We all know that led is driven by current to stimulate the phosphor and emit light, and its voltage is a passive value. In other words, to measure the parameters of LED, the current is the active parameter, and the voltage is the passive parameter. And LED used in the field of lighting, brightness requirements are very high, so the accuracy of the current is also very high. Based on the above discussion, the following discusses how much damage ripple voltage has on LED.
For example, 3523.8 V LED is rated.
Its current voltage curve: (provided by Taiwan Yiguang)
According to the parameters used by most customers, 12 in 12 series, we will give 18 Ma ~ 20 mA, so the voltage range is very narrow, basically 3.1 V ~ 3.2 v.
If we calculate according to the theory of 20 mA, 3.2 V, 12 in 12 series is 38.4 V, 240 ma. Assuming that the current ripple is 5%, the maximum floating voltage is 1.92v, and the single LED increases by 0.16v, that is, a single LED is 3.36v, the current is 24Ma, the current of 10% is 3.52v, the current is 25mA, and the current of 20% is 3.84v, and the current is greater than 45mA.
The current of the above data can not be detected by ordinary instruments, but led can be “felt”. So where is the change of voltage and current at such high frequency? The answer is that LEDs generate extra heat!
Interested friends can use the same set of LED load, different output ripple voltage power supply to test, LED temperature is not the same. In addition, sometimes when the LED light is just installed, it will be found that there are led dead, many of which are caused by the high ripple voltage.
Then I personally understand the harm as follows:
1. Produce high temperature, reduce LED life.
2. The high frequency current impact will cause led failure in a short time. It directly affects the life of LED.
The above two points are one of the main reasons why LED light is so beautiful. As early as three years ago, almost no one discussed this problem. At the same time, the technology level of LED is obviously not as good as now. In today’s technology field, ripple is more and more recognized and cared about.
Another point is that for the drive power supply without electrolytic capacitor, the bottleneck is ripple. If the ripple is not handled below 5%, no electrolytic capacitor in the LED lighting field is always a dream!