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All colleagues unite and focus their efforts to write a new chapter of developmentHow can the issue of LED driver power supplies being prone to failure be addressed?
所属分类： Industry News
发布时间：2020-05-30
To address
LED driver power supply Addressing issues such as high failure rates and difficult maintenance, and based on an analysis of the LED luminescence mechanism and power‑supply requirements combined with current practical applications, we propose adopting a low‑voltage DC power‑supply scheme for LED road lighting. This DC‑based approach not only reduces the failure rate of LED driver circuits but also mitigates safety risks in road illumination, while simultaneously facilitating future electric‑vehicle charging infrastructure.
With the continuous advancement of light-emitting diode (LED) technology, LED lighting has gradually expanded from indoor to outdoor applications. However, its adoption in road lighting has been slow, owing to factors such as high power requirements and harsh operating conditions. After a period of field monitoring, some high‑power LED streetlights have begun to experience failures. Analysis of these failures reveals that damaged LED driver power supplies account for as much as 90% of the issues. Although LED streetlights are theoretically rated for a service life of up to 50,000 hours (approximately 13.7 years), their driver circuits have a significantly shorter lifespan—around 12,000 hours (about 3 years). Consequently, the driver power supply has become the primary bottleneck limiting the overall service life of LED streetlights. Moreover, because LED drivers must be matched to specific LED chips and no unified standard exists, manufacturers produce drivers with non‑standardized output interfaces and widely varying quality levels. This inconsistency complicates maintenance and increases the cost of replacing faulty drivers.
LED driver power supplies have been brought under the scope of China’s mandatory 3C certification. Power supply issues have become a key factor hindering the widespread adoption and application of LED luminaires. Only by addressing these power‑supply challenges can the full potential of LED lighting in road illumination be realized.
I. Power Supply Requirements for LED Chips
To address LED power supply issues, we need to understand the fundamental operating principles of LED chips and their power requirements.
Currently, LED luminaires used in road lighting feature an integrated light-emitting structure that comprises both the LED light source and the power supply. The LED light source consists of a specific number of high‑power LED chips connected in a series‑parallel configuration to form a single, unified light‑emitting module. A single LED is essentially a diode: when a forward voltage is applied across its terminals, it triggers current flow through the P‑N junction, causing the LED to emit light. The nominal voltage of an individual LED is 3.4 V ± 0.2 V (with an actual operating voltage typically ranging from about 2.8 to 3.8 V). The operating current is related to the LED’s power and brightness; LEDs of different power ratings require different currents. Generally speaking, the higher the power and the greater the current, the more light the LED produces. In road lighting applications, high‑power 1‑W LED chips have a nominal current of 350 mA.
Through a structural analysis of commercially available LED luminaires, it is evident that each luminaire comprises a series connection of a specific number of LED chips, yielding an LED string with a operating voltage of 40.8 V ± 2.4 V. These LED strings are then connected in parallel to form an LED luminaire with an operating current of 3.5 A. Based on power-loss calculations, the luminaire requires a power supply of 48 V/3.5 A.
II. LED Driver Power Supply
The existing street‑light power supply operates on 220 V AC and must undergo three steps—step-down transformation, rectification, and current regulation—to deliver a stable low‑voltage DC power source to the LED luminaires. First, the 220 V AC is stepped down to 48 V AC; next, this low‑voltage AC is converted into low‑voltage DC via a bridge rectifier; finally, a high‑efficiency switching regulator further converts it into a constant‑current source, providing a steady current to the LED chips.
To reduce chip failure rates, most manufacturers adopt a series‑parallel configuration with fewer strings and more parallel paths. Current LED luminaires typically operate at 48 V, and each luminaire may have slightly different voltage and current requirements. In practical applications, the appropriate driver should be selected based on the luminaire’s overall voltage and current specifications.
III. Power Supply Fault Analysis
Because the LED chips and the power supply are both housed within the luminaire’s confined space, achieving moisture‑ and water‑proofing requires sealing the power supply—yet this also creates significant thermal‑management challenges. In summer, the temperature of the LED light source can exceed 70°C. Operating under such high‑temperature conditions drastically shortens the lifespan of the LED driver. Moreover, the complete seal prevents on‑site replacement of failed components; only a full unit replacement is possible, making repairs both cumbersome and costly. This is one of the key reasons why end‑users have shown limited enthusiasm for adopting LED street lighting.
IV. DC Power Supply Mode
Since the heat‑dissipation challenges of driver power supplies distributed within individual street‑light fixtures remain unresolved, why not relocate these decentralized drivers from the luminaires to the ground, consolidating them in ground‑mounted transformers or switchgear for centralized management? Ground‑based DC transformers not only offer higher conversion efficiency and better temperature control but also simplify maintenance. Once LED streetlights adopt a low‑voltage DC power supply system, this will enhance electrical safety while also paving the way for future electric‑vehicle charging infrastructure.
V. Technical Approach
Existing LED streetlights can make maximum use of the current infrastructure. By adding step-down and rectification equipment at the existing transformer’s output end (or at the switchgear), a 48 V low‑voltage DC supply is generated through voltage transformation, rectification, and filtering, and this power is then delivered to the LED streetlights via the existing cables (e.g., four 25 mm² conductors and one 16 mm² conductor).
For newly installed or retrofitted LED streetlights, the design of the power distribution and control circuitry can be further optimized. By employing high‑power rectifiers to centrally convert 220 V/380 V AC into a standardized DC supply, low‑voltage DC power can be directly delivered to the LED luminaires. Consequently, the conventional driver circuits can be eliminated, with the streetlight’s power distribution and control system providing the DC supply directly. This allows for a more streamlined structural design and a corresponding increase in reliability.
VI. Advantages of DC Power Supply
1. Address the current issue of the relatively short service life of the driver power supplies in LED street lighting fixtures.
2. Enhance the overall luminous efficacy of LED luminaires (currently, both in China and in Europe and North America, the luminous efficacy of the entire luminaire—including the light source and power supply—is used as a key metric for evaluating energy efficiency); meanwhile, implement centralized step-down rectification to reduce system energy consumption.
3. Reduce safety risks during the operation of street lighting systems (in China, AC voltages below 50 V are considered safe, and in practical applications, DC voltage is safer than AC).
4. By eliminating the driver power supply in LED streetlights, the number of potential failure points is significantly reduced, making maintenance more convenient and substantially lowering installation costs.
5. The DC power supplies installed along both sides of the road can facilitate charging for electric vehicles and battery-powered scooters.