Transient-Response LDO Circuit for Overshoot and Undershoot Control
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Solution Overview
Problem
The transient response speed of low dropout regulators (LDOs) in power management chips is insufficient, leading to significant overshoot and undershoot in bias voltages, which adversely affect the performance of radio frequency modules in modern communication systems.
Innovation Solution
A transient-response low dropout regulator is designed with an operational amplifier, feedback module, power transistor, and transient response enhancement circuit, including a unity gain buffer circuit and transient voltage generation circuits, to quickly adjust output voltages and reduce overshoot and undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the LDO uses a conventional regulation structure, then the circuit is simple and stable, but the transient response speed is slow causing large overshoot and undershoot
Solution Approach 1:
The regulation function is segmented into two independent paths: a DC regulation path using the operational amplifier for steady-state accuracy, and a transient response path using the transient response enhancement circuit for fast dynamic response. This segmentation allows each path to be optimized independently, achieving fast transient response without compromising steady-state regulation while managing circuit complexity.
Solution Approach 2:
The transient response enhancement circuit performs preliminary action by detecting load current changes and proactively adjusting the power transistor's gate voltage before the output voltage actually deviates. This predictive adjustment prevents large overshoot and undershoot, improving transient response speed without requiring complex feedback mechanisms.
2Speed
If the LDO increases power transistor drive capability, then transient current response improves, but output voltage fluctuation and oscillation risk increase
Solution Approach 1:
The circuit dynamically switches between different regulation mechanisms: the operational amplifier provides stable DC regulation for steady-state operation, while the transient response enhancement circuit activates during dynamic transitions to provide fast current response. This dynamic allocation of regulation functions achieves both fast transient response and stable output voltage without oscillation.
Solution Approach 2:
The transient response enhancement circuit acts as an intermediary between the load and the power transistor, buffering the direct coupling that causes oscillation. It detects load changes and mediates the control signal to the power transistor, smoothing the transition and preventing voltage fluctuations while maintaining fast response capability.
Data Source
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AI summary
Disclosed in the present invention are a transient-response low dropout regulator, a chip and an electronic device. The low dropout regulator comprises an operational amplifier, a feedback module, a power transistor and a transient response enhancement circuit. The feedback module samples an output voltage. The operational amplifier clamps a feedback voltage output by the feedback module. A unity gain buffer circuit in the transient response enhancement circuit outputs a first voltage in response to the change of a steady-state voltage, while a transient voltage generation circuit in the transient response enhancement circuit generates a second voltage in response to the change of a transient voltage. The second voltage is superposed on the first voltage and then is output to the power transistor, and then the power transistor supplies the stable output voltage to a load.