Isolated Gate Drive Circuit for Soft Turn-Off Fault Protection
Find Innovative SolutionsGenerate Solutions
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 unsuitable, 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 pulse width and amplitude to control the gate capacitor of the power semiconductor switch, allowing for controlled turn on and turn off operations, including a fault signal-based second turn off pulse with reduced voltage amplitude and equal pulse width to achieve soft turn off.
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 second turn-off pulse signal with reduced voltage amplitude applied to the gate capacitor. This extracts only the necessary elements (gate voltage control) while removing unnecessary complexity (separate protection circuits, stable power supply requirements), achieving protection without increasing device complexity.
Solution Approach 2:
The drive circuit achieves multi-functionality by using the same pulse modulation circuit and isolation transformer for both normal operation and fault protection. The second turn-off pulse signal with reduced amplitude serves dual purposes: it enables soft turn-off protection while maintaining compatibility with the simple drive architecture, eliminating the need for separate protection circuits.
2Speed
If the IGBT is turned off quickly when short circuit occurs, then the protection response is fast, but larger di/dt generates larger spike voltage that may damage the IGBT module
Solution Approach 1:
The patent applies dynamics by making the turn-off speed adjustable through pulse amplitude modulation. During fault conditions, the second turn-off pulse signal uses reduced voltage amplitude to slow down the turn-off process, dynamically adapting the switching speed to minimize voltage spikes while still providing timely protection. This resolves the contradiction between fast response and voltage spike suppression.
Solution Approach 2:
The patent changes the voltage amplitude parameter of the turn-off pulse signal to control the turn-off speed. By reducing the voltage amplitude of the second turn-off pulse signal compared to normal operation pulses, the gate capacitor discharges more slowly, reducing di/dt and consequently reducing voltage spikes while maintaining acceptable protection response time.
3Stability of the object's composition
If refresh pulse signals are used to maintain gate voltage, then the gate capacitor discharge is compensated, but the circuit complexity increases and power consumption increases
Solution Approach 1:
The patent employs periodic refresh pulse signals to maintain gate voltage stability during normal operation. These periodic pulses compensate for gate capacitor discharge without requiring complex continuous power supply circuits. The periodic nature of the refresh pulses simplifies the circuit design while maintaining voltage stability, resolving the contradiction between stability and complexity.
4Stability of the object's composition
If the pulse width of the pulse signal is limited to a few microseconds, then the magnetic core saturation is avoided, but the gate capacitor cannot be charged to the required VGE value for longer drive signals
Solution Approach 1:
The patent applies preliminary action by charging the gate capacitor to the required voltage level before the actual drive signal needs to be generated. The isolation transformer and pulse modulation circuit prepare the gate capacitor in advance during normal operation, so when a fault occurs and the second turn-off pulse is needed, the capacitor is already charged and ready to provide the necessary voltage without requiring extended pulse widths that could saturate the magnetic core.
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 faults, enhances reliability, and expands the application scope of the simple drive circuit by providing a flexible and efficient control mechanism for power semiconductor switches.
Implementation Method 1
an isolation transformer, including a first primary terminal, a second primary terminal, a first secondary terminal, and a second secondary terminal; the first primary terminal is coupled to the second terminal of the pulse modulation circuit, and the second primary terminal is coupled to the third terminal of the pulse modulation circuit
Implementation Method 2
charges/discharges a gate capacitor of the power semiconductor switch via the demodulation circuit based on the at least one first turn on pulse signal and the at least one first turn off pulse signal to drive the power semiconductor switch to be turned on and turned off
Data Source
AI summary
A drive circuit of a power semiconductor switch includes: a pulse modulation circuit having a first terminal configured to receive a fault signal, an isolation transformer, and a pulse demodulation circuit; 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.