Patent ID: 7095634

Claim:
An apparatus which may be used for welding, said apparatus comprising: a) a quasi-resonant soft-switching inverter, wherein said inverter comprises: 1) a connection means to a first power source, wherein said first power source comprises: i) a DC voltage power supply terminal; and ii) a reference terminal; and 2) at least one quasi-resonant type switching leg, wherein each said leg comprises: i) an even number of switches connected in series between said first power source and said reference terminal, wherein; aa) each said switch is connected in parallel to a capacitive element; and bb) each said switch is connected in series to an inductive element forming resonance element; and ii) an output terminal, wherein said output terminal is located between the two central switches of said leg; and b) an apparatus power source, wherein said apparatus power source comprises: 1) a control circuit for said switches, wherein: i) said control circuit sends a control signal; and ii) said control signal comprises at least one member selected from the group consisting of: aa) an on-signal; and bb) an off-signal; 2) a transformer, wherein said transformer comprises: i) a primary element linked to said output terminal; and ii) a secondary element linked to a rectifier, wherein said rectifier delivers a power source output DC voltage; 3) a detection circuit, wherein: i) said detection circuit detects the voltage between the power electrodes of each said switch; and ii) said detection circuit sends a detection voltage signal; and 4) a pilot circuit, wherein: i) said pilot circuit receives said control signal and said voltage signal; and ii) said pilot circuit sends a pilot signal to each said switch, wherein said pilot signal comprises at least one member selected from the group consisting of: aa) an off-signal corresponding to a first set of conditions, wherein said first set of conditions comprises at least one member selected from the group consisting of: aaa) said control signal is an off-signal; and bbb) said voltage between said electrodes is substantially non-zero; and bb) an on-signal corresponding to a second set of conditions, wherein said second set of conditions comprises: aaa) said control signal is an on-signal; and bbb) said voltage between said electrodes is substantially zero.