Dimmable Analog AC Circuit for LED Groups
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Solution Overview
Problem
Analog AC circuits used in LED lighting face challenges in reducing the gap between peak and valley currents during dimming operations, leading to flicker issues and inefficiencies, particularly in horticulture applications where low green light levels are beneficial for plant growth.
Innovation Solution
A circuit design featuring a series interconnection of LED groups with depletion-mode MOSFET transistors and ancillary circuitry that includes a capacitor to ensure continuous current flow to the first LED group, maintaining light emission during dimming and reducing harmonic distortion and power factor distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If analog AC circuit operates with standard dimming, then energy efficiency is improved, but current gap between peak and valley increases causing flicker
Solution Approach 1:
The patent applies the continuity of useful action principle by introducing an ancillary circuit with a capacitor that continuously charges during the AC cycle and discharges during zero-crossing periods to maintain continuous current flow through the LED group. This eliminates the interruption of light output during dimming operations while preserving energy efficiency, directly resolving the contradiction between energy savings and flicker-free operation.
2Device complexity
If AC to DC converter and PWM device are eliminated, then device complexity is reduced, but current control precision during dimming deteriorates
Solution Approach 1:
The patent introduces an ancillary circuit with a capacitor as an intermediary element that mediates between the simple analog AC circuit and the requirement for precise current control during dimming. The capacitor stores and releases energy to smooth current variations, providing precise current control without requiring complex converters or PWM devices, thus resolving the contradiction between simplicity and control precision.
3Use of energy by moving object
If current is reduced during dimming, then energy consumption is lowered, but light output continuity deteriorates
Solution Approach 1:
The patent applies preliminary action by having the capacitor charge during periods when the LED group is receiving sufficient current, storing energy in advance. During dimming periods when current would normally drop, the pre-charged capacitor discharges to maintain continuous current flow. This preliminary energy storage ensures light output continuity while allowing energy consumption to be reduced during non-critical periods.
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 provides improved dimming functionality, reduces flicker, and ensures continuous light output, enhancing plant growth by maintaining low green light levels while minimizing harmonic and power factor distortions.
Implementation Method 1
a capacitor electrically connected to an ancillary transistor that is provided a biasing voltage from an ancillary resistor such that current is continuously provided to the first series interconnection throughout operation
Implementation Method 2
A first series interconnection of a first light-emitting diode (LED) group and a second series interconnection of a second LED group that are in series. The first series interconnection has a cathode coupled to a drain terminal of a first transistor and a source terminal of the first transistor is coupled to a first terminal of a first resistor to provide biasing voltage for the first transistor
Implementation Method 3
a first light-emitting diode (LED) group and a second series interconnection of a second LED group
Implementation Method 4
The first series interconnection continuously emits light during operation of the circuit
Data Source
AI summary
An analog AC circuit for light emitting diode (LED) groups that provides continuously emitted light through a dimming process from 100% relative light output to 5% of relative light output. The analog AC circuit utilizes ancillary circuitry that bypasses a first series interconnection of a first LED group and presents a capacitor electrically connected to an ancillary transistor to provide constant current at above a current threshold to cause the first LED group to continuously emit light even through a dimming process.