Low-Noise Voltage Regulator Without Error Amplifier Divider
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Solution Overview
Problem
Conventional voltage regulators exhibit significant noise on their output due to the amplification of noise from the voltage reference and error amplifier, which is unsuitable for applications requiring low power supply noise.
Innovation Solution
The new low-noise voltage regulators regulate the input ports of the error amplifier to ground, eliminate the need for a voltage divider at the error amplifier input, and incorporate a capacitor to reduce output noise, allowing operation without amplifying reference or error amplifier noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage regulators use a voltage divider at the error amplifier input to regulate output voltage, then voltage regulation is achieved, but noise from the voltage reference and error amplifier is amplified and appears on the output
Solution Approach 1:
The patent removes the voltage divider from the error amplifier input circuitry. Instead of using a voltage divider to regulate the error amplifier input voltage, the invention directly regulates the error amplifier input to ground, eliminating the source of noise amplification while maintaining voltage regulation functionality through an alternative control mechanism
Solution Approach 2:
Conventional regulators amplify a fraction of the output voltage to the error amplifier input. This patent inverts the approach by regulating the error amplifier input directly to ground potential, and using the control stage to indirectly regulate the output voltage through the power stage, thereby avoiding noise amplification
2Ease of operation
If a voltage divider is used to set the output voltage, then output voltage control is achieved, but the noise from reference and error amplifier is gained up by the voltage divider
Solution Approach 1:
The voltage divider is completely removed from the error amplifier input circuitry. Output voltage control is achieved through the control stage regulating the power stage, rather than through a voltage divider at the error amplifier input, thereby eliminating noise amplification
Solution Approach 2:
The control stage acts as an intermediary between the error amplifier and the power stage. It receives the error signal and generates appropriate control signals for the power stage switches, enabling output voltage regulation without requiring a voltage divider at the error amplifier input
3Device complexity
If the error amplifier input is not regulated to ground, then circuit simplicity is maintained, but noise from the voltage reference and error amplifier appears amplified on the output
Solution Approach 1:
The patent eliminates the voltage divider from the error amplifier input, simplifying the circuit by removing unnecessary components while simultaneously regulating the error amplifier input to ground to eliminate noise amplification
Solution Approach 2:
The error amplifier continuously monitors the difference between the reference voltage and the actual output voltage (through the power stage), and adjusts the control stage accordingly to maintain proper regulation. This feedback mechanism enables ground regulation of the error amplifier input without adding complexity
Data Source
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AI summary
A low-noise voltage regulator includes (i) an error amplifier configured to generate an error signal that is proportional to a difference between a voltage at a ground node and a voltage at a set node, (ii) a reference resistor electrically coupled between an output power node and the set node, (iii) a capacitor is connected in parallel with the reference resistor, (iv) a reference current source electrically coupled to the set node, and (v) a control and power stage electrically coupled between an input power node and the output power node. The control and power stage is configured to convert an input voltage to an output voltage in response to the error signal to minimize a magnitude of the error signal.