Equation (3.2) reveals that the output voltage of a DC/AC resonant inverter using Pulse Width Modulation (PWM) technique can be controlled by varying the pulse width angle <5. Unlike the phase-shift control of the DC/AC inverter, the pulse width modulated control is free from the unequal current sharing and other related problems. The only disadvantage of this scheme is that the power semiconductor switches required in the design of the inverter system should have self-turn-off capability. It excludes the use of conventional SCR switches. Thanks to the new development of the MOS Controlled Thyristor (MCT) switch for high frequency, high power applications. The MCT has all the features of a conventional SCR with lower forward voltage drop (approximately IV) and self turn-off capability [6, 7]. When DC/AC resonant inverters employ MCT switches, the pulse width modulated control technique maintains the same design simplicity as the phase shift control technique while overcoming all the disadvantages (Table I). Therefore, only PWM DC/AC resonant inverter topologies are considered for the discussion in this paper. 3.3 DC/AC Resonant Inverter Topologies The above discussion indicates that the pulse width modulated resonant mode inverter topologies are the prime candidates for high power DC/AC conversion in near future space applications. This section presents and investigates a class of resonant mode inverter circuit. This class contains the following topologies: (1) Parallel Resonant Inverter, (2) Series-Parallel Resonant Inverter; (3) Hybrid Resonant Inverter. The performance of each of the above topologies is studied with respect to the following most desirable features of an inverter system: (1) full-load to no-load output voltage regulation; (2) total harmonic distortion of output voltage; and (3) full-load to reduced-load conversion efficiency. The following sub-sections present the behaviour and characteristics of each inverter. 3.3.1 Parallel Resonant Inverter Topology. Figure 5 shows a parallel resonant inverter
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