CN115430885A - Control method and device of phase-shifted full-bridge circuit and welding machine power supply - Google Patents
Control method and device of phase-shifted full-bridge circuit and welding machine power supply Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
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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
Technical Field
The invention relates to the technical field of welding machine power supplies, in particular to a control method and device of a phase-shifted full-bridge circuit and a welding machine power supply.
Background
At present, the trend of welder power supply is towards high frequency and miniaturization, wherein the welder power supply applying soft switching topology can realize high frequency and high efficiency more easily by virtue of lower switching loss. However, the EMI (Electromagnetic Interference) problem caused by the high frequency can seriously affect the control and sampling of the digital chip in the phase-shifted full-bridge circuit of the welder power supply, and moreover, the EMI problem can also cause that the welder is difficult to realize soft switching under light load, and the Interference caused by the voltage spike of the switching device caused by hard switching under high frequency can be more serious. Therefore, how to solve the problem of electromagnetic interference caused by the control of the phase-shifted full-bridge circuit after the power supply of the welding machine is subjected to high frequency is a problem faced at present.
Disclosure of Invention
In view of this, the invention provides a control method and a control device for a phase-shifted full-bridge circuit, and a welding machine power supply, which dynamically adjust a switching frequency according to the magnitude of an output current, so as to control a switching component by using a lower pulse width modulation frequency when a load is smaller, thereby reducing electromagnetic interference.
According to one aspect of the invention, a control method of a phase-shifted full-bridge circuit is provided, wherein the phase-shifted full-bridge circuit is arranged in a welding machine power supply and comprises at least one full-bridge converter module, each full-bridge converter module comprises at least one bridge arm, and each bridge arm comprises a plurality of switch assemblies; the control method comprises the following steps:
s110, 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;
s120, calculating a phase shift angle corresponding to each full-bridge converter module 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, and adjusting the switching frequency corresponding to the switching component according to the comparison result;
and S140, 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 off.
Optionally, the preset hysteresis current threshold includes a preset hysteresis current lower limit value; the step S130 includes:
and when the output current sampling signal is smaller than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component to a first preset frequency threshold value.
Optionally, step S130 further includes:
when the output current sampling signal is smaller than the preset hysteresis current lower limit value, acquiring the reduction proportion of the switching frequency corresponding to the switching component;
acquiring the proportion of the increase of the switching period corresponding to the switching component according to the proportion of the decrease of the switching frequency corresponding to the switching component;
and according to the increasing proportion of the switching period, increasing the dead time corresponding to each bridge arm in the same proportion.
Optionally, the preset hysteresis current threshold further includes a preset hysteresis current upper limit value; the upper limit value of the preset hysteresis current is greater than the lower limit value of the preset hysteresis current; step S130 further includes:
when the output current sampling signal is larger than the preset hysteresis current upper limit value, increasing the switching frequency corresponding to the switching assembly to a second preset frequency threshold value; wherein the second preset frequency threshold is greater than the first preset frequency threshold.
Optionally, step S120 includes:
according to the output voltage sampling signal and a preset voltage reference signal, voltage error calculation is carried out to obtain a first calculation result;
carrying out proportional integral calculation on the first calculation result to obtain a second calculation result;
filtering the second calculation result by using a filter to obtain a current reference signal;
according to the output current sampling signal and the current reference signal, current error calculation is carried out to obtain a third calculation result;
and performing proportional integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.
Optionally, step S120 includes:
taking a difference value between a preset voltage reference signal and the output voltage sampling signal as a first calculation result;
and taking the difference value between the current reference signal and the output current sampling signal as a third calculation result.
Optionally, step S140 includes:
acquiring a duty ratio corresponding to each bridge arm; the duty ratios corresponding to the switch assemblies in the same bridge arm are the same;
and generating a pulse width modulation wave corresponding to each switching component according to the phase shift angle, the switching frequency and the duty ratio.
Optionally, each bridge arm comprises two switch assemblies, and the corresponding PWM waves of the switch assemblies in each bridge arm are complementary.
Optionally, the switch components are all silicon carbide field effect transistors.
According to another aspect of the present invention, there is provided a control device for a phase-shifted full-bridge circuit, for implementing any one of the above control methods, including:
the signal sampling module is used for 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;
the phase shift angle calculation module is used for calculating a 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 adjusting module is used for comparing the output current sampling signal with a preset hysteresis current threshold value and adjusting the switching frequency corresponding to the switching component according to a comparison result;
and the pulse width modulation wave generating module generates 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.
Optionally, the preset hysteresis current threshold includes a preset hysteresis current lower limit value; the switching frequency adjustment module is configured to:
and when the output current sampling signal is smaller than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component to a first preset frequency threshold value.
Optionally, the switching frequency adjustment module is further configured to:
when the output current sampling signal is smaller than the preset hysteresis current lower limit value, acquiring the reduction proportion of the switching frequency corresponding to the switching component;
acquiring the proportion of the increase of the switching period corresponding to the switching component according to the proportion of the decrease of the switching frequency corresponding to the switching component;
and according to the increasing proportion of the switching period, increasing the dead time corresponding to each bridge arm in the same proportion.
Optionally, the phase shift angle calculation module includes:
the voltage error calculation unit is used for performing voltage error calculation according to the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result;
the first proportional integral calculating unit is used for carrying out proportional integral calculation on the first calculation result to obtain a second calculation result;
the current reference signal acquisition unit is used for filtering the second calculation result by using a filter to obtain a current reference signal;
the current error calculation unit is used for calculating a current error according to the output current sampling signal and the current reference signal to obtain a third calculation result;
and the second proportional-integral calculation unit is used for performing 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 invention, there is provided a welder power supply comprising control means for any of the phase-shifted full-bridge circuits described above.
Compared with the prior art, the invention has the beneficial effects that:
the phase-shifted full-bridge circuit control method, the phase-shifted full-bridge circuit control device and the welding machine power supply generate the phase shift 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 that the switch components are controlled by adopting lower pulse width modulation frequency when the load is smaller and combining the phase shift angle and the pulse width modulation frequency, thereby achieving the purpose of reducing electromagnetic interference and improving the electromagnetic compatibility of the phase-shifted full-bridge circuit.
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. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic structural diagram of a phase-shifted full bridge circuit according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a control method of a phase-shifted full bridge circuit according to an embodiment of the present invention;
fig. 3 is a schematic flowchart of step S120 in the control method of the phase-shifted full-bridge circuit according to another embodiment of the disclosure;
fig. 4 shows main waveforms of a main circuit and control signals when the phase-shifted full-bridge circuit disclosed in an embodiment of the present invention operates.
FIG. 5 is a schematic diagram showing the comparison of pulse width modulation waveforms of different transistors of the same bridge arm at different switching frequencies;
FIG. 6 is a schematic diagram of a specific implementation manner of frequency conversion of transistors in the phase-shifted full-bridge circuit;
FIG. 7 is a schematic flow chart of a control method of a phase-shifted full bridge circuit according to another embodiment of the present invention;
FIG. 8 is a schematic diagram of a phase-shifted full bridge circuit according to another embodiment of the present invention;
FIG. 9 is a schematic diagram of a control apparatus of a phase-shifted full bridge circuit according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of the operating principle of the control device of the phase-shifted full-bridge circuit according to an embodiment of the present invention;
fig. 11 is a schematic structural diagram of a phase shift angle calculation module in a control device of a phase-shifted full-bridge circuit according to an embodiment of the present invention;
FIG. 12 is a schematic structural diagram of a power supply of a welder according to 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 different 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 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 to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, materials, devices, etc. 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 description 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/parts/etc.; the terms "comprising," "having," and "providing" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.
The invention discloses a control method of a phase-shifted full-bridge circuit. The phase-shifted full-bridge circuit is arranged in a welding machine power supply and comprises at least one full-bridge converter module. Each full-bridge converter module comprises at least one bridge arm. Each leg 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 comprises only one full-bridge inverter module. The full-bridge converter module comprises two bridge arms. Each leg includes two switch assemblies. In this embodiment, the switch device is a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) Transistor. In other embodiments, the switch assembly may be other devices, and the application is not limited thereto.
Further, in this embodiment, the switching element is a silicon carbide (SiC) MOSFET tube. Specifically, because of special process requirements, a welder power supply needs large current and high power, silicon rectification and thyristor rectification power supplies are generally adopted at present, the reliability is good, the technology is mature, but the equipment is large in size, heavy, low in energy consumption and low in efficiency, and due to the structure, the dynamic and static characteristics are not ideal enough. And the current market puts new requirements on the welding performance, volume and efficiency of the welding power supply.
The superior performance and the extremely high efficiency of SiC as a third-generation wide bandgap semiconductor material have been examined. The extremely low switching loss of the SiC power device is beneficial to realizing high frequency of the power supply of the welding machine. Higher frequencies mean better welding performance and higher power density. Because the output current ripple is reduced, the inductance of the output inductor is correspondingly reduced, and the dynamic response of the output current is faster, the control can be more fine compared with the common welding machine. And the smaller capacitance and inductance also provide convenience for miniaturization of the welding machine. Therefore, in the embodiment, the MOSFET tube made of silicon carbide is beneficial to realizing high frequency and miniaturization of the power supply of the welding machine.
Referring to fig. 1, in the present embodiment, the PWM (pulse width modulation) waves corresponding to the switch components in each bridge arm are complementary. The full-bridge inverter 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 complementarily turned on. The second transistor S2 and the fourth transistor S4 are connected in series to form a second leg. The second transistor S2 and the fourth transistor S4 are complementarily turned on. And the switching-on time of the first bridge arm is ahead of that of the second bridge arm.
With continued reference to FIG. 1, the phase-shifted full bridge circuit further includes a first inductor L r1 Transformer T 1 A first mutual inductor CT 1 A first capacitor C 1 A first diode D 1 A second diode D 2 And a second inductance L 2 A third diode Q 1 A fourth diode Q 2 A fifth diode Q 3 And a sixth diode Q 4 And a second mutual inductor CS 1 . First diode D 1 And a second diode D 2 Are connected in series. Third diode Q 1 And a fifth diode Q 3 Are connected in series. Fourth diode Q 2 And a sixth diode Q 4 Are connected in series. Second inductance L 2 Is connected between the first transistor S1 and the third transistor S3. A first capacitor C 1 Is connected to the second inductor L 2 And the first mutual inductor CT 1 In the meantime. First mutual inductor CT 1 Is connected to a transformer T 1 The primary side of (a). Transformer T 1 Is also connected between the second transistor S2 and the fourth transistor S4. Transformer T 1 Are respectively connected to the third diode Q 1 And a fifth diode Q 3 And a fourth diode Q 2 And a sixth diode Q 4 In between.
The input end of the phase-shifted full-bridge circuit is connected with the output end of a PFC circuit of a welding machine power supply, and the positive pole V of the output end of the phase-shifted full-bridge circuit O + And a negative electrode V O A welding workpiece N1 is provided therebetween. The connection relationship between the components in the phase-shifted full bridge circuit can be referred to as shown in fig. 1, and the description of this embodiment is omitted.
As shown in fig. 2, an embodiment of the present invention discloses a control method of a phase-shifted full bridge circuit. The control method comprises the following steps:
and S110, sampling the output voltage of the phase-shifted full-bridge circuit and the output current corresponding to each full-bridge converter module, and respectively obtaining an output voltage sampling signal and an output current sampling signal corresponding to each full-bridge converter module.
Specifically, taking fig. 1 as an example, 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 inverter module, the output current is the output current of the full-bridge inverter module. The sampling of the output current and the output voltage may be implemented by differential sampling, and the specific implementation process of the sampling may be implemented by referring to the prior art, which is not described in detail in this embodiment.
When the phase-shifted full-bridge circuit is provided with two or more full-bridge converter modules, the output current of each full-bridge converter module is respectively sampled, and the output current sampling signal associated with each full-bridge converter module is correspondingly obtained.
And S120, calculating a phase shift angle corresponding to each full-bridge converter module according to the output voltage sampling signal and the output current sampling signal.
In specific implementation, as shown in fig. 3, step S120 includes:
and S121, performing voltage error calculation according to the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result. In the step, a difference value between a preset voltage reference signal and the output voltage sampling signal is used as a first calculation result. That is, the voltage error is calculated as a difference between the preset voltage reference signal and the output voltage sampling signal.
And S122, performing proportional integral calculation on the first calculation result to obtain a second calculation result.
And S123, filtering the second calculation result by using a filter to obtain a current reference signal.
And S124, performing current error calculation according to the output current sampling signal and the current reference signal to obtain a third calculation result. Wherein the step uses a difference between the current reference signal and the output current sampling signal as a third calculation result. I.e. the current error is calculated as the difference between the calculated current reference signal and the output current sample signal.
And S125, performing proportional integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.
In the step S122, a PI (proportional integral) calculation is performed on the difference between the preset voltage reference signal and the output voltage sampling signal. The second calculation may then be filtered using a first order low pass filter to obtain a current reference signal. Because the output currents of the same full-bridge converter module are the same, the phase shift angles calculated by the same full-bridge converter module are also the same. The phase shift angles corresponding to all bridge arms in the same full-bridge converter module are 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.
Therefore, step S120 is to perform the voltage loop PI calculation first, and then perform the current loop PI calculation. The specific implementation process of the PI calculation may be implemented by referring to the prior art, and is not described in detail in this embodiment.
And S130, comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switching element according to the comparison result. And the switching frequencies of all the switching components in the same full-bridge converter module are the same. The preset hysteresis current threshold includes a preset hysteresis current upper limit value and a preset hysteresis current lower limit value. Wherein, the preset hysteresis current upper limit value is larger than the preset hysteresis current lower limit value.
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 switching element is reduced to a first preset frequency threshold value. And when the output current sampling signal is smaller than the preset hysteresis current lower limit value, the welding machine is in a light load state. When the welder runs in no-load state, the welder is also in a light load state.
Downconversion under light load can provide many benefits. On the one hand, the down conversion can allow longer dead time, thereby increasing the soft-on power range. On the other hand, the noise generated in unit time by the transistor after frequency reduction is reduced, so that the electromagnetic interference caused by hard switching is greatly reduced, and the electromagnetic compatibility of the phase-shifted full-bridge circuit is improved.
For example, the first preset frequency threshold may be 75kHz, and the preset hysteresis current lower limit value may be 100A, which is not limited in this application.
In particular, fig. 4 shows the main waveforms of the main circuit and the control signals when the phase-shifted full-bridge circuit is in operation. Referring to FIG. 4, i L Representing the oscillating current, u, of the primary side of the transformer h1 Representing the primary voltage, u, of the transformer h2 Representing the secondary voltage of the transformer. U in FIG. 4 h2 The shaded portion of (a) indicates that no voltage is output for the corresponding period of time. The control signal waveform shown in fig. 4 is a pulse width modulation waveform corresponding to a PWM wave for controlling each transistor. Wherein, U in Representing the input voltage of a phase-shifted full-bridge circuit. K represents the turn ratio of the primary side and the secondary side of the transformer. U shape in K represents U in And K.
At t 0 To t 1 In the time period, the transistor S1 is turned off, the primary side resonant current charges the bulk capacitor of the transistor S1, and simultaneously discharges the bulk capacitor of the transistor S3 until the voltage between the drain and the source of the transistor S3 is reduced to zero. This process must be completed within the dead time otherwise it will cause the transistor S3 to fail to turn on at zero voltage, resulting in turn-on losses. That is, the capacitor takes time to charge and discharge, and can be turned on only when the capacitor is charged and discharged within a predetermined dead time. Therefore, to achieve soft switching, it is desirable to increase the capacitor charge and discharge time and/or to extend the dead time. The dead time refers to a time period during which two transistors of the same bridge arm are simultaneously in an off state.
Therefore, the primary current and the size of the dead zone have great influence on whether the phase-shifted full bridge circuit can complete soft switching. The larger the power is, the larger the primary current is, the faster the charging and discharging of the capacitor of the switching tube body are, and the easier the converter is to finish soft switching. While the larger the dead time, the longer it takes to charge and discharge the capacitor, the easier it is to achieve soft-on.
Therefore, when the power is small, that is, the output current is small, the dead time needs to be increased to enlarge the soft-on power range, an excessive dead time may cause the loss of the effective duty ratio, and a too low idle voltage may increase the probability of arc striking failure. If the switching period and the dead time are increased in the same proportion, the duty ratio loss caused by the dead time can be kept the same under different switching frequencies, and therefore the problem can be effectively solved by reducing the switching frequency under light load.
The high frequency of the switching power supply is mainly aimed at reducing inductance and capacitance parameters, so that the size of a converter, namely a phase-shifted full-bridge circuit, is reduced, the power density is improved, and the miniaturization of the switching power supply is favorably realized. Under the condition of smaller inductance and capacitance parameters, the ripple of current and voltage in the circuit can be increased by reducing the switching frequency, so that the problems of stress increase of a switching tube, saturation of a magnetic element and the like are caused. The problem can not be caused when the frequency is reduced when the welding machine is in a light-load state, and the power of the welding machine power supply is small, so that the ripple wave cannot exceed the safety range even if the ripple wave is increased.
Fig. 5 shows a comparison of the same leg pulse width modulation waveforms at different switching frequencies. The pulse width modulated waveforms at 75kHz and 150kHz for the first transistor S1 and the third transistor S3 in the first leg are shown, respectively. The abscissa of fig. 5 represents time t.
Fig. 6 shows a switching implementation of the switching frequency of the transistor. In order to ensure that the phase-shifted full-bridge circuit can stably operate, in this embodiment, hysteresis control is adopted during frequency switching. And the magnitude of the output current is used as a switching condition. When the output current I is larger than the hysteresis upper limit I up_lim Namely, when the upper limit value of the hysteresis current is preset, switching from a low frequency, namely a first preset frequency threshold value, to a high frequency, namely a second preset frequency threshold value; for example, low frequency 75kHz is switched to high frequency 150kHz. When the output current I is less than the lower limit I of the hysteresis loop low_lim Namely, when the lower limit value of the hysteresis current is preset, the high frequency is switched from 150kHz to 75kHz. I.C. A max Representing the maximum value of the circuit output current. Fig. 6 also shows the variation of the corresponding generated pulse width modulation waveform after frequency conversion.
And S140, generating a PWM wave corresponding to each switching element according to the phase shift angle and the switching frequency, so as to control the corresponding switching elements to be turned on and off respectively. In specific implementation, the steps may include:
and acquiring the duty ratio corresponding to each bridge arm. And the duty ratios corresponding to the switch assemblies in the same bridge arm are the same. And then generating a pulse width modulation wave corresponding to each switching component according to the phase shift angle, the switching frequency and the duty ratio.
The duty ratio may be generated for a preset value, for example, 50%. The switching frequency is the frequency of the PWM wave. At this time, the steps are as follows: and generating a pulse width modulation wave according to the phase shift angle, the switching frequency and a preset duty ratio.
In this embodiment, the step calculates and generates two control signals, where each control signal includes two complementary PWM waves. Each path of control signal is used for controlling two transistors in the same bridge arm. Each pulse width modulated wave is used to control one transistor to be turned on or off.
In another embodiment, in step S130, when the output current sampling signal is greater than the preset hysteresis current upper limit value, the switching frequency corresponding to the switching element is increased to a second preset frequency threshold. Wherein the second predetermined frequency threshold is greater than the first predetermined 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 may be kept unchanged, or also switched to the second preset frequency threshold.
For example, the second preset frequency threshold may be 150kHz, the preset hysteresis current lower limit value may be 100A, and the preset hysteresis current upper limit value may be 150A, which is not limited in this application.
In another embodiment of the present application, another control method for a phase-shifted full bridge circuit is disclosed. As shown in fig. 7, in the method, on the basis of the corresponding embodiment of fig. 2, step S130 further includes:
and S131, when the output current sampling signal is smaller than the preset lower limit value of the hysteresis current, reducing the switching frequency corresponding to the switching component, and acquiring the reduction ratio of the switching frequency.
And S132, acquiring the proportion of the increase of the switching period corresponding to the switching assembly according to the proportion of the decrease of the switching frequency corresponding to the switching assembly.
And S133, increasing the dead time corresponding to each bridge arm in the same proportion according to the proportion of the increase of the switching period.
That is, the dead time corresponding to each arm is increased at the same rate as the rate at which the switching period is increased.
For example, when the switching frequency of the transistor is switched from 150kHz at a high frequency to 75kHz at a low frequency, the ratio of the decrease is 1/2. The proportion of the increase in the switching period is the opposite of 1/2, i.e. 2. Therefore, the dead time corresponding to each arm in the circuit is also increased to 2 times.
Since excessive dead time can result in loss of effective duty cycle, the problem can arise that the no-load voltage is too low, thereby increasing the probability of arc initiation failure. In the embodiment, the switching period and the dead time are increased in the same proportion, and the duty ratio loss caused by the dead time can be kept the same under different switching frequencies, so that the problem is solved.
As shown in fig. 8, 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 inverter modules, namely a first full-bridge inverter module 81 and a second full-bridge inverter module 82 connected in parallel. The specific structures of the first full-bridge inverter module 81 and the second full-bridge inverter module 82 can be referred to as shown in fig. 8, and are not described again in this embodiment.
When the phase-shifted full-bridge circuit in the figure is controlled by applying the control method disclosed in the above embodiment, it is necessary to sample output currents respectively for the two full-bridge converter modules 81, generate output current sampling signals corresponding to the output currents respectively, and then calculate corresponding phase shift angles respectively for the two full-bridge converter modules 81. Then, the corresponding pulse width modulation waves are obtained. In the calculation process, the output voltage sampling signals corresponding to the references of the two full-bridge inverter 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 device comprises:
and a signal sampling module 91 for 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.
The phase shift angle calculation module 92 calculates a phase shift angle corresponding to each of the full-bridge inverter modules according to the output voltage sampling signal and the output current sampling signal.
And a switching frequency adjustment module 93 for comparing the output current sampling signal with a preset hysteresis current threshold, and adjusting the switching frequency corresponding to the switching element according to the comparison result.
The pwm wave generating module 94 generates a pwm wave corresponding to each of the switching elements according to the phase shift angle and the switching frequency, so as to control the corresponding switching elements to be turned on and off respectively.
Specifically, taking fig. 1 as an example, 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 inverter module, the output current is the output current of the full-bridge inverter module. The sampling of the output current and the output voltage may be implemented by differential sampling, and the specific implementation process of the sampling may be implemented by referring to the prior art, which is not described in detail in this embodiment.
The phase shift angle calculation module 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. The specific implementation process of PI calculation may be implemented by referring to the prior art, and is not described in detail in this embodiment.
When the phase-shifted full-bridge circuit is provided with two or more full-bridge converter modules, the output current of each full-bridge converter module is respectively sampled, and the output current sampling signal associated with each full-bridge converter module is correspondingly obtained.
And the switching frequencies of all the switching components in the same full-bridge converter module are the same. The preset hysteresis current threshold includes a preset hysteresis current upper limit value and a preset hysteresis current lower limit value. The preset hysteresis current upper limit value is larger than the preset hysteresis current lower limit value.
When the output current sampling signal is smaller than the preset hysteresis current lower limit value, the switching frequency adjusting module reduces the switching frequency corresponding to the switching component to a first preset frequency threshold value. When the output current sampling signal is smaller than the preset hysteresis current lower limit value, the welding machine is in a light-load state. When the welder runs in no-load state, the welder is also in a light load state.
Downconversion under light loads can provide many benefits. On the one hand, the down conversion can allow longer dead time, thereby increasing the soft-on power range. On the other hand, the noise generated in the unit time of the transistor after the frequency reduction is reduced, so that the electromagnetic interference caused by hard switching is greatly reduced, and the electromagnetic compatibility of the phase-shifted full-bridge circuit is improved.
For example, the first preset frequency threshold may be 75kHz, and the preset hysteresis current lower limit value may be 100A, which is not limited in this application.
Aiming at the phase-shifted full-bridge circuit with only one full-bridge converter module, the pulse width modulation wave generating module calculates and generates two paths of control signals, and each path of control signal comprises two complementary PWM waves. Each path of control signal is used for controlling two transistors in the same bridge arm. Each pulse width modulated wave is used to control one transistor to be turned on or off.
It will be appreciated that the control arrangement of the phase-shifted full-bridge circuit of the present invention may also comprise other existing functional blocks that support the operation of the control arrangement of 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 bring any limitation to the function and the application range of the embodiment of the present invention.
The control device of the phase-shifted full-bridge circuit in this embodiment is used for implementing the method for controlling the phase-shifted full-bridge circuit, and therefore, for the specific implementation steps of the control device of the phase-shifted full-bridge circuit, reference may be made to the description of the method for controlling the phase-shifted full-bridge circuit, and details are not repeated here.
In some embodiments, based on the corresponding embodiment of fig. 9, the switching frequency adjustment module includes:
and a first proportion obtaining unit, configured to obtain a proportion of reduction of the switching frequency corresponding to the switching element, when the output current sampling signal is smaller than the preset hysteresis current lower limit value.
And a second ratio acquisition unit that acquires a ratio at which the switching cycle corresponding to the switching element increases, based on a ratio at which the switching frequency corresponding to the switching element decreases.
And a dead time increasing unit which increases the dead time corresponding to each bridge arm in the same proportion according to the proportion of the increased switching period.
For example, when the switching frequency of the transistor is switched from 150kHz at a high frequency to 75kHz at a low frequency, the ratio of the decrease is 1/2. The ratio of the increase in the switching period is the opposite of 1/2, i.e. 2. Therefore, the dead time corresponding to each arm in the circuit is also increased by a factor of 2.
Since excessive dead time can result in loss of effective duty cycle, the problem can arise that the idle voltage is too low, thereby increasing the probability of arc initiation failure. In the embodiment, the switching period and the dead time are increased in the same proportion, and the duty ratio loss caused by the dead time can be kept the same under different switching frequencies, so that the problem is solved.
In another embodiment, when the output current sampling signal is greater than the predetermined hysteresis current upper limit value, the switching frequency corresponding to the switching element is increased to a second predetermined frequency threshold. Wherein the second predetermined frequency threshold is greater than the first predetermined 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 may be kept unchanged, or also switched to the second preset frequency threshold.
For example, the second preset frequency threshold may be 150kHz, and the preset hysteresis current upper limit value may be 150A, which is not limited in this application.
Fig. 10 shows the operating principle of the control device of the phase-shifted full-bridge circuit described above. As shown in FIG. 10, a predetermined voltage reference signal V is calculated ref And outputting a voltage sampling signal V o Difference between them, then for a preset voltage reference signal V ref And output voltage sampling signal V o The difference between them is calculated by PI (proportional integral). Then, the second calculation result can be filtered by a first-order low-pass filter to obtain a current reference signal I ref . Calculating a current reference signal I ref And the output current sampling signal I o The difference between them. For current reference signal I ref And the output current sampling signal I o And PI proportional integral calculation is carried out on the difference value between the full-bridge converter modules to obtain a phase shift angle corresponding to each full-bridge converter module, and the phase shift angles are transmitted to a pulse width modulation wave generation module. The PWM wave generating module generates a PWM wave corresponding to each switching component according to the phase shift angle and the switching frequency so as to control the corresponding switching components to be switched on and off respectively.
Referring to fig. 10, the PWM wave generation module generates PWM waves corresponding to the control transistors S1 to S4, respectively.
Fig. 11 shows the structure of the phase shift angle calculation module in the control device of a phase-shifted full-bridge circuit.
In this embodiment, the phase shift angle calculation module 92 includes:
and a voltage error calculation unit 921 for performing voltage error calculation according to the output voltage sampling signal and the preset voltage reference signal to obtain a first calculation result.
First proportional integral calculating section 922 performs proportional integral calculation on the first calculation result to obtain a second calculation result.
The current reference signal obtaining unit 923 obtains a current reference signal after filtering the second calculation result by using a filter.
The current error calculating unit 924 performs current error calculation based on the output current sampling signal and the current reference signal to obtain a third calculation result.
The second proportional-integral calculating unit 925 performs proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.
As shown in FIG. 12, an embodiment of the present invention discloses a welder power supply. The welder power supply comprises a control device 33 of a phase-shifted full bridge circuit as disclosed in any of the embodiments above. The detailed structural features and advantages of the control device of the phase-shifted full bridge circuit can be referred to the description of the above embodiments, and are not repeated herein.
Referring to fig. 12, the welder power supply further includes an EM 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 rectification module 35, an auxiliary power supply 36, and a fan 37. The EMI suppression module is connected to a power grid, and the rectification module is connected with a welding machine load. Fig. 12 is referred to for connection relationships among 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 inverter circuit, the high-frequency transformer, the rectification module, the auxiliary power supply, and the fan, and details thereof are not repeated in this embodiment.
In summary, the control method and device of the phase-shifted full-bridge circuit and the welding machine power supply of the invention have at least the following advantages:
the phase-shifted full-bridge circuit control method, the phase-shifted full-bridge circuit control device and the welding machine power supply disclosed by the embodiment of the invention generate the phase shift 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 that the lower pulse width modulation frequency is adopted when the load is smaller, and control the switch components by combining the phase shift angle and the pulse width modulation frequency, thereby achieving the purpose of reducing the electromagnetic interference and improving the electromagnetic compatibility of the phase-shifted full-bridge circuit.
The foregoing is a further detailed description of the invention in connection with specific preferred embodiments and it is not intended to limit the invention to the specific embodiments described. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (14)
1. The control method of the phase-shifted full-bridge circuit is characterized in that the phase-shifted full-bridge circuit is arranged in a welding machine power supply and comprises at least one full-bridge converter module, each full-bridge converter module comprises at least one bridge arm, and each bridge arm comprises a plurality of switch assemblies; the control method comprises the following steps:
s110, 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;
s120, calculating a phase shift angle corresponding to each full-bridge converter module 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, and adjusting the switching frequency corresponding to the switching component according to the comparison result;
and S140, 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 off.
2. The method for controlling a phase-shifted full-bridge circuit according to claim 1, wherein the predetermined hysteresis current threshold comprises a predetermined hysteresis current lower limit value; the step S130 includes:
and when the output current sampling signal is smaller than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component to a first preset frequency threshold value.
3. The method for controlling the phase-shifted full-bridge circuit according to claim 2, wherein the step S130 further comprises:
when the output current sampling signal is smaller than the preset hysteresis current lower limit value, acquiring the reduction ratio of the switching frequency corresponding to the switching component;
acquiring the proportion of the increase of the switching period corresponding to the switching component according to the proportion of the decrease of the switching frequency corresponding to the switching component;
and according to the increasing proportion of the switching period, increasing the dead time corresponding to each bridge arm in the same proportion.
4. The method for controlling a phase-shifted full-bridge circuit according to claim 2, wherein the predetermined hysteresis current threshold further comprises a predetermined hysteresis current upper limit value; the preset hysteresis current upper limit value is greater than the preset hysteresis current lower limit value; the step S130 further includes:
when the output current sampling signal is larger than the preset hysteresis current upper limit value, increasing the switching frequency corresponding to the switching component to a second preset frequency threshold value; wherein the second preset frequency threshold is greater than the first preset frequency threshold.
5. The method for controlling the phase-shifted full-bridge circuit according to claim 1, wherein the step S120 comprises:
performing voltage error calculation according to 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;
filtering the second calculation result by using a filter to obtain a current reference signal;
according to the output current sampling signal and the current reference signal, current error calculation is carried out to obtain a third calculation result;
and performing proportional integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.
6. The method for controlling the phase-shifted full-bridge circuit according to claim 5, wherein the step S120 comprises:
taking a difference value between a preset voltage reference signal and the output voltage sampling signal as a first calculation result;
and taking the difference value between the current reference signal and the output current sampling signal as a third calculation result.
7. The method for controlling the phase-shifted full-bridge circuit according to claim 1, wherein the step S140 comprises:
acquiring a duty ratio corresponding to each bridge arm; the duty ratios corresponding to the switch assemblies in the same bridge arm are the same;
and generating a pulse width modulation wave corresponding to each switching component according to the phase shift angle, the switching frequency and the duty ratio.
8. The method for controlling a phase-shifted full-bridge circuit according to claim 1, wherein each bridge arm comprises two switching elements, and the corresponding PWM waves of the switching elements in each bridge arm are complementary.
9. The method for controlling a phase-shifted full-bridge circuit according to claim 1, wherein said switching elements are silicon carbide field effect transistors.
10. A control device for a phase-shifted full bridge circuit, for implementing the control method according to claim 1, comprising:
the signal sampling module is used for 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;
the phase shift angle calculation module is used for calculating a 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 adjusting module is used for comparing the output current sampling signal with a preset hysteresis current threshold value and adjusting the switching frequency corresponding to the switching component according to a comparison result;
and the pulse width modulation wave generating module generates 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.
11. The control apparatus of claim 10, wherein the preset hysteresis current threshold comprises a preset hysteresis current lower limit; the switching frequency adjustment module is configured to:
and when the output current sampling signal is smaller than the preset hysteresis current lower limit value, reducing the switching frequency corresponding to the switching component to a first preset frequency threshold value.
12. The control apparatus of claim 11, wherein the switching frequency adjustment module is further configured to:
when the output current sampling signal is smaller than the preset hysteresis current lower limit value, acquiring the reduction proportion of the switching frequency corresponding to the switching component;
acquiring the proportion of the increase of the switching period corresponding to the switching component according to the proportion of the decrease of the switching frequency corresponding to the switching component;
and according to the increasing proportion of the switching period, increasing the dead time corresponding to each bridge arm in the same proportion.
13. The control apparatus of claim 10, wherein the phase shift angle calculation module comprises:
the voltage error calculation unit is used for performing voltage error calculation according to the output voltage sampling signal and a preset voltage reference signal to obtain a first calculation result;
the first proportional integral calculation unit is used for performing proportional integral calculation on the first calculation result to obtain a second calculation result;
the current reference signal acquisition unit is used for filtering the second calculation result by using a filter to obtain a current reference signal;
the current error calculation unit is used for calculating a current error according to the output current sampling signal and the current reference signal to obtain a third calculation result;
and the second proportional-integral calculation unit is used for performing proportional-integral calculation on the third calculation result to obtain a phase shift angle corresponding to each full-bridge converter module.
14. A welder power supply, characterized in that it comprises control means of a phase-shifted full-bridge circuit according to any of claims 10-13.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115765488A (en) * | 2022-12-16 | 2023-03-07 | 杭州锐健医疗科技有限公司 | Radio frequency ablation power supply circuit and control method thereof |
| CN117792106A (en) * | 2023-12-26 | 2024-03-29 | 广东浦立电气股份有限公司 | Phase-shifting full-bridge circuit control method, device, computer equipment and storage medium |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115765488A (en) * | 2022-12-16 | 2023-03-07 | 杭州锐健医疗科技有限公司 | Radio frequency ablation power supply circuit and control method thereof |
| CN117792106A (en) * | 2023-12-26 | 2024-03-29 | 广东浦立电气股份有限公司 | Phase-shifting full-bridge circuit control method, device, computer equipment and storage medium |
| CN117792106B (en) * | 2023-12-26 | 2024-06-04 | 广东浦立电气股份有限公司 | Phase-shifting full-bridge circuit control method, device, computer equipment and storage medium |
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