Synchronous rectifier controller maximises efficiency across load profiles

August 04, 2015 // By Graham Prophet
NXP Semiconductor has posted details of the TEA1995T, which it terms the first product of a new generation of Synchronous Rectifier (SR) controller ICs for switched mode power supplies, with adaptive gate drive for maximum efficiency at any load.

The TEA1995T is a dedicated controller IC for synchronous rectification on the secondary side of resonant converters. It has two driver stages for driving the SR MOSFETs which rectify the outputs of the secondary transformer windings. The two gate driver stages have their own sensing inputs and operate independently of each other.

TEA1995T can also be used in multi-output flyback converters with the SR MOSFET placed at the low side. The device is fabricated in a Silicon On Insulator (SOI) process. It applies adaptive gate drive for maximum efficiency at any load, and requires supply current in no-load operation of less than 200 μA.

Features include;

  1. supply voltage range from 4.5 V to 38 V;
  2. dual synchronous rectification for LLC resonant designs, in SO8 package;
  3. synchronous rectification for multi-output flyback converters;
  4. 5V operation with logic level SR MOSFETS;
  5. differential inputs for sensing the drain and source voltage of each SR MOSFET.

It offers SR control without minimum on-time; adaptive gate drive for fast turn-off at the end of conduction; and under-voltage lock out with active gate pull-down.

Two demonstration boards are available; TEA1995DB1294 is an add-on board is designed for incorporation into existing resonant power supplies or multi-output flyback power supplies by replacing the secondary rectifier diodes. The add-on board consists of the TEA1995 Dual SR controller IC and low-ohmic MOSFETs in TO-220 package. The TEA1995DB1295 add-on board is similar but carries low-ohmic MOSFETs in LFPAK packages.