GaN Power HEMT Slew Rate Clamp for Startup False Turn-On
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Solution Overview
Problem
Existing GaN power devices face issues with false turn-on due to high slew rates during non-operating times, particularly during startup when the voltage supply for active Miller clamps is not yet established, leading to potential shoot-through and reduced efficiency.
Innovation Solution
A slew rate protection circuit is integrated with a clamping transistor and detection circuit to prevent false turn-on by activating only during transient voltage events, disabling when a voltage supply is established, thus providing robust protection without requiring a continuous power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active Miller clamp is used to prevent false turn-on, then reliability is improved, but the device requires a voltage supply that may not be established during startup
Solution Approach 1:
The slew rate protection circuit is designed to operate during the startup period before the main voltage supply is established. It performs the protective function preliminarily during the time when the active Miller clamp cannot yet operate, ensuring continuous protection coverage from the moment the device is powered on.
Solution Approach 2:
The slew rate protection circuit acts as an intermediary protective mechanism that bridges the gap during startup. It uses the auxiliary voltage supply (Vaux) to activate the clamping transistor and provide protection before the main voltage supply (VDD) becomes available to power the active Miller clamp.
2Reliability
If external gate resistance is added to reduce dV/dt, then false turn-on is prevented, but switching period is extended and switching losses increase
Solution Approach 1:
The protection circuit dynamically activates only during the critical startup period when VDD is not yet established. During normal operation when VDD is available, the active Miller clamp handles protection while the slew rate protection circuit is disabled, allowing fast switching without the delays that would result from continuously active protection mechanisms.
Solution Approach 2:
The slew rate protection circuit operates periodically only during the startup phase before VDD establishment. Once VDD is established and the active Miller clamp becomes operational, the slew rate protection circuit transitions to an inactive state, thereby providing protection when needed while maintaining fast switching performance during normal operation.
Data Source
AI summary
A power integrated circuit comprising at least one III-nitride high voltage high-electron-mobility transistor (power HEMT), the power HEMT comprising a heterojunction formed between a GaN layer and an AlGaN layer, and a slew rate protection circuit. The slew rate protection circuit comprising a clamping transistor electrically connected between a gate terminal and a source terminal of the power HEMT, and a detection circuit electrically connected between a drain terminal and the source terminal of the power HEMT, wherein an output of the detection circuit is electrically connected to a gate terminal of the clamping transistor. The detection circuit is configured to output a signal to turn-on the clamping transistor when a transient voltage greater than a threshold transient voltage is observed across the drain and the source terminals of the power HEMT.