Gate Driver Overcurrent Detection for Short PWM Pulses
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Solution Overview
Problem
Switched mode power supplies (SMPS) face challenges in effectively detecting and managing overcurrent conditions, particularly during short pulse width modulation (PWM) pulses, which can lead to uncontrolled temperature increases and potential system destruction due to the limited time window for overcurrent detection.
Innovation Solution
A method and system for overcurrent protection in SMPS that senses load currents during specific time intervals based on the operation of high and low side switching elements, using PWM signals to switch between detection modes and adjust control pulses to prevent overcurrent conditions, incorporating current sensors, comparators, and latch circuits to ensure robust detection even for short PWM pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent detection is performed during short PWM pulses, then system protection is improved, but the detection time window becomes insufficient leading to detection failure
Solution Approach 1:
The patent extends the detection time window by performing overcurrent detection during the low side switching element's on-time, which occurs before the high side switching element would be activated. This preliminary detection allows the system to identify overcurrent conditions during the extended time interval when the low side switch is conducting, ensuring detection capability even for short PWM pulses where the traditional high side switch on-time would be insufficient.
2Measurement precision
If current sensing is performed during high side switching element on-time, then overcurrent detection is achieved, but detection is impossible during short PWM pulses due to insufficient time
Solution Approach 1:
The patent inverts the traditional detection approach by sensing current during the low side switching element's on-time rather than during the high side switching element's on-time. This inversion exploits the complementary nature of the half-bridge switching, where when one switch is off, the other is on. By detecting during the low side switch's conduction period, the system gains an extended detection window that does not compete with the high side switch activation timing, thereby maintaining detection accuracy for both short and long PWM pulses.
3Use of energy by moving object
If PWM pulse duration is reduced for efficient power conversion, then power efficiency is improved, but overcurrent detection capability deteriorates
Solution Approach 1:
The patent enables overcurrent detection during the low side switching element's on-time, which serves as a preliminary detection phase before the high side switch would be activated. This approach allows the system to maintain extended detection windows even when PWM pulse durations are reduced for improved power efficiency, as the detection occurs during the complementary low side switch conduction period rather than competing with the high side switch timing.
Data Source
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.