Multi-phase Buck Boost Converter Mode Transition Control
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Solution Overview
Problem
Non-inverting buck boost converters face challenges in transitioning between buck and boost modes of operation, particularly with line transients and output ripple when the output voltage is close to the input voltage, due to dynamic response and steady-state performance issues.
Innovation Solution
A control scheme using a single integrated current sensor for peak current mode control in buck mode and valley current mode control in boost mode, with cycle-by-cycle detection and maximum duty cycle monitoring to facilitate smooth transitions and minimize output ripple, allowing the converter to automatically switch between modes based on the duty cycle condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single integrated current sensor is used for both buck and boost mode control, then device complexity is reduced, but control precision may be compromised during mode transitions
Solution Approach 1:
The patent implements a single integrated current sensor that serves dual functions for both buck mode peak current detection and boost mode valley current detection. This universal sensor replaces what would traditionally require separate sensing circuits for each mode, thereby reducing device complexity while maintaining adequate measurement precision through software-based mode-specific signal processing
Solution Approach 2:
The control system dynamically changes the interpretation and processing parameters of the current sensor output based on operating mode. During buck mode, the system processes peak current values; during boost mode, it processes valley current values. This parameter adaptation allows a single sensor to provide precise measurements for both modes without requiring hardware changes
2Reliability
If cycle-by-cycle detection with maximum duty cycle monitoring is implemented, then reliability during mode transitions is improved, but device complexity increases
Solution Approach 1:
The patent implements cycle-by-cycle detection that continuously monitors the duty cycle and provides feedback to the control system. When the duty cycle approaches the maximum threshold, the system receives feedback signals that trigger automatic mode transition. This feedback mechanism ensures reliable mode switching while using simple comparator circuits rather than complex control logic
Solution Approach 2:
The control system automatically detects when mode transition is needed through self-monitoring of the duty cycle parameter and autonomously switches between buck and boost modes without external intervention. The maximum duty cycle monitoring circuit automatically generates transition commands, making the system self-regulating and reducing the need for complex external control mechanisms
3Adaptability or versatility
If the converter operates near maximum duty cycle to maintain output voltage when input voltage is close to output voltage, then adaptability is improved, but output ripple increases
Solution Approach 1:
The patent implements dynamic mode switching that automatically adjusts the converter operation between buck and boost modes based on the real-time relationship between input and output voltages. When the input voltage approaches the output voltage, the system dynamically transitions modes to maintain optimal duty cycle operation away from the maximum, thereby reducing output ripple while preserving adaptability to various input conditions
Solution Approach 2:
The cycle-by-cycle duty cycle monitoring creates periodic detection and adjustment actions that prevent the converter from operating continuously at maximum duty cycle. By periodically checking the duty cycle parameter and triggering mode transitions at appropriate intervals, the system maintains adaptability to input voltage changes while avoiding the harmful effects of sustained maximum duty cycle operation
Data Source
AI summary
A multi-phase non-inverting buck boost voltage converter has a plurality of buck boost voltage regulators. Each regulator is associated with a separate phase for generating a regulated output voltage responsive to an input voltage. A plurality of current sensors are each associated with one of the plurality of buck boost voltage regulators for monitoring an input current to the associated buck boost voltage regulator and generating a current sense signal for the associated phase. A plurality of buck boost mode control circuitries are each associated with one of the buck boost regulator for controlling an associated buck boost voltage regulator using peak current mode control in a buck mode of operation and valley current mode control in boost mode of operation responsive to a common error voltage and the associated current sense signal. The plurality of buck boost mode control circuitries provides current balancing between the phases. A voltage error circuit generates the error voltage responsive to the regulated output voltage.