Techniques for Preventing Flickering in LED Lighting Systems

Surface illumination device that reduces flicker, eye strain, and fatigue. The device emits light that is directed away from the user's line of sight. This is achieved by configuring the light distribution so that the maximum intensity angle of light emitted from the center of the device's light-emitting surface is within -90° to <0° in a plane perpendicular to the surface. This avoids direct perception of the light and reduces flicker perception.

Reliable error detection and mitigation in LED lighting devices to prevent flickering or color shifting. The method involves monitoring the forward voltage of the LED emitters in relation to the forward voltage of a detector LED. If an emitter's voltage deviates excessively, indicating a fault, the device enters an unstable state but keeps operating. If the deviation continues, indicating a failed emitter, the device enters an inoperable state and disables that emitter. This prevents flicker and color shifts from failed emitters while allowing continued operation.

A method for controlling LED lighting devices to prevent flickering or color shifting. The method involves monitoring the forward voltage of the LED emitters relative to a detector. If the forward voltage goes outside an acceptable range for a majority of time intervals, indicating a failed LED, it is deactivated. If the forward voltage fluctuates rapidly, indicating flickering or color shifting, the drive current is adjusted to stabilize it.

LED light bulbs that provide constant light output across the AC cycle without flicker or power factor issues. The bulbs use LED strings with enough LEDs so they are fully on at peak voltage. An impedance adjust circuit shunts LEDs to overcome the non-linear voltage-current characteristic of LEDs. This makes the string linear and allows direct AC driving without electronics.

An LED lighting device that prevents flickering and maintains stable illumination quality even if an LED fails. The device has an LED emitter, LED detector, and control circuit. It continuously compares the forward voltage across the emitter to the forward voltage across the detector. If the emitter voltage is outside an acceptable range for the majority of a time window, it indicates instability or LED failure. The control circuit puts the device into an interim state to avoid flickering. If the instability persists in subsequent time windows, it deactivates the emitter.

A multi-colored LED illumination device that can operate in an interim state to avoid flickering or color shifting and prevent driving a failed LED. The device has an LED emitter, LED detector, and control circuit. It compares the forward voltage across the emitter to the detector's forward voltage at equal intervals. If the emitter voltage is outside an acceptable range compared to the detector voltage for a majority of a first-time window, it enters the interim state. If the emitter voltage remains outside the range for the majority of a second-time window, it deactivates the emitter.

LED light bulb with improved efficiency, dimming, power factor correction, and power conversion efficiency. The LED light bulb has an LED string with enough LEDs to be fully on at peak AC voltage. It also uses circuitry to adjust impedance to make the LED string appear resistive. This reduces flicker and allows dimming without electronics. The bulb communicates control signals over the AC power lines to control brightness and power factor correction.

Driving an LED light connected to a dimmer without flickering or other issues. The LED driver has a dynamic control circuit in series with the LEDs that present increasing impedance as the current decreases. This provides a "soft landing" when the dimmer cuts the phase and reduces the LED current. The circuit uses a sense resistor and transistor to monitor and control LED current, allowing it to smoothly taper down without abrupt changes.

LED lighting design that improves efficiency, power factor, flicker, and dimming compatibility. The design uses a long string of LEDs matched to the AC voltage and enough to fully turn on at peak voltage. This eliminates the need for power electronics. The string is impedance-matched to be resistive and has a unity power factor. The LEDs flicker at twice the AC frequency but phosphor persistence smooths it out. The string can also be tapped to adjust the impedance for dimming.

Light-emitting device and illuminating apparatus that reduces flickering of light. The device has two groups of LEDs on a board and a controller that powers them with an undulating voltage. During periods of undulating voltage where it's above a first threshold and below a second threshold, only the inner group emits light. When the voltage is above the second threshold, both groups emit light. This reduces flicker compared to all LEDs turning on/off.