EDN’s 20th annual Innovation Awards Finalists
-- EDN, February 18, 2010
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&& PREVIOUS FINALIST | MAIN | NEXT FINALIST >> Category: Components Finalist: IR1168 SmartRectifier, International Rectifier  The IR1168 SmartRectifier is a 200V dual smart secondary-side rectifier driver IC designed to drive two N-Channel power MOSFETs used as SRs (synchronous rectifiers) in resonant half-bridge topologies. At the core of this device are two high-voltage (200V) high-speed comparators. These differentially sense the drain-to-source voltage of the MOSFET, using the RDS(ON) of the device as a shunt resistance, and hence determine the polarity and level of the device currents. Dedicated internal logic manages the ON/OFF of each device in close proximity to the zero-current transition. The device uses the SmartRectifier control technique, which compares the sensed voltage across the MOSFET with two negative thresholds to determine the turn-on and turn-off transitions for the device. The most negative of these two thresholds, VTH2, detects current through the body diode and, hence, controls the turn-on transition for the power device. Similarly, a second negative threshold, VTH1, determines the level of the current at which the device turns off. A third threshold voltage, VTH3, acts as a reset threshold governing the resetting of an internal one-shot when the cycle is completed and the VDS voltage turns positive and starts to increase again, and the system is ready for the next conduction cycle. By governing the drive level of the secondary-side MOSFETs according to these three thresholds, the IR1168 ensures accurate performance without the need of a PLL or external timing sources. The IR1168-based solution delivers an efficiency improvement of 1.5% for a standard 240W LCD TV SMPS and a reduction of rectifier device temperature of 25°C while shrinking board size by two-thirds. |
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