It is apparent that many engineers are prone to be vexed about the following problem:

On the condition of the same light fixtures and the same wiring operations, some projects operate smoothly, whereas some, for example, the projects of street light LED driver application and non-isolated LED driver application are opposite. The light fixtures applied frequently suffer from the “inexplicable damage”.

Then why does this happen?

Today let’s talk about one of the common reasons—surge and residual voltage

Definition of Surge

The written definition of surge is any voltage peak that exceeds the corresponding stable one, which is to say, the transient voltage. It is divided into 2 types. One is external surge: the spike voltage generated by the abnormalities of lightning and AC network or the startup of high-power equipment surrounded; the other is internal surge: the spike voltage generated by the on-off of equipment. Generally speaking, the surge would be generated by both the lightning discharge and the on-off of electrical equipment, and it is an inevitable problem every time the electrical equipment works.

Where there’s electricity, there’s a surge

If the desirable input voltage waveform of stable mains is a silky smooth sine wave, with the existing input voltage waveform of surge voltage, there will be many spikes on the smooth waveform. The voltage of these spikes can reach thousands of volts, even tens of thousands of volts. If these were not dealt with, they would incur the electrical appliances to be broken down due to the over-high voltage.

Desirable voltage waveform—stable and smooth VS voltage waveform with surge—thorny and uneven

Definition of residual voltage

In order to eliminate the detriment of surge, we use the surge protector to absorb current, eliminating the relatively large spike voltage so as to render the voltage waveform return to a relatively stable state. At this time, the peak voltage at the input and output is the residual voltage. Just as an axe in the circuit, the surge protector cut the big thorns (lightning surge) into small ones (residual voltage). However, if the small thorn is “over-sized”, they might penetrate into some accessories as well, resulting in the damage of equipment.  

  Transient surge voltage (up to thousands of volts) turned to low residual voltage

Influence of the residual voltage of isolated and non-isolated LED drivers on light fixtures

In the design of isolated LED driver, the “electricity-magnet-electricity” conversion of input voltage is conducted via transformer, and the input is not directly connected to the loaded light fixture. Therefore, the surge and residual voltage has small impact on the light fixtures at the output, and the withstanding voltage of light fixture’s aluminum substrate reaching 1.5kV is sufficient for the safety application.

Whereas in the non-isolated circuit, the “electricity-electricity” conversion of the input and output is conducted via the rise and fall of voltage, and the input and output are directly connected to the loaded light fixture. The circuit is excessively sensitive to the surge due to its inferior inhibition ability, when the voltage in the power grid is instable, the non-isolated LED driver is inclined to directly generate more than 3kV residual voltage, leading to the broken down of the loaded light fixture’s aluminum substrate, chip and LEDs, and the light fixture would be burnt out subsequently.

That’s why the application effects are different on the condition of the same products and the same installation methods. The root cause is that the stability of power grids is different. 

Lifud patented technology—low residual voltage (<1.5kV) in the non-isolated circuit

When choosing the non-isolated solution with higher cost performance, the customers would be worried about the withstanding voltage of aluminum substrate, etc. In order to driven this anxiety away, Lifud innovative and patented technology of low residual voltage aims to optimize the circuit, enabling the ultra-low residual voltage in the non-isolated circuit so as to protect the light fixture from being broken down by the high voltage.   

From the first non-isolated low-power tube light LED driver to the first non-isolated high-power UFO highbay driver, Lifud is always customer-centric, continuously striving towards technology innovation and putting technology reformation into effect to solve the pain points in the market, and all is merely for its one vision: making energy more efficient and cleaner.   

Need driver, choose Lifud!