Bus Interface Unpowered Termination for Power Delivery
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Solution Overview
Problem
Existing bus interface protocols, such as USB, face challenges in accurately communicating current sourcing capabilities between devices over wired connections, particularly when the power-consuming device's internal voltage is unstable or absent, leading to inconsistencies in power delivery and charging capabilities.
Innovation Solution
A system utilizing a power supply circuit and dual pull-down circuits, where a first unpowered pull-down circuit uses a resistive element to communicate power capabilities without local power, and a second actively trimmed pull-down circuit takes over once stable power is available, using enhanced-mode MOS transistors to enable precise resistance control, allowing for tiered indications of current sourcing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pull-down circuit is used, then the device complexity is reduced, but the measurement precision of current sourcing capabilities deteriorates when power is unstable or absent
Solution Approach 1:
The pull-down circuit is segmented into two distinct circuits: a first pull-down circuit that operates without local power using a resistive element, and a second pull-down circuit that operates with stable power using an actively trimmed resistive element. This segmentation allows each circuit to be optimized for its specific operating condition, resolving the contradiction between simplicity and precision.
Solution Approach 2:
The system dynamically switches between the first and second pull-down circuits based on the availability of stable local power. A control circuit enables or disables each circuit according to power conditions, allowing the system to adapt its precision level to the current operating state while maintaining overall functionality.
2Measurement precision
If an actively trimmed resistive element is used, then the measurement precision of power capabilities is improved, but the device complexity increases due to additional power management requirements
Solution Approach 1:
The first pull-down circuit is designed to operate in advance before stable local power is available. This preliminary operation allows the device to communicate its current sourcing capabilities immediately upon connection, without waiting for power stabilization, thereby achieving high precision measurement without requiring complex power management for the measurement function itself.
Solution Approach 2:
The resistive element in the first pull-down circuit serves as an intermediary that enables power capability communication without requiring active power management. By using a passive resistive element that operates independently of local power, the system achieves precise measurement while avoiding the complexity of power management circuits for this specific function.
3Measurement precision
If power communication waits for stable internal voltage, then the measurement precision is improved, but the loss of time in power delivery increases
Solution Approach 1:
The first pull-down circuit performs preliminary power capability communication immediately upon connection, before the local power supply stabilizes. This preliminary action eliminates the time delay that would otherwise be required to wait for stable voltage, while still achieving accurate communication of current sourcing capabilities through the passive resistive element.
Solution Approach 2:
The system maintains continuous power capability communication by switching from the first pull-down circuit (operating without stable power) to the second pull-down circuit (operating with stable power). This continuity ensures that power delivery establishment occurs without interruption or time loss, while maintaining measurement precision throughout the transition.
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 accurate and efficient communication of power-related capabilities between devices, ensuring stable power delivery and meeting USB Type-C specifications for extended power delivery up to 100W, even when local power is not available, by using actively trimmed resistive values and unpowered pull-down circuits.
Implementation Method 1
A first resistive element can be configured to provide a pull-down for a particular wire of the wired connection
Implementation Method 2
A second resistive element can be configured to provide a pull-down for the particular wire that is actively trimmed
Implementation Method 3
A second pull-down circuit can be configured to include at least one transistor that, in the absence of the operating power, is configured to enable a current path, in response to a gate voltage generated from a voltage on the particular wire
Data Source
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AI summary
A system including a device that is configured to communicate current sourcing capabilities to an external power source over a wired connection containing a plurality of wires. The device includes a power supply circuit configured to provide operating power for the device. A first pull-down circuit is configured to provide a pull-down for a particular wire of the wired connection using a first resistive element that is actively trimmed using the operating power. A second pull-down circuit includes at least one transistor that, in the absence of the operating power, is configured to enable a current path, in response to a gate voltage generated from a voltage on the particular wire, between the particular wire and a second resistive element.