ABSTRACT
The switched-mode power supply (SMPS) was originally developed by NASA in the 1960s as a compact DC source for space vehicles which could provide a constant, and controllable, output voltage with minimal ripple over a wide range of load current and which could operate from a variable source. If a comparison is made between a conventional, linear power supply and an SMPS of the same rating, the SMPS will be of smaller size, lighter weight and higher efficiency. An SMPS is essentially a DC chopper with a filtered and smoothed output. An SMPS may also be a source of both electromagnetic and radio frequency interference which may appear in the supply, as radiated noise or in the output. Sensing voltage is taken to the controller integrated circuit which will then shut down the SMPS on detecting an overload condition. A conventional DC arc welding system requires a high current at a voltage in the range 50 V to 100 V.
