CN115430885A - Control method and device of phase-shifted full-bridge circuit and welding machine power supply - Google Patents

Abstract

The invention provides a control method and a device of a phase-shifted full-bridge circuit and a welding machine power supply, wherein the control method comprises the following steps: sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each full-bridge converter module to respectively obtain an output voltage sampling signal and an output current sampling signal corresponding to each full-bridge converter module; calculating to obtain a phase shift angle corresponding to each full-bridge converter module according to 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 switching component according to the comparison result; generating a pulse width modulation wave corresponding to each switching component according to the phase shift angle and the switching frequency so as to respectively control the corresponding switching components to be switched on and switched off; the invention can dynamically adjust the switching frequency according to the output current, and realize that the switching component is controlled by adopting lower pulse width modulation frequency when the load is smaller, thereby reducing the electromagnetic interference.

Description

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

technical field

The invention relates to the technical field of welding machine power supplies, in particular to a control method and device for a phase-shifting full-bridge circuit and a welding machine power supply.

Background technique

At present, the welding power supply is developing towards high frequency and miniaturization, and the welding power supply using soft switching topology can more easily achieve high frequency and high efficiency by virtue of its lower switching loss. However, the EMI (Electromagnetic Interference, electromagnetic interference) problem brought about by high frequency will seriously affect the control and sampling of the digital chip in the phase-shifting full-bridge circuit of the welding machine power supply. Not only that, the above-mentioned EMI problem will also cause the welding machine to It is difficult to realize soft switching under load, and the interference caused by the voltage spike of the switching device caused by hard switching will be more serious at high frequencies. Therefore, how to solve the problem of electromagnetic interference caused by the control of the phase-shifting full-bridge circuit after the high frequency of the welding machine power supply is a problem that is currently faced.

Contents of the invention

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 adjusts the switching frequency according to the output current, and realizes the use of a lower pulse width modulation frequency to control the switching component when the load is small. Thereby reducing electromagnetic interference.

According to one aspect of the present invention, a control method of a phase-shifting full-bridge circuit is provided, the phase-shifting full-bridge circuit is arranged in a welding machine power supply, and includes at least one full-bridge converter module, each of the full-bridge converters The module includes at least one bridge arm, and each bridge arm includes a plurality of switch assemblies; 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 output voltage sampling signals and output current sampling signals corresponding to each of the full-bridge converter modules, respectively ;

S120. According to the output voltage sampling signal and the output current sampling signal, calculate and obtain a phase shift angle corresponding to each of the full-bridge converter modules;

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

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

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

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

Optionally, step S130 also includes:

When the output current sampling signal is smaller than the preset hysteresis current lower limit value, obtain a reduction ratio of the switching frequency corresponding to the switching component;

Acquiring the increasing ratio of the switching cycle corresponding to the switching component according to the decreasing ratio of the switching frequency corresponding to the switching component;

According to the increase ratio of the switching period, the dead time corresponding to each of the bridge arms is increased in the same proportion.

Optionally, the preset hysteresis current threshold further includes a preset hysteresis current upper limit; wherein, the preset hysteresis current upper limit is greater than the preset hysteresis current lower limit; step S130 also include:

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.

Optionally, step S120 includes:

performing voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result;

performing a proportional integral calculation on the first calculation result to obtain a second calculation result;

Obtaining a current reference signal after filtering the second calculation result by using a filter;

performing current error calculation according to 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.

Optionally, step S120 includes:

using 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.

Optionally, step S140 includes:

Obtain the duty ratio corresponding to each bridge arm; wherein, the duty ratios corresponding to the switching components in the same bridge arm are the same;

According to the phase shift angle, the switching frequency and the duty ratio, a pulse width modulation wave corresponding to each of the switching components is generated.

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

Optionally, the switch components are silicon carbide field effect transistors.

According to another aspect of the present invention, a control device for a phase-shifted full-bridge circuit is provided, which is used to implement any of the above control methods, including:

The signal sampling module 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 the output voltage sampling signal and the output current corresponding to each of the full-bridge converter modules sampling signal;

The phase-shift angle calculation module calculates the phase-shift angle corresponding to each full-bridge converter module according to the output voltage sampling signal and the output current sampling signal;

The switching frequency adjustment module 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 switching components according to the phase shift angle and the switching frequency, so as to respectively control the corresponding switching components to be turned on and off.

Optionally, the preset hysteresis current threshold includes a preset hysteresis current lower limit; the switching frequency adjustment module is used for:

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

Optionally, the switching frequency adjustment module is also used for:

When the output current sampling signal is smaller than the preset hysteresis current lower limit value, obtain a reduction ratio of the switching frequency corresponding to the switching component;

Acquiring the increasing ratio of the switching cycle corresponding to the switching component according to the decreasing ratio of the switching frequency corresponding to the switching component;

According to the increase ratio of the switching period, the dead time corresponding to each of the bridge arms is increased in the same proportion.

Optionally, the phase shift angle calculation module includes:

The voltage error calculation unit performs voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result;

The first proportional-integral calculation unit performs proportional-integral calculation on the first calculation result to obtain a second calculation result;

The current reference signal acquisition unit obtains the current reference signal after filtering the second calculation result by using a filter;

The current error calculation unit performs 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 full-bridge converter module.

According to another aspect of the present invention, there is provided a welding machine power supply, including a control device for any phase-shifting full-bridge circuit described above.

The beneficial effect of the present invention compared with prior art is:

The control method and device of the phase-shifting full-bridge circuit provided by the present invention, and the power supply of the welding machine generate the phase-shifting angle of the pulse width modulation wave corresponding to each switch component in the same bridge arm by combining the output voltage sampling signal and the output current sampling signal, according to The magnitude of the output current dynamically adjusts the switching frequency to realize the use of a lower PWM frequency when the load is small. Combined with the above-mentioned phase shift angle and PWM frequency control switch components, the purpose of reducing electromagnetic interference is achieved and the phase shift is improved. Electromagnetic Compatibility of Full Bridge Circuits.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention. Apparently, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a phase-shifted full-bridge circuit disclosed in an embodiment of the present invention;

2 is a schematic flowchart of a control method for a phase-shifted full-bridge circuit disclosed in an embodiment of the present invention;

3 is a schematic flowchart of step S120 in the control method of the phase-shifted full-bridge circuit disclosed in another embodiment of the present invention;

FIG. 4 shows the main waveforms of the main circuit and control signals when the phase-shifted full-bridge circuit is working according to an embodiment of the present invention.

Fig. 5 is a comparative schematic diagram of pulse width modulation waveforms of different transistors of the same bridge arm under different switching frequencies;

6 is a schematic diagram of a specific implementation of frequency conversion by transistors in a phase-shifted full-bridge circuit;

7 is a schematic flowchart of a control method for a phase-shifted full-bridge circuit disclosed in another embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a phase-shifted full-bridge circuit disclosed in another embodiment of the present invention;

9 is a schematic diagram of a control device for a phase-shifted full-bridge circuit disclosed in an embodiment of the present invention;

Fig. 10 is a schematic diagram of the working principle of the control device of the phase-shifted full-bridge circuit disclosed in an embodiment of the present invention;

11 is a schematic structural diagram of a phase-shift angle calculation module in a control device of a phase-shift full-bridge circuit disclosed in an embodiment of the present invention;

Fig. 12 is a schematic structural diagram of a welding power source disclosed by an embodiment of the present invention.

detailed description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments 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, numerous specific details are provided in order to give a thorough understanding of embodiments of the present disclosure. However, one skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or that other methods, materials, devices, etc. may be employed. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed descriptions will be omitted.

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 "comprising", "having" and "having" is used in an open, inclusive sense and means that additional elements/components/etc. may be present in addition to the listed elements/components/etc.

The invention discloses a control method of a phase-shifting full-bridge circuit. The above-mentioned phase-shifting full-bridge circuit is set in the power supply of the welding machine and includes at least one full-bridge converter module. Each of the aforementioned full-bridge converter modules includes at least one bridge arm. Each bridge arm includes a plurality of switch assemblies.

As shown in FIG. 1 , an embodiment of the present invention discloses a phase-shifted full-bridge circuit. The circuit consists of only one full-bridge converter block. The full bridge converter module includes two bridge arms. Each bridge arm includes two switch assemblies. In this embodiment, the switch component is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide Semiconductor Field-Effect Transistor) tube. In other embodiments, the switch component may also be other devices, which is not limited in the present application.

Further, in this embodiment, the above switch component is a silicon carbide (SiC) MOSFET tube. Specifically, due to special process requirements, welding machine power supplies require high current and high power. At present, silicon rectifier and thyristor rectifier power supplies are generally used, which have good reliability and relatively mature technology, but the equipment is bulky, heavy and energy-consuming. Low, low efficiency, and because of the structure, the dynamic and static characteristics are not ideal. However, the current market puts forward new requirements for welding performance, volume and efficiency of welding power sources.

As the third-generation wide-bandgap semiconductor material, SiC has been verified for its superior performance and extremely high efficiency. The extremely low switching loss of SiC power devices is conducive to the high frequency of welding power supplies. Higher frequency means better welding performance and higher power density. Due to the reduction of the output current ripple, the output inductance is also correspondingly reduced, and the dynamic response of the output current is faster, so it can achieve more fine control than ordinary welding machines. The smaller capacitance and inductance also provide convenience for the miniaturization of the welding machine. Therefore, in this embodiment, the MOSFET tube made of silicon carbide is used to facilitate the realization of high frequency and miniaturization of the power supply of the welding machine.

Referring to FIG. 1 , in this embodiment, the PWM (pulse width modulation, pulse width modulation) waves corresponding to the switching 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 . Wherein, 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 turned on complementary. 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 turned on complementary. Moreover, the turn-on time of the first bridge arm is ahead of the second bridge arm.

Continuing to refer to FIG. 1 , the above-mentioned phase-shifted full-bridge circuit further includes a first inductor L _r1 , a transformer T ₁ , a first transformer CT ₁ , a first capacitor C ₁ , a first diode D ₁ , and a second diode D ₂ and the second inductor L ₂ , the third diode Q ₁ , the fourth diode Q ₂ , the fifth diode Q ₃ , the sixth diode Q ₄ and the second transformer CS ₁ . The _first diode D1 and the _second diode D2 are connected in series. _The third diode Q1 and the fifth diode _Q3 are connected in series. The fourth diode _Q2 and the sixth diode _Q4 are connected in series. A first terminal 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 terminal of the _second inductor L2 and the _first transformer CT1. The first transformer CT ₁ is connected to the primary side of the transformer T ₁ . _The primary side of the transformer T1 is also connected between the second transistor S2 and the fourth transistor S4. _The secondary side of the transformer T1 is respectively connected between the third diode Q1 and the fifth diode _Q3 , and between the _fourth diode _Q2 and the sixth diode _Q4 .

The input end of the phase-shifting full-bridge circuit is connected to the output end of the PFC circuit of the welding machine power supply, and the welding workpiece N1 is arranged between the positive pole V _O ⁺ and the negative pole V _O- of the output end of the phase-shifting full-bridge circuit. The connection relationship between the various components in the above-mentioned phase-shifting full-bridge circuit can be referred to as shown in FIG. 1 , which will not be repeated in this embodiment.

As shown in FIG. 2 , an embodiment of the present invention discloses a control method for a phase-shifted full-bridge circuit. Above-mentioned control method comprises the following steps:

S110, sampling the output voltage of the phase-shifted full-bridge circuit and the corresponding output current of each full-bridge converter module, and obtaining the output voltage sampling signal and the corresponding output current sampling signal of each full-bridge converter module.

Specifically, taking FIG. 1 as an example for illustration, the output voltage of the phase-shifted full-bridge circuit is the voltage between the positive pole and the negative pole of the output terminal. Since the phase-shifted full-bridge circuit in FIG. 1 has only one full-bridge converter module, the above output current is the output current of the full-bridge converter module. The sampling of the above output current and output voltage can be realized by differential sampling, and the specific implementation process of sampling can be realized by referring to the existing technology, and will not be repeated in this embodiment.

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, and the corresponding output current of each full-bridge converter module is obtained sample signal.

S120. According to the above-mentioned output voltage sampling signal and the above-mentioned output current sampling signal, calculate and obtain the phase shift angle corresponding to each of the above-mentioned full-bridge converter modules.

During specific implementation, as shown in Figure 3, step S120 includes:

S121. Perform voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result. Wherein, in this step, the difference between the preset voltage reference signal and the above-mentioned output voltage sampling signal is taken as the first calculation result. That is, the above voltage error is calculated as the difference between the preset voltage reference signal and the output voltage sampling signal.

S122. Perform proportional integral calculation on the first calculation result to obtain a second calculation result.

S123. Obtain a current reference signal after filtering the above-mentioned second calculation result by using a filter.

S124. Perform current error calculation according to the output current sampling signal and the current reference signal to obtain a third calculation result. Wherein, in this step, the difference between the above-mentioned current reference signal and the above-mentioned output current sampling signal is used as the third calculation result. That is, the current error is calculated as the difference between the calculated current reference signal and the above-mentioned output current sampling signal.

S125. Perform proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.

The above step S122 is to perform PI (proportional integral, proportional integral) calculation on the difference between the preset voltage reference signal and the output voltage sampling signal. Then, the second calculation result may be filtered by a first-order low-pass filter to obtain a current reference signal. Wherein, 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 angles corresponding to each bridge arm in the same full-bridge converter module are the same. The phase shift angle is the phase difference between the PWM waves corresponding to the respective transistors under the same bridge arm generated subsequently.

Therefore, step S120 is to first calculate the voltage loop PI, and then perform the current loop PI calculation. Wherein, the specific implementation process of PI calculation can be implemented with reference to the prior art, and will not be repeated in this embodiment.

S130, comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switching component according to the comparison result. Wherein, the switching frequency of all switching components in the same full-bridge converter module is the same. The aforementioned preset hysteresis current threshold includes a preset hysteresis current upper limit and a preset hysteresis current lower limit. Wherein, the preset upper limit value of the hysteresis current is greater than the preset lower limit value of the hysteresis current.

In this step, when the output current sampling signal is smaller than the preset hysteresis current lower limit value, the switching frequency corresponding to the switch assembly is reduced to a first preset frequency threshold. When the output current sampling signal is less than the preset hysteresis current lower limit, it means that the welding machine is in a light-load state. When the welding machine is running without load, it is also in a light load state.

Downclocking at light loads can bring many benefits. On the one hand, a longer dead time can be allowed after frequency reduction, thereby increasing the power range of soft-on. On the other hand, after the frequency is reduced, the noise generated by the transistor per unit time will be reduced, which greatly reduces the electromagnetic interference caused by hard switching, and improves the electromagnetic compatibility of the phase-shifted full-bridge circuit.

Exemplarily, the above-mentioned first preset frequency threshold may be 75kHz, and the preset lower limit value of hysteresis current may be 100A, which is not limited in the present application.

Specifically, FIG. 4 shows the main waveforms of the main circuit and control signals when the phase-shifted full-bridge circuit is working. Referring to Fig. 4, i _L represents the oscillating current of the primary side of the transformer, u _h1 represents the primary voltage of the transformer, and u _h2 represents the secondary voltage of the transformer. The shaded part of u _h2 in Fig. 4 indicates that no voltage is output in the corresponding time period. The control signal waveform shown in FIG. 4 is a pulse width modulation waveform corresponding to a PWM wave for controlling each transistor. Among them, U _in represents the input voltage of the phase-shifted full-bridge circuit. K represents the turns ratio of the primary and secondary sides of the transformer. U _in /K represents the ratio between U _in and K.

During the period from t ₀ to t ₁ , transistor S1 is turned off, and the primary side resonant current charges the bulk capacitance of transistor S1, and at the same time discharges the bulk 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 lead to zero-voltage turn-on failure of transistor S3, resulting in turn-on loss. In other words, it takes time to charge and discharge the capacitor, and soft opening can only be performed when the capacitor is charged and discharged within the specified dead time. Therefore, to achieve soft switching, it is necessary to speed up the charging and discharging time of the capacitor, and/or extend the dead time. Wherein, the dead time refers to a time period during which two transistors of the same bridge arm are in an off state at the same time.

It can be seen that the size of the primary current and dead zone has a great influence on whether the phase-shifted full-bridge circuit can complete soft switching. The greater the power, the greater the primary current, and the faster the charge and discharge of the switch body capacitance, the easier it is for the converter to complete soft opening. The longer the dead time is, the longer it allows the capacitor to charge and discharge, and the easier it is to realize soft opening.

Therefore, when the power is small, that is, when the output current is small, it is necessary to increase the dead time to expand the power range of soft-on, and an excessively large dead time will cause the loss of the effective duty cycle, and the low no-load voltage will increase Probability of arc ignition failure. However, if the switching cycle is increased in the same proportion as the dead time, the loss of duty cycle caused by the dead time will remain the same at different switching frequencies, so reducing the switching frequency at light loads can effectively solve this problem .

The main purpose of switching power supply to pursue high frequency is to reduce the parameters of inductance and capacitance, thereby reducing the size of the converter, that is, the phase-shifting full-bridge circuit, increasing the power density, and helping to realize the miniaturization of switching power supply. Under the smaller inductance and capacitance parameters, reducing the switching frequency will increase the current and voltage ripple in the circuit, which will lead to problems such as increased stress on the switch tube and saturation of magnetic components. However, this problem will not occur when the welding machine is under light load. Since the power of the welding machine itself is small, even if the ripple increases, it will not exceed the safe range.

Fig. 5 shows the comparison of the pulse width modulation waveforms of the same bridge arm under different switching frequencies. The pulse width modulation waveforms of the first transistor S1 and the third transistor S3 in the first bridge arm at a frequency of 75 kHz and the pulse width modulation waveforms of a frequency of 150 kHz are respectively shown. The abscissa in FIG. 5 represents time t.

FIG. 6 shows a schematic diagram of implementing the switching of 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 during frequency switching. And take the magnitude of the output current as the switching condition. When the output current i is greater than the hysteresis upper limit I _{up_lim} , which is the preset hysteresis current upper limit, switch from low frequency, which is the first preset frequency threshold, to high frequency, which is the second preset frequency threshold; for example, switch from low frequency 75kHz to high frequency 150kHz. When the output current i is less than the hysteresis lower limit I _{low_lim} , that is, the preset lower limit of the hysteresis current, the high frequency 150kHz is switched to the low frequency 75kHz. I _max represents the maximum value of the output current of the circuit. FIG. 6 also shows the change of the corresponding generated pulse width modulation waveform after the frequency conversion.

S140. Generate 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 respectively control the corresponding switching components to be turned on and off. During specific implementation, this step may include:

Obtain the duty cycle corresponding to each bridge arm. Wherein, the duty ratios corresponding to the switching components in the same bridge arm are the same. Then according to the above-mentioned phase shift angle, switching frequency and above-mentioned duty cycle, a pulse width modulation wave corresponding to each of the above-mentioned switching components is generated.

Wherein, the above-mentioned duty cycle may be generated by preset, for example, it is 50%. The switching frequency is the frequency of the PWM wave. In this case, the step is: generate a pulse width modulated wave according to the phase shift angle, the switching frequency and the preset duty cycle.

In this embodiment, this step calculates and generates two control signals, and each control signal 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 a transistor to turn on or off.

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 switching component is increased to a second preset frequency threshold. Wherein, the above-mentioned second preset frequency threshold is greater than the above-mentioned first preset frequency threshold.

In some embodiments, when the output current sampling signal is between the preset hysteresis current lower limit value and the preset hysteresis current upper limit value, the corresponding switching frequency can remain unchanged, or switch to the above-mentioned second preset value. Set the frequency threshold.

Exemplarily, the second preset frequency threshold may be 150kHz, the preset lower limit of hysteresis current may be 100A, and the preset upper limit of hysteresis current may be 150A, which is not limited in the present application.

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

S131. When the output current sampling signal is smaller than the preset lower limit value of the hysteresis current, reduce the switching frequency corresponding to the switching component, and acquire a reduction ratio of the switching frequency.

S132. According to the reduction ratio of the switching frequency corresponding to the above-mentioned switching component, obtain the increasing ratio of the switching period corresponding to the switching component.

S133. Increase the dead time corresponding to each bridge arm in the same proportion according to the above-mentioned increasing ratio of the switching period.

That is, the dead time corresponding to each bridge arm is increased by the same ratio as the switching period.

An example is given below, for example, when the switching frequency of the transistor is switched from a high frequency of 150kHz to a low frequency of 75kHz, the reduction ratio is 1/2. Then the ratio of the switching cycle increase is the opposite number of 1/2, which is 2. Therefore, the dead time corresponding to each bridge arm in the circuit is also doubled.

Because the excessive dead time will lead to the loss of effective duty ratio, there will be a problem that the no-load voltage is too low, which will increase the probability of arc ignition failure. In this embodiment, the switching cycle and the dead time are increased by the same ratio, so that the loss of duty cycle caused by the dead time can be kept the same at different switching frequencies, thereby solving the above-mentioned problem.

As shown in FIG. 8 , another embodiment of the present invention discloses a phase-shifted full-bridge circuit and a connected PFC (PowerFactor Corrector, power factor correction) circuit. The circuit includes two parallel full-bridge converter modules, that is, the first full-bridge converter module 81 and the second full-bridge converter module 82 are connected in parallel. Wherein, the specific structures of the first full-bridge converter module 81 and the second full-bridge converter module 82 can be referred to as shown in FIG. 8 , which will not be repeated in this embodiment.

When the phase-shifted full-bridge circuit in this figure is controlled by the control method disclosed in the above-mentioned embodiments, it is necessary to sample the output current for the two full-bridge converter modules 81 to generate corresponding output current sampling signals, and then for the two The full bridge converter module 81 calculates the corresponding phase shift angles respectively. Then get the corresponding pulse width modulation wave. During the calculation process, the corresponding reference output voltage sampling signals of the two full-bridge converter modules 81 are the same.

As shown in FIG. 9 , another embodiment of the present invention discloses a control device for a phase-shifted full-bridge circuit. The unit includes:

The signal sampling module 91 samples the output voltage of the above-mentioned phase-shifted full-bridge circuit and the output current corresponding to each of the above-mentioned full-bridge converter modules, and respectively obtains the output voltage sampling signal and the corresponding output current sampling signal of each of the above-mentioned full-bridge converter modules .

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

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.

The pulse width modulation wave generation module 94 generates a pulse width modulation wave corresponding to each of the above switch components according to the above phase shift angle and the above switch frequency, so as to respectively control the corresponding switch components to be turned on and off.

Specifically, taking FIG. 1 as an example for illustration, the output voltage of the phase-shifted full-bridge circuit is the voltage between the positive pole and the negative pole of the output terminal. Since the phase-shifted full-bridge circuit in FIG. 1 has only one full-bridge converter module, the above output current is the output current of the full-bridge converter module. The sampling of the above output current and output voltage can be realized by differential sampling, and the specific implementation process of sampling can be realized by referring to the existing technology, and will not be repeated in this embodiment.

The phase shift angle calculation module first performs voltage loop PI calculation according to the output voltage sampling signal, and then performs current loop PI calculation according to the output current sampling signal. Wherein, the specific implementation process of PI calculation can be implemented with reference to the prior art, and will not be repeated in this embodiment.

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, and the corresponding output current of each full-bridge converter module is obtained sample signal.

Wherein, the switching frequency of all switching components in the same full-bridge converter module is the same. The aforementioned preset hysteresis current threshold includes a preset hysteresis current upper limit and a preset hysteresis current lower limit. Wherein, the preset upper limit value of the hysteresis current is greater than the preset lower limit value of the hysteresis current.

When the output current sampling signal is smaller 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 means that the welding machine is in a light-load state. When the welding machine is running without load, it is also in a light load state.

Downclocking at light loads can bring many benefits. On the one hand, a longer dead time can be allowed after frequency reduction, thereby increasing the power range of soft-on. On the other hand, after the frequency is reduced, the noise generated by the transistor per unit time will be reduced, which greatly reduces the electromagnetic interference caused by hard switching, and improves the electromagnetic compatibility of the phase-shifted full-bridge circuit.

Exemplarily, the above-mentioned first preset frequency threshold may be 75kHz, and the preset lower limit value of hysteresis current may be 100A, which is not limited in the present application.

For a phase-shifted full-bridge circuit with only one full-bridge converter module, the PWM wave generation module calculates and generates two control signals, and each control signal 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 a transistor to turn on or off.

It can be understood that the control device for the phase-shifted full-bridge circuit of the present invention also includes other existing functional modules that support the operation of the control device for the phase-shifted full-bridge circuit. The control device of the phase-shifted full-bridge circuit shown in FIG. 9 is only an example, and should not impose any limitation on the functions and application scope of the embodiments of the present invention.

The control device of the phase-shifted full-bridge circuit in this embodiment is used to realize the method for controlling the above-mentioned phase-shifted full-bridge circuit, so the specific implementation steps of the control device of the phase-shifted full-bridge circuit can refer to the above-mentioned phase-shifted full-bridge The description of the circuit control method will not be repeated here.

In some embodiments, on the basis of the above-mentioned embodiment corresponding to FIG. 9 , the above-mentioned switching frequency adjustment module includes:

The first ratio acquiring 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 smaller than the preset lower limit value of the hysteresis current.

The second ratio acquiring unit is configured to acquire, according to the ratio of decreasing switching frequency corresponding to the switching component, the ratio of increasing the switching period corresponding to the switching component.

The dead-time increasing unit increases the dead-time corresponding to each of the above-mentioned bridge arms in the same proportion according to the ratio of the above-mentioned increase in the switching period.

An example is given below, for example, when the switching frequency of the transistor is switched from a high frequency of 150kHz to a low frequency of 75kHz, the reduction ratio is 1/2. Then the ratio of the switching cycle increase is the opposite number of 1/2, which is 2. Therefore, the dead time corresponding to each bridge arm in the circuit is also doubled.

Because the excessive dead time will lead to the loss of effective duty ratio, there will be a problem that the no-load voltage is too low, which will increase the probability of arc ignition failure. In this embodiment, the switching cycle is increased in the same proportion as the dead time, so that the loss of duty cycle caused by the dead time can be kept the same at different switching frequencies, thereby solving the above-mentioned problem.

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 above-mentioned second preset frequency threshold is greater than the above-mentioned first preset frequency threshold.

In some embodiments, when the output current sampling signal is between the preset hysteresis current lower limit value and the preset hysteresis current upper limit value, the corresponding switching frequency can remain unchanged, or switch to the above-mentioned second preset value. Set the frequency threshold.

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

FIG. 10 shows the working principle of the control device of the phase-shifted full-bridge circuit. As shown in Figure 10, calculate the difference between the preset voltage reference signal V _ref and the output voltage sampling signal V _o , and then perform PI on the difference between the preset voltage reference signal V _ref and the output voltage sampling signal V _o (proportional integral, proportional integral) calculation. Then the second calculation result can be filtered by a first-order low-pass filter to obtain the current reference signal I _ref . The difference between the current reference signal I _ref and the above-mentioned output current sampling signal I _o is calculated. Perform PI proportional integral calculation on the difference between the current reference signal I _ref and the above-mentioned output current sampling signal I _o to obtain the phase shift angle corresponding to each of the above-mentioned full-bridge converter modules, and transmit it to the pulse width modulation wave generation module. The pulse width modulation wave generation module generates a pulse width modulation wave corresponding to each of the above switch components according to the phase shift angle and the switch frequency, so as to respectively control the corresponding switch components to be turned on and off.

Referring to FIG. 10 , the pulse width modulation wave generation module generates PWM waves, corresponding to control transistors S1 to S4 respectively.

Fig. 11 shows the structure of a phase-shift angle calculation module in the control device of a phase-shift full-bridge circuit.

In this embodiment, the above-mentioned phase shift angle calculation module 92 includes:

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.

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

The current reference signal acquisition unit 923 obtains the current reference signal after filtering the above-mentioned second calculation result by using a filter.

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.

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

As shown in Fig. 12, an embodiment of the present invention discloses a welding machine power supply. The power supply of the welding machine includes the control device 33 of the phase-shifting full-bridge circuit disclosed in any one of the above-mentioned embodiments. For the detailed structural features and advantages of the control device of the phase-shifted full-bridge circuit, reference may be made to the description of the above-mentioned embodiments, which will not be repeated here.

Referring to FIG. 12 , the welding power supply also includes an EM suppression module 31 , a PFC circuit 25 , a PFC control device 26 , a phase-shifting 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 rectification module is connected to the load of the welding machine. The connection relationship between EMI suppression module, PFC circuit, PFC control device, phase-shifted full-bridge inverter circuit, phase-shifted full-bridge circuit control device, high-frequency transformer, rectifier module, auxiliary power supply and fan can refer to Figure 12. The embodiment will not be described in detail.

To sum up, the control method, device and welding machine power supply of the present invention have at least the following advantages:

The control method and device of the phase-shifting full-bridge circuit disclosed in the embodiment of the present invention, and the power supply of the welding machine generate the phase-shifting angle of the pulse width modulation wave corresponding to each switch component in the same bridge arm by combining the output voltage sampling signal and the output current sampling signal , dynamically adjust the switching frequency according to the output current, realize the use of lower PWM frequency when the load is small, and combine the above-mentioned phase shift angle and PWM frequency control switch components, so as to achieve the purpose of reducing electromagnetic interference and improve the Electromagnetic compatibility of phase-shifted full-bridge circuits.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (14)

1. A control method for a phase-shifting full-bridge circuit, characterized in that, the phase-shifting full-bridge circuit is arranged in a welding machine power supply, and includes at least one full-bridge converter module, each of which includes a full-bridge converter module At least one bridge arm, each bridge arm includes a plurality of switch assemblies; 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 output voltage sampling signals and output current sampling signals corresponding to each of the full-bridge converter modules, respectively ; S120. According to the output voltage sampling signal and the output current sampling signal, calculate and obtain a phase shift angle corresponding to each of the full-bridge converter modules; S130, comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switching component according to the comparison result; S140. Generate a pulse width modulation wave corresponding to each of the switch components according to the phase shift angle and the switch frequency, so as to respectively control the corresponding switch components to be turned on and off. 2. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein the preset hysteresis current threshold includes a preset hysteresis current lower limit; step S130 includes: When the output current sampling signal is smaller than the preset hysteresis current lower limit value, the switching frequency corresponding to the switching component is reduced to a first preset frequency threshold. 3. the control method of phase shifting full bridge circuit as claimed in claim 2, is characterized in that, step S130 also comprises: When the output current sampling signal is smaller than the preset hysteresis current lower limit value, obtain a reduction ratio of the switching frequency corresponding to the switching component; Acquiring the increasing ratio of the switching cycle corresponding to the switching component according to the decreasing ratio of the switching frequency corresponding to the switching component; According to the increase ratio of the switching period, the dead time corresponding to each of the bridge arms is increased in the same proportion. 4. The control method of the phase-shifted full-bridge circuit as claimed in claim 2, wherein the preset hysteresis current threshold also includes a preset hysteresis current upper limit; wherein, the preset hysteresis current The upper limit value is greater than the preset lower limit value of the hysteresis current; step S130 also 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. 5. the control method of phase shifting full bridge circuit as claimed in claim 1, is characterized in that, step S120 comprises: performing voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result; performing a proportional integral calculation on the first calculation result to obtain a second calculation result; Obtaining a current reference signal after filtering the second calculation result by using a filter; performing current error calculation according to 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. 6. the control method of phase-shifting full-bridge circuit as claimed in claim 5 is characterized in that, step S120 comprises: using 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. 7. the control method of phase shifting full bridge circuit as claimed in claim 1, is characterized in that, step S140 comprises: Obtain the duty ratio corresponding to each bridge arm; wherein, the duty ratios corresponding to the switching components in the same bridge arm are the same; According to the phase shift angle, the switching frequency and the duty ratio, a pulse width modulation wave corresponding to each of the switching components is generated. 8 . The control method of the phase-shifted full-bridge circuit according to claim 1 , wherein each bridge arm includes two switching components, and the PWM waves corresponding to the switching components in each bridge arm are complementary. 9. The control method of the phase-shifted full-bridge circuit according to claim 1, wherein the switch components are silicon carbide field effect transistors. 10. A control device for a phase-shifted full-bridge circuit, for realizing the control method as claimed in claim 1, characterized in that, comprising: The signal sampling module 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 the output voltage sampling signal and the output current corresponding to each of the full-bridge converter modules sampling signal; The phase-shift angle calculation module calculates the phase-shift angle corresponding to each full-bridge converter module according to the output voltage sampling signal and the output current sampling signal; The switching frequency adjustment module 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 switching components according to the phase shift angle and the switching frequency, so as to respectively control the corresponding switching components to be turned on and off. 11. The control device according to claim 10, wherein the preset hysteresis current threshold includes a preset hysteresis current lower limit; the switching frequency adjustment module is used for: When the output current sampling signal is smaller than the preset hysteresis current lower limit value, the switching frequency corresponding to the switching component is reduced to a first preset frequency threshold. 12. The control device according to claim 11, wherein the switching frequency adjustment module is further used for: When the output current sampling signal is smaller than the preset hysteresis current lower limit value, obtain a reduction ratio of the switching frequency corresponding to the switching component; Acquiring the increasing ratio of the switching cycle corresponding to the switching component according to the decreasing ratio of the switching frequency corresponding to the switching component; According to the increase ratio of the switching period, the dead time corresponding to each of the bridge arms is increased in the same proportion. 13. The control device according to claim 10, wherein the phase shift angle calculation module comprises: The voltage error calculation unit performs voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result; The first proportional-integral calculation unit performs proportional-integral calculation on the first calculation result to obtain a second calculation result; The current reference signal acquisition unit obtains the current reference signal after filtering the second calculation result by using a filter; The current error calculation unit performs 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 full-bridge converter module. 14. A welding machine power supply, characterized in that it comprises a control device for a phase-shifted full-bridge circuit according to any one of claims 10-13.

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