Zero-Tempco Current Source Circuit Without External Precision 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 influence 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 board 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 integration eliminates the need for external high-precision resistors while maintaining current precision through temperature compensation mechanisms within the chip.
Solution Approach 2:
The patent introduces a zero temperature coefficient resistor circuit as an intermediary between the power supply and the current output stage. This circuit acts as a mediator that compensates for temperature variations and process deviations, providing stable reference current without requiring external high-precision components.
2Measurement precision
If an external high-precision resistor is used to achieve high-precision reference current, then the current precision is improved, but the chip pin count increases
Solution Approach 1:
The patent combines multiple functional elements (temperature compensation, reference voltage generation, and current regulation) into a single integrated zero temperature coefficient resistor circuit within the chip. This reduces the need for external components and decreases the chip pin count while maintaining high current precision.
Solution Approach 2:
The zero temperature coefficient resistor circuit serves multiple functions simultaneously: it provides temperature compensation, generates reference voltage, and regulates current output. This multi-functionality eliminates the need for separate external high-precision resistors and reduces the overall device complexity.
3Measurement 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 integrates the temperature compensation function directly into the chip's resistor network, eliminating the need for expensive external high-precision resistors. This integration reduces component count and assembly complexity, thereby lowering manufacturing costs while maintaining current precision.
Solution Approach 2:
The zero temperature coefficient resistor circuit is self-compensating, automatically adjusting for temperature variations and process deviations without requiring external calibration or adjustment components. This self-service capability eliminates the need for expensive external high-precision resistors and reduces manufacturing complexity.
4Device complexity
If traditional current source circuit is used, then the circuit structure is simple, but the output current drifts with temperature changes
Solution Approach 1:
The patent uses a composite resistor network consisting of multiple resistors with different temperature coefficients (R1 with positive temperature coefficient, R2 and R4 with negative temperature coefficients, R3 as reference). This composite structure compensates for temperature variations through the interaction of different thermal characteristics, maintaining current stability without significantly increasing circuit complexity.
Solution Approach 2:
The patent changes the resistance parameters of multiple resistors to achieve temperature compensation. By carefully selecting resistance values and temperature coefficients for R1, R2, R3, and R4, the circuit maintains a stable output current across temperature variations while keeping the overall structure relatively simple.
Data Source
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AI summary
The present disclosure discloses 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.