In recent years, LED lighting has become very popular, experiencing rapid and significant growth, surpassing bulb technology in automotive lighting applications. However, LEDs are quite challenging to drive, and therefore LED drivers require numerous techniques and control functions compared to bulb drivers. Additionally, automotive applications demand compact and low-cost solutions that are flexible enough to interface with digital electronic control units and handle various wiring configurations and associated parasitics. Automotive lighting systems must also be robust against electromagnetic interference (EMI), a wide temperature range, overcurrent, and overvoltage phenomena. To avoid or mitigate these effects, LEDs cannot be driven by a mechanical relay; instead, a smart driver is required to control the slope of the LED current during transients, keeping it below the characteristic frequency of the wire. A compact and efficient LED driver is needed to overcome these issues and provide high flexibility to handle different LED power levels, connection typologies, and wiring parasitics, such as those caused by ringing effects generated by the resonance of wire inductance and connector capacitance. The aim of this thesis was to benchmark circuit solutions for driving LED strings in automotive environment. The activity has been carried out in collaboration with AMS Italy s.r.l. The main requirements is that driver must work in the automotive temperature range within −40° and 150°C and supplying LEDs with a current equal to 10 mA guaranteeing an accuracy of 1%, starting from a reference current of 100 μA. The first part of the work is about modelling and sizing current sources that have the purpose of delivering supply current to LEDs with the given accuracy. By knowing the main sources of mismatches of the driver, offset of the operational amplifier is modelled and its impact on the circuit is analyzed; then real amplifiers with low offset are designed. Subsequently the chopping technique is implemented for the amplifiers.
Negli ultimi anni, l'illuminazione a LED è diventata molto popolare, registrando una rapida e significativa crescita, superando la tecnologia delle lampadine nelle applicazioni di illuminazione automobilistica. Tuttavia, i LED sono piuttosto difficili da pilotare e, pertanto, i driver per LED richiedono numerose tecniche e funzioni di controllo rispetto ai driver per lampadine. Inoltre, le applicazioni automobilistiche richiedono soluzioni compatte e a basso costo, abbastanza flessibili da interfacciarsi con le unità di controllo elettronico digitale e gestire varie configurazioni di cablaggio e parasitiche associate. I sistemi di illuminazione automobilistica devono essere anche robusti contro le interferenze elettromagnetiche (EMI), una vasta gamma di temperature, sovracorrenti e fenomeni di sovratensione. Per evitare o attenuare questi effetti, i LED non possono essere pilotati da un relè meccanico; è necessario un driver intelligente per controllare la pendenza della corrente LED durante i transitori, mantenendola al di sotto della frequenza caratteristica del cavo. È necessario un driver LED compatto ed efficiente per superare questi problemi e fornire un'alta flessibilità nel gestire diversi livelli di potenza dei LED, tipologie di connessione e parasitiche di cablaggio, come quelle causate dagli effetti di ringing generati dalla risonanza dell'induttanza del cavo e dalla capacità del connettore. L'obiettivo di questa tesi è stato quello di confrontare soluzioni circuitali per pilotare stringhe di LED in un ambiente automobilistico. L'attività è stata svolta in collaborazione con AMS Italy s.r.l. I requisiti principali sono che il driver deve funzionare nell'intervallo di temperature automobilistiche da −40° a 150°C e alimentare i LED con una corrente pari a 10 mA garantendo un'accuratezza del 1%, partendo da una corrente di riferimento di 100 μA. La prima parte del lavoro riguarda la modellazione e la dimensionamento delle sorgenti di corrente che hanno lo scopo di fornire corrente di alimentazione ai LED con la precisione data. Conoscendo le principali fonti di imprecisione del driver, l'offset dell'amplificatore operazionale è modellato e il suo impatto sul circuito è analizzato; successivamente vengono progettati amplificatori reali con basso offset. Successivamente, viene implementata la tecnica di chopping per gli amplificatori.
Progettazione di un LED driver lineare per l'illuminazione automobilistica
ESPIS, MATTEO
2023/2024
Abstract
In recent years, LED lighting has become very popular, experiencing rapid and significant growth, surpassing bulb technology in automotive lighting applications. However, LEDs are quite challenging to drive, and therefore LED drivers require numerous techniques and control functions compared to bulb drivers. Additionally, automotive applications demand compact and low-cost solutions that are flexible enough to interface with digital electronic control units and handle various wiring configurations and associated parasitics. Automotive lighting systems must also be robust against electromagnetic interference (EMI), a wide temperature range, overcurrent, and overvoltage phenomena. To avoid or mitigate these effects, LEDs cannot be driven by a mechanical relay; instead, a smart driver is required to control the slope of the LED current during transients, keeping it below the characteristic frequency of the wire. A compact and efficient LED driver is needed to overcome these issues and provide high flexibility to handle different LED power levels, connection typologies, and wiring parasitics, such as those caused by ringing effects generated by the resonance of wire inductance and connector capacitance. The aim of this thesis was to benchmark circuit solutions for driving LED strings in automotive environment. The activity has been carried out in collaboration with AMS Italy s.r.l. The main requirements is that driver must work in the automotive temperature range within −40° and 150°C and supplying LEDs with a current equal to 10 mA guaranteeing an accuracy of 1%, starting from a reference current of 100 μA. The first part of the work is about modelling and sizing current sources that have the purpose of delivering supply current to LEDs with the given accuracy. By knowing the main sources of mismatches of the driver, offset of the operational amplifier is modelled and its impact on the circuit is analyzed; then real amplifiers with low offset are designed. Subsequently the chopping technique is implemented for the amplifiers.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14239/33362