Constant Current LED Driver Edge Adjusting Circuit
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Solution Overview
Problem
Conventional LED drivers face issues with unstable LED current, large circuit area, and slow turn-on time due to variations in external components and transistor stacking, leading to increased power consumption and electromagnetic interference.
Innovation Solution
A constant current LED driver with an adjusting circuit, feedback circuit, operation amplifier, and edge adjusting circuit to control LED current, combined with a programmable current source using a current mirror and bit line circuitry to manage parasitic capacitance, allowing for fine step current control and rapid turn-on times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a conventional LED driver uses a cascade structure with stacked transistors, then the headroom is increased, but the circuit area and background currents increase
Solution Approach 1:
The patent divides the LED driver into two independent modes: constant current mode and switch-based mode. This segmentation allows the circuit to achieve high headroom in switch-based mode without requiring the large circuit area of a cascade structure, as the constant current mode uses a simplified architecture that eliminates the need for multiple stacked transistors while maintaining performance through mode switching
2Productivity
If the LED driver has a fast turn on time, then the productivity is improved, but the electromagnetic interference increases
Solution Approach 1:
The patent implements dynamic edge adjustment by making the rise time and fall time of the adjusting signal programmable and adjustable. This allows the system to optimize the turn-on speed for productivity while simultaneously controlling the edge rates to minimize electromagnetic interference, adapting the timing characteristics to different operational requirements
Solution Approach 2:
The patent changes the temporal parameters of the adjusting signal by providing independent control over rise time and fall time. By adjusting these time parameters, the system achieves fast turn-on for improved productivity while controlling the rate of change to reduce electromagnetic interference, effectively decoupling speed from interference through parameter optimization
3Illumination intensity
If the LED current is increased to improve brightness, then the illumination intensity is improved, but the power consumption increases
Solution Approach 1:
The patent implements dynamic switching between constant current mode and switch-based mode based on operational requirements. This allows the system to achieve high illumination intensity when needed while minimizing power consumption during normal operation, as the switch-based mode provides efficient current control without the continuous overhead of the constant current regulation circuitry
Solution Approach 2:
The patent changes the operational parameters by switching between two distinct control modes. The constant current mode provides precise current control for optimal brightness efficiency, while the switch-based mode provides high-efficiency operation for brightness applications, allowing the system to optimize the balance between illumination intensity and power consumption based on real-time requirements
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 provides stable LED current, reduces circuit area, minimizes power consumption, and mitigates electromagnetic interference by controlling rise and fall times, enabling efficient and fast LED turn-on while preventing large inrush currents.
Implementation Method 1
a current mirror, comprising a second transistor and a third transistor, configured to generate a first mirrored current flowing through the second transistor corresponding to the reference current
Implementation Method 2
an operation amplifier, comprising a first input terminal, a second input terminal, wherein the first input terminal is configured to receive a LED voltage generated by the LED, wherein the second input terminal is configured to receive the feedback voltage, wherein the operation amplifier generates the output signal according to the LED voltage and the feedback voltage
Implementation Method 3
a feedback circuit, controlled by an output signal, to generate a feedback voltage according to the first current
Implementation Method 4
an edge adjusting circuit, configured to adjust a first type of edges or a second type of edges of the first adjusting signal to generate a second adjusting signal
Data Source
AI summary
A constant current LED driver, for controlling a current flowing through a LED, comprising: an adjusting circuit, configured to generate a first current and a first adjusting signal; a feedback circuit, controlled by an output signal, to generate a feedback voltage according to the first current; an operation amplifier, configured to generate the output signal according to the LED voltage and the feedback voltage; and an edge adjusting circuit, configured to adjust a first type of edges or a second type of edges of the first adjusting signal to generate a second adjusting signal, wherein the LED is controlled by the second adjusting signal. The above-mentioned constant current LED driver can be used as a current control circuit for controlling a current flowing through a target device.