LED Driver Circuit Balancing Waveform Amplitude to Reduce Flicker
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Solution Overview
Problem
LED bulbs experience noticeable flicker when dimmed using existing dimmers designed for incandescent bulbs, due to imbalance in positive and negative portions of the AC sinusoidal wave, causing unpleasant light emission.
Innovation Solution
A method and circuit that balance the driving current waveform of LED bulbs by adjusting the amplitude and duration of the positive and negative cycles to match each other, using a triac-based dimmer and a DC to DC converter system with a decision circuit and balancing circuit to smooth out the current ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a triac-based dimmer is used to control LED bulbs, then the LED bulbs can be dimmed, but noticeable flicker occurs due to imbalance in positive and negative portions of the AC sinusoidal wave
Solution Approach 1:
A current balancing circuit is introduced as an intermediary component between the triac-based dimmer and the LED bulbs. This circuit measures the current through the LED string and actively balances the positive and negative half-cycles of the AC waveform, eliminating the flicker caused by triac operation while preserving dimming functionality.
Solution Approach 2:
The current balancing circuit employs feedback mechanisms to continuously monitor the current through the LED string and adjust the balancing accordingly. By measuring the actual current and comparing it against the desired balanced waveform, the circuit dynamically corrects imbalances between positive and negative half-cycles, eliminating flicker.
2Illumination intensity
If the AC line voltage is clipped by a triac to control LED intensity, then dimming is achieved, but the driving current develops ripple that causes flicker
Solution Approach 1:
The current balancing circuit serves as an intermediary that processes the clipped AC waveform from the triac, measuring and actively balancing the current to produce a stable driving waveform for the LEDs, thereby eliminating ripple-induced flicker while maintaining dimming control.
Solution Approach 2:
The circuit dynamically changes the electrical parameters of the driving waveform by actively adjusting the current balance between positive and negative half-cycles. This parameter adjustment compensates for the clipping effects of the triac, transforming the unstable rippled waveform into a stable balanced waveform suitable for LED operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces noticeable flicker in LED bulbs by balancing the driving current waveform, shifting the flicker frequency from 60 Hz to 120 Hz, making it less perceptible to users, even in dim lighting conditions.
Implementation Method 1
LEDs emit light based on current flow through a P-N junction
Data Source
AI summary
Method and circuits for balancing a first waveform used to drive an LED are disclosed herein. The first waveform has a first cycle with a first amplitude and a second cycle with a second amplitude. An embodiment of the method includes adjusting the first amplitude of the first cycle to match the second amplitude of the second cycle, the result being a second waveform. The LED is driven with the second waveform.