LED Drive Circuit Saturation Mode Current Stability
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Solution Overview
Problem
Traditional drive circuits for LEDs cannot supply a stable output current, leading to variable brightness due to temperature changes and voltage fluctuations, limiting their application in light systems.
Innovation Solution
A drive circuit comprising a MOS transistor and a voltage regulator, where the regulator supplies a fixed voltage to the gate electrode of the transistor to maintain it in saturation mode, ensuring a stable drive current is provided to the LEDs, regardless of temperature changes or voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional drive circuit with resistor is used to drive LEDs, then the circuit is simple in structure, but the output current is unstable and changes with temperature
Solution Approach 1:
The patent changes the operating parameter of the MOS transistor from linear mode to saturation mode. In saturation mode, the drain current becomes independent of drain-source voltage and depends only on gate-source voltage, providing stable current output regardless of temperature changes or voltage fluctuations. This parameter change resolves the contradiction by achieving current stability without significantly increasing circuit complexity.
Solution Approach 2:
The patent introduces a voltage regulator as an intermediary component to provide a stable gate voltage to the MOS transistor. This intermediary ensures that the gate-source voltage remains constant, which in turn maintains stable drain current through the LEDs. The regulator acts as a mediator that decouples the instability from the LED current, resolving the contradiction between simplicity and stability.
2Illumination intensity
If a fixed voltage is supplied to LEDs in a traditional drive circuit, then the voltage source is simple, but the current changes with temperature causing brightness variation
Solution Approach 1:
The patent changes the operational state of the MOS transistor to saturation mode, where the current is controlled by gate voltage rather than being directly proportional to drain voltage. This parameter change makes the current independent of temperature-induced resistance changes in the LEDs, thereby stabilizing both current and brightness simultaneously.
Solution Approach 2:
The patent segments the control function by separating voltage regulation from current control. The voltage regulator handles voltage stabilization, while the MOS transistor in saturation mode handles current stabilization. This segmentation allows each component to specialize in one function, achieving both voltage and current stability for consistent brightness.
3Reliability
If the voltage supplied to the drive circuit is changed, then the output current changes in a typical drive circuit, but a stable current is needed for consistent LED brightness
Solution Approach 1:
The patent exploits the saturation mode parameter characteristic of MOS transistors where drain current is independent of drain-source voltage. By operating in this parameter regime, the circuit achieves voltage tolerance - the ability to maintain stable current despite voltage fluctuations. This resolves the contradiction by making the circuit adaptable to voltage changes while maintaining current stability.
Solution Approach 2:
The MOS transistor in saturation mode acts as an intermediary between the voltage source and the LEDs. It decouples the relationship between input voltage and LED current, allowing voltage variations at the input to be absorbed by the transistor without affecting the output current. This intermediary function provides both stability and voltage adaptability.
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 ensures a consistent current flow through the LEDs, maintaining stable brightness and reducing costs by only requiring a regulator and a MOS transistor, thus overcoming the limitations of traditional drive circuits.
Implementation Method 1
The voltage regulator receives a first voltage to generate a second voltage to control the gate electrode of the transistor
Implementation Method 2
ensure this transistor operated in saturation mode to generate a drive current to drive the LEDs
Implementation Method 3
The rectifier circuit is connected to a voltage source to rectify an output voltage from the voltage source to a first voltage
Data Source
AI summary
This present invention provides a drive circuit to drive LEDs. The drive circuit comprises a transistor and a voltage regulator. The transistor is connected to the LEDs in series. The voltage regulator receives a first voltage to generate a second voltage to control the gate electrode of the transistor. The second voltage can turn on the transistor and ensure this transistor operated in saturation mode to generate a drive current to drive the LEDs.