Inverter Gate Drive Dynamic Negative Rail 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 vary the negative bias voltage 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 can 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, allowing the system to optimize switching speed while preventing excessive voltage overshoot that would damage devices.
Solution Approach 2:
The patent changes the parameter of gate resistance from a static value to a dynamically adjustable parameter. By varying the gate resistance based on system conditions, the patent achieves both fast switching for low losses and controlled voltage overshoot to protect devices from damage.
2Reliability
If device size is increased to handle voltage overshoot, then device reliability improves, but inverter efficiency decreases and costs increase
Solution Approach 1:
The patent implements self-service by enabling the gate driver circuit to automatically monitor voltage overshoot conditions and adjust gate resistance accordingly. This self-regulating mechanism protects devices from voltage damage without requiring oversized components, thereby maintaining inverter efficiency while ensuring device reliability.
3Object-affected harmful factors
If switching speed is slowed down to reduce voltage overshoot, then device safety improves, but power losses increase and inverter efficiency decreases
Solution Approach 1:
The patent applies dynamics by implementing real-time adjustment of gate resistance based on monitored voltage overshoot conditions. This allows the system to maintain fast switching speeds for low power losses while dynamically reducing switching speed only when voltage overshoot threatens device safety, thereby resolving the contradiction between speed and safety.
4Loss of energy
If fixed gate resistance is used for fast switching, then switching losses are minimized, but voltage overshoot control and adaptability to different operating conditions deteriorate
Solution Approach 1:
The patent transforms the static gate resistance into a dynamic parameter that adapts to different operating conditions. The gate driver circuit continuously monitors system state and adjusts gate resistance accordingly, providing both fast switching for low losses and adaptive voltage overshoot control for various operating scenarios.
Solution Approach 2:
The patent changes the gate resistance from a fixed parameter to a variable parameter that can be adjusted based on operating conditions. This parameter change enables the system to optimize switching performance while maintaining voltage overshoot control across different operating scenarios.
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.