Power Semiconductor Switch Control Device Overcurrent Protection
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Solution Overview
Problem
Conventional power semiconductor switches face challenges in rapidly detecting overcurrents and withstanding parasitic voltages, leading to potential damage and spurious tripping during switch-on due to delayed protection mechanisms.
Innovation Solution
A control device for power semiconductor switches is designed with an overcurrent detection circuit and a blocking circuit that generates an actuation voltage to rapidly detect overcurrents and block spurious signals, incorporating a current-sense mechanism to monitor control currents and prevent premature tripping, ensuring reliable and timely switch-off during excessive load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the overcurrent detection circuit monitors the voltage to detect overcurrent, then the detection capability is improved, but the control device becomes susceptible to parasitic voltages causing spurious tripping
Solution Approach 1:
The patent introduces a blocking circuit as an intermediary between the overcurrent detection circuit and the actuation device. This blocking circuit monitors the control current and prevents the overcurrent detection signal from reaching the actuation device during the switch-on phase when control current exceeds a threshold, thereby blocking parasitic voltage effects while allowing genuine overcurrent protection when the switch is off
Solution Approach 2:
The blocking circuit dynamically adjusts the signal transmission based on the control current level and actuation voltage state. It automatically blocks the overcurrent detection signal during switch-on when control current is high, and allows signal transmission during normal operation, creating a time-dependent selective blocking mechanism that adapts to the operational state
2Reliability
If the control device shows high withstand to parasitic voltages by blocking detection signals, then spurious tripping is prevented, but overcurrent detection time is delayed
Solution Approach 1:
The blocking circuit implements dynamic, time-dependent blocking that is active only during the switch-on phase when control current exceeds the threshold. Once the switch is fully on and control current drops below the threshold, the blocking is automatically removed, allowing rapid overcurrent detection. This temporal selectivity prevents parasitic voltage interference during vulnerable periods while enabling fast protection response during critical periods
3Reliability
If the blocking circuit blocks the overcurrent detection signal during switch-on, then spurious tripping is prevented, but the control current monitoring complexity increases
Solution Approach 1:
The blocking circuit serves multiple functions simultaneously: it monitors control current level, compares it against a threshold, generates blocking signals conditionally, and prevents spurious tripping. By consolidating these functions into a single integrated circuit block that leverages existing control current signals, the patent avoids adding separate monitoring systems while achieving reliable parasitic voltage rejection
Data Source
AI summary
A control device for a power semiconductor switch, has a first, second and third electrical control device terminal, and a control device that according to a control signal generates an actuation voltage on the third control device terminal and actuates the power semiconductor switch. An overcurrent detection circuit determines a first voltage corresponding to a primary power semiconductor switch voltage present between the first and second control device terminals and, if the first voltage, further to commence the generation of an actuation voltage for a switch-on of the power semiconductor switch, and if the voltage exceeds a reference voltage, to generate an overcurrent detection signal. A blocking circuit blocks the output of the overcurrent detection signal from the overcurrent detection circuit, if a control current flowing in the third control device terminal for the actuation of the power semiconductor switch exceeds a first current value and/or is designed to block the output of the overcurrent detection signal from the overcurrent detection circuit, if the actuation voltage is smaller than a first voltage value.