PWM Controller for Buck Boost Converter Linear Control
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Solution Overview
Problem
Conventional PWM controllers for buck and boost converters are not suitable for combined buck and boost converters as they perform linear control differently, preventing linear output voltage control when used interchangeably.
Innovation Solution
A PWM controller design for buck and boost converters that includes a first saw wave generator, a peak hold circuit, and a second saw wave generator, with comparators to generate control pulses based on error voltages and reference voltages, allowing for linear control in both boost and buck modes by adjusting duty ratios of output transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional PWM controllers for buck or boost converters are used separately, then linear output voltage control is achieved in each mode, but the controller cannot be used interchangeably in combined buck and boost converters
Solution Approach 1:
The patent designs a single PWM controller that can operate in both buck and boost modes by using mode selection signals to switch between different control paths. The controller includes separate control circuits for buck mode and boost mode, with multiplexers that select the appropriate control path based on the operating mode, enabling one controller to perform multiple functions that previously required separate controllers.
2Adaptability or versatility
If a single PWM controller is designed to handle both buck and boost modes, then controller versatility is improved, but the control circuit complexity increases
Solution Approach 1:
The patent segments the control circuit into distinct buck mode control path and boost mode control path, each optimized for its specific operating mode. The buck control path includes components optimized for step-down regulation, while the boost control path includes components optimized for step-up regulation. Mode selection signals activate only the relevant path, reducing the effective complexity at any given time while maintaining dual-mode capability.
Solution Approach 2:
The patent uses mode detection circuitry that preliminarily determines the operating mode (buck or boost) based on input voltage, output voltage, and load conditions before activating the appropriate control path. This preliminary action allows the controller to prepare the correct control circuit configuration in advance, avoiding the need for complex real-time switching and reducing overall controller complexity.
Data Source
AI summary
A PWM controller for adjusting an output voltage of a buck and boost converter includes a first saw wave generator, which generates a first saw wave in accordance with the level of the output voltage. A first comparator coupled to the first saw wave generator compares the first saw wave with a first reference voltage and generates a first pulse. A peak hold circuit coupled to the first saw wave generator holds a peak value of the first saw wave. A second saw wave generator coupled to the peak hold circuit generates a second saw wave having a lower limit value that is the peak value of the first saw wave. A second comparator coupled to the second saw wave generator compares the second saw wave with the first reference voltage and generates a second pulse.