Vconn Switch Current Control for USB Type-C Protection
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Solution Overview
Problem
Existing USB Type-C controllers face issues with inaccurate over-current detection, failure to function at startup, and inability to detect short circuits due to uncorrelated drain nodes and scaled switches, leading to power losses and unreliable protection.
Innovation Solution
A USB Type-C controller with a Vconn switch featuring a current-controlled architecture, including first and second transistors, a replica switch, and a resistance control module, which matches replica current to load current and controls in-rush current to provide reliable over-current and short-circuit protection, especially during startup and short-circuit events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scaled switch is used to detect over-current events, then over-current protection can be provided, but detection accuracy deteriorates due to uncorrelated drain nodes causing large variations in OCP detection threshold
Solution Approach 1:
The patent uses a replica switch that copies the electrical characteristics of the Vconn switch to generate a replica current that accurately reflects the actual current through the Vconn switch. This copying approach eliminates the detection inaccuracies caused by uncorrelated drain nodes in scaled switches, as the replica switch maintains correlated drain nodes with the original switch.
Solution Approach 2:
The patent introduces a current mirror circuit as an intermediary between the Vconn switch and the OCP detection circuitry. The current mirror transfers the current information from the Vconn switch to the detection circuit through a correlated replica current, enabling accurate OCP detection without directly scaling the switch dimensions.
2Reliability
If a scaled switch is used for OCP detection, then protection function is provided, but functionality at startup deteriorates due to dead time equivalent to turn on time of the scaled switch
Solution Approach 1:
The patent configures the replica switch and current mirror circuit to be activated simultaneously with the Vconn switch at startup. The replica current is generated immediately as the Vconn switch turns on, eliminating any dead time and enabling immediate OCP detection and protection functionality from the moment of startup.
3Reliability
If a scaled switch is used for OCP detection, then protection is provided, but short-circuit detection capability deteriorates during the turn on time of the scaled switch
Solution Approach 1:
The replica switch immediately copies the current waveform of the Vconn switch during turn-on, including any short-circuit conditions. This real-time copying enables the OCP circuit to detect short-circuits instantly during the turn-on phase, eliminating the detection gap that exists when using scaled switches with uncorrelated drain nodes.
4Adaptability or versatility
If a scaled switch with independent sinking current is used, then connection management is enabled, but power efficiency deteriorates due to large power losses from high ratio of load current to quiescent current
Solution Approach 1:
The OCP detection circuit is designed to draw its operating current from the replica current generated by the replica switch, rather than requiring an independent high-power sinking current. This self-service approach allows the OCP circuit to adapt to varying load conditions without dissipating excessive power, as its current requirement scales with the actual load current through the Vconn switch.
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 current-controlled architecture ensures accurate detection and prevention of over-current and short-circuit events, maintaining reliable performance and reducing power losses by dynamically controlling the Vconn switch resistance.
Implementation Method 1
a replica current generator including a first input coupled to a drain of the replica switch and a second input coupled to a drain of the first transistor... operable to match a replica current through the replica switch to that supplied through the first and second transistors to the CC terminal
Implementation Method 2
a resistance control module coupled to an output of the replica current generator and including an output coupled to a gate of the second transistor... operable to control resistance of the Vconn switch, thereby controlling an in-rush current to the CC terminal
Data Source
AI summary
A Universal Serial Bus (USB) controller including a Vconn switch having a current controlled architecture, and method for operating the same, are described. In an example embodiment, the Vconn switch includes first and second transistors coupled in series between a Vconn terminal and a communication channel (CC) terminal, a replica switch coupled to the Vconn terminal, a replica current generator coupled to the replica switch, and a resistance control module coupled to the replica current generator. The replica current generator is operable to match a current through the replica switch to the current supplied to the CC terminal through the first and second transistors. The resistance control module is operable to use a digital output of a current inverter to control an in-rush current to the CC terminal.