Source: https://patents.google.com/patent/JPWO2010137278A1/en
Timestamp: 2020-01-27 19:18:44
Document Index: 79218396

Matched Legal Cases: ['art 11', 'art 6', 'art 8', 'art 10', 'art 12', 'art 41']

JPWO2010137278A1 - Inverter control device and inverter control method - Google Patents
JPWO2010137278A1
JPWO2010137278A1 JP2011515875A JP2011515875A JPWO2010137278A1 JP WO2010137278 A1 JPWO2010137278 A1 JP WO2010137278A1 JP 2011515875 A JP2011515875 A JP 2011515875A JP 2011515875 A JP2011515875 A JP 2011515875A JP WO2010137278 A1 JPWO2010137278 A1 JP WO2010137278A1
JP2011515875A
JP4784717B2 (en
憲和 大崎
2009-05-27 Priority to JP2009127359 priority
2010-05-24 Priority to PCT/JP2010/003458 priority patent/WO2010137278A1/en
2010-05-24 Priority to JP2011515875A priority patent/JP4784717B2/en
2011-10-05 Publication of JP4784717B2 publication Critical patent/JP4784717B2/en
2012-11-12 Publication of JPWO2010137278A1 publication Critical patent/JPWO2010137278A1/en
The inverter control device of the present invention drives a switching circuit on one side with a fixed conduction width, and drives the other switching circuit according to an output state by a pulse width modulation system, a phase control system, or a drive signal width control system by a phase control system By switching to, high-accuracy control at the time of small output is realized while suppressing heat generation of the switching element.
In general, the inverter-controlled welding machine includes an inverter circuit having a full bridge configuration. And an inverter control welding machine drives power semiconductor elements, such as IGBT and MOSFET which are switching elements which usually comprise a bridge circuit with the inverter frequency of about several kHz or more and about 100 kHz or less. At the same time, the inverter-controlled welding machine compares the output current and the output current set value, or compares the output voltage and the output voltage set value, and controls the energization time of the power conversion transformer as the welding output. An output having preferable current characteristics and voltage characteristics is obtained.
In the following, three types of welding machines are described: a PWM method, a phase control method, and a one-side bridge fixed conduction width PWM control method.
FIG. 11 shows a schematic configuration of a main part of an arc welder provided with an inverter control circuit according to a conventional PWM method.
In FIG. 11, the first rectification unit 5 rectifies a three-phase or single-phase AC input, and the first switching element 1 and the second switching element 4 convert the output of the first rectification unit 5 into an AC. The second rectifier 7 rectifies the output of the transformer 6 for power conversion, and the output current detector 8 detects the output current. The current detection unit 9 converts the signal of the output current detector 8 into a feedback signal, and the output setting unit 12 presets an average value and an effective value for a predetermined period of the welding current and welding voltage as the output of the welding machine. Is arranged for. The error amplifying unit 11 obtains and amplifies the error between the output signal of the current detecting unit 9 and the setting signal of the output setting unit 12, and the inverter drive basic pulse generation unit 13 generates a drive waveform that is the basis of inverter control. A pulse width modulation unit (hereinafter referred to as “PWM” unit) 14 outputs a control signal for controlling the conduction width of the switching element 1 and the switching element 4 in accordance with the error amplification signal of the error amplification unit 11. The drive circuits 21, 22, 23, and 24 convert the signals into drive signals for driving the switching elements 1 and 4 based on the output signal from the pulse width modulation unit 14 and output the drive signals. Here, the inverter control unit 29 surrounded by an alternate long and short dash line includes an inverter drive basic pulse generation unit 13 and a pulse width modulation unit 14.
In general, for output control of a non-consumable electrode type arc welder such as a TIG welder, current control is performed so that the output current matches the current set value. In addition, voltage control for making the output voltage coincide with the voltage set value is performed for output control of a consumable electrode arc welder such as a MAG welder. However, since the operation principle of the inverter used for the output control of the arc welder described above is the same, an operation of current control for controlling to a constant current value will be described below as an example of the operation of the inverter.
Since the switching element 1 and the switching element 4 and the switching element 2 and the switching element 3 are alternately turned on simultaneously, the output of the first rectifier 5 is converted into an alternating current. This alternating current is input to the primary winding of the transformer 6, converted into an output suitable for welding, and output from the secondary winding of the transformer 6. The output of the secondary winding of the transformer 6 is converted into direct current by the second rectification unit 7 and output from the welding machine as a welding output.
The error amplifying unit 11 has a high amplification factor, for example, 100 to 1000 times. Thus, the output current maintains a constant current characteristic corresponding to the output current set value even when the output load state changes and the output voltage changes.
In FIG. 12, the phase control unit 15 outputs a control signal for controlling the conduction of the elements from the switching element 1 to the switching element 4 according to the error amplification signal of the error amplification part 11.
The output current of the welding machine is detected by the output current detector 8, and a detection signal proportional to the output current is input from the output current detector 8 through the current detection unit 9 to the error amplification unit 11. In the error amplifying unit 11, the output set value from the output setting unit 12 and the signal from the current detection unit 9 are compared, and an error amplified signal of both is output. This error amplification signal is a phase difference corresponding to the level (signal magnitude) of the error amplification signal with respect to the inverter driving basic pulse waveform generated by the inverter driving basic pulse generation unit 13 in the phase control unit 15. Is converted into a drive pulse having the output.
A primary current flows from the first switching element 1 to the fourth switching element 4 through the transformer 6 during a period in which the conduction period of the switching element 1 and the conduction period of the switching element 4 overlap. Further, the primary current flows from the third switching element 3 to the second switching element 2 through the transformer 6 during a period in which the conduction period of the second switching element 2 and the conduction period of the third switching element 3 overlap. . In this way, the output of the first rectifying unit 5 is converted into an alternating current, and the secondary winding of the transformer 6 is converted into an output suitable for welding and output. The output of the secondary winding of the transformer 6 is converted into direct current by the second rectification unit 7 and is output from the welding machine as a welding output.
Since the error amplification unit 11 has a high amplification factor of 100 to 1000 times, the output current corresponds to the output current setting value even when the output load state changes and the output voltage changes. Maintain constant current characteristics.
FIG. 13 shows a configuration in which the phase control unit 15 in FIG. 12 is replaced with the PWM unit 14, and the operation thereof will be described below.
An example of the operation of the one-side bridge fixed conduction width PWM control type welding machine will be described later with reference to FIGS.
Next, operation | movement of the welding machine which performs control of three types of systems mentioned above using FIGS. 14A-C to FIG. 16A-C is demonstrated.
14A to 16C are schematic diagrams showing the operation of the inverter in the arc welding machine equipped with the conventional inverter control circuit. 14A to 14C show the operation in the PWM method, FIGS. 15A to 15C show the operation in the phase control method, and FIGS. 16A to 16C show the operation in the one-side bridge fixed conduction width PWM control method, respectively.
FIG. 14A, FIG. 15A, and FIG. 16A each show the operation state at the time of a small output, that is, when the inverter conduction period is short. FIG. 14B, FIG. 15B, and FIG. 16B show the operating state at the time of medium output, that is, the inverter conduction period is in the middle region. FIG. 14C, FIG. 15C, and FIG. 16C show the operation states at the time of large output, that is, when the inverter conduction period is long. 14A to 16C, the conduction state from the first switching element 1 to the fourth switching element 4, the conduction period of the inverter circuit, and the primary current waveform of the transformer 6 are schematically represented. ing.
Further, in FIGS. 14A to 14C to 16A to C, the part where an arrow is added to the operation waveforms from the first switching element 1 to the fourth switching element 4 represents the state of waveform change during output control. . The arrows added to the edge portion (falling portion) of the waveform indicate that the edge portion operates back and forth, the waveform expands and contracts, and the conduction period changes. The arrow added to the upper part of the waveform does not expand or contract the waveform, the conduction period does not change, and the entire waveform moves back and forth on the time axis. As a result, the phase of the waveform changes, indicating that the output is controlled as indicated by the inverter conduction period. Moreover, the horizontal stripe part in the transformer primary current waveform represents the regenerative current.
First, an operation example of a PWM type welding machine will be described with reference to FIGS. FIG. 14A shows the operation at the time of the small output, and shows that the switching element is not conducted and the transformer current does not flow at the minimum output due to a delay operation described later of the drive circuit. FIG. 14B shows an example of operation during medium output, and FIG. 14C shows an example of operation during high output. Both the first switching circuit 25 and the second switching circuit 26 operate in the PWM system.
According to FIG. 10A, the drive signal output from the inverter control unit 29 is delayed by the transistor 30 and the pulse transformer 31 that constitute the drive circuit 23. At the same time, the gate resistor 32 and the capacitance 33 inside the gate of the third switching element 3 are deformed. That is, as shown in FIG. 10B, the waveform at the point A is in a state where the conduction time is delayed and shortened at the point C representing the operation of the third switching element 3. For this reason, when the conduction time is close to the minimum conduction width, conduction, that is, the flow of the transformer current becomes unstable, and the transformer current may not flow.
Next, an operation example of a phase control type welding machine will be described with reference to FIGS. 15A to 15C show an operation example of an arc welder provided with an inverter control circuit according to a conventional phase control method. 15A, 15B, and 15C, the first switching circuit 25 shown in FIG. 12 operates with a predetermined conduction width, and the second switching circuit 26 controls the phase with respect to the first switching circuit 25. Has been working. At this time, the transformer current stops flowing when the second switching circuit 26 becomes non-conductive, that is, the second switching circuit 26 cuts off the transformer current, and the first switching circuit 25 does not cut off the current. Heat generation due to switching is suppressed.
However, since the area of the waveform represented by the horizontal stripes in the transformer current waveform is large, the regenerative current increases, and the heat generation of the regeneration diode of the switching element increases.
Next, an operation example of the welding machine using the one-side bridge fixed conduction width PWM control method will be described with reference to FIGS.
FIGS. 16A to 16C show an operation example of an arc welding machine including an inverter control unit 29 according to a pulse width modulation method of a conventional one-side bridge fixed conduction width. FIG. 16A shows the operation at the time of the small output, and shows that the third switching element and the fourth switching element are not conducted and the transformer current does not flow at the minimum output due to the delay operation of the drive circuit. . FIG. 16B shows the operation at the time of medium output, and FIG. 16C shows the operation at the time of large output. The second switching circuit 26 shown in FIG. 13 operates with respect to the first switching circuit 25 in the PWM method. At this time, the second switching circuit 26 cuts off the transformer current, and the first switching circuit 25 does not cut off the current, so that heat generation due to switching is suppressed.
9A and 9B schematically show the snubber capacitor charging current path for the switching element when the transformer current is near the minimum current. FIG. 9A shows the operation of the phase control method. FIG. 9B shows the operation of the one-side fixed conduction width PWM method.
However, pulse width modulation as described above is performed in a conventional PWM inverter control welder or an inverter control welder using a one-side bridge fixed conduction width pulse width modulation method. However, when the inverter conduction width is to be controlled with a minute pulse width of about 1 μs, the delay time on the drive path between the inverter control unit 29 and the switching element, particularly the delay time in the drive circuit and the operation delay time of the switching element. Occurs. As a result, the switching element cannot actually be driven, and there is a problem that high-precision control cannot be performed at the time of small output.
10A and 10B, the drive waveform signal output from the inverter control unit 29 operates the switching element 3 via the points A and B shown in FIG. 10A. However, at that time, the waveform in each part is deformed as shown in FIG. 10B due to the delay operation of the circuit components of the drive circuit 23 and the gate input capacitance 33 of the third switching element 3. As shown in FIG. 10B, the conduction waveform of the third switching element 3 at the point C is not only delayed with respect to the waveform at the point A, but also the conduction width is shortened. Then, as shown in FIG. 10C, when the width of the drive signal from the inverter control unit 29 becomes narrow, the switching element 3 does not conduct.
This is a state in which the switching element is not conductive at the minimum output in FIG. 14A showing the operation example of the welding machine performing PWM control. This has been a problem especially when the output current needs to be stably controlled at several amperes as in the TIG welder.
However, it takes a relatively long time for the switching elements constituting the first switching circuit 25 and the switching elements constituting the second switching circuit 26 to conduct simultaneously. For this reason, the regenerative current is increased, and there is a problem that the heat generation of the regenerative diode built in the switching element and the switching loss of the transistor portion are increased.
An inverter control device according to the present invention includes a first rectifier that rectifies an alternating current input, and a first switching element that is inserted between the outputs of the first rectifier and is connected in series to form a first switching circuit. Two switching elements, the third switching element and the fourth switching element connected in series, which are inserted between the outputs of the first rectifying unit and constitute the second switching circuit, and one of the primary windings is Power conversion connected to the connection between the first switching element and the second switching element, and the other of the primary windings connected to the connection between the third switching element and the fourth switching element Transformer, a second rectification unit that rectifies the output of the power conversion transformer, and an output detection unit that detects an output current or an output voltage from the second rectification unit, An output setting unit for setting an output current or an output voltage in advance, an error amplifying unit for obtaining an error between the signal from the output detecting unit and the signal from the output setting unit, and an output from the error amplifying unit An inverter control unit that outputs a signal for controlling the operation of the first switching circuit and the second switching circuit based on a signal, and the inverter control unit constitutes the first switching circuit. A first switching circuit control unit that outputs a drive signal for alternately conducting the first switching element and the second switching element; the third switching element that constitutes the second switching circuit; and A second switching circuit control unit that outputs a drive signal for alternately conducting the fourth switching element, The second switching circuit control unit generates and outputs a conduction width which is a time for conducting the third switching element and the fourth switching element based on a signal from the error amplification unit. Based on signals from the modulation unit and the error amplification unit, the third switching element and the fourth switching element, which are phase differences with respect to the conduction time of the first switching element and the second switching element, Based on the signal from the error amplifying unit, the phase control unit that generates and outputs the conduction time for conduction, the signal from the pulse width modulation unit, and the signal from the phase control unit are input. And a signal switching unit that outputs a signal from the width modulation unit or a signal from the phase control unit.
The inverter control device according to the present invention includes a first rectifying unit that rectifies an AC input, and a first switching element that is inserted between the outputs of the first rectifying unit and that is connected in series to form a first switching circuit. The third switching element and the fourth switching element that are inserted between the second switching element and the output of the first rectification unit and constitute the second switching circuit, and one of the primary windings is A power conversion transformer connected to the connection between the first switching element and the second switching element, the other of the primary windings being connected to the connection between the third switching element and the fourth switching element; A second rectifier that rectifies the output of the power conversion transformer, an output detector that detects an output current or output voltage from the second rectifier, and an output current or output in advance. Based on an output setting unit for setting a voltage, an error amplifying unit for obtaining an error between a signal from the output detecting unit and a signal from the output setting unit, and a signal from the error amplifying unit, And an inverter control unit that outputs a signal for controlling the operation of the second switching circuit. The inverter control unit includes a first switching element and a second switching element that constitute the first switching circuit. A first switching circuit control unit that outputs a driving signal for alternately conducting the second switching circuit, and a driving signal for alternately conducting the third switching element and the fourth switching element that constitute the second switching circuit. A second switching circuit control unit that outputs the second switching circuit control unit based on a signal from the error amplification unit. Based on the error amplification signal with respect to the drive signal from the first switching circuit control unit, the pulse width modulation unit that generates and outputs the conduction width that is the time for conducting the switching element and the fourth switching element, From the phase control unit that generates the phase difference drive signal, the drive pulse width change unit that changes the drive pulse width from the phase control unit based on the error amplification signal, the signal from the pulse width modulation unit, and the phase control unit And the signal from the drive pulse width changing unit, and based on the signal from the error amplifying unit, the signal from the pulse width modulating unit, the signal from the phase control unit, and the signal from the driving pulse width changing unit And a signal switching unit that outputs any of the above.
The inverter control device according to the present invention includes a first rectification unit that rectifies an AC input, and a first switching element that is inserted between the outputs of the first rectification unit and that is connected in series to form a first switching circuit. The third switching element and the fourth switching element that are inserted between the second switching element and the output of the first rectification unit and constitute the second switching circuit, and one of the primary windings is the first A power conversion transformer connected to a connection portion between the first switching element and the second switching element, the other of the primary windings being connected to the connection portion between the third switching element and the fourth switching element; A second rectifier that rectifies the output of the conversion transformer, an output detector that detects an output current or output voltage from the second rectifier, and an output current or output voltage in advance. An output setting unit for determining the error, an error amplifying unit for obtaining an error between the signal from the output detecting unit and the signal from the output setting unit, and a first switching circuit based on the signal from the error amplifying unit And an inverter control unit that outputs a signal for controlling the operation of the second switching circuit. The inverter control unit alternately switches the first switching element and the second switching element that constitute the first switching circuit. A first switching circuit controller for outputting a drive signal for conducting, and a third switching element for outputting a drive signal for alternately conducting a third switching element and a fourth switching element constituting the second switching circuit. The second switching circuit control unit, the second switching circuit control unit based on the signal from the error amplification unit, the third switch A pulse width modulation section that generates and outputs a conduction width that is a time for conducting the switching element and the fourth switching element, and an additional drive that outputs a drive signal added to the front of the drive signal output by the pulse width modulation section The configuration includes a pulse generation unit and a synthesis unit that synthesizes the output of the pulse width modulation unit and the output of the additional drive pulse generation unit.
The inverter control method of the present invention includes a first rectifier that rectifies an AC input and a first switching element that is inserted between the outputs of the first rectifier and is connected in series to form a first switching circuit. The third switching element and the fourth switching element that are inserted between the second switching element and the output of the first rectification unit and constitute the second switching circuit, and one of the primary windings is the first A power conversion transformer connected to a connection portion between the first switching element and the second switching element, the other of the primary windings being connected to the connection portion between the third switching element and the fourth switching element; A second rectifier that rectifies the output of the conversion transformer, an output detector that detects an output current or output voltage from the second rectifier, and an output current or output voltage in advance. An output setting unit for determining the error, an error amplifying unit for obtaining an error between the signal from the output detecting unit and the signal from the output setting unit, and a first switching circuit based on the signal from the error amplifying unit And an inverter control unit that outputs a signal for controlling the operation of the second switching circuit, and an inverter control method for an inverter control device comprising: Based on the pulse width change control step for changing the time during which the third switching element and the fourth switching element are turned on, and based on the signal from the error amplifying unit, the first switching element and the second switching element A phase control that changes the conduction time of the third switching element and the fourth switching element so as to have a phase difference with respect to the conduction time. And when the magnitude of the error amplification signal is in a predetermined first range, a pulse width control step is performed, and the magnitude of the error amplification signal is in the first range. If the size is smaller than the predetermined second range, at least the phase control step is performed.
By this method, the inverter control method can perform two controls, a PWM control method and a phase control method. Therefore, when the error amplification signal is larger than the predetermined threshold value, the regenerative current can be suppressed and the heat generation of the switching element can be suppressed by performing the control by the PWM control method. Further, when the error amplification signal is equal to or less than a predetermined threshold value, the output current can be accurately controlled by performing the control by the phase control method.
An arc welder using the inverter control device of the first embodiment will be described with reference to FIG. 1 and FIGS. FIG. 1 is a diagram illustrating a schematic configuration of a main part of the arc welder according to the first embodiment. 2A to 2C are schematic views showing the operation of the constituent members of the arc welder of the first embodiment. 2A to 2C are diagrams for explaining the operation of the arc welding machine, in which the welding output is a small output (FIG. 2A), a medium output (FIG. 2B), and a large output (FIG. 2C). The operation of the switching element, the inverter conduction period, and the transformer primary current waveform are respectively shown.
Note that the small output, medium output, and large output in the welding output are distinguished based on, for example, the magnitude of an error amplification signal from an error amplification unit 11 described later. That is, the case where the error amplification signal is equal to or smaller than the predetermined first threshold is set as a small output, and the case where the error amplification signal is larger than the predetermined first threshold and equal to or smaller than the predetermined second threshold is set as medium output. When the error amplification signal is larger than the predetermined second threshold, the output is high.
The inverter control unit 29 includes a first switching circuit control unit 27 and a second switching circuit control unit 28. Here, the first switching circuit control unit 27 generates a drive signal for alternately conducting the first switching element 1 and the second switching element 2. The second switching circuit control unit 28 generates a drive signal for alternately conducting the third switching element 3 and the fourth switching element 4.
2A to 2C show the operating state of the inverter in the present embodiment. 2A to 2C, FIG. 2A shows an operation state at the time of a small output, that is, when the inverter conduction period is short. FIG. 2B shows an operation state when the output is medium, that is, the inverter conduction period is in the middle region, and FIG. 2C shows an operation state when the output is large, that is, when the inverter conduction period is long. 2A, FIG. 2B, and FIG. 2C show the conduction state from the first switching element 1 to the fourth switching element 4, the conduction period of the inverter circuit, and the primary current waveform of the transformer 6 at the respective outputs. Is schematically represented.
Further, in FIGS. 2A to 2C, a portion where an arrow is added to the operation waveforms of the first switching element 1 to the fourth switching element 4 represents a state of waveform change during output control. Note that the arrow attached to the edge of the waveform (the falling part and the part with the black circle) moves as the edge moves back and forth, and the operation waveform expands and contracts to indicate the inverter conduction period. It shows that the output is controlled. The arrow added to the upper part of the waveform does not expand or contract the operation waveform, and the entire operation waveform moves back and forth. As a result, the phase of the operation waveform changes, indicating that the output is controlled in the conduction period as indicated by the inverter conduction period. Further, in the transformer primary current waveform, the horizontal stripe portion represents the regenerative current as described in the background art.
In the pulse width modulation unit 14, the inverter driving basic pulse waveform generated by the inverter driving basic pulse generation unit 13 is input. Based on this basic pulse waveform, a drive pulse having a width corresponding to the error amplification signal level from the error amplifier 11 is generated. This drive pulse is separated into two systems for the third drive circuit 23 and for the fourth drive circuit 24 every other pulse, and is input to the signal switching unit 19 as two drive signals for driving the inverter. The
Further, the phase control unit 15 receives the inverter driving basic pulse waveform generated by the inverter driving basic pulse generation unit 13. A drive pulse having a phase difference corresponding to the error amplification signal level is generated for this basic pulse waveform. This drive pulse is separated into two systems for the third drive circuit 23 and the fourth drive circuit 24 every other pulse, and is input to the signal switching unit 19 as two drive signals for driving the inverter. .
During the period in which the conduction period of the first switching element 1 and the conduction period of the fourth switching element 4 overlap, a primary current flows through the transformer 6 from the first switching element 1 to the fourth switching element 4. During the period in which the conduction period of the second switching element 2 and the conduction period of the third switching element 3 overlap, a primary current flows through the transformer 6 from the third switching element 3 to the second switching element 2. In this way, the output of the first rectifying unit 5 is converted into an alternating current, and is converted into an output suitable for welding from the secondary winding of the transformer 6 and output. Then, the output of the secondary winding of the transformer 6 is converted into direct current by the second rectification unit 7 and output from the welding machine as a welding output.
Next, operation | movement of the inverter control apparatus of the arc welding machine of this Embodiment 1 is demonstrated using FIG.
2A to 2C show an example of the operation of the constituent members of the arc welder, that is, an example of the circuit operation of the inverter control device. In FIG. 2A showing the control operation at the time of the small output including the vicinity of the minimum conduction width and FIG. 2B showing the control operation at the time of the medium output, the second switching circuit 26 is controlled by the phase control method with respect to the first switching circuit 25. An example that has been working. FIG. 2C shows an example in which the operation is controlled by the pulse width modulation method.
2A and 2B is set to the drive signal width at the time of switching from the pulse width modulation operation of FIG. 2C to the phase control operation of FIG. 2B. Thus, the control is set so that the control continuously shifts from the pulse width modulation operation to the phase control operation.
The drive signal width at the time of switching from the pulse width modulation operation to the phase control operation is, for example, a drive signal width smaller than 50% when the maximum conduction width is 100%.
As shown in FIG. 1, a capacitor 10 is provided in series with the primary winding of the transformer 6. As a result, the regenerative current can be reduced by the capacitor 10 as shown by the horizontal stripes of the transformer primary current waveform in FIGS. 2A, 2B, and 2C. Therefore, even when the control is performed by the phase control method, it is possible to suppress the switching element from generating heat due to the regenerative current as in the conventional phase control method. It is most effective for suppressing the regenerative current to set the capacity of the capacitor 10 to several μF with a 350 A output class arc welder. This has been confirmed experimentally.
In addition, by setting the operation of the first switching circuit 25 near the maximum conduction width, the third switching element 3 and the fourth switching element 4 perform the interruption of the transformer primary current. Thereby, since the 1st switching element 1 and the 2nd switching element 2 do not interrupt | block an electric current, the switching loss of the 1st switching element 1 and the 2nd switching element 2 is reduced significantly, and heat_generation | fever is suppressed. Can do.
As for switching between the pulse width modulation method and the phase control method, the pulse width modulation method is used when the signal from the error amplifying unit 11 is larger than a predetermined threshold, and the phase control method is used when the signal is smaller.
An arc welder using the inverter control device of the second embodiment will be described with reference to FIGS. 3 and 4A to 4C. FIG. 3 is a diagram showing a schematic configuration of a main part of the inverter control device of the arc welder in the second embodiment. 4A to 4C are diagrams for explaining the operation of the inverter control device of the arc welding machine according to the second embodiment. The operation of the switching element, the inverter conduction period, the transformer primary current in the inverter control device when the welding output is a small output (FIG. 4A), the medium output (FIG. 4B), and the large output (FIG. 4C). The waveform is shown.
In the present embodiment, the same configurations and the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
The main difference from the first embodiment is the configuration of the inverter control unit 29, which includes a drive pulse width changing unit 17 as will be described later. Further, the signal switching unit 19 switches the output signal from the pulse width modulation unit 14, the output signal from the phase control unit 15, and the output signal from the drive pulse width changing unit 17 to switch between the third drive circuit 23 and the third drive circuit 23. 4 is output to the drive circuit 24.
The operation of the inverter control apparatus of the arc welding machine configured as described above will be described.
The pulse width modulation unit 14 generates a driving pulse having a width based on the error amplification signal level (magnitude) based on the inverter driving basic pulse waveform generated by the inverter driving basic pulse generation unit 13. This drive pulse is separated into two systems every other pulse and is output as two systems of drive signals for driving the inverter.
The phase control unit 15 generates a drive pulse having a phase difference based on the error amplification signal level with respect to the inverter drive basic pulse waveform generated by the inverter drive basic pulse generation unit 13. This drive pulse is separated into two systems every other pulse, and is input to the signal switching unit 19 and also to the drive pulse width changing unit 17 as two systems of drive signals for driving the inverter.
When the error amplification signal is equal to or less than a predetermined first threshold value, the drive signal from the drive pulse width changing unit 17 is output. In addition, when the error amplification signal is larger than the predetermined first threshold and equal to or smaller than the predetermined second threshold, the drive signal from the phase control unit 15 is output. Further, when the error amplification signal is larger than a predetermined second threshold value, the drive signal from the pulse width modulation unit 14 is output. The first threshold value and the second threshold value can be set to predetermined values suitable for the welding, for example, from the result of actual welding.
By this method, when the error amplification signal is larger than a predetermined threshold value, it is possible to suppress the regenerative current and control the heat generation of the switching element by performing the control by the PWM control method. Further, when the error amplification signal is equal to or less than a predetermined threshold value, the output current can be accurately controlled by performing the control by the phase control method.
During the period in which the conduction period of the first switching element 1 and the conduction period of the fourth switching element 4 overlap, a primary current flows through the transformer 6 from the first switching element 1 to the fourth switching element 4. The primary current flows from the third switching element 3 to the second switching element 2 through the transformer 6 during a period in which the conduction period of the second switching element 2 and the conduction period of the third switching element 3 overlap. . In this way, the output of the first rectifying unit 5 is converted into an alternating current, and the secondary winding of the transformer 6 is converted into an output suitable for welding and output. The output of the secondary winding of the transformer 6 is converted into direct current by the second rectification unit 7 and output from the welding machine as a welding output.
Further, according to the inverter control apparatus of the second embodiment, the capacitor 10 is provided in series with the primary winding of the transformer 6 as shown in FIG. 3, so that the horizontal stripes of the transformer primary current waveform of FIGS. As shown by the line, the regenerative current can be reduced compared to the case where the capacitor 10 is not provided. In any state from FIG. 4A to FIG. 4C, the regenerative current can be reduced. This indicates that the heat generation of the switching element that is generated by the regenerative current in the conventional phase control method can be significantly suppressed.
Further, the operation of the first switching circuit 25 is set near the maximum conduction width. As a result, the transformer primary current is cut off by the third switching element 3 and the fourth switching element 4. Therefore, since the first switching element 1 and the second switching element 2 do not cut off the current, the switching loss of the first switching element 1 and the second switching element 2 can be greatly reduced to suppress heat generation. It becomes possible.
Further, by performing the same operation as the conventional phase control operation at the minimum output, it is possible to prevent the transformer current from being applied due to the charging current to the second snubber capacitor 36.
As described above, according to the inverter control device of the second embodiment, the first switching circuit 25 that is a switching circuit on one side is driven with a fixed conduction width. The second switching circuit 26, which is the other switching circuit, is driven by the pulse width modulation method when the output is large, and is driven by the phase control method when the output is medium, and the regenerative current is connected by the capacitor 10 connected in series to the transformer primary side. Suppress. As a result, it is possible to realize an inverter welder that combines the advantages of the pulse width modulation method and the phase control method, that is, enables highly accurate control at the time of small output while greatly suppressing heat generation of the switching element.
Further, the current control using the output current detector 8 and the output current detector 9 in the inverter control device of the second embodiment has been described. In this current control, it goes without saying that the same operation is performed when the output current detector is replaced with the output voltage detector 20 and the voltage control is performed.
In the third embodiment, the same configurations and locations as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.
6A to 6C show the operation state of the inverter control device according to the third embodiment. FIG. 6A shows an operation state when the output is small, that is, when the inverter conduction period is short. FIG. 6B shows an operation state at the time of medium output, that is, the inverter conduction period is in the middle region. FIG. 6C shows an operating state at the time of high output, that is, when the inverter conduction period is long. 6A to 6C schematically show the conduction state from the first switching element 1 to the fourth switching element 4, the conduction period of the inverter circuit, and the transformer primary current waveform. .
In FIG. 6A to FIG. 6C, the part where an arrow is added to the operation waveform from the first switching element 1 to the fourth switching element 4 represents the state of waveform change during output control. An arrow added to the edge portion (falling portion with a black circle) of the operation waveform indicates that the edge portion moves back and forth to operate, and the operation waveform expands and contracts. Moreover, the horizontal stripe part in the transformer primary current waveform represents the regenerative current.
The additional drive pulse generation unit 16 outputs a signal for adding a drive pulse for a fixed time immediately before the drive pulse output from the pulse width modulation unit 14.
6B and 6C show the control operation at the time of medium output and large output. The second switching circuit 26 is operating with the pulse width modulation method with respect to the first switching circuit 25.
Further, according to the inverter control device of the third embodiment, the regenerative current is reduced by the capacitor 10 as shown by the horizontal stripes of the transformer primary current waveform in FIG. For this reason, in any state of FIG. 6A to FIG. 6C, the regenerative current is sharply reduced. This indicates that heat generation of the switching element due to the regenerative current can be significantly suppressed.
Further, no regenerative current is generated as shown at T3 and T4 in FIG. 7B. Then, as shown in the waveform of the fourth switching element 4 represented by Q4 in FIG. 7A, the fourth switching element 4 represented by Q4 is Q1 by the drive signal added immediately before the point A of the drive signal. The first switching element 1 that is represented conducts quickly. For this reason, the loss at the time of ON of the 4th switching element 4 represented by Q4 can also be reduced.
However, in the inverter control device according to the third embodiment, the drive signal output from the drive additional drive pulse generator 16 output from the pulse width modulator 14 is added and synthesized. As a result, even if the welding output is near the minimum output and the drive signal of the pulse width modulation unit 14 is short, the combination of the drive signals of the additional drive pulse generation unit 16 has a certain length. Thus, the output current does not become zero even near the minimum output, and a minute current can be controlled.
In the first to third embodiments described above, the drive signal output from the inverter drive basic pulse generation unit 13 for driving the first switching circuit 25 has a fixed conduction width. However, if the drive signal output from the inverter drive basic pulse generation unit 13 is a signal that turns off with a delay from the turn-off timing of the drive signal for the second switching circuit 26, the first to third embodiments. The same effect as the effect can be obtained. Accordingly, the drive width of the drive signal output from the inverter drive basic pulse generator 13 changes between the timing when the drive signal for the second switching circuit 26 is turned off and the maximum conduction width of the first switching circuit 25. It may be a drive signal.
In addition, in Embodiments 1 to 3 described above, by adding a polarity inversion function to the second rectification unit 7, Embodiments 1 to 3 can be applied to an AC welding arc welder.
DESCRIPTION OF SYMBOLS 1 1st switching element 2 2nd switching element 3 3rd switching element 4 4th switching element 5 1st rectification part 6 Transformer 7 2nd rectification part 8 Current detector 9 Current detection part 10 Capacitor 11 Error amplification part 12 output setting unit 13 inverter drive basic pulse generation unit 14 pulse width modulation unit 15 phase control unit 16 additional drive pulse generation unit 17 drive pulse width change unit 19 signal switching unit 20 voltage detection unit 21 first drive circuit 22 second Drive circuit 23 Third drive circuit 24 Fourth drive circuit 25 First switching circuit 26 Second switching circuit 27 First switching circuit control unit 28 Second switching circuit control unit 29 Inverter control unit 30 Transistor 31 Pulse Transformer 32 Gate resistance 33 Gate internal capacitance 34 Second snubber resistance 35 Fourth scan Naver resistor 36 1st snubber capacitor 37 2nd snubber capacitor 38 Output terminal 39 Output terminal 40 1st synthetic | combination part 41 2nd synthetic | combination part
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JP4784717B2 JP4784717B2 (en) 2011-10-05
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