Smart Card Circuit Grounding Sequence for SIM Safety
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Solution Overview
Problem
SIM cards are prone to being burned out when detached from a card holder, either due to improper power-off sequences during normal use or during drop tests, leading to damage or failure.
Innovation Solution
A smart card connection circuit incorporating a travel switch and a switching unit that grounds signal cables before power cables, ensuring a controlled power-off sequence when the SIM card is removed, using resistors and GPIO interfaces for precise control and safe detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the SIM card is detached from the card holder during normal use or drop tests, then the SIM card can be removed or replaced, but the SIM card is prone to being burned out due to improper power-off sequences
Solution Approach 1:
The travel switch detects SIM card detachment in advance and triggers the switching unit to ground signal cables before power cables, ensuring the correct power-off sequence occurs automatically before the SIM card is fully removed, preventing burnout while maintaining ease of operation
Solution Approach 2:
The travel switch acts as an intermediary that detects SIM card position and controls the switching unit to implement the proper power-off sequence, mediating between the physical removal action and the electrical safety requirements
2Reliability
If a travel switch and switching unit are added to control the power-off sequence, then SIM card safety is improved, but the device complexity increases
Solution Approach 1:
The power-off control function is extracted from the main system and implemented through a separate, dedicated switching unit triggered by the travel switch, isolating the safety mechanism from the main device complexity while ensuring reliable operation
Data Source
AI summary
A smart card connection circuit of an electronic device which includes a card holder, a travel switch, and a switching unit; a contact of the travel switch is located in the card holder, and an output end of the travel switch is connected to a control end of the switching unit; and when a smart card at a preset position in the card holder leaves the preset position, the smart card leaves the contact of the travel switch, the travel switch controls the switching unit to switch to a second output end, and each signal cable pin on the card holder is grounded by using the switching unit before a power cable pin on the card holder is grounded by using the switching unit. The present invention is applied to electronic devices such as a mobile phone and a tablet computer.