JPH0355225B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an auxiliary power supply circuit used in a control circuit or the like in a welding device.

The welding equipment includes a welding power source that supplies power to the welding load, a control power source for output voltage and output current control, sequence control, etc., and an electric motor to feed the consumable electrode and drive the welding cart. An auxiliary power source such as a commercial power source is required.

For these auxiliary power sources, a method is generally adopted in which a commercial AC power source is adjusted to a desired voltage using a transformer and then used as AC or after being rectified as DC. However, since the capacity of the auxiliary power supply normally requires several hundred VA to several KVA, when this is obtained using a commercial frequency transformer, not only does the transformer itself become large, but the output must be rectified to create a direct current. In this case, the smoothing circuit also becomes large, and the device is too large to be ignored in terms of volume, weight, and price compared to the welding power source. Furthermore, recently, as a power source for welding, direct rectification of AC power at a commercial frequency is used to convert the DC power obtained into AC power at a frequency higher than the commercial frequency, usually around several KHz to 100 KHz.
A switching type power supply has been proposed in which the converted output is appropriately adjusted by a transformer and then passed through a rectifier circuit to obtain a DC output. Although the transformer and smoothing reactor, which account for a large portion of the weight of such welding power sources, are made smaller and lighter by handling high frequencies, the auxiliary power supply used for them is Since the conventional system uses a commercial AC power source after adjusting it as is, the overall effect of reducing size and weight has not been sufficiently achieved.

The present invention obtains power directly or indirectly from a commercial AC power source in an auxiliary power supply device, converts the power to high frequency AC, adjusts the power, and then converts it back to a desired frequency, such as DC or commercial frequency. By converting this into auxiliary power, we aim to make the device as compact and lightweight as possible.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a commercial frequency AC power supply, and 4 is a welding load consisting of an electrode 41, a workpiece 42, and a welding arc 43. Reference numeral 5 denotes a motor for feeding the electrode 41, which is controlled by a motor speed control circuit 51. 6 is an auxiliary power supply device of the present invention, 7 is a forward conversion circuit that rectifies the output of the commercial frequency AC power source 1 to obtain DC, and 8 is a forward conversion circuit that obtains the DC output from the forward conversion circuit 7 and converts it into high frequency power. An inverse conversion circuit; 9 is a high-frequency transformer for converting the high-frequency output of the inverse conversion circuit 8 into a voltage suitable for welding; 11 is a rectifier circuit that rectifies the output of the high-frequency transformer 9 into a DC output; 12 is a rectifier circuit; This is an output adjustment circuit using transistors and the like to adjust the output of No. 11 to a desired value. The auxiliary power supply circuit 6 includes a frequency conversion circuit 66 that receives the DC output from the forward conversion circuit 7 and converts it into high-frequency power, and an inverse conversion circuit 8 and an output adjustment device 1 for converting the output of the frequency conversion circuit 66.
The first voltage is converted to a voltage suitable for the second power supply.
A first output circuit includes a transformer 67 and a rectifier circuit 68, and a second transformer 69 converts the output of the frequency conversion circuit 66 into a voltage suitable for the motor speed control circuit 51.

When configured as shown in FIG. 1, the transformer 67,
69 indicates the output frequency of the frequency conversion circuit 66 by several hundred
For high frequencies from Hz to 100KHz, a very small iron core can be used, and a rectifier circuit 68 can be used.
Since the smoothing circuit (not shown) provided in the auxiliary power supply device 6 may have an extremely short time constant, the auxiliary power supply device 6 can be extremely small and lightweight. Here, the frequency conversion circuit 66
When an output regulator is provided as a conversion circuit that can adjust any one or more of the output pulse width, repetition frequency, and output peak value of a frequency conversion circuit, or when the output of a frequency conversion circuit is taken out by a transformer connection, a transformer is used. The containers 67 and 69 can also be omitted.

In the embodiment shown in FIG. 1, the motor speed control circuit 5, which is one of the output targets of the auxiliary power supply 6,
1 is not provided with a rectifier circuit since it is operated by high-frequency AC voltage, but a rectifier circuit is naturally required for an output object that operates by DC power. Furthermore, if necessary, in place of the rectifier circuit, another conversion circuit for converting high frequency power back to low frequency power such as a commercial frequency may be provided, such as an inverse conversion circuit 8, an output adjustment circuit 12, a motor speed control circuit 51, etc. It is possible to use the same equipment as is when controlling the conventional commercial frequency.

Furthermore, instead of the transformers 67 and 69, semiconductor switching elements such as thyristors and transistors that control the output of the frequency conversion circuit 66 on and off, or analog elements such as transistors that can change impedance in an analog manner may be used. can.

Furthermore, the frequency conversion circuit 66 may be of a type that outputs a DC voltage on and off using chopper control instead of an AC output. Furthermore, by inputting the high frequency output of the transformer 69 as is to the motor speed control circuit and controlling the polarity and effective value by appropriately switching on and off this high frequency voltage using a switching element, extremely accurate control is possible. becomes.

As described above, according to the present invention, it is possible to make the auxiliary power source required for controlling the welding equipment extremely small and lightweight, and the output is adjusted after converting the commercial AC power source into high-frequency power. The welding device as a whole can be made smaller and lighter, and the price can be lowered without impairing the effect of making the welding power supply circuit smaller and lighter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1...Commercial frequency AC power supply, 6...Auxiliary power supply device, 66...Frequency conversion circuit, 67, 69...
Transformer, 68... Rectifier circuit, 7... Forward conversion circuit,
8...Inverse conversion circuit.

Claims (1)

[Scope of Claims] 1. A welding power source that includes a forward conversion circuit that obtains DC power from a commercial AC power source and an inverse conversion circuit that converts the output of the forward conversion circuit to AC power with a higher frequency than the frequency of the commercial AC power source. The auxiliary power supply device used for the welding power source includes a frequency conversion circuit that obtains power from the forward conversion circuit of the welding power source and converts it into AC having a higher frequency than commercial AC, and converts the output of the frequency conversion circuit into desired voltage-current characteristics. An auxiliary power supply device for welding consisting of an output adjustment circuit for output. 2. Claim 1, wherein the frequency conversion circuit is a conversion circuit whose output value is variable, and the output adjustment circuit is a circuit that acts on the frequency conversion circuit to set the output value of the frequency conversion circuit. Auxiliary power supply device for welding as described in. 3. The frequency conversion circuit is a conversion circuit that converts only the frequency of input power and outputs the same, and the output adjustment circuit is a transformer, a switching element, or an analog device that receives the output of the frequency conversion circuit and adjusts the voltage and current. An auxiliary power supply device for welding according to claim 1 or 2, which comprises an element. 4. The welding auxiliary power supply device according to claim 1, wherein at least one of the frequency conversion circuit and the output adjustment circuit is a circuit that obtains a plurality of outputs.