Power Supply Switch Failure Detection via Accumulated Off-Periods
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Solution Overview
Problem
Existing power supply control devices fail to properly detect switch-related failures when the switch is not turned on properly, especially in configurations using PWM control, as they do not reach the predetermined voltage threshold within the specified period.
Innovation Solution
A power supply control device and method that include an output unit for producing a switching signal to alternately turn the switch on and off, an on-detection unit to detect the switch's on-state, and a reporting unit to report failures if the accumulated period exceeds a threshold, allowing for proper detection of switch-related failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PWM control is used to supply electric power to the load by turning the switch on and off alternately, then the voltage can be applied at a prescribed average voltage irrespective of varying battery output voltage, but the existing detection method fails to detect switch-related failures because the continuous on-period does not reach the predetermined threshold
Solution Approach 1:
The system performs preliminary accumulation of off-periods before triggering a failure detection. By accumulating the periods when the switch should be on but remains off across multiple PWM cycles, the system prepares the detection threshold in advance, enabling reliable failure detection in PWM control scenarios where individual off-periods are too short.
Solution Approach 2:
The invention transitions from detecting switch status within a single time dimension (individual PWM cycle) to detecting across multiple time dimensions (accumulated periods across multiple cycles). This dimensional expansion allows the system to distinguish between normal PWM off-periods and actual switch failures by accumulating evidence over time.
2Reliability
If the detection period threshold is set to ensure reliable failure detection, then switch failures can be detected in continuous operation, but PWM control becomes impossible because the threshold would be exceeded during normal switching cycles
Solution Approach 1:
The detection mechanism is segmented into separate accumulation and evaluation phases. The accumulation phase continuously tracks off-periods without triggering false alarms, while the evaluation phase determines whether the accumulated value indicates a real failure. This segmentation allows PWM control to operate normally while maintaining reliable failure detection capability.
Solution Approach 2:
The detection threshold is made dynamic by accumulating off-periods over multiple PWM cycles rather than using a fixed threshold. The accumulated value adapts to the PWM duty ratio, allowing the system to distinguish between normal PWM operation (where off-periods are distributed) and actual failures (where off-periods accumulate continuously).
Data Source
AI summary
A power supply control device and a power supply control method capable of detecting a switch-related failure properly are provided. A power supply control device controls power supply via a switch. An output unit of a microcomputer produces a switching signal that instructs the switch to turn alternately on and off. A detection circuit reports a failure related to the switch if an accumulated period has reached or exceeded a threshold period. The accumulated period is accumulation of one or more periods when the switching signal instructs the switch to turn on but a comparator does not detect an on-state of the switch.