Current Page
  1. Home
  2. Lighting Technology Reference

* LED Lighting Life Span depends on Capacitor Type(Patented!!) *

* Solid Capacitor LED Lighting Solution(US Patented, Field Failure : 0.2%) *

SCPS(Solid Capacitor Power technology) can gureetee
semi-permanent life time & reliability under harsh condition like
cold storage warehouse with high humidity and low temperature.
Its solid capacitor and semiconductor based linear operation circuit differenciates that of
SMPS type LED lighting which uses liquid capacitor and high speed switching(500kHz).


In addition, Its 240Hz constant current driving frequency fits into
US DOE(Department of Energy) requirement(above 150Hz) and expect Apparent Brightness Increase(Broca-Sultzer effect).

1. SMPS LED Lighting Feature


SMPS(Switching Mode Power Supply) is, so far, one of the far advanced power technology
with relatively small form factor, thanks to high speed switching, but as a side effect,
it generates electromagnetic waves and requires protection components such as EMI filter to minimize to noise.

In addition to that, it also utilizes liquid capacitor which is blamed for
73% of power failure. Liquid capacitor itself only has 1,000hr life span and it is
highly dependant on ambient temperature regardless of either hot or cold.


[SMPS form factor and Liquid Capacitor in red circle]

2. AC Direct LED Lighting Feature


Unlike SMPS Type, AC Direct doesn't utilize neither liquid capacitor nor
high speed switching which theoretically, eliminate power failure causes but, as its nature,
It has 120Hz driving frequency in case of AC main 60Hz and also low LED usage which causes
low light output. In general, lighting with AC Direct Driver shows only about
75% power conversion efficiency similar to that of SMPS type under 30W.

[US DOE AC Direct Driving Pattern]

3. Technology Basis


A. Stroboscopic Effect by Driving Frequency and Percent Flicker

The stroboscopic effect is a visual phenomenon caused by aliasing that
occurs when continuous motion is represented by a series of short or instantaneous light.

[Stroboscopic Effect on synchronization with flash light]

Flicker parameter designed by LRC(Lighting Research Center in US) shows that
higher driving frequency and lower percent flicker increases acceptability of lighting.
Traditional lighting such as High Pressure Sodium or Metal Halide lamp reside in somewhat unacceptable region.

* Reference: Flicker Parameters for Reducing Stroboscopic Effects from
from Solid-state Lighting Systems May 2012 Lighting Research Center

B. Improving Flicker Index

LED lighting quality can be measured by flicker.
Japan recommend no flicker for indoor lighting or above 500Hz and
DOE recommend to keep flicker index below driving frequency*0.001.
But it doesn't cover real problem like noise flicker from SMPS.


C. LED Usage and lighting efficacy

Main issue with AC Direct LED lighting resides in low efficacy due to
low LED usage(=On/(On+Off) as in its nature. For instance, higher driving voltage
lowers LED usage and lower driving voltage drops power efficiency. Efficacy on LED package
drops about 20~40% as input current increase twice.


D. Apparent Brightness Increase(Broca-Sulzer Effect)

Research on apparent brightness dates early 1900 and.
Recent study by Tianjin University Key Laboratory of Opto-electronics Information and
Technical Science shows that when the average intensities are the same, the apparent brightness of the
PWM dimming LED is higher than that of the continuous dimming LED.