Gate Drive Unit for Power Switch Short Circuit Protection
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Solution Overview
Problem
Existing power switches in circuits, such as MOSFETs and IGBTs, are vulnerable to damage from short circuits due to insufficient protection mechanisms, particularly when rapid current changes occur, as current protection devices like fuses may fail to prevent damage in time, and active clamping requires complex tuning for optimal performance.
Innovation Solution
A gate drive unit with a measurement unit, multi-resistive driving device, and processing unit that measures voltages and currents across power switches, dynamically adjusts the control voltage by activating or deactivating individually controllable resistive elements to manage the rate of voltage decrease during short circuit events, distinguishing between different types of short circuits to implement appropriate protection procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuses are used for short circuit protection, then protection is provided against overcurrent, but fuses cannot blow fast enough to prevent damage from rapid short circuits occurring during switch activation
Solution Approach 1:
The gate driver monitors voltage across the power switch during turn-on and detects short circuit conditions before they can cause damage. By detecting the abnormal voltage profile during the activation phase and preemptively preventing full turn-on, the system protects the switch before excessive current can flow, rather than reacting after the fuse would need to blow.
Solution Approach 2:
The gate driver continuously monitors the voltage across the power switch during activation and uses this feedback to detect short circuit conditions. When a short circuit is detected during turn-on, the driver adjusts the gate voltage waveform to prevent the switch from fully conducting, thereby protecting the device without requiring a fuse to interrupt the current.
2Reliability
If abrupt voltage elimination is used to switch off current during short circuit, then current conduction is stopped quickly, but the power switch can be damaged or destroyed
Solution Approach 1:
The gate driver dynamically adjusts the gate voltage waveform based on real-time monitoring of the power switch voltage. During a short circuit condition, the driver modulates the gate voltage to control the turn-off process, preventing abrupt voltage elimination that would cause damage while still stopping current conduction. This dynamic control adapts the switching behavior to the specific fault condition.
Solution Approach 2:
The gate driver changes the gate voltage parameters (magnitude, duration, waveform shape) based on detected short circuit conditions. By adjusting these parameters, the driver controls the rate of current change and prevents damaging voltage spikes during turn-off, while still achieving the necessary current interruption to protect the circuit.
3Reliability
If active clamping is used to protect from overvoltage at short circuit turn-off, then switch protection is provided, but intensive tuning of analog circuit is required which is difficult to achieve for all operational conditions
Solution Approach 1:
The gate driver performs self-diagnosis by monitoring its own output and the power switch voltage during activation. The built-in short circuit detection functionality automatically identifies fault conditions and adjusts the gate waveform without requiring external analog tuning circuits. This self-monitoring approach eliminates the need for complex adjustable analog protection circuits while providing robust protection across all operational conditions.
Data Source
AI summary
A gate drive unit includes a measurement unit, a multi-resistive driving device, and a processing unit. The measurement unit measures a voltage across main terminals of a power switch. The driving device includes plural individually controllable resistive elements. The processing unit controls a control voltage applied to a control electrode of the power switch to activate the power switch. The processing unit individually activates or deactivates the resistive elements of the multi-resistive driving device to change which of the resistive elements at least partially conducts the control voltage to the power switch at different times responsive to the voltage across the main terminals representing a short circuit event. The processing unit changes which of the resistive elements are activated or deactivated to control a rate at which the control voltage decreases.