IGBT Drive Circuit With Fault-Triggered Soft Turn-Off
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Solution Overview
Problem
The simple drive circuit for power semiconductor switches lacks a stable power supply, making traditional soft turn off circuits and active clamping circuits inapplicable, which can lead to voltage spikes during overcurrent/short-circuit faults, compromising the reliability and scope of application.
Innovation Solution
A drive circuit with a pulse modulation circuit, isolation transformer, and pulse demodulation circuit that adjusts turn off pulse signals based on fault conditions, reducing voltage spikes by controlling the gate capacitor discharge, thereby enhancing reliability and applicability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional soft turn off circuits or active clamping circuits are used, then voltage spikes are suppressed and IGBT modules are protected, but the circuit complexity increases and these circuits are not applicable to simple drive configurations
Solution Approach 1:
The patent extracts the essential protection function from complex traditional circuits and implements it through a simplified approach: using a capacitor connected in parallel with the IGBT gate-emitter terminals and controlling its discharge through a resistor. This extracts only the necessary elements (capacitor, resistor, control circuit) needed for soft turn-off protection, eliminating unnecessary circuit components while maintaining protection capability.
Solution Approach 2:
The patent makes the simple drive circuit universally applicable by designing a protection mechanism that works within the existing simple drive architecture. The capacitor-based soft turn-off circuit serves multiple functions: it provides voltage spike suppression, enables controlled turn-off during faults, and maintains compatibility with the simple drive configuration, thus achieving multi-functionality without requiring separate dedicated protection circuits.
2Speed
If the IGBT is turned off quickly to respond to short-circuit faults, then protection response time is reduced, but voltage spikes increase due to stray inductance and large di/dt
Solution Approach 1:
The patent applies beforehand cushioning by pre-charging a capacitor during the IGBT on-state and then controlling its discharge during turn-off. The capacitor acts as a cushion that absorbs the voltage spike energy that would otherwise be generated by the stray inductance and large di/dt. By preparing the capacitor in advance and controlling its discharge rate through a resistor, the circuit cushions against voltage spikes while maintaining fast fault response.
Solution Approach 2:
The patent implements dynamic control of the turn-off process by using a controlled capacitor discharge mechanism. Instead of a fixed turn-off speed, the circuit dynamically adjusts the discharge rate through the resistor, allowing fast turn-off under normal conditions and controlled soft turn-off during faults to minimize voltage spikes. This dynamic approach optimizes both speed and voltage spike suppression.
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
Effectively reduces voltage spikes during IGBT turn off in overcurrent/short-circuit faults, improving the reliability and scope of application of the simple drive circuit, while maintaining a simple and cost-effective structure.
Implementation Method 1
The pulse signal is transmitted to the drive board through the isolation transformer
Implementation Method 2
the energy pulse signal and the drive pulse signal charge/discharge a gate capacitor of the IGBT
Data Source
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AI summary
A drive circuit of a power semiconductor switch includes: a pulse modulation circuit (1) having a first terminal configured to receive a fault signal, an isolation transformer (2), and a pulse demodulation circuit (3); when there is no fault signal being received, the pulse modulation circuit outputs a first turn on pulse signal and a first turn off pulse signal via the isolation transformer and the pulse demodulation circuit to charge/discharge a gate capacitor of the power semiconductor switch, so as to drive the power semiconductor switch to be turned on and turned off at a first speed; when the fault signal is received, the pulse modulation circuit outputs a second turn off pulse signal via the isolation transformer and the pulse demodulation circuit to discharge the gate capacitor of the power semiconductor switch, so as to drive the power semiconductor switch to be turned off at a second speed.