Constant Voltage vs. Constant Current LED Drivers: What Aquarium DIYers Should Know

Choosing the right LED driver is critical for DIY aquarium lighting. There are two types: constant voltage (CV) and constant current (CC). Pick the wrong one and you risk overheating LEDs, wasting power, and shortening lifespan. This guide shows how to choose quickly and safely.

The Problem With Constant Voltage

A constant voltage supply (e.g., 12 V or 24 V) works well for LED strips that already include current limiting. High‑power discrete LEDs are different: as junction temperature rises, forward voltage drops and current tends to increase. Under a fixed‑voltage source this creates a positive feedback loop (thermal runaway) that can overheat and damage LEDs.

You can add series resistors to limit current, but they waste power as heat and reduce efficiency. Example: dropping 2 V at 700 mA wastes 1.4 W per string—heat that your heatsink must remove without producing any light. For serious aquarium lighting, this hurts efficiency, thermal headroom, and reliability.

Why Constant Current Is Better

A constant current driver fixes the current (e.g., 700 mA, 1500 mA) and lets the voltage float to what the LEDs require. This:

This solves two big problems:

1. It stops LEDs from overheating and drawing too much current by keeping the current steady at a safe level.
2. It removes the need for inefficient resistors, so more power goes into light instead of wasted heat.

There is another major advantage for reef aquariums: constant current allows each channel to have a completely different number of LEDs. For example, the blue channel may have many more LEDs than the red channel, but the driver will still keep each channel stable. This flexibility is one reason why almost all high end reef lights use constant current drivers.

Which Should You Choose?

• Use CV when: driving pre‑regulated LED strips or modules that already include current limiting; simple, low‑power builds.
• Use CC when: driving high‑power discrete LEDs; mixing different LED counts per channel; needing reliable dimming and thermal stability.

Takeaway

LEDs are not like ordinary light bulbs. Their behavior changes with temperature, and without proper current control they can be damaged. For high‑power aquarium lighting, constant current drivers offer better safety, efficiency, and design flexibility. Use CC drivers for serious builds; CV is acceptable for pre‑regulated strips and simple projects.

Quick Comparison Table

Safety note

Working with high‑power LEDs and drivers involves electrical and thermal risks. Ensure proper heatsinking, secure electrical connections, and follow the driver’s datasheet. If you are unsure about wiring, thermal management, or safety procedures, consult a qualified technician.