Abstract
High-bandwidth buck voltage regulator with peak current-mode control is a commonly-used scheme, especially for CPU power applications. However, the conventional single-frequency and three-frequency models are inaccurate in modeling the loop gain stability when the control bandwidth is close or higher than one-third of the converter switching frequency. A more accurate four-frequency small-signal model for a high-bandwidth buck converter with peak current-mode control is proposed in the present paper. The describing function approach is used to model the duty-cycle modulator. The effects of the four-frequency components, including the modulating frequency, the two sideband harmonics, and the switching frequency, are considered. Simulations and experiments verified the results.
Highlights
In recent years, tremendous progress has been made about the voltage regulator (VR) for powering the latest computer central processor units (CPU), which is often called the “VCore” regulator
Compared to traditional constant-frequency voltage mode (CFVM) control, current-mode control can be integrated with the above two crucial techniques required by V-Core application [1]-[3]
Previous single-frequency small-signal models of constant-frequency peak current mode (CFPCM) control have been proposed for many years [19]-[20], but it is only accurate for the case with a small control bandwidth/switching frequency ratio
Summary
Tremendous progress has been made about the voltage regulator (VR) for powering the latest computer central processor units (CPU), which is often called the “VCore” regulator. Some modeling methods [16]-[18] are stability-oriented and do not contain frequency-domain information for transient response behavior estimation Those methods are not as widely adopted in the industry by engineers as frequencydomain small-signal models do. Previous single-frequency small-signal models of CFPCM control have been proposed for many years [19]-[20], but it is only accurate for the case with a small control bandwidth/switching frequency ratio. For applications with high control bandwidth/switching frequency ratio, a two-frequency model for CFVM control. It is due to the lack of some frequency components that may affect the loop behavior when the bandwidth/switching frequency ratio is high To solve this issue, a four-frequency model has been proposed and verified to achieve small-signal model accuracy [22]. Simulations and experimental results will be used to verify the accuracy of the proposed four-frequency model
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