Voltage Controlled LED Circuit for Dynamic Brightness
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Solution Overview
Problem
Current LED drive circuits are inadequate for dynamic brightness control, particularly in high-power LED applications like digital micro-mirror device image projection systems, as they fail to provide a wide range of brightness control, and are often complex, costly, and slow.
Innovation Solution
A voltage-controlled light emitting diode (VCLED) circuit using a field effect transistor (FET) as a current sink, an operational amplifier, and a current sense network, which allows for dynamic and programmable brightness control through a variable voltage control signal, enabling selective adjustment of LED brightness and supporting high-speed applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current LED drive circuits are used to stabilize LED operation, then LED brightness stability is improved, but dynamic brightness control capability deteriorates
Solution Approach 1:
The patent implements a voltage-controlled current sink using a FET whose gate voltage can be dynamically adjusted to control LED brightness. The system transitions from static current stabilization to dynamic brightness control by applying a control voltage to the FET gate, enabling real-time adjustment of LED current and brightness levels while maintaining stable operation through feedback control.
2Reliability
If complex current control circuits are used to achieve stable LED operation, then brightness stability is improved, but device complexity increases
Solution Approach 1:
The patent combines the current control function and brightness regulation function into a single integrated circuit block. The voltage-controlled current sink merges the FET-based current regulation with the operational amplifier feedback mechanism, eliminating the need for separate complex control circuits while achieving both stability and dynamic control in one unified structure.
3Device complexity
If traditional LED drive circuits are used, then circuit simplicity is maintained, but brightness control range deteriorates
Solution Approach 1:
The patent extends the brightness control range by utilizing the voltage-controlled characteristics of the FET. By varying the gate-source voltage parameter, the circuit achieves a wide dynamic range of LED brightness control from low to high levels. The operational amplifier feedback ensures that this extended range is maintained with proper stabilization, allowing brightness adjustment beyond what traditional fixed-current circuits can provide.
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 VCLED circuit achieves a wide range of brightness control, reduces complexity and cost, and supports high-speed operations with lower power consumption and improved heat performance, maintaining image quality by dynamically adjusting LED brightness in high-power applications.
Implementation Method 1
A voltage controlled light emitting diode (VCLED) circuit using a field effect transistor (FET) as a current sink
Implementation Method 2
an operational amplifier, and a current sense network, which allows for dynamic and programmable brightness control through a variable voltage control signal
Implementation Method 3
an operational amplifier, and a current sense network
Data Source
AI summary
A device (300) includes a driver circuit (200) having a field effect transistor (FET) (30), acting as a current sink, a current sense network (10), an operational amplifier (opamp) (20), and a light emitting diode (LED) (40). Current sense network (10) is connected to the source electrode (32) of FET (30), as well as to the inverting input terminal (22) of opamp (20). The non-inverting input terminal (24) of opamp (20) is coupled to a variable voltage control signal source (VDAC) (110). The output terminal (26) of opamp (20) is coupled to the gate electrode (36) of FET (30). LED (40) is connected to the drain electrode (34) of FET (30). The brightness of LED (40) is controlled by varying the amplitude of the VDAC control signal, and on/off status is controlled by a switch S1 disposed between the output terminal (26) of opamp (20) and the FET (30).