Flicker Prevention in LED Lighting

Flicker-free LED driving method and circuit to eliminate stroboscopic flicker in LED lighting. The method involves controlling the current through the LED string and regulating the input current using a switching tube and voltage feedback. A capacitor stores energy to maintain constant current. This prevents flicker by keeping the LED current steady while adjusting input current.

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Reducing jitter in low brightness LED lighting by using a vibration suppression module. The module has a resistor and capacitor connected in parallel with the LED and inductor. This creates a low pass filter to smooth out current ripples when the LED brightness is slowly increasing from low levels. This prevents flicker perception in dim environments.

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Pulse width modulation (PWM) dimming of LEDs that improves dimming accuracy, particularly at low duty cycles. The method involves compensating for current deviations in PWM dimming by adjusting the slope of the inductor current within the PWM cycle based on the determined magnitude relationship between the absolute values of the rising and falling slope. This periodic lifting operation on the inductor current within the PWM cycle, in response to the adjusted slope, compensates for the current deviation of the output current of the LED driver chip.

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Flicker-free LED dimming system and method that provides smooth dimming without strobing at low brightness levels. The system uses a modified PWM dimming technique that allows precise control of the LED output current to eliminate flicker. It achieves this by using a dual-control strategy. At low duty cycles, a separate control signal is generated to accurately count the passing cycles of the PWM signal to fine-tune the output current. At higher duty cycles, the regular PWM signal is used. This prevents current interruptions that cause flicker at low brightness. By transitioning between the two control methods based on duty cycle, flicker-free dimming is achieved across the entire dimming range.

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LED dimming method to mitigate stepped variation and non-smoothness of the dimming curve, providing a smoother dimming effect for LEDs. The method involves changing the duty cycle of the PWM signal in a way that avoids steps. When the duty cycle is less than a threshold, the method takes sets of n PWM periods, calculates the average duty cycle, and outputs multiple sets in order with incrementing or decrementing average duty cycles. This allows duty cycle changes of 0.1% or less to avoid stepped current variations.

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Flicker-free LED dimming control system that eliminates stroboscopic effects when dimming LED lights. The system uses a power input module, boost module, LED module, switch module, voltage stabilizer, MCU, PWM-to-DAC converter, and linear current loop. The MCU controls the PWM-to-DAC converter to adjust the LED current. The linear current loop stabilizes the LED current and prevents flicker.

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LED lighting with smooth dimming over the entire brightness range, addressing the issue of visible flickering and color shifts at low brightness with traditional pulse width modulation (PWM) dimming. The high dynamic smooth dimming is achieved by combining pulse density modulation (PDM) and frequency modulation dimming. At low brightness, the frequency of the half-bridge switching network is increased instead of just PDM, providing more precise dimming and meeting the linear brightness change perceived by the human eye.

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High-precision adaptive dimming of LED lights without flicker or noise using high-frequency PWM. The dimming is achieved by a control circuit in the LED power supply that adjusts the PWM duty cycle based on the desired brightness level. The circuit has a microcontroller with a lookup table to map duty cycles to brightness levels. It compares the measured duty cycle to the reference for the target level, and adjusts if needed to compensate for attenuation in the circuitry or LED device. This ensures stable brightness and eliminates flicker and noise compared to low-frequency PWM.

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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.

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LED backlight dimming method to balance brightness, stroboscopic effect, noise and uniformity for low brightness levels. The method involves adaptive frequency conversion of PWM dimming based on brightness setting. For low brightness, it uses lower frequencies to reduce brightness loss and uniformity issues. For higher brightness, it uses higher frequencies to avoid flicker. The frequency conversion is achieved by a module that generates custom frequencies based on brightness thresholds. This balances defects like unevenness, stroboscopic effect, noise and uniformity for low brightness levels.

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PWM dimming system for LED lighting that avoids stroboscopic and noise issues while providing deeper dimming compared to conventional PWM dimming. The system uses a separate dimming control module that sends PWM signals to the LED driver module. The driver module then uses the PWM signals to turn the LEDs on and off, providing dimming. This separation of PWM generation and LED control allows optimizing the PWM frequency for reduced stroboscopic effects while still achieving deeper dimming levels.

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A method and system for controlling current stability in LED lighting applications. The method involves using a separate adjustment circuit connected between the LED light sources and the power supply. This allows providing different constant currents to each LED, unlike traditional LED drivers. A central controller coordinates the adjustment circuit and main LED driver to ensure stable currents for all LEDs.

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LED driving device that reduces flicker and improves dimming resolution in LED lighting applications. It allows smooth brightness adjustment and eliminates visible steps in dimming. The device uses pulse width modulation (PWM) to control the LEDs, but instead of using a single PWM signal, it combines multiple signals with different duty cycles within a cycle. This reduces the pulsating current and flicker when shooting video with fast frame rates. The device calculates the required PWM rates based on the dimming signal, and uses separate converter circuits for each rate.

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Reducing flickering in LED displays with regional backlight adjustment by properly switching PWM data. The method involves coordinating the VSYNC signal from the display controller with the internal oscillator in the LED driver chip. When VSYNC arrives, the driver chip completes the current PWM cycle instead of truncating it. This prevents sudden changes in duty cycle and eliminates low-frequency flicker. The driver chip calculates the correct average brightness over a full VSYNC period rather than an incomplete cycle. This ensures consistent brightness and passes professional eye protection certifications.

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Reducing audible noise from LED dimming using PWM signals. The method involves generating PWM signals for driving multiple LED channels that spreads the power supply transients due to LED currents during dimming. The PWM signals have leading edges that are fixed transitions and trailing edges that are modulated based on the duty cycle. This cancels out voltage ripple at the fixed leading/trailing edge alignments. It also disperses voltage ripple by misaligned edges.

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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.

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LED lighting device with improved flicker performance using a sequential driving method for AC power. The device reduces flicker by controlling the LED current based on the number of lit LEDs instead of voltage level. It uses a loopback compensator to charge during the first operation section and apply a second voltage in the compensation section. A driving control unit detects LED current and turns off last LED group in charge section. This provides consistent output by removing non-emission sections.

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LED display driver circuit that prevents brightness non-uniformity at low brightness levels by adjusting channel currents based on estimated brightness. The circuit has a control unit that receives brightness estimates for each channel. It then adjusts the control signals to the current control circuits based on the estimates. This compensates for channel-to-channel current variance at low brightness where the on-time is short. It can use measured current integrals from testing or receive estimates from external sources.

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LED driver using a modulation technique called stochastic frequency pulse modulation (SFPM) to dim LEDs without visible flicker, audible noise, high frequencies, or EMI. The SFPM involves randomly increasing/decreasing the duration of the high/low periods in each cycle to average out to the target dimming level. A controller sets ranges for the high/low durations based on past cycles, then randomly selects within those ranges. This avoids fixed frequencies and allows dimming without issues associated with PWM.

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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.

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