PWM Drive Current Detection Using Period Identification
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Solution Overview
Problem
Conventional fault detection devices for PWM load devices struggle to accurately detect faults due to variations in duty ratio, leading to incorrect current calculations and incomplete fault detection.
Innovation Solution
A drive current detection device that periodically samples the current flowing through the load device, identifies the current-driven period, and selects sampled values from this period to calculate the drive current value, enabling accurate fault detection by excluding current values from the non-conducting period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fault detection devices sample current at arbitrary timing for PWM load devices, then the device complexity is low, but the measurement precision of drive current is inaccurate due to duty ratio variations
Solution Approach 1:
The system performs preliminary identification of the current-driven period before selecting sampled values for drive current calculation. By determining the ON period of the PWM signal in advance, the system ensures that only relevant current samples are used, eliminating measurement errors caused by duty ratio variations while maintaining a relatively simple device structure.
Solution Approach 2:
The system changes the parameter selection criteria from arbitrary timing to timing based on the identified current-driven period. By dynamically adjusting which sampled values are used for calculation based on the PWM ON period, the system achieves accurate drive current measurement across varying duty ratios without significantly increasing device complexity.
2Reliability
If fault detection uses arbitrary timing current sampling, then the ease of operation is high, but the reliability of fault detection is poor due to incorrect drive current calculation
Solution Approach 1:
The system performs preliminary identification of the current-driven period before fault detection. This preliminary action ensures that subsequent fault detection operations use accurate drive current values, significantly improving reliability while adding minimal operational complexity since the period identification occurs automatically in the background.
Solution Approach 2:
The system uses feedback from the identified current-driven period to guide the selection of sampled values for drive current calculation. This feedback mechanism ensures that fault detection always uses relevant current samples, improving reliability while maintaining ease of operation through automated feedback-based selection.
3Measurement precision
If all sampled values are used for drive current calculation regardless of timing, then the productivity of fault detection is high, but the measurement precision deteriorates due to inclusion of non-conducting period current values
Solution Approach 1:
The system extracts only the sampled values that occur during the current-driven period for drive current calculation, excluding samples from the non-conducting period. This extraction approach improves measurement precision by eliminating erroneous current values while maintaining processing efficiency by using a clear selection criterion based on the identified ON period.
Solution Approach 2:
The system applies different quality criteria to different sampled values based on their timing within the PWM cycle. Samples during the current-driven period are selected for calculation, while samples during the non-conducting period are excluded. This local quality approach ensures high measurement precision without significantly impacting processing efficiency.
Data Source
AI summary
It is an object of the invention to, in fault detection of a PWM load device, provide a fault detection device and a fault detection method, which are capable of appropriately detecting fault of the load device in the case where such load device is connected the duty ratio of the PWM waveform of which is different, or where such load device is connected the magnitude of current of which is different. The fault detection device samples a current flowing through the load device on a predetermined cycle, decides, based on sampled values, a current-driven period and decides, by using sampled values in the current-driven period, a drive current value for determining whether or not there is a fault.