Power converter with low loss switching

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
• a convertor, connected to receive the output of the pre-regulator and provide a welding output;
• wherein the pre-regulator is a slow voltage transition and a slow current transition switched boost convertor;
• wherein the boost converter includes a boost inductor, a switch, and an output capacitor;
• and
• further wherein the converter includes a snubber, including a snubber capacitor, a snubber inductor, a first snubber diode, a second snubber diode, a third snubber diode, a fourth snubber diode, and first and second snubber capacitors;
• the snubber inductor, switch, and fourth diode are connected such that current may flow from the boost inductor to any of the snubber inductor, switch, and fourth diode;
• current flowing through the fourth diode can flow through either the third diode or the second capacitor;
• current flowing from the boost inductor through the snubber inductor can flow through either the first diode or the first capacitor;
• the fourth diode and the second capacitor are connected across the switch;
• current flowing through the third diode can flow through either the first capacitor and the snubber inductor or through the second diode;
• and
• current flowing through the first and second diodes flows to the output.

A method of providing welding power, comprising:

• 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 pre-regulating includes slow voltage transition and slow current transition switching a boost convertor.

A method of providing welding power, comprising:

• 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 pre-regulating includes slow voltage transition and slow current transition switching a boost convertor;
• and
• further wherein pre-regulating includes the steps of maintaining a boost converter switch off, and allowing current to flow through a boost inductor, a snubber inductor, and a first diode, to the dc bus;
• turning the switch on and diverting current from the snubber inductor to the switch;
• reversing the current in the snubber inductor;
• discharging a second capacitor through a first capacitor, a third diode, and the snubber inductor, thereby transferring energy from the second capacitor to the snubber inductor;
• diverting current through a fourth diode, the third diode and the first capacitor when the second capacitor is discharged, thereby transferring energy from the snubber inductor to the first capacitor;
• turning the switch off and diverting current through the fourth diode and into the second capacitor;
• allowing the voltage on the second capacitor to rise until current begins to flow from the snubber inductor to the first capacitor;
• diverting current from the second capacitor through a third diode to the second diode;
• allowing the current flowing from the boost inductor to the snubber inductor to increase until all of the current from the boost inductor flows into the snubber inductor;
• diverting current from the first capacitor to the first diode;
• and
• repeating the above.

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 slow voltage transition and slow current transition switching boost convertor means.