Feed-Forward LDO Circuit for Current Ripple Rejection
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Solution Overview
Problem
Power supplies often suffer from current ripple, which causes fluctuations in the DC voltage output, impacting the performance of downstream electronic components.
Innovation Solution
The implementation of a feed-forward current ripple rejection (FFCRR) circuitry within a low dropout regulator (LDO) that senses the current ripple, modifies it, and injects the modified current to counteract the ripple, thereby stabilizing the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching or rectification processes are used in power supply, then power conversion efficiency is improved, but current ripple is generated causing voltage fluctuations
Solution Approach 1:
The feed-forward ripple rejection circuit proactively detects and processes the ripple current before it reaches the output, using a separate detection path with high-pass filter to identify ripple components and generate compensating signals in advance to counteract the harmful effects
Solution Approach 2:
The patent introduces an intermediary ripple detection circuit that sits between the switching stage and output, using dedicated detection transistors and filter networks to isolate and process ripple signals separately from the main power path, allowing independent ripple compensation without interfering with efficient power conversion
2Reliability
If feed-forward ripple rejection circuitry is added to LDO, then ripple rejection capability is improved, but circuit complexity increases
Solution Approach 1:
The ripple rejection function is segmented into distinct functional blocks: ripple detection stage with detection transistors, high-pass filtering stage, amplification stage, and combination stage with the main LDO circuit. This modular segmentation allows each block to be optimized independently and simplifies the overall design and analysis of the complex circuit
Solution Approach 2:
The patent uses a copy of the ripple signal through the detection transistor network to create a separate control path. The detection circuit creates a replicated version of the ripple current that flows through dedicated filter and amplifier circuits, allowing the original power path to remain simple while the copied signal path handles the complex ripple rejection processing
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 FFCRR circuitry effectively cancels out current ripple, improving the stability and reliability of the power supply output voltage, thus enhancing the performance of connected electronic components.
Implementation Method 1
a low-pass filter having an input and an output, the input of the low-pass filter coupled to the first current terminal of the first transistor
Implementation Method 2
a high-pass filter having an input and an output, the input of the high-pass filter coupled to the first current terminal of the first transistor
Data Source
AI summary
An example apparatus includes: a low-pass filter and a high-pass filter coupled to a first current terminal of the first transistor; an input of a first amplifier coupled to the output of the high-pass filter; an input of a negative gain amplifier coupled to an output of the first amplifier; inputs of an adder coupled to an output of the negative gain amplifier and an output of the low-pass filter; a first input of a second amplifier coupled to the output of the adder; a control terminal of a second transistor coupled to the output of the second amplifier, a second current terminal of the second transistor coupled to the first input of the second amplifier; and a control terminal of a third transistor coupled to the output of the second amplifier, a second current terminal of the third transistor coupled to an output terminal.