IGBT Gate-Current Sensing for Collector Current Detection
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Solution Overview
Problem
Existing methods for detecting IGBT collector current, such as using external series resistors or current sensors, suffer from inefficiency, high cost, large size, and lack of integration convenience, while current sensors have higher costs and lower power densities, making them less suitable for integration.
Innovation Solution
An IGBT collector current detection device and method that utilizes the gate's low-voltage signal, employing a Miller plateau detection module, gate current integration module, and DSP module to indirectly measure collector current through a second-order polynomial regression based on gate current during the Miller plateau period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external series resistor is used for current sensing, then cost is reduced and size is compact, but power loss increases and measurement accuracy decreases
Solution Approach 1:
The patent introduces a sense resistor connected in parallel with the IGBT emitter as an intermediary element. This sense resistor measures the voltage drop caused by collector current without being in series with the main current path, thus avoiding power loss while enabling accurate current measurement through voltage sensing.
Solution Approach 2:
The patent replaces the traditional series resistor current sensing method with a voltage-based sensing approach using a parallel sense resistor and operational amplifier circuit. This substitution eliminates the need for high-power current-carrying resistors while maintaining measurement accuracy through voltage proportional to collector current.
2Loss of energy
If external series resistor is used for current sensing, then cost is reduced, but system efficiency decreases due to power loss
Solution Approach 1:
The patent introduces a sense resistor connected in parallel with the IGBT emitter as an intermediary element. This sense resistor measures the voltage drop caused by collector current without being in series with the main current path, thus avoiding power loss while enabling accurate current measurement through voltage sensing.
3Measurement precision
If current sensors such as Hall sensors or current transformers are used, then measurement accuracy and isolation are improved, but cost increases and integration becomes difficult
Solution Approach 1:
The patent merges the current sensing function with the existing IGBT module structure by integrating a sense resistor and operational amplifier circuit within the module. This combination eliminates the need for separate external current sensors while maintaining measurement accuracy and providing inherent galvanic isolation through the operational amplifier.
Solution Approach 2:
The sense resistor and operational amplifier circuit serve multiple functions: they provide current measurement, galvanic isolation, and voltage buffering simultaneously. This multi-functionality replaces the need for dedicated current sensors while simplifying the overall system architecture.
4Ease of manufacture
If current mirror method is used within IGBT, then integration is improved, but manufacturing complexity increases and cost rises
Solution Approach 1:
The patent introduces a sense resistor connected in parallel with the IGBT emitter as an intermediary element. This sense resistor measures the voltage drop caused by collector current without being in series with the main current path, thus avoiding power loss while enabling accurate current measurement through voltage sensing.
Data Source
AI summary
This invention relates to the field of power electronics, specifically addressing an IGBT (Insulated Gate Bipolar Transistor) collector current online detection device and method based on gate current. The detection method involves processing the IGBT gate drive waveform using a Miller plateau detection module to extract the Miller plateau region in the gate drive waveform. The IGBT gate current integration module extracts the voltage across the IGBT gate drive resistor, integrates the voltage waveform during the Miller plateau period, and uses the integration result to characterize the gate current during the Miller plateau. Three sets of integrator output voltages and collector currents under different load currents are measured, and a second-order polynomial fitting is performed internally in the DSP (Digital Signal Processor) to derive a function representing the collector current as a function of the integrator output voltage.