Gate Current Mirror Protection in Current Source Converter Switching
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Solution Overview
Problem
Current source power converters face the risk of current interruption during switching between upper or lower switching devices, which can lead to overvoltage peaks and potential destruction of power converter components.
Innovation Solution
A control circuit is implemented to detect when an upper or lower current conducting switching device is turned off before another is turned on, triggering a protection circuit to create a conductive path at the poles of the current generator, preventing overvoltage peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If overlapping time between switching devices is reduced, then Total Harmonic Distortion (THD) of output current is improved, but the risk of open circuit situation increases due to timing mismatches
Solution Approach 1:
The protection circuit is activated in advance by detecting the turn-off of the first switching device before the turn-on of the second switching device. This preliminary detection triggers the creation of a conductive path through the protection switch, ensuring that if timing mismatch occurs, the circuit is already prepared to handle the open circuit condition, thus resolving the contradiction between reduced overlapping time and increased open circuit risk
2Reliability
If overlapping time between switching devices is increased, then open circuit risk is reduced, but conduction losses increase due to body diode conduction
Solution Approach 1:
The protection circuit creates a conductive path in advance when the first switching device turns off, allowing current to continue flowing through the protection switch rather than through the body diode. This preliminary action prevents the need for extended overlapping time, thereby reducing conduction losses while maintaining reliability
3Productivity
If switching speed is increased, then converter efficiency is improved, but overvoltage peaks occur due to abrupt current changes
Solution Approach 1:
The protection circuit is triggered in advance when the first switching device turns off, creating a conductive path before the second switching device turns on. This preliminary action allows for faster switching speeds by providing a safe current path that prevents overvoltage peaks, thus resolving the contradiction between switching speed and overvoltage generation
Data Source
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AI summary
Control circuit for a current source converter having a current generator comprising an inductance (2) and having two or more half bridges each half bridge having an upper leg provided with an upper switching device (11, 13) and a lower leg provided with a lower switching device (12, 14), said upper legs switching devices and said lower legs switching devices being controlled by a controller (40) to provide an overlap between an upper leg turning off and an upper leg turning on switching device and to provide an overlap between a lower leg turning on switching device and a lower leg turning off switching device through gate pull up and gate pull down pulse signals to gate drivers buffers (6) of said switching devices, where said gate driver circuit comprises: - for each switching device (11, 12, 13, 14) a gate current mirroring circuit (5) on a sink branch of the gate driver buffer (6) of such switching device (11, 12, 13, 14) to provide a gate pull down detection signal (Im) from a turning OFF switching device, - for each switching device (11, 12, 13, 14) a gate command connection path to provide a gate command signal (G), at least one logic circuit combining a gate command signal (G) of a first upper or lower leg switching device and a gate pull down signal of a respectively second upper or lower leg switching device to provide a first protection trigger signal (Pr), when said gate command signal of said first upper or lower leg switching device and said gate pull down detection signal of said respective second upper or lower leg switching device correspond to both said first and second upper leg switching devices or both said first and second lower leg switching devices being OFF; converter having such a control circuit.