Voltage Reference Circuit With Sense Contacts for Thermal Bias Stability
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Solution Overview
Problem
Voltage reference circuits face challenges in maintaining a constant output voltage due to variations in contact resistance, which can be critical in safety-critical applications like lithium ion batteries for electric vehicles, where stability over years is required.
Innovation Solution
A voltage reference circuit design utilizing a resistive track with strategically placed force and sense contacts, where resistors are defined by the length of the track rather than contact pads, and a counter-bias voltage mechanism to counteract temperature-dependent voltage biases, ensuring the output voltage is independent of temperature and contact resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact resistance variations are present in the voltage reference circuit, then the output voltage becomes unstable and varies over time, but using traditional resistor configurations with contact pads increases sensitivity to contact resistance changes
Solution Approach 1:
The invention extracts and eliminates the contact pads from the resistor configuration. By defining resistors solely through lengths of resistive track between sense contacts, the design removes the contact resistance interfaces that cause instability, thereby improving output voltage reliability without sacrificing measurement precision
Solution Approach 2:
The invention introduces sense contacts as intermediary elements that measure voltage at specific points along the resistive track without being part of the current-carrying force contacts. This intermediary measurement approach eliminates the harmful effect of contact resistance variations while maintaining accurate voltage reference
2Reliability
If the voltage reference circuit uses traditional resistor configurations, then the circuit structure is simpler, but contact resistance variations cause significant errors in the output voltage
Solution Approach 1:
The invention segments the resistive track into multiple defined sections (first resistor, second resistor, third resistor) with specific functional roles. This segmentation allows precise control over voltage division and counter-bias application, improving output accuracy while the shared resistive track maintains structural efficiency
Solution Approach 2:
The invention applies local quality by assigning different functional characteristics to different sections of the resistive track. The first resistor section handles main voltage division, the second resistor provides counter-bias, and specific sense contacts are positioned at optimized locations to measure and compensate for temperature effects locally
3Reliability
If the voltage reference circuit does not compensate for temperature effects, then the circuit operation is simpler, but the output voltage varies with temperature changes
Solution Approach 1:
The invention applies preliminary anti-action by introducing a counter-bias voltage through the second resistor that preemptively compensates for the temperature-dependent voltage bias of the P-N junction. This counter-action is built into the circuit structure and automatically opposes the harmful thermal effects, improving temperature stability without requiring complex active control
Solution Approach 2:
The invention utilizes parameter changes by exploiting the temperature-dependent characteristics of the P-N junction and the resistive track. By carefully selecting resistor ratios and sense contact positions, the circuit transforms the temperature sensitivity of individual components into a compensated overall response, maintaining stable output across temperature variations
4Length of stationary object
If sense contacts are placed close to force contacts, then the resistive track length is reduced, but contact resistance effects become more significant
Solution Approach 1:
The invention creates equipotential conditions by positioning sense contacts at specific locations where voltage gradients are minimized or where the voltage represents the intended reference value. This equipotential positioning ensures that sense contacts measure the true reference voltage without being significantly affected by contact resistance at the force contacts
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 design significantly reduces errors associated with contact resistance variations, providing a stable and reliable constant voltage reference, essential for long-term reliability in safety-critical systems.
Implementation Method 1
a first component arrangement having a first terminal coupled to the second force contact of the resistive track; a second terminal for coupling to the second supply voltage; and a control terminal coupled to the first sense contact, the control terminal configured to control the flow of current between the first and second terminals of the first component arrangement based on a voltage at the control terminal, wherein the first component arrangement comprises a P-N junction which has a temperature dependent voltage bias
Implementation Method 2
a resistive track having: a first force contact for coupling with a first supply voltage, and a second force contact for coupling to a second supply voltage
Data Source
AI summary
A voltage reference circuit including a resistive track having a first force contact and a second force contact. The first and second force contacts configured to pass a current through the resistive track. A first sense contact, a second sense contact and a third sense contact are arranged at different positions along the resistive track between the first and second force contacts and the sense contacts are arranged to define a first resistor and a second resistor. A first component arrangement includes a P-N junction which has a temperature dependent voltage bias; a second component arrangement. One or both of the first component arrangement and the second component arrangement provide for a counter-bias voltage. The counter bias voltage counters the temperature dependent voltage bias of the P-N junction such that the voltage reference circuit provides a constant output reference voltage.