Guide
Constant Voltage vs Constant Current LED Drivers
How to tell which type your LED requires, then map EMCOD families to constant-voltage or constant-current systems.
Written by Projekt Supply Lighting Team. Last reviewed September 2, 2026. First published September 2, 2026. Part of the EMCOD LED driver and transformer guide.
Two different jobs
A constant-voltage driver maintains a set output voltage. Common examples are 12 V DC and 24 V DC. The connected LED load draws the current it requires within the system’s limits. Typical fixture or tape marking: 12VDC or 24VDC. Source: EMCOD catalog record
A constant-current driver regulates output current. Common LED markings are 350 mA, 500 mA, or 700 mA. Voltage then varies within the driver’s permitted output range as the LED requires. Typical specification: a current in milliamps, not a tape voltage. Source: EMCOD product page
First identification rule
If the LED label says
12VDC · 24VDC
Start with constant voltage
If the LED spec says
350 mA · 500 mA · 700 mA
Start with constant current
This is a first-identification rule. Confirm the full manufacturer specification before selecting a driver.
Always verify the complete LED manufacturer specification. This rule is a starting point, not a substitute for exact electrical requirements. Independent source: U.S. Department of Energy
Side-by-side comparison
| Characteristic | Constant voltage | Constant current |
|---|---|---|
| What is regulated? | Output voltage, commonly 12 V DC or 24 V DC. | Output current, commonly specified in milliamps. |
| Typical LED marking | 12VDC or 24VDC. | 350 mA, 500 mA, 700 mA, or another current rating. |
| Common output notation | 12DC / 24DC in many EMCOD constant-voltage MPNs. | A current-mode series code such as ECC-UD, plus a wattage class. |
| Typical applications | LED tape and fixtures that specify a fixed DC voltage. | LED modules or arrays that specify drive current, not tape voltage. |
| Driver selection basis | Output voltage, then wattage, input, dimming, and listing. | Required current, then the driver’s published current/voltage window and wattage. |
| What must match? | Voltage, polarity, wattage class, input, control, and environment. | Current, polarity, permitted voltage window, wattage, input, control, and environment. |
| Risk if the wrong type is selected | A current-mode driver can over-drive or fail to run a voltage-marked load. | A 12/24 V tape driver can destroy or starve a milliamp-rated module even when wattage looks large enough. |
What the driver holds steady
Constant voltage
Driver holds 24 V
LED load determines current
The driver attempts to keep output at the listed voltage, such as 24 V DC. Current then depends on the connected LED load, within the driver’s published limits.
Constant current
Driver holds 700 mA
Voltage moves in the published window
The 700 mA figure is a teaching example, not an EMCOD nameplate. Voltage adjusts within the permitted driver and LED range.
How EMCOD families map
Rows use catalog output type, input, and control labels. In this catalog, ECC-UD is the constant-current LED driver family. The six comparison families below are constant voltage. Source: EMCOD catalog record
| Family | Output type | Typical output | Input | Dimming | Use case | View family | Source |
|---|---|---|---|---|---|---|---|
| MLE-P | Constant voltage | 12 V or 24 V DC | 120 V 50/60 Hz | Confirm on the exact spec sheet | J-box electronic CV driver | View MLE-P | EMCOD catalog record |
| MLE | Constant voltage | 12 V or 24 V DC | 100–277 V 50/60 Hz | Confirm on the exact spec sheet | Electronic CV driver | View MLE | EMCOD catalog record |
| MLE-UD | Constant voltage | 12 V or 24 V DC | 100–277 V AC 50/60 Hz | Catalog: universal 5-in-1. Confirm methods on the spec sheet | Universal-dimming CV | View MLE-UD | EMCOD catalog record |
| ECV-UD | Constant voltage | 12 V or 24 V DC | 100–277 V 50/60 Hz | Catalog: universal 5-in-1. Confirm methods on the spec sheet | Universal-dimming CV | View ECV-UD | EMCOD catalog record |
| ES-UD | Constant voltage | 12 V or 24 V DC | 100–277 V AC 50/60 Hz | Catalog: electronic PWM | Slim PWM CV | View ES-UD | EMCOD catalog record |
| EDR | Constant voltage | 12 V or 24 V DC | 110–277 V 50/60 Hz | Catalog: universal DIN-rail. Confirm methods on the spec sheet | DIN-rail CV | View EDR | EMCOD catalog record |
| ECC-UD | Constant current | Current-mode; voltage window on the spec sheet, not 12/24 V tape output | 100–277 V 50/60 Hz | Catalog: constant-current universal dimming. Confirm methods on the spec sheet | LED modules specified in milliamps | View ECC-UD | EMCOD catalog record |
Also cataloged as constant-voltage, and not shown as extra table rows: Dimmer+Driver Combo (EDD), CCT Tunable Combo, MLE-UD-C2, and ML. Landscape transformers are a different product class.
Constant-current example
Constant-current identification
- Example LED marking:
- 700 mA (illustrative module marking, not an EMCOD specification)
- Driver type required:
- Constant current at that published current
LED marking in milliamps → start with a constant-current driver
700 mA marking is a current requirement, not a 12 V or 24 V tape voltage.
Do not choose a 24 V constant-voltage driver by wattage alone.
The EMCOD constant-current family is ECC-UD. Catalog records store wattage class and input, not a milliamp field, so this page does not assign 700 mA to ECC-010-UD or any other ECC MPN. Read the specification sheet for the current setting and voltage window.
Projekt Supply calculation/concept example. The 700 mA figure is an illustrative LED marking, not a published EMCOD output. Always verify the LED manufacturer’s current requirement and the EMCOD specification sheet.
ECC-UD example: ECC-010-UD is cataloged as a 10W constant-current driver, 100-277V 50/60Hz input, Indoor / IP20. The manufacturer product page titles it a Class 2 constant-current unit and lists a 3–42 V DC output window with a 10 W maximum. That is not a 24 V tape driver. A 100 W 24 V constant-voltage driver remains the wrong output method even if its wattage class is larger. Source: EMCOD manufacturer specifications
Constant-voltage example
Example: 24 V DC LED tape with about 70 W connected load. The candidate driver must be constant-voltage, 24 V DC output, at or above that wattage, with matching input, dimming, and location listing. A 24 V example is MLE60-24DC-P for a 60 W class (too small for 70 W) versus a 96 W 24 V class such as MLE96-24DC-P. Source: EMCOD manufacturer specifications
Work the wattage arithmetic in How to Size an LED Driver.
After you confirm constant voltage, compare 12 V and 24 V in 12V vs 24V LED Drivers.
Why wattage alone is not enough
Compatibility still depends on exact load and manufacturer instructions. “Potentially” never means automatic.
| LED requirement | Driver | Wattage | Compatible? |
|---|---|---|---|
| 24 V DC LED | 60 W 12 V DC constant-voltage driver | 60 W | No. Output voltage does not match. |
| 24 V DC LED | 96 W 24 V DC constant-voltage driver | 96 W | Potentially, if connected load is at or below 96 W and input, dimming, listing, and manufacturer instructions also match. |
| 700 mA LED (example marking) | 100 W 24 V constant-voltage driver | 100 W | No. Wrong output method, even if wattage is larger. |
Common mistakes
- Choosing by wattage only.
- Confusing volts and amps.
- Assuming all LEDs use constant voltage.
- Replacing a current driver with a voltage driver because the wattage looks close.
- Ignoring the operating voltage range of a constant-current load.
- Assuming an mA marking is the same as a driver’s maximum current capacity.
- Failing to verify input voltage.
- Ignoring dimming and control requirements.
Match control method in LED Driver Dimming Explained.
Continue in EMCOD Replacement Guide.
Common questions
What is a constant-voltage LED driver?
A constant-voltage driver holds a set DC output, commonly 12 V or 24 V. The LED load draws the current it needs within the driver’s limits. Most LED tape is specified this way. EMCOD examples include MLE-P, MLE, MLE-UD, ECV-UD, ES-UD, and EDR.
What is a constant-current LED driver?
A constant-current driver regulates output current. Voltage then sits wherever the LED requires, inside the driver’s published window. Typical LED markings are milliamps, not 12VDC/24VDC. In the EMCOD catalog, that hardware is the ECC-UD family.
How do I know which one my LED requires?
Read the LED specification. If it is marked 12VDC or 24VDC, start with constant voltage. If it is marked in milliamps, start with constant current. That identification is a starting rule, not a substitute for the complete electrical specification.
Can I replace a constant-current driver with a constant-voltage driver?
Not as a swap. A 24 V tape driver does not become a 700 mA driver because its wattage class is larger. Match topology first, then current or voltage, wattage, input, dimming, and listing on the exact specification sheet.
What does 700mA mean on an LED?
It is a current rating: 700 milliamps. The LED expects a driver that regulates that current, not a 12 V or 24 V tape supply. It is not the same thing as a driver’s maximum current capacity printed in amps.
Is 24V always constant voltage?
No. 24 V DC is a common constant-voltage output, but a constant-current driver may also show a voltage window that happens to include 24 V. The LED marking and the driver topology still have to match. See the 12 V vs 24 V guide after you confirm constant voltage.
Does wattage matter for constant-current drivers?
Yes. Current must match, and the connected load still has to stay within the published wattage and voltage window. ECC-010-UD is cataloged as a 10 W class. A current match that exceeds that wattage class is still oversized for that MPN.
Which EMCOD family is constant current?
In the current Projekt Supply catalog, ECC-UD is the constant-current LED driver family. The six comparison families used on this page—MLE-P, MLE, MLE-UD, ECV-UD, ES-UD, and EDR—are constant-voltage. Other constant-voltage families include EDD, EDD-CCT, MLE-UD-C2, and ML.
Return to the EMCOD selection guide or browse EMCOD LED drivers.
Matched the output type? Browse EMCOD LED driver families →
Technical Sources & References
- Projekt Supply catalog / EMCOD Lighting Group — ECC-UD Series family (constant-current universal dimming)Manufacturer catalog / Projekt catalog record
- EMCOD Lighting Group — ECC-010-UD specification sheetManufacturer specification sheet
- EMCOD Lighting Group — ECC-010-UD manufacturer product pageManufacturer product page
- Projekt Supply catalog / EMCOD Lighting Group — MLE-P Series Electronic JBox Driver familyManufacturer catalog / Projekt catalog record
- EMCOD Lighting Group — MLE60-12DC-P specification sheetManufacturer specification sheet
- Projekt Supply catalog / EMCOD Lighting Group — MLE-UD Series familyManufacturer catalog / Projekt catalog record
- Projekt Supply catalog / EMCOD Lighting Group — ECV-UD Series 5-in-1 Dimming familyManufacturer catalog / Projekt catalog record
- Projekt Supply catalog / EMCOD Lighting Group — ES-UD Series familyManufacturer catalog / Projekt catalog record
- Projekt Supply catalog / EMCOD Lighting Group — EDR Series DIN Rail Universal Driver familyManufacturer catalog / Projekt catalog record
- Projekt Supply catalog / EMCOD Lighting Group — MLE Series Electronic Constant Voltage familyManufacturer catalog / Projekt catalog record
- Projekt Supply — Illustrative 700 mA constant-current identification exampleProjekt Supply calculationConcept example from a stated LED marking, not an EMCOD milliamp rating.
- U.S. Department of Energy — LED LightingIndependent technical source
