Two-Stage LDO Regulator for Overshoot and Undershoot Control
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Solution Overview
Problem
Low dropout (LDO) linear regulators experience instantaneous overshoots and undershoots due to load changes, which can harm the circuit.
Innovation Solution
A low dropout regulator circuit with a power device and two amplification stages, utilizing a feedback resistor network and a feedback capacitor to control the power device at a resistive region, amplifying differential signals to quickly adjust the output voltage in response to load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO regulator is used, then the circuit provides stable DC voltage with low noise, but instantaneous overshoots and undershoots occur due to load changes
Solution Approach 1:
The regulator is divided into two separate amplification stages: a first amplification stage that processes the feedback voltage to generate positive and negative signals, and a second amplification stage that receives a feed forward signal and generates the final amplified signal. This segmentation allows each stage to be optimized for specific functions, improving transient response while maintaining stability.
Solution Approach 2:
A feed forward signal indicative of the output voltage is received by the second amplification stage before the full feedback loop response is complete. This preliminary action allows the regulator to anticipate and compensate for load changes more quickly, reducing overshoot and undershoot while maintaining the stability provided by the feedback mechanism.
2Speed
If the power device operates in a resistive region to quickly respond to load changes, then transient response improves, but control precision may be affected
Solution Approach 1:
A feedback resistor network provides continuous feedback voltage indicative of the output voltage to the first amplification stage. This feedback mechanism maintains control precision by constantly monitoring the output and adjusting the control signals, even while the power device operates in the resistive region for faster transient response.
Solution Approach 2:
The circuit utilizes parameter changes in the amplification stages, where the first amplification stage amplifies the difference between feedback voltage and reference voltage, and the second amplification stage further amplifies the difference involving the feed forward signal. These staged parameter changes allow precise control while maintaining fast response capability.
Data Source
AI summary
A low dropout regulator circuit with reduced overshoot and undershoot during transient state is discussed. The low dropout regulator circuit has a power device operating at a restive region, a first amplification stage and a second amplification stage. The first amplification stage amplifies a difference between a feedback voltage and a reference voltage to generate a positive signal and a negative signal. The feedback voltage is derived from an output voltage via a feedback resistor network. The second amplification stage amplifies a difference between the positive signal and a sum of a feed forward signal and the negative signal to generate an amplified signal. The feed forward signal is derived from an output voltage via a capacitor network.