Programmable VBUS Discharge in USB Power Delivery ICs
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Solution Overview
Problem
Existing USB-PD systems face challenges in quickly discharging voltage from a USB VBUS line without causing heating and latch-up, particularly when high currents are involved, and often require external components that increase costs and do not provide adequate protection against live supply discharge.
Innovation Solution
An integrated circuit (IC) controller with multiple independently-controlled on-die discharge circuits that can discharge voltage from a USB VBUS line to programmable levels, reducing the risk of heating and protecting against high currents without external components, by driving current to a USB ground line during events like VBUS swap or fault conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voltage is discharged quickly from VBUS line, then discharge speed is improved, but heating and latch-up risk increases
Solution Approach 1:
The patent implements dynamic discharge control by adjusting the drive strength of discharge circuits based on real-time voltage levels and conditions. The system transitions from static to dynamic operation, modifying discharge parameters during the process to maintain safety while achieving fast discharge. This is evident in the programmable drive strength scheduling that adapts discharge characteristics during operation.
Solution Approach 2:
The system changes physical parameters during discharge operation, specifically adjusting voltage thresholds and current limits dynamically. By modifying these parameters based on operating conditions, the system achieves fast discharge while preventing harmful heating and latch-up effects. The programmable voltage thresholds allow optimization of discharge characteristics for different scenarios.
2Power
If external components are used for voltage discharge, then discharge capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the discharge circuit functionality directly into the USB-PD controller IC, eliminating the need for separate external discharge components. This integration combines multiple functions (power delivery control, voltage regulation, and voltage discharge) into a single device, reducing component count while maintaining full discharge capability. The on-die discharge circuits are controlled through the existing controller architecture.
Solution Approach 2:
The USB-PD controller is designed to perform multiple functions including power negotiation, power delivery control, and voltage discharge. This multi-functional approach eliminates the need for dedicated external discharge components, as the controller itself provides comprehensive power management capabilities. The same control logic manages both power delivery and discharge operations.
3Productivity
If high current is used for voltage discharge, then discharge efficiency is improved, but risk of latch-up and heating increases
Solution Approach 1:
The system implements feedback control by continuously monitoring voltage levels during discharge and adjusting discharge current accordingly. This closed-loop control ensures high discharge efficiency while preventing excessive current that could cause latch-up or heating. The controller responds to voltage threshold crossings by modulating discharge drive strength, maintaining optimal operating conditions.
Solution Approach 2:
The patent applies partial action by using multiple discharge circuits with programmable drive strengths rather than a single high-current circuit. This allows the system to apply just enough current to achieve efficient discharge without excessive current that would cause heating or latch-up. The ability to select different drive strength levels enables optimization between speed and safety.
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
Enables efficient and protected voltage discharge on the VBUS line to any desired non-zero voltage level, reducing heating risks and eliminating the need for external components, thus improving power delivery and reducing costs.
Implementation Method 1
by driving current to a USB ground line during events like VBUS swap or fault conditions
Data Source
AI summary
Techniques for voltage discharge from a USB Power Delivery (USB-PD) VBUS line are described herein. In an example embodiment, an integrated circuit comprises a discharge control logic coupled to a first discharge circuit and to a second discharge circuit. The first discharge circuit configured to couple to a power source node on the VBUS line. The second discharge circuit configured to couple to an output node on the VBUS line. The discharge control logic is configured to independently control the first discharge circuit and the second discharge circuit to discharge the voltage on the VBUS line.