Multiplexed Interface Circuit Protection Against Type-C Pin Shorting
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Solution Overview
Problem
In mobile device interfaces, such as the Type-c interface, a pin with a multiplexing function can be short-circuited from a power input pin during charging, leading to burnout of the switch chip and affecting normal interface usage.
Innovation Solution
The interface circuit includes a switching unit with isolation resistors and an on-off apparatus, which disconnects the switching unit from the power input when a short circuit occurs, preventing burnout and ensuring normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the interface uses multiplexing function pins adjacent to power input pins, then the interface can be used for both charging and audio functions, but the multiplexing pins may be short-circuited from power pins causing switch chip burnout
Solution Approach 1:
The patent introduces isolation resistors as intermediary components between the power input pin and the switch chip, and between the multiplexing pins and the switch chip. These resistors act as mediators that allow normal signal transmission while blocking harmful high-voltage short circuits from reaching the switch chip, thus protecting the switch chip from burnout while maintaining interface multiplexing functionality
Solution Approach 2:
The patent implements protection mechanisms in advance by connecting isolation resistors before the short circuit can occur. The resistors are pre-configured in the circuit path to limit current flow and absorb voltage spikes, providing beforehand cushioning against potential short circuit damage to the switch chip during charging operations
2Reliability
If isolation resistors are added to protect the switching unit, then the switching unit is protected from burnout, but the circuit complexity increases
Solution Approach 1:
The patent applies isolation resistors only at specific critical locations where short circuit protection is needed - specifically between the power input pin and the switching unit, and between the multiplexing pins and the switching unit. This localized application of protection components provides effective protection while minimizing the overall increase in circuit complexity by not adding resistors to every circuit path
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents the switching unit from burning down during short circuits, ensuring the normal use of the interface by limiting the current through the switch chip to below burnout levels.
Implementation Method 1
Because the first resistor, the second resistor, the third resistor, and the fourth resistor are respectively connected in series as isolation resistors on their respective paths, a current flowing through the Vcc end, the GND end, the first control end and the second control end, and the first input end and the third input end is smaller than a burnout current of the switching unit
Data Source
AI summary
This disclosure provides example interface circuits, interface circuit protection methods, and terminal devices. An example interface circuit includes a switching unit, a power input end, a first function pin, a second function pin, a control signal input end, a detection port, a grounding output end, a first resistor, a second resistor, a third resistor, a fourth resistor, and an on-off apparatus. The switching unit includes a wire grounding GND end, a circuit power supply Vcc end, a first switch circuit, and a second switch circuit. The on-off apparatus includes an input pin, a first on-off pin, and a second on-off pin. The switching unit is configured to switch, in response to a control signal that is input through the control signal input end, functions corresponding to the first function pin and the second function pin.