LED Current Driver Feedback Correction for Battery Voltage Drift
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Solution Overview
Problem
Current driver circuits in lighting and light communication applications face challenges in maintaining a consistent current level through LEDs due to variations in battery voltage caused by charging and discharging, as well as changes in temperature and voltage demands, leading to undesirable fluctuations in output current.
Innovation Solution
A current driver integrated circuit that includes a voltage detector circuit, an Output Model Current Mirror (OMCM) circuit, a Corrected Current Mirror (CCM) circuit, a summing node reference current generator circuit, and a Corrected Current to Gate Voltage Converter (CCGVC) circuit, which work together to maintain the current level within five percent of a desired output current level over a range of output voltages by adjusting the gate voltage of the current driver transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a current driver circuit uses a reference current to set the output current level, then the current control is simple, but the output current varies significantly with battery voltage changes
Solution Approach 1:
The patent implements a feedback mechanism by detecting the output voltage and using it to dynamically adjust the reference current. The circuit monitors the voltage drop across the LED and modulates the reference current accordingly, creating a closed-loop control system that compensates for voltage variations and maintains stable output current.
Solution Approach 2:
The patent changes the reference current parameter dynamically based on the detected output voltage. Instead of using a fixed reference current, the circuit adjusts the reference current magnitude in response to voltage changes, thereby maintaining constant output current despite varying battery voltage conditions.
2Adaptability or versatility
If the battery voltage varies due to charging and discharging, then the power supply adapts to different states, but the output voltage and output current vary significantly
Solution Approach 1:
The feedback mechanism detects output voltage variations caused by battery charging and discharging states and automatically adjusts the reference current to compensate. This ensures that despite the battery adapting to different charge states, the output current remains stable and consistent.
Solution Approach 2:
The circuit takes preliminary anti-action by pre-adjusting the reference current in response to detected voltage variations before they can cause significant output current deviation. This proactive compensation prevents output current instability rather than merely reacting to it.
3Adaptability or versatility
If different applications require different battery voltages, then the system is versatile, but the output current level becomes difficult to maintain
Solution Approach 1:
The patent dynamically changes the reference current parameter based on the detected output voltage, which varies across different applications and battery voltages. This adaptive parameter adjustment ensures precise output current control (within five percent) regardless of the specific application or battery voltage level.
Solution Approach 2:
The current driver circuit is designed with universal functionality to operate across a wide range of battery voltages and applications. The feedback-based reference current adjustment mechanism provides a unified solution that maintains precise output current control across all operating conditions, eliminating the need for application-specific circuit configurations.
Data Source
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AI summary
A current driver integrated circuit (IC) is coupled to control current flow through a diode. In one example, the diode is a Light Emitting Diode (LED) having an anode coupled to a supply node supplied by a battery and a cathode coupled to a drive terminal of the current driver IC. During operation the current driver IC is enabled and sinks an output current from the supply node, through the LED, through the drive terminal, and onto a ground node. As current flows through the LED, the battery is discharged. Changes in battery voltage cause an output voltage between the cathode of the LED and the ground node to change. Despite variations in output voltage, the current driver IC maintains a current level of the output current to be within five percent of a desired output current level across an output voltage range of at least 2V.