Auxiliary welding excitation power supply and control method

Abstract

The application discloses a kind of auxiliary welding excitation power supply and control method, including rectifier module, PFC module, LLC module, SR module and modulation module, the new circuit topology structure and control method are used in the present application, the limitation of traditional equipment is effectively avoided, integrates direct current, alternating current and other output functions on a set of equipment, and the frequency regulation range is wider, the device volume is smaller, and can be applied to more welding scene;Meanwhile, the present application adopts the mode of PFC+LLC+SR combination, reduces reactive power and power switch tube switching loss, improves power quality;The device only needs to set up preset target power function expression in advance, and the output control can be automatically completed using the control method of the present application, and the communication interface can be opened to realize online adjustment.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to an auxiliary welding excitation power supply and control method. Background Technology

[0002] The development direction of the welding industry has always been towards higher efficiency, energy saving and intelligent welding technology. Various new welding methods have emerged, such as laser welding, composite welding and twin-wire welding. However, they all have the disadvantages of high heat input and high energy consumption during the welding process, which affect the crystallization process and thus deteriorate the mechanical properties of the welded joint.

[0003] In recent years, magnetic control technology has been introduced into the welding field and has developed rapidly, resulting in numerous magnetic field devices and excitation equipment that can solve various welding problems and improve welding quality. However, these devices have certain limitations and cannot adapt to the needs of various welding scenarios. For example, they may only output DC or only AC, failing to simultaneously provide both functions. Because magnetic field devices are composed of wires with low impedance, they can only apply relatively low voltages, thus placing high demands on the excitation equipment. For DC power, a DC / DC converter can convert the voltage to a lower value for the magnetic field device. However, for AC power, current equipment uses transformers to reduce the voltage. If the AC frequency is high, the transformer size is acceptable; if the frequency is too low, the transformer becomes bulky, making the entire device cumbersome, thus limiting the frequency. Since a magnetic field device is essentially an inductive load, excessively high frequencies result in excessive impedance, allowing only a small current to flow through it. Therefore, AC frequencies are limited to a relatively low range.

[0004] In production, equipment frequently needs to be changed to adapt to different welding requirements, wasting a significant amount of manpower, resources, and time, severely impacting production efficiency. Furthermore, current excitation equipment is bulky, heavy, and has low energy conversion efficiency, limiting its application and making it unsuitable for more demanding welding requirements. Therefore, there is an urgent need to develop a new excitation device that can achieve both DC and AC outputs, with a wide AC frequency adjustment range, thereby solving the problems existing in current excitation equipment. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide an auxiliary welding excitation power supply and control method.

[0006] This invention employs a novel circuit topology and control method, which improves the efficiency of the excitation equipment while reducing its size, and integrates more functions on the same device.

[0007] The present invention adopts the following technical solution:

[0008] An auxiliary welding excitation power supply, comprising:

[0009] Rectifier module: Used to convert AC power into pulsating half-wave DC power;

[0010] PFC module: operates in Boost mode to convert pulsating half-wave DC power into 400V high-voltage DC power, while adjusting the phase of the AC grid input current to follow the phase of the AC grid voltage.

[0011] LLC module: used to convert 400V high-voltage DC power into high-frequency high-voltage square wave AC power, and after isolation and step-down, convert it into high-frequency low-voltage square wave AC power.

[0012] SR module: Used to convert high-frequency low-voltage square wave AC power into high-frequency pulsating DC power, and output low-voltage DC power after filtering;

[0013] Modulation module: Used to modulate low-voltage DC power into the required form of electrical energy to supply the magnetic field device;

[0014] The rectifier module, PFC module, LLC module, SR module and modulation module are connected in sequence.

[0015] Furthermore, the PFC module includes a filter inductor L1, a power switch Q1, a power diode D5, a power diode D6, and a filter capacitor C1;

[0016] The power switch Q1 is controlled by the drive signal DRIVER1, and the drive signal DRIVER1 operates in duty cycle adjustment mode. When the drive signal DRIVER1 is high, the power switch Q1 is turned on, and the current returns to the rectifier module through the filter inductor L1 and the power switch Q1. At this time, the filter inductor L1 stores energy, and the filter capacitor C1 releases energy.

[0017] When the drive signal DRIVER1 is low, the power switch Q1 is turned off, and the current returns to the rectifier module through the filter inductor L1 and the power diode D6. At this time, the filter inductor L1 releases energy, and the filter capacitor C1 stores energy.

[0018] Furthermore, the LLC module includes power switch Q2, power switch Q3, power switch Q4, power switch Q5, resonant inductor L2, magnetizing inductor L3, resonant capacitor C2, resonant capacitor C3, resonant capacitor C4, resonant capacitor C5, resonant capacitor C6, and high-frequency transformer T1;

[0019] The power switch Q2 and power switch Q4 are connected in series and are connected across the output terminal of the PFC module;

[0020] The power switch Q3 and power switch Q5 are connected in series and are connected across the output terminal of the PFC module;

[0021] The resonant capacitor C2 is connected in parallel with the power switch Q2, the resonant capacitor C3 is connected in parallel with the power switch Q3, the resonant capacitor C4 is connected in parallel with the power switch Q4, the resonant capacitor C5 is connected in parallel with the power switch Q5, and the two ends of the magnetizing inductor L3 are connected across the primary side of the high-frequency transformer T1.

[0022] The resonant inductor L2 and the resonant capacitor C6 are connected in series. One end of the resonant inductor L2 is connected between the power switch Q2 and the power switch Q4. One end of the resonant capacitor C6 is connected to one end of the magnetizing inductor L3. The other end of the magnetizing inductor L3 is connected to one end of the resonant capacitor C5.

[0023] further,

[0024] The power switches Q2, Q3, Q4, and Q5 are controlled by drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5, respectively; wherein...

[0025] The drive signal DRIVER2 of the power switch Q2 and the drive signal DRIVER4 of the power switch Q4 are complementary, and the drive signal DRIVER3 of the power switch Q3 and the drive signal DRIVER5 of the power switch Q5 are complementary.

[0026] The drive signal DRIVER2 and the drive signal DRIVER5 are the same, and the drive signal DRIVER3 and the drive signal DRIVER4 are the same;

[0027] The drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5 operate in frequency modulation mode, and their operating frequency range is limited to f. m < f s < f r ,in , This ensures that the LLC module operates in the ZVS and ZCS regions. At the same time, under the combined action of the resonant inductor L2, magnetizing inductor L3, resonant capacitors C2, C3, C4, C5, and C6, the power switch can be turned on and off at zero voltage.

[0028] Furthermore, the SR module includes a power switch Q6, a power switch Q7, a filter inductor L4, and a filter capacitor C7;

[0029] The power switch transistors Q6 and Q7 are connected to the third and sixth pins of the high-frequency transformer T1, respectively, and their other ends are connected to the filter inductor L4.

[0030] The positive terminal of the filter capacitor C7 is connected to the filter inductor L4, and its other end is connected to the fourth and fifth pins of the high-frequency transformer T1.

[0031] The drive signal DRIVER6 for power switch Q6 and the drive signal DRIVER7 for power switch Q7 operate in frequency modulation mode, specifically as follows:

[0032] When the voltage terminal of the high-frequency transformer T1 is positive, the drive signal DRIVER6 becomes high. At this time, the power switch Q6 is turned on, and electrical energy flows to the next stage through the power switch Q6, the filter inductor L4, and the filter capacitor C7.

[0033] When the voltage terminal of the high-frequency transformer T1 is negative, the drive signal DRIVER7 becomes high, and the power switch Q7 is turned on. At this time, electrical energy flows to the subsequent stage through the power switch Q7, the filter inductor L4, and the filter capacitor C7.

[0034] Furthermore, when the drive signals DRIVER2 and DRIVER5 are high, the power switches Q2 and Q5 are turned on. At this time, the current flows back to the PFC module through the power switch Q2, resonant inductor L2, resonant capacitor C6, magnetizing inductor L3, high-frequency transformer T1, and power switch Q5. At this time, the voltage of the high-frequency transformer T1 is positive at the top and negative at the bottom. When the drive signal DRIVER6 is high, the secondary current can flow through the power switch Q6.

[0035] When the drive signals DRIVER3 and DRIVER4 are high, the power switches Q3 and Q4 are turned on. At this time, the current flows back to the PFC module through the power switch Q3, the magnetizing inductor L3, the high-frequency transformer T1, the resonant capacitor C6, the resonant inductor L2, and the power switch Q4. At this time, the voltage of the high-frequency transformer T1 is positive at the bottom and negative at the top. When the drive signal DRIVER7 is high, the secondary current can flow through the power switch Q7.

[0036] Furthermore, the modulation module includes power switch Q8, power switch Q9, power switch Q10, power switch Q11, filter inductor L5, and filter capacitor C8;

[0037] Power switch Q8 and power switch Q10 are connected in series and then connected across the output of the SR module;

[0038] Power switch Q9 and power switch Q11 are connected in series and then connected across the output of the SR module;

[0039] One end of the filter inductor L5 is connected between power switch Q8 and power switch Q10, and the other end is connected to filter capacitor C8.

[0040] The other end of the filter capacitor C8 is connected between the power switch Q9 and the power switch Q11, and both ends of it are connected to the output terminal.

[0041] Furthermore, the power switches Q8, Q9, Q10, and Q11 are controlled by drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11, respectively. Specifically, drive signals DRIVER8 and DRIVER10 are complementary, drive signals DRIVER9 and DRIVER11 are complementary, drive signals DRIVER8 and DRIVER11 are identical, and drive signals DRIVER9 and DRIVER10 are identical. Moreover, drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11 operate in duty cycle adjustment mode, and the output voltage can be adjusted by regulating the duty cycle of drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11.

[0042] further,

[0043] The PFC module adopts a "voltage outer loop + current inner loop" control mode to control the PFC module output voltage to reach the set value.

[0044] A control method for the auxiliary welding excitation power supply, wherein the LLC module and SR module work together and operate in a constant voltage single-loop control mode, specifically as follows:

[0045] First, check the output voltage V of the SR module. f2 Set the voltage V of the SR module. ref2 The error value V is obtained by comparison. err2 The signal is fed into the voltage PI controller to calculate and obtain the drive signal PFM in the LLC module and SR module, and then applied to the corresponding switching transistor to control the output voltage of the LLC module to reach the set value.

[0046] Furthermore, the modulation module operates in feedforward mode, specifically as follows:

[0047] First, the output voltage V of the SR module is collected. f2 Using the target output voltage V ref3 Divide by the SR module output voltage V f2The percentage δ is obtained, and then MPWM is obtained through a waveform modulation algorithm, thereby controlling the magnitude of the drive signal in the modulation module to adjust the output.

[0048] Furthermore, the waveform modulation algorithm is specifically as follows:

[0049] The driving signals of the modulation module include driving signal DRIVER8, driving signal DRIVER9, driving signal DRIVER10 and driving signal DRIVER11;

[0050] Target output voltage V ref3 Divide by the output voltage V of the LLC+SR module f2 Obtain the percentage δ;

[0051] The percentage δ is multiplied by half the counter period value to obtain the first comparison value;

[0052] The second comparison value is obtained by adding half of the counter cycle value to the first comparison value.

[0053] The second comparison value is compared with the counter. When the counter is less than the second comparison value, the drive signals DRIVER8 and DRIVER10 output a high level. When the counter is greater than or equal to the second comparison value, the drive signals DRIVER8 and DRIVER11 output a low level.

[0054] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0055] (1) The present invention adopts a new circuit topology and control method, which effectively avoids the limitations of traditional equipment and can realize almost arbitrary power waveform output such as DC, DC pulse, AC pulse, and sinusoidal AC, and can be applied to more application scenarios;

[0056] (2) The power switching transistor of the LLC module operates in a soft-switching state, and the SR module uses a power switching transistor instead of a diode. This combination can effectively reduce the on-state voltage and on-state resistance of the power devices, significantly reduce energy loss, and improve energy conversion efficiency.

[0057] (3) The present invention uses a modulation module instead of the transformer form of other equipment, which can not only realize DC output, but also realize AC output. Furthermore, the AC frequency can be lower and the adjustment range is wider, but the size of the equipment is much smaller than that of other equipment. Attached Figure Description

[0058] Figure 1 This is a topology diagram of the main circuit of the excitation power supply of the present invention;

[0059] Figure 2This is a Simulink simulation model diagram of the excitation power supply of the present invention;

[0060] Figure 3 This is a waveform diagram of the rectifier module of the present invention.

[0061] Figure 4 This is a waveform diagram of the PFC module operation of the present invention;

[0062] Figure 5 This is a waveform diagram of the inductor operation of the PFC module of this invention;

[0063] Figure 6 This is a waveform diagram of the power switch drive signal of the LLC module of the present invention;

[0064] Figure 7 This is a waveform diagram of the soft-switching operation of the power switching transistor in the LLC module of this invention;

[0065] Figure 8 This is a waveform diagram of the high-frequency transformer operation of the LLC module of this invention;

[0066] Figure 9 This is a waveform diagram of the SR module operation of the present invention;

[0067] Figure 10 This is a waveform diagram of the power switch transistor operating in the SR module of this invention;

[0068] Figure 11 This is a waveform diagram of the modulation module of the present invention.

[0069] Figure 12 This is a block diagram of the PFC module control structure of the present invention;

[0070] Figure 13 This is a block diagram of the LLC+SR module control structure of the present invention;

[0071] Figure 14 This is a block diagram of the modulation module control structure of the present invention;

[0072] Figure 15 This is a diagram of the modulation module control algorithm of the present invention;

[0073] Figure 16 This is a verification diagram of the closed-loop control effect of the modulation module of the present invention;

[0074] Figures 17(a)-17(e) are waveform diagrams of the operation of the present invention under different forms of electrical energy. Detailed Implementation

[0075] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0076] like Figure 1As shown, an auxiliary welding excitation power supply includes a rectifier module, a PFC module, an LLC module, an SR module, and a modulation module, with each module connected in sequence.

[0077] like Figure 2 This is a schematic diagram of the model connection constructed by the present invention, and the specific description is as follows:

[0078] The rectifier module is connected to the AC power grid and includes rectifier diodes D1, D2, D3, and D4, used to convert AC power into pulsating half-wave DC power. Figure 3 As shown.

[0079] The PFC module is connected to the rectifier module and includes a filter inductor L1, a power switch Q1, power diodes D5 and D6, and a filter capacitor C1; as follows: Figure 4 As shown, the PFC module operates in Boost mode, converting pulsating half-wave DC power into 400V high-voltage DC power, while adjusting the current phase to follow the voltage phase of the AC grid, thereby reducing reactive power loss and improving power quality.

[0080] like Figure 5 As shown, the power switch Q1 is controlled by the drive signal DRIVER1, which operates in duty cycle adjustment mode. When DRIVER1 is high, the power switch Q1 is turned on, the voltage across the filter inductor L1 is positive on the left and negative on the right, and the current flows through the filter inductor L1 and the power switch Q1 back to the rectifier module. At this time, the filter inductor L1 stores energy, and the filter capacitor C1 releases energy. When DRIVER1 is low, the power switch Q1 is turned off, the voltage across the filter inductor L1 is negative on the left and positive on the right, and the current flows through the filter inductor L1 and the power diode D6 back to the rectifier module. At this time, the filter inductor L1 releases energy, and the filter capacitor C1 stores energy.

[0081] The LLC module, connected to the PFC module, includes power switching transistors Q2, Q3, Q4, and Q5, resonant inductor L2, magnetizing inductor L3, resonant capacitors C2, C3, C4, C5, and C6, and a high-frequency transformer T1.

[0082] like Figure 6As shown, power switches Q2, Q3, Q4, and Q5 are controlled by drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5, respectively. Specifically, drive signals DRIVER2 and DRIVER4 are complementary, and drive signals DRIVER3 and DRIVER5 are complementary. Drive signals DRIVER2 and DRIVER5 are identical, and drive signals DRIVER3 and DRIVER4 are identical. Furthermore, drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5 operate in frequency modulation mode, and their operating frequency range is limited to f. m < f s < f r ,in , This ensures that the LLC module operates in the ZVS and ZCS regions. Simultaneously, under the combined action of the resonant inductor L2, magnetizing inductor L3, resonant capacitors C2, C3, C4, C5, and C6, zero-voltage turn-on and turn-off of the power switch can be achieved. Figure 7 As shown.

[0083] like Figure 8 As shown, under the control of the drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5, the power switches Q2, Q3, Q4, and Q5 convert the 400V high-voltage DC power of the LLC module into high-frequency high-voltage square wave AC power. At the same time, the high-frequency transformer T1 isolates and steps down the voltage, converting it into high-frequency low-voltage square wave AC power.

[0084] The SR module is connected to the LLC module and includes power switch Q6, power switch Q7, filter inductor L4, and filter capacitor C7.

[0085] like Figure 9As shown, power switches Q6 and Q7 are controlled by drive signals DRIVER6 and DRIVER7, respectively, to convert high-frequency low-voltage square wave AC power into high-frequency pulsating DC power. Simultaneously, after filtering, low-voltage DC power is output. Drive signals DRIVER6 and DRIVER7 operate in frequency modulation mode. When the voltage of the high-frequency transformer T1 is positive at the top and negative at the bottom, drive signal DRIVER6 becomes high, and power switch Q6 is turned on. Power flows through power switch Q6, filter inductor L4, and filter capacitor C7 to the next stage. When the voltage of the high-frequency transformer T1 is positive at the bottom and negative at the top, drive signal DRIVER7 becomes high, and power switch Q7 is turned on. Power flows through power switch Q7, filter inductor L4, and filter capacitor C7 to the next stage.

[0086] Further explanation: The statement that the voltage of the high-frequency transformer T1 is positive at the top and negative at the bottom specifically means that the voltage of the high-frequency transformer T1 is positive at the same-name terminal; the statement that the voltage of the high-frequency transformer T1 is positive at the bottom and negative at the top specifically means that the voltage of the high-frequency transformer T1 is negative at the same-name terminal.

[0087] like Figure 10 As shown, the drive signals DRIVER2, DRIVER5, and DRIVER6 are the same, and the drive signals DRIVER3, DRIVER4, and DRIVER7 are the same. When drive signals DRIVER2 and DRIVER5 are high, power switches Q2 and Q5 are turned on. At this time, the current flows back to the PFC module through power switch Q2, resonant inductor L2, resonant capacitor C6, magnetizing inductor L3, high-frequency transformer T1, and power switch Q5. The voltage across high-frequency transformer T1 is positive at the top and negative at the bottom. When the drive signal DRIVER6 is high, the secondary current flows through the power switch Q6. When the drive signals DRIVER3 and DRIVER4 are high, the power switches Q3 and Q4 are turned on. At this time, the current flows back to the PFC module through the power switch Q3, magnetizing inductor L3, high-frequency transformer T1, resonant capacitor C6, resonant inductor L2, and power switch Q4. At this time, the voltage of the high-frequency transformer T1 is positive at the bottom and negative at the top. When the drive signal DRIVER7 is high, the secondary current flows through the power switch Q7.

[0088] The modulation module is connected to the SR module and includes power switches Q8, Q9, Q10, and Q11, a filter inductor L5, and a filter capacitor C8.

[0089] The power switch transistors Q6 and Q7 are connected to the third and sixth pins of the high-frequency transformer T1, respectively, and their other ends are connected to the filter inductor L4.

[0090] The positive terminal of the filter capacitor C7 is connected to the filter inductor L4, and its other end is connected to the fourth and fifth pins of the high-frequency transformer T1. The low-voltage DC power is modulated into the required form to supply the magnetic field device, such as... Figure 11 As shown.

[0091] The power switches Q8, Q9, Q10, and Q11 are controlled by drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11, respectively. Drive signals DRIVER8 and DRIVER10 are complementary, and drive signals DRIVER9 and DRIVER11 are complementary. Drive signals DRIVER8 and DRIVER11 are identical, and drive signals DRIVER9 and DRIVER10 are identical. Furthermore, drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11 operate in duty cycle adjustment mode. The output voltage can be adjusted by regulating the duty cycle of drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11.

[0092] like Figure 12 As shown, preferably, the PFC module adopts a "voltage outer loop + current inner loop" control mode. First, the output voltage V of the PFC module is acquired. f1 Set the voltage V of the PFC module to match it. ref1 The error is obtained through comparison, and the current inner loop setpoint I is obtained after passing through the voltage outer loop PI controller. g1 Then, based on the current AC voltage phase V ac1 and the current inner loop setpoint I g1 Calculate the current inner loop setpoint I ref1 And compare it with the PFC inductor current feedback value I f1 The error is compared and the duty cycle (Duty) of the drive signal DRIVER1 is obtained through the current inner loop PI controller. Then, it is applied to the power switch Q1 to control the output voltage of the PFC module to reach the set value.

[0093] like Figure 13 As shown, preferably, the LLC module and the SR module work together and operate in a constant voltage single-loop control mode. First, the output voltage V of the LLC+SR module is detected. f2Set the voltage V of the LLC+SR module. ref2 The error value V is obtained by comparison. err2 The signal is fed into the voltage PI controller to calculate the PFM of drive signals DRIVER2, DRIVER3, DRIVER4, DRIVER5, DRIVER6, and DRIVER7, which are then applied to the power switches Q2, Q3, Q4, Q5, Q6, and Q7 to control the LLC module output voltage to reach the set value.

[0094] Further explanation: LLC+SR module output voltage V f2 Its amplitude is adjusted by the LLC module, and the SR module acts as a rectifier.

[0095] like Figure 14 As shown, preferably, the modulation module operates in feedforward mode, first acquiring the output voltage V of the LLC+SR module. f2 Using the target output voltage V ref3 Divide by the output voltage V of the LLC+SR module f2 The percentage δ is obtained, and then MPWM is obtained through a waveform modulation algorithm, thereby controlling the magnitude of the drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11 to adjust the output.

[0096] like Figure 15 As shown, the specific adjustment process of the modulation module is as follows:

[0097] Target output voltage V ref3 Divide by the output voltage V of the LLC+SR module f2 Obtain the percentage δ;

[0098] The percentage δ multiplied by half the counter period value (Period / 2) yields the first comparison value Compare1;

[0099] The first comparison value Compare1 is added to half of the counter period value (Period / 2) to obtain the second comparison value Compare2;

[0100] The second comparison value Compare2 is compared with the counter CNT. When the counter CNT is less than the second comparison value Compare2, the drive signals DRIVER8 and DRIVER11 output a high level. When the counter CNT is greater than or equal to the second comparison value Compare2, the drive signals DRIVER8 and DRIVER11 output a low level.

[0101] Inverting drive signals DRIVER8 and DRIVER11 yields the output levels of drive signals DRIVER9 and DRIVER10.

[0102] In this embodiment, the drive signal is provided by a digital signal processor.

[0103] like Figure 16 As shown, the waveform modulation algorithm of the modulation module was simulated and tested using a simulation model. The test results achieved the expected requirements. The drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11 change according to the changes in the preset target electrical energy form.

[0104] Preferably, the output values ​​of the PFC module and LLC+SR module remain constant throughout the entire operation, both stable at the set value, and the form of electrical energy supplied to the magnetic field device is adjusted by the modulation module.

[0105] As shown in Figures 17(a)-17(e), preferably, a novel high-efficiency multifunctional auxiliary welding excitation power supply can achieve output of almost any form of electrical energy, including DC, DC pulse, triangular wave, AC pulse, sinusoidal AC, etc. As long as the target form of electrical energy is preset, the system can start running according to the preset target. The preset form of electrical energy can be encapsulated as a function through program setting.

[0106] It should be noted that in this invention, the PFC module can be removed while still achieving the basic functions of the invention, but in this case, the current input to the AC grid will not be able to follow the phase of the input voltage; at the same time, the LLC+SR module can be replaced with a DC / DC converter with other topologies.

[0107] This invention proposes a novel magnetically controlled power supply circuit structure that enables AC output over a wide frequency range. Currently, commercially available power supplies can only achieve a minimum frequency of 40Hz, but this circuit structure can achieve a minimum of 2Hz, with a high upper frequency limit. The limitation of current commercially available power supplies in achieving very low frequencies is that they use transformers for output regulation, allowing only higher frequency AC outputs and not DC outputs; otherwise, other circuit structures would be required. This invention, however, employs SVPWM control, enabling not only a wide frequency range of AC output from a single power supply but also DC, pulse, and other outputs, providing more comprehensive functionality. Furthermore, even at lower frequencies, this power supply does not suffer from excessive size due to transformer limitations.

[0108] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An auxiliary welding excitation power supply, characterized in that, include: Rectifier module: Used to convert AC power into pulsating half-wave DC power; LLC module: used to convert DC power into high-frequency, high-voltage square wave AC power, and then through isolation and step-down to convert it into high-frequency, low-voltage square wave AC power. SR module: Used to convert high-frequency low-voltage square wave AC power into high-frequency pulsating DC power, and output low-voltage DC power after filtering; Modulation module: Used to modulate low-voltage DC power into the required form of electrical energy to supply the magnetic field device; The rectifier module, LLC module, SR module and modulation module are connected in sequence; It also includes a PFC module, which operates in Boost mode to convert pulsating half-wave DC power into 400V high-voltage DC power, while adjusting the phase of the AC grid input current to follow the phase of the AC grid voltage and inputting it to the LLC module.

2. The auxiliary welding excitation power supply according to claim 1, characterized in that, The PFC module includes a filter inductor L1, a power switch Q1, a power diode D5, a power diode D6, and a filter capacitor C1. The power switch Q1 is controlled by the drive signal DRIVER1, and the drive signal DRIVER1 operates in duty cycle adjustment mode. When the drive signal DRIVER1 is high, the power switch Q1 is turned on, and the current returns to the rectifier module through the filter inductor L1 and the power switch Q1. At this time, the filter inductor L1 stores energy, and the filter capacitor C1 releases energy. When the drive signal DRIVER1 is low, the power switch Q1 is turned off, and the current returns to the rectifier module through the filter inductor L1 and the power diode D6. At this time, the filter inductor L1 releases energy, and the filter capacitor C1 stores energy.

3. The auxiliary welding excitation power supply according to claim 1, characterized in that, The LLC module includes power switches Q2, Q3, Q4, and Q5, resonant inductor L2, magnetizing inductor L3, resonant capacitors C2, C3, C4, C5, and C6, and a high-frequency transformer T1. The power switch Q2 and power switch Q4 are connected in series and are connected across the output terminal of the PFC module; The power switch Q3 and power switch Q5 are connected in series and are connected across the output terminal of the PFC module; The resonant capacitor C2 is connected in parallel with the power switch Q2, the resonant capacitor C3 is connected in parallel with the power switch Q3, the resonant capacitor C4 is connected in parallel with the power switch Q4, the resonant capacitor C5 is connected in parallel with the power switch Q5, and the two ends of the magnetizing inductor L3 are connected across the primary side of the high-frequency transformer T1. The resonant inductor L2 and the resonant capacitor C6 are connected in series. One end of the resonant inductor L2 is connected between the power switch Q2 and the power switch Q4. One end of the resonant capacitor C6 is connected to one end of the magnetizing inductor L3. The other end of the magnetizing inductor L3 is connected to one end of the resonant capacitor C5.

4. The auxiliary welding excitation power supply according to claim 3, characterized in that, The power switches Q2, Q3, Q4, and Q5 are controlled by drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5, respectively; wherein... The drive signal DRIVER2 of the power switch Q2 and the drive signal DRIVER4 of the power switch Q4 are complementary, and the drive signal DRIVER3 of the power switch Q3 and the drive signal DRIVER5 of the power switch Q5 are complementary. The drive signal DRIVER2 and the drive signal DRIVER5 are the same, and the drive signal DRIVER3 and the drive signal DRIVER4 are the same; The drive signals DRIVER2, DRIVER3, DRIVER4, and DRIVER5 operate in frequency modulation mode, and their operating frequency range is limited to f. m < f s < f r ,in , This ensures that the LLC module operates in the ZVS and ZCS regions. At the same time, under the combined action of the resonant inductor L2, magnetizing inductor L3, resonant capacitors C2, C3, C4, C5, and C6, the power switch can be turned on and off at zero voltage.

5. The auxiliary welding excitation power supply according to claim 3, characterized in that, The SR module includes power switch Q6, power switch Q7, filter inductor L4 and filter capacitor C7; The power switch transistors Q6 and Q7 are connected to the third and sixth pins of the high-frequency transformer T1, respectively, and their other ends are connected to the filter inductor L4. The positive terminal of the filter capacitor C7 is connected to the filter inductor L4, and its other end is connected to the fourth and fifth pins of the high-frequency transformer T1. The drive signal DRIVER6 for power switch Q6 and the drive signal DRIVER7 for power switch Q7 operate in frequency modulation mode, specifically as follows: When the voltage terminal of the high-frequency transformer T1 is positive, the drive signal DRIVER6 becomes high. At this time, the power switch Q6 is turned on, and electrical energy flows to the next stage through the power switch Q6, the filter inductor L4, and the filter capacitor C7. When the voltage terminal of the high-frequency transformer T1 is negative, the drive signal DRIVER7 becomes high, and the power switch Q7 is turned on. At this time, electrical energy flows to the subsequent stage through the power switch Q7, the filter inductor L4, and the filter capacitor C7.

6. The auxiliary welding excitation power supply according to claim 4, characterized in that, When the drive signals DRIVER2 and DRIVER5 are high, the power switches Q2 and Q5 are turned on. At this time, the current flows back to the PFC module through the power switch Q2, resonant inductor L2, resonant capacitor C6, magnetizing inductor L3, high-frequency transformer T1, and power switch Q5. At this time, the voltage of the high-frequency transformer T1 is positive at the top and negative at the bottom. When the drive signal DRIVER6 is high, the secondary current can flow through the power switch Q6. When the drive signals DRIVER3 and DRIVER4 are high, the power switches Q3 and Q4 are turned on. At this time, the current flows back to the PFC module through the power switch Q3, the magnetizing inductor L3, the high-frequency transformer T1, the resonant capacitor C6, the resonant inductor L2, and the power switch Q4. At this time, the voltage of the high-frequency transformer T1 is positive at the bottom and negative at the top. When the drive signal DRIVER7 is high, the secondary current can flow through the power switch Q7.

7. The auxiliary welding excitation power supply according to claim 1, characterized in that, The modulation module includes power switches Q8, Q9, Q10, and Q11, a filter inductor L5, and a filter capacitor C8. Power switch Q8 and power switch Q10 are connected in series and then connected across the output of the SR module; Power switch Q9 and power switch Q11 are connected in series and then connected across the output of the SR module; One end of the filter inductor L5 is connected between power switch Q8 and power switch Q10, and the other end is connected to filter capacitor C8. The other end of the filter capacitor C8 is connected between the power switch Q9 and the power switch Q11, and both ends of it are connected to the output terminal.

8. The auxiliary welding excitation power supply according to claim 7, characterized in that, The power switches Q8, Q9, Q10, and Q11 are controlled by drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11, respectively. Drive signals DRIVER8 and DRIVER10 are complementary, and drive signals DRIVER9 and DRIVER11 are complementary. Drive signals DRIVER8 and DRIVER11 are identical, and drive signals DRIVER9 and DRIVER10 are identical. Furthermore, drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11 operate in duty cycle adjustment mode. The output voltage can be adjusted by regulating the duty cycle of drive signals DRIVER8, DRIVER9, DRIVER10, and DRIVER11.

9. The auxiliary welding excitation power supply according to claim 2, characterized in that, The PFC module adopts a "voltage outer loop + current inner loop" control mode to control the PFC module output voltage to reach the set value.

10. A control method for the auxiliary welding excitation power supply according to any one of claims 1-9, characterized in that, The LLC module and SR module work together in a constant voltage single-loop control mode, specifically: First, check the output voltage V of the SR module. f2 Set the voltage V of the SR module. ref2 The error value V is obtained by comparison. err2 The signal is fed into the voltage PI controller to calculate and obtain the drive signal PFM in the LLC module and SR module, and then applied to the corresponding switching transistor to control the output voltage of the LLC module to reach the set value.

11. The control method according to claim 10, characterized in that, The modulation module operates in feedforward mode, specifically: First, the output voltage V of the SR module is collected. f2 Using the target output voltage V ref3 Divide by the SR module output voltage V f2 The percentage δ is obtained, and then MPWM is obtained through a waveform modulation algorithm, thereby controlling the magnitude of the drive signal in the modulation module to adjust the output.

12. The control method according to claim 11, characterized in that, The waveform modulation algorithm is specifically as follows: The driving signals of the modulation module include driving signal DRIVER8, driving signal DRIVER9, driving signal DRIVER10 and driving signal DRIVER11; Target output voltage V ref3 Divide by the output voltage V of the LLC+SR module f2 Obtain the percentage δ; The percentage δ is multiplied by half the counter period value to obtain the first comparison value; The second comparison value is obtained by adding half of the counter cycle value to the first comparison value. The second comparison value is compared with the counter. When the counter is less than the second comparison value, the drive signals DRIVER8 and DRIVER10 output a high level. When the counter is greater than or equal to the second comparison value, the drive signals DRIVER8 and DRIVER11 output a low level.

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