Zener Voltage Reference Circuit With CTAT Temperature Compensation
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Solution Overview
Problem
Conventional voltage reference circuits based on Zener diodes face challenges in maintaining long-term stability and low drift, particularly in applications like battery management systems, due to the positive temperature coefficient of Zener diodes, which requires effective temperature compensation.
Innovation Solution
A voltage reference circuit incorporating a CTAT circuit with two bipolar transistors arranged to carry identical currents, connected in a series configuration with a Zener diode, and utilizing additional current sources and a FET to ensure precise current matching, allowing for lower supply voltage operation and improved temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a Zener diode is used as the basis for a reference voltage circuit, then the reference voltage stability over time is improved, but the positive temperature coefficient of the Zener diode causes temperature drift that must be compensated
Solution Approach 1:
The patent converts the harmful positive temperature coefficient of the Zener diode into a useful feature by combining it with a CTAT circuit. The PTAT characteristic of the Zener diode voltage when combined with the CTAT component creates a compound voltage that is first-order compensated against temperature variations, transforming the temperature sensitivity from a defect into a compensatable characteristic.
Solution Approach 2:
The patent creates a composite voltage reference circuit by combining the Zener diode with a CTAT circuit comprising bipolar transistors and resistors. This composite structure integrates the long-term stability of the Zener diode with the temperature compensation capability of the CTAT circuit, achieving both durability and temperature insensitivity.
2Temperature
If bipolar transistors are stacked or partially stacked relative to ground voltage for temperature compensation, then temperature compensation is achieved, but the minimum supply voltage requirement increases
Solution Approach 1:
The patent inverts the conventional stacking approach by connecting the emitters of the bipolar transistors to a common node that is not ground, and connecting the collectors to the supply voltage through current sources. This inverted configuration eliminates the need for stacked transistor arrangements relative to ground, thereby reducing the minimum supply voltage requirement while maintaining temperature compensation functionality.
3Duration of action of stationary object
If conventional voltage reference circuits are used, then long-term drift is reduced, but the temperature coefficient requires additional compensation circuits that increase complexity
Solution Approach 1:
The patent merges the temperature compensation function directly into the voltage reference circuit by integrating the CTAT circuit with the Zener diode. The bipolar transistors and resistors are configured to work together with the Zener diode in a unified structure, combining the reference voltage generation and temperature compensation functions into a single cohesive circuit rather than separate modules.
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
The solution achieves accurate temperature compensation, reducing the positive temperature coefficient of the Zener diode voltage, enabling a stable reference voltage with low drift and lower minimum supply voltage requirements, suitable for long-term applications.
Implementation Method 1
the base of the first bipolar transistor is connected to the first node and the base of the second bipolar transistor is connected to a centre node of a first voltage divider... their base emitter voltages may thereby be accurately matched, which may improve the accuracy of the cancellation of the positive temperature coefficient of the Zener diode voltage
Implementation Method 2
The voltage across Zener a diode varies only slowly with the current through the diode, and thus the diode can form the basis of an accurate reference voltage
Data Source
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AI summary
A voltage reference circuit is disclosed comprising: a supply terminal; a ground terminal; a first current source and a Zener diode connected in series between the supply and ground terminals and having a first node therebetween and configured to supply a Zener voltage at the first node; an output node configured to provide a voltage reference; and a CTAT, circuit connected between the first node and the output node; wherein the CTAT circuit comprises: two bipolar transistors, having their respective emitters connected at a second node, and configured to, in operation, have equal collector-emitter currents, the base of the first bipolar transistor being connected to the first node, the base of the second bipolar transistor being connected to a centre node of a first voltage divider; and wherein the first voltage divider is connected between the emitter of the second bipolar transistor and the output node.