Power Switch Driver Protection with Single-Terminal Fault Detection
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Solution Overview
Problem
Switched mode power converters face challenges in providing effective overvoltage and overcurrent protection, especially as operational voltages increase, due to the complexity and cost of protection circuitry, particularly with high-voltage IGBTs, where detecting conditions and preventing damage to power switches is difficult.
Innovation Solution
A switch controller with a switch fault detector that monitors voltage and current signals at a single sense terminal to detect overcurrent, short circuits, and overvoltage conditions, actively clamping voltages and turning off the power switch to prevent damage, using a combination of resistive dividers and current/voltage references to manage protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection circuitry is added to detect and prevent overvoltage and overcurrent conditions, then reliability of power switch protection is improved, but device complexity increases
Solution Approach 1:
The patent combines overvoltage detection and overcurrent detection functions into a single integrated controller device. The controller includes a first detection circuit for overvoltage conditions and a second detection circuit for overcurrent conditions, both integrated within the same controller that also generates gate drive signals. This merging reduces overall system complexity while maintaining comprehensive protection capabilities.
Solution Approach 2:
The controller is designed as a multi-functional device that simultaneously performs gate drive signal generation, overvoltage detection, overcurrent detection, and protective switching operations. By making the controller universal and multi-functional, the patent avoids adding separate dedicated protection devices, thereby improving reliability without proportionally increasing device complexity.
2Reliability
If detection sensitivity is increased to detect fault conditions at lower thresholds, then protection effectiveness is improved, but false triggering increases
Solution Approach 1:
The patent employs adjustable threshold parameters for both overvoltage and overcurrent detection. The first detection circuit monitors voltage across the power switch against a predetermined overvoltage threshold, while the second detection circuit monitors current through the power switch against a predetermined overcurrent threshold. These parameters can be optimized during design to balance sensitivity with false triggering prevention.
Solution Approach 2:
The controller continuously monitors voltage and current parameters and provides feedback control. When overvoltage or overcurrent conditions are detected, the controller immediately stops generating gate drive signals, creating a feedback loop that prevents further damage. This rapid feedback mechanism allows for effective protection while maintaining stable operation during normal conditions.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Driver circuitry for driving a power semiconductor switch is described. The power semiconductor switch has a control input and main terminals. The driver circuitry includes control terminal driver circuitry configured to be coupled to the control input of the power semiconductor switch and provide a drive signal thereto; a sense terminal configured to be coupled to a main terminal of the power semiconductor switch; a current mirror coupled to the sense terminal to mirror a current input into the sense terminal during turn-off; a first current comparator coupled to compare a current signal received from the current mirror to a first current threshold and output a first signal representative of a result of the comparison; and a second comparator coupled to compare a signal received from the sense terminal to a turn-on threshold and output a second signal representative of a result of the comparison. The turn-on threshold represents a highest voltage of the main terminal during turn-on. The first current threshold represents a highest voltage of the main terminal during turn-off.