LED Driver Current Monitoring via Feedback Voltage
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Solution Overview
Problem
Conventional LED driving devices cannot directly monitor the current flowing through the constant current driver, leading to potential false detection of voltage as current flow.
Innovation Solution
A light emitting element driving device is configured with an external terminal connected to a light emitting element, a constant current circuit including a transistor and current setting resistance, and a current detection unit that converts the current into a voltage signal using a feedback voltage, allowing direct monitoring of the current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage detection is used to detect LED terminal state, then abnormality detection function is provided, but current flowing through constant current driver cannot be directly monitored
Solution Approach 1:
The patent introduces a feedback voltage as an intermediary signal that reflects the current state. The feedback voltage is generated based on the current flowing through the constant current driver, and this voltage signal serves as a mediator to indicate the current status without directly measuring the current itself, thus resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the feedback voltage is continuously generated based on the current through the constant current driver. This feedback loop allows the system to monitor current indirectly through voltage, providing both reliable abnormality detection and accurate current monitoring capability.
2Reliability
If voltage at LED terminal is detected, then abnormality detection is enabled, but false detection may occur
Solution Approach 1:
The feedback voltage acts as an intermediary that provides a more accurate representation of the current state. By using this intermediate voltage signal that is directly related to the current through the constant current driver, the system avoids false detections that occur when directly measuring LED terminal voltage, thus improving both reliability and measurement precision.
3Measurement precision
If direct current monitoring is implemented, then current can be accurately monitored, but device complexity increases
Solution Approach 1:
The patent uses a feedback-based approach that leverages existing circuit elements to generate a feedback voltage that reflects the current state. This method achieves direct current monitoring accuracy without requiring complex additional measurement circuits, as the feedback mechanism utilizes the existing constant current driver circuitry to generate the monitoring signal.
Solution Approach 2:
The constant current driver circuit itself generates the feedback voltage that serves as the monitoring signal. The circuit serves itself by using its own internal operations to produce a signal that reflects its current state, eliminating the need for separate complex monitoring circuits and thus achieving accurate monitoring with minimal added complexity.
Data Source
AI summary
The present disclosure provides a light emitting element driving device. The light emitting element driving device includes a constant current circuit and a current detection unit. The constant current circuit includes: a first transistor including a first end, a second end and a control end connected to an external terminal; a current setting resistance connected to the second end of the first transistor; and a drive amplifier including a first input end connected to a first node to which the first transistor and the current setting resistance are connected, a second input end to which a current set voltage is applied, and an output end connected to the control end of the first transistor. The current detection unit generates a current detection signal based on a feedback voltage generated in the first node.