Load Driving Device Overcurrent Detection Using Transistor Source-Drain Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing load driving devices face challenges in detecting overcurrent with simple and small-scale construction, especially when dealing with high voltages, as they often require resistors or complex circuits, and suffer from increased chip costs or circuit complexity.
Innovation Solution
A load driving device with a controller, a dividing circuit, a voltage generating circuit, and a comparator that uses MOS transistors to generate divided voltages and reference voltages for overcurrent detection, eliminating the need for detection resistors and allowing operation in high voltage environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detection resistance or wire resistance is used for over current detection, then over current can be detected, but chip cost increases
Solution Approach 1:
The output transistor itself serves the dual function of current amplification and over-current detection. The source-drain voltage of the output transistor is directly utilized as the detection signal, eliminating the need for separate detection resistors or wire resistance components, thereby reducing chip cost while maintaining detection capability
Solution Approach 2:
The output transistor is made multi-functional by using its inherent source-drain voltage characteristic for both its primary switching function and over-current detection function. This eliminates dedicated detection components and reduces overall circuit complexity and cost
2Measurement precision
If a comparator with reference voltage generation is used for over current detection, then detection accuracy is improved, but circuit complexity increases
Solution Approach 1:
The controller continuously monitors the source-drain voltage of the output transistor and adjusts the gate voltage accordingly. When over-current is detected (source-drain voltage exceeds threshold), the controller reduces gate voltage to limit current, creating a closed-loop feedback system that ensures accurate over-current protection without complex additional circuitry
Solution Approach 2:
The output transistor's own source-drain voltage serves as both the operating parameter and the detection signal. This self-providing detection signal eliminates the need for external detection resistors, complex voltage dividers, or separate reference voltage generation circuits, thereby simplifying the overall circuit construction while maintaining detection accuracy
3Reliability
If resistors or capacitors are used to construct detection circuits, then over current can be detected, but circuit scale increases
Solution Approach 1:
The output transistor provides its own detection signal through its source-drain voltage, eliminating the need for external detection resistors, capacitors, or other passive components. This self-sufficient approach significantly reduces the circuit scale while maintaining reliable over-current protection functionality
Solution Approach 2:
The detection function is extracted from the output transistor's source-drain voltage characteristic rather than requiring separate detection components. By taking out and utilizing the inherently available voltage signal, the circuit scale is reduced while preserving detection capability
Data Source
AI summary
The load driving device disclosed in the specification includes a controller to generate a first control signal based on an input signal, a first output transistor to supply an output current to a load according to the first control signal, a first dividing circuit to output a first divided voltage by dividing a voltage across a first primary electrode and a second primary electrode of the first output transistor by a first transistor and a second transistor connected in serial, a first voltage generating circuit to output a first reference voltage, and a first comparator to supply a first over current detection signal to the controller based on the first reference voltage and the first divided voltage.