| 摘要 |
An electric welding apparatus which, for controlling at least one welding parameter, such as welding voltage or welding current, comprises a switching mode power supply (SMPS) as control element, the switching mode power supply preferably being regulated on the primary. The actual values of voltage and current are taken from the output of the switching mode power supply and fed to an analog control circuit. The set values of voltage and current are fed to a microprocessor via an entry keyboard, and in the microprocessor they are stored in a memory and passed on in analogous form to the analog control circuit which carries out a comparison of set value and actual value and, in dependence thereon, produces an error signal that is fed to a pulse width modulator of the switching mode power supply. The pulse width modulator is connected to the driver stages of the switching stages of the switching mode power supply, which switching stages are designed as boost regulator of buck regulator, and thus a pulse width modulation of the current pulses of the switching stages is effected in dependence on the difference between actual and nominal value. The converter section of the switching mode power supply preferably is designed as a modified single-ended buck regulator or as a push-pull full bridge, wherein it is operated at a fixed clock frequency of about 25 kHz. The secondary coil of the transformer of the switching mode power supply being either direct in connection with the output connection terminals of the switching mode power supply, or a secondary rectifier is connected between the secondary coil and the output connection terminals, whereby the secondary rectifier can be bridged by switch means.
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