LED lights have become increasingly popular due to their energy efficiency and long lifespan. However, many users experience an annoying issue: flickering. Unlike older CFL bulbs, which are often perceived as having a more stable light output, LEDs can sometimes flicker, raising questions about why this occurs and whether it indicates a problem with electrical wiring.
The answer to why LED lights flicker often lies in the design of their power supplies, particularly in cheaper models. To understand this, let’s delve into the basic components of a typical LED bulb. An LED bulb essentially consists of several low-voltage diodes, typically around 3 volts each, arranged in a series. These diodes are connected to the mains electricity supply through a rectifier, which converts AC power to DC, and a current-limiting element. This current limiter can be a simple resistor or capacitor, as depicted in the diagram below, or, more commonly in some regions, a linear regulator.
Schematic diagram of a basic LED bulb circuit, illustrating the rectifier, capacitor, resistor, and series of LEDs that contribute to flicker sensitivity due to voltage fluctuations.In cost-effective LED bulb designs, the total forward voltage of the series of LEDs is intentionally set to be very close to the rectified mains voltage. This approach minimizes energy loss across the current-limiting component, enhancing efficiency. However, this design choice also makes the LED bulb highly susceptible to voltage fluctuations on the power line.
When appliances like HVAC systems or water heaters switch on or off, they can introduce electrical noise and voltage variations into the power supply. Because the LEDs in these bulbs are operating so close to their minimum forward voltage requirement, even minor dips in voltage can be enough to drop below this threshold, causing the LEDs to momentarily turn off and then back on – resulting in the perceived flicker.
While a larger capacitor in the circuit or a more sophisticated voltage regulation system could mitigate this flickering issue, these additions would increase the cost of manufacturing. Consequently, budget-friendly LED bulbs often omit these more advanced components to keep production costs down. Similarly, using fewer LEDs in series could create more headroom for voltage fluctuations, but this would lead to increased power dissipation across the current-limiting element. In non-isolated designs, where components are directly connected to mains voltage, heat dissipation must be minimized due to safety regulations preventing exposed metal heatsinks. This limitation further incentivizes manufacturers to use simpler, more sensitive designs in cheaper LED bulbs, ultimately contributing to the flicker problem.
In conclusion, the flickering observed in LED lights, especially when compared to the steadier light of CFL bulbs, is primarily attributed to the cost-saving design choices in their power supplies. These designs prioritize efficiency and low manufacturing costs over robust voltage regulation, making them vulnerable to common voltage fluctuations in household electrical systems.
