Overcurrent Protection IC With Matched Resistors for Temperature Drift
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Solution Overview
Problem
Existing integrated circuit devices face challenges in maintaining consistent resistance values of current detection resistors due to temperature changes, which are exacerbated by manufacturing errors, affecting the accuracy of overcurrent protection.
Innovation Solution
The overcurrent protection integrated circuit employs first and second resistors made of the same metal material, positioned to minimize manufacturing errors, and uses a differential amplifier to maintain equal voltage across these resistors, with a current mirror circuit to adjust current ratios, and an overcurrent protection comparator to detect voltage deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection resistor is used in the integrated circuit device, then the current detection function is achieved, but the resistance value changes with temperature rise, affecting measurement precision
Solution Approach 1:
The patent creates a virtual copy of the temperature effect by using a dummy resistor that experiences the same temperature changes as the current detection resistor. The dummy resistor's voltage change mirrors the temperature-induced resistance change, allowing the circuit to subtract this effect and recover the true current measurement.
Solution Approach 2:
The patent introduces a dummy resistor as an intermediary element that mediates between the temperature effect and the current detection circuit. This dummy resistor serves as a reference that captures temperature variations, enabling the main circuit to compensate for these variations and maintain accurate current measurement.
2Stability of the object's composition
If metal wiring is used to configure current detection part, then temperature characteristics can be matched, but manufacturing errors affect both resistors differently, reducing reliability
Solution Approach 1:
The patent applies homogeneity by using the same metal material for both the current detection resistor and the dummy resistor. This ensures that both resistors have identical temperature coefficients and respond uniformly to temperature changes, enabling accurate temperature compensation while maintaining manufacturing consistency.
3Stability of the object's composition
If resistor values are adjusted to cancel temperature effects, then temperature compensation is achieved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of precisely controlling absolute resistance values, the patent copies the temperature response characteristics from one resistor to another. This approach shifts the requirement from precise absolute value control to matching relative temperature behavior, which is inherently easier to achieve through identical material selection and geometric design.
Solution Approach 2:
The patent changes the design parameter from absolute resistance value to temperature coefficient matching. By focusing on maintaining the same temperature response rather than the same resistance value, the circuit achieves temperature compensation while tolerating normal manufacturing variations in absolute resistance.
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 approach effectively cancels out the effects of temperature changes on resistor values, ensuring accurate overcurrent protection without being affected by manufacturing errors, thereby maintaining reliable operation.
Implementation Method 1
a temperature characteristic of a current detection resistor configured by the metal wiring in the current detection part and a temperature characteristic of a voltage control circuit to match each other to thereby cancel out a variation in a detected current value caused by a change in temperature
Implementation Method 2
there is an issue that a resistance value of the current detection resistor changes with a rise in temperature of the integrated circuit device
Data Source
AI summary
An overcurrent protection integrated circuit includes: a current input including a first resistor receiving an input current; a current sense amplifier circuitry including a differential amplifier, a switching element, a second resistor, and a current mirror circuit; and an overcurrent determiner including a third resistor and an overcurrent protection comparator. The current sense amplifier circuitry controls, through the differential amplifier, a voltage of the second resistor to be equal to a voltage of the first resistor, and sends out, from the switching element toward the current mirror circuit, a current decreased to a predetermined ratio relative to the input current. The overcurrent determiner compares a voltage of the third resistor and a voltage of a direct-current power supply, and outputs a signal when the voltage of the third resistor exceeds the voltage of the direct-current power supply. The first resistor and the second resistor include the same metal material.