US 7,321,498 B2
DC-DC converter having synchronous rectification without cross conduction
George L. Cebry, Glendale, Ariz. (US)
Assigned to Honeywell International, Inc., Morristown, N.J. (US)
Filed on Oct. 31, 2005, as Appl. No. 11/264,067.
Prior Publication US 2007/0097714 A1, May 03, 2007
Int. Cl. H02M 3/335 (2006.01)
U.S. Cl. 363—21.02  [363/21.04] 16 Claims
OG exemplary drawing
 
1. A timing circuit for a synchronous rectifier having an input MOSFET switch coupled to primary windings of an isolation transformer, an output MOSFET switch coupled to secondary windings of the isolation transformer, and a complementary output MOSFET switch coupled to an output terminal, the timing circuit comprising:
a first timing output signal circuit responsive to a pulse width modulated signal at a first input terminal and providing first and second timing output signals that switch low at time t1 and high at time t4 to control the input MOSFET switch and output MOSFET switch, respectively, wherein the first timing output signal circuit comprises:
a first resistor coupled between the input terminal and a first node;
a first diode having a cathode connected to the input terminal and an anode connected to the first node;
a first capacitor coupled between the first node and a first voltage reference; and
a first comparator having a positive input connected to the first node, a negative input connected to a second voltage reference, and an output providing the first and second timing output signals; and
a second timing output signal circuit responsive to the pulse width modulated signal and providing a third timing output signal that switches high at time t2 and low at time t3 to control the complementary output MOSFET switch.