A novel adaptive-ramp ripple-based constant on-time controlled buck converter
Date Issued
2016
Date
2016
Author(s)
Kong, Le
Abstract
Ripple-based constant on-time (RBCOT) scheme has recently been adopted in the DC converters for many mobile applications. In this class of converters, an external ramp of fixed slope is often used to overcome system stability and step-load transient problems. To ensure converter proper operation, the slope of the external ramp must be properly designed according to the converter component values, and the specified operating conditions such as input voltage, output voltage, and switching frequency. However, for the up-and-coming smart power management integrated circuit (PMIC) applications, the conventional RBCOT scheme with a fixed-slope ramp simply cannot meet the requirements. For such an application, the converter output voltage and switching frequency can change due to the dynamic voltage scaling used in PMIC to improve the overall efficiency. To cope with the varying operating conditions, which keeping the converter stable with acceptable step-load response, the ramp slope must be adaptive in nature. In this thesis, a novel adaptive ramp scheme is proposed to deal with such a problem. The proposed adaptive ramp circuit is implemented in an analog circuit. It can be integrated with a conventional converter controller without additional pins. Simulations were conducted and a hardware experimental circuit was built to verify the proposed concept. This control scheme is suitable for DC converters for many mobile device applications, especially for PMIC.
Subjects
PMIC
ripple-based constant on-time
adaptive ramp
Type
thesis
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