#### Basic Joule Thief in LTSpice I made a basic Joule Thief in LTSpice just to test the circuit topology and get a feel for the characteristics and design parameters. I added a bunch of extra libraries to my LTSpice install so I wouldn't have to go fishing for components every five minutes, but I found the pre-existing Transformer components are both 1. ideal and non-editable and 2. insufficiently defined to run simulation. I'm not an LTSpice pro so I'm probably overlooking something. ![[LTSpice - Modeling Transformers]] ##### LTSpice: Basic Joule Thief ![[Pasted image 20241122200211.png]] ##### Validating the BJT Breakdown Action ![[Pasted image 20241122202005.png]] Current trickles through Lp into the base of the NPN. The voltage (green trace) climbs until it reaches ~725mV and the BJT begins conducting. Around ~825mV the channel opens fully and begins conducting significant current. This current saturates Ls. Since Ls and Lp are arrange to antagonize eachother, this cuts off Lp and closes the conduction channel. Once the conduction channel is closed & Ls has stored up current, the only remaining path is through the LED. The inductive kickback blows the stored energy through the LED/Load, and the cycle repeats.