Switching Regulator Short Circuit Detection Timing Controller
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Solution Overview
Problem
Conventional DC-DC converters face issues with erroneous short circuit detection due to noise, leading to a small detection margin when the short circuit detection threshold is set close to the peak current, which can result in false alarms and require enlarging the coil to reduce noise-induced fluctuations, increasing circuit complexity.
Innovation Solution
A timing controller is introduced between the comparator and PWM controller to generate a second short circuit detection signal based on the activation periods of the transistors, allowing for a larger detection margin by validating or invalidating the initial detection signal from the comparator, thus preventing erroneous detections without enlarging the coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the short circuit detection threshold is set close to the peak current to improve detection sensitivity, then the detection precision is improved, but the reliability deteriorates due to noise causing erroneous detections
Solution Approach 1:
The timing controller performs preliminary action by determining the activation periods of the transistors in advance and using this timing information to validate or invalidate the detection signal. This prevents noise during switching transitions from causing erroneous detections, thereby maintaining high detection precision while improving reliability.
Solution Approach 2:
The system uses feedback by comparing the detection signal with the actual transistor activation timing. The timing controller provides feedback information about when transistors are activated, and this feedback is used to determine whether a detection signal represents a true short circuit or noise, thus resolving the contradiction between precision and reliability.
2Reliability
If the coil is enlarged to reduce noise-induced current fluctuations, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The timing controller acts as an intermediary between the comparator and the short circuit detection logic. Instead of modifying the coil to reduce noise, the timing controller mediates by using timing information to validate detection signals, thereby maintaining reliability without increasing device complexity.
Solution Approach 2:
The invention changes the parameter being monitored from current magnitude alone to a combination of current magnitude and timing information. By adding the timing dimension as a validation criterion, the system achieves improved reliability without needing to enlarge the coil or modify its physical parameters.
3Measurement precision
If the detection margin is reduced to allow threshold close to peak current, then the measurement precision is improved, but the stability deteriorates due to false alarms
Solution Approach 1:
The timing controller performs preliminary validation by checking whether the detection signal occurs during a valid transistor activation period. This preliminary action filters out false alarms caused by noise while maintaining the ability to detect true short circuits, thus improving detection stability without sacrificing precision.
Data Source
AI summary
A method and circuit for accurately detecting an output short circuit in a switching regulator. A first transistor and a second transistor are connected in series and driven in a complementary manner. A comparator compares output current, which is generated when the first and second transistors are driven, with a short circuit detection threshold to generate a first short circuit detection signal. A timing controller retrieves the first short circuit detection signal generated by the comparator at a predetermined time to generate a second short circuit detection signal.