4. Waveshaping Techniques to Improve
Switching Power Supply Efficiency
135
Much research and work has been done in the past two decades to improve the
efficiency of the basic PWM switching power supply. During the 1980s, the
improvements largely took the form of improved semiconductor devices and
ferrite materials. Their contributions allowed the switching frequencies to rise
and their efficiency to improve about another +5 to +10 percent over the bipolar
transistor-based designs. The most recent techniques include the use of reso-
nant and charge redirection techniques. These modifications along with the use
of synchronous rectifiers (where applicable), allowed ...