Semiconductor Switch Fault Checking Across PWM Duty Cycles
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Solution Overview
Problem
Existing methods for diagnosing faults in semiconductor switches using PWM signals with variable duty cycles are unreliable, especially at high or low duty cycles, and are heavily dependent on environmental conditions such as supply voltage, making it difficult to detect faults like high-resistance short circuits or interruptions.
Innovation Solution
The method evaluates changing voltage levels across the semiconductor switch, counting voltage pulses to determine faults independently of environmental conditions, and uses a capacitor to generate short-term pulses for evaluation, which are processed through a simple A/D converter and controller to detect errors like short circuits or interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current or voltage measurements are taken to test semiconductor switch faults, then fault detection capability is improved, but reliability deteriorates at high or low duty cycles where measurements become indistinguishable from permanent faults
Solution Approach 1:
The patent introduces an intermediary measurement approach by monitoring the control signal to the semiconductor switch rather than directly measuring current or voltage across the switch. This intermediary measurement of the control signal's presence and characteristics allows fault detection without the ambiguity that occurs when duty cycles are extremely high or low, where traditional electrical measurements become indistinguishable from permanent fault conditions
Solution Approach 2:
The patent replaces the traditional electrical measurement system (current/voltage probes on the power circuit) with a control signal monitoring system. By substituting the measurement mechanism to observe the control side rather than the power side, the system achieves reliable fault detection across all duty cycle ranges without being affected by the electrical conditions that plague traditional methods
2Ease of manufacture
If pure current measurement is used for fault detection, then implementation simplicity is improved, but reliability deteriorates due to strong dependence on environmental variables such as supply voltage
Solution Approach 1:
The patent uses the control signal as an intermediary that is independent of environmental variables like supply voltage. By monitoring whether the control signal is present and its characteristics rather than measuring power circuit parameters, the system achieves environmental independence while maintaining implementation simplicity through straightforward signal presence detection
Solution Approach 2:
The patent changes the measurement parameter from electrical quantities (current, voltage) that are heavily influenced by environmental conditions to control signal parameters (presence, timing, logic state) that are inherently stable and independent of supply voltage and load variations, thereby achieving reliable fault detection across varying environmental conditions
Data Source
Figure 1~2
AI summary
The invention provides a method for checking a semiconductor switch for a fault, wherein the semiconductor switch is driven with a PWM signal with a variable duty cycle. To the benefit of determining faults on the semiconductor switch reliably and cost-effectively, it is provided that if the semiconductor switch is operated with a duty cycle of 100% or 0%, the current measurement of the overall system is evaluated, while if the semiconductor switch is operated with a duty cycle of between 0% and 100%, the generated voltage pulses across the semiconductor switch are evaluated.