Power Switching Circuit Reverse Overcurrent Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power switching circuits fail to adequately protect diodes connected in parallel with switching elements from overcurrents, leading to potential diode deterioration and breakdown, especially when using synchronous rectification systems without a free-wheel diode.
Innovation Solution
A power switching circuit comprising a main switching element, a sense switching element, a reverse overcurrent detection circuit, and a control circuit that turns on both elements when a reverse overcurrent is detected, distributing the current through both the main and sense body diodes to mitigate overcurrent stress on the diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all switching elements are turned off when overcurrent occurs, then the main current is interrupted, but the overcurrent flows only through diodes connected in parallel to the switching elements, which deteriorates the diodes
Solution Approach 1:
The invention divides the diode into two separate diodes: a main body diode connected in parallel with the main switching element, and a sense body diode connected in parallel with the sense switching element. This segmentation allows the overcurrent to be distributed between the two diodes, reducing the current burden on each individual diode and preventing deterioration.
2Loss of energy
If synchronous rectification system eliminates free-wheel diode, then voltage drop is minimized, but overcurrent flows through body diode with low overcurrent capacity, leading to deterioration or breakdown
Solution Approach 1:
The invention segments the single body diode function into two separate body diodes (main body diode and sense body diode), enabling the overcurrent to be shared between them. This segmentation maintains the synchronous rectification benefit of minimized voltage drop while providing adequate overcurrent handling capacity through the combined capability of both diodes.
3Reliability
If overcurrent is detected by current through sense transistor, then main current is interrupted, but with inductive load the overcurrent flows through diode after interruption
Solution Approach 1:
The invention performs preliminary action by having the sense switching element remain connected to its body diode, which remains capable of conducting current. When overcurrent occurs and the main switching element is turned off, the sense body diode is already in position to immediately conduct the inductive load current, preventing the delay that would otherwise cause overcurrent through the main diode.
Data Source
AI summary
A power switching circuit includes a power semiconductor element that includes a main switching element connected in parallel with a main body diode and a sense switching element connected in parallel with a sense body diode; a reverse overcurrent detection circuit that detects an overcurrent flowing in the reverse direction out of currents flowing through a parallel-connection body of the sense switching element and the sense body diode; and a control circuit that drives the gate of the power semiconductor element; wherein when the reverse overcurrent detection circuit detects a reverse overcurrent, the control circuit controls the main switching element and the sense switching element to turn on.