Novel zero-voltage-switching family of isolated converters

• US 5,325,283 A
• Filed: 06/08/1992
• Issued: 06/28/1994
• Est. Priority Date: 06/08/1992
• Status: Expired due to Fees

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: The Center For Innovative Technology
• Inventors: Farrington, Richard W., Lee, Fred C., Jovanovic, Milan M.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US07/896,093
• Time in Patent Office: 750 Days
• Field of Search: 363/17, 363/20, 363/21, 363/56, 363/98, 363/97, 363/132, 363/131
• US Class Current: 363/21.03
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An isolated zero-voltage-switching converter in which the magnetizing inductance of the isolating transformer is a resonant element and an open circuit is provided on the secondary side of the transformer during the time interval when both primary switches are off. When the secondary of the transformer is open, the magnetizing inductance is in series with the capacitances of the primary switches, thus forming a resonant circuit.

Claims

1. An isolated, resonant, zero-voltage-switching converter, comprising in combination:

a transformer having a primary winding and a secondary winding, said transformer having a magnetizing inductance;

a direct current voltage source;

primary switching means including a primary parasitic switch capacitance for periodically coupling said voltage source to said primary winding;

a resonant circuit including said primary switch capacitance and said magnetizing inductance for establishing a zero voltage across said primary switching means immediately prior to turn-on of said primary switching means;

a load impedance;

means coupling said secondary winding of said transformer to said load impedance;

said means coupling said secondary winding, including an LC filter, and a unidirectional switch that periodically blocks current flow in said secondary winding when a zero impedance condition exists across said primary winding.

2. An isolated, resonant, zero-voltage-switching converter as in claim 1, wherein said converter has a bridge-type topology and said means coupling said secondary winding of said transformer to said load impedance further includes a free-wheeling diode connected to the input of said LC filter to provide a path for filter inductor current when said switching means is in an off state.

3. An isolated, resonant, zero-voltage-switching converter as in claim 1, wherein said unidirectional switch comprises a saturable inductor and a rectifier diode connected in series.

4. An isolated, resonant, zero-voltage-switching converter as in claim 2, wherein said unidirectional switch comprises a saturable inductor and a rectifier diode connected in series.

5. An isolated, resonant, zero-voltage-switching converter as in claim 3, further including a linear inductor connected in parallel with said saturable inductor and a capacitance in parallel with said rectifier diode thereby providing zero voltage turn-off of said rectifier diode.

6. An isolated, resonant, zero-voltage-switching converter as in claim 4, further including a linear inductor connected in parallel with said saturable inductor and a capacitance in parallel with said rectifier diode thereby providing zero voltage turn-off of said rectifier diode.