LED Current Sensing Circuit Using Matched Transistors
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Solution Overview
Problem
Conventional LED current sensing circuits face challenges in efficiently controlling small reference resistors, leading to inefficiencies and difficulty in precisely managing LED current, especially in portable devices where voltage fluctuations are common.
Innovation Solution
A current sensing circuit utilizing a matched transistor group, operation amplifier, and current source to sense and adjust LED currents, replacing small reference resistors with larger resistance values, thereby improving control loop efficiency and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a small reference resistor is used to reduce power consumption, then power consumption is reduced, but manufacturing precision and control precision deteriorate
Solution Approach 1:
The patent changes the resistance value parameter from small to large (10kΩ to 1MΩ), which improves manufacturing precision and control precision while maintaining low power consumption through the transistor switching mechanism
Solution Approach 2:
The transistor T11 automatically switches the transistor group on or off based on the control signal, eliminating the need for manual control and improving the efficiency of the control loop
2Ease of operation
If a transistor is added to control current cutoff, then current control capability is improved, but device complexity and control loop efficiency worsen
Solution Approach 1:
The transistor group serves multiple functions: it acts as a switch for current cutoff, a current mirror for sensing, and a control element for brightness adjustment, eliminating the need for separate control circuits
Solution Approach 2:
The patent combines the current sensing function and current control function into a single transistor group, merging multiple functions into one circuit block to reduce overall complexity
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 enhances the precision and efficiency of LED current control, allowing for better management of LED brightness and reducing power consumption, while being resilient to small voltage fluctuations.
Implementation Method 1
a matched transistor group, having a first current path coupled to the load device for sensing the load current and a second current path for generating a first current according to the load current
Implementation Method 2
an operation amplifier, coupled to the first and second current paths
Implementation Method 3
a current source, having a third current path coupled to the second current path and a fourth current path for generating a second current according to the first current, the second current indicating conductive condition of the load device
Data Source
AI summary
A current sensing circuit for sensing a current flowing through a LED bank and a driver circuit for driving the LED bank are provided. The current sensing circuit includes: a matched transistor group, having a first current path coupled to the load device for sensing the load current and a second current path for generating a first current according to the load current; an operation amplifier, coupled to the first and second current paths; and a current source, having a third current path coupled to the second current path and a fourth current path for generating a second current according to the first current, the second current indicating conductive condition of the load device.