USB ID Contact Isolation Circuit for Water Electrolysis Prevention
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Solution Overview
Problem
Water exposure can damage the ID contact of a USB interface in mobile devices, leading to poor contact with OTG devices due to electrolysis, as existing designs lack effective protection against water without compromising the ability to detect connected OTG devices.
Innovation Solution
A USB interface circuit with an isolation circuit between the power supply and the ID contact, which maintains the voltage below the electrolytic voltage threshold of water when no OTG device is connected, preventing electrolysis and ensuring the ID contact remains functional while allowing detection of connected OTG devices by switching to a saturated state when a device is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the ID contact is exposed to enable OTG device connection, then the ease of operation is improved, but the reliability deteriorates due to water damage risk
Solution Approach 1:
The patent changes the voltage parameter of the ID contact from a high level (1.8V or higher) to a low level (below electrolytic voltage threshold of water). This parameter change prevents water electrolysis and corrosion while maintaining the electrical interface functionality for OTG device detection and connection.
2Ease of operation
If the ID contact voltage is maintained at high level for normal operation, then the ease of operation is improved, but the object-affected harmful factors worsen due to water electrolysis
Solution Approach 1:
The patent applies preliminary anti-action by pre-establishing a low voltage state on the ID contact before water exposure can cause damage. The isolation circuit is configured to maintain the ID contact voltage below the electrolytic voltage threshold of water, preventing water electrolysis and corrosion in advance.
Solution Approach 2:
The patent introduces an isolation circuit as an intermediary component between the power supply circuit and the ID contact. This intermediary circuit controls the voltage level on the ID contact, blocking harmful high voltage from reaching the interface while allowing normal low-voltage OTG detection operations.
3Reliability
If an isolation circuit is added to protect from water damage, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The isolation circuit performs multiple functions simultaneously: it limits the voltage on the ID contact to prevent water electrolysis, enables OTG device detection through voltage level changes, and protects the power supply circuit from external influences. This multi-functionality reduces the need for separate protection circuits.
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
Prevents damage to the ID contact from water exposure while enabling normal connection and detection of OTG devices, ensuring reliable operation in waterproof mobile devices.
Implementation Method 1
The isolation circuit is configured to control a voltage at the ID contact below a preset voltage upon detecting an OTG device is not connected with the USB interface, wherein the preset voltage is an electrolytic voltage threshold of water
Data Source
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Figure 3
AI summary
A USB interface circuit includes a power supply circuit having an output, a USB interface having an ID contact, a trigger detection circuit having an input, and an isolation circuit located between the power supply circuit and the ID contact and having a first end and a second end. The first end of the isolation circuit and the output of the power supply circuit are connected with the input of the trigger detection circuit. The second end of the isolation circuit is connected with the ID contact. The isolation circuit is configured to control a voltage at the ID contact below a preset voltage upon detecting that an On-The-Go (OTG) device is not connected with the USB interface. Other example USB interface circuits and mobile devices including USB interface circuit are also disclosed.