Parallel RC-IGBT Gate Voltage Control Near Current Zero Crossing
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Solution Overview
Problem
The existing methods for controlling reverse conductive semiconductor switches in parallel circuits face challenges in reducing switching losses and accurately detecting current zero crossings, leading to potential damage and EMC issues due to the lack of precise control over diode behavior and high di/dt during current reversal.
Innovation Solution
The method involves controlling individual RC-IGBTs in parallel circuits with different gate-emitter voltages, allowing some switches to operate with negative and others with positive voltages, especially near current zero crossings, to distribute current efficiently and reduce losses, thereby simplifying current direction detection and reducing the need for precise zero crossing determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If all parallel semiconductor switches are controlled with the same gate voltage, then the control system is simple, but switching losses increase and current distribution is uneven
Solution Approach 1:
The control system is segmented into multiple independent control channels, each controlling a specific semiconductor switch in the parallel circuit. This allows different gate-emitter voltages to be applied to different switches, enabling optimized current distribution and reduced switching losses while maintaining manageable control complexity through modular architecture
Solution Approach 2:
Different gate-emitter voltages are applied to different semiconductor switches based on their individual operating conditions and current requirements. This local differentiation of control parameters enables each switch to operate optimally, reducing overall switching losses while the modular control architecture prevents excessive system complexity
2Reliability
If the zero crossing of load current is determined with high accuracy, then the transition between IGBT mode and diode mode is precise, but the control system complexity and measurement cost increase
Solution Approach 1:
The control system prepares the semiconductor switches for mode transition in advance by monitoring current trends and pre-adjusting gate-emitter voltages before the actual zero crossing occurs. This preliminary preparation ensures reliable mode transition without requiring extremely precise real-time zero crossing detection, thereby reducing measurement and control system complexity while maintaining high reliability
Solution Approach 2:
The control system uses feedback from current measurements to dynamically adjust gate-emitter voltages of parallel semiconductor switches. This feedback mechanism ensures accurate mode transition by continuously monitoring operating conditions and making real-time control adjustments, achieving high reliability without excessive system complexity through intelligent control algorithms
3Speed
If the diode current decreases too quickly at low load currents, then the switching speed is high, but voltage spikes occur and EMC problems arise
Solution Approach 1:
The gate-emitter voltage of each semiconductor switch is dynamically adjusted based on the instantaneous current conditions. During low current periods, the control system modifies the gate voltage to regulate the rate of current decrease, maintaining high switching speed while preventing excessive di/dt that would cause voltage spikes and EMC problems
Solution Approach 2:
The control system changes the gate-emitter voltage parameter of semiconductor switches to optimize diode current behavior. By adjusting this parameter, the system controls the rate of current decay during switching transitions, achieving high switching speed while limiting di/dt to prevent voltage spikes and electromagnetic interference
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
This approach reduces switching losses, prevents current break-off, and simplifies current direction detection, leading to improved switching behavior and economic advantages by eliminating the need for expensive high-accuracy current measurements.
Implementation Method 1
Operation in IGBT mode requires a positive gate-emitter voltage (open channel for current flow)
Implementation Method 2
Conversely, if current flows from the emitter to the collector, the reverse-conducting IGBT operates in diode mode
Data Source
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AI summary
The invention relates to a method for actuating at least two reverse-conducting semiconductor switches (1), the at least two reverse-conducting semiconductor switches (1) being arranged in a parallel circuit (2). To improve the switching response, it is proposed that at least two of the reverse-conducting semiconductor switches (1) arranged in a parallel circuit be actuated at least intermittently using a different voltage. The invention further relates to a switching element (3) having two reverse-conducting semiconductor switches (1) arranged in a parallel circuit (2) and an actuating unit (4) or at least a part (5) of an actuating unit (4) for actuating the reverse-conducting semiconductor switches (1), wherein a current sensor (6) for detecting a load current (iL) flowing through the parallel circuit (2) is connectable to a control assembly (7) for evaluating measured values of the current sensor (6), the actuating unit (4) or the part (5) of the actuating unit (4) being able to be used to actuate the individual reverse-conducting semiconductor switches (1) using different voltages in each case.