Gate Driver Overcurrent Sensing for Short PWM Pulses
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Solution Overview
Problem
Switched mode power supplies (SMPS) face challenges in effectively detecting overcurrent conditions, especially during short pulse width modulation (PWM) pulses, which can lead to uncontrolled temperature increases and potential system destruction due to limited time windows for robust overcurrent protection.
Innovation Solution
The method involves sensing load currents during specific time intervals when either the high side or low side switching elements are turned on, using threshold values and PWM signal durations to switch between operation modes, and employing current sensors and comparator circuits to detect overcurrent conditions, thereby reducing energy transport and heat generation by adjusting control pulses or turning off switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent protection is implemented using conventional sensing methods during short PWM pulses, then the detection window is limited, but the system can still detect overcurrent conditions during normal operation
Solution Approach 1:
The patent applies dynamics by switching between two operational modes based on PWM pulse duration. For short pulses, the system uses Mode 1 with extended sensing during the low-side switch on-time. For longer pulses, it uses Mode 2 with conventional sensing. This dynamic adaptation allows the system to maintain reliable overcurrent detection across varying pulse widths while optimizing the detection window for each scenario.
Solution Approach 2:
The patent changes the sensing parameter by extending the detection window beyond the high-side switch on-time to include the low-side switch on-time for short PWM pulses. This parameter change in the sensing strategy allows sufficient time for robust overcurrent detection even when the PWM pulse duration is very short, thereby improving detection reliability without being constrained by the limited pulse width.
2Reliability
If the detection window is extended to improve overcurrent detection for short PWM pulses, then detection reliability improves, but the complexity of the control system increases
Solution Approach 1:
The patent implements a universal overcurrent protection system that handles both short and long PWM pulses through a single integrated controller capable of operating in two modes. The same controller dynamically adapts its sensing strategy based on pulse duration, eliminating the need for separate protection circuits for different pulse types. This multi-functionality approach improves reliability for short pulses while avoiding the complexity of multiple dedicated circuits.
3Measurement precision
If overcurrent detection is performed continuously, then detection accuracy improves, but energy consumption and heat generation increase
Solution Approach 1:
The patent employs periodic action by performing overcurrent sensing only during specific intervals - either during the high-side switch on-time (Mode 2 for longer pulses) or during the low-side switch on-time (Mode 1 for short pulses). This periodic sensing approach maintains detection accuracy by sampling at the most informative moments while minimizing energy consumption compared to continuous sensing throughout the entire switching cycle.
Data Source
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AI summary
The present document relates to overcurrent protection methods and devices. In particular, the present document relates to overcurrent protection methods and devices for gate drivers which are receiving short pulse width modulation (PWM) pulses. In particular, a method of detecting an overcurrent in a switched mode power supply comprising a high side switching element and a low side switching element is described. The method may comprise sensing, in a first mode of operation, during a first sensing time interval when the low side switching element is turned on, a first current indicative of a load current. The method may comprise detecting an overcurrent condition if the first current exceeds a first threshold value.