Welding power supply with open circuit detection of Hall current detector

Abstract

The invention provides a welding power supply with open circuit detection of a Hall current detector. There is a problem that disconnection of an output line of a Hall current detector caused by disconnection of a line or disconnection of a connector cannot be detected. A Hall current detector (CT) detects a welding current flowing in a welding power source, a control power source supplies power to the Hall current detector (CT), and a bias resistor (Rb) connected to the control power source applies a bias voltage to the output of the Hall current detector (CT). When the output voltage of the Hall current detector is greater than a given reference voltage (Vr) during the stop of the welding power supply, it is determined that the output line of the Hall current detector is open.

Description

Technical Field

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

[0002] There is known a method of detecting disconnection of a power supply line to a Hall element based on the current flowing in the Hall element becoming zero (for example, Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-232261 Summary of the invention

[0006] -Problems to be solved by the invention-

[0007] There is a problem that the output line of the Hall current detector cannot be detected to be disconnected due to disconnection of the line or disconnection of the connector.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to detect disconnection of an output line of a Hall current detector.

[0009] -Methods for solving the problem-

[0010] In order to solve the above-mentioned problems, the invention of technical solution 1 is a circuit break detection device, characterized in that it comprises: a Hall current detector for detecting a welding current flowing in a welding power supply; 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 the control power supply; and an output line circuit break detection unit for detecting a circuit break of the output line of the Hall current detector, wherein the output line circuit break detection unit determines that the output line of the Hall current detector is broken when the output voltage of the Hall current detector is above a given reference voltage when the welding power supply is stopped.

[0011] The circuit break detection device of the invention of technical solution 2 is based on the circuit break detection device of the invention of technical solution 2, and is characterized in that it has a switch connected between the bias resistor and the control power supply, and the switch is closed when the welding power supply is stopped, and the switch is opened when the welding power supply is energized.

[0012] -Effects of the Invention-

[0013] According to the present invention, it is possible to detect a disconnection caused by a disconnection of an output line of a Hall current detector or a disconnection of a connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1This is a circuit diagram according to Embodiment 1 of the present invention.

[0015] Figure 2 This is a circuit diagram according to Embodiment 2 of the present invention.

[0016] -Description of Reference Numerals-

[0017] CN1, 2: Connector

[0018] CP1: Comparator

[0019] CT: Hall current detector

[0020] HE: Hall element

[0021] Ic, Ie: control current

[0022] Lab: Control line break signal

[0023] OP1, 2: Operational amplifier

[0024] PC1, 2: Photocoupler

[0025] PCB: control printed circuit board

[0026] R, R1~6: resistance

[0027] Rb: Bias resistor

[0028] Sab: Output line disconnection signal

[0029] SW: Switch

[0030] V1~3: output voltage

[0031] Vh: output signal

[0032] Vr: reference voltage. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0034] [Implementation method 1]

[0035] Figure 1 1 is a circuit diagram according to Embodiment 1 of the present invention. Hereinafter, the circuit operation will be described with reference to this diagram.

[0036] The Hall current detector CT detects the welding current flowing through the welding power source (not shown) and outputs a voltage proportional to the welding current to the terminal Vo (hereinafter referred to as the terminal Vo) of the connector CN1 of the Hall current detector CT. The following control power is supplied from the connector CN2 of the control printed board PCB via the terminal GND (hereinafter referred to as the terminal GND) of the connector CN1 of the Hall current detector CT to the terminal Vcc and the terminal Vee (hereinafter referred to as the terminal Vcc and the terminal Vee) of the connector CN1 of the Hall current detector CT.

[0037] (1) +15 V is supplied from the control power supply +15 V between the terminal Vcc and the terminal GND via the light emitting diode of the photocoupler PC1, and a positive side control current Ic flows for operating the Hall element HE and the operational amplifier OP1.

[0038] (2) -15 V is supplied from the control power supply -15 V to between the terminal Vee and the terminal GND via the light emitting diode of the photocoupler PC2, and the negative side control current Ie flows to operate the Hall element HE and the operational amplifier OP1.

[0039] The resistors R1 and R2 and the 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, in the case of a welding current of 100A, the voltage V1 is designed to be 1.00V. In addition, an output protection resistor r (about 100 ohms) of the operational amplifier OP1 is connected between the output of the operational amplifier OP1 and the terminal Vo (hereinafter referred to as the terminal Vo) of the connector CN1 of the Hall current detector CT.

[0040] The operational amplifier OP2 and the resistors R3 and R4 invert the voltage V2 of the terminal Vo. For example, when R3 = 10 k ohms and R4 = 5 k ohms, the inverting amplification is 1 / 2 times.

[0041] A bias resistor Rb (about 300k ohms) is connected to pin 2 (hereinafter referred to as pin 2) of connector CN2 of the control printed circuit board PCB via a 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 due to the output protection resistor r of the operational amplifier OP1, the voltage V2 of pin 2 is superimposed with a small voltage of V2=15V×r / (Rb+r)=15V×100 / (300k+100)=5mV.

[0042] If the circuit between terminal Vo and pin 2 is disconnected due to disconnection or connector detachment, the voltage V2 at pin 2 becomes the following voltage due to bias resistor Rb even though the welding power source is stopped, that is, the welding current is 0A.

[0043] V2=15V×R3 / (Rb+R3)=15V×10k / (300k+10k)=0.48V

[0044] When the voltage V2 of the pin 2 exceeds the reference voltage Vr, the comparator CP1 switches the output from low level (Low) (0V) to high level (High) (15V), and sets the output line disconnection signal Sab to high level. The reference voltage Vr is set to about 0.1V. When there is a disconnection between the terminal Vo and the pin 2, the value of the voltage V2 becomes V2 (0.48V)>Vr (0.1V) during the welding power supply stop, so the output line disconnection signal Sab becomes high level, and the disconnection between the terminal Vo and the pin 2 can be detected.

[0045] How to detect disconnection between each terminal and each pin between the connector CN1 of the Hall current detector CT and the connector CN2 of the control printed board PCB is described below.

[0046] There is a circuit break between the terminal Vcc and pin 1 of the connector CN2 of the control printed circuit board PCB (hereinafter referred to as pin 1): the control current Ic does not flow through the Hall current detector CT, and no current flows through the light-emitting diode of the photocoupler PC1. Therefore, the light-receiving transistor of the photocoupler PC1 is disconnected, and the control line break signal Lab also becomes a low level (0V), and the circuit break is detected.

[0047] There is a circuit break between terminal Vee and pin 4 (hereinafter referred to as pin 4) of connector CN2 of the control printed circuit board PCB: the control current Ie does not flow through the Hall current detector CT, and no current flows through the light-emitting diode of the photocoupler PC2. Therefore, the light-receiving transistor of the photocoupler PC2 is disconnected, and the control line break signal Lab also becomes a low level (0V), and the circuit break is detected.

[0048] There is a circuit break between the terminal GND and pin 3 of the connector CN2 of the control printed circuit board PCB (hereinafter referred to as pin 3): 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 the photocouplers PC1 and PC2. Therefore, the light-receiving transistors of the photocouplers PC1 and PC2 are disconnected, and the control line circuit break signal Lab also becomes a low level (0V), and the circuit break is detected.

[0049] There is a circuit break between terminal Vo and pin 2: When the welding power supply is stopped and the welding current is not flowing, the voltage V2 of pin 2 becomes V2=0.48V as described above, and becomes V2(0.48V)>Vr(0.1V), so the output of comparator CP1 also becomes a high level (15V), and the output line circuit break signal Sab becomes a high level, and the circuit break is detected.

[0050] [Implementation method 2]

[0051] Figure 2 This is a circuit diagram according to Embodiment 2 of the present invention. Hereinafter, referring to this diagram, the circuit operation will be described only for the parts different from Embodiment 1.

[0052] In the first embodiment, the bias resistor Rb is always connected to the control power supply +15V and the No. 2 pin. When the welding power supply is powered on, the bias voltage of 5mV caused by the bias resistor Rb is also superimposed on the output voltage V2 of the Hall current detector CT. When the welding current flowing in the welding power supply is AC, a signal of 5mV (0.5A) is added to the positive welding current, and a signal of 5mV (0.5A) is subtracted from the negative welding current, resulting in a difference between the positive and negative currents.

[0053] To solve this problem, Figure 2 As shown, a switch SW is provided between the control power supply +15V and the bias resistor Rb. When the welding power supply is stopped, the switch SW is closed, and the bias resistor Rb is connected between the control power supply +15V and the No. 2 pin, so that a disconnection can be detected between the terminal Vo and the No. 2 pin. When the welding power supply is energized, the switch SW is opened to stop the bias voltage superposition caused by the bias resistor Rb between the No. 2 pins. In this way, the positive and negative current differences generated when the welding power supply is energized can be prevented.

[0054] Embodiment 1 and Embodiment 2 Figure 1 The circuit diagram of the figure is an example, and for example, a relay that mechanically opens and closes contacts 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.

Claims

1. A circuit breaker detection device, characterized in that: have: A Hall current detector for detecting a welding current flowing in a welding power source; A power supply circuit supplies control power to the Hall current detector; A bias resistor connected to the output of the Hall current detector and the control power supply; as well as an output line disconnection detection unit, for detecting a disconnection of an output line of the Hall current detector, The output line disconnection detection unit determines that an 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.

2. The circuit break detection device according to claim 1, wherein: The disconnection detection device comprises: a switch connected between the bias resistor and the control power supply, The switch is closed when the welding power source is stopped, and is opened when the welding power source is energized.

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