Current-Limited LED Circuits for Stable AC and DC Operation
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Solution Overview
Problem
LEDs driven by AC power face issues with flicker and reduced lifespan due to varying current and heat levels, and DC power systems suffer from complete failure when one LED burns out, with resistors providing inadequate current control and energy waste.
Innovation Solution
Incorporating current limiting diodes in LED circuits to maintain a constant current level, allowing LEDs to operate during both phases of AC power and enabling DC power operation with polarity reversal to utilize all LEDs, and integrating these circuits into chips or packages for various lighting applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If AC power is used to drive LEDs, then the lifespan of LEDs is extended by turning them on and off during AC cycles, but flicker occurs due to voltage variations and current control issues
Solution Approach 1:
A current limiting diode is introduced as an intermediary component in series with the LED circuit. This diode actively regulates the current flowing through the LEDs during AC cycles, preventing uncontrolled current surges when voltage rises and ensuring stable operation when voltage drops, thereby eliminating flicker while maintaining extended LED lifespan through AC-powered operation
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing a current limiting diode that dynamically adjusts current levels based on AC voltage variations. This parameter control ensures that current remains within safe operating limits regardless of AC voltage fluctuations, resolving the flicker issue while preserving the lifespan benefits of AC-powered LED operation
2Reliability
If a resistor is placed in series with the LED circuit to control current, then some current protection is provided, but energy is wasted and heat levels increase
Solution Approach 1:
The patent replaces the passive resistor-based current control mechanism with an active current limiting diode. Unlike resistors that continuously dissipate energy as heat regardless of current levels, the current limiting diode actively regulates current flow, providing protection only when necessary and minimizing energy waste and heat generation under normal operating conditions
Solution Approach 2:
The current limiting diode provides self-regulating current control without requiring external control circuits or continuous energy input. The diode inherently limits current based on its electrical characteristics, providing automatic current protection while minimizing energy consumption and heat generation, unlike resistors that continuously waste energy
3Duration of action of moving object
If DC power is used with LEDs connected in series strings, then continuous operation is achieved, but complete failure occurs when one LED burns out
Solution Approach 1:
The patent segments the LED circuit into multiple parallel branches, each containing series-connected LEDs. This segmentation ensures that if one LED fails in one branch, current can continue to flow through other parallel branches, maintaining partial system operation and improving overall reliability while preserving continuous operation capabilities
Solution Approach 2:
The patent enables recovery of system functionality after LED failure by redirecting current through alternative parallel paths. When one LED burns out, the circuit automatically recovers by channeling current through remaining functional LEDs in parallel branches, extending system operational life and reducing complete failure scenarios
4Illumination intensity
If current is increased to make LEDs brighter, then light output increases, but heat production increases reducing LED efficacy and lifespan
Solution Approach 1:
The current limiting diode acts as an intermediary that decouples the relationship between voltage input and current through the LED. It ensures current remains at optimal levels for light output while preventing current surges that would generate excessive heat, thereby maintaining brightness without compromising LED lifespan through thermal management
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 extends LED lifespan and reduces flicker by maintaining consistent current, and allows AC and DC power compatibility, doubling the effective life of DC-powered systems by utilizing both forward and reverse biased LEDs.
Implementation Method 1
The circuit may include a constant current or current limiting diode in order to substantially maintain a constant and an 'upper limit' of current within the circuit
Implementation Method 2
LEDs are semiconductor devices that produce light when a current is supplied to them
Implementation Method 3
LEDs emit light based on the amount of current passing through them
Implementation Method 4
some of the LEDs operate during the positive phase of the AC power cycle and some LEDs operate during the negative phase of the AC power cycle
Implementation Method 5
it is known in the art to place a resistor in series with the LED circuit
Implementation Method 6
A resistor will also waste energy and raise heat levels within the circuit
Data Source
AI summary
A lighting device and a lighting system having reversed biased LEDs are disclosed. In an example, a lighting system includes a driver integrated circuit configured to output a DC voltage and at least one LED circuit having at least two LEDs. The at least one LED circuit is electrically configured so that a first LED in the at least one LED circuit is electrically connected to and forward biased by the driver integrated circuit and a second LED in the at least one LED circuit is electrically connected to and reverse biased by the driver integrated circuit. The lighting system also includes a switching circuit configured to switch a biasing of the first LED and the second LED in the at least one LED circuit after receiving a signal from a sensor.