DC-DC Converter Switched-Capacitor On-Time Control
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Solution Overview
Problem
Existing DC-DC converter topologies experience output voltage ripple noise due to variable frequency, which is difficult to filter effectively, especially when dealing with variable loads and different input and output voltages.
Innovation Solution
The implementation of a DC-DC converter topology that includes a first feedback loop for adjusting the duty cycle and a second feedback loop with a switched-capacitor circuit to adjust the switching frequency, allowing for stable output node voltage ripple that can be easily filtered, using a frequency-locked loop to maintain a target switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a feedback circuit is used to adjust power based on variable load, then the converter can adapt to different loads, but output voltage ripple with variable frequency is generated that is difficult to filter
Solution Approach 1:
The patent implements an adaptive on-time control mechanism where the switch on-time dynamically adjusts based on feedback from the output voltage. The control circuit modifies the on-time parameter in response to load changes while maintaining a fixed switching frequency, thereby adapting to variable loads without generating variable frequency ripple. This dynamic adjustment of the on-time parameter (equation: Vout = (Ton/Toff) * Vin) allows the converter to maintain stable output voltage across different load conditions while keeping the ripple frequency constant for effective filtering.
2Power
If conventional DC-DC converter topology is used, then the converter can handle power conversion, but the output voltage ripple has variable frequency that adds noise to the electrical system
Solution Approach 1:
The patent changes the control parameter from duty cycle to on-time while maintaining fixed switching frequency. By controlling the on-time duration directly rather than using variable duty cycle, the converter achieves stable output voltage with constant frequency ripple. The on-time is adjusted according to the feedback voltage to maintain proper output voltage level, while the switching frequency remains fixed, resulting in reduced noise in the electrical system.
3Measurement precision
If duty cycle adjustment is used for feedback control, then output voltage can be regulated, but frequency variance of output node voltage ripple increases
Solution Approach 1:
The patent segments the control function into two independent parts: (1) on-time adjustment for output voltage regulation, and (2) fixed switching frequency maintenance. The feedback control adjusts only the on-time parameter based on output voltage error, while the switching frequency remains fixed. This segmentation allows precise output voltage regulation without affecting the switching frequency, thereby reducing frequency variance of the output voltage ripple.
Data Source
AI summary
An apparatus includes a direct-current to direct-current (DC-DC) converter having an output terminal and at least one electronic switch. The DC-DC converter also includes: 1) a first feedback loop configured to control a voltage at the output terminal by adjusting a first switching parameter of the at least one electronic switch; and 2) a second feedback loop configured to adjust a second switching parameter of the at least one electronic switch. The second feedback loop includes a switched-capacitor circuit configured to determine a threshold signal based on an error between a reference signal and a control signal for the at least one electronic switch. The second feedback loop is configured to adjust the second switching parameter based on a comparison of an on-time signal with the threshold signal.