Semiconductor Device for Non-Isolated Buck Converter Protection
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Solution Overview
Problem
Non-isolated buck converters face challenges in detecting and responding to inappropriate input voltages due to the difference in ground potentials between the input and output voltages, making it difficult to implement a protecting function for semiconductor devices.
Innovation Solution
A semiconductor device for non-isolated buck converters is designed with a control circuit that includes a protecting circuit capable of evaluating the voltage between the input and output terminals, allowing for switching control and protection operations based on predetermined voltage thresholds, using a voltage dividing circuit integrated on a silicon semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor device operates with a different ground potential (second ground potential) than the input and output voltages (first ground potential), then the semiconductor device can be isolated from voltage fluctuations and operate stably, but the device cannot detect the magnitude of the input voltage and perform protection operations
Solution Approach 1:
The patent introduces a ground potential conversion circuit as an intermediary between the control circuit (operating at second ground potential) and the input voltage (at first ground potential). This converter mediates the ground potential difference, allowing the control circuit to safely detect and respond to input voltage magnitude without direct exposure to voltage fluctuations at the first ground potential.
2Object-affected harmful factors
If the semiconductor device directly monitors input voltage for protection, then protection function can be implemented, but the device becomes vulnerable to ground potential differences and voltage fluctuations
Solution Approach 1:
The ground potential conversion circuit serves as a protective intermediary, allowing the control circuit to monitor input voltage through a safe interface. The converter isolates the control circuit from direct exposure to input voltage fluctuations while still enabling voltage magnitude detection for protection decisions.
3Reliability
If a protection circuit is added to detect input voltage magnitude, then protection operation can be performed, but the device complexity increases
Solution Approach 1:
The ground potential conversion circuit is designed to serve multiple functions: it converts ground potentials for stable operation, enables input voltage detection, and provides protection capability. By integrating these functions into a single circuit block, the patent avoids the need for separate protection circuits while maintaining reliability.
Data Source
AI summary
A non-isolated buck converter generates an output voltage by stepping down an input voltage obtained by subjecting an alternating-current voltage to full-wave rectification and smoothing, by using a step-down circuit including a switching element, an inductor, and a freewheeling diode. The switching element is disposed between a first terminal and a second terminal. A semiconductor device in charge of switching control operates with a potential at the second terminal as a reference. A control circuit provided in the semiconductor device includes a protecting circuit capable of referring to an evaluation voltage corresponding to a voltage between the first terminal and the second terminal at a sampling timing at which a predetermined period of time has passed from turning off of the switching element, and performing a protecting operation that fixes the switching element to an off state on the basis of the evaluation voltage.