LED Driver Circuit Eliminates Ripple at Low TRIAC Dimming Depth
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Solution Overview
Problem
Existing LED driver systems suffer from current ripple noise causing flickering in LED lamps, which can lead to optic nerve fatigue, and are not compatible with all TRIAC dimmers, especially at low dimming depths, requiring large and costly energy storage capacitors.
Innovation Solution
A driver circuit with current ripple control, low loop response, LEDN potential detection, start fast response, and dimming fast response mechanisms to adjust the gate-source voltage of the MOS transistor, converting current ripple to voltage ripple and eliminating low-frequency breathing sway in LED lamps due to fluctuating AC power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large energy storage capacitor is used to ensure the MOS transistor works in saturation region, then the transistor can maintain stable operation, but the cost and volume of the capacitor increase significantly
Solution Approach 1:
The patent changes the operating parameters of the MOS transistor by introducing a controlled ripple voltage component. By adjusting the ripple voltage amplitude and frequency, the transistor can maintain saturation region operation with a much smaller capacitor. The ripple voltage modifies the gate-source voltage waveform to ensure the transistor remains in saturation throughout the switching cycle, eliminating the need for oversized capacitors while maintaining reliability.
Solution Approach 2:
The patent applies periodic ripple voltage to the gate electrode of the MOS transistor. This periodic action ensures that the transistor operates in the saturation region during each switching cycle. The ripple voltage is synchronized with the switching frequency, providing continuous saturation region operation without requiring large energy storage capacitors. This periodic modulation approach maintains transistor reliability while reducing capacitor size.
2Object-affected harmful factors
If a large energy storage capacitor is used to eliminate current ripple, then the LED flickering is reduced, but the driver PCB volume increases
Solution Approach 1:
The patent changes the voltage parameters at the MOS transistor gate by superimposing a ripple voltage on the control signal. This parameter change allows the transistor to maintain proper saturation operation during the entire AC line cycle, effectively eliminating LED flickering. The ripple voltage amplitude is carefully controlled to ensure the transistor remains in saturation while minimizing the required capacitor size, thus reducing driver PCB area.
Solution Approach 2:
The patent implements a feedback mechanism where the ripple voltage is derived from the output voltage of the driver circuit. This feedback approach ensures that the ripple voltage automatically adjusts to maintain the MOS transistor in the saturation region under varying load and line conditions. The feedback-controlled ripple eliminates LED flickering while keeping the energy storage capacitor small, thereby reducing driver PCB area.
3Speed
If the loop response speed is increased to improve dynamic performance, then the system responds faster to changes, but the ripple elimination effectiveness decreases
Solution Approach 1:
The patent applies periodic ripple voltage at the MOS transistor gate at the same frequency as the AC line frequency. This periodic action creates a controlled voltage variation that counteracts the rectified ripple current. By synchronizing the ripple frequency with the line frequency, the system effectively eliminates current ripple while maintaining a slow loop response speed for stable operation. The periodic ripple voltage ensures that the transistor remains in saturation throughout each half-cycle, preventing ripple propagation to the LED.
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 circuit effectively eliminates current ripple and breathing sway in LED lamps, ensuring high efficiency, cost-effectiveness, and compatibility with most TRIAC dimmers, while maintaining a low system loop response speed for stable operation.
Implementation Method 1
adjusting a gate-source voltage of the MOS transistor, thus further adjusting a conduction impedance of the MOS transistor to convert current ripple output by a preceding-stage constant current to voltage ripple
Implementation Method 2
one end of a capacitor being connected with the constant current control circuit
Data Source
AI summary
A driver circuit for eliminating current ripple of an LED driver system comprises a current ripple control module, a low loop response module, an LEDN potential detection response module, a start fast response module and a dimming fast response module, and the driver circuit has a very low system loop response speed in a stable operating state, thus ensuring excellent output current ripple elimination function of the circuit and eliminating breathing type sway of an LED lamp at a very low frequency due to a low TRIAC dimming current.