Short Circuit Detection Circuit Using Digital Inverter
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Solution Overview
Problem
Conventional short circuit protection circuits for power transistors require voltage level shifters, blanking times, and additional reference branch circuits, leading to increased die size, slower detection times, and higher current consumption, making it difficult to meet efficiency standards.
Innovation Solution
A digital short circuit detection circuit using an inverter and digital processing circuit, eliminating the need for voltage level shifters and blanking circuits, which reduces response time and current consumption by implementing cycle-by-cycle fault detection in the same power supply domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional short circuit protection circuits use voltage level shifters and reference branch circuits, then short circuit detection can be achieved, but die size increases and current consumption increases
Solution Approach 1:
The patent extracts and eliminates the voltage level shifter and reference branch circuit from the conventional short circuit protection architecture. By directly comparing the drain voltage of the power transistor to the reference voltage without these intermediate components, the circuit achieves the same protection function with significantly reduced die area.
Solution Approach 2:
The comparator circuit is designed to perform multiple functions: it compares the drain voltage to the reference voltage for short circuit detection, and also handles normal switching operation control. This multi-functionality eliminates the need for separate voltage level shifter circuits, reducing overall circuit complexity and die size.
2Reliability
If conventional short circuit protection circuits use voltage level shifters and blanking times, then false detection can be prevented, but detection time increases
Solution Approach 1:
The circuit performs preliminary action by continuously monitoring the drain voltage through the comparator even during normal operation. The comparator is always ready to detect voltage drops indicating short circuits, eliminating the need for blanking periods where detection is suspended. This continuous monitoring enables immediate detection without time delays.
Solution Approach 2:
Instead of using blanking time to prevent false detection by disabling the comparator during switching transitions, the patent inverts the approach by keeping the comparator active and using clever circuit design to distinguish between normal switching voltage drops and actual short circuit conditions, achieving both false detection prevention and immediate response.
3Reliability
If conventional short circuit protection circuits are implemented, then transistor protection is achieved, but current consumption increases
Solution Approach 1:
The patent employs a minimalist detection circuit architecture that uses simple voltage comparison without expensive or power-hungry components like voltage level shifters. The comparator-based direct comparison approach provides adequate protection functionality with minimal power consumption, effectively using a simpler, less power-intensive solution that suffices for the protection task.
Data Source
AI summary
A method for detecting a short circuit includes driving a transistor in response to a drive signal, forming a drain signal of the transistor, generating an inverted signal in response to the drain signal, generating a detect signal when the inverted signal and a control signal are active, and providing the drive signal in an active logic state when the control signal is active and the detect signal is inactive, and in an inactive logic state otherwise.