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Effect of Ripple on LED Lights

Copy of an article from TCI Group Italy


The continuous research and development of cutting edge solutions leads TCI to provide the ultimate technology to satisfy the current market requests and to foresee the future ones.
RIPPLE FREE is an example of how TCI always aims at providing qualitative excellent products.  TCI LED drivers are provided with a sophisticated multistage circuit to supply the LEDs with a perfect current (a line), without any excess (Figure1).

RIPPLE is the width of the LED drivers’ output current sinusoidal wave. hen powered by RIPPLE FREE LED DRIVERS the LEDs can reach the maximum performance and light efficiency, with the minimum heat dissipation.
TCI RIPPLE FREE LED DRIVERS ensure the lowest level of light flickering.

In both the cases of bright or low light, it is assumed that the flicker is acceptable because it is largely imperceptible. However, surveys have linked the flicker to health problems.  So, even though flicker at these frequencies may not be visible to the naked eye, there is evidence that the human brain can detect light flicker frequencies up to 200Hz (the  LED drivers output ripple is 100Hz).
Potential problems include headaches, eye strain, impaired visual performance or, in extreme cases, epileptic seizure.
It is important to consider the flicker effects during video-cameras recording, where the images are cut with several black lines and it is not possible to properly shoot.

A low LED driver current ripple is 5% more efficient in terms of light output.    In addition to the effects, HIGH RIPPLE current will negatively affect the LED, the LED driver life time, and the efficiency of the system in general.
An example is 700 mA output current average, 40% ripple is 560mA current ripple pk-pk. The output current will swing between 980 mA and 420 mA with the average at 700 mA.

Ripple current can increase the LED driver power dissipation that leads to  increased junction temperatures. Figure 2 shows the major impact on the LED life of a higher temperature, because in the “A” area the LED is oversupplied while in the “B” area the LED is undersupplied. The temperature excess of the “A” zone cannot be balanced in the “B” zone and consequently the LED system (LED+heatsink+lamp) has a higher temperature compared to the RIPPLE FREE solution.

The third main consequence of this effect is the lower light efficiency of the LEDs, as LEDs are less efficient when their temperature increases.  TCI RIPPLE FREE LED DRIVERS ensure the minimum temperature of the designed LED system.
It is also important to know that the future development of the LED technology will bring to even more efficient LEDs but the increase of efficiency (the internal die inside the LED reduces its resistance) will make the  HIGH RIPPLE LED drivers performance worse.
In Figure 3 “C” and “D” areas show the possible increase of current ripple due to an increase of LEDs efficiency.

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Phone.  0800 695 444 or 09-475 6747
sales@nzlightingltd.co.nz
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