Soft transition converter

An AC-DC converter comprising of:

• a low impedance AC sources providing an alternation of a positive voltage, a negative voltage and a dead time;
• an inductive element connected in series with said AC source;
• a bridge of rectifiers means and capacitors having a first input terminal a second input terminal a first output terminal and a second output terminal;
• the first rectifier means being connected between the first input terminal and the first output terminal with the cathode to the first output terminal,
• the second rectifier means being connected between the first input terminal and the second output terminal, with the cathode to the first input terminal,
• the first capacitor connected in between the first output terminal and the second input terminal, and
• the second capacitor connected between the second input terminal and the second output terminal;
• The said AC voltage source in series with said inductive element is connected between the first input terminal and the second input terminal;
• a load is connected between the first output terminal to the second output terminal;
• the said voltage source modulating the energy transfer through said inductor element and said rectifiers to said capacitors and said load by changing the ratio between the duration of said positive and negative alternation and the repetition period of the signal provided by said voltage source.

The circuit of claim wherein said AC voltage source is generated by the secondary windings of two transformers, a first transformer and a second transformer, each having primary and said secondary windings;

• said secondary windings of said transformers are connected in series;
• the said primary winding of the first transformer is connected to first and second primary output terminal;
• the said primary winding of the second transformer is connected to third and fourth primary output terminal;
• a DC voltage source having a positive and a negative terminal;
• a bridge switching circuit for producing a chopped voltage from said DC input voltage, said switching circuit having a said first primary input terminal, a said primary second input terminal, a said third primary input terminal, and a said fourth primary input terminal, said first, second, third and fourth primary input terminals being adapted for connection to said DC input voltage, said switching circuit including
• a first switching element (M11) having a parasitic drain to source capacitance C11, M11 being connected between positive terminal of DC voltage source and said first primary input terminal,
• a second switching element (M12) having a parasitic drain to source capacitance C12, M12 being connected between said second primary input terminal and negative terminal of DC voltage source,
• a third switching element (M13) having a parasitic drain to source capacitance C13, M13 being connected between positive terminal of DC voltage source and said third primary input terminal, and
• a fourth switching element (M14) having a parasitic drain to source capacitance C14, M14 being connected between said fourth primary input terminal and negative terminal of DC voltage source;
• means for determining and controlling a conduction interval for each M11-M41 to produce a first half-cycle, including an on-time wherein M11 and M12 are conducting and M13 and M14 are not conducting, a dead time wherein M11, M12, M13 and M14 are conducting, a second half-cycle, including an on-time wherein M13 and M14 are conducting and M11 and M12 are not conducting, a dead time wherein neither switching element M11, M12, M13 and M14 is not conducting;
• the turn on of said switches M11-M14 is performed when the voltage across C11-C14 reaches a desired level.