ST’s Extensive Selection for LED General Lighting

Luigi Galioto, Technical Marketing, Central LABs, STMicroelectronics

The analysts forecast that the LED General Lighting segment market from 2015-2020 will grow at a CAGR of 25% for Residential, of 29% for Commercial and of 16.9% for Street lighting. This growth is based on two main factors. The first factor is the reality that some of the largest countries have already become more energy conscious and have introduced regulations to phase out incandescent lamps in favor of more energy-efficient light sources such as LEDs. The second factor is related to the rapid urbanization taking place in emerging economies, which has resulted in a drastic increase in the number of households that require energy-efficient lighting sources as well as the need to improve urban infrastructure. Relevant to this analysis is ST’s broad offering for residential, commercial and street lighting LED applications.

STMicroelectronics’ offering: STMicroelectronics covers the entire range for LED general lighting applications with a wide portfolio including dedicated and suitable products.

Depending on the application, whether residential, commercial or street lighting, we’ll introduce ST’s products, platforms, and evaluation boards for the most commonly used architectures/circuits. We dedicate a separate section to the eDesign Suite, ST’s popular software tool for power management applications including LED lighting.

The market requirements for LED efficacy and driver ICs are constantly evolving. Residential lighting applications need high integration levels, high efficiency, high power factor (HPF), long lifetimes, and dimming capabilities as well as a low system cost and component count.

ST offers a wide portfolio of highly integrated offline converters up to 15W (each IC includes a power MOSFET combined with control and protection circuitry on a single chip) working with a high breakdown voltage of 800 V able to manage the main used topologies in the market—buck, buck-boost and flyback. Among these, dedicated offline LED driver converters such as the HVLED805, HVLED807PF, and HVLED815PF, work with a high PF and in constant-current/constant-voltage mode primary-side regulation (PSR-CC/CV), as illustrated in figure 1, while reducing costs by avoiding the need for a secondary side regulation IC and opto-coupler in the circuit.

Fig. 1 – HPF flyback with PSR-CV/CC

For flyback topologies, the STRVS repetitive overvoltage protections and STTH ultrafast diodes (with a pn from 600V to 1200V) are suggested for the clamping circuit; the STPS Schottky diodes and FERD field effect rectifiers fit very well for output rectification. The low leakage current of STRVS, the low VF/IR of the output diodes, and the best VF/trr tradeoff of STTH, guarantee reliability and efficiency to the flyback.