What Is A COB Downlight?

Struggling with lighting terms like COB? Choosing the wrong type can mean poor light and unhappy clients. Let me explain COB downlights to help you select the perfect light every time.

A COB (Chip-on-Board) downlight uses a technology where multiple small LED chips are packaged together as a single lighting module. This creates one powerful, uniform light source, unlike other LEDs that use multiple, separate light points. It’s known for its bright, focused beam.

Now that you know the basics, you are probably wondering how this technology actually compares to the standard downlights¹ you see everywhere. It's a valid question, as the differences directly impact the look and feel of a space. Both have their place, but knowing when to use each one is what separates a good lighting plan from a great one. Let's break down the key differences to see why this matters for your projects.

What is the difference between a COB downlight and a standard downlight?

Ever notice how some lights cast one sharp shadow, while others create softer, fuzzier edges? This small detail can completely change a room's mood. Understanding the difference gives you control.

The main difference is the light source. A COB downlight² has one large, single light source. A standard downlight, usually using SMD (Surface Mounted Device) technology, has many small, separate LED chips³. This changes the quality and direction of the light they produce.

To truly understand the impact on your projects, let's look closer at how they are built and how they perform. The technology inside the lamp is what determines the result you see in the room. I have seen many projects succeed or fail based on this single choice.

The Light Source Technology

The most fundamental difference is how the LED chips are arranged. A standard SMD downlight has numerous individual LED chips soldered onto a circuit board. When you look at it, you can see many little points of light. Think of it like a showerhead with lots of small nozzles. On the other hand, a COB downlight bonds many tiny chips directly onto a substrate to act as one large chip. It’s like having one powerful, single jet of water. This single-point source is what allows COB lights to mimic the classic look of a halogen lamp⁴, which many designers and clients still prefer for certain applications.

Light Quality and Appearance

This difference in the light source directly affects the quality of the light beam. Because COB acts as a single point, it creates a clean, controlled beam with a single, crisp shadow. This is perfect for accent lighting⁵—making a piece of art, a retail product, or an architectural feature pop. In contrast, the multiple light points of an SMD downlight create a wider, more diffused, and softer light. This is better for general ambient lighting⁶ where you want to illuminate a whole room evenly, like in an office or a kitchen, because it reduces harsh glare and multiple distracting shadows.

Common Applications

Based on these qualities, their applications are quite different. I always guide my clients based on the specific goal of the lighting.

What are the key components of a COB downlight?

Thinking a downlight is just a lamp in a casing? There's more to it, especially with COB technology. Overlooking key components can lead to early failure and wasted money on your projects.

A COB downlight has three critical parts: the COB LED chip itself, a robust heat sink⁷, and a reliable driver⁸. The chip makes the light, the heat sink keeps it from overheating, and the driver provides clean, stable power. The final quality depends on all three.

When you are sourcing these products, you are not just buying a light; you are buying a system where each part must work perfectly with the others. From my years of manufacturing, I can tell you that cutting corners on any of these components is a recipe for disaster. Let's dig into why each part is so important for performance and long life.

The COB Chip

This is the heart of the lamp. It’s where dozens or even hundreds of tiny LED chips are bonded together on a ceramic or aluminum base and covered with a layer of phosphor. This is what creates that bright, uniform light. However, this surface is very delicate. In my factory, we have strict rules for handling them. One careless touch on the yellow phosphor surface can damage the chip, leading to dark spots or an inconsistent color temperature in the final product. When you receive a shipment, a quick visual inspection of the chip surface can be a good first step for quality control.

The Heat Sink

This is probably the most critical component for a COB downlight's lifespan. Because all those LED chips are packed into a small area, they generate a lot of concentrated heat. If that heat isn't pulled away effectively, the chip will degrade quickly, lose brightness, and fail. A good COB downlight needs a thick, heavy aluminum body to act as a heat sink. In our iPHD products, I insist on using high-grade die-cast aluminum and a thermal paste with a conductivity of at least 2.0 W/mK. This small detail makes the difference between a lamp that lasts 50,000 hours and one that fails in its first year.

The Driver

The driver is the unsung hero. It's an external or internal power supply that converts the AC power from the wall into the low-voltage DC power the LED chip needs. A high-quality driver provides a constant, stable current, which prevents the light from flickering. It also protects the sensitive COB chip from power surges or fluctuations. A cheap, unstable driver is one of the most common points of failure in any LED product. It can cause the light to flicker, change color, or just stop working altogether.

Is COB better than LED?

Is COB the best, or just another type of LED? This question is common and causes a lot of confusion. This confusion can make you hesitate, possibly missing the best solution for your lighting project.

Let's clear this up: COB is not "better" than LED, because COB is a type of LED technology. The real question is whether COB is a better choice than other LED types, like SMD, for your specific need. Neither is better overall; their strengths shine in different situations.

Choosing the right type of LED is about matching the technology to the goal. You wouldn't use a hammer to turn a screw. In the same way, you have to pick the right light for the job. Thinking about it this way makes the decision much simpler and ensures you get the results you want. Let's explore where each technology excels so you can choose confidently.

When COB is the Perfect Choice

COB technology truly shines when you need a lot of light from a small fixture. This is called high lumen density⁹. It’s perfect for applications that require a powerful, punchy beam of light. Think about track lights in a retail store highlighting a new product, spotlights in an art gallery, or downlights installed in a hotel lobby with a very high ceiling. The intense, focused beam can travel a long distance and create strong contrast, which adds drama and directs attention. From a design perspective, the compact nature of the COB chip also allows for smaller, sleeker, and more minimalist fixture designs.

When SMD is the Star

SMD (Surface Mounted Device) technology is the workhorse for general lighting. Because the LED chips are spread out over a larger area, they produce a wider, more diffuse light that is less intense and has less glare. This makes SMD the ideal choice for applications where you need comfortable, even illumination over a large space. Think of LED ceiling panels in an office, under-cabinet lighting in a kitchen, or standard downlights in a living room. For these situations, you don't want a harsh spotlight; you want broad, soft light. SMD solutions are also often more cost-effective for achieving this kind of ambient lighting.

Making the Right Choice

The best choice always comes down to the application. There is no single "best" technology. As a purchasing manager, asking the right questions about the project's goal is key.

What is the purpose of a COB light?

You know what a COB light is, but why was it even invented? What specific gap does it fill in the lighting world? Not knowing its core purpose means you might use it where it does not belong.

The main purpose of COB technology is to create a very high-intensity light from a single, compact point. It was developed to solve the problem of replicating the look and feel of a traditional halogen bulb but with far greater energy efficiency and a much longer lifespan.

By packing many small LEDs into one module, manufacturers could finally offer the power and focus that designers loved about old halogen technology, but without the high heat, energy waste, and constant replacements. Understanding this core purpose helps you see exactly where COB fits in your lighting strategy¹⁰. It's a specialist tool designed for impact.

Achieving High Lumen Density

The primary goal of COB is to achieve high "lumen density." This sounds technical, but it just means packing the most amount of light (lumens) into the smallest possible area. Before COB, if you needed a very bright light, you had to use a very large fixture with many separate LEDs or a power-hungry halogen bulb. COB technology changed that. It allows us to create incredibly bright spotlights and downlights in very small and sleek housings. This is a huge advantage in modern architecture and retail design, where minimalist aesthetics are often preferred. It gives designers a powerful tool without a bulky fixture.

Creating a Superior Halogen Replacement

For decades, halogen lamps were the standard for accent lighting because of their brilliant, crisp light from a single point. But they were inefficient and hot. COB was engineered specifically to be a superior replacement. It produces that same single-shadow, high-quality light but uses about 85% less energy and can last over 20 times longer. I remember when we first started offering COB solutions; our clients in the retail and hospitality sectors were thrilled. They could finally get the dramatic lighting effects they wanted without the high electricity bills and constant maintenance calls to replace burned-out bulbs.

Simplifying Luminaire Design and Manufacturing

A less obvious but important purpose of COB technology is that it simplifies things. For a lighting designer, working with a single, compact light source is much easier than arranging many individual LEDs to achieve a desired effect. This gives them more creative freedom. For a manufacturer like me, it can also streamline the assembly process. Soldering one COB module onto a heat sink is often faster and requires less complex circuitry than placing and soldering dozens of individual SMD chips. This efficiency in both design and production helps make high-performance lighting more accessible.

Conclusion

COB downlights provide powerful, focused light from a compact source, making them ideal for accenting spaces and high ceilings. They are a type of LED, not a replacement for all LEDs.