USB Power Bus Pre-Charging to Block Inrush Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The integration of USB-A and USB-C devices often results in an initial inrush current due to differing voltage potentials, which can damage devices, and existing solutions like adding transistors or voltage bus capacitors are either ineffective or costly.
Innovation Solution
A controller with a state machine and control signal generator is used to manage the connection by pre-charging a system capacitor to reverse bias the parasitic body diode of a blocking transistor, preventing inrush current when a USB-A device is connected to a USB-C device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If USB-A and USB-C devices are integrated with differing voltage potentials, then connection versatility is improved, but inrush current damage risk increases
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor connected to the USB-C bus before connecting a USB-A device. The controller detects the connection state and activates the power supply to charge the capacitor to a threshold voltage in advance, ensuring the parasitic body diode is reverse-biased before inrush current can occur, thereby preventing damage while maintaining connection versatility
Solution Approach 2:
The patent uses a capacitor as an intermediary element between the USB-C power bus and the parasitic body diode. This capacitor serves as a buffer that absorbs voltage differences and prevents direct current surge transmission, acting as a mediator that protects the system while allowing USB-A and USB-C devices with differing voltage potentials to connect safely
2Reliability
If transistors or voltage bus capacitors are added to prevent inrush current, then device protection is improved, but device complexity and cost increase
Solution Approach 1:
The patent achieves multi-functionality by using a single capacitor that simultaneously serves as both a pre-charge element to prevent inrush current and as a voltage bus capacitor for normal USB-C operation. The controller intelligently manages this single component, eliminating the need for separate protection circuits and reducing overall device complexity while maintaining reliable device protection
Solution Approach 2:
The system applies self-service by using the existing USB-C power supply circuitry to charge the protective capacitor itself, rather than requiring an external or separate power source. The controller monitors the capacitor voltage and activates the power supply only when needed, allowing the system to protect itself using its own integrated components without adding external complexity
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
This solution effectively reduces the risk of damage from inrush current by ensuring the parasitic body diode is reverse biased, thereby preventing harmful currents from flowing through it, enhancing the safety and efficiency of USB connections.
Implementation Method 1
charge a capacitor to a threshold voltage
Implementation Method 2
reverse bias the parasitic body diode of a blocking transistor, preventing inrush current
Data Source
AI summary
Methods, apparatus, systems and articles of manufacture are disclosed including a capacitor, located in a universal serial bus schematic. The methods, apparatus, systems and articles of manufacture include a controller, include a controller including a state machine and a control signal generator, wherein the controller is configured to be coupled to a connector and to a power supply, the state machine is configured to determine a state of the connector, and the control signal generator is configured to, in response to an indication of a device not connected to the connector, generate a signal to indicate to the power supply to charge a capacitor to a threshold voltage, and wherein the control signal generator is further configured to generate the signal until a second state.