Practical Design of An LED Light Bulb

To make the light bulb brighter, the light emitting diodes (LEDs) are also going to have to run hotter. And hotter LEDs means the mean time to failure (MTTF) is going to be less. There are going to be two sources of heat in the LED light bulb design, the ballast and the LEDs. This chapter draws a specification, for marketing sign‐off before the design begins. There are a number of issues that are indirectly addressed in this specification. The chapter talks about total harmonic distortion (THD). While THD has long been familiar to those interested in audio, it is relatively new in the world of power conversion. The chapter provides a summary in words of how the two measures, Flicker Index (FI) and Percent Flicker (%F), are calculated. FI first finds the average light output. The chapter then finds how much of the total light is emitted above that average. % F measures the difference between the brightest light emitted and the dimmest light.