Overcurrent Detection Circuit Using Differential Reference Voltage
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Solution Overview
Problem
Existing overcurrent detection circuits in power convertors, especially when integrated into high-side driver circuits, face challenges in accurately detecting overcurrent due to displacement currents and voltage fluctuations, which can cause malfunctions and instability, particularly affecting the bipolar transistor-based reference voltage generation.
Innovation Solution
An overcurrent detection circuit with a simple configuration using a current detection resistor, a reference voltage generation circuit comprising resistors with different and same temperature characteristics, and an instrumentation amplifier to generate a stable reference voltage, eliminating the need for a bipolar transistor and ensuring accurate overcurrent detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bipolar transistor is used in the reference voltage generation circuit to provide temperature compensation, then the overcurrent detection accuracy is improved, but the circuit stability deteriorates due to displacement current and voltage fluctuations in high-side driver applications
Solution Approach 1:
The invention extracts and removes the bipolar transistor from the reference voltage generation circuit, replacing it with a resistor-based voltage division circuit. This extraction eliminates the source of displacement current and voltage fluctuations while maintaining the temperature compensation function through careful selection of resistors with appropriate temperature coefficients.
Solution Approach 2:
The invention creates a simplified copy of the temperature compensation function using resistors instead of a bipolar transistor. The resistor-based voltage division circuit replicates the temperature characteristic matching capability of the bipolar transistor but without the harmful side effects of displacement current and voltage fluctuation.
2Measurement precision
If a bipolar transistor is used for temperature compensation in the reference voltage circuit, then the temperature characteristic matching is improved, but the circuit complexity increases due to additional components and configuration requirements
Solution Approach 1:
The invention replaces the complex bipolar transistor configuration with a simple resistor-based voltage division circuit that copies the essential temperature compensation function. This reduces circuit complexity while maintaining temperature characteristic matching through proper selection of resistors with appropriate temperature coefficients.
Solution Approach 2:
The invention substitutes the bipolar transistor with simple resistors that are cheaper, more reliable, and require no complex biasing or configuration. The resistor-based solution is more robust and easier to integrate into standard CMOS or bipolar processes without requiring special device structures.
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
This configuration allows for stable and accurate detection of overcurrent flowing through switching elements, protecting them from overcurrent without the malfunction risks associated with bipolar transistors, and can be adjusted for various temperature characteristics, enhancing practical application.
Implementation Method 1
a current detection resistor Rs which converts the current supplied from the current input terminal Tin into voltage
Implementation Method 2
a reference voltage generation circuit which generates a reference voltage having a temperature characteristic that is corresponded to the output temperature characteristic of the current detection element, by resistance-dividing a predetermined standard voltage
Data Source
AI summary
An overcurrent detection circuit includes a current detection resistor that generates a voltage in proportion to current flowing through a switching element and a comparator that compares the voltage detected via the current detection resistor and a reference voltage generated by a reference voltage generation circuit to thereby detect overcurrent flowing through the switching element. In particular, the reference voltage generation circuit includes: a first resistance voltage dividing circuit that resistance-divides a standard voltage by connecting, in series, two types of resistors having different temperature characteristics; a second resistance voltage dividing circuit that resistance-divides the standard voltage by connecting, in series, resistors having the same temperature characteristics; and an instrumentation amplifier that generates the reference voltage according to the difference between the divided output voltages of the first and second resistance voltage dividing circuits.