Constant-Current LED Driver Circuit with Adjustable Output Voltage
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Solution Overview
Problem
Existing LED driving circuits face challenges in maintaining constant-current characteristics with ±15% power supply voltage changes while minimizing power consumption and reducing wiring complexity and heat generation, especially when voltage differences between LED branches are large, and require additional open-circuit protection.
Innovation Solution
A constant-current LED driving circuit with an output voltage adjustable circuit that uses a switch conversion main circuit, output characteristic parameter sampling, and an output voltage controller to adjust the output voltage based on sampled signals, eliminating the need for resistors and comparison circuits, thereby simplifying wiring and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear adjustment current-limiting circuits are used in each LED branch, then constant-current control can be achieved, but the wiring complexity increases and power consumption rises when voltage differences between branches are large
Solution Approach 1:
The patent merges multiple independent current-limiting circuits into a single centralized current control circuit that manages all LED branches. Instead of having separate linear adjustment circuits in each branch requiring complex inter-branch wiring, the invention uses one control circuit with multiple sampling resistors to detect and regulate current across all branches, significantly reducing wiring complexity while maintaining constant-current control.
Solution Approach 2:
The centralized current control circuit serves multiple LED branches simultaneously through its multi-functional design. A single control circuit performs current sampling, comparison, and regulation for all branches using multiple sampling resistors connected to different branches, making the control system universal rather than requiring dedicated circuits for each branch.
2Reliability
If linear regulating transistors are used for current limiting in each branch, then constant-current control is achieved, but heat generation increases tremendously affecting driver reliability
Solution Approach 1:
The patent replaces the linear regulating transistor mechanism (analog/continuous control) with a switching-based control mechanism. The control circuit uses switching elements that operate in saturation or cutoff regions rather than linear regions, minimizing power dissipation as heat. The switching action provides current control while dramatically reducing the heat generation problem associated with linear regulators.
3Use of energy by stationary object
If output voltage adjustable voltage source samples minimum drain voltage through minimum value sampling circuit, then power consumption is minimized, but additional open-circuit protection circuits are required
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously samples the voltage across each sampling resistor connected to different LED branches. By comparing these sampled voltages, the control circuit identifies the branch with maximum voltage drop (indicating highest current) and adjusts the switching elements to balance currents across all branches. This feedback-based current balancing eliminates the need for separate open-circuit protection circuits while maintaining efficient power consumption.
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 constant-current control for LED loads with reduced wiring complexity and power consumption, improved reliability, and automatic adjustment for open-circuit conditions without additional protection circuits, ensuring efficient and reliable operation.
Implementation Method 1
a switch conversion main circuit, for connecting a power supply and outputting an adjustable voltage to the at least one LED load
Implementation Method 2
an output characteristic parameter sampling circuit for sampling an output characteristic parameter of the switch conversion main circuit and outputting a sampled signal of the characteristic parameter
Data Source
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AI summary
A constant-current Light Emitting Diode (LED) driver circuit is provided, and the circuit includes: an output voltage adjustable circuit and at least one path of LED load, wherein the output voltage adjustable circuit comprises: a switch converting main circuit, an output characteristic parameter sampling circuit, and an output voltage controller. The output voltage controller is used to adjust the output voltage of the switch converting main circuit according to the variation relationship between the sampling signal output by the output characteristic parameter sampling circuit and the output voltage, determine the adjustive direction of the output voltage magnitude of the switch converting main circuit according to the change of the sampling signal, adjust the magnitude of the output voltage of the switch converting main circuit according to the preset step, and finally make the output voltage equal to the voltage of one path of LED load with the highest voltage or the difference between the output voltage and the voltage of one path of LED load voltage with the highest voltage within the predetermined range. The present solution implements reducing the connection complexity and power dissipation on the base of controlling the multi-path constant-current LED.