The Basic Objectives of Electrical Conversion
The function of a power conversion circuit is to control the energy flow between a given electrical source and a given load. A converter must manipulate flow, but should not consume energy. The reason is simple. Since a power converter appears between a source and a load, any energy used within the converter is lost to the overall system. To be useful, a converter should have a high input-output energy efficiency. This is the first and primary design objective in power electronics:
Efficiency Target → 100 %
We seek lossless process to implement converters
A power converter connected between a source and a load also affects system reliability. If the energy source is perfectly reliable (it is on all the time), then a failure in the converter affects the user (the load) just as if the energy source itself fails. An unreliable power converter creates an unreliable system. Reliability requirements are extreme in many applications. To put this into perspective, consider that a typical U.S. household loses electric power only a few minutes a year. Energy is available 99.999% of the time. A converter must be better than this to avoid degrading a system. As high-efficiency becomes more routine, this second reliability objective grows in importance:
Reliability Target → No Failures Over Application Lifetime
Reliability is often a more difficult objective than efficiency. Imagine just trying to prove that a circuit will not fail over decades of use. Spectacular failures are a traditional property of power supplies, and other equipment is often damaged in the process.