Linear Regulator Noise Isolation for Switched-Mode Power Supplies
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Solution Overview
Problem
Switched-mode power supplies generate noise that can be transmitted to sensitive RF signal transmit/receive circuits, compromising their operation, especially when both types of loads are powered by the same power supply.
Innovation Solution
Incorporating a linear voltage regulator with a transistor controlled by an operational amplifier, where the substrate and gate of the transistor can be connected to different voltage nodes, allowing for isolation of noise and preventing current leakages between power supply nodes, thereby isolating noise from the RF circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a switched-mode power supply is used to power both logic circuits and RF circuits, then power conversion efficiency is improved, but noise is transmitted to the RF circuits compromising their operation
Solution Approach 1:
The power supply system is segmented into two independent paths: one path uses the switched-mode power supply for logic circuits, while the other path uses a separate linear voltage regulator for RF circuits. This segmentation prevents noise from the switched-mode supply from affecting the sensitive RF circuits while maintaining high efficiency for the logic circuits.
Solution Approach 2:
A linear voltage regulator is introduced as an intermediary component between the power source and the RF circuits. This intermediary filters out noise and provides a clean power supply to the RF circuits, while the switched-mode power supply continues to operate independently for other loads.
2Reliability
If the substrate and gate of the transistor are connected to the power supply voltage node, then current leakage is prevented, but noise isolation capability is reduced
Solution Approach 1:
The connections of the transistor substrate and gate are made dynamic rather than fixed. During normal operation, the substrate connects to the switched-mode power supply output for noise isolation, while during shutdown or low-power modes, both substrate and gate connect to the power supply voltage node to prevent current leakage. This dynamic reconfiguration allows the system to optimize for different operational requirements.
Data Source
AI summary
An electronic circuit includes a switched-mode power supply powering a first load via a first linear voltage regulator. The first regulator includes a transistor. The substrate and the gate of the transistor are capable of being coupled to a node of application of a power supply voltage. A method of operating the circuit is also disclosed.