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High Resolution DPWM Schemes (Part II) (2005)

Fig. 1. Proposed Nearly Constant Frequency Modulation (D=0.2).
Due to the limit cycle oscillations, high-frequency, high-resolution DPWM design with reasonable power consumption and die size becomes the major challenges in the implementation of digital-controlled power converters. CPES proposed constant on-time modulation to achieve much higher resolution than conventional constant frequency modulation. However, large variation of switching frequency is not desired. In order to solve this issue, CPES proposed another modulation scheme. In this scheme, on-time is regulated for coarse regulation, while switching frequency is regulated for fine regulation. This scheme can achieve nearly constant frequency with the same resolution as the constant on-time control.

Fig. 2. Conventional Constant Frequency Modulation.
Fig. 3. Proposed DPWM Scheme.
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