Tri-State Buck-Boost Driver With Separate Duty Cycle Control
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Solution Overview
Problem
Existing buck-boost converters face challenges in achieving high linearity and efficiency due to the presence of a right half-plane zero, which limits control system bandwidth and causes undershoots, and the fixed de-energizing duty cycle leads to inefficiencies, especially at low duty cycles.
Innovation Solution
A tri-state buck-boost system with a freely changeable de-energizing duty cycle and independent control of energizing and de-energizing phases, utilizing a buck-boost control loop with feedback and feedforward mechanisms to optimize duty cycles and reduce freewheeling time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed de-energizing duty cycle is used in traditional buck-boost converters, then the control structure is simple, but efficiency deteriorates especially at low duty cycles due to excessive freewheeling time
Solution Approach 1:
The patent segments the duty cycle control into two independent components: energizing phase duty cycle (De) and de-energizing phase duty cycle (Dd). This allows separate optimization of each phase, enabling the de-energizing phase to be extended to reduce freewheeling time without affecting the energizing phase control, thereby improving efficiency without excessive complexity
Solution Approach 2:
The patent introduces dynamic adjustment of the de-energizing duty cycle based on the energizing duty cycle. The de-energizing duty cycle is set as Dd = 1 - De + ΔD, where ΔD is an additional duty cycle component. This dynamic relationship allows the converter to adaptively optimize the de-energizing phase duration according to the energizing phase requirements, reducing freewheeling time and improving efficiency across different operating conditions
2Productivity
If the de-energizing duty cycle is extended to reduce freewheeling time, then efficiency improves, but the control complexity increases
Solution Approach 1:
The patent implements a control mechanism where the de-energizing duty cycle is determined based on feedback from the energizing duty cycle. The relationship Dd = 1 - De + ΔD creates a feedback loop that automatically adjusts the de-energizing phase duration according to the energizing phase requirements, enabling efficient operation without requiring complex external control circuits
Solution Approach 2:
The patent changes the duty cycle parameters from a fixed single duty cycle to two variable duty cycles (De and Dd) with a defined relationship. This parameter transformation allows the system to optimize the de-energizing phase duration dynamically, reducing freewheeling time and improving efficiency while maintaining manageable control complexity through the established mathematical relationship
3Manufacturing precision
If traditional PWM control is used, then the control implementation is straightforward, but linearity deteriorates due to the right half-plane zero causing undershoots and limiting control bandwidth
Solution Approach 1:
The patent segments the switching control into energizing and de-energizing phases with separate duty cycle controls. This segmentation eliminates the right half-plane zero issue present in traditional single-duty-cycle buck-boost converters, allowing independent optimization of each phase to improve output voltage linearity and eliminate undershoots
Solution Approach 2:
The patent introduces dynamic control of both energizing and de-energizing phases with the relationship Dd = 1 - De + ΔD. This dynamic control strategy allows the system to respond more effectively to input changes, improving linearity and eliminating the bandwidth limitations caused by the right half-plane zero in traditional fixed-duty-cycle designs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances efficiency by minimizing freewheeling time and maintaining linearity, reducing total harmonic distortion, and improving control system performance.
Implementation Method 1
a tri-state buck-boost converter configured to operate in an energizing phase in which energy of an inductor is increased, a de-energizing phase in which the energy of the inductor is decreased
Data Source
AI summary
A variable de-energizing phase duty cycle Dd is generated based on an input signal to optimize for a low duty cycle in a freewheeling phase. A variable energizing phase duty cycle De is generated based on a buck-boost control loop tracking the input signal. A tri-state buck-boost converter is controlled using the variable energizing phase duty cycle De and the variable de-energizing phase duty cycle Dd.