JPS6323515A - Protector of electric source for welding and cutting - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protection device for a power source for arc welding or plasma cutting, and more particularly to a protection device against excessive or insufficient input voltage.

[Conventional technology]

If the input voltage of the welding/cutting power supply fluctuates, an excessive input may destroy the semiconductor elements in the main circuit, or an insufficient input may cause the control circuit to malfunction. A protection device is provided that performs protective operations such as stopping the output of the power source and issuing an abnormality alarm based on the detection signal.

The one shown in Figure 3 is an example of a conventional protection device of this type.
The input voltage from the AC power supply 1 is transferred to a transformer 7, a full-wave rectifier 8,
A configuration in which the voltage of the smoothing capacitor 10 of the control power supply supplied to the control circuit 11 as DC rectified and smoothed by the smoothing capacitor 10 is compared with the reference voltage V ref by a comparator 16 to detect excessive or insufficient input voltage. It becomes.

In this circuit system, since the voltage of the smoothing capacitor 10 compared with the reference voltage vYef is obtained by quasi-average detection of the output waveform a of the full-wave rectifier 8, as shown in FIG. 4c and d, the control circuit 11 It is easily affected by load fluctuations.

C is a case where the load current is small, and d is a case where the load current is large.

[Problem that the invention seeks to solve]

2, in conventional protection devices that use the control power supply to obtain the voltage to be compared, the voltage to be compared tends to fluctuate due to the influence of load fluctuations in the control power supply, resulting in stable over-input. , it is difficult to detect under-input, and therefore, appropriate protection may not be possible. Further, in order to eliminate such problems, when a transformer and a rectifier circuit type for detecting excessive input and insufficient input are added, the protective device becomes expensive.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a protection device for a welding/cutting power source that is inexpensive and operates stably against excessive or insufficient input voltage.

[Failure to solve the problem]

For the above purpose, a reverse blocking diode is inserted between the output terminal of the aftereffect rectifier of the control power supply that rectifies and smoothes the AC input and supplies it to the control circuit and the smoothing capacitor, and the output of the full-wave rectifier described in 1. The pulsating voltage taken from the end is detected by an integrating circuit using an operational amplifier to detect the average value or quasi-average value.
This is achieved by comparing the output voltage of the integrating circuit with a reference voltage using a comparator to detect whether the input voltage is too high or too low.

[Effect]

In the present invention, since the backstop diode 1 is inserted between the output end of the full-wave rectifier of the control power supply and the smoothing capacitor, the voltage taken out from the output end of the aftereffect rectifier is an unsmoothed pulsating current. When this pulsating current voltage is inputted into an integrating circuit using an operational amplifier, a waveform voltage resulting from mean value detection or quasi-mean value detection of the pulsating current voltage is output from the integrating circuit. The output voltage of this integrating circuit reflects the input voltage from the AC power supply, and is less susceptible to load fluctuations of the control power supply than the voltage of the smoothing capacitor, which is subjected to quasi-average detection. By comparing the output voltage of 1! with the 1! voltage, it is possible to stably detect whether the input voltage is too high or too low.

〔Example〕

FIG. 1 shows a circuit configuration of an embodiment of the present invention.

The main circuits of the welding/cutting power supply in this embodiment include a primary rectifier circuit 2 that converts input voltage from an AC power source into DC, an output control inverter circuit 3 that converts DC to high-frequency AC, and a high-frequency transformer. 4. It consists of a secondary rectifier circuit 5 that converts the secondary output of the transformer into direct current, and a direct current reactor 6 that smoothes the output current.

Transformer7. The full-wave rectifier 8 and the smoothing capacitor 10 constitute a control power source that supplies the input voltage from the AC power source 1 as rectified and smoothed DC to the control circuit 1.

In this embodiment, a reverse blocking diode 9 is inserted between the aftereffect rectifier 8 and the smoothing capacitor 10, and an unsmoothed pulsating voltage having a waveform as shown in FIG. 2a is taken out from the output terminal A of the aftereffect rectifier 8. , this is applied as an input voltage ■; to an integrating circuit 12 composed of an input resistor 13, an integrating capacitor 14, and an operational amplifier 15, and the output voltage ■ of the integrating circuit 12 is obtained. By comparing Vyef with the reference voltage Vyef by the comparator 16, it is detected whether the input voltage from the AC power source is too high or too low.

In the capacitor input type control power supply shown in the figure, the influence of load fluctuations on the control circuit IJ tends to appear at the peak of the full-wave rectifier output waveform a shown in FIG. Since the output voltage Vo of the integrating circuit 12 is the overall average value or quasi-average value of the output waveform a of the aftereffect rectifier as shown in FIG. 2 (1), quasi-average detection is performed as in the conventional example shown in FIG. It is clear that this is less susceptible to load fluctuations than when the voltage of the smoothing capacitor 10 is used as the voltage to be compared.

The protection device of this embodiment further delays the output of the comparator 16 by a noise removal circuit 17 in order to avoid interrupting the welding/cutting work due to transient noise, and the comparator 16 detects excessive or insufficient input. Only when the output continues for a predetermined period of time or longer, the signal output from the noise removal circuit 17 performs protective actions such as stopping the output of the welding/cutting power supply and alarming abnormalities. This prevents damage to the switching elements (e.g., switching element 3) and malfunction of the control circuit 11 due to an excessively low input voltage.

〔Effect of the invention〕

According to the present invention, the voltage to be compared for detecting over/under input voltage can be obtained from the rectifier circuit constituting the control power supply in a stable form that is less affected by load fluctuations in the control circuit. There is no need to provide a separate rectifier circuit, and the welding/cutting power source can be properly protected against excessive or insufficient input using an inexpensive device.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of the present invention, Figure 2 is its voltage waveform diagram, Figure 3 is a circuit diagram of a conventional example with parts common to Figure 1 omitted, and Figure 4 is its voltage waveform diagram. FIG. 1... AC power supply 2-6... Main circuit section 7.
...Transformer 8...Aftermath rectifier 9...Reverse blocking diode 10...Smoothing capacitor 11...Control circuit 12...
...Integrator circuit 13...Input resistance 14...
Integrating capacitor 15... Operational amplifier 16... Comparator Junnosuke Nakamura = 7- Fig. 1 1: AC power supply 2IJF, l○ or smoothing capacitor 2 primary side rectifier circuit 11: Control circuit 3 = Inverter circuit 12: Integrating circuit 4: High-rise skin transformer
16: Inlet oyster L hole 5: Secondary rectifier circuit
14: Integrating capacitor 6: DC reactor
15: Operational amplifier 7: Transformer 16:
Baboon comparator 8: Full-wave rectifier @ 17: Noise removal circuit 9: Reverse blocking diode Figure 2 Figure 3 Figure 1: AC power supply 7゛Transformer 8: Full-scale rectifier 10: Smoothing capacitor 11: Control circuit 16 : Baboon comparison sign number 4

Claims (1)

[Claims] 1. In a protection device that detects excessive or insufficient input voltage of a welding/cutting power supply and performs a protective operation to prevent destruction of main circuit elements and malfunction of control circuits based on the detection signal,
A reverse blocking diode is inserted between the output end of the full-wave rectifier of the control power supply that rectifies and smoothes the AC input and supplies it to the control circuit and the smoothing capacitor, and the pulse taken out from the output end of the full-wave rectifier is inserted. The current voltage is average-value detected or quasi-average detected by an integrating circuit using an operational amplifier, and the output voltage of the integrating circuit is compared with a reference voltage using a comparator to detect excessive or insufficient input voltage. Welding and
Protection device for power supply for disconnection.