Do SMD LEDs need less current than THT LEDs?
Do SMD LEDs need less current than THT LEDs?
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When working on a recent project, I chose 1206 red SMD LEDs due to the specific request for SMD variants. These LEDs were connected to an 74HC595 shift register, and I initially calculated the current for each LED using a 680 Ω series resistor, leading to approximately 4 mA of current.
However, a colleague suggested using much higher resistors, around 10k, because SMD LEDs are "laser-like" compared to typical diffused THT LEDs, focusing the beam and having a smaller radiant angle. Considering that the control panel didn’t need to light up a room or cause discomfort, should higher resistor values indeed be used? What is the typical recommended current for SMD LEDs in non-illuminative scenarios?
LED COB and LED SMD: A Few Things You Need to Know
Characteristics of SMD LEDs
SMD LEDs are widely favored for their ability to be directly applied to circuit board surfaces, reducing the need for additional leads and materials. Offering a wide luminous angle between 120-160 degrees, they allow for even illumination and enhanced visual effects. Additionally, SMD LEDs function at lower voltages and currents, consuming less energy and generating minimal heat. These aspects contribute to their long lifespan and stability. The inclusion of three single-color LED units within each SMD LED allows for multi-color displays, further extending their versatility.
Understanding COB LEDs
COB LEDs represent a more advanced form of LED technology. They integrate multiple LED chips onto an insulating layer and an aluminum heat sink, available in different shapes like round, square, or star. This compact packaging facilitates a high concentration of light output per square inch, simplifying circuit design, reducing energy consumption, and lowering failure risks. COB LEDs are notable for their superior heat dissipation and low operating temperatures, leading to extended lifespans and stability.
Characteristics of COB LEDs
The dense arrangement of chips in COB LEDs enables them to attain impressive brightness levels. They require only one circuit and two contacts to drive the entire array, which streamlines circuit design and enhances reliability. Unlike traditional LEDs, COB LEDs lack leads, phosphorescent layers, or lenses, which enhance light efficiency while reducing light loss. The robust thermal properties of the substrate and heat sink ensure effective heat conduction, enabling low-temperature operation and prolonged LED life.
COB LEDs vs. SMD LEDs: A Comparison
1. Brightness
COB LEDs are characterized by higher light output due to their tightly packed chips, making them ideal for high-brightness applications like spotlights and downlights. While SMD LEDs may not achieve the same brightness in a single chip, they offer more uniform and soft lighting, suitable for wider illumination needs such as strips and bulbs.
2. Energy Efficiency
Generally, SMD LEDs are more energy-efficient than COB LEDs because they produce more lumens per watt. This efficiency makes them a cost-effective choice over time. Despite their higher lumens per square inch, COB LEDs do not match the energy efficiency of SMD LEDs but offer significant brightness advantages in compact applications.
3. Color
SMD LEDs offer the ability to produce various colors due to their built-in single-color LED units. They deliver versatile lighting effects by adjusting the brightness of each unit. Conversely, COB LEDs are typically limited to emitting light of a single color or temperature, making them suitable for applications needing consistent color output.
4. Heat Dissipation
COB LEDs are designed for efficient heat dissipation thanks to their close-packed chip arrangement on thermally conductive substrates. This feature ensures durability and stability, particularly for prolonged use in high-temperature conditions. While SMD LEDs are also efficient in dissipating heat, their traditional packaging results in a slightly higher heat output compared to COB LEDs.
5. Cost
The cost dynamics between COB and SMD LEDs are complex. COB LEDs, with their simplified production processes, tend to be cost-effective, though they require superior materials and heat management solutions. On the other hand, SMD LEDs involve complex production with separate substrates, phosphor layers, and circuit designs. However, advancements in automation have made SMD LEDs more affordable in certain scenarios.
In conclusion, the choice between COB and SMD LEDs relies on the specific demands of the application. COB LEDs are excellent for brightness and cost-efficiency, while SMD LEDs shine in uniformity, energy efficiency, and color versatility.
6. Environmental Footprint
Both COB and SMD LEDs make a significant environmental impact by consuming less energy and reducing carbon emissions compared to traditional bulbs. Their longer lifespan lessens waste production, promoting sustainability. Choosing these LEDs is a step toward a brighter, eco-friendly future.
Why COB LEDs Require Better Substrate Heat Dissipation
COB LEDs generate more heat due to their dense chip integration, needing efficient heat dissipation for optimal performance. The aluminum substrate in COB LEDs offers superior thermal conductivity, effectively transferring heat to maintain operation at lower temperatures. Additionally, aluminum substrates have a low thermal expansion coefficient, preventing dimensional changes and ensuring stable operation. Using aluminum substrates in COB LEDs allows them to handle higher currents, enhancing their applicability in high-demand scenarios.
The Advantage of Aluminum Substrate in COB LEDs
The superior thermal and dimensional stability properties of aluminum substrates make them ideal for advanced LED applications. They allow COB LEDs to maintain lower temperatures and handle higher currents, crucial for extended operation in challenging environments.
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COB LEDs and SMD LEDs in Luminaire Manufacturing Applications
1. Applications of SMD LEDs
SMD LEDs are preferred for wide-angle lighting applications like strips, panels, and bulbs due to their even illumination capabilities and color versatility. They are commonly used in architectural lighting and dynamic lighting effects.
2. Applications of COB LEDs
COB LEDs are ideal for high-brightness and concentrated lighting such as spotlights, downlights, and industrial lighting. Their efficient heat dissipation and extended lifespans make them suitable for harsh environments requiring long operational hours.
Troubleshooting COB LEDs and SMD LEDs
1. Power-Up Test
Use a power supply or battery to check if the LEDs light up properly. Failure to emit light might indicate damage or poor contact.
2. Multimeter Test
A multimeter can measure the conduction voltage and resistance of the LEDs. Abnormal values could signal shorts or open circuits in the lamp bead.
3. Visual Inspection
Examine the LEDs for any physical damage such as cracks or discoloration, which may result from overheating or mechanical stress.
For precise assessments, consider using professional testing instruments like spectrometers.
Replacing Bad COB LEDs or SMD LEDs in LED Products
1. Removal of Bad LEDs
Use a soldering iron or hot air gun to remove faulty LEDs from the board, taking care not to damage other components.
2. Cleaning and Preparing the Board
Clean off excess solder to prepare for mounting new LEDs.
3. Replacement of LEDs
Install new LEDs, ensuring correct polarity. Solder them firmly in place, particularly for models with intermediate heat sink pads.
4. Soldering
Heat the connections evenly to ensure solid solder joints.
5. Testing
Verify that the new LEDs light up correctly. Troubleshoot as needed to resolve any remaining issues.
If you are inexperienced or lack the necessary tools, consider replacing the entire board instead.
Conclusion
Understanding the differences and strengths of COB and SMD LEDs can significantly impact your lighting solutions. Each type has its place depending on the specific needs of the application.
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As a professional LED luminaire manufacturer, Vorlane provides expertise and high-quality products to meet your lighting requirements. Please reach out for assistance or more information about COB and SMD LEDs. Together, we can illuminate a brighter future with advanced LED technology.