A constant current driver circuit is a type of electronic circuit specifically designed to supply a steady flow of current to an LED, regardless of changes in voltage or resistance. This is especially important for COB (Chip-on-Board) LEDs, where consistent performance and protection from overcurrent are key to long-term reliability.
Why Current Control Matters
Unlike traditional light bulbs, LEDs are current-driven devices. That means the amount of current flowing through the LED, not just the voltage, determines how bright it gets. If too much current flows, the LED can overheat and fail. If the current is too low, it may flicker or appear dim. This is where constant current drivers shine.
How the Circuit Works
In a constant current circuit, the driver adjusts its output voltage automatically to ensure that the desired current (measured in milliamps, like 350mA or 700mA) stays consistent. It continuously monitors the load (in this case, the LED or array of LEDs) and fine-tunes the voltage to keep the current steady, even if the temperature, resistance, or LED aging changes over time.
For example, a typical constant current driver might be labeled:
Output: 700mA, 20–42V
This means the driver will always supply 700mA of current, while the output voltage can vary between 20V and 42V depending on how many LEDs are in the circuit and how they behave during operation.
Main Components Inside the Circuit
- Current sense resistor: Measures the actual current flowing and provides feedback.
- Control IC or transistor: Adjusts the output voltage based on current feedback.
- Switching regulator or linear regulator: Maintains the efficiency of the power conversion process.
- Protection features: Often includes thermal shutdown, short circuit protection, and over-voltage protection.
Why It’s Ideal for COB LEDs
COB LEDs typically consist of multiple LED chips working as a single module. Because they share the same current, using a constant current driver helps prevent uneven brightness and overheating of individual chips. It also simplifies wiring, especially when LEDs are wired in series, and improves energy efficiency.
A constant current driver circuit ensures that your LEDs receive just the right amount of power, not too much and not too little, regardless of what’s happening elsewhere in the system. That’s a huge win for performance, safety, and lifespan, especially in professional lighting applications.