Power convertor with low loss switching

A method of providing welding power, comprising the steps of:

• rectifying an input line voltage;
• pre-regulating the input line voltage to provide a dc bus;
• and
• converting the dc bus to a welding output;
• wherein the step of pre-regulating includes SVT and SCT switching a boost convertor.

A welding power supply comprising:

• an input rectifier means for receiving an input line voltage and providing a rectified voltage;
• a pre-regulator means for receiving the rectified voltage and providing a dc bus, wherein the pre-regulator means is connected to the rectifier means;
• and
• a convertor means for receiving the output of the pre-regulator means and provide a welding output, wherein the converter means is connected to the pre-regulator means;
• wherein the pre-regulator means includes SVT and SCT switching means.

A welding power supply comprising:

• an input rectifier configured to receive an input line voltage and provide a rectified voltage on an output;
• a pre-regulator connected to receive as an input the output of the rectifier and provide a dc bus as an output;
• and
• an invertor, connected to receive the output of the pre-regulator and provide a welding output;
• wherein the inverter includes a snubber circuit having a first switch in anti-parallel with a first diode, and a second switch in anti-parallel with a second diode, and wherein the combination of the first switch and first diode are connected in series with the combination of the second switch and the second diode, and wherein the first and second switches are connected in opposing directions.

A method of providing welding power comprising the steps of:

• turning on a first power switch and a first snubber switch, and allowing current to flow through the first power switch, a first dc bus, a first powers capacitor, and in a first direction through a transformer;
• turning the first power switch off and allowing current to flow through the first snubber switch, a second snubber diode, a snubber capacitor, and through the transformer in the first direction, while the first power switch is turning off, to provide a slow voltage transition off;
• allowing current to flow through a second anti-parallel power diode, a second DC bus, a second power capacitor, and through the transformer in the first direction, while the first power switch is continuing to turn off, to continue providing a slow voltage transition off;
• turning off the first snubber switch;
• turning on a second power switch and a second snubber switch after the first power switch is off, and allowing current to flow through the second power switch, the transformer in a second direction, the second power capacitor, and the second bus;
• turning the second power switch off and allowing current to flow through the second snubber switch, a first snubber diode, the transformer in the second direction, and a snubber capacitor, while the second power switch is turning off, to provide a slow voltage transition off;
• allowing current to flow through a first power diode, the transformer in the second direction, and the first power capacitor, while the second power switch is turning off, to provide a slow voltage transition off;
• turning off the second snubber switch;
• and repeating these steps.