Boost Converter CrCM Control With Per-Switch Over-Current Sensing
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Solution Overview
Problem
Existing boost power converters operating in Critical Conduction Mode (CrCM) face challenges in efficiently regulating peak inductor current and preventing over-current conditions, while also achieving high switching frequencies.
Innovation Solution
The implementation of a power factor correction circuit that senses high bandwidth bidirectional inductor current using current-sense resistor based per-switch sensing, compares it against reference thresholds, and provides over-current protection and CrCM control, enabling operation at higher switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If peak inductor current is increased to provide large output power, then output power is improved, but over-current conditions occur
Solution Approach 1:
The patent implements preliminary over-current detection by comparing the peak inductor current against a predetermined threshold before the over-current condition can cause damage. The control circuit is configured to detect when the peak current exceeds the threshold and immediately respond by adjusting the switching duty cycle, preventing harmful over-current conditions while allowing high peak currents necessary for large output power delivery.
2Speed
If conventional current sensing methods are used, then device complexity is reduced, but switching frequency is limited to lower values
Solution Approach 1:
The patent merges the current sensing function with the existing switching circuitry by utilizing the current sense resistor that is already part of the power stage. The sensing resistor is integrated into the circuit path, and the same control circuit that generates switching signals also performs the current comparison and protection functions, eliminating the need for separate complex sensing circuits and enabling higher switching frequencies.
3Adaptability or versatility
If CrCM operation is implemented to improve power factor, then power factor is improved, but over-current regulation becomes more difficult
Solution Approach 1:
The patent implements feedback control by continuously monitoring the peak inductor current in CrCM operation and comparing it against the threshold. The control circuit adjusts the switching duty cycle based on this feedback to maintain proper current regulation. This feedback mechanism enables effective CrCM operation for power factor correction while maintaining precise over-current regulation through real-time monitoring and adjustment.
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
This solution effectively prevents over-current conditions, enables CrCM operation with high switching frequencies, and improves power factor correction, enhancing the overall efficiency and performance of boost power converters.
Implementation Method 1
current-sense resistor based per-switch sensing
Data Source
AI summary
A power converter includes an input coupled to an inductor, a first switch coupled to a first comparator, and a second switch coupled to a second comparator. The power converter also includes a pulse comparison counter coupled to the first comparator and the second comparator and a synchronous rectifier (SR) calculator coupled to the pulse comparison counter. The synchronous rectifier calculator is operable to modify a conduction time of the first switch during a first AC half-cycle and modify a conduction time of the second switch during a second AC half-cycle.