Adaptive LED Driving Circuit for Vehicle Lighting
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Solution Overview
Problem
Conventional LED driving methods for vehicle lighting face challenges in maintaining high reliability and efficiency across a wide range of input voltages, leading to heat and reliability issues, particularly in the linear driving method, where the size of the driving circuit needs to be large to handle increased power, resulting in cost and size problems.
Innovation Solution
An LED system with a driving circuit that includes a first and second LED chip connected in series, an external transistor, and a current sensing resistor, allowing for adaptive constant current control based on input voltage levels, with the driving circuit controlling the external transistor to manage power distribution and heat effectively across varying voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the linear driving method is used to reduce circuit size and cost, then the implementation circuit size is smaller and cost is lower, but the driving stability decreases rapidly according to input voltage range and reliability according to temperature is low
Solution Approach 1:
The patent applies dynamics by making the driving method adaptable to different input voltage conditions. The system dynamically switches between linear driving mode and switching driving mode based on the input voltage level, allowing the driving circuit to optimize its operation for each condition. This resolves the contradiction by enabling the circuit to maintain small size through linear driving at appropriate voltages while ensuring reliability through automatic transition to switching driving when voltage conditions require it.
2Reliability
If the switching driving method is used to achieve high efficiency and high reliability, then efficiency and reliability are improved, but the volumes of essential components are large and thus the total size of the circuit is large and cost is high
Solution Approach 1:
The patent segments the driving approach by dividing the input voltage range into different operating zones. Instead of using a single unified switching driving circuit for all conditions, the system segments the operation into: (1) linear driving mode for certain voltage ranges, and (2) switching driving mode for other voltage ranges. This segmentation allows the circuit to achieve high reliability when switching driving is necessary while avoiding the large component volumes of switching driving when linear driving suffices, thus reducing overall circuit size.
3Device complexity
If power applied to heat distribution resistor is increased to reduce the size of the driving circuit, then the IC PKG size is reduced, but the voltage applied to the heat distribution resistor is increased, so normal driving may not be achieved in low voltage range
Solution Approach 1:
The patent applies dynamics by making the heat distribution resistor's power consumption adaptive to input voltage conditions. The system dynamically adjusts the operating mode: in low voltage ranges, it operates in linear driving mode where the heat distribution resistor consumes minimal power, enabling normal driving. In high voltage ranges, it transitions to switching driving mode where the heat distribution resistor can consume higher power to reduce IC PKG size. This dynamic adaptation resolves the contradiction between minimizing IC size and maintaining broad voltage range compatibility.
Data Source
AI summary
Provided is an LED system for vehicle lighting, the LED system including: an LED package (10) including a first LED chip (11) and a second LED chip (12); and an external transistor (20) provided outside the LED package (10), and connected to a main current channel of the LED package (10) in series, wherein the driving circuit (13) is configured to drive only the first LED chip (11) with a first constant current when a level of an input voltage is lower than that of a reference voltage, or drive the first LED chip (11), the second LED chip (12), and the external transistor (20) with a second constant current when the level of the input voltage is higher than that of the reference voltage, wherein the driving circuit (13) controls the first constant current and the second constant current such that power of the first LED chip (11) when only the first LED chip (11) is driven is the same as power of the first LED chip (11) and the second LED chip (12) when all the first LED chip (11), the second LED chip (12), and the external transistor (20) connected to each other in series are driven.