Analog LED Driver Circuit Reduces Harmonic Distortion
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Solution Overview
Problem
LED lighting circuits using digital circuitry to measure and control AC input voltage for LEDs result in elevated harmonic distortion and power factor distortion, reducing efficiency.
Innovation Solution
A current conditioning circuit using analog components and depletion-mode MOSFET transistors to selectively route current to LED groups based on instantaneous AC input voltage, minimizing harmonic and power factor distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If digital circuitry is used to measure and control AC input voltage for LEDs, then LED lighting efficiency is improved through selective activation, but harmonic distortion and power factor distortion are elevated
Solution Approach 1:
The patent replaces digital circuitry with an analog conditioning circuit that uses continuous voltage sensing and analog switching. The conditioning circuit continuously monitors the rectified sinusoidal voltage and smoothly transitions between conducting and non-conducting states based on instantaneous voltage levels, eliminating the discrete measurement and control steps of digital systems. This analog approach maintains LED lighting efficiency while producing minimal harmonic distortion because the switching occurs naturally at the zero-crossing points of the sinusoidal waveform rather than through abrupt digital on/off commands.
2Use of energy by moving object
If digital switches are used to selectively activate LED groups based on microprocessor control, then power utilization is optimized, but total harmonic distortion increases
Solution Approach 1:
The patent implements continuous voltage sensing and continuous analog switching rather than discrete digital control. The conditioning circuit maintains a continuous connection to the rectified sinusoidal voltage source and continuously adjusts its conductivity based on the instantaneous voltage level. This continuous action allows the circuit to optimize power utilization by conducting current only when voltage exceeds the LED threshold while avoiding the abrupt transitions of digital switching, thereby reducing total harmonic distortion.
Solution Approach 2:
The patent introduces an analog conditioning circuit as an intermediary between the rectified sinusoidal voltage source and the LED groups. This conditioning circuit acts as a buffer that smooths the transition between different LED group activations. By using analog voltage division and continuous conductivity adjustment rather than direct digital switching, the intermediary circuit reduces the abrupt current changes that cause harmonic distortion while still achieving optimized power utilization through selective LED group activation.
3Measurement precision
If abrupt switching between LED groups is implemented, then control precision is improved, but harmonic distortion increases due to non-smooth transitions
Solution Approach 1:
The patent employs dynamic analog switching where the conductivity of the switching elements changes continuously rather than abruptly. The conditioning circuit uses voltage-dependent resistance or transistor conductivity that naturally transitions between states based on the instantaneous voltage level. This dynamic behavior allows precise control of which LED groups are active at any moment while ensuring smooth transitions between states, thereby maintaining control precision without generating harmonic distortion from abrupt switching.
Solution Approach 2:
The patent changes the control parameter from discrete digital on/off states to continuous analog conductivity levels. The conditioning circuit adjusts its electrical parameters (resistance, conductivity) continuously based on the instantaneous rectified sinusoidal voltage level. This parameter change enables precise control over LED group activation while ensuring that transitions occur gradually through the natural sinusoidal voltage waveform rather than through abrupt digital switching, thereby reducing harmonic distortion.
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 achieves reduced harmonic distortion and power factor distortion, enhancing the efficiency of LED lighting by smoothly transitioning between conducting and non-conducting states, maintaining high efficiency and minimizing power loss.
Implementation Method 1
A current conditioning circuit is provided for selectively routing current to various LED groups in an LED light. The conditioning circuitry includes only analog circuit components, and includes a first series interconnection of a first LED group, a first depletion MOSFET transistor, and a first resistor coupled between output nodes of a voltage rectifier and an input node of a second series interconnection of a second LED group, a second depletion MOSFET transistor, and a second resistor.
Data Source
Figure 1A~1B
Figure 1C
Figure 1D
AI summary
Conditioning circuits are provided for driving two or more LED groups using a rectified AC input voltage. The conditioning circuits uses analog circuitry to gradually and selectively activate the LED groups based on an instantaneous value of the rectified input voltage. The circuit includes a first series interconnection of a first LED group, a first transistor, and a first resistor, and a second series interconnection of a second LED group, a second transistor, and a second resistor. In one example, the second series interconnection is connected between a drain terminal and a source terminal of the first transistor, while in another example, the second series interconnection is connected between an anode of the first LED group and a source terminal of the first transistor. The first and second LED groups are selectively activated by the rectified voltage applied across the first series interconnection.