Energy Predictive Buck Converter Control
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Solution Overview
Problem
Conventional buck converters face instability and poor transient response due to inadequate feedback loops, especially when the voltage error term is small or delayed, leading to restricted stability ranges and potential oscillations or destructive conditions.
Innovation Solution
Implementing energy balancing control that incorporates inductive current and volt-time representation to maintain a closed feedback loop across multiple cycles, optimizing transient response and stability by using squared terms and gain corrections, particularly with digital controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional voltage error feedback control is used, then the control loop is simple to implement, but the converter becomes unstable when voltage error is small or delayed, restricting stability range
Solution Approach 1:
The patent introduces energy balance feedback by comparing energy demand (based on output voltage error) with energy supply (based on inductive current and volt-time product). This feedback mechanism keeps the control loop closed even when voltage error is small, preventing instability and oscillations while maintaining a relatively simple control structure.
Solution Approach 2:
The patent changes the feedback parameter from voltage error alone to energy balance (combining volt-time product and inductive current). This parameter transformation allows the system to maintain stability across a wider duty cycle range by providing timely feedback even when voltage error is delayed or too small.
2Speed
If per-cycle energy balancing is implemented, then transient response is improved, but energy balance information is destroyed at the beginning of each chopping cycle, limiting recovery from severe transients
Solution Approach 1:
The patent implements multi-cycle energy balancing where energy supply information (volt-time product and inductive current) is maintained continuously across multiple chopping cycles rather than being reset each cycle. This continuous information availability enables the system to recover from severe transients by accumulating energy balance data over multiple cycles, improving both transient response and system resilience.
3Device complexity
If ramp signal is reset for each chopping cycle, then control is simplified, but energy supply is grossly misrepresented when inductor continues to charge from previous cycle
Solution Approach 1:
The patent incorporates inductive current and volt-time product into the energy supply term before the chopping cycle begins, allowing energy supply information to survive from cycle to cycle. This preliminary action ensures accurate energy supply representation is maintained throughout the inductor charging process, even when charging continues from a previous cycle, without significantly complicating the control signal generation.
Data Source
AI summary
A switched-mode buck power converter includes a power source, a first switch, an inductor for storing energy, a diode or second switch, and control circuitry. The inductor has a first end connected to an output node of the power converter, wherein the first switch is connected between the power source and a second end of the inductor. The diode or second switch is connected, at the second end of the inductor, between the first switch and a common node of the power converter. The control circuitry is configured to (i) characterize per cycle energy demand of the power converter, (ii) characterize per cycle inductive energy of the power converter, and (iii) compare the characterized energy demand to the characterized inductive energy to control the first switch.