LED Driver Boundary Conduction Mode Single Input Feedback
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Solution Overview
Problem
Conventional LED drivers require multiple input terminals for feedback signals to operate in boundary conduction mode, increasing complexity and cost, and often lead to inefficiencies due to additional dissipation from sensors and voltage level shifts.
Innovation Solution
An LED driver with a single input terminal for feedback, utilizing a current sensing circuit with capacitance to indicate zero-crossing and current levels, reducing dissipation and complexity by integrating the feedback signal through a control unit connected to both the high and low voltage terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple current or voltage sensors are used to provide feedback signals for boundary conduction mode operation, then the power converter can be operated in boundary condition mode with reduced dissipation, but the complexity of the control unit increases and the choice of control unit is limited
Solution Approach 1:
The patent combines multiple feedback signal functions into a single input terminal. The current sensing circuit integrates both the zero-crossing detection signal and the current level feedback signal, allowing the control unit to receive all necessary feedback information through one terminal rather than multiple separate terminals. This merging approach reduces control unit complexity while maintaining boundary conduction mode operation capability.
Solution Approach 2:
The single input terminal of the control unit is designed to handle multiple functions: receiving zero-crossing detection signals, receiving current level feedback signals, and providing timing information for switch control. This multi-functional design eliminates the need for separate dedicated terminals for each feedback function, thereby reducing overall system complexity.
2Adaptability or versatility
If multiple input terminals are provided on the control unit for feedback signals, then boundary conduction mode can be implemented, but the cost and complexity of the control unit increases
Solution Approach 1:
The patent merges the functionality of multiple input terminals into a single input terminal by designing a current sensing circuit that consolidates zero-crossing detection and current level feedback into one signal path. This allows the control unit to operate in boundary conduction mode without requiring multiple dedicated input terminals, thereby reducing configuration complexity.
3Stability of the object's composition
If conventional LED drivers operate at high switching frequency to provide continuous current, then the current supply is substantially continuous, but the switching losses increase and efficiency decreases
Solution Approach 1:
The patent implements boundary conduction mode where the power converter operates in periodic cycles rather than continuous high-frequency switching. The converter switches on at zero-crossing points and operates until a predetermined current level is reached, then switches off. This periodic operation with extended on-times reduces switching frequency and associated losses while maintaining adequate current supply to the LED fixture.
Solution Approach 2:
The patent changes the operating parameters of the power converter by transitioning from continuous high-frequency switching to boundary conduction mode with lower switching frequency. By adjusting the switching timing to occur at zero-crossing points and extending the on-time duration, the system achieves reduced switching losses while maintaining current continuity through the periodic nature of the operation.
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
Enables efficient operation in boundary condition mode with reduced switching losses and simplified control unit design, allowing for cost-effective and robust LED driver implementation.
Implementation Method 1
a second capacitance connecting the second terminal and the input terminal for providing the feedback signal when the switch is open
Implementation Method 2
a current sensor arranged to provide, when the switch is closed, the feedback signal representing a level of the current supplied to the LED fixture
Data Source
AI summary
An LED driver for controlling a current supplied to an LED fixture, the LED driver including a switched mode power supply (SMPS) for providing the current to the LED array and a control unit for controlling a switch of the SMPS. The control unit includes an input terminal connected to a current sensing circuit and the switch is connected to the LED fixture at a node downstream of the LED fixture. The current sensing circuit of the LED driver provides a feedback signal to the input terminal of the control unit; the current sensing circuit including a current sensor arranged to provide, when the switch is closed, the feedback signal representing a level of the current supplied to the LED fixture; the current sensing circuit further providing the feedback signal indicating a zero-crossing of the current supplied to the LED fixture when the switch is open.