Voltage-Sensed Transistor Switching for Loss and EMI Control
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Solution Overview
Problem
The existing systems for controlling transistors as switches in H-bridge configurations face challenges in managing switching losses and electromagnetic interference (EMI) while ensuring safe operation during short circuit and overcurrent conditions, as they struggle to balance the rates of current and voltage changes during switching phases.
Innovation Solution
A system comprising a voltage sensing circuit, a control circuit, and a driver circuit that modulates the charge and discharge currents to optimize the switching process, including a method to detect and respond to short circuit and overcurrent conditions by adjusting the charge current magnitudes and phases, thereby reducing switching losses and EMI while ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transistor switching speed is increased to improve productivity, then the switching losses and EMI increase, but the system reliability deteriorates during short circuit and overcurrent conditions
Solution Approach 1:
The patent applies dynamics by making the charge current magnitude adjustable based on the detected voltage change rate. The driver circuit dynamically modifies the charge current magnitude during the switching phase based on feedback from the voltage sensing circuit, allowing the system to optimize switching speed while controlling switching losses and EMI generation.
Solution Approach 2:
The patent implements feedback through the voltage sensing circuit that monitors the voltage across the transistor's current terminals during switching. The control circuit uses this feedback information to detect short circuit and overcurrent conditions, and to adjust the charge current magnitude provided by the driver circuit, creating a closed-loop control system that balances switching performance with safety.
2Loss of energy
If the charge current magnitude is increased to reduce switching losses, then the voltage change rate increases causing higher EMI, but the system generates more electromagnetic interference
Solution Approach 1:
The patent applies dynamics by making the charge current magnitude adjustable based on the detected voltage change rate. The driver circuit dynamically modifies the charge current magnitude during the switching phase based on feedback from the voltage sensing circuit, allowing the system to optimize switching speed while controlling switching losses and EMI generation.
Solution Approach 2:
The patent changes the charge current magnitude parameter dynamically during the switching phase. By adjusting this parameter based on the detected voltage change rate, the system can reduce switching losses when safe to do so while limiting EMI generation when voltage changes are rapid, thus resolving the contradiction between energy loss and harmful electromagnetic effects.
3Device complexity
If the switching control is simplified to reduce device complexity, then the ability to detect and respond to short circuit and overcurrent conditions deteriorates
Solution Approach 1:
The patent implements feedback through the voltage sensing circuit that monitors the voltage across the transistor's current terminals during switching. The control circuit uses this feedback information to detect short circuit and overcurrent conditions, and to adjust the charge current magnitude provided by the driver circuit, creating a closed-loop control system that balances switching performance with safety.
Solution Approach 2:
The voltage sensing circuit provides self-service by automatically detecting voltage conditions across the transistor and providing this information to the control circuit. This self-monitoring capability enables the system to detect short circuit and overcurrent conditions without requiring complex external monitoring equipment, thus maintaining reliability while avoiding excessive complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively reduces switching losses, minimizes EMI, and enhances safety by precisely controlling the transistor's switching phases, preventing damage and extending the lifespan of the transistors during short circuit and overcurrent events.
Implementation Method 1
The voltage sensing circuit is configured to generate a first voltage at the voltage sensing output representing a second voltage at the voltage sensing terminal
Implementation Method 2
A transistor includes various parasitic capacitances at the control terminal, such as gate-source capacitance (CGS) and gate-drain capacitance (CGD), which can be charged or discharged to modulate the voltage of the control terminal
Data Source
AI summary
In one example, an apparatus comprises: a voltage sensing circuit having a voltage sensing terminal and a voltage sensing output, the voltage sensing circuit configured to generate a first voltage at the voltage sensing output representing a second voltage at the voltage sensing terminal; a control circuit having a control circuit input and a control circuit output, the control circuit input coupled to the voltage sensing output, the control circuit configured to: determine a state of a transistor based on the first voltage; and generate a driver signal at the control circuit output based on the state; and a driver circuit having a driver input and a switch control output, the driver input coupled to the control circuit output, the driver circuit configured to provide a current at the switch control output responsive to the driver signal.