Buck DC/DC Converter Control for Short-Circuit Overcurrent Limiting
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Solution Overview
Problem
Buck DC/DC converters face challenges in overcurrent protection, particularly when the output line is shorted to ground, leading to increased coil current and high currents through both high-side and low-side transistors, necessitating an effective overcurrent protection mechanism.
Innovation Solution
A controller for synchronous rectification type buck DC/DC converters is designed with a pulse modulator, overcurrent detection circuit, and switch control circuit to generate control pulses that manage the operation of high-side and low-side transistors, implementing an overcurrent protection mode to limit currents within a predetermined threshold, independent of the main feedback loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent protection is implemented by monitoring low-side current, then transistor damage is prevented, but the system cannot distinguish between genuine overcurrent faults and normal high current operating conditions
Solution Approach 1:
The patent applies local quality by implementing different detection thresholds for different operating modes. The system uses a first threshold for normal operation and a second, lower threshold for short-circuit detection. This allows the system to adapt its sensitivity based on the specific operational context, preventing false positives during high-current normal operation while maintaining sensitivity for actual fault conditions.
Solution Approach 2:
The patent implements dynamics by making the detection threshold variable rather than fixed. The threshold dynamically changes based on the operating mode: a higher threshold during normal operation and a lower threshold during short-circuit conditions. This dynamic adaptation allows the system to maintain accurate fault detection across varying operational states without sacrificing protection reliability.
2Device complexity
If a fixed threshold is used for overcurrent detection, then the circuit is simple to implement, but it causes false triggering during normal high current operation
Solution Approach 1:
The patent resolves this contradiction by implementing a dynamic threshold system that automatically adjusts based on operating mode. During normal operation, a higher threshold prevents false triggering, while during short-circuit conditions, a lower threshold enables accurate fault detection. This dynamic approach maintains circuit reliability without requiring excessively complex additional hardware.
Solution Approach 2:
The patent applies parameter changes by modifying the detection threshold parameter based on operational context. The system changes the threshold value from a first level during normal operation to a second level during short-circuit detection. This parameter adaptation allows the same detection circuit to operate reliably across different current conditions without requiring completely separate detection paths.
3Adaptability or versatility
If the controller uses dual thresholds for short-circuit detection, then accurate fault identification is achieved, but the control logic becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the control logic into distinct segments: normal operation mode and short-circuit detection mode. Each mode has its own threshold and response protocol. This segmentation simplifies the overall control logic by creating clear, discrete decision paths rather than requiring complex continuous analysis, making the dual-threshold system more manageable despite the increased precision requirements.
Data Source
AI summary
The present disclosure relates to a buck DC/DC converter, a controller thereof and controlling method thereof, and an electronic device. A pulse modulator generates a pulse modulation signal such that an output of the buck DC/DC converter is pulse-modulated to approach a target state. An overcurrent detection circuit compares a low-side current flowing through a low-side transistor with a predetermined overcurrent threshold value to generate an overcurrent detection signal that is asserted when the low-side current is greater than the overcurrent threshold value. (i) In a first mode, the control pulse that is input to the driver circuit corresponds to the pulse modulation signal, and (ii) in a second mode, the control pulse takes a second level for a period during which the overcurrent detection signal is asserted and takes a first level during a fixed on time after the overcurrent detection signal is negated.