阅读说明：本技术 用于gtaw焊接装备的点火装置 (Ignition device for GTAW welding equipment ) 是由 A·梅尼彻 于 2018-05-08 设计创作，主要内容包括：用于焊接装备的点火装置包括电容器、变压器、连接到变压器的次级绕组的高电压输出电路、使得电容器能够放电到变压器的初级绕组的放电开关、充电器以及控制充电器和放电开关的操作控制电路。(An ignition device for a welding apparatus includes a capacitor, a transformer, a high voltage output circuit connected to a secondary winding of the transformer, a discharge switch enabling the capacitor to discharge to a primary winding of the transformer, a charger, and an operation control circuit controlling the charger and the discharge switch.)

1. An ignition device for a welding apparatus, comprising:

a capacitor;

a transformer having a primary winding connected to the capacitor;

a high voltage output circuit including a secondary winding of the transformer;

a switch enabling the capacitor to be discharged through the primary winding of the transformer;

a charger including a pulse width modulation control circuit configured to control charging of the capacitor; and

operating a control circuit that controls the charger to cause periodic charging of the capacitor and also controls the switch to cause periodic discharging of the capacitor and thus the presence of a high voltage at the output of the high voltage output circuit.

2. The ignition apparatus of claim 1, wherein the charger is configured to provide limited instantaneous power and the charger is activated by the operation control circuit for a predetermined amount of time.

3. The ignition apparatus of claim 1, wherein the charger includes a flyback converter having a switch with a reverse blocking capability that prevents a reverse voltage from being applied to a voltage supply that provides voltage to the charger.

4. The ignition device of claim 1, wherein the pulse width modulation circuit includes a voltage feedback circuit that controls a maximum voltage to which the capacitor can be charged.

5. The ignition apparatus of claim 1, wherein the operation control system includes a voltage sensor, and the operation control system is configured to stop charging the capacitor when a voltage sensed by the voltage sensor exceeds a predefined voltage level.

6. The ignition apparatus of claim 1, wherein the switch has reverse conductivity and is controlled by a trigger signal generated by the operation control circuit to cause periodic discharge of the capacitor.

7. The ignition apparatus of claim 1, wherein the operation control system includes a cadence oscillator, and the charger is allowed to operate only when a signal from the cadence oscillator is present.

8. The ignition apparatus of claim 7, wherein the trigger signal applied to the switch is generated by a logical combination of a signal from the cadence oscillator and a one-time signal, or directly from the cadence oscillator signal.

9. The ignition apparatus of claim 1, wherein the operation control system is configured to stop operation of the charger when the external command signal remains activated for longer than a predefined time.

10. A method of operating an ignition device, the ignition device comprising:

a capacitor;

a transformer having a primary winding connected to the capacitor;

a high voltage output circuit including a secondary winding of the transformer;

a switch enabling the capacitor to be discharged through the primary winding of the transformer; and

a charger including a pulse width modulation control circuit configured to control charging of the capacitor, the method comprising:

controlling the charger to cause periodic charging of the capacitor; and

controlling the switch to cause periodic discharge of the capacitor and thus the presence of a high voltage at the output of the high voltage output circuit.

11. The method of claim 10, further comprising controlling the charger to provide limited instantaneous power and activating the charger for a predetermined amount of time.

12. The method of claim 10, further comprising preventing application of a reverse voltage to a voltage supply providing voltage to the charger by providing a switch with reverse blocking capability.

13. The method of claim 10, wherein the pulse width modulation circuit comprises a voltage feedback circuit and controls a maximum voltage to which the capacitor can be charged.

14. The method of claim 10, further comprising sensing a voltage and stopping charging the capacitor when the sensed voltage exceeds a predefined voltage level.

15. The method of claim 10, further comprising controlling the switch with a trigger signal to cause periodic discharge of the capacitor.

16. The method of claim 10, wherein the ignition device comprises a cadence oscillator, and the method further comprises enabling the charger only when a signal from the cadence oscillator is present.

17. The method of claim 16, further comprising generating a trigger signal applied to the switch by logically combining a signal from the cadence oscillator with a one-time signal or directly by a signal from the cadence generator.

18. The method of claim 10, further comprising stopping operation of the charger when an external command signal remains activated for longer than a predefined time.

Technical Field

The present embodiments relate to Gas Tungsten Arc Welding (GTAW) equipment, and more particularly to an arc starting (arc starting) or ignition device.

Background

In a welding apparatus, the power source that provides the arc is the basic component. Depending on the method of electrical welding, the power supply may deliver electrical power of different parameters. The output voltage of any type of welding power supply is limited to a level defined by the requirements of the welding method, safety requirements and the widely understood effectiveness of the equipment. In general, the maximum voltage is too low to cause electrical breakdown from the working electrode to the workpiece at normal operating distances. Thus, the start of welding may occur in a contact manner. In this case, the welding starts from the direct contact of the working electrode and the workpiece. After the power source is activated, when a certain current flows from the power source, the contact is terminated, resulting in a voltage surge and arcing between the electrode and the workpiece. As an alternative to the contact method, welding may be initiated without the electrode and object being in contact. In this alternative case, the welding apparatus comprises an auxiliary device which delivers a sufficiently high voltage for a short time to cause an electrical breakdown between the electrode and the welding object and further to start the arc and welding process.

Disclosure of Invention

In GTAW welding, it is desirable to initiate the arc without contact of the electrode with the workpiece. The ignition device according to embodiments described herein provides high voltage required for ignition of the arc as well as high reliability and safety by controlling voltage, energy and time of operation.

Drawings

Fig. 1 depicts a functional circuit diagram of an ignition device according to an example embodiment.

Fig. 2 depicts a time diagram of several signals in an ignition device according to an example embodiment.

Fig. 3 depicts a time diagram of the voltage across a charging capacitor with increasing time scale according to an example embodiment.

Detailed Description

The embodiments described herein employ a capacitor discharge arc ignition device suitable for contactless arc starting for GTAW welding.

The operation principle of the capacitor discharge arc ignition device is as follows. In a first operation period, the capacitor is charged to a predetermined voltage level by the charger circuit. Once charged, the capacitor is discharged into a high voltage output circuit comprising a series connection of the capacitor, a switch and an air or air gap between the electrodes. In a particular embodiment, the series connection may include a high voltage transformer to obtain the high voltage required for ionizing the atmosphere and generating an arc for welding.

When used in the context of GTAW, and in accordance with embodiments described herein, the ignition device is configured to provide reliable contactless initiation of the process and to provide an improved level of safety for the operator.

In the present embodiment, and at a high level, the ignition device includes a storage capacitor, a charger, a discharge switch, and a high-frequency high-voltage transformer. The charger periodically charges the capacitor. By means of the discharge switch, the capacitor is periodically discharged through the primary winding of the high voltage transformer. The high voltage secondary winding of the transformer then delivers a high voltage to the gap between the electrode and the workpiece. The discharge process proceeds in a resonant manner due to the inductance and capacitance of the circuit. This process is attenuated according to the losses in the gap and in all the elements of the resonant circuit.

According to an example embodiment, the voltage level to which the capacitor is charged is controlled in three ways, thereby providing reliability and safety by keeping the voltage, charge, and discharged energy within acceptable limits.

In an embodiment, the time of "one-time operation" (i.e., the time of operation within the active external control signal) is limited to a particular value, thereby providing reliability and safety by limiting the energy released within one cycle and disabling the permanently generated high voltage in case of a fault that results in a permanently activated external control line or enable signal.

Fig. 1 depicts a functional circuit diagram of an ignition device 100 according to an example embodiment. The figure depicts functional blocks and discrete components.

Fig. 2 depicts a timing diagram of several signals in an ignition device according to an example embodiment. As will be explained in more detail below, the figure shows, among other things, that an unintentional unrestricted start signal (start) is internally limited to a predefined limit (one-time signal). After removal of the initiation signal and subsequent initiation of activation, the next operation may begin. In a particular embodiment, the low frequency or pace oscillator G2 stops operating. However, in another embodiment, oscillator G2 may continue its operation while the charging of the capacitor is disabled in another manner. The trigger pulse (trigger) of the ignition discharge switch is also shown. The last time diagram shows the voltage (V) across the capacitor during a period of operation_C1)。

FIG. 3 depicts a time diagram of the voltage on the charging capacitor with increasing time scale to more clearly illustrate the charging and discharging process and to show the voltage level V_C11And V_C13. Voltage level V_C12Not shown in the figure. Expectation of V_C12Greater than V_C11And is less than V_C13This is not a mandatory condition, however.

Referring to fig. 1, in the ignition device 100, a charger 110 configured as a flyback converter charges a capacitor C1. The charger 110 includes a coupled inductor T1 having a primary winding of an inductance L1 and a secondary winding of an inductance L2, a switch S1 in the form of a series connection of a MOSFET transistor V1 and a diode V2 with reverse blocking capability, a secondary rectifier V3, and a Pulse Width Modulation (PWM) control circuit N1120 operating on the principle of Peak Current Mode (PCM).

PMW control circuit N1120 may be an integrated control circuit and includes generating a high frequency f_oscShort pulse oscillator G1, powerA voltage feedback amplifier a1 and a maximum current limiter in the form of a resistor R1 and a zener diode V6. The PMW control circuit N1120 further includes a peak current comparator a2, a PWM latch D1, and an output logic element (and gate) D2. The PMW control circuit N1120 may further include a T-flip-flop D3 that will operate at a frequency (f)_osc) Divided by, for example, two, limiting the maximum duty cycle to 50%. PMW control circuit N1120 includes a control inputWhich starts and stops operation. Although not shown in the figure, in other aspects, operation may be stopped by, for example, stopping oscillator G1, such that MOSFET V1 is prevented from conducting, and such that current does not flow through the primary winding of T1.

The charger is powered by an external dc low voltage power source VDC.

The ignition device 100 of the present embodiment further includes an operation control circuit 140, and the operation control circuit 140 includes a low-frequency oscillator G2 (see fig. 2 and 3) having a predefined frequency and generating pulses of a predefined width ton.

The signal from the low frequency oscillator G2 passes through the control inputIs applied to AND (AND) logic gate D5 so that the charger 110 is only able to operate during the activation pulse for ton time. Thus, the charger 110 operates during ton time. On the falling slope of the ton pulse, a trigger pulse is generated by a monostable trigger D6. Thus, switch S2, which is presented as a reverse conduction of thyristor V4 with diode V5, is activated, closing the series connected circuit of primary winding z1 and capacitor C1 of high voltage transformer T2. Reverse conduction through V5 is required due to the resonant nature of the discharge. The output winding z2 of the transformer T2 is connected to the air gap, i.e., the high voltage output terminal (HV output terminal) of the high voltage output circuit 130. The high voltage output circuit 130 may include a clamp circuit F1. Once switch S2 (thyristor V4) is activated, a high voltage appears at the air gap, ionizing the space between the electrodes, creating an enabling low voltageThe conductive path of the GTWA arc. The GTWA welding power supply interconnection to ignition device 100 is not depicted in fig. 1 as it is not relevant to the present embodiment.

The charger 110 and the PMW control circuit 120 operate in discontinuous current mode operation (DCM) based on the principle of a flyback converter. Each pulse from oscillator G1 sets PWM latch D1. On the falling slope of the pulse from the oscillator, the control output OUT activates switch S1 by applying the appropriate voltage to the gate of V1. Therefore, the current in the primary winding L1 increases from zero. The current is sensed using resistor R2 and the current sense signal CS is delivered to the PWM control circuit comparator a 2. Once the current reaches a value equal to the voltage on the + input of comparator a2 divided by the value of resistor R2, the PWM control circuit latch D1 resets, turning off the output signal OUT. The voltage across windings L1, L2 reverses and current in the coupled inductor T1 begins to flow through diode V5, charging capacitor C1. This cycle is repeated on each pulse of the G1 oscillator.

Initially, the current in winding L1 increases to some maximum value defined by the resistance of the reference voltage Vz from the V6 reference diode and R2. When the voltage of the capacitor C1 reaches V_C11At level (fig. 2), the voltage feedback amplifier a1 begins to decrease the current reference. Thus, the voltage feedback loop is closed and the charger maintains the voltage on capacitor C1 at level V_C11. In this way, the voltage across the capacitor is regulated in a first manner.

Due to V_C1The importance of the voltage level, a second, separate overvoltage protection is thus achieved. In particular, once voltage V is reached_C12Comparator a3 resets flip-flop D7. The flip-flop D7 resets whenever there is no pulse from the cadence oscillator G2. Therefore, even in the case where the voltage feedback loop including the voltage feedback amplifier a1 does not operate, the voltage across the capacitor C1 cannot be greater than V_C12。

The maximum voltage across the capacitor C1 is limited to a level V in a third way_C13. Since the peak current in the primary winding L1 of the coupled inductor T1 is limited to a value Vz/R2 and when chargingThe time is limited to ton and therefore the maximum voltage across capacitor C1 is limited to the following value:

if the PWM control circuit N1120 includes a T-flip-flop D3, then

Thus, according to embodiments described herein, there is provided an ignition device comprising a charger, a pulse width modulation control circuit configured to control charging of a capacitor of the charger, a high voltage output circuit electrically connected to the capacitor and comprising a switch enabling the capacitor to be discharged, and an operation control circuit controlling the switch such that a high voltage is present at an output of the high voltage output circuit.

The embodiments described herein provide several unique features including a charger employing a flyback converter with a switch with reverse blocking capability, triple control of the charging voltage, and limited ignition operating time.

More specifically, due to the diode V2, the storage capacitor C1 is charged from the flyback converter having the switch S1 with reverse blocking capability. The diode V2 protects the converter and the voltage power source VDC from reverse voltages occurring during resonance of the storage capacitor C1 and the external inductance and capacitance.

The maximum voltage across the reservoir capacitor C1 is limited in three ways. First, the flyback converter has an accurately defined instantaneous power and an accurately defined operating time. The capacitor has an accurate capacitance. In this way, a part of the energy and thus the voltage of the maximum capacitor is well defined. Second, the flyback converter includes a voltage feedback loop via a1, so the voltage of the capacitor is well defined. Third, when the voltage of the capacitor is too high, the operation of the flyback converter is disabled via the standby voltage feedback loop of A3 with latch D7.

Finally, the one-time operation of the unit is internally limited. When the start signal is present at the input of timer D4, its output (one-time signal) is activated, but only for a time no longer than a predefined or predetermined time. In addition, in the absence of the enable signal, the output of timer D4 is not active. The one-time signal enables the operation of the cell by means of the gate D5. In this way, the equipment is protected from general faults in which the unit is driven by a permanent activation signal that is inadvertently applied. Furthermore, due to this time limitation, the total energy and total charge delivered by the cell during one welding cycle is limited.

The above description is intended to be exemplary only. Various modifications and structural changes may be made therein without departing from the scope of the concepts described herein and within the scope and range of equivalents of the claims.