Power Switch Circuit with Voltage Equalization for Accurate Over-Current Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power switch circuits experience errors in over-current protection due to voltage inconsistencies between the power switch and sensing switch, leading to misjudgment and incorrect current limiting, resulting in a 10% to 20% error in output current.
Innovation Solution
A power switch circuit design that includes a second switch with a higher breakdown voltage than the first switch, coupled in series between the first switch and the output terminal, and an adjusting circuit that equalizes the source voltage of the sensing switch to the drain voltage of the first switch, ensuring accurate sensing and preventing current backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current replication circuit or sensing resistor is coupled between the drain of the sensing switch and ground to enable over-current protection, then the over-current protection mechanism can be implemented, but the drain voltages of the power switch and sensing switch become inconsistent, causing a voltage deviation of about 0.2V that leads to misjudgment and 10% to 20% error in current limiting
Solution Approach 1:
The patent introduces a second switch as an intermediary component between the first switch and the output terminal. This second switch acts as a voltage buffer that prevents the drain voltage of the first switch from dropping to 0V when the output voltage approaches 0V, thereby maintaining voltage consistency between the power switch and sensing switch and eliminating the 0.2V deviation that causes misjudgment in over-current protection
Solution Approach 2:
The patent ensures that the source voltage of the sensing switch remains equal to the drain voltage of the first switch by using the second switch to maintain equipotential conditions. This prevents voltage inconsistency and ensures accurate current sensing throughout the operation, including when output voltage is near 0V
2Productivity
If the output voltage drops to close to 0V during over-current protection, then the load consumption continues but the current supply is limited, but the voltage drop causes inconsistency in drain voltages leading to misjudgment by the over-current protection circuit
Solution Approach 1:
The patent applies beforehand cushioning by introducing the second switch with higher breakdown voltage before the voltage inconsistency problem can occur. This second switch provides a voltage buffer that prevents the drain voltage of the first switch from collapsing to 0V when output voltage approaches 0V, thus cushioning against the potential misjudgment and maintaining reliable current sensing throughout the over-current protection process
Data Source
AI summary
A power switch circuit is disclosed. The power switch circuit includes an input terminal, an output terminal, a first switch, a second switch, a sensing switch and an adjusting circuit. The first switch is coupled to the input terminal. The second switch is coupled to the first switch and the output terminal. A first node between the first switch and the second switch has a first node voltage. A breakdown voltage of the second switch is higher than that of the first switch. The sensing switch is coupled to the input terminal and the first switch. The adjusting circuit is coupled to the first node and the sensing switch. A second node between the adjusting circuit and the sensing switch has a second node voltage. The adjusting circuit adjusts the second node voltage according to the first node voltage to make it equal to the first node voltage.