Parallel IGBT Drive Monitoring via Transformer Isolation
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Solution Overview
Problem
In high-capacity power conversion applications, monitoring the status of parallel-connected power switching devices, such as IGBTs, is challenging due to the need for precise detection of failures to prevent damage and ensure continued operation or safe shutdown, especially in large-scale UPS systems where multiple devices are connected in parallel.
Innovation Solution
A drive circuit and monitoring circuit system is implemented, which includes transformers with secondary windings coupled to gate drive nodes and current sensors to sense primary winding currents, allowing for the determination of drive signals and statuses of individual power switching devices, including detection of the Miller effect and failure modes, with galvanic isolation and filtering to provide accurate status information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple power switching devices are connected in parallel to provide increased current capacity, then the current capacity is improved, but the difficulty of detecting and measuring the status of individual devices increases
Solution Approach 1:
The patent divides the monitoring function into individual segments for each power switching device. Each device has its own dedicated monitoring circuit that independently measures drive signals and status parameters, allowing individual device monitoring even when multiple devices are connected in parallel. This segmentation enables precise tracking of each device's operational state without interference from other parallel devices.
Solution Approach 2:
The patent introduces intermediary monitoring circuits and measurement devices that act as mediators between the parallel-connected power switching devices and the control system. These intermediaries capture drive signals, collector-emitter voltages, and other status parameters, converting them into measurable and reportable forms. This intermediary layer enables indirect but accurate monitoring of individual device status while maintaining the parallel configuration.
2Reliability
If monitoring circuits are added to detect the status of power switching devices, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple monitoring functions into integrated monitoring circuits that simultaneously measure drive signals, collector-emitter voltages, and other parameters. By merging these functions into unified circuits rather than separate dedicated circuits for each parameter, the overall system complexity is reduced while maintaining comprehensive monitoring capability. The monitoring circuits are designed to perform multiple measurements using shared components and signal paths.
Solution Approach 2:
The monitoring circuits are designed with multi-functionality, serving multiple purposes: detecting drive signals, monitoring collector-emitter voltage, identifying failure modes, and providing diagnostic information. This universal approach allows a single monitoring circuit to perform various monitoring tasks, reducing the need for multiple specialized circuits and thereby lowering overall system complexity while improving reliability through comprehensive monitoring.
3Reliability
If precise monitoring of individual devices is implemented, then the reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent implements feedback mechanisms where monitoring circuits continuously measure actual device parameters and feed this information back to the control system. This feedback enables real-time adjustment and compensation, allowing the system to maintain reliable operation even with variations in manufacturing precision. The feedback loop detects deviations caused by manufacturing tolerances and compensates for them through control adjustments, reducing the stringency of manufacturing precision requirements.
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 system enables effective monitoring and management of parallel-connected power switching devices, allowing for timely detection of failures, enabling continued operation with reduced capacity or safe shutdown, and facilitating maintenance by identifying failed devices and logging events for analysis.
Implementation Method 1
The drive circuit may include respective transformers having respective secondary windings coupled to respective ones of the gate drive nodes, and a primary driver circuit configured to drive primary windings of the transformers
Implementation Method 2
current sensors may include respective current sense resistors coupled in series with the respective primary windings
Implementation Method 3
The monitoring circuit may further include a filter circuit configured to filter respective voltages across the respective current sense resistors to generate filtered voltages indicative of drive delivered to the respective drive nodes
Data Source
AI summary
An apparatus, such as an inverter or rectifier in a double-conversion UPS, includes a plurality of power switching devices, such as IGBTs, coupled in parallel. A drive circuit is coupled to the power switching devices at a plurality of drive nodes and configured to drive the drive nodes responsive to a drive control signal. A monitoring circuit is coupled to the drive circuit and configured to determine respective statuses of respective ones of the power switching devices. The monitoring circuit may be configured to generate respective measures of drive delivered to respective ones of the drive nodes.