Capacitor-Less LDO Regulator With Feed-Forward PSR Control
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Solution Overview
Problem
Conventional capacitor-less Low Drop Out (LDO) Voltage Regulators suffer from inadequate Power Supply Rejection (PSR), line transient response, and load transient response due to the absence of feed-forward and feedback components, necessitating large off-chip capacitors and limiting their performance.
Innovation Solution
The proposed linear LDO Voltage Regulating system incorporates a feed-forward stage with a current summing amplifier and Dynamic Current Bleeder circuit, along with a feedback stage that includes a boost and reduce amplifier circuit, to enhance PSR, line transient response, and load transient response, eliminating the need for external capacitors by using a Compensation capacitor to create a dominant pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional LDOVR architecture is used without feed-forward and feedback components, then device complexity is reduced, but Power Supply Rejection (PSR) performance deteriorates
Solution Approach 1:
The patent introduces a feed-forward path that senses input voltage variations and proactively adjusts the pass transistor gate voltage to compensate for PSR degradation. This feed-forward mechanism works in conjunction with the feedback loop to maintain stable output voltage despite input fluctuations, resolving the contradiction between simplified architecture and PSR performance
Solution Approach 2:
The feed-forward circuit performs preliminary action by detecting input voltage changes before they affect the output and preemptively adjusting the pass transistor control signal. This proactive compensation prevents PSR degradation from occurring in the first place, maintaining reliability without requiring complex additional components
2Volume of moving object
If capacitor-less architecture is used, then device size is reduced, but transient response performance deteriorates
Solution Approach 1:
The enhanced feedback loop with increased gain and bandwidth compensates for the absence of large output capacitors by rapidly detecting and correcting output voltage deviations during transient events. This allows the capacitor-less design to achieve fast transient response comparable to conventional designs with large capacitors
Solution Approach 2:
The feed-forward circuit performs preliminary action by anticipating load transient effects through input voltage sensing and proactively adjusting the pass transistor control signal before significant output voltage deviation occurs, maintaining fast transient response without requiring large external capacitors
3Reliability
If feed-forward and feedback components are added to enhance PSR, then Power Supply Rejection improves, but device complexity increases
Solution Approach 1:
The patent merges the feed-forward and feedback functions into a unified control architecture where both paths work synergistically through shared sensing nodes and coordinated control signals. This integration achieves enhanced PSR while minimizing the additional complexity compared to separate independent circuits
4Volume of moving object
If conventional LDOVR is used without Compensation capacitor, then device size is reduced, but stability deteriorates
Solution Approach 1:
The enhanced feedback loop with increased gain and bandwidth provides sufficient phase margin and stability compensation without requiring a large external Compensation capacitor. The feedback mechanism actively corrects stability issues by rapidly responding to oscillations and voltage deviations, maintaining output stability in the capacitor-less architecture
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
This solution significantly improves PSR and transient responses, reducing the need for external capacitors, enhancing efficiency, and maintaining a stable output voltage under varying load conditions, making it suitable for compact and efficient voltage regulation.
Implementation Method 1
using a Compensation capacitor to create a dominant pole
Data Source
AI summary
A capacitor-less linear Low Drop Out (LDO) Voltage Regulating (VR) system and method with enhanced Power Supply Rejection (PSR), line transient response, and load transient response is disclosed. The system includes a current-summing amplifier to refine input voltage and error signals from an error amplifier circuit, improving regulation accuracy. Further, the system includes a Dynamic Current Bleeder (DCB) circuit to manage current flow, optimizing efficiency. Furthermore, a strategically placed compensation capacitor ensures stable voltage delivery despite load or input changes. To further enhance performance, a boost and reduce amplifier circuit continuously monitors and adjusts current of the error amplifier circuit, minimizing output voltage variations. The system effectively manages applications demanding highly regulated and stable voltage supplies.