Many lighting ballasts use two power MOSFET switches in a configuration as shown in Figure 2. The MOSFETs alternate between driving and conducting the transformer windings. This fundamental circuit has been the industry standard for lighting ballasts for many years, but it has a few drawbacks. There is no self-start feature and light dimming capability is not part of the circuit.  Also a large transformer is needed for proper operation. New advances in driver ICs have resulted in major improvements in lighting ballasts. These circuits can drive low- and high-side MOSFETS from logic-level, ground-referenced inputs rather than needing a driver transformer. Figure 3 (on the next slide) is an example showing the various capacitors needed for the ballast circuit.