JP5429791B2 - Welding power supply - Google Patents

Description

  The present invention relates to a welding power source apparatus that performs feedback control to maintain an output voltage at a desired value.

  In order to maintain the output voltage of the welding power source at a predetermined value, an auxiliary winding is provided on the secondary side of the transformer, and feedback control is performed using this auxiliary voltage to maintain the output voltage at a predetermined value. However, since a leakage inductance exists in the transformer, a flyback voltage (counterelectromotive voltage) is generated on the secondary side of the transformer when each switching element forming the inverter circuit is cut off. In addition, there is a stray capacitance between the primary and secondary windings of the transformer, stray capacitance between the switching elements, and stray capacitance between the wirings. To do. When feedback control is performed using the auxiliary voltage including the flyback voltage and the parasitic vibration, the output voltage of the welding power source is controlled to be lower than a predetermined value. As a countermeasure, conventionally, an auxiliary voltage is detected in synchronization with the time when each switching element is turned on, and feedback control is performed using the auxiliary voltage. Hereinafter, conventional feedback control of a welding power source will be described.

  FIG. 8 is an electrical connection diagram of a conventional welding power source apparatus. In the figure, the DC power supply circuit is formed by a primary rectifier circuit DR1 that rectifies the output of a three-phase AC commercial power supply AC and converts it into a DC voltage, and a smoothing capacitor C1 that smoothes the voltage converted into a DC voltage. .

  The bridge-connected inverter circuit shown in FIG. 8 is formed by the first switching element TR1 to the fourth switching element TR4, the first switching element TR1 and the fourth switching element TR4 that form opposite sides, and the second switching element. The element TR2 and the third switching element TR3 form a pair, and the first switching element TR1 and the fourth switching element TR4 or the second switching element TR2 and the third switching element TR3 forming these pairs alternately turn on and off. Repeatedly converts DC voltage to high frequency AC voltage.

  The transformer INT converts the primary winding, the secondary winding that converts the high-frequency AC voltage on the primary side into a voltage suitable for arc machining, and converts the high-frequency AC voltage into a voltage suitable for feedback control. It is formed with the auxiliary winding which outputs. The output conversion circuit is formed by a secondary rectifier circuit DR2 and a DC reactor DCL. The secondary rectifier circuit DR2 rectifies the secondary output of the secondary winding of the transformer INT and converts it into a DC voltage suitable for arc machining. The DC reactor DCL smoothes the rectified DC voltage and supplies it to the load.

  The auxiliary rectifier circuit DR3 shown in FIG. 8 rectifies the output of the auxiliary winding of the transformer INT, and the auxiliary switching element SW becomes conductive when the first output control signal Sc1 and the second output control signal Sc2 are at a high level, The auxiliary rectified voltage rectified by the auxiliary rectifier circuit DR3 is supplied to the auxiliary voltage averaging circuit VRC. The auxiliary voltage averaging circuit VRC forms a low-pass filter with a resistor and a capacitor (not shown), averages the auxiliary rectified voltage, and outputs it as a feedback control signal Vrc.

  The error amplification circuit ER amplifies the error between the value of the predetermined output voltage setting signal Vr set by the output voltage setting circuit VR and the value of the feedback control signal Vrc, and outputs the result as an error amplification signal Er. The main control circuit SC performs pulse width modulation control for modulating the pulse width with a constant pulse frequency, performs pulse width modulation control in accordance with the value of the error amplification signal Er, and performs first output control with signals shifted from each other by a half cycle. The signal Sc1 and the second output control signal Sc2 are output.

  FIG. 9 is a waveform timing chart for explaining the operation of the conventional welding power source apparatus shown in FIG. 8. The waveform in FIG. 9A shows the first output control signal Sc1, and the waveform in FIG. Indicates the second output control signal Sc2. The waveform in FIG. 5C shows an OR signal Or obtained by performing OR logic of the first output control signal Sc1 and the second output control signal Sc2, and the waveform in FIG. 4D shows the auxiliary switch output signal Sw. (E) shows the feedback control signal Vrc, (F) shows the secondary voltage waveform N2 of the secondary winding of the transformer, and (G) shows the waveform of the transformer. The auxiliary voltage waveform N3 of the auxiliary winding of the device is shown.

Next, the operation of the prior art will be described using the waveform timing chart of FIG.
When the first output control signal Sc1 is input from the main control circuit SC shown in FIG. 8 to the inverter drive circuit SD, the inverter drive circuit SD outputs the first switching drive signal Tr1 and the fourth switching drive signal Tr4 to perform relative operations. The first switching element TR1 and the fourth switching element TR4 that form the facing sides are conducted. At this time, when a voltage is applied to the primary winding N1 of the transformer INT shown in FIG. 8, the secondary voltage waveform N2 shown in FIG. 9F is applied to the secondary winding of the transformer INT. Simultaneously, the auxiliary voltage waveform N3 shown in FIG. 9G is generated in the auxiliary winding. At this time, a flyback voltage is generated in the auxiliary voltage waveform N3 when each switching element is cut off.

  In the OR circuit OR shown in FIG. 8, when the first output control signal Sc1 shown in FIG. 9A becomes High level, the OR signal Or shown in FIG. 9C also becomes High level and the auxiliary switching element SW is turned on. Let At this time, the flyback voltage is removed by the auxiliary switching element SW, and the auxiliary switching signal Sw shown in FIG. 9D is supplied to the auxiliary voltage averaging circuit VRC. The auxiliary voltage averaging circuit VRC averages the auxiliary switching output signal Sw and outputs it as a feedback control signal shown in FIG.

  The error amplification circuit ER performs error amplification on the value of the output voltage setting signal Vr and the value of the feedback control signal Vrc and outputs the result as an error amplification signal Er. The main control circuit SC performs pulse width modulation control for modulating the pulse width with a constant pulse frequency, and controls the output of the first output control signal Sc1 in accordance with the value of the error amplification signal Er.

  When the first output control signal Sc1 shown in FIG. 8 becomes the Low level, the inverter drive circuit SD cuts off the first switching element TR1 and the fourth switching element TR4, and the OR signal Or shown in FIG. The auxiliary switching element SW is cut off and the supply of the auxiliary switching output signal Sw to the auxiliary voltage averaging circuit VRC is stopped.

  Subsequently, when the second output control signal Sc2 is input to the inverter drive circuit SD, the inverter drive circuit SD conducts the second switching element TR2 and the third switching element TR4 that form opposite sides. At this time, in the OR circuit OR, when the second output control signal Sc2 shown in FIG. 9B becomes High level, the OR signal Or shown in FIG. 9C also becomes High level, and the auxiliary switching element SW becomes conductive. . At this time, the flyback voltage is removed, and the rectified auxiliary switching signal Sw shown in FIG. 9D is supplied to the auxiliary voltage averaging circuit VRC. The auxiliary voltage averaging circuit VRC averages the auxiliary switching output signal Sw and outputs it as a feedback control signal shown in FIG.

  The error amplification circuit ER performs error amplification on the value of the output voltage setting signal Vr and the value of the feedback control signal Vrc and outputs the result as an error amplification signal Er. The main control circuit SC controls the output of the second output control signal Sc2 in accordance with the value of the error amplification signal Er.

  As described above, the auxiliary switching element SW supplies the auxiliary rectified voltage to the auxiliary voltage averaging circuit VRC when the first output control signal Sc1 and the second output control signal Sc2 are at the high level, and the auxiliary voltage averaging circuit VRC. Averages the supplied auxiliary rectified voltage and outputs it as a feedback signal. At this time, the accuracy of the output voltage is improved by removing unnecessary components such as a flyback voltage and an oscillating voltage generated when each switching element is cut off from the feedback signal. (For example, Patent Document 1)

Japanese Patent Laid-Open No. 9-15265

  If the auxiliary voltage output from the auxiliary winding of the transformer is detected when the first output control signal and the second output control signal are at the high level, the auxiliary voltage is generated when each switching element forming the inverter circuit is cut off. An auxiliary voltage from which a component causing an error such as a flyback voltage and an oscillating voltage is removed can be detected, and feedback control is performed using the auxiliary voltage to improve the accuracy of the output voltage of the welding power source.

However, since the transformer has a leakage inductance, even if each switching element forming the inverter circuit is made conductive and the primary voltage is applied to the primary side of the transformer, the secondary of the transformer is caused by the leakage inductance. An energy transmission delay time occurs in which the energy transmission is delayed. Within this energy transfer delay time, the output voltage on the secondary side of the transformer becomes substantially zero, and the energy transfer delay time becomes longer as the primary current value of the transformer increases.
Also, since the auxiliary winding of the transformer is excited with less energy than the secondary winding, the auxiliary voltage is quickly generated when the primary voltage is applied to the primary side of the transformer. Therefore, the output voltage generation time of the secondary winding of the transformer is delayed by the energy transmission delay time from the auxiliary voltage generation time of the auxiliary winding. When feedback control of the output voltage of the welding power source is performed using this auxiliary voltage, the difference between the output voltage generation time of the secondary winding of the transformer and the auxiliary voltage generation time of the auxiliary winding is small in the small current region. The output voltage of the power supply is controlled to a desired value, but in the large current range, the difference between the output voltage generation time of the secondary winding of the transformer and the auxiliary voltage generation time of the auxiliary winding becomes large. This causes a serious problem that the output voltage of the power supply becomes lower than a desired value.

  For example, although the energy transfer delay time is 0.05 μs when the output current is 25 A, it becomes long to 0.8 μs when the output current is 400 A. Recently, an inverter circuit used for a welding power source is required to have a high speed, and is often used at a cycle of 10 μs (100 KHz). At this time, when the maximum on-duty of the inverter circuit is 4.5 μs and the energy transfer delay time is 0.8 μs, the output voltage is about 15% lower than the desired value.

  Therefore, an object of the present invention is to provide a welding power source apparatus that can obtain a stable output voltage without being affected by the output current when the output voltage is feedback controlled using the auxiliary voltage of the auxiliary winding of the transformer. .

In order to solve the above-described problem, the first invention includes an inverter circuit that converts a DC voltage from a DC power supply circuit into a high-frequency AC voltage, a primary winding, a secondary winding, and an auxiliary winding. A transformer for converting a high-frequency AC voltage into a voltage suitable for a load, a secondary rectifier circuit for rectifying a secondary voltage output from a secondary winding of the transformer, and a second output from the secondary rectifier circuit A DC reactor that smoothes the secondary rectified voltage and supplies it to the load; a predetermined leakage inductance value of the transformer; and a primary current value and a primary voltage value of the transformer when the inverter circuit is conductive. Based on the calculation of the energy transfer delay time, the auxiliary voltage output from the auxiliary winding of the transformer starts detecting the auxiliary voltage when the energy transfer delay time elapses from the time when the inverter circuit is turned on. An auxiliary arithmetic control circuit that stops detection of the auxiliary voltage when the inverter circuit is cut off, an auxiliary voltage rectifier circuit that rectifies the detected auxiliary voltage, and averages the rectified auxiliary voltage and outputs it as a feedback control signal And an auxiliary voltage averaging circuit that performs a welding operation, and a main control circuit that controls a conduction time of the inverter circuit in accordance with an error between a value of the feedback control signal and a predetermined output setting value. It is a power supply device.

  In the first and second inventions, detection of the auxiliary voltage is started when a predetermined energy transmission delay time elapses from the time when the inverter circuit conducts the auxiliary voltage output from the auxiliary winding of the transformer. As a result, the difference between the output voltage generation time of the secondary winding of the transformer and the auxiliary voltage generation time of the auxiliary winding is reduced, and if the output voltage of the welding power source is feedback controlled using this auxiliary voltage, the output voltage decreases. Therefore, good welding can be obtained.

It is an electrical connection figure of the welding power supply device concerning Embodiment 1 of the present invention. FIG. 2 is a detailed view of an auxiliary control circuit TC shown in FIG. FIG. 3 is a waveform timing chart for explaining the operation of the first embodiment. FIG. 6 is an electrical connection diagram of a welding power source apparatus according to Embodiment 2. FIG. 5 is a detailed diagram of an auxiliary calculation control circuit TP shown in FIG. 4. FIG. 10 is a waveform timing chart for explaining the operation of the second embodiment. FIG. 6 is an electrical connection diagram of a welding power source apparatus according to Embodiment 3. It is an electrical connection figure of the welding power supply device of a prior art. It is a waveform timing diagram explaining operation | movement of the welding power supply device of a prior art.

FIG. 1 is an electrical connection diagram of a welding power source apparatus according to Embodiment 1 of the present invention.
In the figure, components having the same reference numerals as those in the electrical connection diagram of the conventional welding power source apparatus shown in FIG. 9 perform the same operations, and therefore, description thereof will be omitted and only components having different reference numerals will be described.

  The feedback control circuit of the first embodiment is formed by the auxiliary switching element SW, the auxiliary rectifier circuit DR3, the auxiliary voltage averaging circuit VRC, and the auxiliary control circuit TC shown in FIG. The auxiliary switching element SW is turned on in response to the auxiliary control signal Tc shown below and supplies the auxiliary voltage from the auxiliary winding to the auxiliary rectifier circuit DR3. The auxiliary rectifier circuit DR3 rectifies the auxiliary voltage and outputs it as an auxiliary rectified voltage. Subsequently, the auxiliary voltage averaging circuit VRC averages the auxiliary rectified voltage and outputs it as a feedback control signal Vrc.

  FIG. 2 is a detailed diagram of the auxiliary control circuit TC, which is formed by an OR logic circuit OR, a switch delay time circuit TB, an inverting circuit IN, and an AND logic circuit AND. First, the OR logic circuit OR is a first output control signal. The OR logic of Sc1 and the second output control signal Sc2 is performed and output as an OR logic signal Or.

  From the experimental results, the switch delay time circuit TB has an energy transfer delay time of 0.05 μs when the output current is 25 A, but increases to 0.8 μs when the output current is 400 A. Based on this result, for example, when the energy transfer delay time is set to 0.6 μs and the OR logic signal Or becomes the high level, the switch delay time signal Tb having a time of 0.6 μs is output. The AND logic circuit AND performs AND logic on the OR logic signal Or and the inverted signal obtained by inverting the switch delay time signal Tb, and outputs the result as the auxiliary control signal Tc.

FIG. 3 is a waveform timing chart for explaining the operation of the welding power supply device of the first embodiment.
The waveform in FIG. 5A shows the first output control signal Sc1, and the waveform in FIG. 4B shows the second output control signal Sc2. The waveform of FIG. 6C shows an OR logic signal Or obtained by performing an OR logic of the first output control signal Sc1 and the second output control signal Sc2, and the waveform of FIG. 4D shows the auxiliary rectified voltage signal Dr3. Indicates. The waveform of (E) in the figure shows the feedback control signal Vrc, and the waveform of (F) in the figure shows the waveform of the switch delay time signal Tb. The waveform in FIG. 10G shows the auxiliary control signal Tc, the waveform in FIG. 11H shows the secondary voltage waveform N2 of the secondary winding of the transformer, and the waveform in FIG. The auxiliary voltage waveform N3 of the auxiliary winding is shown, and the waveform (J) in the figure shows the output waveform Va of the auxiliary switching element. Hereinafter, a description will be given with reference to FIG.

  At time t = t1 shown in FIG. 3, when the first output control signal Sc1 shown in FIG. 3A becomes a high level, the first switching element TR1 and the fourth switching element TR4 forming the inverter circuit are turned on, A high-frequency AC voltage (not shown) is applied to the primary side of the main transformer INT.

  At time t = t1, the OR logic circuit OR shown in FIG. 2 performs the OR logic of the first output control signal Sc1 and the second output control signal Sc2, and outputs the OR logic signal Or shown in FIG. Set to High level. The switch delay time circuit TB outputs a switch delay time signal Tb having a pulse width of a predetermined time T1 when the OR logic signal Or shown in FIG.

  The AND logic circuit AND shown in FIG. 2 performs AND logic on the OR logic signal Or and the inverted signal of the switch delay time signal Tb, and outputs the result as the auxiliary control signal Tc shown in FIG.

  The auxiliary switching element SW shown in FIG. 1 becomes conductive when the auxiliary control signal Tc becomes High level at time t = t2, and supplies the auxiliary voltage waveform N3 of the auxiliary winding shown in FIG. 3 (I) to the auxiliary rectifier circuit DR3. To do. At this time, during the switch delay time signal Tb (time t = t1 to t2), the voltage supplied to the auxiliary rectifier circuit DR3 becomes substantially zero, the same as the time when the output voltage of the secondary winding of the transformer is generated (J The output waveform Va of the auxiliary switching element SW from which the output waveform Va of the auxiliary switching element SW shown in (3) is very small and the flyback voltage is also deleted is supplied to the auxiliary rectifier circuit DR3.

  The auxiliary rectifier circuit DR3 rectifies the output waveform Va of the auxiliary switching element SW shown in FIG. 3J and outputs an auxiliary rectified voltage signal Dr3 shown in FIG. The auxiliary voltage averaging circuit VRC shown in FIG. 1 averages the auxiliary rectified voltage signal Dr3 and supplies it to the error amplifier circuit ER as the feedback control signal Vrc shown in FIG.

  At time t = t3 shown in FIG. 3, when the first output control signal Sc1 shown in FIG. 3A becomes a low level, the first switching element TR1 and the fourth switching element TR4 forming the inverter circuit are cut off, The supply of the high-frequency AC voltage to the primary side of the main transformer INT is stopped.

  At time t = t3, the OR logic circuit OR shown in FIG. 2 performs an OR logic on the first output control signal Sc1 and the second output control signal Sc2, and outputs an OR logic signal Or shown in FIG. Set to Low level. The switch delay time circuit TB stops its operation when the OR logic signal Or shown in FIG.

  The AND logic circuit AND shown in FIG. 2 performs an AND logic of the OR logic signal Or and the inverted signal of the switch delay time signal Tb, and the auxiliary control signal Tc shown in FIG. Then, the auxiliary switching element SW is cut off when the auxiliary control signal Tc becomes Low level, and stops supplying the auxiliary voltage waveform N3 shown in FIG. 3I to the auxiliary rectifier circuit DR3.

At time t = t4 shown in FIG. 3, when the second output control signal Sc2 shown in FIG. 3B becomes a high level, the second switching element TR2 and the third switching element TR3 forming the inverter circuit are turned on, A high frequency alternating voltage is applied to the primary side of the main transformer INT.

  At time t = t4, the OR logic circuit OR shown in FIG. 2 performs an OR logic between the first output control signal Sc1 and the second output control signal Sc2, and outputs an OR logic signal Or shown in FIG. Set to High level. The switch delay time circuit TB outputs the switch delay time signal Tb having a pulse width of a predetermined time T1 again when the OR logic signal Or shown in FIG.

  The AND logic circuit AND shown in FIG. 2 performs AND logic on the OR logic signal Or and the inverted signal of the switch delay time signal Tb, and outputs the result as the auxiliary control signal Tc shown in FIG.

  The auxiliary switching element SW shown in FIG. 1 conducts when the auxiliary control signal Tc becomes High level at time t = t5, and supplies the auxiliary voltage waveform N3 of the auxiliary winding shown in FIG. 3 (I) to the auxiliary rectifier circuit DR3. To do. At this time, during the switch delay time signal Tb (time t = t4 to t5), the voltage supplied to the auxiliary rectifier circuit DR3 becomes substantially zero, and the time when the output voltage of the secondary winding of the transformer is generated (J The output waveform Va of the auxiliary switching element SW from which the output waveform Va of the auxiliary switching element SW shown in (3) is very small and the flyback voltage is also deleted is supplied to the auxiliary rectifier circuit DR3.

  The auxiliary rectifier circuit DR3 rectifies the output waveform Va of the auxiliary switching element SW shown in FIG. 3J and outputs an auxiliary rectified voltage signal Dr3 shown in FIG. The auxiliary voltage averaging circuit VRC shown in FIG. 1 averages the auxiliary rectified voltage signal Dr3 and supplies it to the error amplifier circuit ER as the feedback control signal Vrc shown in FIG.

  At time t = t6 shown in FIG. 3, when the second output control signal Sc2 shown in FIG. 3A becomes a low level, the second switching element TR2 and the third switching element TR3 forming the inverter circuit are cut off, The supply of the high-frequency AC voltage to the primary side of the main transformer INT is stopped.

  At time t = t6, the OR logic circuit OR shown in FIG. 2 performs an OR logic on the first output control signal Sc1 and the second output control signal Sc2, and outputs an OR logic signal Or shown in FIG. Set to Low level. The switch delay time circuit TB stops its operation when the OR logic signal Or shown in FIG.

  The AND logic circuit AND shown in FIG. 2 performs an AND logic of the OR logic signal Or and the inverted signal of the switch delay time signal Tb, and the auxiliary control signal Tc shown in FIG. Then, the auxiliary switching element SW is cut off when the auxiliary control signal Tc becomes Low level, and stops supplying the auxiliary voltage waveform N3 shown in FIG. 3I to the auxiliary rectifier circuit DR3. Thereafter, the same operation as described above is performed.

  From the above, the difference between the generation time point of the secondary voltage waveform N2 of the secondary winding of the transformer shown in FIG. 3H and the generation time point of the output waveform Va of the auxiliary switching element shown in FIG. Therefore, if the feedback control is performed using the auxiliary voltage whose difference from the time of occurrence is small, a decrease in the welding voltage can be suppressed.

  FIG. 4 is an electrical connection diagram of the welding power source apparatus according to the second embodiment. In the same figure, components having the same reference numerals as those in the electrical connection diagrams of the welding power source apparatus shown in FIGS. 1, 2 and 9 perform the same operations, and thus description thereof will be omitted.

  The input current detection circuit ID shown in FIG. 4 detects the primary current of the transformer INT and outputs it as a primary current detection signal Id, and the input voltage detection circuit VI detects the primary voltage of the transformer INT and detects the primary current. Output as voltage detection signal Id.

  The feedback control circuit is formed by the auxiliary switching element SW, the auxiliary rectifier circuit DR3, the auxiliary voltage averaging circuit VRC, and the auxiliary arithmetic control circuit TP shown in FIG. The auxiliary switching element SW is turned on in response to the auxiliary calculation control signal Tp shown below, and supplies the auxiliary voltage from the auxiliary winding to the auxiliary rectifier circuit DR3. The auxiliary rectifier circuit DR3 rectifies the auxiliary voltage and outputs it as an auxiliary rectified voltage. Subsequently, the auxiliary voltage averaging circuit VRC averages the auxiliary rectified voltage and outputs it as a feedback control signal Vrc.

  FIG. 5 is a detailed diagram of the auxiliary operation control circuit TP, which is formed by an OR logic circuit OR, a switch delay operation time limit circuit TO, an inverting circuit IN, and an AND logic circuit AND. First, the OR logic circuit OR has a first output. The OR logic of the control signal Sc1 and the second output control signal Sc2 is performed and output as an OR logic signal Or.

The switch delay calculation time limit circuit TO starts calculation when the OR logic signal Or becomes High level, sets the leakage inductance value of the transformer INT that has been preliminarily stored as Ls, and detects the primary current value IN1 and the primary current of the detected transformer INT. Based on the voltage value VN1, the energy transfer delay time T2 of the transformer INT is calculated.
T2 = (IN1 × Ls) / VN1
And is output as a switch delay calculation time limit signal To. The AND logic circuit AND performs AND logic on the OR logic signal Or and the inverted signal obtained by inverting the switch delay operation time limit signal To and outputs the result as the auxiliary operation control signal Tp.

FIG. 6 is a waveform timing chart for explaining the operation of the welding power supply device of the second embodiment.
The waveform in FIG. 5A shows the first output control signal Sc1, and the waveform in FIG. 4B shows the second output control signal Sc2. The waveform of FIG. 6C shows an OR logic Or obtained by performing OR logic of the first output control signal Sc1 and the second output control signal Sc2, and the waveform of FIG. 4D shows the primary current detection signal. Indicates. The waveform in FIG. 4D shows the primary current detection signal Id, the waveform in FIG. 1E shows the primary voltage detection signal Vd, the waveform in FIG. 1F shows the feedback control signal Vrc, The waveform of FIG. (E) shows the waveform of the switch delay calculation time limit signal To. The waveform in FIG. 10G shows the auxiliary calculation control signal Tp, the waveform in FIG. 10I shows the secondary voltage waveform N2 of the secondary winding of the transformer, and the waveform in FIG. The auxiliary voltage waveform N3 of the auxiliary winding is shown, and the waveform of FIG. 4K shows the output waveform Va of the auxiliary switching element. Hereinafter, a description will be given with reference to FIG.

  At time t = t1 shown in FIG. 3, when the first output control signal Sc1 shown in FIG. 6A is at a high level, the first switching element TR1 and the fourth switching element TR4 forming the inverter circuit are turned on, A high-frequency AC voltage (not shown) is applied to the primary side of the main transformer INT.

The switch delay calculation time limit circuit TO starts calculation when the OR logic signal Or becomes High level, sets the leakage inductance value of the transformer INT that has been preliminarily stored as Ls, and detects the primary current value IN1 and the primary current of the detected transformer INT. Based on the voltage value VN1, the energy transfer delay time T2 of the transformer INT is calculated.
T2 = (IN1 × Ls) / VN1
Is obtained as a switch delay calculation time limit signal To having a pulse width T2 shown in FIG. 6 (G). Then, the AND logic circuit AND performs AND logic on the OR logic signal Or and the inverted signal obtained by inverting the switch delay calculation time limit signal To and outputs the result as the auxiliary calculation control signal Tp shown in FIG.

  The auxiliary switching element SW shown in FIG. 1 becomes conductive when the auxiliary calculation control signal Tp becomes High level at time t = t2, and the auxiliary voltage waveform N3 of the auxiliary winding shown in FIG. 6 (J) is supplied to the auxiliary rectifier circuit DR3. Supply. At this time, during the switch delay calculation time limit signal To (time t = t1 to t2), the voltage supplied to the auxiliary rectifier circuit DR3 becomes substantially zero, which is the same as the time when the output voltage of the secondary winding of the transformer is generated ( The output waveform Va of the auxiliary switching element SW in which the difference from the generation time point of the output waveform Va of the auxiliary switching element SW shown in k) becomes substantially zero and the flyback voltage is deleted is supplied to the auxiliary rectifier circuit DR3.

  The auxiliary rectifier circuit DR3 rectifies the output waveform Va of the auxiliary switching element SW shown in FIG. 3K and supplies it to the auxiliary voltage averaging circuit VRC. The auxiliary voltage averaging circuit VRC averages the auxiliary rectified voltage signal and supplies it to the error amplifier circuit ER as the feedback control signal Vrc shown in FIG.

  At time t = t3 shown in FIG. 3, when the first output control signal Sc1 shown in FIG. 6A becomes a low level, the first switching element TR1 and the fourth switching element TR4 forming the inverter circuit are cut off, The supply of the high-frequency AC voltage to the primary side of the main transformer INT is stopped.

  At time t = t3, the OR logic circuit OR shown in FIG. 5 performs the OR logic of the first output control signal Sc1 and the second output control signal Sc2, and outputs the OR logic signal Or shown in FIG. Set to Low level. The switch delay calculation time limit circuit TO stops its operation when the OR logic signal Or shown in FIG. Then, after time t = t4, the same operation as described above is performed.

  From the above, the difference between the generation time point of the secondary voltage waveform N2 of the secondary winding of the transformer shown in FIG. 6 (I) and the generation time point of the output waveform Va of the auxiliary switching element shown in FIG. When the feedback control is performed using the corrected auxiliary voltage of the auxiliary winding, the welding voltage can be reduced over a wide range from a small current region to a large current region, and the output voltage can be accurately adjusted to a desired value. Can keep well.

  In the above-described second embodiment, the energy transfer delay time T2 is detected from the primary current value IN1 and the primary voltage value VN1 of the transformer INT, which is obtained from the energy transfer delay approximation formula of T2 = (IN1 × Ls) / VN1. However, the energy transfer delay time may be obtained by setting either the primary current value or the primary voltage value to a predetermined value.

  FIG. 7 is an electrical connection diagram of the welding power source apparatus according to the third embodiment. In the figure, components having the same reference numerals as those in the electrical connection diagrams of the welding power source apparatus shown in FIGS. 4, 5, and 9 perform the same operations, and thus description thereof will be omitted, and only components having different reference numerals will be described.

  The output current detection circuit OD shown in FIG. 7 detects the output current and outputs it as an output current detection signal Od.

  The primary current / voltage conversion circuit OI converts the primary current IN1 from the value of the output current detection signal Od according to the winding ratio of the transformer INT, and turns the winding of the transformer INT from the value of the auxiliary voltage averaging signal Vrc. The primary voltage VN1 is also converted according to the line ratio.

The switch delay calculation time limit circuit TO starts calculation when the OR logic signal Or becomes High level, sets the leakage inductance value of the transformer INT that has been preliminarily stored as Ls, and detects the primary current value IN1 and the primary current of the detected transformer INT. Based on the voltage value VN1, the energy transfer delay time T2 of the transformer INT is calculated.
T2 = (IN1 × Ls) / VN1
And is output as a switch delay calculation time limit signal To.
The AND logic circuit AND performs AND logic on the OR logic signal Or and the inverted signal obtained by inverting the switch delay operation time limit signal To and outputs the result as the auxiliary operation control signal Tp.
Thereafter, since the same operation as that of the second embodiment is performed, the description of the operation is omitted.

AND AND logic circuit C1 smoothing capacitor DCL DC reactor DR1 primary rectifier circuit DR2 secondary rectifier circuit DR3 auxiliary rectifier circuit ER error amplifier circuit Er error amplifier signal ID input current detection circuit Id input current detection signal IN inverter circuit INT main transformer M Workpiece OD Output current detection circuit Od Output current detection signal OI Primary current / voltage conversion circuit OR OR logic circuit Or OR logic signal SC main control circuit Sc1 first output control signal Sc2 second output control signal SD inverter drive Circuit SW Auxiliary switching element Sw Auxiliary switch output signal TC Auxiliary control circuit Tc Auxiliary control signal TB Switch delay time circuit Tb Switch delay time signal TO Switch delay operation time circuit To Switch delay operation time signal
TP Auxiliary calculation control circuit Tp Auxiliary calculation control signal TH Torch TS Start switch Ts Start signal TR1 First switching element TR2 Second switching element TR3 Third switching element TR4 Fourth switching element Tr1 First switching element drive signal Tr2 Second switching element Drive signal Tr3 Third switching element drive signal Tr4 Fourth switching element drive signal VR Output voltage setting circuit Vr Output voltage setting signal VRC Auxiliary voltage averaging circuit Vrc Feedback control signal

Claims (1)

An inverter circuit for converting a DC voltage from a DC power supply circuit into a high-frequency AC voltage, a transformer having a primary winding, a secondary winding, and an auxiliary winding and converting the high-frequency AC voltage into a voltage suitable for a load; A secondary rectifier circuit that rectifies the secondary voltage output from the secondary winding of the transformer, and a DC reactor that smoothes the secondary rectified voltage output from the secondary rectifier circuit and supplies it to the load, An energy transfer delay time is calculated based on a predetermined leakage inductance value of the transformer and a primary current value and a primary voltage value of the transformer when the inverter circuit is conducting, and The auxiliary voltage output from the winding starts detecting the auxiliary voltage when the energy transmission delay time elapses from the time when the inverter circuit is turned on, and detects the auxiliary voltage when the inverter circuit is cut off. An auxiliary arithmetic control circuit to stop, the auxiliary voltage rectifier circuit for rectifying the detected auxiliary voltage, the auxiliary voltage averaging circuit for outputting the rectified auxiliary voltage and the average value as a feedback control signal, the feedback A welding power supply apparatus comprising: a main control circuit that controls a conduction time of the inverter circuit in accordance with an error between a value of the control signal and a predetermined output setting value.

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