Safe Disconnect Circuit for IPM Fault Isolation
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Solution Overview
Problem
High-voltage, high-current integrated power modules (IPMs) pose safety hazards when control signals are lost, as they often remain in an 'on' condition, and existing solutions fail to differentiate between spurious and fault conditions, leading to potential damage or hazardous situations.
Innovation Solution
A safe disconnect circuit that detects input signals with amplitudes and durations below preset thresholds, using an RC circuit and optical coupler to maintain the load in an 'off' state until a proper signal is received, and electrically isolates the load to prevent hazardous conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the IPM operates in a normally on condition to avoid unnecessary switching, then the module remains stable and avoids spurious switching, but loss of control signal due to faults cannot be detected and the module cannot be safely turned off
Solution Approach 1:
An optical coupler is introduced as an intermediary component between the control circuit and the IPM. The optical coupler receives control signals, converts them to optical signals for transmission, and then back to electrical signals to drive the IPM. This mediator allows the system to maintain normal operation while enabling fault detection through monitoring of the optical coupling path, resolving the contradiction between operational stability and fault detection capability.
2Device complexity
If the control circuit directly controls the IPM without electrical isolation, then the control is simple and direct, but hazardous conditions can occur due to electrical interference or faults between the input circuit and the IPM
Solution Approach 1:
The optical coupler serves as an electrical isolation barrier between the low-voltage control circuit and the high-voltage IPM. It converts electrical control signals to optical signals, transmits them through an optically isolated path, and then converts them back to electrical signals. This intermediary approach provides electrical isolation to eliminate harmful electrical interference while maintaining effective control, accepting the added complexity as necessary for safety.
3Reliability
If the circuit responds to any control signal variation by shutting down the IPM, then safety is prioritized, but spurious signals cause unnecessary shutdowns and operational disruption
Solution Approach 1:
The system uses parameter thresholds to distinguish between valid control signals and spurious variations. The control circuit is designed to recognize specific signal characteristics (amplitude, pulse width, timing patterns) that define legitimate shutdown commands versus noise or interference. By changing the response parameters based on signal validation, the system maintains safety while avoiding unnecessary shutdowns, resolving the contradiction between reliability and productivity.
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 prevents damage by distinguishing between spurious and fault conditions, ensuring safe shutdown and isolation of high-voltage, high-current loads, thereby mitigating risks associated with IPM operation.
Implementation Method 1
an optical coupler circuit disposed intermediate the switch and the load, the optical coupler circuit being operative to electrically isolate the load from the switch
Implementation Method 2
an RC circuit for maintaining a load in an off condition until such time as the switching circuit detects the presence of a proper input signal
Data Source
AI summary
A safe disconnect circuit is provided for mitigating the effect of harmful circuit conditions upon a load, such as an integrated power module (IPM). The safe disconnect circuit comprises a switching circuit operative to receive a pulsed input signal, and to detect the presence of a load threatening input signal, e.g. a load control signal, having an amplitude below a preset amplitude threshold and a duration beyond a present duration threshold. The switching circuit is operative to terminate load power in response to detect a presence of the load threatening signal.