USB Power Supply Voltage Drop Compensation
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Solution Overview
Problem
USB power supply apparatuses face significant voltage drop issues due to high on-resistance MOSFETs and impedance in the power supply path, making it difficult to meet the USB-PD specification's higher current and voltage requirements.
Innovation Solution
A USB power supply apparatus with a selector that chooses between the output voltage and bus voltage closer to the USB power receiving apparatus, a feedback circuit to control the power supply circuit, and a controller that manages the switch and selector based on the supply current and state, reducing voltage drop and maintaining the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a MOSFET with higher on-resistance is used in the power supply path, then device cost is reduced, but voltage drop increases making it difficult to meet USB-PD specification requirements
Solution Approach 1:
The feedback circuit performs preliminary voltage detection and adjustment before the voltage reaches the output terminal. By detecting the output voltage and comparing it with a reference voltage, the feedback circuit proactively adjusts the power supply circuit to compensate for voltage drop, ensuring the voltage meets specification requirements before delivery.
Solution Approach 2:
A feedback circuit is introduced that continuously monitors the output voltage and feeds this information back to the power supply circuit. The feedback circuit compares the detected output voltage with a reference voltage and adjusts the power supply accordingly, creating a closed-loop control system that automatically compensates for voltage drop caused by MOSFET on-resistance.
2Speed
If the switch is turned on immediately to supply power, then power delivery speed is improved, but voltage instability occurs due to inrush current and impedance
Solution Approach 1:
The feedback circuit continuously monitors the output voltage and provides real-time feedback to the power supply circuit. This closed-loop control ensures that voltage instability caused by inrush current is quickly detected and corrected, maintaining voltage stability during the power delivery process.
Solution Approach 2:
The feedback circuit performs preliminary voltage detection and adjustment before full power delivery begins. By preparing the voltage regulation system in advance and making preliminary adjustments, the system avoids voltage instability when the switch is turned on, enabling both fast power delivery and stable voltage.
Data Source
AI summary
A USB power supply apparatus conforms to the USB (Universal Serial Bus) specification, and supplies electric power to a USB power receiving apparatus. A bus line connects the output of a power supply circuit and the USB power receiving apparatus. A switch is provided on a path of the bus line. A selector selects one from among the output voltage VOUT of the power supply circuit and the bus voltage VBUS at a position that is closer to the USB power receiving apparatus side than the switch. A feedback circuit feedback controls the power supply circuit such that the voltage VS selected by the selector approaches a setting voltage VSET. A controller controls the switch and the selector based on the state of the USB power supply apparatus.