Voltage-Current Converter for Linear LED Control
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Solution Overview
Problem
Conventional LED drivers face challenges in precisely controlling the current supplied to LEDs due to difficulties in specifying the operation voltage of transistors, leading to non-linear current control and inaccurate LED management.
Innovation Solution
A voltage-current converter is introduced, comprising a differential amplifier, a current mirror, and a voltage setting unit, which sets the threshold voltage arbitrarily, ensuring no current output at the threshold voltage and increasing output current with input voltage differences, thereby enhancing linearity and facilitating current load control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bias adjustment circuit applies voltage to a control terminal of a transistor in a constant current source, then the current to be supplied to the current mirror can be adjusted, but when the voltage reaches the operation voltage of the transistor, the current suddenly starts to flow, making it difficult to linearly control the current
Solution Approach 1:
The patent introduces a differential amplifier as an intermediary device between the bias adjustment circuit and the current mirror. The differential amplifier receives the control voltage and compares it with a reference voltage, producing a proportional output current that linearly controls the current mirror. This mediator transforms the abrupt transistor switching behavior into a smooth, linear control relationship, solving the non-linearity problem while maintaining ease of operation.
2Manufacturing precision
If the operation voltage of the transistor is not precisely specified, then it is difficult to linearly control the current, but precisely specifying the operation voltage limits the adaptability of the circuit
Solution Approach 1:
The patent changes the controlling parameter from the absolute voltage level (which requires precise specification) to the voltage difference between the input signal and a reference voltage. The differential amplifier responds to this voltage difference, allowing linear current control without needing to precisely specify the absolute operation voltage. This parameter transformation maintains manufacturing precision while improving adaptability to different operating conditions.
3Reliability
If a sudden current flow occurs when voltage reaches operation voltage, then the LED driver cannot properly control the LED, but increasing the voltage smoothly requires complex circuitry
Solution Approach 1:
The differential amplifier inherently provides feedback by continuously comparing the input voltage with the reference voltage and adjusting the output current accordingly. This feedback mechanism ensures that the current increases smoothly and proportionally with the input voltage, preventing sudden current flow and ensuring reliable LED control. The feedback approach achieves accurate control without requiring complex additional circuitry.
Data Source
AI summary
A current to be supplied to a load driven by the current is linearly controlled in accordance with a voltage. A voltage-current converter according to the present invention includes a differential amplifier, a first current mirror, and a voltage setting unit. The differential amplifier receives an input voltage from an input terminal and outputs a voltage in accordance with a difference between the input voltage and a threshold voltage. The first current mirror receives the voltage from the differential amplifier and outputs an output current to an output terminal. The voltage setting unit sets the threshold voltage.