LED Control Circuit Harmonic Distortion Reduction
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Solution Overview
Problem
Direct AC drive (DACD) circuits for LEDs often result in distortion of the input current from the AC line, failing to meet International Electro-technical Commission (IEC) distortion specifications, such as IEC6000-3-2.
Innovation Solution
The proposed solution involves an LED control circuit with multiple current regulator circuits and an adjustable reference circuit that regulate LED currents based on the AC input signal waveform, reducing harmonic distortion by adjusting the current flow in response to the AC signal's varying values, thereby minimizing total harmonic distortion in the AC line current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct AC drive circuit is used to control LED, then circuit complexity is reduced, but total harmonic distortion of AC line current increases and IEC specifications are not met
Solution Approach 1:
The control circuit is divided into multiple independent current regulator circuits, each responsible for a specific LED or LED group. Each regulator circuit independently controls current to its LED during specific portions of the AC cycle, preventing harmonic distortion while maintaining relatively simple individual circuit designs.
Solution Approach 2:
The circuit dynamically switches between different current regulator circuits based on the AC input signal waveform. Each regulator circuit is activated during specific portions of the AC cycle when the signal exceeds certain thresholds, allowing the system to adapt to varying AC conditions and minimize harmonic distortion.
2Reliability
If multiple current regulator circuits are used to reduce harmonic distortion, then IEC compliance is improved, but device complexity increases
Solution Approach 1:
The control circuit is divided into multiple independent current regulator circuits, each responsible for a specific LED or LED group. Each regulator circuit independently controls current to its LED during specific portions of the AC cycle, preventing harmonic distortion while maintaining relatively simple individual circuit designs.
Solution Approach 2:
Multiple current regulator circuits are merged into a single integrated control system that shares common components such as the AC input signal receiver, reference circuit, and control logic. This consolidation reduces overall device complexity while maintaining the harmonic distortion reduction benefits of multiple regulators.
Data Source
AI summary
In an embodiment, an LED control circuit may include a first circuit configured to form a reference signal having a waveform of a rectified ac signal. The LED control circuit may also include a first regulator circuit configured to regulate a first LED current from a first LED during a first portion of the reference signal to have a waveshape that follow the reference signal waveform but not receive the first current during a second portion of the reference signal. The LED control circuit may also include a second regulator circuit configured to regulate a second current from the first LED and from a second LED during the second portion of the reference signal to have a waveshape that follows the reference signal waveform.