The whole point of an LLC resonant converter is to maximize efficiency. If you can do that without boosting the cost and size of your device, that’s even better. And if you can do all those things quickly and get your product to market in a timely manner, you’ve hit the jackpot. Once you’ve decided to configure an LLC resonant converter, you still have a lot of decisions to make. One way to cut system size and cost is to integrate the leakage inductor with the transformer, turning an ordinary transformer into an LLC transformer. A standalone inductor can take up a lot of space, so by integrating the series inductor as leakage inductance in a transformer, you can reduce the size of two separate components by about a third. And between component cost and assembly cost, you can reduce the cost of a separate inductor by 75 percent.
Getting just the right LLC transformer goes hand-in-hand with process capability. LLC designs can be a challenge and, too often, become a time-consuming, trial-and-error process. An extremely cost effective approach is to use finite element analysis (FEA) to develop a virtual design, thus eliminating a lot of time-consuming trial and error and unnecessary prototypes. Be warned, however, that FEA analysis, and FEA software in general, works best in the hands of an experienced LLC transformer designer. In the right hands, FEA analysis reduces the guesswork, often generating a prototype design—leakage inductance, design capacitance, winding configuration, and so on—that hits the mark the first time. The result is an LLC resonant converter that matches the engineer’s design specs, minimizes device size, wrings out avoidable cost, and does it all without slowing down development and manufacturing.