VCONN Soft-Start Control for USB-C Inrush Current
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Solution Overview
Problem
Existing USB Type-C interface technologies lack a digitally controlled soft start scheme to manage inrush current and ramp up output voltage effectively, leading to complex implementations and significant memory requirements.
Innovation Solution
A system and method utilizing a serial shift register with a programmable clock divider, a resistor digital-to-analogue conversion unit, and pass gate switches to incrementally control the input voltage to a VCONN charge pump, allowing the output voltage to be ramped slowly and incrementally, thereby controlling inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a related art charge pump circuit with multiple capacitors and switches is used, then the output voltage can be controlled, but significant memory is required to store multiple control signals
Solution Approach 1:
The patent extracts the control signal storage function from a separate memory component and integrates it into the shift register circuitry. The shift register itself stores the control signals sequentially, eliminating the need for additional memory resources while maintaining precise control over the charge pump switches.
Solution Approach 2:
The patent combines multiple functions into unified circuit blocks: the shift register integrates control signal generation and storage, the charge pump integrates voltage multiplication and regulation, and the feedback loop integrates monitoring and control. This merging reduces overall system complexity and memory requirements.
2Productivity
If output voltage is ramped up quickly, then power delivery is efficient, but inrush current damages the circuit
Solution Approach 1:
The patent implements preliminary action by enabling the charge pump in staged increments before full power delivery is needed. The shift register sequentially activates switch pairs, gradually building up the output voltage from zero to the target level, ensuring the circuit is prepared for safe operation before full power is applied.
Solution Approach 2:
The patent uses periodic clock signals to control the sequential activation of switch pairs in the charge pump. Each clock cycle advances the shift register, which in turn activates the next pair of switches, creating a periodic, controlled ramping sequence that prevents inrush current while maintaining efficient power delivery.
3Measurement precision
If feedback loop is incorporated to monitor charge pump output, then voltage control is improved, but implementation complexity increases significantly
Solution Approach 1:
The patent merges the feedback monitoring function with the existing charge pump control circuitry. The feedback path uses the same control signals and switch states to monitor output voltage, integrating the monitoring function into the control logic rather than adding separate complex monitoring hardware.
Solution Approach 2:
The control circuitry serves multiple functions: it generates control signals for the charge pump switches, stores these signals in the shift register, and simultaneously uses these same signals for feedback monitoring. This multi-functionality reduces overall system complexity while maintaining precise voltage control.
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 a digitally controlled soft start scheme that effectively manages inrush current by incrementally ramping up the output voltage, reducing complexity and memory requirements while ensuring safe and efficient power delivery in USB Type-C interfaces.
Implementation Method 1
a resistor digital to analogue conversion (DAC) unit that can be operatively coupled to the serial shift register and can be configured to, upon controlling by the serial shift register, increment voltage in a step wise manner
Implementation Method 2
a VCONN charge pump, and configured to control an input voltage to a VCONN charge pump, said input voltage being in incremental steps such that the VCONN charge pump pumps an output voltage, corresponding to the input voltage
Data Source
AI summary
The present disclosure provides a system and method for soft start scheme to control inrush current for VCONN in USB-C interface. The system includes: a serial shift register having flip-flops and adapted to obtain clock with programmable clock divider, frequency of clock changes dynamically by programming programmable clock divider; a resistor DAC unit configured to increment voltage in step-wise manner; a pass gate switch comprising NMOS gate switch and a PMOS gate switch connected in parallel and operatively coupled to the resistor DAC unit and configured to control an input voltage to a VCONN charge pump, said input voltage being in incremental steps such that the VCONN charge pump pumps an output voltage; and a VCONN switch gate operatively coupled to the VCONN charge pump and configured to supply the output voltage in controlled, incremental steps, such that the output voltage is ramped slowly to control the inrush current.