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Power Supplies for LED Driving by Steve Winder

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CHAPTER 4 Linear Power Supplies

4.1 Introduction

Linear power supplies for driving LEDs are preferred for a number of reasons. The complete absence of any EMI radiation is one important technical reason. Lowest cost is an important commercial reason. However, they also have disadvantages: in some applications they have low efficiency and hence the introduction of thermal problems; in other applications, such as when powered from the AC mains supply, they have the disadvantage of large size.

4.1.1. Voltage Regulators

Many voltage regulators are based on the LM317 originally from National Semiconductor, but which is now made by a number of manufacturers. Inside the LM317 are: (1) a power switch, which is an NPN transistor; (2) a voltage reference ...

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