LED Streetlight Driver Solution
The PR788 component from Texas Instruments is a 100W offline AC to DC LED current driver with power factor correction. This design is a two stage converter item with a universal input boost PFC stage providing a 240V to 400V DC output and a low side buck stage providing the current source to power the LED’s.
This product was designed to support up to 30 high brightness LED’s in series up to 900mA average current. The design incorporates interface for microprocessor control to allow for shutdown into a low power mode (<0.5W) and PWM dimming of the LED’s.
The PFC stage is a critical conduction mode boost converter with a boost follower feature implemented. The boost follower is set to provide a DC output of 240V to 400V. The lower DC output at low input voltage results in improved efficiency at low line conditions Vs a fixed 400V output. The minimum regulation point was set at 240V to allow the design to be scaled to power up to 50 LED’s in series. The Golden Dragon OVAL LEDs from OSRAM providing already a optimized light output through their OVAL beam pattern. For the best thmermal management DK Thermal produced the MCPCBs based on Laid technolgies T - LAM material. The result is a homogenous streetlighting illumination with a high application efficiency.
