Bandgap Reference Circuit Switching for Temperature-Stable Voltage
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Solution Overview
Problem
Conventional band gap reference voltage generating circuits fail to maintain a reference voltage independent of temperature due to resistance deviations in resistors, which affect the correlation between the reference voltage and temperature.
Innovation Solution
A band gap reference voltage generating circuit is designed with a current generating circuit, a current divider circuit, a connection path switching circuit, and a control circuit to periodically switch connection paths and adjust polarities, reducing the impact of resistance deviations on the reference voltage's temperature dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance values of resistors R1A and R1B are made equal through accurate control, then the reference voltage VOUT can be made independent of temperature, but resistance deviation inevitably exists even under accurate control causing the reference voltage to be affected by temperature
Solution Approach 1:
The patent applies periodic action by using a switching circuit to periodically exchange the connection paths of resistors R1A and R1B. The control circuit switches the connection states at regular intervals, causing the resistors to alternately connect to different nodes. This periodic switching averages out the temperature effects caused by resistance deviations, allowing the reference voltage to remain independent of temperature even when resistor values are not perfectly matched.
2Reliability
If the emitter area of bipolar junction transistor Q2 is made multiple times that of Q1 to create different base-emitter voltages, then the reference voltage can be calculated using the voltage difference, but this requires precise control of transistor geometry ratios
Solution Approach 1:
The patent applies dynamics by introducing time-varying switching operations that dynamically change the circuit configuration. Instead of relying solely on static geometric ratios of transistors, the switching circuit dynamically exchanges connection paths based on control signals. This dynamic approach compensates for manufacturing variations in transistor emitter areas, making the reference voltage more robust against geometric ratio deviations.
3Measurement precision
If resistance deviation is denoted by ε and used to calculate the relationship between reference voltage and temperature, then the temperature effect can be quantified, but the reference voltage remains affected by temperature despite well-regulated resistor parameters
Solution Approach 1:
The patent applies feedback by using the control circuit to monitor and respond to temperature effects. The switching operation is controlled based on detected conditions, creating a feedback mechanism that actively compensates for temperature drift. By periodically exchanging resistor connections in response to temperature variations, the system feedback-corrects the temperature dependence that would otherwise exist due to resistance deviations.
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 effectively minimizes the effect of resistance differences on the reference voltage's temperature correlation, ensuring a stable reference voltage independent of temperature variations.
Implementation Method 1
The forwardly-conducted base-emitter voltage VBE1 has a negative temperature coefficient, that is, a value of dVBE1/dT is negative; and ΔVBE is a positive temperature coefficient, that is, a value of d(ΔVBE)/dT is positive
Data Source
AI summary
A band gap reference voltage generating circuit includes a reference voltage generating circuit, a current generating circuit, a current divider circuit, and a first connection path switching circuit. The reference voltage generating circuit forms a reference voltage on first and second current input terminals thereof. First and second input terminals of the current generating circuit are connected to the first and second current input terminals, respectively. The current generating circuit generates a first current to bias the reference voltage generating circuit. The current divider circuit includes a current input terminal, a first current output terminal, and a second current output terminal. The first connection path switching circuit switches connection paths between the first input terminal and the second input terminal of the current generating circuit, and the first current input terminal and the second current input terminal of the current divider circuit.