Vconn Switch Current-Controlled Circuit for Startup OCP Accuracy
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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 high 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 the load current and controls the Vconn switch resistance to manage inrush currents and detect over-current 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 main switch.
Solution Approach 2:
The patent introduces a current sense resistor as an intermediary element to convert the replica current into a measurable voltage signal. This intermediary approach enables accurate current detection without directly measuring the high current through the Vconn switch, improving both safety and measurement precision.
2Reliability
If a scaled switch is used for over-current detection, then protection function can be implemented, 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 to be turned on simultaneously with or before the Vconn switch through coordinated gate control. This preliminary action ensures that the over-current protection circuit is already functional when the main switch turns on, eliminating the dead time period where protection would be unavailable.
3Reliability
If a scaled switch is used for over-current detection, then protection can be provided, but detection capability deteriorates during short circuit events when the scaled switch is being turned on
Solution Approach 1:
The patent implements a feedback mechanism where the replica current continuously reflects the actual current through the Vconn switch. During short circuit events, this feedback allows the control circuit to immediately detect the abnormal current condition and respond by turning off the Vconn switch, enabling reliable short circuit detection throughout the entire turn-on process.
4Ease of operation
If a sinking current through the scaled switch is used to manage connections, then connection control is achieved, but power efficiency deteriorates due to relatively large power losses from high ratio of load current to quiescent current
Solution Approach 1:
The patent uses the replica switch to copy only the necessary current information needed for protection detection, rather than sinking a large quiescent current through a scaled switch. This copying approach enables connection management and over-current detection while minimizing power consumption, as the replica circuit draws minimal current compared to the main power path.
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 solution provides reliable over-current and short-circuit protection, including at startup, with reduced quiescent current consumption, ensuring safe and efficient power delivery across USB Type-C cables.
Implementation Method 1
The replica current generator is operable to match a replica current through the replica switch to that supplied through the first transistor 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. The resistance control module is 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 controller including a Vconn switch having a current controlled architecture, and method for operating the same are provided. Generally, the Vconn switch includes first and second transistors coupled in series between a Vconn terminal and a communication channel (CC) terminal, a replica switch including a source coupled to the Vconn terminal, 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, and 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. The replica current generator is operable to match a current through the replica switch to that supplied through the first and second transistors to the CC terminal, and the resistance control module is operable to control resistance of the Vconn switch.