LED filament lamp drive scheme

Update:24 Apr 2018

First, resistance-capacity buck: small size, low cost, […]

First, resistance-capacity buck: small size, low cost, voltage change is not constant current, there are strobe, easy to over EMC, lightning surge resistance is poor, difficult to pass the export certification, in the poor protection of the power grid is vulnerable to damage.

Second, linear constant current: small size, low cost, voltage fluctuations, small range constant current, 30cm no flicker, easy EMC, heat, in the grid voltage fluctuations in areas prone to damage due to heat.

Third, the IC constant current: a larger number of components, the cost is slightly higher, the voltage fluctuation constant current accuracy, no flicker, over EMC, the most comprehensive protection.

Fifth, LED filament lamp and filament drive standardization recommendations

At present, the specifications of LED filament lamps are not unified, and some filaments are 75V, 10mA; some are 65V, 10mA; in bubble sealing, some are 2 strings, and some are 1 string, which is not convenient for ordering and stocking of filaments and drivers.

Comprehensive resistance and IC constant current characteristics of the two programs. It is recommended that you use a 75V, 10mA filament, and make 2 strings when sealing.

On the one hand, this LED filament lamp has a low current consumption, low power consumption, high power efficiency, and high overall lamp efficiency. On the other hand, it is also convenient for standardization and inventory production. The latter, in particular, can solve the current unfavorable situation of the filament drive due to the large number of models, the inability to prepare inventory, and the long delivery period.

How to set the LED filament?

The reason for the LED junction temperature is that the added electrical energy is not converted into light energy, but is converted into heat energy. The light efficiency of LED is only 100 lm/W at present, its electro-optical conversion efficiency is only about 20 – 30%. In other words, about 70% of the electrical energy becomes thermal energy.

LED junction temperature is due to two factors:

1. Internally generated photons cannot be completely emitted outside the chip and eventually converted into heat. This part is mainly because this is called the external quantum efficiency of only about 30%, and most of them are converted into heat.

2. The internal quantum efficiency is not high, that is, when electrons and holes recombine, photons cannot be generated in 100%, which is generally referred to as “current leakage” and the recombination rate of carriers in the PN region is reduced. The leakage current multiplied by the voltage is the power of this part, which is converted into heat energy, but this part does not occupy the main component, because the internal photon efficiency is now close to 90%.


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