Quick-Start Low Dropout Regulator for Fast Response
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Solution Overview
Problem
Conventional low dropout regulators suffer from reduced operational rate due to delays caused by low-pass filtering circuits, which affect noise filtering efficiency and require larger circuit areas.
Innovation Solution
A quick-start low dropout regulator design incorporating an error amplifier, an N-type depletion MOSFET, and switches for synchronized switching, along with low-pass filtering components, to rapidly adjust output voltage while minimizing circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filtering circuit is used to filter noises, then noise filtering capability is improved, but operational rate is reduced due to delays
Solution Approach 1:
The patent applies preliminary action by pre-charging the output node capacitor through a dedicated quick-start path before the main low-pass filtering circuit begins operation. This is achieved by using a quick-start transistor that activates first to charge the capacitor, allowing the regulator to respond faster to load changes while the low-pass filter continues to provide noise filtering. The preliminary charging action eliminates the delay that would otherwise occur when the capacitor must charge through the slower filtering path.
2Speed
If additional elements and feedback structures are added to increase operational rate, then operational rate is improved, but circuit area increases
Solution Approach 1:
The patent merges the quick-start function with the existing low-pass filtering circuit by sharing the output node capacitor and using a controlled current source that integrates with the filtering transistor. Instead of adding a completely separate fast-response circuit, the invention combines the quick-start path with the filtering path, allowing both noise filtering and fast response capabilities to coexist in a unified circuit structure that minimizes additional area requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enables rapid charging of the output node, improving operational rate and reducing circuit area, while effectively filtering noises without increasing the number of elements.
Implementation Method 1
an N-type depletion MOSFET, and switches that control the connection to an input voltage source and ground, utilizing a low-pass filtering resistor and capacitor to rapidly charge the output node
Implementation Method 2
a low-pass filtering circuit, which is formed by the low-pass filtering resistor 170 and the low-pass filtering capacitor 180, to filter off the flicker noises within
Data Source
AI summary
A low dropout regulator includes an error amplifier, an N-type depletion MOSFET, a first switch, a second switch, a low-pass filter resistor, and a low-pass filter capacitor. By switching on both the first switch and the second switch, a voltage level of an output node at a negative input terminal of the error amplifier may be rapidly raised to be close to and lower than a voltage level of an input node at a gate of the N-type depletion MOSFET. Both the first switch and the second switch are then switched off immediately so that the voltage level of the output node is gradually raised to be equal to the voltage level of the input node through the low-pass filter resistor.