LED Driver Circuit with Voltage-Based Duty Control
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Solution Overview
Problem
Conventional LED driver circuits have a large footprint and high manufacturing costs due to the requirement of multiple constant-current power supplies and external signal terminals for switch detection, and they lack effective overheat protection tailored to LED voltages.
Innovation Solution
An LED driver circuit that eliminates the need for constant-current power supplies and external signal terminals by using voltage detecting circuits and MOS transistors controlled by a controlling part to manage on-duty ratios based on terminal voltages, reducing heat generation and detecting LED element breakages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple constant-current power supplies and external signal terminals are used for switch detection, then the LED driver circuit can control multiple LED circuits, but the circuit footprint and manufacturing cost increase
Solution Approach 1:
The patent combines multiple constant-current power supplies into a single power supply unit, and integrates the switch detection function into the existing terminal structure. The controlling part uses the terminal voltages directly for detection without requiring separate external signal terminals, thereby reducing the overall circuit footprint while maintaining the capability to control multiple LED circuits.
Solution Approach 2:
The patent makes the terminal serve multiple functions: it acts as both the electrical connection terminal and the voltage detection point for switch state detection. The single power supply unit also serves multiple LED circuits, reducing the number of separate components needed and minimizing the circuit area.
2Adaptability or versatility
If multiple constant-current power supplies are used to drive LED circuits, then the LED circuits can be controlled, but the manufacturing cost increases
Solution Approach 1:
The patent merges multiple constant-current power supply functions into a single power supply unit with centralized control. This reduces the number of separate components that need to be manufactured and assembled, thereby lowering manufacturing costs while maintaining the ability to control multiple LED circuits through the unified power supply and controlling part.
3Reliability
If conventional overheat protection circuits are used, then transistor overheating is protected, but they lack effective protection tailored to LED voltages and heat generation
Solution Approach 1:
The patent implements a feedback mechanism where the controlling part continuously monitors the terminal voltages and uses this information to detect switch states and estimate heat generation conditions. Based on this feedback, the controlling part adjusts the on-duty ratios of the switching elements to prevent overheating, providing protection that is specifically tailored to the LED circuit's voltage and thermal characteristics rather than using a generic overheat protection approach.
Solution Approach 2:
The system uses its own operating parameters (terminal voltages) for both control and protection functions. The controlling part detects switch states and manages heat generation using the voltage information already available from normal operation, eliminating the need for separate protection circuits and providing integrated, precision protection.
Data Source
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AI summary
A controlling part of an LED driver circuit controls a first switch element with a first on-duty ratio if a first terminal voltage is lower than a preset first upper limit value, controls the first switch element with a second on-duty ratio smaller than the first on-duty ratio if the first terminal voltage reaches the first upper limit value, controls a second switch element with a third on-duty ratio if a second terminal voltage is lower than a preset second upper limit value, and controls the second switch element with a fourth on-duty ratio smaller than the third on-duty ratio if the second terminal voltage reaches the second upper limit value.