Parallel Inverter Current Sensing for Plausibility Fault Detection
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Solution Overview
Problem
Inverter circuits used in electric machines, particularly in hybrid or all-electric vehicles, face challenges in ensuring functional safety for torque control due to the need for redundant current sensor measurements, which can be costly and complex.
Innovation Solution
The proposed solution involves an inverter circuit with a low-side and high-side configuration, where one current sensor measures current through a single semiconductor switching element, and another sensor measures current through all parallel-connected switching elements. This redundancy allows for cost-effective and reliable fault detection by comparing the currents measured by each sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple current sensors are used per phase winding for redundant measurement, then functional safety and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the current measurement function into two distinct sensor types: one sensor measures current through a single semiconductor switching element, while another sensor measures current through all parallel-connected switching elements. This segmentation allows redundant measurement without requiring multiple sensors for each phase winding, thereby reducing overall system complexity while maintaining functional safety
Solution Approach 2:
The control unit acts as an intermediary that processes and compares measurements from the two different sensor types. By using the control unit to perform the comparison and plausibility check, the patent avoids the need for additional dedicated comparison hardware, thus reducing device complexity while ensuring reliable fault detection
2Reliability
If multiple current sensors are used per phase winding for redundant measurement, then fault detection capability is improved, but cost increases
Solution Approach 1:
The patent makes the current sensors serve multiple functions: they provide both primary current measurement for control and redundant measurement for fault detection. The same sensors are used for both torque control and safety monitoring, eliminating the need for separate redundant sensors and thereby reducing cost
Solution Approach 2:
The system uses its existing current sensors to perform self-diagnosis and fault detection by comparing their measurements. This self-service approach eliminates the need for additional dedicated fault detection sensors, reducing manufacturing cost while maintaining fault detection capability
3Adaptability or versatility
If current sensors measure current through all parallel-connected switching elements, then measurement range requirements increase, but sensor placement flexibility is improved
Solution Approach 1:
The patent applies local quality by having different sensors measure different portions of the current: one sensor measures current through a single switching element (local measurement), while another measures current through all parallel-connected elements (aggregate measurement). This allows each sensor to be optimized for its specific measurement range while providing complementary information for fault detection
Data Source
AI summary
An inverter circuit has a low side which has a plurality of controllable semiconductor switching elements connected in parallel with one another between a first DC voltage terminal and a center terminal of the inverter circuit, and a high side which has a plurality of controllable semiconductor switching elements connected in parallel with one another between a second DC voltage terminal and the center terminal of the inverter circuit. The inverter circuit also has a first current sensor, connected in series with exactly one of the switching elements and adapted to measure a first current which flows through the switching element, and a second current sensor, arranged between the center terminal and an output terminal of the inverter circuit and adapted to measure a second current. The first current and the second current are recorded. The second current is then checked for plausibility with the first current.