Negative Voltage Linear Regulator Controller for Photodiode Noise Mitigation
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Solution Overview
Problem
Conventional circuits using the output of inverting switching regulators as a source of negative voltage for photodiodes suffer from ripple noise, which couples noise to high-gain transimpedance amplifiers, causing detection problems due to direct coupling through the photodiode.
Innovation Solution
A control and drive circuit that includes a regulation control circuit with an error amplifier and a level shifter to convert unregulated negative voltages to positive error and feedback signals, mitigating switching noise by using a negative linear regulator circuit and allowing ground-referred semiconductor implementations, reducing costs and noise coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the output of inverting switching regulators is directly used as the source of negative voltage, then cost is reduced by integration, but ripple noise is generated which couples to photodiode and causes detection problems
Solution Approach 1:
A level shifter circuit is introduced as an intermediary component between the switching regulator output and the error amplifier. This level shifter converts the negative voltage feedback signal to a positive voltage signal, thereby mediating the connection and preventing direct coupling of ripple noise to the high-gain transimpedance amplifier while maintaining the integrated cost-effective design
2Device complexity
If conventional direct coupling is used from switching regulator to photodiode, then circuit complexity is reduced, but noise detection problems occur in high-gain transimpedance amplifier
Solution Approach 1:
The level shifter serves as a mediating circuit that breaks the direct coupling path between the switching regulator and the photodiode/TIA system. By converting the negative voltage signal to positive voltage, it provides electrical isolation that prevents noise propagation while maintaining signal integrity for accurate detection
Solution Approach 2:
The harmful ripple noise component is extracted and isolated from the main signal path through the level shifter configuration. The level shifter extracts only the necessary feedback information while leaving the high-frequency switching ripple behind, effectively separating the useful signal from the harmful noise
Data Source
AI summary
A circuit includes a regulation control circuit. The regulation control circuit includes an error amplifier to generate a control output signal based on an error signal input and a reference input. The regulation control circuit includes a level shifter to receive a negative voltage supplied to a load and to provide a positive error signal to the error signal input of the error amplifier. A driver circuit receives the control output signal from the error amplifier and generates a drive output signal in response to the control output signal. A regulation output circuit regulates the negative voltage supplied to the load in response to the drive output signal from the driver circuit.