Transconductance Circuit Feedback for Low-Voltage Precision LED Drive
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional transconductance circuits face challenges in providing precision output currents while minimizing area and power consumption, and they struggle to operate effectively at low supply voltages and drive loads with large inductance, such as light-emitting diodes (LEDs) used for optical vital signs measurement, where noise cancellation is also a concern.
Innovation Solution
The transconductance circuits incorporate an amplifier with a switch coupled between its output and input, and include current cells with transistors and resistors, along with a programmable capacitor for stability and drive capability, allowing for the generation of current pulses and simultaneous monitoring of output current and voltage to cancel noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transconductance circuits are used to provide precision output currents, then output current precision is improved, but area consumption and power consumption increase
Solution Approach 1:
The circuit is divided into functional blocks: an amplifier with feedback switch, multiple current cells with individual switches, and a programmable capacitor. This segmentation allows precise current control through selective activation of current cells while minimizing the active area at any given time.
Solution Approach 2:
The circuit employs dynamic switching of current cells and a programmable capacitor that can be configured based on operating conditions. This dynamic reconfiguration enables the circuit to maintain precision across different operating points while using minimal area for each specific configuration.
2Measurement precision
If conventional transconductance circuits are used to provide precision output currents, then output current precision is improved, but power consumption increases
Solution Approach 1:
Instead of continuously operating all current cells, the circuit activates only the necessary subset of current cells required to achieve the desired output current. This partial action reduces power consumption while maintaining precision by engaging only the minimal necessary circuit elements.
Solution Approach 2:
The circuit changes operating parameters by selectively enabling different combinations of current cells and adjusting the programmable capacitor value. This allows the circuit to optimize the balance between precision and power consumption based on the specific operating requirements.
3Use of energy by stationary object
If conventional transconductance circuits operate at low supply voltages, then power consumption is reduced, but drive capability for large inductance loads deteriorates
Solution Approach 1:
The amplifier incorporates a feedback path with a switch that connects the output to the input. This feedback mechanism enables the amplifier to maintain high gain and drive capability even at low supply voltages, allowing the circuit to effectively drive large inductance loads like LEDs while operating at low power.
Solution Approach 2:
The circuit employs periodic switching of the feedback switch and current cell switches to generate current pulses. This periodic action allows the circuit to build up current through the inductive load over time, achieving effective drive capability for large inductance loads while maintaining low average power consumption.
4Adaptability or versatility
If conventional transconductance circuits drive LED loads, then optical vital signs measurement is enabled, but noise in the output signal increases
Solution Approach 1:
The feedback switch creates a noise-reducing feedback path that allows the amplifier to correct for noise and disturbances in the output current. This feedback mechanism is particularly effective for LED drives, as it maintains precise current control despite the noisy switching required for optical vital signs measurement.
Solution Approach 2:
The circuit converts the potentially harmful noise from switching operations into a manageable signal by using the feedback path to detect and correct noise. The switching action that generates noise also enables the feedback mechanism to identify and compensate for these disturbances, transforming the harmful effect into an opportunity for noise cancellation.
Data Source
AI summary
Disclosed herein are transconductance circuits, as well as related methods and devices. In some embodiments, a transconductance circuit may include an amplifier having a first input coupled to a voltage input of the transconductance circuit, and a switch coupled between an output of the amplifier and a second input of the amplifier.