Lighting
EVLIIVLED815W10A 10W, buck-boost LED driver
STEVAL-ILL055V1 11W, flyback LED driver
Fig. 2 – Main system evaluation boards
EVALIIVLED815W15 15W, flyback LED driver can be used as well; in this topology, the 60-100V low-voltage
STripFET F7 power MOSFETs series, ensures all solutions are very efficient and reliable. The STripFET F7 family features an extremely low Rdson, an optimized body diode( low Qrr) and intrinsic capacitance and a proper Crss / Css ratio.
Commercial Commercial and architectural lighting applications usually they require more than 20W, a high power factor, high levels of efficiency, cost-saving solutions, and the possibility of using more than one LED string— single or multiple strings— with remote monitoring.
In the case of a single string, the flyback topology is usually used. Working in constant-current primary-side regulation( PSR-CC) mode, ST ' s new HVLED003D, a flyback offline LED driver controller with embedded dimming capability( 0-10, PWM and Triac), can directly drive the single string without needing an optocoupler and secondary-side controller in the circuit.
For the main related switch, the MDmesh K5 power MOSFETs series is suggested, and we’ ve found the 800-900-950Vbr part numbers fit very well. The MDmesh K5 series suits hard switching topologies, and it has a very low Rdson, and small Qg and capacitance.
The multiple strings power supply architecture consists of a main power supply( usually a flyback) providing a constant DC bus voltage and subsequent multiple strings. This architecture can be seen in fig. 3.
Fig. 5 – Analog LED multiple strings management based on a controller
The suggested output diodes for buck and reverse buck topologies are the same as those reported in the single string case.
Ÿ To digitally manage the strings with reverse buck topology( fig. 6) jointly to PM88 or TD35 gate drivers, ST offers the STLUX, a new series of dedicated digital lighting controllers, as well as the STM32 high-performance microcontrollers. The power MOSFETs are the same as those shown in the fig. 5 case, and the output diodes in this case are the same as those used in both figures 4 and 5 cases.
Fig. 3 – LED multiple strings power supply architecture
ST’ s offline LED controller HVLED001 / A with constant-voltage primary-side regulation( PSR-CV) with dimming capability( 0-10, PWM) is available for the flyback. PSR-CV means doesn’ t need to use an optocoupler and secondary-side controller in the circuit. Power MOSFETs, output diodes and clamping net used for this flyback are the same of the ones described in the single string approach. The subsequent multiple strings can be managed using analog or digital means:
Fig. 6 – Digital LED multiple strings management
A wide offering of system evaluation boards for commercial single and multiple strings are available, and some of these are shown in fig. 7.
STEVAL-ILL070V2 / V3 35W, analog single-string LED driver
STEVAL-ILL074V1 / V2 60W, analog power supply for LED driving
Fig. 4 – Analog LED multiple strings management based on a converter
The new HVLED0002 current mode LED controller based on a fixed off-time( FOT) algorithm for reverse buck topology( fig. 5)
STEVAL-ILL077V1 60W, digital multiple-string LED driver
STEVAL-ILL054V2 18V-4A, buck LED driver converter
Fig. 7 – Main system evaluation boards for commercial applications
ELE Times | 54 | March, 2017