Welding power supply equipped with disconnection detection of hall current detector

Abstract

To solve the problem of incapability in disconnection of an output line of a Hall current detector due to breaking or connector loosening.SOLUTION: A welding power supply includes: a Hall current detector CT for detecting welding current flowing through the welding power supply; and a control power supply for supplying power supply to the Hall current detector CT. Bias voltage is applied to output of the Hall current detector CT by bias resistance Rb connected to the control power supply, and an output line of the Hall current detector is determined to be disconnected when output voltage of the Hall current detector is a prescribed reference voltage Vr or more while the welding power supply is stopped.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to disconnection detection of a Hall current detector. [Background technology]

[0002] A method is known in which a break in a power supply line to a Hall element is detected by detecting that a current flowing through the Hall element becomes zero (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2009-232261 Summary of the Invention [Problem to be solved by the invention]

[0004] There is an issue that it is not possible to detect disconnection of the output line of the Hall current detector due to a broken wire or a loose connector.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to detect a disconnection of an output line of a Hall current detector. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the invention of claim 1 comprises: a hall current detector for detecting a welding current flowing through a welding power source; a power supply circuit for supplying a control power supply to the Hall current detector; a bias resistor connected to the output of the Hall current detector and to the control power supply; an output line disconnection detection unit that detects a disconnection of an output line of the Hall current detector; Equipped with the output line disconnection detection unit determines that the output line of the Hall current detector is disconnected when an output voltage of the Hall current detector is equal to or higher than a predetermined reference voltage while the welding power source is stopped; The present invention relates to a disconnection detection device.

[0007] The invention of claim 2 is as follows: a switch connected between the bias resistor and the control power supply; Equipped with The switch is closed while the welding power source is stopped, and the switch is opened while the welding power source is energized. 2. The disconnection detection device according to claim 1, Effect of the Invention

[0008] According to the present invention, a break in the output line of the Hall current detector or a disconnection due to a disconnection of a connector can be detected. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram according to a first embodiment of the present invention. [Diagram 2] FIG. 11 is a circuit diagram according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] [First embodiment] 1 is a circuit diagram according to the first embodiment of the present invention, the circuit operation of which will be described below with reference to the diagram.

[0012] The Hall current detector CT detects the welding current flowing through a welding power source (not shown) and outputs a voltage proportional to the welding current to terminal Vo (hereinafter referred to as terminal Vo) of connector CN1 of the Hall current detector CT. The following control power is supplied to terminals Vcc and Vee (hereinafter referred to as terminals Vcc and Vee) of connector CN1 of the Hall current detector CT from connector CN2 of the control printed board PCB via terminal GND (hereinafter referred to as terminal GND) of connector CN1 of the Hall current detector CT. (1) +15V is supplied between terminals Vcc and GND from the control power supply +15V via the light-emitting diode of photocoupler PC1, and a +side control current Ic flows to operate the Hall element HE and operational amplifier OP1. (2) -15V is supplied between terminals Vee and GND from the control power supply -15V via the light-emitting diode of photocoupler PC2, and a negative control current Ie flows for operating the Hall element HE and operational amplifier OP1.

[0013] Resistors R1, R2 and operational amplifier OP1 inside the Hall current detector CT differentially amplify the output signal Vh of the Hall element HE, which is proportional to the welding current flowing through the welding power source, and output a voltage V1 proportional to the welding current. For example, when the welding current is 100 A, it is designed so that the voltage V1 = 1.00 V. Note that an output protection resistor r (about 100 ohms) of the operational amplifier OP1 is connected between the output of the operational amplifier OP1 and terminal Vo of the connector CN1 of the Hall current detector CT (hereinafter referred to as terminal Vo).

[0014] The operational amplifier OP2 and resistors R3 and R4 invert and amplify the voltage V2 at the terminal Vo. For example, when R3 = 10k ohms and R4 = 5k ohms, the voltage is inverted and amplified by 1 / 2.

[0015] A bias resistor Rb (approximately 300k ohms) is connected to pin 2 of connector CN2 on the control printed circuit board PCB (hereafter referred to as pin 2) via the control power supply +15V. When the welding power supply is stopped, that is, when the welding current is 0A, the output V1 of the operational amplifier OP1 inside the Hall current detector CT is also 0V, but because there is an output protection resistor r of the operational amplifier OP1, the voltage V2 of pin 2 is: V2=15V×r / (Rb+r)=15V×100 / (300k+100)=5mV A tiny voltage of is superimposed on the

[0016] If terminal Vo and pin 2 are disconnected due to a broken wire or disconnection of the connector, the voltage V2 at pin 2 will be the following voltage due to bias resistor Rb, even if the welding power source is stopped, i.e., the welding current is 0A. V2=15V×R3 / (Rb+R3)=15V×10k / (300k+10k)=0.48V

[0017] If the voltage V2 at pin 2 exceeds the reference voltage Vr, the comparator CP1 switches the output from low (0V) to high (15V) and sets the output line open circuit signal Sab to high. The reference voltage Vr is set to approximately 0.1V. If there is a disconnection between terminal Vo and pin 2, the value of voltage V2 will be V2 (0.48V) > Vr (0.1V) while the welding power supply is stopped, so the output line open circuit signal Sab will go high and it will be possible to detect that there is a disconnection between terminal Vo and pin 2.

[0018] This section explains how to detect disconnections between each terminal and each pin between the connector CN1 of the Hall current detector CT and the connector CN2 of the control printed circuit board PCB.

[0019] If there is a disconnection between terminal Vcc and pin 1 of connector CN2 on the control printed circuit board PCB (hereinafter referred to as pin 1): Since no control current Ic flows through the Hall current detector CT and no current flows through the light-emitting diode of photocoupler PC1, the light-receiving transistor of photocoupler PC1 turns off and the control line disconnection signal Lab also goes low (0 V), detecting a disconnection.

[0020] If there is a disconnection between terminal Vee and pin 4 of connector CN2 on the control printed circuit board PCB (hereinafter referred to as pin 4): Since no control current Ie flows through the Hall current detector CT and no current flows through the light-emitting diode of photocoupler PC2, the light-receiving transistor of photocoupler PC2 turns off and the control line disconnection signal Lab also becomes low (0 V), detecting a disconnection.

[0021] When there is a disconnection between terminal GND and pin 3 (hereinafter referred to as pin 3) of connector CN2 on the control printed board PCB: Since the control currents Ic and Ie do not flow through the Hall current detector CT and no current flows through the light-emitting diodes of photocouplers PC1 and PC2, the light-receiving transistors of photocouplers PC1 and PC2 are turned off and the control line disconnection signal Lab also becomes low (0 V), detecting a disconnection.

[0022] When there is a disconnection between terminal Vo and pin 2: During the period when the welding power source is stopped and no welding current is flowing, the voltage V2 at pin 2 will be V2 = 0.48 V as described above, and since V2 (0.48 V) > Vr (0.1 V), the output of comparator CP1 will also be High (15 V), the output line disconnection signal Sab will be High, and a disconnection will be detected.

[0023] [Embodiment 2] 2 is a circuit diagram according to the second embodiment of the present invention. Hereinafter, the circuit operation will be described with reference to the diagram, focusing only on the parts that are different from the first embodiment.

[0024] In the first embodiment, bias resistor Rb is always connected to the control power supply +15V and pin 2, so that a bias voltage of 5mV from bias resistor Rb is superimposed on the output voltage V2 of the Hall current detector CT even when current is flowing through the welding power supply. When the welding current flowing through the welding power supply is AC, a signal of 5mV (0.5A) is added to a positive welding current, and a signal of 5mV (0.5A) is subtracted from a negative welding current, resulting in a problem of a difference between positive and negative currents.

[0025] To solve this problem, a switch SW is installed between the control power supply +15V and bias resistor Rb as shown in Figure 2. When the welding power supply is stopped, the switch SW is closed to connect the bias resistor Rb between the control power supply +15V and pin 2, making it possible to detect a disconnection between terminal Vo and pin 2. When the welding power supply is energized, the switch SW is opened to stop the bias voltage superimposition by the bias resistor Rb across pin 2. This makes it possible to prevent a positive and negative current difference that occurs when the welding power supply is energized.

[0026] FIG. 1 and the circuit diagrams shown in the figures for the first and second embodiments are merely examples, and for example, a relay whose contacts are opened and closed mechanically may be used as the switch SW, or a semiconductor switch such as a P-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an analog switch may be used. [Explanation of symbols]

[0027] CN1, 2 connector CP1 Comparator CT Hall current detector HE Hall element Ic, Ie Control current Lab control line disconnection signal OP1, OP2 operational amplifiers PC1, 2 Photocoupler PCB Control Printed Circuit Board R, R1~6 resistance Rb Bias resistor Sab output line disconnection signal SW Switch V1~3 Output voltage Vh output signal Vr Reference voltage

Claims

1. a hall current detector for detecting a welding current flowing through a welding power source; a power supply circuit for supplying a control power supply to the Hall current detector; a bias resistor connected to the output of the Hall current detector and to the control power supply; an output line disconnection detection unit that detects a disconnection of an output line of the Hall current detector; Equipped with the output line disconnection detection unit determines that the output line of the Hall current detector is disconnected when an output voltage of the Hall current detector is equal to or higher than a predetermined reference voltage while the welding power source is stopped; A disconnection detection device characterized by the above.

2. a switch connected between the bias resistor and the control power supply; Equipped with The switch is closed while the welding power source is stopped, and the switch is opened while the welding power source is energized.

2. The disconnection detection device according to claim 1 .

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