Patent ID: 6111769
Filing Date: 2000-08-29
Classification: H02M,Y02B

Abstract:
A synchronous rectifier circuit for a bridge type DC-to-DC converter comprising:a primary transformer having a primary and a secondary winding, said secondary winding having a first and a second terminal;a first and a second synchronous rectifier operably coupled to said first and second synchronous terminals of said secondary winding, wherein said first and second synchronous rectifiers are MOSFETS;a first and a second totem pole driver operably coupled to said first and second synchronous rectifiers to provide current drain;an external driver including a timing circuit and a transformer with a primary winding and a secondary winding, said secondary winding including a first and a second terminal, said timing circuit operably coupled to said primary winding; anda DC level shifter circuit including a first and a second switch driver coupled to said first and second terminals of said secondary winding of said external driver, respectively, said first switch driver having a first capacitor having a first and a second end, said first capacitor providing storage for circuit current, a first resistor coupled in parallel to said first capacitor whereby the capacitance of said first capacitor is fully discharged, and a first diode coupled to said secondary winding of said transformer, said first switch driver coupled to said first totem pole driver;wherein said DC level shift circuit is connected to said first and second totem pole drivers whereby said timing signal to turn on and turn off said first and second synchronous rectifiers is transferred from said first and second switch drivers through said first and second totem pole drivers to said first and second synchronous rectifiers, and whereby said first switch driver provides the appropriate timing to turn on and off said first synchronous rectifier.