Switching Regulator Feedback Circuit With Cascode Gain Stability
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Solution Overview
Problem
Existing switching regulators struggle to simultaneously achieve high accuracy of output voltage and favorable frequency characteristics of the feedback loop.
Innovation Solution
A semiconductor circuit device is used in a switching regulator, incorporating a differential amplifier circuit with cascode-connected output-stage transistors, which increases the output impedance and thereby enhances the DC gain of the feedback loop, maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output impedance of the differential amplifier circuit is increased to improve output voltage accuracy, then the DC gain is enhanced, but the frequency characteristics of the feedback loop deteriorate
Solution Approach 1:
The output stage is segmented into two separate transistors (first output-stage transistor and second output-stage transistor) connected in series between the power supply node and output node. This segmentation allows the first transistor to provide high output impedance for accurate voltage sensing while the second transistor maintains frequency response characteristics, resolving the contradiction between measurement precision and reliability.
2Device complexity
If a single output-stage transistor is used in the differential amplifier circuit, then the circuit complexity is reduced, but the DC gain is insufficient to achieve high output voltage accuracy
Solution Approach 1:
The output stage is divided into two transistors connected in series, where the first output-stage transistor contributes to high output impedance and the second output-stage transistor maintains frequency response. This segmentation enables high DC gain for accurate voltage regulation without excessive circuit complexity.
Solution Approach 2:
Each transistor in the series connection performs a specialized function: the first transistor optimizes for output impedance and DC gain, while the second transistor optimizes for frequency characteristics. This local quality differentiation achieves high measurement precision without proportionally increasing overall device complexity.
Data Source
AI summary
A semiconductor circuit device includes a differential amplifier circuit and a switching signal output circuit. The differential amplifier circuit outputs a current based on an output voltage of a switching regulator. The switching signal output circuit outputs a switching signal for a switching device based on a voltage at an output node of the differential amplifier circuit and a voltage corresponding to an inductor current flowing through an inductor. The differential amplifier circuit includes a first output-stage transistor and a second output-stage transistor. The first output-stage transistor is provided between a first power supply node and a first node and outputs the current. The second output-stage transistor is provided between the first node and the output node and has a gate to which a first bias voltage is input.