LED Drive Circuit Eliminating Dead Loads for Flicker-Free Dimming
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Solution Overview
Problem
Existing LED drive circuits face inefficiencies due to the need for fixed loads, leading to reduced efficiency and issues with startup flickering and limited dimming range, especially when using phase-control dimming methods.
Innovation Solution
An LED drive circuit comprising a rectifier circuit, a converter with a switching element, and a controller that receives phase-control dimming signals and current sampling signals to control the LED current, eliminating the need for dead loads and allowing for wide-range linear dimming without flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed load (dead load) is added to hold minimum breakover current during conduction, then phase angle signal detection accuracy is improved, but circuit loss increases and efficiency decreases
Solution Approach 1:
The patent removes the fixed load (dead load) component from the circuit by using the LED itself as the load. The controller directly controls the switching element to regulate current through the LED without requiring additional resistive loads, thereby eliminating the energy loss associated with dead loads while maintaining phase angle detection capability through alternative means.
Solution Approach 2:
The LED serves multiple functions: it is both the load that consumes power and the indicator that demonstrates the circuit operation. The controller uses the LED's own characteristics and the phase-control dimming signal to detect phase angle information without requiring separate fixed load components, achieving both power consumption and signal detection functions through the LED itself.
2Ease of operation
If the conduction angle is filtered and converted into DC signal with delay time, then dimming control is achieved, but startup flickering occurs due to delayed response
Solution Approach 1:
The controller directly responds to the phase-control dimming signal at its leading edge without requiring delayed filtering and DC conversion. By acting immediately on the incoming signal to control the switching element, the system eliminates the delay inherent in traditional filtering approaches, preventing startup flickering while maintaining dimming control functionality.
Solution Approach 2:
The controller implements a feedback mechanism that continuously monitors the phase-control dimming signal and adjusts the switching element control accordingly. This real-time feedback allows the system to respond immediately to signal changes without the delay caused by filtering and DC conversion, eliminating startup flickering while maintaining stable dimming control.
3Measurement precision
If complex reference sampling circuits are used to convert conduction angle to DC signal, then dimming signal accuracy is improved, but device complexity increases
Solution Approach 1:
The patent eliminates complex reference sampling circuits by directly using the phase-control dimming signal as the control reference. The controller processes the incoming AC phase-control signal directly through its control logic, extracting the necessary dimming information without requiring additional filtering, rectification, or DC conversion circuits, thereby maintaining signal accuracy while dramatically reducing circuit complexity.
Solution Approach 2:
The patent replaces traditional analog filtering and DC conversion hardware with a digital control approach. The controller uses its internal processing capabilities to interpret the phase-control dimming signal directly, substituting complex analog reference sampling circuits with simpler digital signal processing, thereby maintaining dimming accuracy while reducing overall device complexity.
Data Source
AI summary
An LED drive circuit and drive method thereof are provided. The drive circuit comprises: a rectifier circuit receiving a phase-control dimming signal with a conduction angle, and outputting a rectified signal; a converter comprising a switching element, with an input end coupled to the rectifier circuit and an output end coupled to an LED; and a controller having a first input end receiving the rectified signal, a second input end receiving a first sampling signal and an output end outputting a control signal according to the rectified signal and the sampling signal; wherein the switching element receives the control signal from the controller, thus executing an on/off operation to control current flowing through the LED.