On the selection of control-law coefficients for multiloop PWM switching regulators

An analytical investigation was performed to ascertain the explicit effects of the state-variable feedback control-law coefficients and the source variable feed-forward control-law coefficients on the stability and performance in linearized multiloop (pulse-width modulated) switching regulators. Detailed results are presented for input impedance, output current susceptibility, input voltage susceptibility and output impedance of the basic buck, boost, and buck-boost regulators. General relationships are derived for the feed-forward control-law coefficients to minimize input voltage susceptibility and the output impedance of the multiloop buck regulator. Relationships for all three regulators based on other performance measures such as output current susceptibility can be derived using the results presented. Simplified results are given for multiloop switching regulators with a conventionally implemented current loop and with a value of inductance several times greater than critical