Power Receiving Apparatus Short Circuit Detection via Bus Switch Segmentation
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Solution Overview
Problem
Current power supply systems, particularly those conforming to the USB-PD specification, are unable to effectively detect and protect against short circuits that occur on the load side of the bus switch, leading to potential overheating and reliability issues.
Innovation Solution
Incorporating a short circuit detection circuit within the power receiving apparatus that operates before the bus switch is turned on, allowing for safe detection of short circuits without affecting the power supply circuit, and utilizing a charger circuit with high impedance and a charging resistor to limit current flow during a short circuit, along with a comparator to detect voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short circuit detection circuit is added to detect short circuits on the load side of the bus switch, then the reliability and safety of the power supply system is improved, but the device complexity increases
Solution Approach 1:
The bus line is divided into two segments: a first bus line between the receptacle and the bus switch, and a second bus line between the bus switch and the load circuit. The short circuit detection circuit specifically monitors the second bus line segment, allowing targeted detection without requiring complete system redesign. This segmentation enables reliable short circuit detection while maintaining manageable circuit complexity.
Solution Approach 2:
The bus switch serves as an intermediary element that the short circuit detection circuit monitors to detect short circuits on the load side. By detecting the state of the bus switch and the voltage on the second bus line, the system can identify short circuits without directly interfacing with the load circuit, thus improving reliability while keeping the detection mechanism relatively simple.
2Productivity
If the bus switch is turned on to supply power to the load circuit, then the productivity and power delivery capability is improved, but the risk of overheating and damage from short circuits increases
Solution Approach 1:
The short circuit detection circuit performs detection before the bus switch is turned on. By checking for short circuits on the second bus line in advance (when the bus switch is in the off state), the system prevents potential short circuit damage before it can occur. This preliminary detection action enables safe power delivery while eliminating the harmful effect of short circuits.
Solution Approach 2:
The system uses the off state of the bus switch (when no power is being delivered) as an opportunity to perform safety detection. The detection circuit utilizes the zero-voltage condition during the off state to safely detect short circuits without affecting normal power delivery operations. This converts a potentially harmful condition (short circuit) into a detectable state that can be identified and prevented.
3Reliability
If a charger circuit with high impedance and charging resistor is used to limit current flow during short circuit, then the reliability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The charger circuit is designed with high impedance characteristics and includes a charging resistor to limit current flow during short circuit conditions. By changing the impedance parameter of the charger circuit, the system naturally limits harmful current without requiring complex active protection circuits. This parameter-based approach improves reliability while maintaining ease of manufacture, as it uses passive circuit elements rather than complex active protection mechanisms.
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
Enables safe detection and protection against short circuits on the load side, preventing overheating and maintaining system reliability by disconnecting the short-circuit portion and limiting current flow, thus ensuring the power supply system remains in a safe state.
Implementation Method 1
In the off state of the bus switch, the short circuit detection circuit detects a short circuit of the bus line that is more toward the load circuit side than the bus switch. When there is no short circuit of the bus line, a charger circuit raises, from an initial value of zero, a voltage on the bus line by charging the bus line
Implementation Method 2
When the voltage on the bus line does not reach a predetermined voltage, it is determined that there is a short circuit of the bus line
Data Source
AI summary
A power receiving apparatus receives a bus voltage from a power supply apparatus via a cable, and supplies the bus voltage to a load circuit. A power receiver side controller receives, as a power supply, a voltage VADP of a bus line that is more toward a bus switch. The power receiver side controller is capable of communicating with a power supply side controller of the power supply apparatus. Furthermore, the power receiver side controller determines the voltage to be supplied based on a negotiation, and controls the bus switch. A short circuit detection circuit detects a short circuit of a bus line that is more toward the load circuit side than the bus switch.