Multi-mode external characteristic control circuit

Abstract

The utility model discloses a multi-mode external characteristic control circuit, which is used for controlling PWM (Pulse Width Modulation) signal modulation of a whole machine and comprises a mode conversion unit used for outputting different gear signals; the current detection unit is used for outputting different judgment signals according to different gear signals; the voltage regulation and control unit is used for outputting a voltage regulation and control signal according to the gear signal and the judgment signal; the low-load voltage control unit is used for outputting a voltage control signal according to the gear signal and the judgment signal; and the PWM control unit is used for outputting a whole machine PWM modulation signal according to the voltage control signal and the voltage regulation and control signal. According to the utility model, the welding power supply can obtain a safety mode or an arc starting and arc extinguishing mode in different no-load and load voltage states and different welding effects.

Description

Technical Field

[0001] The utility model relates to a multi-mode external characteristic control circuit, in particular to a multi-mode external characteristic control circuit of a welding machine output voltage. Background Art

[0002] Welding machine refers to an electrical appliance that provides a power supply with certain characteristics for welding. Welding is widely used in various industrial fields, such as aerospace, shipbuilding, automobiles, containers, etc., because of its advantages of flexibility, simplicity, convenience, firmness and reliability, and even the same strength as the parent material after welding. Welding external characteristics refer to the static relationship curve between the output voltage and output current of the welding power supply in a stable state, which is usually expressed in the form of a curve on the coordinates with voltage as the vertical axis and current as the horizontal axis. This relationship curve reflects the working condition and performance of the power supply, and can be divided into three types: steep drop external characteristics, flat hard external characteristics and rising external characteristics. The steep drop external characteristic refers to the characteristic that the terminal voltage decreases significantly when the output current increases. This characteristic helps to quickly reduce the resistance between the workpieces during the welding process and promote melting welding. The flat hard external characteristic keeps the voltage stable and is suitable for welding processes that require uniform heat input. The rising external characteristic is that the voltage increases with the increase of current. This characteristic is rare and is usually used for special welding needs.

[0003] Therefore, different working environments, different application scenarios and different materials will have some different requirements for welding external characteristic modes. For conventional high-current thick plate connection welding machine applications, the welding output no-load voltage is required to be high and the arc can be extinguished freely. For closed containers and humid and easy-to-electric-shock environments, a low-voltage arc starting and low no-load safety voltage anti-electric shock design is adopted. For heat-sensitive materials such as high-carbon steel and cast iron welding, smooth arc starting, short arc operation, and low-voltage arc extinguishing are required. The adjustable arc starting and arc extinguishing voltage mode between high no-load and low no-load is more suitable for arc extinguishing operations.

[0004] Chinese patent document CN108390123B discloses a method and apparatus for a multi-mode welding power supply, comprising: a welding power supply connected to a multi-mode power output circuit; a controller for receiving input from the welding power supply and outputting a control signal to the multi-mode power output circuit. The controller is configured to identify whether the load at the multi-mode power output corresponds to a welding mode or a battery charging mode. The controller is also configured to control the multi-mode power output circuit to adjust the power from the welding power supply based on one of the identified welding mode or battery charging mode. Although this prior art can provide a multi-mode power output, it is necessary to use a controller to first perform the operating mode corresponding to the load at the multi-mode power output, and then control the output circuit according to the current-voltage curve in different operating modes, which requires a complex configuration of the controller, increasing the circuit cost. Utility Model Content

[0005] The present utility model aims to solve the technical problems of complex controller configuration and high circuit cost in the prior art, and provides a multi-modal external characteristic control circuit for controlling the PWM signal modulation of the whole machine, wherein: it includes a mode conversion unit for outputting different gear signals;

[0006] a current detection unit for outputting different determination signals according to different gear signals;

[0007] a voltage regulation unit for outputting a voltage regulation signal according to the gear signal and the determination signal;

[0008] a low no-load voltage control unit for outputting a voltage control signal according to the gear signal and the determination signal;

[0009] a PWM control unit for outputting a modulation signal of the whole machine PWM according to the voltage control signal and the voltage regulation signal.

[0010] Preferably, the mode conversion unit includes a single-pole multi-throw switch and multiple signal control diodes. The multiple signal control diodes form different circuits of the single-pole multi-throw switch, and the +15V power supply is switched to different circuits through the single-pole multi-throw switch to output different gear signals.

[0011] Preferably, the single-pole multi-throw switch is a single-pole four-throw switch. The mode conversion unit includes five signal control diodes. The output gear signals include four gears, corresponding to four no-load and load voltage modes, namely free high no-load voltage, high no-load arc starting and high voltage arc extinguishing modes; low no-load voltage, low voltage arc starting and low voltage arc extinguishing modes; constant voltage no-load, the load voltage changes with the load but does not exceed the set controlled voltage mode; high no-load, the load voltage changes with the load and does not exceed the controlled voltage, and the arc extinguishing is controlled.

[0012] Preferably, the current detection unit includes a resistor, a signal control diode, a triode and an FB pin. When the system provides current, Ifb is 0, and when the system does not provide current, Ifb is at a high potential.

[0013] Preferably, the voltage regulation unit includes a resistor, a capacitor, a voltage stabilizing diode, a diode and a triode, as well as the welding power supply output +. The voltage regulation unit outputs a voltage regulation signal according to the gear signal and the determination signal.

[0014] Preferably, the low no-load voltage control unit includes a resistor, a capacitor, a diode, a triode, and the output + of the welding power supply. The +15V power supply is applied to the welding power supply +. Before arc ignition, the PWM control unit outputs a turn-off signal. When short-circuit arc ignition occurs, the PWM control unit has no output signal, the welding power supply outputs current, the determination signal output by the current detection unit becomes low, the PWM control unit is self-locked, and enters the normal arc-burning state. The normal arc-burning voltage is higher than 15VDC, and the +15V power supply is reversely isolated by the diode.

[0015] Preferably, the PWM control unit includes two diodes. The voltage regulation signal output by the voltage regulation unit controls the modulation signal after passing through one of the diodes, and the output is high-level effective. The voltage control signal output by the low no-load control unit controls the modulation signal after passing through the other diode, and the output is high-level effective.

[0016] The utility model has the following beneficial effects:

[0017] In the utility model, the current detection unit determines no-load or load according to the presence or absence of current, and outputs different determination signals according to the two states of the presence or absence of current. Then, according to the agreed relationship between the welding voltage and the welding current and the state of the presence or absence of current, a PWM modulation signal is obtained, so as to realize the regulation of the welding voltage, and thus realize the control of the no-load or load voltage output, so that the welding power supply can obtain safe modes or arc ignition and arc extinguishing modes under different no-load and load voltage states and different welding effects. Compared with the prior art, there is no need for complex controller configuration, the circuit is simpler, and the circuit cost can be reduced. Description of the Drawings

[0018] Figure 1 is the circuit diagram of an embodiment of a multi-modal external characteristic control circuit of the utility model;

[0019] Figure 2 is the external characteristic diagram of the voltage output corresponding to gear I;

[0020] Figure 3 is the external characteristic diagram of the voltage output corresponding to gear II;

[0021] Figure 4 is the external characteristic diagram of the voltage output corresponding to gear III;

[0022] Figure 5 is the external characteristic diagram of the voltage output corresponding to gear IV. Detailed Embodiment

[0023] The following is a further detailed description through specific embodiments:

[0024] 1. Definition

[0025] No-load: refers to the situation without load.

[0026] No-load voltage: It refers to the open-circuit voltage at the output terminal of the power supply when no load is connected.

[0027] Arc starting: In shielded metal arc welding, it is the process of igniting the welding arc with the electrode.

[0028] Arc extinguishing: It refers to the process of the arc going out after welding stops.

[0029] Arc ignition: In welding, it is the process of igniting the welding arc with welding materials (such as electrodes, welding wires, etc.).

[0030] Diode reverse isolation: When the diode is in the reverse bias state, a very high resistance is formed. At this time, if the signal voltage at the input terminal is smaller than the positive power supply voltage, the diode will be in the cut-off state and will not transmit the signal, playing an isolation role; if the signal voltage at the input terminal is larger than the positive power supply voltage, the diode will be in the breakdown state and conduct current, playing a role in normal signal transmission.

[0031] PWM modulation: Pulse width modulation, which is an analog control method. According to the change of the corresponding load, the bias of the transistor base or MOSFET gate is modulated to change the conduction time of the transistor or MOSFET, so as to change the output of the switching regulated power supply.

[0032] 2. Description of the drawings: Figures 2 - 5 In the figure, 0 - t1: no load; t1 - t2: short-circuit arc starting; t2 - t3: load; t3 - t4: arc extinguishing; after t4: no load.

[0033] The embodiment is basically as shown in the attached Figure 1 As shown: A multi-modal external characteristic control circuit is used to control the PWM signal modulation of the whole machine. Among them: It includes a mode conversion unit for outputting different gear signals;

[0034] A current detection unit for outputting different determination signals according to different gear signals;

[0035] A voltage regulation unit for outputting a voltage regulation signal according to the gear signal and the determination signal;

[0036] A low no-load voltage control unit for outputting a voltage control signal according to the gear signal and the determination signal;

[0037] A PWM control unit for outputting the modulation signal of the whole machine PWM according to the voltage control signal and the voltage regulation signal.

[0038] Among them, the mode conversion unit includes a single-pole multi-throw switch and multiple signal control diodes. The multiple signal control diodes form different circuits of the single-pole multi-throw switch. The +15V power supply is switched to different circuits through the single-pole multi-throw switch to output different gear signals. Specifically, the mode conversion unit includes a single-pole four-throw switch SW0 and five signal diodes D1, D2, D3, D4, and D5. The single-pole four-throw switch SW0 has four gears: Gear I: Free high no-load voltage, high no-load arc starting, and high voltage arc extinguishing. Suitable for continuous large current thick plate welding; Gear II: Low no-load voltage, low voltage arc starting, and low voltage arc extinguishing. Suitable for safe operation in a humid and airtight container; Gear III: Constant voltage no-load, the load voltage changes with the load but does not exceed the set controlled voltage. Suitable for arc extinguishing and intermittent arc welding; Gear IV: High no-load, the load voltage changes with the load and does not exceed the controlled voltage, and the arc extinguishing is controlled. Suitable for heat-sensitive welding materials, high arc starting success rate, short arc operation, and low voltage arc extinguishing.

[0039] The current detection unit includes resistors R6, R7, R8, signal control diode D9, transistor T3, and an FB pin. When there is current provided by the system, Ifb is 0. When there is no current provided by the system, Ifb is at a high potential.

[0040] The voltage regulation unit includes resistors R1, R2, R3, R4, R5, capacitor C1, zener diode ZD1, diode D10, transistors T1 and T2, and the welding power supply output +P+.

[0041] The low no-load voltage control unit includes resistors R9, R10, R11, R12, R13, R14, R16, capacitor C2, diodes D6, D7, transistors T4, T5, and the welding power supply output +P+. The +15V power supply is applied to the welding power supply +. Before arc starting, the PWM control unit outputs a turn-off signal, and the main circuit of the welding machine does not work. The voltage across the positive and negative terminals of the welding power supply is lower than 15Vdc. For short-circuit arc starting, the PWM control unit has no output signal, the main circuit works, the welding power supply outputs current, the determination signal output by the current detection unit becomes low, the PWM control unit is self-locked, and enters the normal arc burning state. The normal arc burning voltage is higher than 15VDC, and +15V is reverse-isolated by diode D6.

[0042] The PWM control unit includes two diodes D8 and D11. The voltage regulation signal output by the voltage regulation unit controls the modulation signal through diode D11, and the output is high-level effective; the voltage control signal output by the low no-load control unit controls the modulation signal through diode D8, and the output is high-level effective.

[0043] The specific implementation process is as follows:

[0044] (1) The single-pole multi-throw switch is placed in Gear I: Free high no-load voltage, high no-load arc starting, and high voltage arc extinguishing, and the load voltage is not specially controlled.

[0045] The single-pole multi-throw switch is placed in position I, the diodes D1 and D2 are energized, and points A and B are energized. The potential of point A is +(15 - 0.7) VDC, the triode T2 is saturated and conducting, the positive electrode of the diode D11 is at a low potential, and at this time the PWM control unit has no output. The potential of point B is +(15 - 0.7) Vdc, the triode T3 is saturated and conducting the diode, the positive electrode of D8 is at a low potential, and the PWM control unit has no output.

[0046] The voltage output external characteristic corresponding to gear I is as Figure 2 shown.

[0047] (2) The single-pole multi-throw switch is placed in gear II: low no-load voltage, low-voltage arc ignition and low-voltage arc extinction.

[0048] The single-pole multi-throw switch is placed in position II, the diode D3 is energized, the voltage of point A is (15 - 0.7) VDC, the triode T2 is saturated and conducting, the positive electrode of the diode D11 is clamped at 0 potential, and the function of the voltage regulation unit is shielded.

[0049] Working process of the low no-load voltage control unit:

[0050] During the no-load stage, Ifb outputs a high potential. +15V is divided by the resistors R9, D6, R10, R11, and R12, and a power supply lower than 15V is obtained at the output +P+ of the welding power supply. At the same time, the driving triode T4 is saturated and conducting, the positive electrode of the diode D7 is clamped at 0 potential, and the triode T5 is cut off. The positive electrode potential of the diode D8 is derived from the voltage division of Ifb through the resistors R6, R16, diode D8, and the subsequent PWM control resistors. The PWM control unit outputs a high potential, the modulation signal is locked, the inverter main circuit has no output, and the voltage at the output +P+ of the welding power supply is lower than 15VDC. During no-load, the welding power supply is in a low no-load voltage state.

[0051] During the short-circuit arc ignition stage, the output +P+ of the welding power supply is short-circuited to the ground, the triode T4 is cut off, the triode T5 is saturated and conducting, the positive electrode of the diode D8 is clamped at 0 potential, the PWM control unit has no output, the main circuit normally outputs the welding current, Ifb outputs a low potential, and the PWM control unit is interlocked and clamped at a low level to ensure the stable and normal output of the main circuit.

[0052] During the arc-extinguishing stage, the arc is broken by pulling. During the pulling process, the current always exists and the main circuit keeps outputting. When the arc voltage gradually approaches the no-load voltage of the welding power source, it will be naturally broken. When the welding current is 0, it instantly returns to the high no-load voltage, Ifb becomes higher, the output +P+ of the welding power source becomes higher, the triode T4 is saturated and conducts, and the CE pole of the triode T5 is cut off. The high potential of Ifb acts on the PWM control unit through the resistors R6, R16, and the diode D8. The PWM control unit outputs a high potential, the modulation signal is locked, and there is no output from the main inverter circuit. After maintaining the high no-load voltage for a short time, it returns to the 0 potential. The output +P+ of the welding power source is maintained at a high potential by the voltage provided by the +15V through the resistor R9 and the diode D6 circuit, maintaining the saturation conduction of the triode T4, the cut-off of the triode T5, and the high potential output of the PWM control unit. When the output +P+ voltage of the welding power source is lower than 15VDC, the welding output terminal returns to the low no-load state. The voltage output external characteristic corresponding to gear II is as Figure 3 shown.

[0053] (3) The single-pole multi-throw switch is set to gear III: constant voltage no-load, and the load voltage changes with the load but does not exceed the set controlled voltage.

[0054] When the single-pole multi-throw switch is placed in gear III, the diode D4 is energized, the potential at point B is (15 - 0.7) VDC, the CE pole of the triode T3 is saturated and conducts, the positive potential of the diode D8 is clamped to 0, the low no-load voltage control unit is shielded, and the positive potential of the diode D9 is clamped to 0.

[0055] No-load stage: The no-load voltage is controlled. The welding power supply outputs a high no-load voltage at +P+. This voltage is divided and filtered by resistors R1, R2, and capacitor C1. The voltage at the terminals of capacitor C1 gradually increases. When the voltage Uc1 of capacitor C1 is lower than the breakdown voltage of the voltage regulator diode ZD1, the collector-emitter (CE) of transistor T1 is cut off, and the CE of transistor T2 is saturated and conducting. The positive terminal of diode D11 is clamped at 0 potential. The PWM control unit has no output, and the modulation signal is normally output. The main inverter circuit operates normally, and the welding power supply outputs a high no-load voltage at +P+ continuously. When the voltage Uc1 of capacitor C1 is higher than the breakdown voltage of the voltage regulator diode ZD1, the CE of transistor T1 is saturated, and the CE of transistor T2 is cut off. +15V acts on the PWM control unit through resistor R5 and diode D11. The PWM control unit outputs at a high level, the modulation signal is locked, and the main circuit stops working. The welding power supply outputs a no-load voltage of 0 at +P+. The voltage across capacitor C1 gradually decreases. After a period of time, the voltage Uc1 of capacitor C1 is lower than the breakdown voltage of the voltage regulator diode ZD1. The voltage regulator diode ZD1 is cut off, the CE of transistor T1 is cut off, the CE of transistor T2 is saturated and conducting, the positive terminal of diode D11 is clamped at 0 potential, the PWM control unit has no output, the adjustment signal is normally output, the main inverter circuit operates normally, and the welding power supply outputs a high no-load voltage at +P+ again. This process repeats. The welding power supply outputs a square wave at +P+ with alternating high and low voltages. The higher the voltage regulator diode ZD1, the larger the PWM duty cycle, and the higher the average voltage output at +P+ of the welding power supply. The welding power supply outputs a constant output that is proportional to the breakdown voltage of the voltage regulator diode ZD1. By adjusting the voltage regulator diode ZD1, the size of the no-load average voltage output at +P+ of the welding power supply can be adjusted.

[0056] Load stage. The main circuit operates, and arc striking is relatively easy. After entering normal welding, the welding arc voltage is generally lower than the average value of the output at +P+ of the welding power supply. When the arc voltage is artificially raised to the point where it can break down the voltage regulator diode ZD1, the arc voltage is instantaneously controlled and output, forcing the arc voltage to automatically return to the range of the controlled voltage value. In terms of the welding feel, it is manifested as the arc being elongated, the current becoming smaller, and eventually the arc going out, reminding the welding operator to perform short-arc operation to ensure welding quality.

[0057] Arc extinguishing stage. The arc is elongated, the current becomes smaller, then elongated again, and the arc goes out at the controlled voltage point. There will be no situation where the arc is stretched very long and is not easy to go out, which is beneficial for arc-breaking welding and arc-extinguishing welding operations. The voltage output external characteristic corresponding to gear III is as Figure 4 shown.

[0058] (4) The single-pole multi-throw switch is placed in gear IV: High no-load, the load voltage changes with the load and does not exceed the controlled voltage, and the arc extinguishing is controlled.

[0059] The single-pole multi-throw changeover switch is placed in gear position Ⅳ, diode D5 is powered on, the collector-emitter of triode T5 is saturated and conducting, and the positive electrode of diode D8 is clamped to 0. The low no-load voltage control unit is shielded.

[0060] During the no-load stage, Ifb is at a high potential. Ifb acts on the base of triode T2 through resistor R6, diode D9, and resistor R4. The collector-emitter of triode T2 is saturated and conducting, and the positive electrode of diode D11 is clamped at 0. The PWM control unit has no output, the adjustment signal is normal, and the main circuit operates normally. The welding has a high no-load output and is easy to strike an arc.

[0061] During the load stage, Ifb is at 0 potential, the positive electrode of diode D9 is clamped to 0, triode T2 is controlled by triode T1, and triode T1 is controlled by the breakdown state of the welding power supply output +P+ zener diode ZD1. During normal welding, the arc voltage is lower than the controlled voltage value (proportional to the breakdown voltage of zener diode ZD1) set by the welding power supply output +P+. Zener diode ZD1 is cut off, the collector-emitter of triode T1 is cut off, the collector-emitter of triode T2 is saturated and conducting, the positive electrode of diode D8 is clamped at 0, the PWM control unit has no output, the modulation signal output is normal, and the main circuit operates normally. When the arc is stretched and raised, the arc voltage becomes higher, the welding power supply output +P+ is higher than a certain value, zener diode ZD1 breaks down, the collector-emitter of triode T1 conducts, triode T2 is cut off, +15V acts on the PWM control unit through resistor R5 and diode D8, the PWM control unit outputs a high potential, the modulation signal is locked, the main circuit shuts down and has no output, and the welding power supply output +P+ is limited within the controlled voltage related to the breakdown voltage of zener diode ZD1. During the welding process, when the arc is stretched, the current becomes smaller until the arc breaks. The arc is suitable for short-arc operation to ensure welding quality.

[0062] During the arc-extinguishing stage, the arc is stretched, the current becomes smaller, then stretched again, and the arc breaks at the controlled voltage point. After the arc breaks, Ifb becomes higher, the collector-emitter of triode T2 is saturated and conducting, the positive electrode of diode D8 is clamped at 0 potential, the PWM control unit has no output, the main circuit output is normal, and the no-load voltage returns to the high no-load state, facilitating the next arc striking. High-voltage arc striking, short-arc welding, and short-arc arc extinguishing are achieved. The voltage output external characteristic corresponding to gear position Ⅳ is as Figure 5 shown.

[0063] The above are only the embodiments of the present utility model. Common knowledge such as the specific structures and characteristics known in the art is not described in detail herein. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the utility model belongs before the filing date or the priority date, can learn all the existing technologies in this field, and have the ability to apply the conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, improve and implement this solution in combination with their own abilities. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present utility model, several deformations and improvements can still be made, and these should also be regarded as the protection scope of the present utility model, and these will not affect the implementation effect of the present utility model and the practicality of the patent. The protection scope claimed in this application should be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A multi-modal external characteristic control circuit for controlling the PWM signal modulation of the whole machine, characterized in that: It includes a mode conversion unit for outputting different gear signals; a current detection unit for outputting different determination signals according to different gear signals; a voltage regulation unit for outputting a voltage regulation signal according to the gear signal and the determination signal; a low no-load voltage control unit for outputting a voltage control signal according to the gear signal and the determination signal; a PWM control unit for outputting a modulation signal of the whole machine PWM according to the voltage control signal and the voltage regulation signal.

2. The multimodal external characteristic control circuit according to claim 1, wherein: The mode conversion unit includes a single-pole multi-throw switch and a plurality of signal control diodes. The plurality of signal control diodes form different circuits of the single-pole multi-throw switch, and the +15V power supply is switched to different circuits through the single-pole multi-throw switch to output different gear signals.

3. The multimodal external characteristic control circuit according to claim 2, characterized in that: The single-pole multi-throw switch is a single-pole four-throw switch. The mode conversion unit includes five signal control diodes. The output gear signals include four gears, corresponding to four no-load and load voltage modes, namely free high no-load voltage, high no-load arc starting and high voltage arc extinguishing modes; low no-load voltage, low voltage arc starting and low voltage arc extinguishing modes; constant voltage no-load, the load voltage changes with the load but does not exceed the set controlled voltage mode; high no-load, the load voltage changes with the load and does not exceed the controlled voltage, and the arc extinguishing is controlled.

4. The multimodal external characteristic control circuit according to any one of claims 1-3, characterized in that: The current detection unit includes a resistor, a signal control diode, a triode and an FB pin. When there is current provided by the system, Ifb is 0. When there is no current provided by the system, Ifb is at a high potential.

5. The multimodal external characteristic control circuit according to claim 4, characterized in that: The voltage regulation unit includes a resistor, a capacitor, a voltage stabilizing diode, a diode and a triode, and the welding power supply output +. The voltage regulation unit outputs a voltage regulation signal according to the gear signal and the determination signal.

6. The multimodal external characteristic control circuit according to claim 5, characterized in that: The low no-load voltage control unit includes a resistor, a capacitor, a diode and a triode, and the welding power supply output +. The +15V power supply is applied to the welding power +. Before arcing, the PWM control unit outputs a turn-off signal; when short-circuit arcing occurs, the PWM control unit has no output signal, the welding power supply outputs current, the determination signal output by the current detection unit becomes low, and the PWM control unit is self-locked and enters the normal arcing state. The normal arcing voltage is higher than 15VDC, and the +15V power supply is reversely isolated by the diode.

7. The multimodal external characteristic control circuit according to claim 6, characterized in that: The PWM control unit includes two diodes. The voltage regulation signal output by the voltage regulation unit controls the modulation signal after passing through one of the diodes, and the output is high-level effective. The voltage control signal output by the low no-load control unit controls the modulation signal after passing through the other diode, and the output is high-level effective.

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