Zero-TC Current Source Circuit for Precision Without External Resistors
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Solution Overview
Problem
The use of external high-precision resistors in current source circuits increases the number of pins and area of the PCB board, leading to higher costs and affecting the precision of ignition currents in airbag ignition circuits.
Innovation Solution
A high-precision current source is designed using a reference voltage generation circuit with a zero temperature coefficient resistor circuit, which adjusts bias voltage based on control signals to maintain precision, reducing the need for external high-precision resistors and minimizing the impact of temperature and manufacturing process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external high-precision resistor is used to achieve high-precision reference current, then the current precision is improved, but the number of pins and PCB area increase
Solution Approach 1:
The patent merges the external high-precision resistor function into an internal zero temperature coefficient resistor circuit composed of multiple resistors (R1, R2, R3, R4) with different temperature coefficients. This combination achieves high-precision current reference without requiring external pins or additional PCB area, directly resolving the contradiction between current precision and PCB area.
Solution Approach 2:
The patent uses composite resistor structures with different temperature coefficients (positive and negative TC resistors) to create a zero temperature coefficient resistor circuit. This composite approach achieves high precision current reference internally, eliminating the need for external high-precision resistors and reducing PCB area while maintaining current precision.
2Measurement precision
If an external high-precision resistor is used to achieve high-precision reference current, then the current precision is improved, but the cost increases
Solution Approach 1:
The patent combines multiple standard resistors with different temperature coefficients into a zero temperature coefficient resistor circuit that provides high-precision current reference. This internal integration eliminates the need for expensive external high-precision resistors, reducing manufacturing cost while maintaining current precision.
Solution Approach 2:
The patent replaces expensive external high-precision resistors with internally integrated zero temperature coefficient resistor circuits composed of standard-value resistors. This substitution reduces component cost and simplifies manufacturing without sacrificing current precision.
3Measurement precision
If an external high-precision resistor is used to achieve high-precision reference current, then the current precision is improved, but the number of pins increases
Solution Approach 1:
The patent merges the function of external high-precision resistors into internal zero temperature coefficient resistor circuits, eliminating the need for external connection pins. This integration maintains current precision while reducing device complexity and pin count.
Solution Approach 2:
The patent extracts the high-precision resistance function from external components and implements it internally through zero temperature coefficient resistor circuits. This extraction eliminates external pins and connections while preserving current precision.
Data Source
AI summary
A high-precision current source and an electronic device applied in the field of high-precision circuit design. An inverting input terminal, a non-inverting input terminal and an output terminal of a first operational amplifier are connected to a bias voltage terminal, a first terminal of a zero temperature coefficient resistor circuit and a first terminal of the first transistor, respectively; second and third terminals of the first transistor are connected to a power supply of a chip and a second terminal of the zero temperature coefficient resistor circuit, respectively; third and fourth terminals of the zero temperature coefficient resistor circuit are connected to a signal control terminal and a first terminal of a current generation circuit, respectively, and a second terminal of the current generation circuit is connected to a corresponding external circuit.