A simple LED driver with low dimming switch stress

摘要

This paper aims to investigate the low dimming switch stress of a light-emitting diode (LED) driver. Most dimmable LED drivers contain a series dimming switch with a LED string to implement a pulse-width modulation-dimming function. However, this setup causes the dimming switch to suffer from high voltage stress in the dimming interval. To reduce the voltage stress of a dimming switch, a low switch stress scheme is presented. The dimming circuit is parallel with the LED string. Using proper arrangement and design of the parameters, the dimming circuit changes the feedback status, which results in the output driving voltage varying between a constant current and a fixed voltage operation. These two operating conditions also make the LED string turn on/off alternately and consequently and perform the dimming function. The dimming switch acts by altering the feedback path instead of cutting off the main power flow; hence, it does not need a power level switch. Details of the operating principles and design considerations are discussed in this study. A prototype boost converter was developed to verify the feasibility of the proposed low dimming switch stress LED driver. Copyright (c) 2015 John Wiley & Sons, Ltd.