Lightweight and efficient LED power supply design uses 48V power module

LED 技术过去 10 年发展迅猛，在许多情况下取代了 LCD 技术。我们最熟悉的变化是，我们的消费类电视已逐渐变得更薄、更轻、更大、更节能。而用于数字标牌的外部照明显示屏取得的发展更显著。这些极具魅力的绚丽商业显示屏使较小格式的消费单元相形见绌，它们消耗更多的电源。因此，整个系统架构和供电网络是设计这些系统的重要组成部分。

Compared with liquid crystal display (LCD) technology, direct-view LED video wall technology has become a popular choice for large displays due to its excellent brightness and color uniformity. However, large video displays present a daunting power supply design challenge: How best to develop an efficient solution that reduces energy consumption, minimizes heat generation, is easily scalable, and is secure? Heat generation is a big problem with light-emitting diodes (LEDs). More heat can lead to excessive temperatures, which can quickly reduce the brilliance and lifespan of the LED.

One factor that causes LED panels to heat up is the heat loss in converting and distributing power within the video wall: losses in the power converters and resistive copper losses in the wiring and printed circuit boards. So, what's the solution? When designing high-power LED applications, evaluating the pros and cons of different zoning options can help determine the best option.

In addition to being brighter, direct-view LED displays are also more energy-efficient than LED-backlit LCD displays because they can produce more light output using less energy (i.e., "useful power"). Still, they generate a lot of "wasted power" in the form of heat. This may seem surprising since LEDs are often cool to the touch. They are cool to the touch because they typically do not generate heat in the form of infrared radiation, which can be felt by touch. In fact, up to 85% of the energy consumed is dissipated as heat, so large LED arrays will require far more power than can be converted into light.

For large LED panels, LED power consumption can become considerable. For example, the "Fremont Street Experience" display in Las Vegas consumes 2.2MW (megawatts) of power when it is at its brightest, and even more energy is needed during the day to protect against the effects of Nevada's intense sunlight. . Even small displays have a lot of LEDs and consume a lot of power: for example, a leading manufacturer's display module contains an 80 x 80 array, or a total of 6,400 LEDs, and requires 300W of power (5V, 60A).

Therefore, when designing LED power supplies, maximizing efficiency is critical.

Large panel video LED displays are composed of multiple smaller panels and need to be powered by a common bus voltage. Distributing alternating current (AC) directly to each panel and converting the AC to DC on each panel would be cost-prohibitive, cumbersome, and generally unsafe. Instead, it is recommended to use a single large AC-DC converter stage to provide an isolated low-voltage bus voltage to power each individual panel. For large panels, the distance from the large AC-DC power supply to the LED driver can be several meters, which creates challenges as power levels increase, making it an important design consideration.

Heat is the main enemy of LEDs, and the inherent inefficiencies in the power supply design only make this situation worse. Excessively high temperatures will shorten the life of the LED and cause fading. Worse, light output decreases as junction temperature increases. An efficient power supply system for LEDs must pay attention to each individual component to avoid the development of localized hot spots, which not only accelerates the failure of the LED but also reduces its brightness throughout its lifetime. This is especially important in video walls where both light quality and color uniformity are important.

Transmitting power from the power supply to the LED array through resistive copper wires causes power loss in the form of heat, known as distribution losses. Distribution losses in current (I) are proportional to the square of the current, expressed as P = I2R, where R is the resistance of the wire, busbar, or PCB trace; reducing this resistance requires reducing the current or reducing the wire impedance.

To reduce the current while supplying the same total amount of power to the load, an increase in voltage is required (P = VI). For example, doubling the voltage from 24V to 48V can reduce the current by 50%, which in turn can reduce distribution losses by 75%.

To achieve the same effect by reducing wire resistance would require increasing the cross-sectional area of ​​the conductor by a factor of 4, which not only adds weight and cost, but is also impractical.

Another way to reduce power consumption is to minimize the number of conversion stages. For example, eliminating the conversion stage can increase system efficiency by 5 to 10 percent and, depending on the power level, reduce the heat generated in the system. To eliminate the conversion stage, designers need to select components that provide high buck conversion rates without compromising efficiency.

The most common bus voltages for powering LED panels have always been 24V and 12V. It removes potentially lethal voltages from the panels compared to AC power distribution, and they comply with the Safety Extra Low Voltage (SELV) "safe" voltage standards for low voltage power supplies.

However, a better option than 12V or 24V is to double the intermediate voltage to 48V. 48V is lower than 60V, so it still meets SELV safety standards, even if a 20% overvoltage protection margin is included. This cuts the current in half for a given power level and reduces cabling cost and weight compared to a 24V system, which equates to even more savings!

You can reduce distribution losses by 75% by increasing the bus voltage to 48V, which significantly reduces heat generation. Lower operating temperature improves system reliability, and lower current reduces LED panel thickness. In addition, using higher voltages with lower distribution losses also increases the efficiency and reliability of the video wall, which helps reduce lifetime operating costs for the end user.

Power modules are the most efficient way to create a compact power supply network. Modular design always provides smaller and lighter solutions for power system design. Power modules package a large number of components into a unified flat package. The flat design improves thermal performance and makes designs more convenient and scalable. Vicor power modules are the world's highest power density modules and are highly efficient, lightweight and compact. When hanging heavy commercial LED signs, weight and high performance are extremely important.

The answer is simple. If we can break away from the accepted norms of using power systems and no longer rely on the 12V or 24V intermediate bus voltage, and only need to double the bus voltage to 48V, the advantages will be immediate and sustainable over the life of the equipment. continuous:

◆ Reduced heat generation/easier thermal management

◆ Reduce wiring/cost saving, smaller size and lighter weight

◆ LED has higher performance/higher display quality

◆ Longer panel life/higher reliability

◆ Higher power efficiency/lower power consumption

在设计大功率的大型 LED 显示屏时，使用 48V 母线会让一切变得不同。线缆重量将得到显著地改善。凭借模块化电源设计的优势，您将有机会降低长期功耗，实现更加明亮的 LED 并大幅减轻供电网络的重量。