JPH09285137A - Capacitor discharge type resistance welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment advantageous in cost and space which prevents irregularity of welding equality. SOLUTION: When a start command is inputted in a current pattern circuit 26, it outputs a predetermined current pattern signal. An instantaneous PWM circuit 27 outputs PWM signal, in such a manner that a current detection signal from a current detector 321 coincides with the current pattern signal. A change- over circuit 14 alternately selects either one of gate circuits 24, 25 wherever the start command is inputted, and sends the PWM signal to the selected circuit. Thereby IGBT's (switching elements) 20a, 20d or 20b, 20c are turned on, and a discharging current from a capacitor 5 flows through the primary side of a transformer 7. A level detection circuit 23 monitors the voltage of the capacitor 5 after start of discharge. When the voltage level falls down to a discharge limit voltage, the detection circuit 23 stops the operation of the gate circuits 24, 25 to stop discharge of the capacitor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor discharge type resistance welding apparatus for spot welding by discharging the electric charge of a capacitor.

[0002]

2. Description of the Related Art FIG. 8 is a circuit diagram showing a structure of a conventional capacitor discharge type resistance welding apparatus. In this figure, the AC power from the AC power supply 1 is converted into DC power by a converter 2 formed by a thyristor bridge.
The capacitor 5 is charged by this DC power via the reactor 3. Reference numeral 4 is a reverse voltage blocking diode.

The capacitor 5 includes thyristors 6a and 6a.
The switching circuit 6 formed by b, 6c and 6d is connected, and the discharge current of the capacitor 5 flows to the primary side of the transformer 7 via the switching circuit. The welding electrode 8 is connected to the secondary side of the transformer 7.

The capacitor 5 is discharged according to a constant determined by the inductance of the discharge circuit and the resistance of the weld. The discharge circuit of this capacitor 5 is equivalently an LCR circuit, and its discharge is resonant,
The diode 4 prevents the reverse voltage from being applied to the capacitor 5.

The detection signal of the voltage of the capacitor 5 is sent to the voltage detection circuit 10, and the detection signal of the current flowing through the converter 2 is sent to the amplifier 12 by the current detector 9. The voltage reference V _D ^* is adapted to be sent to the amplifier 11, which in turn supplies this voltage reference V _D ^*.
And the deviation from the voltage detection signal from the voltage detection circuit 10 are output to the amplifier 12 as a current reference. The amplifier 12 outputs the deviation between the current reference and the current detection signal from the current detector 9 to the phase circuit 13, and the phase circuit 13 controls the phase of the thyristor of the converter 2 so that the deviation becomes zero. To do.

When the switching circuit 14 receives a start signal,
Either one of the trigger circuits 15 and 16 is selected and a trigger command is output to it. For example, the trigger circuit 1
When 5 is selected, the trigger circuit 15 operates the thyristor 6
Turn on a and 6d. As a result, the charge of the capacitor 5 is changed from the capacitor 5 to the thyristor 6a to the transformer 7.
Flow along the path of the primary side of thyristor 6d → capacitor 5. Then, in the next start command, the trigger circuit 1
6 is selected, and the trigger circuit 16 has thyristors 6b and 6c.
Turn on. As a result, the charge of the capacitor 5 is changed from the capacitor 5 to the thyristor 6c to the primary side of the transformer 7.
The thyristor 6b and the capacitor 5 flow along the path.
In this way, the direction of the current flowing through the primary side of the transformer 7 is switched for each start command, so that the transformer 7 is prevented from being saturated.

FIG. 9 is a waveform diagram showing changes in the voltage V ₅ of the capacitor 5 and the current I flowing through the primary side of the transformer 7 during discharging. As shown in this figure, after the start command is issued at time t ₁ , the current I increases until it reaches the peak value, and then decreases at time t ₂ until it becomes zero. On the other hand, the voltage V ₅ continues to decrease from time t ₁ to time t ₂ .

[0008]

In the above-mentioned conventional device, the total discharge charge amount can be adjusted by changing the discharge voltage of the capacitor 5, but the instantaneous value of the current during discharge is controlled. I can't do it. Therefore, when the resistance value of the welded part or the inductance of the discharge circuit changes during welding, the discharge waveform also changes,
There were variations in the welding quality.

Further, the capacitor 5 in the conventional device is
Since the electric charge is completely discharged, deterioration of the dielectric is likely to occur. Therefore, it is necessary to use a capacitor dedicated to charging and discharging as the capacitor 5,
Since the charge / discharge capacitor is expensive and large, it is disadvantageous in terms of cost and space.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a capacitor discharge type resistance welding apparatus which prevents variations in welding quality and is advantageous in terms of cost and space.

[0011]

As a means for solving the above-mentioned problems, the invention according to claim 1 converts AC power from an AC power supply into DC power to charge a capacitor and inputs a start command. When this occurs, the discharge current from this capacitor is passed through the switching circuit to the primary side of the transformer to supply current to the welding electrode connected to the secondary side of the transformer. In the device, a current pattern circuit that outputs a predetermined current pattern signal based on the input of the start command, a current detector that detects a current flowing through the primary side of the transformer, and a current pattern from the current pattern circuit. A signal and an instantaneous PWM circuit that outputs a PWM signal based on the input of the current detection signal from the current detector, and the value of the current detection signal is the current pattern. To match the value, to perform based switching control on the switching circuit to the PWM signal, characterized by.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided capacitor voltage detection means for detecting the voltage of the capacitor, and when the voltage of the capacitor drops below a set level, the switching circuit is provided. It is characterized in that the current output from is stopped.

According to a third aspect of the present invention, in the second aspect of the present invention, the set level of the voltage of the capacitor is set to a level of 1/2 to 1/3 or more of the voltage reference value before the start of discharge. It is characterized by

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a dither circuit for generating a dither signal whose signal level changes linearly in correspondence with the cycle of the PWM signal. And a value obtained by adding the current detection signal to the dither signal,
Based on a comparison with the value of the current pattern signal, the PW
The pulse width of the M signal is determined.

According to a fifth aspect of the present invention, in the invention according to any one of the first to third aspects, the instantaneous PWM circuit has upper and lower limits of the value of the current detection signal based on the value of the current pattern signal. PWM so that it falls within the range between values
It has a hysteresis comparator that outputs a signal.

According to a sixth aspect of the present invention, the invention according to any one of the first to fifth aspects further comprises a charge completion detecting means for detecting completion of charging of the capacitor. The discharge of the capacitor is started only when is detected.

The invention according to claim 7 is the invention according to any one of claims 1 to 6, further comprising a current direction switching circuit for switching the direction of the discharge current flowing to the primary side of the transformer, It is characterized in that the current direction is switched every time a start command is input.

According to an eighth aspect of the present invention, in the seventh aspect of the invention, the current direction switching circuit is configured to operate even when the energizing pulse width of the current pattern signal output from the current pattern circuit is a predetermined time or more. The present invention is characterized in that the current direction is switched.

According to a ninth aspect of the invention, in the seventh aspect of the invention, the current direction switching circuit switches the current direction even when saturation of the transformer is detected. , Is characterized.

The invention according to a tenth aspect is the first to ninth aspects.
In any one of the inventions, as a conversion circuit for converting AC power from the AC power supply to DC power, a full bridge circuit formed only by switching elements capable of turn-on and turn-off control based on turn-on and turn-off signals. It has been used.

The invention as defined in claim 11 is the invention as defined in any one of claims 1 to 1.
In the invention described in any one of 0, the predetermined current pattern output by the current pattern circuit includes a plurality of basic current patterns previously incorporated in the current pattern circuit, and a combination of these basic current patterns. And a user setting pattern obtained by combining the basic current pattern and the user setting pattern, and a user setting pattern obtained by combining the user setting patterns with each other. .

[0022]

FIG. 1 is a block diagram showing an embodiment of the present invention.
It will be described with reference to FIGS. However, the same components as those in FIG. 8 are designated by the same reference numerals, and duplicate description will be omitted.

In FIG. 1, the AC power from the AC power supply 1 is rectified by a rectifier circuit 17 formed by a diode bridge.
Is converted into DC power. A diode 18 and an IGBT 19 are connected between the other end side of the reactor 3 and one end side and the other end side of the capacitor 5, and these reactor 3, diode 18, and
The IBGT 19 forms a boost chopper circuit.

The capacitor 5 has an IG in which reverse voltage blocking diodes are respectively inserted between the emitter and the collector.
A switching circuit 20 formed by BTs 20a, 20b, 20c, 20d is connected. The switching circuit 20 functions as a step-down chopper circuit, and allows the current from the capacitor 5 charged to a voltage of a preset level to flow to the primary side of the transformer 7. At this time, the current flowing through the primary side of the transformer 7 is
The current is detected by the current detector 21.

The detection signal of the voltage of the capacitor 5 is sent to the voltage detection circuit 10, and the detection signal of the current flowing through the rectifier circuit 17 is sent to the amplifier 12 by the current detector 9. The voltage reference V _D ^* is adapted to be sent to the amplifier 11, which in turn supplies this voltage reference V _D ^*.
And the deviation from the voltage detection signal from the voltage detection circuit 10 are output to the amplifier 12 as a current reference. The amplifier 12 outputs the deviation between this current reference and the current detection signal from the current detector 9 to the PWM circuit 22. The PWM circuit 22 outputs a PWM signal to the gate of the IGBT 19 so that this deviation becomes zero, and boosts the voltage of the capacitor 5 to the set voltage.

The current pattern circuit 26 outputs a predetermined current pattern signal to the instantaneous PWM circuit 27 when the start command is input. The instantaneous PWM circuit 27 inputs this current pattern signal and the current detection signal from the current detector 21, and outputs a PWM signal so that the values of both may match. The switching circuit 14 alternately selects one of the gate circuits 24 and 25 each time a start command is input, and the instantaneous PWM
The PWM signal from the circuit 27 is sent. For example,
If the gate circuit 24 is selected, the PWM signal from the instantaneous PWM circuit 27 is sent to the gate circuit 24 through the switching circuit 14, and the gate circuit 24 causes the IGBT 20a,
A gate signal is output to the gate of 20d. This allows
A discharge current from the capacitor 5 flows to the primary side of the transformer 7 through the emitters and collectors of the IGBTs 20a and 20d. Then, when the next start command is issued, the PWM signal from the instantaneous PWM circuit 27 is sent to the gate circuit 25 through the switching circuit 14 this time, and the
A gate signal will be sent to T20b and 20c.

The level detection circuit 23 monitors the voltage level of the capacitor 5 after the start of discharge, and stops the operation of the gate circuits 24 and 25 when the voltage level falls below a predetermined value. Further, the dither circuit 28 is
This is a circuit for enabling stable M control, but it is not always necessary.

Next, the operation of FIG. 1 will be described. First, the operation of the configuration when the dither circuit 28 is not provided will be described. Before the start command is output to the current pattern circuit 26 and the switching circuit 14, the voltage detection circuit 11, the amplifiers 11 and 12, the PWM circuit 22, and the step-up chopper circuit (reactor 3, diode 18, IGBT).
It is assumed that the capacitor 5 has been charged to the level of the voltage reference value V _D ^* by the function of the circuit 19).

Here, in this embodiment, when the voltage of the AC power source 1 is 220V AC, the value of V _D ^* is about 700V.
Set to. The level detection circuit 23 stops the operation of the gate circuits 24 and 25 when the voltage of the capacitor 5 becomes 350 V (1/2 of 700 V) or less, and limits the discharge of the capacitor 5. In the present embodiment, the value of the discharge limiting voltage is 350 V as described above, but a preferable range of this value is 350 V to 2
It is 33V (1/3 of 700V). This is because the energy is expressed as (1/2) · C · V ² when the capacitance and voltage of the capacitor are C and V, so when the voltage is discharged to 1/3 of the initial value, Used 8/9 of the stored energy, and the voltage was 1
This is because 3/4 of the stored energy will be used even when discharged to / 2. That is, by setting the discharge limiting voltage as described above, most of the energy stored in the capacitor 5 can be utilized, while the capacitor 5 is prevented from being completely discharged, so that the dielectric is abruptly deteriorated. Can be prevented.
Therefore, as the capacitor 5, it is not necessary to use a capacitor dedicated to charging and discharging, and it is possible to use an ordinary electrolytic capacitor. When the charging voltage and the discharge limiting voltage of the capacitor 5 are set as described above, the instant required to charge the capacitor 5 is 1 to 3 [sec], and the discharging time is several tens of mm [sec]. The charging / discharging time does not affect the workability of spot welding.

When the start command is input to the current pattern circuit 26, the current pattern circuit 26 outputs a predetermined current pattern signal to the instantaneous PWM circuit 27. Instantaneous PWM
The circuit 27 outputs a PWM signal so that the current detection signal matches the current pattern signal. And this P
The IGBTs 20a, 20d (or 20b, 20) by the gate signal of the gate circuit 24 (or 25) based on the WM signal.
c) performs the switching operation, and the discharge current from the capacitor 5 flows through the primary side of the transformer 7.

FIG. 2 shows the voltage V of the capacitor 5 at this time.
₅ is a waveform diagram showing a current pattern signal V ₂₆ of the current pattern circuit 26, a current detection signal I ₂₁ of the current detector 21, and the change of the start command signal. As shown in this figure, the waveform of the current detection signal I ₂₁ is almost the same as the waveform of the current pattern signal V ₂₆ . Therefore, even if the resistance of the welded portion changes during welding, the current detection signal I
₂₁ can be made to follow the current pattern signal, and a stable welding current can be passed. Further, the capacitor voltage V ₅ continues to decrease from time t _{1 to} t ₂ when the start command is output, but since the discharge is stopped when the voltage has dropped to around 350 V, the dielectric of the capacitor 5 suddenly increases. Deterioration is prevented. In the case of FIG. 2, the current pattern is set so that the discharge is stopped when it slightly exceeds 350V. However, when the voltage V ₅ drops to 350V due to a setting error of the current pattern or some abnormality, As described above, the discharging operation of the capacitor 5 is immediately stopped. Then, the next start command is time t
_When issued between _{3 and} t ₄ , the current pattern circuit 26 outputs a similar pattern signal V ₂₆ , but since the switching circuit 14 switches the gate circuits 24 and 25 alternately, A reverse current flows through the primary side, and the signal 21 has a reverse waveform.

Next, the operation of FIG. 1 when the dither circuit 28 is provided will be described with reference to the waveform diagram of FIG. The current detection signal I ₂₁ and the current pattern signal V ₂₆ in FIG. 3 are obtained by enlarging a part of FIG. That is, the signal level and the scale of the time axis are significantly different between FIG. 1 and FIG.

A clock circuit (not shown in FIG. 1) generates the clock signal CL shown in FIG. 3 at a constant cycle, and the instantaneous PWM circuit 27 outputs the PWM signal in synchronization with the clock signal CL. ing. The dither circuit 28 also outputs the dither signal V _DI whose signal level increases linearly in synchronization with the clock signal CL. Instant P
The WM circuit 27 applies the dither signal V to the current detection signal I _21.
Signal with added _DI [I ₂₁ + V _DI ] and current pattern signal V ₂₆
The PWM signal is output so that the larger section of the current pattern signal V ₂₆ is the ON section and the smaller section is the OFF section. For example, at times t _{11 to} t ₁₃ , the waveform of the signal [I ₂₁ + V _DI ] and the waveform of the signal V ₂₆ intersect at time t ₁₂ , so PWM is performed at intervals t _{11 to} t ₁₂ .
Signal is on, PWM signal interval t ₁₂ ~t ₁₃ is turned off.

As described above, the instantaneous PWM circuit 27 can output a stable PWM signal by adding the dither signal V _DI from the dither circuit 28. That is,
As is clear from the illustration of FIG. 3, the width of the increase / decrease in the current detection signal I ₂₁ is very small, so the PWM signal may not be generated based on the comparison between the current detection signal I ₂₁ and the current pattern signal V _26. , The pulse width may deviate from the regular one (especially when noise is mixed). However, by adding the dither signal V _DI as described above, the change in the signal level can be sharpened and a stable PWM signal can be obtained. However, since the current detection signal apparently increases by the amount of the dither signal V _DI added, it is necessary to compensate for this. In order to perform this compensation, the level of the current pattern signal V ₂₆ may be increased by the change e of the dither signal V _DI at time t ₁₂ when the PWM signal changes from on to off. This change e is in the section t _{11 to} t
_Since it changes linearly in ₁₃ , [modulation rate] =
_{(T 11 ~t 12) / (} t 11 ~t 13) can be carried out easily compensated by computing.

The basic embodiment of the present invention is generally as described above, but the present invention also includes the following modes.

(1) The instantaneous PWM circuit 27 shown in FIG. 1 uses the dither signal V _DI to generate a PWM signal, but as shown in FIG. 4, upper and lower limit values based on the current pattern signal are used. A device having a hysteresis comparator that generates a PWM signal so that the current detection signal I ₂₁ falls within the range ΔI may be used. The instantaneous PWM circuit having such a hysteresis comparator has a simple circuit configuration, which is advantageous in terms of cost. However, it has a disadvantage that the switching frequency of the switching circuit 20 becomes indefinite.

(2) The configuration of the charging circuit for the capacitor 5 in FIG. 1 may be configured as shown in FIG. That is, the reactors 51, 52, 53 and the current detector 5
4, 55 are arranged on the alternating current side, and the rectifier circuit 56 detects the current converted into the direct current. Then, instead of the rectifier circuit 17 formed by the diode bridge and the step-up chopper circuit in FIG. 1, a step-up converter using a mixed bridge composed of the diodes 57, 58, 59 and the IGBTs 60, 61, 62 may be used. . Further, regarding the diodes 57, 58 and 59, this is I
If the IGBT and the full bridge configuration of the IGBT are used, control with a power factor of 1 can be performed, which is advantageous for high frequency measures.

(3) In order to improve the efficiency of the welding operation, it is preferable to start the welding device after confirming that the capacitor 5 has been charged. Therefore, an activation interlock can be provided so that the activation start is performed on the condition that the completion of charging is detected. As a method of detecting the completion of charging, the level detection circuit 23 detects that the capacitor voltage is equal to or higher than a set value, or the charging current of the chopper circuit is equal to or lower than the set value. There is a method of detecting by providing a level detector on the output side of 9 or detecting that the current reference (output of the amplifier 11) becomes equal to or less than a set value.

(4) As shown in FIG. 6, when a current pattern signal having a long pulse width is required, the direction of the current I ₂₁ can be switched by interrupting the start command midway. The welding current can be supplied for a longer time without saturating the transformer 7.

(5) A transformer for detecting the primary side voltage V ₇ of the transformer 7 is provided, and the ratio V ₇ / I ₂₁ of the primary side voltage V ₇ and the primary side current I ₂₁ is calculated to transform the voltage. The primary side resistance of the device 7 can be obtained. Then, when this resistance is drastically reduced, it is judged that the transformer 7 is saturated and a circuit for automatically reversing the current direction is added to effectively utilize the iron core of the transformer 7. The size of the transformer 7 can be reduced.

(6) In the current pattern circuit 26, as shown in FIG. 7, basic current patterns V _25a and V _25b made by the welding equipment manufacturer are incorporated. Therefore,
On the user side, it is also possible to generate a user setting pattern (V _25a + V _25b ) by adding these basic current patterns at a setting ratio (FIG. 7 shows the case of a ratio of 1: 1). it can. The combination in this case is
Not only the basic current patterns, but also various combinations such as a combination of the basic current pattern and the user setting pattern and a combination of the user setting patterns can be selected. Therefore, there are derived merits such as being able to deal with different requirements of the user side and utilizing the know-how of welding technology on the user side.

(7) Although the transformer 7 is used in FIG. 1, in a device having a small capacity, the step-down chopper can directly supply a current to the welding electrode 8. Therefore, if the current direction is limited to one direction, the chopper can be configured with one IGBT and one diode, and therefore the circuit configuration can be made extremely simple.

[0043]

As described above, according to the present invention, it is possible to provide a capacitor discharge type resistance welding apparatus which prevents variations in welding quality and is advantageous in terms of cost and space.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a waveform diagram for explaining the operation of FIG.

FIG. 4 is a waveform diagram for explaining an operation of a modified example of the instantaneous PWM circuit in FIG.

5 is a configuration diagram of a modified example of the capacitor charging circuit in FIG.

FIG. 6 is a waveform diagram for explaining another embodiment included in the present invention.

FIG. 7 is a waveform diagram for explaining another embodiment included in the present invention.

FIG. 8 is a configuration diagram of a conventional device.

FIG. 9 is a waveform chart for explaining the operation of FIG.

[Explanation of symbols]

1 AC Power Supply 5 Capacitor 7 Transformer 8 Welding Electrode 14 Switching Circuit 20 Switching Circuit 20a, 20b, 20c, 20d IGBT (Switching Element) 21 Current Detector 23 Level Detection Circuit (Capacitor Voltage Detection Means) 26 Current Pattern Circuit 27 Instantaneous PWM Circuit 28 Dither circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chihiro Oka Chiba, Fuchu-shi, Tokyo No. 1 in Toshiba Fuchu factory (72) Inventor Soma Saburo No. 1, Toshiba-cho, Fuchu-shi, Tokyo Toshiba Co., Ltd. Fuchu Factory

Claims (11)

[Claims] 1. When the AC power from the AC power supply is converted into DC power to charge the capacitor and a start command is input, the discharge current from the capacitor is passed through the switching circuit to the primary side of the transformer. A current pattern circuit for outputting a predetermined current pattern signal based on the input of the start command in a condenser discharge type resistance welding device for supplying a current to a welding electrode connected to the secondary side of a transformer. A current detector for detecting a current flowing through the primary side of the transformer; a current pattern signal from the current pattern circuit; and a PWM based on the input of the current detection signal from the current detector.
An instantaneous PWM circuit for outputting a signal, and performing switching control on the switching circuit based on the PWM signal so that the value of the current detection signal matches the value of the current pattern. Capacitor discharge type resistance welding equipment. 2. The capacitor discharge type resistance welding apparatus according to claim 1, further comprising a capacitor voltage detecting means for detecting the voltage of the capacitor, and when the voltage of the capacitor drops below a set level, the switching circuit The capacitor discharge resistance welding device is characterized in that the current output of is stopped. 3. The capacitor discharge type resistance welding apparatus according to claim 2, wherein the setting level of the voltage of the capacitor is set to a level of 1/2 to 1/3 or more of a voltage reference value before the start of discharge. Capacitor discharge type resistance welding equipment. 4. The capacitor discharge type resistance welding apparatus according to claim 1, wherein the dither signal whose signal level changes linearly is said P
The instantaneous PWM circuit includes a dither circuit that generates a PWM signal corresponding to a cycle of the WM signal, and the instantaneous PWM circuit compares the value obtained by adding the current detection signal to the dither signal with a value of the current pattern signal to generate the PWM signal. A capacitor discharge type resistance welding device characterized by determining the pulse width of a signal. 5. The capacitor discharge type resistance welding apparatus according to claim 1, wherein the instantaneous PWM circuit has upper and lower limit values for the value of the current detection signal based on the value of the current pattern signal. A capacitor discharge type resistance welding device, characterized in that it has a hysteresis comparator that outputs a PWM signal so that it falls within the range. 6. The capacitor discharge type resistance welding apparatus according to claim 1, further comprising a charge completion detecting means for detecting completion of charging of the capacitor, and completion of charging of the capacitor. A capacitor discharge type resistance welding device, characterized in that the discharge of the capacitor is started only when detected. 7. The capacitor discharge resistance welding apparatus according to claim 1, further comprising a current direction switching circuit that switches a direction of a discharge current flowing to the primary side of the transformer, A capacitor discharge type resistance welding device, characterized in that the current direction is switched every time a command is input. 8. The capacitor discharge type resistance welding apparatus according to claim 7, wherein the current direction switching circuit is configured to operate the current pattern switching circuit when the current pulse signal output from the current pattern circuit has a conduction pulse width of a predetermined time or more. A capacitor discharge type resistance welding device characterized in that the direction is switched. 9. The capacitor discharge resistance welding apparatus according to claim 7, wherein the current direction switching circuit switches the current direction even when saturation of the transformer is detected. Capacitor discharge type resistance welding equipment. 10. The capacitor discharge resistance welding apparatus according to claim 1, wherein a turn-on and turn-off based on a turn-on and turn-off signal is used as a conversion circuit for converting AC power from the AC power supply into DC power. A capacitor discharge resistance welding device characterized by using a full-bridge circuit formed only of controllable switching elements. 11. The capacitor discharge type resistance welding apparatus according to claim 1, wherein the predetermined current pattern output by the current pattern circuit includes a plurality of current patterns incorporated in advance in the current pattern circuit. Of the basic current pattern, a user setting pattern obtained by combining these basic current patterns, a user setting pattern obtained by combining the basic current pattern and the user setting pattern, and a combination of the user setting patterns A user-set pattern, and a capacitor discharge resistance welding device characterized by the above.