Analysis of the Sideband Effect on the Stability of the Voltage-Mode-Controlled Boost Converter

Although the small-signal model of the loop gain, which quantitatively include the sideband effect, have been proposed in the resent research, all results are for buck converters. When applying these results for the Voltage-Mode-Controlled(VMC) boost converter, the instability phenomenon, in some cases the converter with the leading-edge modulation is stable while with the trailing-edge modulation it becomes unstable, still couldn't be explained as the case that using average model. In order to indicate why these results aren't suitable for boost converter, it is firstly pointed out that the high-frequency characteristic of the duty ratio-to-output transfer function ( GvdS), which the average model fails to describe, could affect the low-frequency performance of the loop gain and the modulator. Then, we give the theoretical prediction of Gvd(S)) by using the describe function method, which has excellent agreement with the measured results especially in the high-frequency region. By using the corresponding obtained loop gain, the aforementioned phenomenon would be explained. The work demonstrates significant importance of the research into the sideband effect on the stability for the DC/DC converter and the DC system.