Why Old Dimmers Don’t Work with LEDs and How You Can Fix It

Glossary of Terms

In the blog below, we discuss some technical aspects of electrical loads and LEDs that aren’t always common knowledge. To help you understand, read this glossary:

• AC voltage waveform: Alternating current (AC) refers to the periodic cycling of current between its highest and lowest values within a circuit. The current flows in one direction when the voltage is positive and reverses direction when the voltage becomes negative. AC is highly effective for power distribution due to its ease of transmission and conversion, making it an efficient method for delivering electricity from generation facilities to residential, commercial, and industrial locations. It is the most common type of input power used in standard and high-voltage applications within homes, businesses, and industrial sites.

• Electrical load profile:  An electrical load profile is the representation of power consumption over time, illustrating how energy use varies throughout a specific period, such as a day or year. It highlights peaks, troughs, and trends in usage, helping identify operational patterns and periods of maximum demand. Load profiles are essential for optimizing energy efficiency, managing costs, designing tailored electrical systems, and aiding utilities in balancing grid supply and demand.

• Internal diode-capacitor: An internal diode-capacitor is a circuit component used to convert AC to DC, smooth voltage fluctuations, and stabilize power. The diode directs current flow in one direction for correction, while the capacitor stores and releases energy to maintain steady voltage. This configuration is common in power supplies, signal processing, and voltage multiplier circuits.

• Power draw: Power draw refers to the amount of electrical power consumed by a device or system during operation, typically measured in watts (W) or kilowatts (kW). It represents the instantaneous energy usage and is influenced by factors such as the device's design, efficiency, and load. Monitoring power draw is essential for energy management, cost estimation, and ensuring electrical systems are not overloaded.

• Resistive loads: Resistive loads are electrical loads that convert all the electrical energy they consume directly into heat or light.  Resistive loads draw power at a constant rate and maintain a consistent phase relationship between voltage and current, making them straightforward to analyze and control. Examples include incandescent light bulbs, electric heaters, toasters, and ovens. 

• Respond linearly: For an electrical current to respond linearly, it must change in direct proportion to the applied voltage.  In a linear response, the relationship between voltage and current forms a straight line on a graph, indicating a constant resistance. This behavior is characteristic of resistive loads, which lack reactive components such as capacitance or inductance that could introduce phase shifts or non-linear behavior.

For more lighting terms, check here.

Retrofitting LED lighting into existing fixtures is a popular way to improve energy efficiency and lighting quality without a full replacement. However, many encounter challenges when using older dimmer switches. These dimmers were not designed with LEDs in mind, and they operate with a different electrical load profile. As a result, using them with LEDs often leads to flickering, poor performance, or even damage to the bulb. This is because older dimmers cannot properly manage the low-power draw of LEDs, causing compatibility issues.

Understanding these technological differences and the role of dimmers in regulating light levels is key to a successful lighting upgrade. This article explores why older dimmers often fail with retrofit LEDs and offers solutions for achieving smooth and efficient dimming.

For more information about dimming LEDs, read our "Dimming for Beginners: The Basics" blog. 

LEDs operate with significantly less power than traditional incandescent bulbs, leading to notable differences in how they interact with dimmers. Traditional dimmers are designed for the higher power draw and simple resistive loads of incandescent bulbs, which respond linearly to changes in the dimmer set point. In contrast, LEDs feature non-linear, capacitive loads due to their internal diode-capacitor power supplies, resulting in variable current demands.

Older dimmers, optimized for steady and predictable current from incandescent bulbs, struggle to accurately detect and manage the minimal and variable load required by LEDs. 

Furthermore, the absence of standardized performance requirements for dimmers and LED lamps further complicates compatibility. Organizations like NEMA have developed guidelines, such as SSL 6, which provide basic recommendations for dimming compatibility between LEDs and controls. However, SSL 6 remains incomplete, lacking detailed rating systems to ensure consistent performance across products.

Ensuring compatibility between dimmers and LED lights is essential for achieving reliable performance and extending the lifespan of your lighting system. The transition from incandescent to LED technology has introduced challenges due to differences in electrical characteristics, load types, and the limitations of older dimmer designs. However, advancements in dimmer technology, such as universal designs, micro-power circuitry, and improved synchronization methods, have made it easier to overcome these obstacles.

Super Bright LEDs offers a wide selection of dimmers specifically designed for LED lighting, ensuring optimal compatibility and performance. From TRIAC dimmers to advanced options for LED light strips, their products provide smooth, flicker-free dimming and are rigorously tested to meet the highest standards.