3-State Buck-Boost PWM Control for Inductor Current Reduction
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Solution Overview
Problem
Conventional voltage regulators operating in buck-boost mode often experience reduced efficiency due to high inductor current levels and difficulty in transitioning between buck and boost modes when input voltage is close to output voltage, leading to inefficient operation in intermediate buck-boost mode.
Innovation Solution
A current-mode 3-state buck-boost pulse width modulation (PWM) control architecture is implemented, which introduces an intermediate switching state between conventional 2-state configurations, allowing for controlled delay in PWM signals to manage inductor current effectively, thereby reducing average inductor current and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional 2-state buck-boost mode is used, then the voltage regulator can operate in buck-boost mode, but the inductor current becomes excessively high reducing efficiency
Solution Approach 1:
The patent divides the conventional 2-state buck-boost operation into three distinct states by adding an intermediate state. State 1 corresponds to traditional buck mode, State 2 is the new intermediate buck-boost state with controlled inductor current, and State 3 corresponds to traditional boost mode. This segmentation allows the regulator to operate in the intermediate state when input voltage is close to output voltage, preventing the excessive inductor current that would occur in conventional 2-state operation and thereby improving efficiency.
2Ease of operation
If conventional 2-state configuration is used, then the control is simple, but transitioning between buck and boost modes is difficult when input voltage is close to output voltage
Solution Approach 1:
The patent introduces an intermediate buck-boost state that acts as a mediator between buck mode and boost mode. When the input voltage approaches the output voltage, the controller transitions to this intermediate state, which provides a smooth bridging operation. This intermediary state eliminates the difficulty of direct mode transitions in conventional 2-state configurations, allowing seamless operation across the full voltage range while maintaining controlled inductor current levels.
3Speed
If conventional 2-state PWM control is used, then the control architecture is simple, but the transient response is slow
Solution Approach 1:
The patent implements a dynamic control architecture that automatically selects between three operating states based on real-time voltage conditions. The controller monitors input and output voltages and dynamically transitions between State 1 (buck), State 2 (intermediate buck-boost), and State 3 (boost) to optimize performance. This dynamic adaptation enables fast transient response by immediately switching to the appropriate state when load or voltage conditions change, overcoming the slow response limitation of fixed 2-state configurations.
Data Source
AI summary
A voltage regulator including a converter and a modulator. The converter includes a switching circuit coupled to an inductor for converting an input voltage to an output voltage. The modulator controls the switching circuit in a buck mode of operation, a boost mode of operation, and an intermediate buck-boost mode of operation. During the buck-boost mode of operation, the modulator controls the switching circuit during each switching cycle to sequentially switch between three different switching states, including a first switching state that applies the input voltage across the inductor, a second switching state that applies a difference between the input and output voltages across the inductor, and a third switching state that applies the output voltage across the inductor. The modulator is controlled based on voltage applied across or current flowing through the inductor to regulate the output voltage to a target level.