Reference design ensures high efficiency, long lifetime for T8 retrofits

December 05, 2012 // By Christoph Hammerschmidt
Power Integrations has introduced two reference designs describing high-efficiency, non-isolated, high-power-factor (PF) LED drivers for T8 tubes. The designs feature low component count and leverage simple magnetics and single-sided boards yielding industry-leading power densities of 14.2 W/in³.

Based on the LNK460KG LED driver from Power Integrations’ LinkSwitch-PL family of ICs, the circuits detailed in DER-337 (high-line) and DER-345 (low-line) use single-stage non-isolated topologies which result in a profile of only 8 mm - small enough to be mounted behind the LEDs in the T8 tube.

The buck-boost (DER-337) or buck (DER-345) configurations deliver a power factor greater than 0.9 and low THD, meeting EN61000-3-2 C limits. The designs are EMI compliant, easily meeting the EN55015 (EMI) class B specification. The integrated single-stage driver IC controls both PFC and constant-current output resulting in a solution that uses fewer than 30 components. Both drivers deliver 20 W (85 V at 240 mA) at an efficiency as high as 92 % (DER-337) and 89 % (DER-345).

According to Power Integrations, the LED tube market is moving to non-isolated drivers, which boost system efficiency and reduce the temperature of the driver board and components. These boards use approximately half the number of components of isolated designs and are typically 3 - 4 % more efficient. With a high power factor and low total harmonic distortion they suit commercial and industrial lighting applications throughout the world.

Each document contains the LED driver specification, schematic, PCB details, bill of materials, transformer documentation and detailed performance characteristics. Download DER-337 at; DER-345 at