Nonlinear Current Driving Circuit for Temperature-Compensated Light-Emitting Devices
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Solution Overview
Problem
Proximity sensors in mobile devices face inaccurate distance measurements due to the nonlinear change in emissive power of light-emitting devices with temperature variations, leading to incorrect screen activation or music control.
Innovation Solution
A current driving circuit that generates a nonlinear driving current using a combination of reference and compensation currents, adjusted by positive and negative temperature coefficient resistors, to stabilize the output power of light-emitting devices across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-emitting device is used in a proximity sensor, then the sensor can measure distance by detecting reflected light intensity, but the emissive power changes nonlinearly with temperature variations leading to inaccurate distance measurements
Solution Approach 1:
The patent applies parameter changes by using temperature coefficient resistors (positive and negative) to dynamically adjust the driving current according to temperature variations. The resistor values change with temperature to compensate for the nonlinear emissive power changes of the light-emitting device, thereby maintaining accurate distance measurements across different temperature conditions.
Solution Approach 2:
The patent implements feedback by monitoring temperature conditions and using temperature coefficient resistors to automatically adjust the driving current in response to temperature changes. This feedback mechanism ensures that the light-emitting device operates with stable emissive power despite temperature variations, resolving the measurement accuracy issue.
2Measurement precision
If the driving current is adjusted to compensate for temperature effects, then measurement accuracy improves, but the circuit complexity increases due to multiple current generating circuits and variable resistors
Solution Approach 1:
The patent merges multiple current generating functions into a unified circuit structure. The first and second current generating circuits work together with the driver circuit to produce the compensated driving current, combining temperature compensation functionality with the existing current drive structure to minimize additional complexity while achieving accurate measurements.
Solution Approach 2:
The patent uses temperature coefficient resistors as intermediary elements between the current generating circuits and the light-emitting device. These resistors mediate the temperature compensation effect by converting temperature variations into appropriate current adjustments, simplifying the overall control mechanism while maintaining measurement accuracy.
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
Ensures accurate and stable optical measurements by compensating for temperature-induced nonlinearities in light-emitting device output power, maintaining consistent performance across a wide temperature range.
Implementation Method 1
The first current source circuit includes the positive temperature variable resistor. The first current source circuit generates a positive temperature coefficient current according to the positive temperature variable resistor.
Implementation Method 2
The second current source circuit includes the negative temperature variable resistor. The second current source circuit generates a negative temperature coefficient current according to the negative temperature variable resistor.
Data Source
AI summary
A current driving circuit configured to drive a light-emitting device is provided. The current driving circuit includes a first current generating circuit, a second current generating circuit and a driver circuit. The first current generating circuit is configured to generate a reference current. The second current generating circuit includes at least one variable resistor, and may generate a compensation current according to the at least one variable resistor. The at least one variable resistor is selected from at least one of a positive TCR resistor and a negative TCR resistor. The driver circuit is coupled to the first current generating circuit and the second current generating circuit, and configured to receive the reference current and the compensation current to serve as a driving current. The driver circuit outputs the driving current to drive the light-emitting device.