow chart of the digital controller DSP.

[0051] Figure 6 This is the main working process of the PWM task.

[0052] Figure 7 This is the main working circuit of the parallel post-stage voltage regulator.

[0053] Figure 8 This is the simulation waveform diagram of the output voltage when the input voltage jumps in the full-bridge LLC resonant converter implemented by the digital phase-shift control method and the present invention.

[0054] Figure 9 This is the voltage ripple waveform diagram of the simulation conditions. Specific embodiments

[0055] In order to make the technical means, features and effects achieved by the present invention easier to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments and the accompanying drawings in the embodiments of the present invention.

[0056] As Figures 1 - 9 shown, the optimal embodiment of the present invention is described as follows:

[0057] Referring to Figure 1 shown, a digital phase-shift control device for a wide-input full-bridge LLC resonant converter includes a power supply, a power supply circuit, a digital controller DSP, and an output load R0. The power supply circuit includes a full-bridge conversion circuit coupled to the power supply with a drive circuit, a resonant network coupled to the full-bridge conversion circuit, an isolation transformer coupled to the resonant network, a parallel voltage regulator coupled to the isolation transformer, and a load output R0 coupled to the parallel voltage regulator;

[0058] The parallel voltage regulator includes a main rectifier and a regulator connected in parallel with each other, and a filter connected in series after the main rectifier and the regulator are connected in parallel;

[0059] The main rectifier includes a winding and diodes D2 and D3 connected in parallel;

[0060] The regulator includes a winding, a diode D1 and a diode D4 connected in parallel, an inductor Lf1 and a switching transistor G5 connected in series after being connected in parallel; a connection point is provided between the inductor Lf1 and the switching transistor G5, one end of a capacitor Cf1 is connected to the connection point, and the other end is grounded;

[0061] The filter includes an inductor Lf and a capacitor Cf connected to the inductor Lf, and the other end of the capacitor Cf is grounded; the capacitor Cf is connected in parallel with a load output R0;

[0062] The input end of the digital controller DSP is connected to the non-grounded side of an output load R0, and the output end of the digital controller DSP is respectively connected to switching transistors G1, G2, G3, G4 of a full-bridge conversion circuit in a bridging manner and the gate of the switching transistor G5.

[0063] See Figure 1 As shown, the full-bridge conversion circuit adopts a full-bridge switching structure composed of four switching transistors. A pulse signal is sent by the digital controller DSP, and the dead time is controlled through an internal program of the digital controller DSP to control the conduction and cut-off of the switching transistors G1, G2, G3, G4. When the switching transistors G1 and G4 are conducting, G2 and G3 are cut off. After half a cycle, when the switching transistors G2 and G3 are conducting, G1 and G4 are cut off. When G1, G4 and G2, G3 are conducting, the opening times of the two conducting switching transistors are not simultaneous. This time interval of the opening time is the phase shift angle α between the two switching transistors, and the time when the two switching transistors overlap in conduction is the time when the input voltage of the power supply is transmitted to the resonant network, which can be called the conduction angle θ.

[0064] The control loop of the circuit controls the time when the two switching transistors conduct simultaneously through the conduction angle θ, and the duty cycle of the circuit always remains at 0.5. The input voltage V of the power supply passing through the full-bridge conversion circuit in is converted into V transmitted to the LLC resonant network ab . In one cycle, the conduction time of the V ab voltage is controlled by the magnitude of the conduction angle θ. The digital controller DSP is responsible for sampling the output voltage and controlling the change of the phase shift angle α through an internal program: when the output voltage V o is greater than the reference voltage V ref , the DSP reduces the conduction angle θ; when the output voltage V o is less than the reference voltage V ref , the DSP increases the conduction angle θ. Until the output voltage is stabilized near the rated output voltage, the conduction angle θ is fixed, thereby maintaining the stability of the output voltage.

[0065] In this embodiment, the circuit structure is simple and easy to implement, soft switching can be achieved within the effective phase shift angle range, and at the same time, the efficiency of the converter can be improved to achieve high-frequency and high-efficiency switching.

[0066] See Figure 1 As shown, a parallel voltage regulator is adopted at the rear stage of the transformer to reduce the voltage stress between the main rectifiers D1 and D2; most of the output power is effectively transmitted through the unregulated main rectifiers D1 and D2, and the remaining output power is transmitted by the parallel post-regulator, thus significantly improving the efficiency.

[0067] In this embodiment, the digital controller DSP controls the on and off of the switching tubes G1, G2, G3, and G4 of the full-bridge conversion circuit, and the duty cycle of the full-bridge conversion circuit always remains at 0.5.

[0068] In this embodiment, the digital controller DSP is the digital controller TMS320F28335.

[0069] In this embodiment, TMS320F28335 has a high-speed processing capability of 150 MHz. Compared with TI's previous-generation digital signal controllers, the performance is increased by an average of 50%. For complex calculation algorithms such as fast Fourier transform (FFT), the performance is more than doubled. There are up to 18 PWM outputs, among which 6 are TI's unique higher-precision PWM outputs (HRPWM), meeting the requirements of this invention for PWM waves. Based on the 32-bit floating-point processing unit, it can quickly write control algorithms and is compatible with the fixed-point C28x controller software, thus simplifying software development, shortening the development cycle, and reducing the development cost.

[0070] A digital phase-shift control method for a wide-input full-bridge LLC resonant converter includes the following steps:

[0071] Step 1: Write a program for the digital controller DSP to implement digital control, and complete the setting of dead time and phase-shift angle in the program;

[0072] Step 2: The digital controller DSP collects the output voltage V0 of the parallel voltage regulator, compares the collected output voltage V0 with the preset reference voltage V ref to obtain an error signal, and then judges the value of the error signal to adjust the phase-shift angle. If the error signal is greater than 0, the phase-shift angle is adjusted by a corresponding value; on the contrary, if the error signal is less than 0, the phase-shift angle is adjusted smaller;

[0073] Step 3: The digital controller DSP controls the on and off of the switching tubes G1, G2, G3, and G4 of the full-bridge conversion circuit according to the set program;

[0074] Step 4: Repeat Step 2 and Step 3 until the output voltage V0 is stabilized at the preset reference voltage V ref .

[0075] In this embodiment, the digital controller DSP program is:

[0076] Initialization;

[0077] The PWM period counter accumulates;

[0078] Parallel regulator switch tube G5;

[0079] Obtain the output voltage;

[0080] Calculate the PI loop voltage error;

[0081] Calculate the integral quantity;

[0082] Integral quantity limitation;

[0083] PI output = integral quantity + proportional quantity;

[0084] Phase shift angle limitation;

[0085] According to the PWM period count and phase shift angle conditions, set the conduction and turn-off of Q1, Q2, Q3, and Q4;

[0086] Set the dead zone;

[0087] Clear the PWM period counter, and one cycle is completed.

[0088] The present invention is a digital phase-shift control method and device for a wide-input full-bridge LLC resonant converter. The output voltage V0 is sampled by a digital controller DSP, and the collected output voltage V0 is compared with a preset reference voltage V ref for comparison. The digital controller DSP judges the obtained error signal, and according to a preset program, the DSP completes the regulation of the output voltage by controlling the adjustment of the phase shift angle. For the transformer secondary circuit, a parallel voltage regulator is used to easily achieve zero-voltage switching under full-load and wide-range input conditions. The parallel voltage regulator reduces the voltage stress between the main rectifiers D2 and D3; it also reduces the conduction losses of D1 and D4, as well as the switching losses. At the same time, only a very small requirement for the output filter significantly increases the power density. In addition, most of the output power is effectively transmitted through the unregulated main rectifier, and the remaining part of the output power is regulated by the parallel voltage regulator, thereby significantly improving the efficiency at high input voltages.

[0089] The working principle of the invention is further described below in conjunction with the attached drawings so that those skilled in the art can fully understand the present invention, which is specifically described as follows:

[0090] See Figure 3As shown in the figure, one switching cycle is divided into 8 operating modes, and the waveforms of the upper and lower four cycles are symmetrical. Therefore, only four modes in half of the switching cycle need to be analyzed. To simplify the analysis, on the basis of not affecting the overall circuit design, it is assumed that: all diodes and switching tubes are ideal devices; the output filter capacitor Cf is large enough to be regarded as a constant voltage source; all capacitors, inductors and transformers are ideal components, and the circuit impedance is not considered.

[0091] Mode 0 [before t0]: Before t0, the switching tubes G2 and G3 are conducting, G1 and G4 are off, and V ab is 0. The resonant inductor L r , the exciting inductor L m and the resonant capacitor C r resonate simultaneously. The resonant current I Lr , the exciting current I Lm are equal and flow in opposite directions. The transformer current is 0, and the primary of the transformer stops transferring energy to the secondary. The load is supplied with energy by the filter capacitor C o .

[0092] Mode 1 [t0 - t1]: At t0, the switching tube G2 turns off, C2 is charged and C4 is discharged. L r , L m and C r resonate simultaneously. I Lr =I Lm . The load is supplied with energy by the filter capacitor Cf. The current of the rectifier diode on the secondary side of the transformer is continuous, and the rectifier diode is hard turned off.

[0093] Mode 2 [t1 - t2]: At t1, the discharge of C4 is completed, and the diode in the body of G4 conducts, providing conditions for the ZVS of G4. The exciting inductor L m is clamped and does not participate in resonance. Although the rectifier diode is continuous, it naturally freewheels to zero at the critical point. Therefore, the rectifier diode on the secondary side can achieve zero-current turn-off, that is, ZCS.

[0094] Mode 3 [t2 - t3]: At t2, G4 achieves ZVS. The exciting current I Lm increases linearly. L r and C r resonate, and the primary of the transformer starts to transfer energy to the secondary.

[0095] Mode 4 [t3 - t4]: At t3, the switching tubes G1 and G4 conduct, G2 and G3 turn off, and the resonant current I Lr , the exciting current I Lm begin to flow positively through zero. At t4, the switching tube G1 turns off, C3 is charged and C1 is discharged, providing conditions for the ZVS of G4, and V ab is 0.

[0096] Before t0, switch tubes G2 and G3 are conducting, G1 and G4 are off, and V ab is 0. Resonant inductor L r , exciting inductor L m and resonant capacitor C r resonate simultaneously. Resonant current I Lr , exciting current I Lm are equal and flow in opposite directions. Transformer current is 0, and the primary of the transformer stops transferring energy to the secondary. The load is powered by filter capacitor Cf. At t0, switch tube G2 turns off, C2 charges, C4 discharges, and L r , L m and C r resonate simultaneously. I Lr = I Lm . The load is powered by filter capacitor Cf. The rectifier diode current on the secondary side of the transformer is continuous, and the rectifier diode has a hard turn-off. At t1, C4 finishes discharging, the diode in the body of G4 conducts, providing conditions for ZVS of G4. Exciting inductor L m is clamped and does not participate in resonance. Although the rectifier diode is continuous, it naturally freewheels to zero at the critical point. Therefore, the secondary rectifier diode can achieve zero-current turn-off, i.e., ZCS. At t2, G4 achieves ZVS. Exciting current I Lm increases linearly, and L r and C r resonate. The primary of the transformer starts to transfer energy to the secondary. At t3, switch tubes G1 and G4 conduct, G2 and G3 turn off, and resonant current I Lr , exciting current I Lm begin to flow positively through zero. At t4, switch tube G1 turns off, C3 charges, C1 discharges, providing conditions for ZVS of G4, and V ab is 0. After that, the full-bridge LLC resonant converter enters the second half cycle, and the situation is similar.

[0097] See Figure 4 shown. There is a small dead time between the conduction and turn-off of switch tubes G1 and G2 to prevent the switch tubes from short-circuiting due to direct connection. The same applies to G3 and G4. There is a phase shift angle α between the start conduction times of switch tubes G1 and G4. The purpose is to control the conduction time of voltage V ab transmitted to the resonant network, and finally achieve stable phase-shift control of the output voltage.

[0098] See Figure 5As shown in the figure, first, each module is initialized. Next, the PWM module is configured. There is an enhanced PWM module ePWM inside the DSP. Each full - comparison unit can generate two complementary PWM drive pulses. At the same time, the dead - time module is used to set the dead - time of the two complementary drive pulses, so as to avoid the direct connection of the two switching tubes G1 and G2 (or G3 and G4) in the same bridge arm, causing a short - circuit. Then, the task processing starts. This DSP also provides an ADC module for the sampling channel. By changing the phase - shift angle α according to the size of the sampling value, the phase - shift voltage regulation control can be realized.

[0099] See Figure 6 As shown in the figure, first, the output voltage Vo is sampled in the ADC sampling module. Then, the output voltage Vo is compared with the reference voltage V ref The phase - shift angle α is adjusted through the obtained error signal, and the result is then transmitted to the PWM module to complete the control of the output voltage Vo to achieve stability.

[0100] See Figure 7 As shown in the figure, similar to the above - mentioned LLC resonant circuit, the waveforms of the front and back two cycles are symmetric. Therefore, only half of the switching cycle needs to be analyzed. t0 - t1: G1, G3, G5 are conducting, D2, D3 are off, and the parallel - connected post - regulator supplies power to the load. At the t1 interval, the parallel - connected post - regulator is turned off, and the inductor current is transferred from G5 to D2. t1 - t2: D2 supplies power to the load. t2 - t3: G5 is turned off, and the leakage inductance of the transformer charges the parasitic capacitances of G1 and G2 until G2 conducts and G2 realizes ZVS.

[0101] The time - domain simulation analysis of the method of the present invention is carried out using the PSIM simulation software, and the results are as follows.

[0102] See Figure 8 As shown in the figure, for the digital phase - shift control full - bridge LLC resonant converter, the input voltage jumps from 380V to 420V. The output voltage starts to stabilize at 48V. After the voltage jump occurs, it re - enters the steady state and stabilizes at 48V after 0.017s.

[0103] See Figure 8 As shown in the figure, by adding a post - regulator on the original circuit, when the input voltage jumps from 320V to 500V, the output voltage starts to stabilize at 48V and re - enters the steady state and stabilizes at 48V after the voltage jump occurs. It can be seen that the input voltage range of the switching converter of the present invention is wider, and soft - switching can be realized in a large range, achieving high efficiency.

[0104] See Figure 9 As shown in the figure, the simulation conditions are that the input voltage V in = 320 - 500V, the resonant inductor L r = 540μH, the resonant capacitor Cr = 0.0047 μF, excitation inductance L m = 3240 μH, load resistance R = 19.2 Ω.

[0105] In the PSIM simulation, the digital controller DSP is replaced by the CBlock module, and the program is

[0106]

[0107]

[0108]

[0109]

[0110] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A digital phase-shift control device for a wide-input full-bridge LLC resonant converter, comprising a power supply, a power supply circuit, a digital controller DSP, and an output load R0, characterized in that: The power supply circuit includes a full-bridge conversion circuit coupled to the power supply and having a drive circuit, a resonant network coupled to the full-bridge conversion circuit, an isolation transformer coupled to the resonant network, a parallel voltage regulator coupled to the isolation transformer, and a load output R0 coupled to the parallel voltage regulator; The parallel voltage regulator includes a main rectifier and a regulator connected in parallel with each other, and a filter connected in series after the main rectifier and the regulator are connected in parallel; The main rectifier includes a winding and diodes D2 and D3 connected in parallel; The regulator includes a winding, diodes D1 and D4 connected in parallel with each other, an inductor Lf1 and a switching tube G5 connected in series in sequence after being connected in parallel; a connection point is provided between the inductor Lf1 and the switching tube G5, one end of a capacitor Cf1 is connected to the connection point, and the other end is grounded; The filter includes an inductor Lf and a capacitor Cf connected to the inductor Lf, and the other end of the capacitor Cf is grounded; the capacitor Cf is connected in parallel with the load output R0; The input end of the digital controller DSP is connected to the non-grounded side of the output load R0, and the output end of the digital controller DSP is respectively connected to the switching tubes G1, G2, G3, G4 bridged by the full-bridge conversion circuit and the gate of the switching tube G5.

2. The digital phase-shifting control device for a wide-input full-bridge LLC resonant converter according to claim 1, wherein: The digital controller DSP controls the conduction and cut-off of the switching tubes G1, G2, G3, G4 of the full-bridge conversion circuit, and the duty cycle of the full-bridge conversion circuit always remains at 0.

5.

3. The digital phase-shift control device for a wide-input full-bridge LLC resonant converter according to claim 1, characterized in that: The digital controller DSP is a digital controller TMS320F28335.

4. A digital phase-shift control method for a wide-input full-bridge LLC resonant converter, characterized in that: It includes the following steps: Step 1: Write a program for the digital controller DSP to implement digital control, and complete the setting of the dead time and phase shift angle in the program; Step 2: The digital controller DSP collects the output voltage V0 of the parallel voltage regulator, compares the collected output voltage V0 with a preset reference voltage V ref to obtain an error signal after comparison, and then judges the value of the error signal to adjust the phase shift angle. If the error signal is greater than 0, the phase shift angle is adjusted by a corresponding value; on the contrary, if the error signal is less than 0, the phase shift angle is adjusted smaller; Step 3: The digital controller DSP controls the conduction and cut-off of the switching tubes G1, G2, G3, G4 of the full-bridge conversion circuit according to the set program; Step 4: Repeat Step 2 and Step 3 until the output voltage V0 stabilizes at the preset reference voltage V ref .

5. A digital phase-shift control method for a wide-input full-bridge LLC resonant converter according to claim 4, characterized in that: The program of the digital controller DSP is as follows: Initialization; The PWM period counter accumulates; The switching tube G5 of the parallel voltage regulator; Obtain the output voltage; Calculate the PI loop voltage error; Calculate the integral amount; Integral amount limit; PI output = integral amount + proportional amount; Phase shift angle limit; According to the PWM period count and phase shift angle conditions, set the conduction and turn-off of Q1, Q2, Q3, Q4; Set the dead zone; Clear the PWM period counter, and one cycle is completed.

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