Bolometer Circuit Power Reduction via Passive Resistive Loads
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Solution Overview
Problem
Conventional bolometer circuits are hindered by increased size, cost, complexity, and noise due to additional transistors or control mechanisms required for bias generation and control, which also reduce sensitivity and usable signal range for infrared radiation detection.
Innovation Solution
A bolometer circuit design featuring a substrate with thermally isolated active bolometers and resistive loads, coupled with an amplifier circuit using an operational amplifier and a variable voltage source to maintain a reference voltage level, generating an output signal indicative of infrared radiation intensity without the need for extensive bias control circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If additional transistors or control mechanisms are used for bias generation and control, then bias control capability is improved, but device complexity increases
Solution Approach 1:
The patent removes transistors and active control mechanisms from the bolometer conduction path, extracting only the essential resistive load elements. This eliminates the need for complex bias control circuitry while maintaining bolometer operation through simple voltage division between the bolometer and resistive load.
Solution Approach 2:
The patent replaces expensive, complex transistor-based control mechanisms with simple, passive resistive loads that require no active control. The resistive loads are basic circuit elements that provide bias control through their resistance value without requiring additional control circuitry.
2Ease of operation
If additional transistors or control mechanisms are used for bias generation and control, then bias control capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes transistor components from the circuit design, reducing the number of expensive semiconductor devices that need to be fabricated and assembled. Only simple resistive loads remain, which are much cheaper to manufacture and integrate.
Solution Approach 2:
The patent substitutes expensive transistor-based control circuitry with inexpensive passive resistive loads. These resistive elements are among the cheapest circuit components to manufacture, significantly reducing overall device cost.
3Ease of operation
If additional transistors or control mechanisms are used for bias generation and control, then bias control capability is improved, but noise increases
Solution Approach 1:
The patent removes transistors from the bolometer conduction path, eliminating the primary noise sources associated with transistor operation. Without transistors switching or amplifying signals in the sensitive measurement path, thermal and electronic noise are significantly reduced.
4Ease of operation
If additional transistors or control mechanisms are used for bias generation and control, then bias control capability is improved, but power consumption increases
Solution Approach 1:
The patent extracts and removes active control components that consume power, leaving only passive resistive elements. Without transistors requiring bias currents or switching power, the overall power consumption of the bolometer circuit is significantly reduced.
Solution Approach 2:
The patent replaces power-consuming active control circuitry with passive resistive loads that require no external power supply or control signals. The resistive loads draw minimal power and operate autonomously based on their resistance values.
5Ease of operation
If additional transistors or control mechanisms are used for bias generation and control, then bias control capability is improved, but sensitivity decreases
Solution Approach 1:
The patent removes transistors from the bolometer conduction path, eliminating the voltage drops and current limitations imposed by transistor operation. This allows the full supply voltage to be applied across the bolometer and resistive load, maximizing the signal swing and sensitivity for detecting infrared radiation changes.
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 reduces complexity, noise, and power consumption while maintaining high sensitivity and expanding the usable signal range for infrared radiation detection, enabling efficient and cost-effective thermal imaging.
Implementation Method 1
an active bolometer configured to receive external infrared (IR) radiation and substantially thermally isolated from the substrate
Implementation Method 2
an amplifier circuit comprising an operational amplifier (op-amp) having a first input coupled to a node in the bolometer conduction path... the amplifier circuit is configured to generate a current flow to the amplifier circuit in response to a resistance change of the active bolometer due to the external IR radiation by maintaining the reference voltage level at the first input of the op-amp
Implementation Method 3
the amplifier circuit is further configured to convert the current flow into an output voltage at an output of the op-amp that is indicative of an intensity of the external IR radiation received at the active bolometer
Data Source
AI summary
A bolometer circuit may include an active bolometer configured to receive external infrared (IR) radiation. The bolometer circuit may be configured to reduce power consumption at high temperatures. In particular, the bolometer circuit may include additional resistors provided in the resistive loads for bolometer conduction paths to limit power at high temperatures. In some embodiments, the bias (e.g., a voltage level) to the gates of transistors in the resistive loads for the bolometer conduction paths may be adjusted based on temperature to limit power and/or current at high temperatures. In bolometer circuits with a feedback resistor provided across an amplifier to configure a feedback amplifier, a circuit with adjustable amplifier power may be provided to save power. In some embodiments, a bolometer circuits may be provided with reduced gains to allow for very hot scenes to be imaged without railing the output.