Comparison of performance of single-loop and current-injection-control for PWM converters which operate in both continuous and discontinuous modes of operation

A comparison of single-loop and current-mode controlled power converters operating in the continuous and discontinuous modes is performed using the PWM (pulse width modulation) switch model and a new, continuous-time model of current injection control (CIC). The theoretical and experimental results show a significant performance improvement that can be realized when CIC is employed in converters which operate over a wide load range. Except for the single-loop, continuous mode transient response time, all the CIC figures are equal to or better than the single-loop figures. The transient response time of CIC can be improved to be equal to or better than single-loop control by placing the compensation zero at a higher frequency. The penalty is that the system loop gain will be conditionally stable. This may not be significant, though, since the system loop gain crossover frequency is governed by the current loop. The current loop is determined by the external ramp slope.<
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