LED Driver Dimming Curve Shaping for Phase-Cut Dimmer Compatibility
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Solution Overview
Problem
LED light sources connected to conventional phase-cut dimmers exhibit a linear dimming curve, which is not compatible with the human eye's logarithmic response to light intensity, unlike incandescent lamps with their exponential dimming curve, leading to undesirable lighting effects.
Innovation Solution
A driving circuit that shapes the current through the LED light source based on the average voltage of the rectified signal to produce a non-linear dimming curve, mimicking the incandescent curve at low light levels and the LED curve at higher levels, using a switched mode power supply and voltage sensor to control the current amplitude and on-time, thereby emulating the desired dimming behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional phase-cut dimmer is used with an LED light source, then the LED can be dimmed, but the dimming curve becomes linear which is incompatible with human eye sensitivity
Solution Approach 1:
The patent applies parameter changes by modifying the current waveform parameters (amplitude and duration) based on the detected voltage level. The controller adjusts the LED current parameters dynamically during each AC cycle to transform the linear dimming response into a non-linear curve that matches human eye sensitivity characteristics.
Solution Approach 2:
The patent replaces the mechanical/incandescent-based exponential dimming curve with an electronically controlled non-linear dimming curve. By using a controller that processes voltage detection and generates shaped current pulses, the system substitutes the natural exponential behavior of incandescent lamps with an electronically synthesized non-linear response.
2Reliability
If constant current is provided to LED light source, then reliable operation is achieved, but the dimming behavior does not match incandescent lamp characteristics
Solution Approach 1:
The patent implements periodic action by synchronizing the LED current pulses with the AC mains voltage cycles. Within each half-cycle, the controller applies shaped current pulses whose amplitude and duration are modulated according to the instantaneous voltage level, creating a periodic dimming pattern that produces the desired non-linear overall dimming curve.
Solution Approach 2:
The patent applies dynamics by transitioning from static constant current to dynamic current modulation. The controller continuously adjusts the current amplitude and pulse width based on real-time voltage detection, making the current supply adaptive and dynamic rather than fixed, thereby achieving both reliability and non-linear dimming response.
3Use of energy by stationary object
If LED light source replaces incandescent lamp, then power consumption and heat generation improve, but compatibility with phase-cut dimmers deteriorates
Solution Approach 1:
The patent introduces an intermediary component - the controller with voltage detection and current shaping circuitry - that mediates between the phase-cut dimmer and the LED driver. This intermediary processes the dimmer's voltage modulation and transforms it into appropriate current commands for the LED, enabling compatibility while maintaining LED efficiency advantages.
Solution Approach 2:
The patent achieves universality by designing a dimming control system that can work with conventional phase-cut dimmers while driving LED light sources. The controller performs multiple functions: voltage detection, dimming level determination, current shaping, and LED driver control, making the system adaptable to both LED technology and traditional dimming infrastructure.
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 allows the LED light source to exhibit a dimming curve that is more compatible with human eye sensitivity, providing a retrofit solution for dimmable lighting applications using conventional phase-cut dimmers, ensuring a smooth transition between low and high light levels.
Implementation Method 1
a rectifier (22) connected to the output of the phase-cut dimmer for converting the phase-cut signal into a rectified signal
Data Source
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AI summary
The present invention relates to a driving circuit (100) connected to a conventional phase-cut dimmer. A LED light source (30) is driven by a switched mode power supply (26), which is powered by the mains voltage through a phase-cut dimmer (10) and a rectifier (22). The current through the LED light source (30) is reduced according to the voltage level of the average rectified voltage Vin detected by a voltage sensor (24) and the on time limitation of the switched mode power supply (26). The current amplitude will be increasingly reduced towards the low voltage levels of Vin, namely towards the low dimmer knob levels. Thereby, the invention allows a LED light source driving circuit (100) connected to a conventional phase-cut dimmer to readily make the dimming curve of the LED light source (30) non- linear for being more compatible with the human eye sensitivity.