Understanding LED Drivers: How to Match a Replacement

Updated October 2026.

LEDs require drivers for two purposes

1. LED chips run on low-voltage direct current. Buildings supply 120-277V alternating current. An LED driver converts building power to the low-voltage direct current the LEDs need.

2. LED drivers also protect LEDs from voltage or current fluctuations. A change in voltage could cause a change in the current being supplied to the LEDs. LED light output is proportional to its current supply, and LEDs are rated to operate within a certain current range (measured in amps). Therefore, too much or too little current can cause light output to vary or degrade faster due to higher temperatures within the LED.

Save LEDs: Replace External LED Drivers

When an LED stops operating before the end of its rated lifetime, it can usually be saved if the driver is replaced. Drivers often fail prematurely due to high internal operating temperatures. Components called electrolytic capacitors are typically the cause of death. Electrolytic capacitors have a gel inside them that gradually evaporates over the lifespan of the driver. High temperatures quicken the evaporation of the gel and shorten the life of the capacitor, causing the driver, and hence your LED, to stop working unexpectedly.

The temperature within the driver correlates to the external temperature on the driver case. A small circle on the label of most LED drivers, called the "TC point," is the hottest point on the driver. This point is usually marked with a temperature and is used to determine the driver's max operating temperature. If a driver runs too close to this limit, it will have a shorter lifespan than if it were operated cooler. Drivers must be used at operating temperatures below the TC point (or contain long-life electrolytic capacitors) for the driver to outlast the LED. Otherwise, drivers can fail and must be replaced.

Choosing an LED Driver

There are two main types of external LED drivers, constant-current and constant-voltage, as well as a third type called an AC LED driver. Each is designed to operate LEDs with a different set of electrical requirements. When replacing a driver, match the old driver's input and output ratings as closely as possible.

Constant-Current Drivers

Constant-current drivers power LEDs that require a fixed output current and a range of output voltages. There will be only one output current specified, labeled in amps or milliamps, along with a range of voltages that will vary depending on the load (wattage) of the LED. For example, a driver labeled 700mA with an output range of 4-13V DC delivers a fixed 700 milliamps to any load that falls within that voltage range.

Constant-Voltage Drivers

Constant-voltage drivers power LEDs that require a fixed output voltage with a maximum output current. In these LEDs, the current is already regulated, either by simple resistors or an internal constant-current driver, within the LED module. These LEDs require one stable voltage, usually 12V DC or 24V DC. For example, a 24V DC driver rated 1.04A maximum can run up to about 25 watts of 24V tape light.

AC LED Drivers

AC LED drivers are essentially no-minimum-load transformers. Many conventional electronic transformers have a minimum load, and an LED lamp draws so little power that the transformer may not register it at all, which causes flicker or no light. AC LED drivers are used with lamps that already contain an internal driver, such as 12V AC LED MR16 lamps. Check the lamp's datasheet: if the lamp requires DC input, it cannot be used with an AC LED driver.

Other Factors to Consider

Max Wattage

Standard industry practice is to load a driver to no more than about 80 percent of its maximum rated wattage. Running a driver at or above its maximum overstresses its components. For example, a driver rated 96 watts maximum should run no more than about 77 watts of LEDs (96 x 0.8 = 76.8).

Dimming

Both constant-current and constant-voltage LEDs and drivers can be made dimmable, but both the LEDs and the driver must say so on the datasheet. If the specs don't mention dimming, assume the product is not dimmable. Dimmable drivers specify the control they need, such as phase (TRIAC or trailing edge) or 0-10V dimmers. Test a specific LED and driver combination before a large purchase if the maker doesn't publish a dimmer compatibility chart.

Power Factor

Power factor describes how effectively a driver draws power from the building's supply. It is the driver's real power (watts) divided by input volts times amps. The range is 0 to 1; the closer to 1, the better. A good power factor is 0.9 or above.

UL Class 1 vs UL Class 2

UL Class 2 drivers comply with UL 1310, meaning output is considered safe to contact and no major safety protection is required at the LED or luminaire level. The risk of fire or shock at the output is low. Class 2 outputs stay below roughly 60 volts in dry locations, 30 volts in wet locations, and 100 watts. Those limits restrict how many LEDs a Class 2 driver can run.

UL Class 1 drivers have outputs outside the Class 2 limits, so safety protection is required within the fixture. A Class 1 driver can run more LEDs per driver, which is why it is common in larger fixtures.

Choosing a driver replacement

Copy these from the old driver's label before you order:

Constant current drivers:

• Rated output current (mA)
• Output voltage range
• Input voltage
• Control and dimming options
• Lead exit configuration and can size

Constant voltage drivers:

• Output voltage (12V, 24V, etc.)
• Input voltage (120V, 277V, etc.)
• Maximum output (watts)

Get it matched

Driver labels are dense, and a near-match can burn out an LED board. Text a photo of the old driver's label to 949-589-3020 and a Lighting Specialist will match it from our LED drivers and transformers. For low-voltage halogen and LED lamps on transformers, see magnetic and electronic transformers.