Dynamic Gate Resistor Control for Switching Devices

Solution Overview

Problem

Existing technologies for switching field effect transistors (FETs) in motor inverters face challenges in balancing switching speed and surge voltage, as adjusting the gate resistor resistance affects both power loss and noise, requiring a dynamic and adaptive approach to set appropriate resistance values based on specific FET types, circuit conditions, and load currents.

Innovation Solution

A switching device with a gate resistor unit comprising variable resistors and a control unit that calculates and sets appropriate resistance values for different periods of the switching cycle based on detected voltage and current values, using operational expressions and stored parameters to optimize switching performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the resistance of the gate resistor is increased, then the surge voltage generated in the turn-off period is suppressed, but the switching speed drops and power loss is increased

Engineering Contradiction:

Improvesurge voltageVSAvoidswitching speed

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The gate resistor resistance is made dynamically adjustable during the turn-off period. The control unit switches between a first resistance value (for suppressing surge voltage) and a second resistance value (for maintaining switching speed) based on the real-time voltage at the drain terminal, transforming a static component into a dynamic one to resolve the contradiction between surge suppression and switching speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The resistance parameter of the gate resistor is changed during operation based on circuit conditions. By adjusting the resistance value according to the drain voltage level, the system optimizes both surge voltage suppression and switching speed performance, resolving the fixed parameter limitation.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the resistance of the gate resistor is reduced, then the switching speed increases and power loss is reduced, but the surge voltage generated in the turn-off period becomes higher

Engineering Contradiction:

Improveswitching speedVSAvoidsurge voltage

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The gate resistor resistance is made dynamically adjustable during the turn-off period. The control unit switches between a first resistance value (for suppressing surge voltage) and a second resistance value (for maintaining switching speed) based on the real-time voltage at the drain terminal, transforming a static component into a dynamic one to resolve the contradiction between surge suppression and switching speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The resistance parameter of the gate resistor is changed during operation based on circuit conditions. By adjusting the resistance value according to the drain voltage level, the system optimizes both surge voltage suppression and switching speed performance, resolving the fixed parameter limitation.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If a switching control unit is used to dynamically adjust the gate resistor resistance, then both power loss and surge voltage are suppressed, but the device complexity increases

Engineering Contradiction:

Improvepower lossVSAvoidcontrol structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The control unit uses feedback from the drain voltage detection to automatically adjust the gate resistor resistance. This closed-loop control suppresses both power loss and surge voltage while maintaining relatively simple control logic, making the complexity acceptable for the performance gains achieved.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system automatically adjusts the gate resistor resistance based on real-time circuit conditions without requiring external intervention. The control unit self-regulates the resistance value according to the drain voltage level, reducing the need for complex external control mechanisms while achieving optimal performance.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10505529B1Switching device, power converter device, control apparatus, and computer program product

Publication Date: 2019.12.10 KK TOSHIBA

AI summary

According to an embodiment, a switching device includes: a switching control unit that connects a first resistor between an input terminal for receiving the switching signal and a gate of a switching transistor during a first period that is an anterior half of a turn-off period of the switching transistor, and connects a second resistor between the input terminal and the gate during a second period that is a posterior half of the turn-off period; a calculating unit that calculates a first gate resistance based on a target voltage rising rate and a first operational expression, and that calculates a second gate resistance based on the permissible maximum voltage value and a second operational expression; and a resistance setting unit that sets resistances of the first resistor and the second resistor based on the first gate resistance and the second gate resistance.