Inverter Gate Drive Dynamic Voltage Control
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Solution Overview
Problem
High-speed switching of semiconductor power devices in hard-switched applications leads to excessive voltage overshoot during turn-off, which can exceed device ratings, causing damage, and existing solutions like increasing device size or slowing down switching speed result in inefficiencies and additional costs.
Innovation Solution
A system and method for dynamic control of the gate drive negative rail voltage, using control algorithms to adjust the negative bias voltage rail and limit the device turn-off rate, thereby reducing voltage overshoot while minimizing switching losses and maximizing DC bus voltage utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fast switching is used to decrease power losses and improve inverter efficiency, then switching losses are reduced, but voltage overshoot increases and may exceed device ratings causing damage
Solution Approach 1:
The patent applies dynamics by making the gate resistance variable rather than fixed. The gate driver circuit dynamically adjusts the gate resistance value based on real-time monitoring of voltage overshoot conditions, switching state, and current levels. During fast switching operations, higher gate resistance is applied to limit dI/dt and reduce voltage overshoot, while during normal operation, lower gate resistance enables faster switching and reduced losses.
Solution Approach 2:
The patent changes the parameter of gate resistance dynamically during operation. By varying the gate resistance parameter based on operating conditions (switching state, current magnitude, voltage overshoot levels), the system optimizes the trade-off between switching speed and voltage overshoot control, resolving the contradiction between efficiency and device safety.
2Reliability
If larger gate resistance is used to limit voltage overshoot, then device safety is improved, but switching speed decreases and efficiency is reduced
Solution Approach 1:
The system dynamically adjusts gate resistance based on real-time conditions rather than using a fixed large resistance value. This allows the system to maintain high switching speed during normal operation while providing overvoltage protection when needed, thus improving both productivity and reliability simultaneously.
Solution Approach 2:
The gate resistance is periodically adjusted during switching cycles based on monitored parameters. The control circuit continuously monitors voltage overshoot and switching state, then adjusts gate resistance accordingly - applying high resistance only during critical turn-off moments when voltage overshoot risk exists, and low resistance during other phases to maintain efficiency.
3Power
If higher DC link voltage is used to maximize power output, then power capability is improved, but voltage overshoot risk increases and may exceed device ratings
Solution Approach 1:
The gate driver circuit acts as an intermediary between the high-voltage power system and the switching devices. It monitors voltage overshoot conditions and adjusts gate resistance to prevent the cumulated voltage from exceeding device ratings, enabling the system to operate at higher DC link voltages without compromising device safety.
Solution Approach 2:
The system employs feedback by continuously monitoring voltage overshoot conditions and switching state, then using this information to adjust gate resistance in real-time. This feedback mechanism allows the system to maximize DC link voltage utilization while maintaining voltage rating compliance through dynamic protection.
Data Source
AI summary
An apparatus includes an inverter including a high-side switch coupled to a low-side switch, the inverter generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein controlling the switches to generate the time-varying drive current produces a potential transitory overshoot condition for one of the switches of the inverter; a drive control, coupled to the inverter, to generate the drive control signals and to set a level of each of the rail voltages responsive to a plurality of controller signals; and a controller monitoring one or more parameters indicative of the potential transitory voltage overshoot condition, the controller dynamically adjusting, responsive to the monitored parameters, the controller signals to reduce a risk of occurrence of the potential transitory voltage overshoot condition.