Pre-Amplified Error Amplifier for Stable Fast Load Transients
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Solution Overview
Problem
Existing error amplifiers in power supplies face a tradeoff between loop stability and load transient response, failing to simultaneously satisfy both performance metrics.
Innovation Solution
An error amplifier design incorporating a pre-amplifier, operational transconductance amplifiers (OTAs), pull-up, and pull-down circuits, which selectively activate based on voltage differences to improve load transient response without compromising stability, using bias voltage and current sources to control the activation of these circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional error amplifier with OTA and compensation network is used, then loop stability is achieved, but load transient response deteriorates due to mutual restriction between stability and transient response
Solution Approach 1:
The error amplifier is segmented into three functional circuits: a steady-state circuit for normal operation, a pull-up circuit for rapid voltage increase, and a pull-down circuit for rapid voltage decrease. This segmentation allows each circuit to be optimized for its specific function, enabling the system to maintain stability during normal operation while achieving fast transient response when load changes occur.
Solution Approach 2:
The error amplifier dynamically switches between different circuits based on operating conditions. The pre-amplifier continuously monitors voltage differences and selectively activates the pull-up or pull-down circuit when voltage thresholds are exceeded, allowing the system to adapt its response characteristics in real-time according to load transient requirements.
2Speed
If pull-up and pull-down circuits are added to improve load transient response, then device complexity increases
Solution Approach 1:
The pull-up circuit and pull-down circuit are merged into a unified error amplifier structure that shares common components such as the pre-amplifier input stage and output connection points. This merging approach reduces overall complexity compared to implementing separate control circuits, while still providing the necessary fast transient response capability through selective activation.
Data Source
AI summary
The present invention provides an error amplifier and a power supply. In the error amplifier, a pre-amplifier takes an amplification action in response to a fluctuation in a feedback voltage, allowing more accurate selective activation of a pull-up circuit, a pull-down circuit or a steady-state circuit. This can reduce accuracy requirements for OTAs therein and hence design requirements for the error amplifier. Moreover, in the event of a loading transition, the pull-up or pull-down circuit can be selectively activated to sooner pull up or down a voltage at an output terminal of the error amplifier. This effectively improves load transient response performance of the loop while not affecting its loop stability.