Long-life outdoor LED lighting drive power supply design

Outdoor lighting, especially street lights and tunnel lights, are difficult to repair and costly. Therefore, LED drive power requires not only high reliability and high protection level for these applications, but also requires a long service life, so that the lamps can at least run 5 year. This article describes how to ensure long life of LED driver power supplies.

LED drivers are made up of hundreds of components such as semiconductors, capacitors, potting compounds, PCBs, magnetic devices, etc. Electrolytic capacitors are considered to be the weakest link.       

Therefore, when calculating the life of the LED driver, we should find the one with the shortest life in capacitors A, B, and C.

1. Choose a long-life capacitor to make sure L0 is good enough. Utech's power supply is 10,000-12,000 hours @105 °C life NCC and Rubycon brand. The long-life, high-quality Japanese capacitors are used to maintain good performance in extremely cold environments, and maintain good performance even at -40 °C.

2. High efficiency and good thermal conductivity. When the temperature is lowered by 10 ° C, the life of the capacitor is increased by 2 times. Reducing the power consumption of the entire LED driver requires less heat. Assuming the same power loss, it is important to dissipate heat through the air or the luminaire. Most of the heat is conducted through the potting compound and the casing, which is why the Utech LED driver uses a high thermal conductivity rubber and a thick aluminum casing.

3. Ripple current. Ripple current is always ignored when people talk about life, but it plays a key role in the calculation. When we check the specifications of a capacitor, we see a lifetime of 10,000 hours @105 °C with the specified ripple current. The larger the ripple current, the more heat the capacitor itself generates. Therefore, if the ripple current is large, the internal temperature of the capacitor will be much higher than the case temperature, and the lifetime will also decrease. Compared to competitors, Ute uses larger capacitors to achieve lower current ripple. This is also why the life of the Utech LED driver can reach 100,000 hours at 75 °C.

After learning how to design a long-life LED driver, we need to know how to use it. This is a typical life and shell temperature curve, from which we can calculate the life of the power supply at different shell temperatures.

In summary, designing a long-life LED driver is not that simple. The high-quality components and the outstanding design of experienced engineers are key factors in achieving this goal.