Control method and device of phase-shifted full-bridge circuit and welding machine power supply

Abstract

The present invention provides a control method and device for a phase-shifted full-bridge circuit and a welding machine power supply. The control method comprises: sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each full-bridge converter module to obtain an output voltage sampling signal and an output current sampling signal corresponding to each full-bridge converter module, respectively; calculating the phase shift angle corresponding to each full-bridge converter module based on the output voltage sampling signal and the output current sampling signal; comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switch component based on the comparison result; generating a pulse width modulation wave corresponding to each switch component based on the phase shift angle and the switching frequency to control the corresponding switch component to be turned on and off respectively; the present invention can dynamically adjust the switching frequency according to the output current, so as to achieve the control of the switch component using a lower pulse width modulation frequency when the load is small, thereby reducing electromagnetic interference.

Description

Technical Field

[0001] The present invention relates to the technical field of welding power supplies, and in particular to a control method and device for a phase-shifted full-bridge circuit and a welding power supply. Background Art

[0002] Currently, welding power supplies are trending toward higher frequencies and smaller sizes. Welding power supplies that utilize soft-switching topologies, thanks to their lower switching losses, can more easily achieve high frequencies and high efficiency. However, the electromagnetic interference (EMI) issues associated with higher frequencies can severely impact the control and sampling of digital chips within the welding power supply's phase-shifted full-bridge circuit. Furthermore, these EMI issues make soft switching difficult under light loads, while voltage spikes in switching devices caused by hard switching can further exacerbate interference at higher frequencies. Therefore, addressing the electromagnetic interference issues associated with the control of the phase-shifted full-bridge circuit in welding power supplies with higher frequencies remains a pressing issue. Summary of the Invention

[0003] In view of this, the present invention provides a control method and device for a phase-shifted full-bridge circuit and a welding machine power supply, which dynamically adjust the switching frequency according to the output current, so as to control the switching component with a lower pulse width modulation frequency when the load is small, thereby reducing electromagnetic interference.

[0004] According to one aspect of the present invention, a control method for a phase-shifted full-bridge circuit is provided. The phase-shifted full-bridge circuit is provided in a welding power supply and includes at least one full-bridge converter module. Each of the full-bridge converter modules includes at least one bridge arm, and each bridge arm includes a plurality of switch components. The control method includes the following steps:

[0005] S110, sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each of the full-bridge converter modules, and obtaining an output voltage sampling signal and an output current sampling signal corresponding to each of the full-bridge converter modules;

[0006] S120, calculating a phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal;

[0007] S130, comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switch component according to the comparison result;

[0008] S140 , generating a pulse width modulation wave corresponding to each of the switch components according to the phase shift angle and the switching frequency, so as to control the corresponding switch components to be turned on and off respectively.

[0009] Optionally, the preset hysteresis current threshold includes a preset hysteresis current lower limit; step S130 includes:

[0010] When the output current sampling signal is less than the preset hysteresis current lower limit value, the switching frequency corresponding to the switch component is reduced to a first preset frequency threshold.

[0011] Optionally, step S130 further includes:

[0012] When the output current sampling signal is less than the preset hysteresis current lower limit value, obtaining a reduction ratio of the switching frequency corresponding to the switching component;

[0013] According to the ratio of reduction of the switching frequency corresponding to the switching component, obtaining the ratio of increase of the switching period corresponding to the switching component;

[0014] According to the ratio of increase of the switching period, the dead time corresponding to each bridge arm is increased in the same ratio.

[0015] Optionally, the preset hysteresis current threshold value further includes a preset hysteresis current upper limit value; wherein the preset hysteresis current upper limit value is greater than the preset hysteresis current lower limit value; step S130 further includes:

[0016] When the output current sampling signal is greater than the preset hysteresis current upper limit value, the switching frequency corresponding to the switch component is increased to a second preset frequency threshold; wherein the second preset frequency threshold is greater than the first preset frequency threshold.

[0017] Optionally, step S120 includes:

[0018] Performing voltage error calculation based on the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result;

[0019] Performing proportional integral calculation on the first calculation result to obtain a second calculation result;

[0020] After filtering the second calculation result using a filter, a current reference signal is obtained;

[0021] performing a current error calculation based on the output current sampling signal and the current reference signal to obtain a third calculation result;

[0022] Proportional integral calculation is performed on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.

[0023] Optionally, step S120 includes:

[0024] taking the difference between the preset voltage reference signal and the output voltage sampling signal as a first calculation result;

[0025] The difference between the current reference signal and the output current sampling signal is used as a third calculation result.

[0026] Optionally, step S140 includes:

[0027] Obtaining a duty cycle corresponding to each bridge arm; wherein the duty cycles corresponding to the switch components in the same bridge arm are the same;

[0028] A pulse width modulation wave corresponding to each of the switching components is generated according to the phase shift angle, the switching frequency, and the duty cycle.

[0029] Optionally, each bridge arm includes two switch components, and the PWM waves corresponding to the switch components in each bridge arm are complementary.

[0030] Optionally, the switch components are all silicon carbide field effect transistors.

[0031] According to another aspect of the present invention, a control device for a phase-shifted full-bridge circuit is provided, for implementing any of the above control methods, comprising:

[0032] a signal sampling module for sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each of the full-bridge converter modules, and obtaining an output voltage sampling signal and an output current sampling signal corresponding to each of the full-bridge converter modules;

[0033] a phase shift angle calculation module, which calculates the phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal;

[0034] a switching frequency adjustment module, which compares the output current sampling signal with a preset hysteresis current threshold, and adjusts the switching frequency corresponding to the switching component according to the comparison result;

[0035] The pulse width modulation wave generating module generates a pulse width modulation wave corresponding to each of the switch components according to the phase shift angle and the switching frequency, so as to control the corresponding switch components to be turned on and off respectively.

[0036] Optionally, the preset hysteresis current threshold includes a preset hysteresis current lower limit; and the switching frequency adjustment module is configured to:

[0037] When the output current sampling signal is less than the preset hysteresis current lower limit value, the switching frequency corresponding to the switch component is reduced to a first preset frequency threshold.

[0038] Optionally, the switching frequency adjustment module is further configured to:

[0039] When the output current sampling signal is less than the preset hysteresis current lower limit value, obtaining a reduction ratio of the switching frequency corresponding to the switching component;

[0040] According to the ratio of reduction of the switching frequency corresponding to the switching component, obtaining the ratio of increase of the switching period corresponding to the switching component;

[0041] According to the ratio of increase of the switching period, the dead time corresponding to each bridge arm is increased in the same ratio.

[0042] Optionally, the phase shift angle calculation module includes:

[0043] a voltage error calculation unit, performing voltage error calculation according to the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result;

[0044] a first proportional-integral calculation unit, performing proportional-integral calculation on the first calculation result to obtain a second calculation result;

[0045] a current reference signal acquisition unit, configured to filter the second calculation result using a filter to obtain a current reference signal;

[0046] a current error calculation unit, performing current error calculation according to the output current sampling signal and the current reference signal to obtain a third calculation result;

[0047] The second proportional-integral calculation unit performs proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each of the full-bridge converter modules.

[0048] According to another aspect of the present invention, there is provided a welding power supply, comprising a control device for any of the above-mentioned phase-shifted full-bridge circuits.

[0049] The beneficial effects of the present invention compared with the prior art are:

[0050] The control method, device, and welding machine power supply of the phase-shifted full-bridge circuit provided by the present invention combine the output voltage sampling signal and the output current sampling signal to generate the phase shift angle of the pulse width modulation wave corresponding to each switch component in the same bridge arm, dynamically adjust the switching frequency according to the output current, and realize the use of a lower pulse width modulation frequency when the load is small. The switching components are controlled by combining the above-mentioned phase shift angle and pulse width modulation frequency, thereby achieving the purpose of reducing electromagnetic interference and improving the electromagnetic compatibility of the phase-shifted full-bridge circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are incorporated into and constitute a part of this specification, illustrate embodiments consistent with the present invention, and together with the description, serve to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and it is clear that those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0052] Figure 1 This is a structural schematic diagram of a phase-shifted full-bridge circuit disclosed in one embodiment of the present invention;

[0053] Figure 2 A schematic flow chart of a control method for a phase-shifted full-bridge circuit disclosed in one embodiment of the present invention;

[0054] Figure 3 1 is a flow chart of step S120 in a method for controlling a phase-shifted full-bridge circuit according to another embodiment of the present invention;

[0055] Figure 4 These are the main waveforms of the main circuit and control signal when the phase-shifted full-bridge circuit disclosed in one embodiment of the present invention is working.

[0056] Figure 5 A schematic diagram comparing the pulse width modulation waveforms of different transistors in the same bridge arm at different switching frequencies;

[0057] Figure 6 A schematic diagram of a specific implementation method of frequency conversion by transistors in a phase-shifted full-bridge circuit;

[0058] Figure 7 A schematic flow chart of a control method for a phase-shifted full-bridge circuit disclosed in another embodiment of the present invention;

[0059] Figure 8 A schematic structural diagram of a phase-shifted full-bridge circuit disclosed in another embodiment of the present invention;

[0060] Figure 9 A schematic diagram of a control device for a phase-shifted full-bridge circuit disclosed in one embodiment of the present invention;

[0061] Figure 10 A schematic diagram of the working principle of a control device for a phase-shifted full-bridge circuit disclosed in one embodiment of the present invention;

[0062] Figure 11 This is a structural diagram of a phase shift angle calculation module in a control device for a phase shift full-bridge circuit disclosed in one embodiment of the present invention;

[0063] Figure 12 The figure is a schematic structural diagram of a welding power supply disclosed in one embodiment of the present invention. DETAILED DESCRIPTION

[0064] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention will be comprehensive and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure can be practiced without one or more of the specific details, or other methods, materials, devices, etc. may be adopted. In other cases, well-known technical solutions are not shown or described in detail to avoid blurring various aspects of the present disclosure. The same reference numerals in the figures represent the same or similar structures, and their detailed descriptions will be omitted.

[0065] The terms "a," "an," "the," "said," and "at least one" are used to indicate the presence of one or more elements / components / etc.; the terms "including," "having," and "having" are used to express an open-ended inclusive meaning and mean that additional elements / components / etc. may be present in addition to the listed elements / components / etc.

[0066] The present invention discloses a control method for a phase-shifted full-bridge circuit. The phase-shifted full-bridge circuit is provided in a welding power supply and includes at least one full-bridge converter module. Each full-bridge converter module includes at least one bridge arm. Each bridge arm includes multiple switch components.

[0067] like Figure 1 As shown, one embodiment of the present invention discloses a phase-shifted full-bridge circuit. The circuit includes only one full-bridge converter module. The full-bridge converter module includes two bridge arms. Each bridge arm includes two switch assemblies. In this embodiment, the switch assemblies are MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). In other embodiments, the switch assemblies may also be other devices, which is not limited by this application.

[0068] Furthermore, in this embodiment, the switch assembly is a silicon carbide (SiC) MOSFET. Specifically, due to specialized process requirements, welding power supplies require high current and power. Currently, silicon rectifier and thyristor rectifier power supplies are commonly used. While they offer excellent reliability and are technologically mature, these devices are bulky, heavy, energy-intensive, and inefficient. Furthermore, due to structural factors, their dynamic and static characteristics are less than ideal. The current market is placing new demands on welding power supplies for welding performance, size, and efficiency.

[0069] As a third-generation wide-bandgap semiconductor material, SiC has proven its superior performance and extremely high efficiency. The extremely low switching losses of SiC power devices facilitate the high-frequency operation of welding power supplies. Higher frequencies mean better welding performance and higher power density. Due to the reduced output current ripple, the output inductance also decreases, resulting in a faster dynamic response of the output current and enabling more precise control compared to conventional welding machines. Smaller capacitance and inductance also facilitate miniaturization of the welding machine. Therefore, in this embodiment, the use of silicon carbide MOSFETs facilitates both high-frequency operation and miniaturization of the welding power supply.

[0070] refer to Figure 1 In this embodiment, the PWM (pulse width modulation) waves corresponding to the switch components in each bridge arm are complementary. The full-bridge converter module includes a first transistor S1, a second transistor S2, a third transistor S3, and a fourth transistor S4. The first transistor S1 and the third transistor S3 are connected in series to form a first bridge arm. The first transistor S1 and the third transistor S3 are complementary and conductive. The second transistor S2 and the fourth transistor S4 are connected in series to form a second bridge arm. The second transistor S2 and the fourth transistor S4 are complementary and conductive. In addition, the first bridge arm is turned on before the second bridge arm.

[0071] Continue to refer Figure 1 The above phase-shifted full-bridge circuit further includes a first inductor L r1 , transformer T1, first transformer CT1, first capacitor C1, first diode D1, second diode D2, second inductor L2, third diode Q1, fourth diode Q2, fifth diode Q3, sixth diode Q4, and second transformer CS1. The first diode D1 and second diode D2 are connected in series. The third diode Q1 and fifth diode Q3 are connected in series. The fourth diode Q2 and sixth diode Q4 are connected in series. The first end of the second inductor L2 is connected between the first transistor S1 and the third transistor S3. The first capacitor C1 is connected between the second end of the second inductor L2 and the first transformer CT1. The first transformer CT1 is connected to the primary side of transformer T1. The primary side of transformer T1 is also connected between the second transistor S2 and the fourth transistor S4. The secondary side of transformer T1 is connected between the third diode Q1 and the fifth diode Q3, and between the fourth diode Q2 and the sixth diode Q4, respectively.

[0072] The input end of the phase-shift full-bridge circuit is connected to the output end of the PFC circuit of the welding power supply, and the positive electrode V O + With negative V O- There is a welding workpiece N1 between them. The connection relationship between the various components in the above phase-shifted full-bridge circuit can be referred to Figure 1 As shown, this embodiment will not be described in detail.

[0073] like Figure 2 As shown, an embodiment of the present invention discloses a control method for a phase-shifted full-bridge circuit. The control method includes the following steps:

[0074] S110 , sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each full-bridge converter module to obtain an output voltage sampling signal and an output current sampling signal corresponding to each full-bridge converter module, respectively.

[0075] Specifically, Figure 1 For example, the output voltage of the phase-shifted full-bridge circuit is the voltage between the positive and negative poles of the output terminal. Figure 1 The phase-shifted full-bridge circuit in FIG. 1 has only one full-bridge converter module, so the output current described above is the output current of the full-bridge converter module. Sampling of the output current and output voltage can be achieved through differential sampling. The specific implementation process of sampling can be referenced to existing technologies and will not be further described in this embodiment.

[0076] When the phase-shifted full-bridge circuit has two or more full-bridge converter modules, the output current of each full-bridge converter module is sampled separately to obtain an output current sampling signal associated with each full-bridge converter module.

[0077] S120 , calculating and obtaining a phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal.

[0078] When implementing it specifically, Figure 3 As shown, step S120 includes:

[0079] S121: Perform a voltage error calculation based on the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result. In this step, the difference between the preset voltage reference signal and the output voltage sampling signal is used as the first calculation result. That is, the voltage error calculation is based on the difference between the preset voltage reference signal and the output voltage sampling signal.

[0080] S122, performing proportional integral calculation on the first calculation result to obtain a second calculation result.

[0081] S123 , filtering the second calculation result using a filter to obtain a current reference signal.

[0082] S124: Calculate a current error based on the output current sampling signal and the current reference signal to obtain a third calculation result. In this step, the difference between the current reference signal and the output current sampling signal is used as the third calculation result. That is, the current error is calculated as the difference between the current reference signal and the output current sampling signal.

[0083] S125 , performing proportional integral calculation on the third calculation result to obtain a phase shift angle corresponding to each of the full-bridge converter modules.

[0084] The above-mentioned step S122 is to perform PI (proportional integral) calculation on the difference between the preset voltage reference signal and the output voltage sampling signal. The second calculation result can then be filtered using a first-order low-pass filter to obtain a current reference signal. Since the output current of the same full-bridge converter module is the same, the phase shift angle calculated by the same full-bridge converter module is also the same. The phase shift angle corresponding to each bridge arm in the same full-bridge converter module is the same. The phase shift angle is the phase difference between the PWM waves corresponding to each transistor under the same bridge arm generated subsequently.

[0085] Therefore, step S120 is to first perform voltage loop PI calculation and then perform current loop PI calculation. The specific implementation process of PI calculation can be implemented with reference to the existing technology and will not be described in detail in this embodiment.

[0086] S130: Compare the output current sampling signal with a preset hysteresis current threshold, and adjust the switching frequency corresponding to the switch component based on the comparison result. The switching frequency of all switch components in the same full-bridge converter module is the same. The preset hysteresis current threshold includes a preset hysteresis current upper limit and a preset hysteresis current lower limit. The preset hysteresis current upper limit is greater than the preset hysteresis current lower limit.

[0087] In this step, when the output current sampling signal is less than the preset hysteresis current lower limit, the switching frequency corresponding to the switch component is reduced to a first preset frequency threshold. When the output current sampling signal is less than the preset hysteresis current lower limit, it indicates that the welder is in a light-load state. When the welder is operating at no load, it is also in a light-load state.

[0088] Frequency reduction under light load conditions offers numerous benefits. First, it allows for a longer dead time, thereby increasing the soft-switching power range. Second, frequency reduction reduces the noise generated by the transistors per unit time, significantly reducing electromagnetic interference (EMI) caused by hard switching and improving the electromagnetic compatibility (EMC) of the phase-shifted full-bridge circuit.

[0089] For example, the first preset frequency threshold may be 75 kHz, and the preset hysteresis current lower limit may be 100 A, which is not limited in the present application.

[0090] Specifically, Figure 4 The main waveforms of the main circuit and control signal when the phase-shifted full-bridge circuit is working are shown. Figure 4 ,i L Represents the oscillating current of the primary side of the transformer, u h1 Indicates the primary voltage of the transformer, u h2 Indicates the secondary voltage of the transformer. Figure 4 in u h2 The shaded portion indicates that no voltage is output during the corresponding time period. Figure 4 The control signal waveform shown in FIG is a pulse width modulation waveform corresponding to the PWM wave used to control each transistor. in U represents the input voltage of the phase-shifted full-bridge circuit. K represents the turns ratio between the primary and secondary sides of the transformer. in / K means U in The ratio between K and .

[0091] In the time period from t0 to t1, transistor S1 is turned off, and the primary resonant current charges the body capacitance of transistor S1 and discharges the body capacitance of transistor S3 until the voltage between the drain and source of transistor S3 drops to zero. This process must be completed within the dead time, otherwise it will cause the zero voltage turn-on of transistor S3 to fail, resulting in turn-on loss. In other words, it takes time to charge and discharge the capacitor, and soft switching can only be achieved if the capacitor charging and discharging is completed within the specified dead time. Therefore, to achieve soft switching, it is necessary to speed up the capacitor charging and discharging time and / or extend the dead time. Among them, the dead time refers to the time period when the two transistors in the same bridge arm are in the off state at the same time.

[0092] As can be seen from this, the primary current and deadband significantly influence the soft-switching capability of a phase-shifted full-bridge circuit. The higher the power, the greater the primary current, and the faster the switch capacitance charges and discharges, the easier it is for the converter to achieve soft-switching. A longer deadband allows for more time for the capacitor to charge and discharge, making soft-switching easier.

[0093] Therefore, when the power is low, that is, the output current is low, the dead time needs to be increased to expand the soft-open power range. However, an excessively large dead time will result in a loss of effective duty cycle, and too low a no-load voltage will increase the probability of arc ignition failure. However, if the switching period and the dead time are increased at the same ratio, the duty cycle loss caused by the dead time will remain the same at different switching frequencies. Therefore, reducing the switching frequency at light loads can effectively solve this problem.

[0094] Switching power supplies pursue high frequencies primarily to reduce inductance and capacitance parameters, thereby reducing the size of the converter (i.e., the phase-shifted full-bridge circuit), increasing power density, and facilitating miniaturization of the switching power supply. With smaller inductance and capacitance parameters, reducing the switching frequency increases current and voltage ripple in the circuit, leading to increased stress on the switching transistor and saturation of magnetic components. However, reducing the switching frequency when the welder is lightly loaded does not cause this problem. Since the welder power supply itself is relatively low power, even if the ripple increases, it will not exceed a safe range.

[0095] Figure 5 The figure shows a comparison of the pulse width modulation waveforms of the same bridge arm at different switching frequencies, showing the pulse width modulation waveforms of the first transistor S1 and the third transistor S3 in the first bridge arm at a frequency of 75kHz and a frequency of 150kHz. Figure 5 The horizontal axis represents time t.

[0096] Figure 6 The figure shows a schematic diagram of switching the switching frequency of the transistor. In order to ensure the stable operation of the phase-shifted full-bridge circuit, in this embodiment, hysteresis control is adopted when switching the frequency. The output current is used as the switching condition. When the output current i is greater than the hysteresis upper limit I up_lim That is, when the hysteresis current upper limit is preset, the low frequency, i.e., the first preset frequency threshold, is switched to the high frequency, i.e., the second preset frequency threshold; for example, the low frequency 75kHz is switched to the high frequency 150kHz. When the output current i is less than the hysteresis lower limit I low_lim That is, when the lower limit of the hysteresis current is preset, the high frequency 150kHz is switched to the low frequency 75kHz. max Indicates the maximum output current of the circuit. Figure 6 The change of the pulse width modulation waveform generated after the frequency conversion is also shown.

[0097] S140, generating a pulse width modulation wave corresponding to each of the above-mentioned switching components according to the above-mentioned phase shift angle and the above-mentioned switching frequency, so as to control the corresponding switching components to be turned on and off respectively. In specific implementation, this step may include:

[0098] Obtaining the duty cycle corresponding to each bridge arm. The duty cycles corresponding to the switch components in the same bridge arm are the same. Then, generating a pulse width modulation wave corresponding to each of the switch components based on the phase shift angle, the switching frequency, and the duty cycle.

[0099] The duty cycle can be preset, for example, 50%. The switching frequency is the frequency of the PWM wave. In this case, the step is to generate a pulse width modulation wave according to the phase shift angle, the switching frequency, and the preset duty cycle.

[0100] In this embodiment, this step calculates and generates two control signals, each of which includes two complementary PWM waves. Each control signal is used to control two transistors in the same bridge arm. Each PWM wave is used to control the conduction or disconnection of a transistor.

[0101] In other embodiments, in step S130, when the output current sampling signal is greater than the preset hysteresis current upper limit, the switching frequency corresponding to the switch component is increased to a second preset frequency threshold, wherein the second preset frequency threshold is greater than the first preset frequency threshold.

[0102] In some embodiments, when the output current sampling signal is between a preset hysteresis current lower limit value and a preset hysteresis current upper limit value, the corresponding switching frequency may remain unchanged or may also be switched to the second preset frequency threshold.

[0103] For example, the second preset frequency threshold may be 150 kHz, the preset hysteresis current lower limit may be 100 A, and the preset hysteresis current upper limit may be 150 A, which is not limited in the present application.

[0104] In another embodiment of the present application, another control method of the phase-shifted full-bridge circuit is disclosed. Figure 7 As shown in the above Figure 2 Based on the corresponding embodiment, step S130 further includes:

[0105] S131, when the output current sampling signal is less than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component, and obtaining the ratio of the switching frequency reduction.

[0106] S132 , obtaining an increase ratio of the switching period corresponding to the switching component according to a decrease ratio of the switching frequency corresponding to the switching component.

[0107] S133 , according to the ratio of the increase of the switching period, increase the dead time corresponding to each bridge arm by the same ratio.

[0108] That is, the dead time corresponding to each bridge arm is increased at the same ratio as the switching period is increased.

[0109] Let's take an example. For example, when the transistor's switching frequency switches from a high frequency of 150kHz to a low frequency of 75kHz, the reduction ratio is 1 / 2. Therefore, the increase ratio of the switching period is the inverse of 1 / 2, or 2. Therefore, the dead time corresponding to each bridge arm in this circuit is also doubled.

[0110] Because excessive dead time can lead to loss of effective duty cycle, resulting in excessively low no-load voltage and an increased probability of arc ignition failure, this embodiment increases the switching period and dead time by the same proportion. This ensures that the duty cycle loss caused by the dead time remains the same at different switching frequencies, thus solving this problem.

[0111] like Figure 8 As shown, another embodiment of the present invention discloses a phase-shifted full-bridge circuit and a connected PFC (Power Factor Corrector) circuit. The circuit includes two parallel full-bridge converter modules, namely, a first full-bridge converter module 81 and a second full-bridge converter module 82 in parallel. The specific structures of the first full-bridge converter module 81 and the second full-bridge converter module 82 can be referred to. Figure 8 As shown, this embodiment will not be described in detail.

[0112] When the phase-shifted full-bridge circuit in this figure is controlled using the control method disclosed in the above embodiment, it is necessary to sample the output current of each of the two full-bridge converter modules 81, generate corresponding output current sampling signals, and then calculate the corresponding phase shift angle for each of the two full-bridge converter modules 81. This then generates the corresponding pulse-width modulated waves. During this calculation process, the reference output voltage sampling signals of the two full-bridge converter modules 81 are identical.

[0113] like Figure 9 As shown, another embodiment of the present invention discloses a control device for a phase-shifted full-bridge circuit. The device includes:

[0114] The signal sampling module 91 samples the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each of the full-bridge converter modules, and obtains an output voltage sampling signal and an output current sampling signal corresponding to each of the full-bridge converter modules.

[0115] The phase shift angle calculation module 92 calculates the phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal.

[0116] The switching frequency adjustment module 93 compares the output current sampling signal with a preset hysteresis current threshold, and adjusts the switching frequency corresponding to the switching component according to the comparison result.

[0117] The pulse width modulation wave generating module 94 generates a pulse width modulation wave corresponding to each of the switching components according to the phase shift angle and the switching frequency, so as to control the corresponding switching component to be turned on and off respectively.

[0118] Specifically, Figure 1For example, the output voltage of the phase-shifted full-bridge circuit is the voltage between the positive and negative poles of the output terminal. Figure 1 The phase-shifted full-bridge circuit in FIG. 1 has only one full-bridge converter module, so the output current described above is the output current of the full-bridge converter module. Sampling of the output current and output voltage can be achieved through differential sampling. The specific implementation process of sampling can be referenced to existing technologies and will not be further described in this embodiment.

[0119] The phase shift angle calculation module first performs voltage loop PI calculation based on the output voltage sampling signal, and then performs current loop PI calculation based on the output current sampling signal. The specific implementation process of PI calculation can be achieved by referring to the existing technology, and will not be repeated in this embodiment.

[0120] When the phase-shifted full-bridge circuit has two or more full-bridge converter modules, the output current of each full-bridge converter module is sampled separately to obtain an output current sampling signal associated with each full-bridge converter module.

[0121] The switching frequencies of all switch components in the same full-bridge converter module are the same. The preset hysteresis current threshold value includes a preset hysteresis current upper limit value and a preset hysteresis current lower limit value. The preset hysteresis current upper limit value is greater than the preset hysteresis current lower limit value.

[0122] When the output current sampling signal is less than the preset hysteresis current lower limit, the switching frequency adjustment module reduces the switching frequency corresponding to the switching component to a first preset frequency threshold. When the output current sampling signal is less than the preset hysteresis current lower limit, it indicates that the welder is in a light-load state. When the welder is operating at no load, it is also in a light-load state.

[0123] Frequency reduction under light load conditions offers numerous benefits. First, it allows for a longer dead time, thereby increasing the soft-switching power range. Second, frequency reduction reduces the noise generated by the transistors per unit time, significantly reducing electromagnetic interference (EMI) caused by hard switching and improving the electromagnetic compatibility (EMC) of the phase-shifted full-bridge circuit.

[0124] For example, the first preset frequency threshold may be 75 kHz, and the preset hysteresis current lower limit may be 100 A, which is not limited in the present application.

[0125] For a phase-shifted full-bridge circuit with only one full-bridge converter module, the pulse-width modulation wave generation module calculates and generates two control signals, each consisting of two complementary PWM waves. Each control signal is used to control two transistors in the same bridge arm. Each pulse-width modulation wave is used to turn a transistor on or off.

[0126] It can be understood that the control device of the phase-shifted full-bridge circuit of the present invention also includes other existing functional modules that support the operation of the control device of the phase-shifted full-bridge circuit. Figure 9 The control device of the phase-shifted full-bridge circuit shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present invention.

[0127] The control device of the phase-shifted full-bridge circuit in this embodiment is used to implement the above-mentioned method of controlling the phase-shifted full-bridge circuit. Therefore, the specific implementation steps of the control device of the phase-shifted full-bridge circuit can refer to the above-mentioned description of the method of controlling the phase-shifted full-bridge circuit, and will not be repeated here.

[0128] In some embodiments, in the above Figure 9 Based on the corresponding embodiment, the switching frequency adjustment module includes:

[0129] The first ratio acquisition unit is configured to acquire a ratio of reduction of the switching frequency corresponding to the switching component when the output current sampling signal is less than the preset hysteresis current lower limit value.

[0130] The second ratio acquisition unit acquires the increase ratio of the switching period corresponding to the switching component according to the decrease ratio of the switching frequency corresponding to the switching component.

[0131] The dead time increasing unit increases the dead time corresponding to each of the bridge arms in the same proportion as the increase in the switching period.

[0132] Let's take an example. For example, when the transistor's switching frequency switches from a high frequency of 150kHz to a low frequency of 75kHz, the reduction ratio is 1 / 2. Therefore, the increase ratio of the switching period is the inverse of 1 / 2, or 2. Therefore, the dead time corresponding to each bridge arm in this circuit is also doubled.

[0133] Because excessive dead time can lead to loss of effective duty cycle, resulting in too low no-load voltage and an increased probability of arc ignition failure, this embodiment increases the switching period and dead time in the same proportion. This ensures that the duty cycle loss caused by the dead time remains the same at different switching frequencies, thus solving this problem.

[0134] In other embodiments, when the output current sampling signal is greater than the preset hysteresis current upper limit, the switching frequency corresponding to the switch component is increased to a second preset frequency threshold, wherein the second preset frequency threshold is greater than the first preset frequency threshold.

[0135] In some embodiments, when the output current sampling signal is between a preset hysteresis current lower limit value and a preset hysteresis current upper limit value, the corresponding switching frequency may remain unchanged or may also be switched to the second preset frequency threshold.

[0136] For example, the second preset frequency threshold may be 150 kHz, and the preset hysteresis current upper limit may be 150 A, which is not limited in the present application.

[0137] Figure 10 The working principle of the control device of the above-mentioned phase-shifted full-bridge circuit is shown in FIG. Figure 10 As shown, the preset voltage reference signal V is calculated ref And the output voltage sampling signal V o The difference between them is then used to determine the preset voltage reference signal V ref And the output voltage sampling signal V o The difference between the two is calculated by PI (proportional integral). Then the second calculation result can be filtered using a first-order low-pass filter to obtain the current reference signal I ref Calculate the current reference signal I ref With the above output current sampling signal I o The difference between the current reference signal I ref With the above output current sampling signal I o The difference between the two is subjected to a PI proportional integral calculation to obtain a phase shift angle corresponding to each full-bridge converter module, which is then transmitted to a pulse-width modulation wave generation module. The pulse-width modulation wave generation module generates a pulse-width modulation wave corresponding to each switching component based on the phase shift angle and the switching frequency, thereby controlling the corresponding switching component to be turned on and off.

[0138] refer to Figure 10 The pulse width modulation wave generation module generates PWM waves, which correspond to the control transistors S1 to S4 respectively.

[0139] Figure 11 The structure of a phase-shift angle calculation module in a control device of a phase-shifted full-bridge circuit is shown.

[0140] In this embodiment, the phase shift angle calculation module 92 includes:

[0141] The voltage error calculation unit 921 performs voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result.

[0142] The first proportional-integral calculation unit 922 performs proportional-integral calculation on the first calculation result to obtain a second calculation result.

[0143] The current reference signal acquisition unit 923 filters the second calculation result using a filter to obtain a current reference signal.

[0144] The current error calculation unit 924 performs current error calculation according to the output current sampling signal and the current reference signal to obtain a third calculation result.

[0145] The second proportional-integral calculation unit 925 performs proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.

[0146] like Figure 12 As shown, one embodiment of the present invention discloses a welding power supply. The welding power supply includes a control device 33 for a phase-shifted full-bridge circuit disclosed in any of the above embodiments. The detailed structural features and advantages of the control device for the phase-shifted full-bridge circuit can be found in the description of the above embodiments and will not be repeated here.

[0147] refer to Figure 12 The welding power supply also includes an EMI suppression module 31, a PFC circuit 25, a PFC control device 26, a phase-shifted full-bridge circuit 32, a high-frequency transformer 34, a rectifier module 35, an auxiliary power supply 36, and a fan 37. Among them, the EMI suppression module is connected to the power grid, and the rectifier module is connected to the welding load. The connection relationship between the EMI suppression module, the PFC circuit, the PFC control device, the phase-shifted full-bridge inverter circuit, the control device of the phase-shifted full-bridge circuit, the high-frequency transformer, the rectifier module, the auxiliary power supply, and the fan can be referred to. Figure 12 , this embodiment will not be described in detail.

[0148] In summary, the control method, device, and welding power supply of the phase-shifted full-bridge circuit of the present invention have at least the following advantages:

[0149] The control method, device, and welding machine power supply of the phase-shifted full-bridge circuit disclosed in the embodiments of the present invention combine the output voltage sampling signal and the output current sampling signal to generate the phase shift angle of the pulse width modulation wave corresponding to each switch component in the same bridge arm, dynamically adjust the switching frequency according to the output current, and achieve the use of a lower pulse width modulation frequency when the load is small. The switching components are controlled by combining the above-mentioned phase shift angle and pulse width modulation frequency, thereby achieving the purpose of reducing electromagnetic interference and improving the electromagnetic compatibility of the phase-shifted full-bridge circuit.

[0150] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A control method for a phase-shifted full-bridge circuit, characterized in that: The phase-shifted full-bridge circuit is provided in a welding power supply and includes at least one full-bridge converter module. Each of the full-bridge converter modules includes at least one bridge arm, and each bridge arm includes a plurality of switch components. The control method includes the following steps: S110, sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each of the full-bridge converter modules, and obtaining an output voltage sampling signal and an output current sampling signal corresponding to each of the full-bridge converter modules; S120, calculating a phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal; S130, comparing the output current sampling signal with a preset hysteresis current threshold value including a preset hysteresis current lower limit value; when the output current sampling signal is less than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component to a first preset frequency threshold value, and obtaining a reduction ratio of the switching frequency corresponding to the switching component; According to the ratio of reduction of the switching frequency corresponding to the switching component, obtaining the ratio of increase of the switching period corresponding to the switching component; According to the ratio of the increase of the switching period, the dead time corresponding to each bridge arm is increased in the same ratio; S140 , generating a pulse width modulation wave corresponding to each of the switch components according to the phase shift angle and the switching frequency, so as to control the corresponding switch components to be turned on and off respectively.

2. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein: The preset hysteresis current threshold value further includes a preset hysteresis current upper limit value; wherein the preset hysteresis current upper limit value is greater than the preset hysteresis current lower limit value; step S130 further includes: When the output current sampling signal is greater than the preset hysteresis current upper limit value, the switching frequency corresponding to the switch component is increased to a second preset frequency threshold; wherein the second preset frequency threshold is greater than the first preset frequency threshold.

3. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein: Step S120 includes: Performing voltage error calculation based on the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result; Performing proportional integral calculation on the first calculation result to obtain a second calculation result; After filtering the second calculation result using a filter, a current reference signal is obtained; performing a current error calculation based on the output current sampling signal and the current reference signal to obtain a third calculation result; Proportional integral calculation is performed on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.

4. The control method of the phase-shifted full-bridge circuit according to claim 3, wherein: Step S120 includes: taking the difference between the preset voltage reference signal and the output voltage sampling signal as a first calculation result; The difference between the current reference signal and the output current sampling signal is used as a third calculation result.

5. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein: Step S140 includes: Obtaining a duty cycle corresponding to each bridge arm; wherein the duty cycles corresponding to the switch components in the same bridge arm are the same; A pulse width modulation wave corresponding to each of the switching components is generated according to the phase shift angle, the switching frequency, and the duty cycle.

6. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein: Each bridge arm includes two switch components, and the PWM waves corresponding to the switch components in each bridge arm are complementary.

7. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein: The switch components are all silicon carbide field effect transistors.

8. A control device for a phase-shifted full-bridge circuit, used to implement the control method according to claim 1, characterized in that: include: a signal sampling module for sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each of the full-bridge converter modules, and obtaining an output voltage sampling signal and an output current sampling signal corresponding to each of the full-bridge converter modules; a phase shift angle calculation module, which calculates the phase shift angle corresponding to each of the full-bridge converter modules according to the output voltage sampling signal and the output current sampling signal; a switching frequency adjustment module, which compares the output current sampling signal with a preset hysteresis current threshold, and adjusts the switching frequency corresponding to the switching component according to the comparison result; The pulse width modulation wave generating module generates a pulse width modulation wave corresponding to each of the switch components according to the phase shift angle and the switching frequency, so as to control the corresponding switch components to be turned on and off respectively.

9. The control device according to claim 8, wherein: The preset hysteresis current threshold value includes a preset hysteresis current lower limit value; the switching frequency adjustment module is used to: When the output current sampling signal is less than the preset hysteresis current lower limit value, the switching frequency corresponding to the switch component is reduced to a first preset frequency threshold.

10. The control device according to claim 9, characterized in that The switching frequency adjustment module is further configured to: When the output current sampling signal is less than the preset hysteresis current lower limit value, obtaining a reduction ratio of the switching frequency corresponding to the switching component; According to the ratio of reduction of the switching frequency corresponding to the switching component, obtaining the ratio of increase of the switching period corresponding to the switching component; According to the ratio of increase of the switching period, the dead time corresponding to each bridge arm is increased in the same ratio.

11. The control device according to claim 8, wherein The phase shift angle calculation module includes: a voltage error calculation unit, performing voltage error calculation according to the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result; a first proportional-integral calculation unit, performing proportional-integral calculation on the first calculation result to obtain a second calculation result; a current reference signal acquisition unit, configured to filter the second calculation result using a filter to obtain a current reference signal; a current error calculation unit, performing current error calculation according to the output current sampling signal and the current reference signal to obtain a third calculation result; The second proportional-integral calculation unit performs proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each of the full-bridge converter modules.

12. A welding power supply, characterized in that: A control device comprising the phase-shifted full-bridge circuit according to any one of claims 8 to 11.

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