AC-DC power supply makers are introducing constant-current models for lighting manufacturers moving into the LED illumination market.
High efficiency is particularly important because maximum luminair dissipation is restricted by law in many parts of the world.
Inside and out
TDK-Lambda has developed a range of supplies with an output efficiency of 82% for both indoor and outdoor lighting.
The 12W LDC12 series (LDV12 is a voltage output variant) is IP66-rated and accepts universal AC inputs.
Constant current is either 350mA, the de-facto standard set by Lumileds’ original 1W Luxeon Star, or 700mA.
These PSUs are convection cooled, operating between -10e_SDgrC and +60e_SDgrC without derating, and guaranteed to start at -20e_SDgrC.
Standard features include short-circuit, overload and over-voltage protection. Over-voltage protection is particularly important in constant-current supplies to avoid self-destruction should the LED string become open circuit.
The units measure 90×34.5x21mm and are mounted in a vibration and shock resilient case.
All models have a mean time between failures of over 700,000 hours and a calculated capacitor life of up to 10 years. Warranty is three years.
On the open-frame side, Taiwanese PSU maker Mean Well has developed a range of LED PSUs for low-cost and built-in installations.
The 45W PLP-45 series models measure 102x51x31mm and have 90-264Vac inputs and simplified single stage active power factor correction (PFC).
“They can comply with EN61000-3-2 Class C (harmonic current) and PF>0.9 when output loading is higher than 75% to fulfil the general requirement of lighting fixtures,” says Mean Well.
Efficiency is up to 89% and free air convection is sufficient for full load operation between -30e_SDgrC and +70e_SDgrC.
Output current can be adjusted from 75% to 100% with a pot, and standard functions include short-circuit, overload and over-voltage protection.
Mean Well also makes sealed supplies, and is currently working on an IP67 (IP65 with internal potentiometer) convection-cooled series for streetlights.
Dubbed HLG, these have universal inputs, power factor correction and offer up to 94% efficiency.
It has already released the 240W HLG240H.