The Difference Between Constant Voltage vs Constant Current
If you’ve been shopping for LED lights, you’ve likely come across the terms constant current and constant voltage. All LED lights require a power supply, but the LED’s internal components will determine whether a constant current driver or a constant voltage power supply is needed.
Constant-Voltage Power Supply
A constant voltage power supply maintains a steady output voltage regardless of changes in the load or input voltage. Constant voltage power supplies will supply an output current up to their maximum rating based on the needs of the light they are powering. This current may vary depending on the voltage, number of LEDs, and wire gauge.
Certain LED products and electronic devices require a constant-voltage power supply if they use a different operating voltage than what’s supplied by the line voltage. For example, if you want to power a 12V or 24V DC (direct current) LED strip light with your home’s 120V AC (alternating voltage) wiring system, you must use a constant voltage power supply to safely reduce and convert the power from AC to DC.
Constant-Current Driver
A constant-current driver regulates and maintains a steady current over its specific voltage range directly to an LED. This current is typically measured in milliamps (mA) or amps (A). LEDs are current-driven devices, meaning they require a specific operating current to ensure optimal performance and longevity. Some drivers do lower and convert the output voltage, but the voltage will vary based on the current required by the LED chips.
Constant current drivers are commonly used with high-powered industrial lights and retrofit light kits. These lights use either built-in or external constant-current drivers to supply the required current. When replacing an outdated LED driver, it is important to verify that the output current, power consumption (wattage), and voltage range of the new driver match the existing one.
Which One Do You Need?
An LED light should never use a constant voltage power supply and a constant current driver at the same time, so you must determine which power supply your light requires. The most common reason for buying a constant current driver is if you need to replace a failing or outdated driver for an existing lighting system. Not many residential lighting fixtures require this, so the average homeowner will rarely need to buy an LED constant current driver. Therefore, constant voltage power supplies are more often than not the power supplies that people shop for since they are used to power strip lighting systems and electronic devices. When choosing a power supply for LED strip lights, the output voltage must match the voltage of the strip light.
