USB PD Power Control for Inrush-Tolerant Overcurrent Switching
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Solution Overview
Problem
In USB-Type-C PD systems, the supply of electric power stops due to overcurrent detection before current stability is achieved, leading to potential misinterpretation of malfunctions, as inrush currents exceeding set limits can occur during negotiation and voltage changes.
Innovation Solution
A power control device with first and second overcurrent detecting units and a timer unit that performs overcurrent detection using different criterion values before and after negotiation, preventing unnecessary power supply shutdown by validating detection based on the first criterion value after the negotiation and voltage stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent detection is performed using a fixed criterion value during power supply, then overcurrent protection is provided, but power supply stops during normal inrush current periods
Solution Approach 1:
The patent applies dynamics by making the overcurrent criterion value changeable based on the operational state. The control unit dynamically switches between a first criterion value (higher) during negotiation/voltage change periods and a second criterion value (lower) during stable operation periods. This resolves the contradiction by allowing the system to tolerate higher currents during transient states while maintaining strict protection during normal operation.
Solution Approach 2:
The patent applies preliminary action by setting a timer that counts down from a predetermined period when power supply starts or voltage changes occur. During this predetermined period (before the timer reaches zero), the system uses the first criterion value to accommodate expected inrush currents. This preliminary preparation prevents false overcurrent detection during normal voltage stabilization processes.
2Productivity
If overcurrent detection is invalidated during negotiation period, then power supply continuity is maintained, but real overcurrents cannot be detected
Solution Approach 1:
The system dynamically adjusts detection sensitivity based on timing. The control unit activates the first overcurrent detecting unit (with higher threshold) during the negotiation period when the timer is counting down, and switches to the second overcurrent detecting unit (with lower threshold) when the timer reaches zero. This temporal differentiation allows the system to maintain both continuity during negotiation and accuracy during stable operation.
3Device complexity
If a single overcurrent criterion value is used, then detection simplicity is maintained, but false malfunction indications occur during voltage changes
Solution Approach 1:
The patent segments the overcurrent detection function into two distinct detecting units: a first overcurrent detecting unit with a first criterion value for use during negotiation periods, and a second overcurrent detecting unit with a second criterion value for use during stable operation. This segmentation allows each unit to be optimized for its specific operational context, reducing false malfunctions while maintaining manageable complexity through clear temporal separation of their usage.
Data Source
AI summary
A first overcurrent detecting unit to detect whether or not a current supplied from a power source unit to an external device exceeds a first criterion value. A second overcurrent detecting unit to detect whether or not the current supplied from the power source unit to the external device exceeds a second criterion value that is a criterion value higher than the first criterion value, a timer unit in which a time corresponding to a time from a time point at which switching from electric power supplied from the power source unit to the external device in a period, in which a negotiation is performed, to electric power corresponding to a result of the negotiation with the external device is performed to a time before the supply of the electric power becomes stable is set. A control unit is to perform overcurrent detection using the second overcurrent detecting unit before the negotiation ends and, when the negotiation ends, and the time set in the timer unit elapses, invalidate the overcurrent detection using the second overcurrent detecting unit and validate the overcurrent detection using the first overcurrent detecting unit are included.