USB Power Control Circuit with Adaptive Feedback and Segmented Switching
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Solution Overview
Problem
The existing power control systems for USB devices are inefficient and costly, particularly when a device operates as both a host and a peripheral, leading to voltage instability and unreliable operations due to significant voltage drops and overshoots across switches, which are exacerbated by the need for large switches to minimize resistance and maintain suitable voltage levels.
Innovation Solution
The implementation of a USB power control circuit with adaptive feedback and charging functions, utilizing multiple switches and a charge circuit to regulate voltage efficiently, allowing the internal device regulator to provide power to both internal and external USB transceivers while minimizing voltage drops and ensuring stable load regulation, by selectively coupling power sources and using a comparator to manage switching states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If large switches are used to minimize resistance and maintain suitable voltage levels, then voltage stability is improved, but device complexity and cost increase
Solution Approach 1:
The power delivery path is segmented into multiple stages with smaller switches operating at different voltage levels. The first switch operates at full voltage to charge the capacitor, while the second switch operates at reduced voltage to supply the USB transceiver, allowing smaller switch sizes while maintaining stability
Solution Approach 2:
A capacitor is introduced as an intermediary energy storage element between the power source and the USB transceiver. This capacitor acts as a buffer that decouples the large current transient requirements from the USB transceiver power supply, enabling the use of smaller switches
2Use of energy by moving object
If the internal device regulator provides power to both internal and external USB transceivers, then power efficiency is improved, but voltage drops and overshoots increase causing instability
Solution Approach 1:
The capacitor is charged in advance to the appropriate voltage level before the USB transceiver is activated. This preliminary charging action prepares the energy buffer so that when the transceiver turns on, the pre-charged capacitor can immediately supply current without causing significant voltage drops or overshoots
Solution Approach 2:
The power delivery function is segmented into two distinct switching stages: a first switch for charging the capacitor from the regulator, and a second switch for delivering power from the capacitor to the USB transceiver. This segmentation allows independent optimization of each stage and prevents the instability caused by direct connection
3Adaptability or versatility
If additional regulators are added to provide power to internal USB transceiver and external devices, then power delivery capability is improved, but device complexity and cost increase
Solution Approach 1:
The internal device regulator is made multi-functional by enabling it to power both the internal USB transceiver and external USB devices through the capacitor buffer and dual-switch arrangement. This eliminates the need for separate dedicated regulators while maintaining the ability to independently power different USB interfaces
Solution Approach 2:
The capacitor serves as a universal intermediary energy buffer that enables a single regulator to serve multiple USB power delivery functions. By mediating between the regulator and multiple potential loads (internal transceiver, external devices), the capacitor allows one regulator to effectively perform the work of multiple regulators
Data Source
AI summary
A universal serial bus power control circuit including at least one first switch which selectively couples a power source node to an external power node, a comparator which detects when the external power node is charged, a feedback node for enabling voltage regulation, a charge circuit and a controller. The charge circuit charges the external power node from the power source node and selectively couples the feedback node to at least one of the power source node and the external power node. The controller opens the first switch when the external power node is not charged, controls the charge circuit to charge the external power node while coupling the feedback node to the power source node, and closes the first switch and couples the feedback node to the external power node in a host mode when the external power node is charged.