Independent LED Control Circuit with Shunt Leakage Protection
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Solution Overview
Problem
Conventional methods for controlling light emitting diodes (LEDs) in series connections require multiple components and sources, leading to inefficiencies and increased costs, as they struggle to independently manage different electrical characteristics and prevent inadvertent excitation due to leakage currents.
Innovation Solution
A circuit with a constant current source and shunt circuit connected in series with LEDs, along with a switching circuit using transistors and bias resistors, allows for independent control of series-connected LEDs through a tri-state control signal, minimizing component count and power consumption while preventing inadvertent excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional separate control using multiple constant current sources and resistors is used, then each LED can be controlled independently, but the device complexity and component count increase significantly
Solution Approach 1:
The patent combines multiple constant current sources into a single shared current source that supplies current to multiple LEDs. The current source is coupled to a switching circuit that directs current to different LEDs based on control signals, eliminating the need for separate current sources for each LED while maintaining independent control capability.
Solution Approach 2:
The single current source serves multiple functions by being coupled to a switching circuit that can direct current to different LEDs. The current source becomes a universal supply that can control any number of LEDs depending on the switching configuration, reducing overall component count while maintaining control versatility.
2Reliability
If conventional separate control with individual resistors is used, then each LED receives appropriate current, but power consumption increases
Solution Approach 1:
The patent merges multiple individual resistor-current control paths into a single shared current source with a switching circuit. By sharing the current source and using the switching circuit to direct current to different LEDs, the system reduces the total number of resistors and power consumption while maintaining appropriate current control for each LED.
3Device complexity
If series connected LEDs are used to reduce components, then component count decreases, but inadvertent excitation due to leakage currents occurs
Solution Approach 1:
The patent introduces a switching circuit as an intermediary between the shared current source and the series connected LEDs. This switching circuit acts as a mediator that actively controls current flow to each LED based on control signals, preventing inadvertent excitation from leakage currents while maintaining the benefits of series connection and reduced component count.
4Ease of operation
If conventional control methods are used, then LED control is achieved, but PCB area and cost increase
Solution Approach 1:
The patent merges multiple control components into a single shared current source with a switching circuit, significantly reducing the number of discrete components required on the PCB. This consolidation reduces the overall PCB area while maintaining full LED control capability through the switching circuit's ability to direct current to different LEDs.
Data Source
AI summary
Described herein is a circuit and method for independent control of series connected light emitting diodes (LEDs). The circuit includes a first light emitting diode (LED) connected in series with a second LED. A current source is connected in series with the first LED and the second LED and a shunt circuit is connected in parallel with the first LED and the second LED. The shunt circuit includes a pair of serially connected resistors. The shunt circuit prevents inadvertent excitement of the LEDs due to leakage currents but minimally affect illumination characteristics of the LEDs. A pair of transistors is connected to the first LED and the second LED, respectively, and is biased using a set of bias resistors. A tri-state control signal switches on and off the pair of transistors and enables excitation of the first LED, the second LED or both via the current source.